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COPYRIGHT DEPOSIT 



ONE COPY REC'D 
MAY 23 1898 



A DICTIONARY 



OF 



ELECTRICAL WORDS, 



TERMS AND PHRASES. 



BY 

EDWIN J. HOUSTON, A.M., Ph.D. (Princeton), 

EMERITUS PROFESSOR OF NATURAL PHILOSOPHY AND PHYSICAL GEOGRAPHY IN THE CENTRA! 
HIGH SCHOOL OF PHILADELPHIA ; PROFESSOR OF PHYSICS IN THE FRANKLIN 
INSTITUTE OF PENNSYLVANIA ; ELECTRICIAN OF THE INTER- 
NATIONAL ELECTRICAL EXHIBITION, 
ETC., ETC. 



FOURTH EDITION. WITH APPENDIX. GREATLY ENLARGED. 



NEW YORK: 
THE W. J. JOHNSTON COM PA 



253 BROADA^VAY. 
1 898. 







\T : 



— U5l t 

Mfc CCfY BtCEIVED 



-J 



<o 






8028 



Copyright, 1889, 1892, 1894, 1898 

BY 

The "W. J. Johnston Compaxt 



Appendix B. 
Copyright, 1898 

BY 

Edwin J. Houston 



printed bj 
BraunworttL, Muna « Barbel 

iyn, N.Y., U. S. A. 



Gc2,7o 



PREFACE TO THE FIRST EDITION. 

THE rapid growth of electrical science, and the almost daily addition to it of new 
words, terms and phrases, coined, as they too frequently are, in ignorance of 
t-hose already existing, have led to the production of an electrical vocabulary that is 
already beSvildering in its extent. This multiplicity of words is extremely discourag- 
ing to the student, and acts as a serious obstacle to a general dissemination of elec- 
trical knowledge, for the following reasons : 

i. Because, in general, these new terms are not to be found eve*", in the unabridged 
editions of dictionaries. 

2. The books or magazines, in which they were first proposed, are either inac- 
cessible to the ordinary reader, or, if accessible, are often written in phraseology un- 
intelligible except to the expert. 

3. The same terms are used by different writers in conflicting senses. 

4. The same terms are used with entirely different meanings. 

5. Nearly all the explanations in the technical dictionaries are extremely brief as 
regards the words, terms and phrases of the rapidly growing and comparatively new 
science of electricity. 

In this era of extended newspaper and periodical publication, new words are often 
coined, although others, already in existence, are far better suited to express the same 
ideas. The new terms are used for a while and then abandoned ; or, if retained, 
having been imperfectly defined, their exact meaning is capable of no little ambiguity; 
and, subsequently, they are often unfortunately adopted by different writers with such 
varying shades of meaning, fti&t it is difficult to understand their true and exact 
significance. 

Then again, old terms buried away many decades ago and long since forgotten, are 
dug up and presented in such new garb that their creators would most certainly fail 
to recognize them. 

It has been with a hope of removing these difficulties to some extent that the author 
has ventured to present this Dictionary of Electrical Words, Terms and Phrases to his 
brother electricians and the public generally. 

He trusts that this dictionary will be of use to electricians, not only by showing the 
wonderful extent and richness of the vocabulary of the science, but also by giving the 
general consensus of opinion as to the significance of its different words, terms or 
phrases. It is, however, to the general public, to whom it is not only a matter of 
interest but also one of necessity to fully understand the e^act meaning of electrical 
literature, that the author believes the book will be of the greatest value. 

In order to leave no doubt concerning the precise meaning of the words, terms and 
phrases thus defined, the following plan has been adopted of giving : 

(1.) A concise definition of the word, term or phrase. 

(2.) A brief statement of the principles of the science involved in the definition. 



(3 ) Where possible and advisable, a cut of the apparatus described or employed 
in connection with the word, term or phrase denned. 

It will be noticed that the second item of the plan makes the Dictionary ap- 
proach to some extent the nature of an Encyclopedia. It differs, however, from 
an Encyclopedia in its scope, as well as in the fact that its definitions in all cases 
are concise. 

Considerable labor has been expended in the collection of the vocabulary, for 
which purpose electrical literature generally has been explored. In the alphabetical 
arrangement of the terms and phrases defin -d, much perplexity has arisen as to the 
proper catch-word under which to place them. It is believed that part of the 
difficulty in this respect has been avoided by the free use of cross references. 

In elucidating the exact meaning of terms by a brief statement of the principles 
of the science involved therein, the author has freely referred to standard textbooks on 
electricity, and to periodical literature generally. He is especially indebted to works 
or treatises by the following authors, viz. : S. P. Thompson, Larden, Cumming, 
Hering, Prescott, Ayrton, Ayron and Perry, Pope, Lockwood, Sir William Thom- 
son, Fleming, Martin and Wetzler, Preece, Preece and Sivewright, Forbes, Max- 
well, De Watteville, J. T. Sprague, Culley, Mascart and Joubert, Schwendler, 
Fontaine, Noad, Smee, Depretz, De la Rive, Harris, Franklin, Cavallo, Grove,. 
Hare, Daniell, Faraday and very many others. 

The author ofL-rs his Dictionary to his fellow electricians as a starting point only. 
He does not doubt that his book will be found to contain many inaccuracies, ambig- 
uous statements, and possibly doubtful definitions. Pioneer work of this character 
must, almost of necessity, be marked by incompleteness. He, therefore, invites 
the friendly criticisms of electricians generally, as to errors of omission and commis- 
sion, hoping in this way to be able finally to crystallize a complete vocabulary of 
electrical words, terms and phrases. 

The author desires in conclusion to acknowledge his indebtedness to his friends, 
Mr. Carl Henng, Mr. Joseph Wetzler and Mr. T. C. Martin, for critical exami- 
nation of the proof sheets ; to Dr. G. G. Faught for examination of the proofs of 
the parts relating to the medical applications of electricity, and to Mr. C. E. Stump 
for valuable aid in the illustration of the book ; also to Mr. George D. Fowle, 
Engineer of Signals of the Pennsylvania Railroad Company, for information concern- 
ing their System of Block Signaling, and to many others. 

EDWIN J. HOUSTON. 
Central High School, Philadelphia, Pa., 
September, 1889. 



PREFACE TO THE SECOND EDITION. 

THE first edition of the "Dictionary of Electrical Words, Terms and Phrases" met 
with so favorable a reception that the entire issue was soon exhausted. ' 
Although but a comparatively short time has elapsed since its publication, electrical 
progress has been so marked, and so many new words, terms and phrases have been 
introduced into the electrical nomenclature, that the preparation of a new edition has 
been determined on rather than a mere reprint from the old plates. 

The wonderful growth of electrical science may be judged from the fact that the 
present work contains more than double the matter and about twice the number of 
definitions that appeared in the earlier work. Although some of this increase has 
been due to words which should have been in the first edition, yet in greater part it 
has resulted from an actual multiplication of the words used in electrical literature. 

To a certain extent this increase has been warranted either by new applications of 
electricity or by the discovery of new principles of the science. In some cases, how- 
ever, new words, terms or phrases have been introduced notwithstanding the fact that 
other words, terms or phrases were already in general use to express the same ideas. 

The character of the work is necessarily encyclopedic. The definitions are given 
in the most concise language. In order, however, to render these definitions intel- 
ligible, considerable explanatory matter has been added. 

The Dictionary has been practically rewritten, and is now, in reality, a new book 
based on the general lines of the old book, but considerably changed as to order of 
arrangement and, to some extent, as to method of treatment. 

As expressed in its preface, the author appreciates the fact that the earlier book 
was tentative and incomplete. Though the wide scope of the second edition, the 
vast number of details included therein, and the continued growth of the electrical 
vocabulary must also necessarily make this edition incomplete, yet the author ventures 
to hope that it is less incomplete than the first edition. He again asks kindly criti- 
cisms to aid him in making any subsequent edition more nearly what a dictionary of 
so important a science should be. 

The order of arrangement in the first edition has been considerably changed. The 
initial letter under which the term or phrase is defined is in all cases that of the noun. 

For example, "Electric Light " is defined under the term " Light, Electric " ; 

"Diameter of Commutation" under "Commutation, Diameter of ," "Alter- 
nating Current Dynamo-Electric Machine" under "Machine, Dynamo-Electric, 
Alternating Current ." As before, the book has numerous cross references. 

Although the arrangement of the words, terms and phrases under the initial letter 
of the first word, term or phrase, as, for example, " Electric Light" under the letter E, 
might possess some advantages, yet, in the opinion of the author, the educational value 



VI 

of the work would be thereby considerably decreased, since to a great extent such an. 
arrangement would bring together incongruous portions of the science. 

Frequent cross references render it possible to use the Dictionary as a text-book in 
connection with lectures in colleges and universities. With such a book the student need 
make notes only of the words, terms or phrases used, and afterwards, by the use of the 
definitions and explanatory matter connected therewith, work up the general subject 
matter of the lecture. The author has successfully used this method in his teaching. 

In order to separate the definitions from the descriptive matter, two sizes of type 
have been used, the definitions being placed in the larger sized type. 

In the descriptive matter the author has not hesitated to quote freely from standard 
electrical works, electrical magazines, and periodical literature generally. Among the 
numerous works consulted, besides those to which reference has already been made 
in the preface to the first edition, he desires to acknowledge his indebtedness espe- 
cially to "The Alternating Current Transformer," by J. A. Fleming ; to various works 
of John W. Urquhart ; to "Modern Views of Electricity," by Prof. O. J. Lodge; to 
"A Text-bojk of Human Physiology," by Landois & Sterling; and to "Practical 
Application of Electricity in Medicine and Surgery," by Liebig & Rohe. 

The cuts or diagrams used in the book have either been drawn especially for the 
work or have been taken from standard electrical publications. 

The chart of standard electrical symbols and diagrams has been taken from Prof. 
F. B. Crocker's paper on that subject. 

The definition of terms used in systems of electric railways have been taken 
mainly from a paper on " Standards in Electric Railway Practice," by O. T. Crosby. 

The author desires especially to express his obligations to Prof. F. B. Crocker of 
the E ectrical Engineering Department, Columbia College, New York, and to Carl 
Hering. of Philadelphia, for critical examination of the entire manuscript and for many 
valuable suggestions ; also to The Electrical World and the Electrical Engineer of New 
York, and to Prof. Elihu Thomson, Edward Caldwell, T. C. Martin, Dr. Louis Bell, 
Joseph Wetzler, Nikola Tesla, Wm. H. Wahl, Prof. Wm. D. Marks, Prof. A. E. 
Dolbear, C. W. Pike, John Hoskin, and numerous others, for aid in connection with 
new words or phrases. So far as thev relate to the medical applications of electricity, 
the proof sheets were revised by Dr. G. G. Faught, of Philadelphia. 

The author desires to thank critics of the first edition and the electricil fraternity in 
general for valuable suggestions. He presents this second edition of his Dictionary in the 
hope that it may to some extent properly represent the vocabulary of electrical science. 

Central High School, EDWIN J. HOUSTON. 

Philadelphia, May, 1S92. 



PREFACE TO THE THIRD EDITION. 

THE second edition of the "Dictionary of Electrical Words, Terms, and Phrases" 
was exhausted in such a comparatively short time that the publishers believed 
that what new matter might be required for a third edition could best be added in 
the form of an appendix. 

Although not quite two years have elapsed since the issue of the second edition, 
yet the growth of electrical science has continued at so rapid a pace, and new words, 
terms, and phrases have of necessity been introduced so rapidly, that fully twenty per 
cent., both of new words and new matter, have been found necessary for the third 
edition. Had this fact been known in time, it might have been better to have 
developed the additional matter throughout the text, rather than placing it at the end 
of the book as an appendix. 

Should a demand be made for a fourth edition, the author contemplates re- 
writing and re-arranging the entire volume. He is thoroughly aware of the inaccuracies 
and incompleteness of many of the definitions in the second edition, and hopes, in 
the event of a demand for a fourth edition, to produce a volume more nearly ap- 
proximating to what an electrical dictionary should be. In the meantime, he again 
asks the kindly criticisms of his fellow laborers in the electrical field to aid him in the 
work. 

In order to facilitate the use of the cross-references, all words, terms, and phrases 
referred to in the appendix are so marked; i e., (See Appendix — Insulation, Kilo- 
metric, of Cable.} All references not so marked will be found in the main text of the 
dictionary. 

The author desires to express his obligations to numerous authors and technical 
journals for information as to new words, terms, and phrases, and to the significance 
generally given to them in actual use. He desires especially to acknowledge his 
obligations to his colleague, Mr. A. E. Kennelly, and to Professors R. A. Fessenden, 
C. Wellman Park; to Messrs. C. P. Steinmetz, J. F. Kelly, O. B. Shallenberger, Carl 
Hering, H. W. Frye, W. D. Weaver, W. F. C. Hasson, Townsend Wolcott, J. B. 
Cahoon, and many others, for reading of proof sheets and suggestions. 

The author presents this third edition of the Dictionary with the hope that it 
may prove of value to the electrical fraternity. 

EDWIN J. HOUSTON. 

Philadelphia, May, 1894. 



** . 






PREFACE TO THE FOURTH EDITION. 

IN preparing the fourth edition of his " Dictionary of Electrical 
Words, Terms and Phrases," the author soon found that the 
recent marvellous growth in the electrical vocabulary was such that 
it would be impossible to add, in the shape of a separate appendix, 
the new words, terms and phrases only, that it was necessary to 
introduce into the book. This will be evident from the fact that 
the added words exceed in number those already contained in the 
first, second and third editions. Since it was deemed inadvisable 
by the publisher to recast the entire book, the only course left open 
to the author was to alphabetically arrange all the old and new 
words, and to present them in concise definitions without any ency- 
clopaedic matter, referring the reader to the matter contained in 
the earlier editions for illustration and detail. 

It has also been thought advisable to introduce a change in the 
manner of arrangement, the words, terms and phrases being alpha- 
betically arranged according, either to the word, or to the first word 
of the term or phrase. This has permitted the entire suppression 
of all cross references, which, in view of the author's past expe- 
rience, he believes will prove an advantage. 

The author desires to acknowledge the very valuable assistance 
afforded him by his colleague, Dr. A. E. Kennelly, in the prepa- 
ration of the matter for the fourth edition, both in collecting new 
terms, as well as in preparing the definitions, and reading the 
proof. 

The author trusts, that the fourth edition of his electrical Diction- 
ary will prove of benefit not only to the electrical world but to the 
reading public generally. 

All criticisms will be gladly received. 

Edwin J. Houston. 

Philadelphia, December, 1897. 



A. DICTIONARY 



OF 



ELECTRICAL 

WORDS, TERMS AND PHRASES 



A. or An. — An abbreviation sometimes used 
in medical electricity for anode. (See Anode.) 

A. C. C. — An abbreviation used in medical 
electricity for Anodic Closure Contraction. 
(See Contraction, Anodic Closure) 

A. D. C. — An abbreviation used in medical 
electricity for Anodic Duration Contraction. 
(See Contraction, Anodic Duration) 

A. 0. C. — An abbreviation used in medical 
electricity for Anodic Opening Contraction. 
(See Contraction, Anodic Opening.) 

Abscissa of Kectilinear Co-ordinates. — A 
line or distance cut off along axis of abscissas. 

The abscissa of the point D, Fig. I, on the curve 
O D R, is the distance D I, or its equal A 2, 
measured or cut off on the line A C, the axis of 
abscissas; or, briefly, A 2, is the abscissa of the 
point D. 

Abscissas, Axis of — One of the 

axes of co-ordinates used for determining the 
position of points on a curved line. 

Thus the position of p 
the point D, Fig. 1, on 
the curved line O D R, 
is determined by the per- 
pendicular distances, D I 
and D 2, of such point 
from two straight lines, 
A B and A C, called the 
axes of co-ordinates. AC, 
is called the axis of ab- Fi ^ T ' Axes 0/ Co-ordinates, 
scissas, and AB, the axis of ordinates. The point 




A, where the lines are considered as starting or 
originating, is called the point of origin, or, gen- 
erally, the origin. 

The use of co-ordinates was first introduced by 
the famous mathematician, Dcs Cartes. 

Absolute. — Complete in itself. 

The terms absolute and relative are used in 
electricity in the same sense as ordinarily. 

Thus, a galvanometer is said to be calibrated 
absolutely when the exact current strengths re- 
quired to produce given deflections are known ; 
or, in other words, when the absolute current 
strengths are known ; it is said to be calibrated 
relatively when only the relative current strengths 
required to produce given deflections are known. 

The word absolute, as applied to the units em- 
ployed in electrical measurements, was introduced 
by Gauss to indicate the fact that the values of 
such units are independent both of the size of the 
instrument employed and of the value of gravity at 
the particular place where the instrument is 
used. 

The word absolute is also used with reference 
to the fact that the values of the units could 
readily be redetermined from well known con- 
stants, in case of the loss of the standards. 

The absolute units of length, mass, and time 
are more properly called the C. G. S. units, or 
the centimetre-gramme. second units. (See Units, 
Absolute.) 

An absolute system of units based on the tnilli- 
gramme, millifnetre, and second, was proposed by 
Weber, and was called the millimetre milli- 
gramme-second units. It has been replaced by 



Abs.] 



[Ace. 



the C. G. S. units. (See Units, Centimetre- 
Gramme- Second. Units, Fundamental.) 

Absolute Block System for Railroads. — 

(See Block System for Railroads, Absolute?) 

Absolute Calibration. — (See Calibration, 
Absolute?) 

Absolute Electrometer. — (See Electrome- 
ter, Absolute?) 

Absolute Galvanometer. — (See Galva- 
nometer, Absolute?) 

Absolute Unit of Current. — (See Current, 
Absolute Unit of.) 

Absolute Unit of Electromotive Force. — 
(See Force, Electro?notive, Absolute Unit 
of) 

Absolute Unit of Inductance. — (See In- 
ductance, Absolute Unit of.) 

Absolute Unit of Resistance. — (See Re- 
sistance, Absolute Unit of) 

Absolute Unit of Self-induction.— (See 
Induction, Self, Absolute Unit of) 

Absolute Units. — (See Units, Absolute?) 

Absolute Vacuum. — (See Vacuum, Ab- 
solute?) 

Absorption. — The taking, or, literally, 
drinking in, of one form of matter by another, 
such as a gas, vapor or liquid by a solid ; or 
of the energy of sound, light, heat, or elec- 
tricity by ordinary matter. 

Absorption, Acoustic The taking 

in of the energy of sound waves produced by 
one sounding or vibrating body by another 
vibrating body. 

Acoustic absorption may result in the dissipa- 
tion of the absorbed energy, as heat, or in sym- 
pathetic vibrations. {See. Vibrations, Sympathetic.) 

Absorption, Electric The appar- 
ent soaking of an electric charge into the 
glass or other solid dielectric of a Leyden jar 
or condenser. (See Condenser.) 

The capacity of a condenser varies with the 
time the condenser remains charged and with the 
time taken in charging. Some of the charge 
acts as if it soaked into the solid dielectric, and 
this is the cause of the residual charge. (See 
Charge, Residual.) Therefore, when the con- 



denser is discharged, less electricity appears than 
was passed' in ; hence the term electric absorption. 

Absorption, Luminous The ab- 
sorption of the energy of light in its passage 
through bodies. 

When sunlight falls on an opaque colored body, 
such for example as a red body, all the colors but 
the reds are absorbed. The reds are then thrown 
off and thus cause the color. In the same manner, 
when sunlight falls on a transparent colored body, 
such for example as red, all colors but the reds are 
absorbed, and the reds are transmitted. 

When sunlight falls on a phosphorescent body, 
a part of the light is absorbed as heat ; another 
part is absorbed by the molecules being set into 
motion sufficiently rapid to cause them to emit 
light or to become luminous. 

A mass of glowing gas or vapor absorbs waves 
of light of the same length as those it itself emits. 
This is the cause of the dark lines of the solar 
spectrum, called the Fraunhoffer lines. 

The amount of light absorbed by the glass globe 
of an incandescent lamp, according to Urquhart, 
is as follows, viz.: 

Clear glass 10 per cent. 

Ground glass 35 " 

Opalescent glass 50 " 

Absorption, Selective The absorp- 
tion of a particular or selected character of 
waves of sound, light, heat, or electricity. 

Absorption, Thermal — The ab- 
sorption of heat energy in its passage through 
a body. 

The phenomena of thermal absorption are 
similar to those of luminous absorption. A sub- 
stance that is transparent to heat, or which allows 
heat waves to pass through without absorption, 
is called diathermanous, or diather??tanic i or 
is said to be transparent to heat. 

Absorptive Power. — (See Power, Absorp- 
tive?) 

Acceleration. — The rate of change of 
velocity. 

Acceleration is thus distinguished from velocity: 
velocity expresses in time the rate-of-change of 
position, as a velocity of three metres per second; 
acceleration expresses in time the rate-of-change 
of velocity, as an acceleration of one centimetre 
per second. 

Since all matter is inert, and cannot change its 



Ace] 



[Ace. 



condition of rest or motion without the applica- 
tion of some force, acceleration is necessarily due 
to some force outside the matter its If. A force 
may therefore be measured by the acceleration it 
imparts to a given mass of matter. 

Acceleration is positive when the velocity is in- 
creasing, and negative when it is decreasing. 

Acceleration, Dimensions of The 

value of the acceleration expressed in terms 
of the length or of distance by the time. (See 
Acceleration, Unit of.) 

Acceleration, Unit of — That ac- 
celeration which will give to a body unit- 
velocity in unit-time ; as, for example, one 
centimetre-per-second in one second. 

Bodies falling freely in a vacuum, and ap- 
proximately so in air, acquire an acceleration 
which in Paris or London, at the end of a second, 
amounts to about 981 centimetres per second, or 
nearly 32.2 ft. per second. 

V 
A = — , or, in other words, 

The acceleration equals the velocity divided by 
the time. 

But, since velocity equals the Distance, or the 

Length traversed in a Unit of Time, V = — . 



Therefore, A = — = — = ^ o , or 



The acceleration equals the length, or the dis- 
tance passed through, divided by the square of the 
time in seconds. 

These formulae represent the Dimensions of 
Acceleration. 

Accumulated Electricity. — (See Electri- 
city, Accumulated?) 

Accumulating Electricity. — (See Electri- 
city, Accumulating?) 

Accumulation of Electricity. — (See Elec- 
tricity, Accumulation of.) 

Accumulator. — A word sometimes applied 
to any apparatus in which the strength of a 
current is increased by the motion past it of a 
conductor, the currents produced in which 
tend to strengthen and increase the current 
which causes the induction. 



The word accumulator is sometimes applied to 
Sir Wm. Thomson's Electric Current Accumu- 
lator. 

Current accumulators operate on the reaction 
principle of dynamo-electric machines. In this 
sense, therefore, a dynamo-electric machine is an 
accumulator. (See Machine, Dynamo- Electric, 
Reaction Principle of.) 




Fig. 2. Barlow's Wheel. 

The copper disc D, Fig. 2, has freedom of 
rotation, on a horizontal axis at O, in a magnetic 
field, the lines of force of which, represented by 
the dotted lines in the drawing, pass downward 
perpendicularly into the plane of the paper. 

If, now, a current from any source be passed 
in the direction A, O, B, C, A, through the circuit 
A, O, B, C, A, which is provided with spring 
contacts at O, and A, the disc will rotate in the 
direction of the curved arrow. This motion is 
due to the current acting on that part of the disc 
which lies between the two contacts — A and O. 
This apparatus is known as Barlow" s Wheel. 

If, when no current is passing through the 
circuit, the disc be turned in the direction of the 
arrow, a current is set up in such a direction as 
would oppose the rotation of the disc. (See 
Law, Lenz's.) 

If, however, the disc be turned in the opposite 
direction to that of the arrow, induction currents 
will as before be produced in the circuit. As 
this rotation of the disc tends to move the circuit 
O A, towards the parallel but oppositely directed 
circuit B C, these two circuits being parallel and 
in opposite directions tend to repel one another, 
and there will thus be set up induced currents 
that tend to oppose the motion of rotation, and 
the current of the circuit will therefore increase 
in strength. (See Dynamics, Electro.) Should 
then a current be started in the circuit, and the 
original field be removed, the induction will be 
continued, and a current which, up to a certain 
extent, increases or accumulates, is maintained in 
the circuit during rotation of the disc. (Larden.) 

Barlow's Wheel, when used in this manner, is 
known as Thomson's Electric Current Accumu- 
lator. 



Ace] 



[Ace. 



Accumulator. — A word often applied to 
a Leyden jar or condenser, which permits the 
gradual collection from an electric source of 
a greater charge than it would otherwise be 
capable of containing. 

A condenser. (See Condenser.) 

The ability of a source to accumulate an in- 
creased charge when connected to a condenser is 
due to the increased capacity which a plate or 
other conductor acquires when placed near 
another plate or conductor. (See Condenser. 
Jar, Leyden.) 

Accumulator, Capacity of The 

capacity of a condenser, expressed in micro- 
farads. (See Conde?iser, Capacity of.) 

Accumulator or Condenser ; Laws of Ac- 
cumulation of Electricity. — Sir W. Snow 
Harris, by the use of his Unit-Jar and Elec- 
tric Thermometer, deduced the following 
laws for the accumulation of electricity, which 
we quote from Noad's " Student's Text-Book 
of Electricity," revised by Preece : 

(i.) "Equal quantities of electricity are given 
off at each revolution oi the plate of an electrical 
machine to an uncharged surface, or to a surface 
charged to any degree of saturation. " 

( 2. ) "A coated surface receives equal quantities 
of electricity in equal times ; and the number of 
revolutions of the plate is a fair measure of the 
relative quantities of electricity, all other things 
remaining the same." 

(3.) " The free action of an electrical accumula- 
tion is estimated by the interval it can break 
through, and is directly proportional to the quan- 
tity of electricity." 

(4.) " The free action is inversely proportional 
to the surface." 

(5.) " When the electricity and the surface are 
increased in the same ratio, the discharging in- 
terval remains the same ; but if, as the electricity 
is increased, the surface is diminished, the dis- 
charging interval is directly as the square of the 
quantity of electricity." 

(6.) "The resistance of air to discharge is as 
the square of the density directly." 

According to some later investigations, the 
quantity a plane surface can receive under a given 
density depends on the linear boundary of the 
surtace as well as on the area of the surface. 

" The amount of electrical charge depends on 



surface and linear extension conjointly. There 
exists in every plane suriace what may be termed 
an electrical boundary, having an important rela- 
tion to the grouping or disposition of the electric 
particles in regard to each other and to surrounding 
matter. This boundary in circles or globes is 
represented by their circumferences. In plane 
rectangular surfaces, it is by their linear extension 
or perimeter. If this boundary be constant, their 
electrical charge varies with the square root of 
the surface. If the surface be constant the charge 
varies with the square root of the boundary. If 
the surface and boundary both vary, the charge 
varies with the square root of the surface multi- 
plied into the square root of the boundary " 

These laws apply especially to continuous sur- 
faces taken as a whole, and not to surfaces divided 
into separate parts. 

By electrical charge Harris meant the quantity 
sustained on a given surface under a given elec- 
trometer indication ; by electrical intensity, he 
meant the indication of the electrometer corre- 
sponding to a given quantity on a given surface. 

(See Condenser, Capacity of. Capacity, Elec- 
trostatic. Capacity, Specific Inductive. ) 

Accumulators of this character are now 
generally called Condensers. (For more modern 
principles concerning their construction and 
capacity see Condenser. Condenser, Capacity of.) 

Accumulator, Secondary or Storage 
Cell Two inert plates partially sur- 
rounded by a fluid incapable of acting chem- 
ically on either of them until after the passage 
of an electric current, when they become 
capable of furnishing an independent electric 
current. 

This use of the term accumulator is the one 
most commonly employed. A better term for 
such a cell is a secondary or storage cell. (See 
Cell, Secondary or Storage.) 

Commercially, an accumulator consists of a 
single jar and its electrolyte, in which a single 
set of positive and negative plates is properly 
placed. 

Accumulator, Water-Dropping 

An apparatus devised by Sir W. Thomson for 
increasing the difference of potential between 
two electric charges. 

The tube X Y, Fig. 3, connects with a reser- 
voir of water which is maintained at the zero 
potential of the earth. The water escapes from 



Ach.] 



[Act 



B' 




the openings at C and D, in small drops and falls 
on funnels provided, as shown, to receive the 
separate drops and again discharge them. 

The vessels A, A', and B, 
B', which are electrically X 

connected as shown, are 
maintained at a certain small A frj 
d.fference of potential, as 
indicated by the respective 
-f- and — signs. 

Under these circum- 
stances, therefore, C and D, 
will be charged inductively &£• 3- Water-Drop- 
with charges opposite to ^ Accumulator. 
those of A and B, or with — and -j- electricities 
respectively. As the drops of water fall on the 
funnels, the charges which the funnels thus con- 
stantly receive are given up to B' and A', before 
the water escapes. Since, therefore, B, B', and 
A, A', are receiving constant charges, the differ- 
ence of potential between them must continually 
increase. This apparatus operates on the same 
principle as the replenisher. The drops of water 
act as the carriers, and A, A', and B, B', as the 
hollow vessels. (See Replenisher.') 

Achromatic. — Free from false coloration. 

Images formed by ordinary lenses do not pos- 
sess the true colors of the object, unless the edges 
of the lenses are cut off by the use of a diaphragm; 
i e.. an opaque plate with a central circular 
opening. The edges of the lenses disperse the 
light like an ordinary prism, and so produce rain- 
bow colored (prismatic) fringes in the image. 
1'he use of an achromatic lens is to obviate this 
false coloration. 

Achromatizable. — Capable of being freed 
from false coloration. 

Achromatize. — To free from false color- 
ation. 

Achromatizing. — Freeing from false color- 
ation. 

Acid, Spent A battery acid, or other 

acid, that has become too weak for efficient 
action. 

In a voltaic cell the acid of the electrolyte 
becomes spent by combining with the metal of 
the positive plate. 

Acidometer. — A special form of hydrom- 
eter used in determining the specific gravity 
of the acid liquid in a secondary or storage 



cell. (See Areo7neter or Hydro?neter. Cell, 
Storage) 

The scale on the acidometer tube is made to in- 
dicate the density according to the distance the 
floating instrument sinks in the liquid. 

Aclinic Line. — (See Line, Aclinic) 

Acoustic Absorption. — (See Absorption, 
Acoustic) 

Acoustic Engraving. — (See Engraving, 
Acoustic) 

Acoustic Telegraphy. — (See Telegraphy, 
Acoustic) 

Acoustic Tetanus. — (See Tetanus, Acous- 
tic) 

Acoutemeter, Electric An ap- 
paratus for electrically testing the delicacy of 
hearing. 

The Acoutemeter is one of the many applica- 
tions of Hughes' sonometer. It consists of three 
flat coils placed parallel to one another on a grad- 
uated rod, passing through their axes. The 
central coil, which is used as the primary of an 
induction coil, is fixed. The other two, which are 
employed as secondary coils, are movable. (See 
Sonometer, Hughes' 1 . Coil, Induction. Micro- 
phone.) A microphone, electrical tuning fork, 
switches, plugs, and other accessories, are suitably 
placed and connected. The subject whose hear- 
ing is to be tested is placed with his back to the 
apparatus, and with two telephone receivers tightly 
fixed to his ears. As various sounds are produced, 
the outer or movable coils are moved gradually 
away from the central coil, until no sound is 
heard in the telephone receivers. This distance 
is in the inverse ratio of the delicacy of hearing of 
the individual. 

Actinic Photometer. — (See Photometer, 
Actinic) 

Actinic Ray. — (See Ray, Actinic) 

Actinism. — The chemical effects of light, 
as manifested by the decomposition of various 
substances. 

Under the influence of the sun's light, the car- 
bonic acid absorbed by the leaves of plants is de- 
composed in the living leaves into carbon, which is 
retained by the plant for the formation of its 
woody fibre or ligneous tissue, and oxygen, which 
is thrown off. 



Act.] 



[Act, 



The bleaching of curtains, carpets, and other 
fabrics exposed to sunlight is caused by the actinic 
power of the light. The photographic picture is 
impressed by the actinic power of light on a plate 
covered with some sensitive metallic salt. 

Actinograph. — An apparatus for measur- 
ing and recording the intensity of the chemi- 
cal effects of light. 

Actinography. — The method of measuring 
and recording the intensity of the chemical 
effects of light. 

Actiiiometer. — A word sometimes applied 
to a pyrheliometer. (See Pyrheliometer^) 

Actiiiometer, Electric An appa- 
ratus for electrically measuring the intensity 
of the chemically active rays present in any 
luminous radiation. 

The rays from the luminous source are per- 
mitted to fall on a selenium resistance, and their 
intensity determined by the change observed in 
the resistance as indicated by the deflections of a 
galvanometer placed in circuit with the selenium 
resistance. Or, a thermo-electric pile is employed, 
and the amount of heat present determined by the 
indications of a galvanometer placed in its 
circuit. 

Action, Cataphoric The action 

of electric osmose or cataphoresis. (See 
Catafthoresis.) 

Action Currents. — (See Curre?its, Action.) 

Action, Inductive, Lines of — 

Lines within the space, separating a charge 
and a neighboring body, along which elec- 
trostatic inductive action takes place. 

Lines of electrostatic force. 

Lines of inductive action pass through the 
dielectric, separating the two bodies, and termi- 
nate on the surfaces of the conductor. According 
to the now generally received notions, the elec- 
trostatic charge exists in the mass of the dielectric, 
and not in that of the conductor. The lines of 
inductive action terminate against the surfaces, 
one at the positive, and the other at the negative 
surface. A true E. M. F. exists in the space 
traversed by lines of inductive action. A con- 
ductor brought into this space becomes electri- 
fied, or is strained in such a manner that a 
momentary current is produced by the rearrange- 



ment of the electrification brought about by 
electrostatic induction. 

Action, Local, of Dynamo-Electric Ma- 
chine The loss of energy in a dy- 
namo-electric machine by the setting up of 
eddy currents in its pole pieces, cores, or 
other conducting masses. (See Curre?its, 
Eddy.) 

In a dynamo-electric machine local action is 
obviated by a lamination of the pole pieces, arma- 
ture core, etc. (See Core, Lamination of.) 

Action, Local, of Toltaic Cell 

An irregular dissolving or consumption of the 
zinc or positive element of a voltaic battery, by 
the fluid or electrolyte, when the circuit is 
open or broken, as well as when closed, or in 
regular action. 

Local action is due to small particles of such 
impurities as carbon, iron, arsenic, or other 
negative elements, in the positive plate. These 
impurities form with the positive element minute 
voltaic couples, and thus direct the corro^ve 
action of the liquid to portions of the plate near 
them. Local action causes a waste of energy. 
It may be avoided by the amalgamation of the 
zinc. (S-*e Zinc, A?naigamation of.) 

Action, Magne-Crystallic A term 

proposed by Faraday to express differences 
in the action of magnetism on crystalline 
bodies in different directions. 

A needle of tourmaline, if hung with its axis 
horizontal, is no longer paramagnetic, as usual, 
but diamagnetic. The same is true of a crystal 
of bismuth. Faraday concluded from these ex- 
periments that a force existed distinct from either 
the paramagnetic or the diamagnetic force. He 
called this the viagne cry stallic force. 

Plucker infers from these phenomena that a 
definite relation exists between the ultimate form 
of the particles of matter and their magnetic be- 
havior. The subject may be regarded as yet 
somewhat obscure. (See Polarity, Diamagnetic.) 

Action of a Current on a Magnetic Pole. 

— (See Current, Action of, on a Magnetic- 
Pole.) 
Action, Refreshing, of Current 

The restoration, after fatigue, of muscular and 
nervous excitability obtained by the action of 



Act.] 



9 



[Aer. 



voltaic alternatives. (See Alternatives, Vol- 
taic^) 

Activity. — The work done per second by 
any agent. (This term is but seldom used.) 

Work-per-second, or, as generally termed 
in the United States, Power, or Rate of 
Doing Work. (See Power.) 

Activity, Unit of A rate of work- 
ing that will perform one unit of work per 
second. 

In C. G. S. units, the activity of one erg per 
second. 

The C. G. S. unit of activity is very small. 
One Watt, the practical unit of activity or power, 
is equal to ten million ergs per second. (See 
Watt.) 

The unit of activity generally used for mechan- 
ical power is the horse-power, or 746 watts. 
(See Horse-Power.) 

Actual Cautery. — (See Cautery, Actual?) 
Acute Angle. — (See Angle, Acute?) 
Adapter. — A screw nozzle fitted to an elec- 
tric lamp, provided with a screw thread to en- 
able it to be readily placed on a gas bracket 
or chandelier in place of an ordinary gas 
burner. 

Adherence. — The quality or property of 
adhering. (See Adhesion?) 

Adherence, Magnetic Adhesion be- 
tween surfaces due to magnetic attraction. 

Magnetic adhesion has been applied, among 
other things, to a brake action on car wheels, 
either by causing them to adhere directly to the 
track or to a brake-block. 

Adhesion. — The mutual attraction which 
exists between unlike molecules. (See At- 
traction, Molecular?) 

The phenomena of adhesion are due to the 
mutual attraction of dissimilar molecules. 

Adhesion, Electric Adhesion be- 
tween surfaces due to the attraction of unlike 
electrostatic charges. 

Molecular adhesion must be distinguished from 
the attraction which causes a piece of dry and 
warmed writing paper, that has been rubbed by a 
piece of india-rubber, to stick to a papered wall. 
In this latter case the attraction between the wall 



and the paper is due to the mutual attraction of 
two dissimilar electrostatic charges. Molecular 
adhesion must also be distinguished from the at- 
traction of opposite magnetic poles. 

Adhesion, Galvanoplastic The ad- 
hesion of a galvanoplastic deposit or coating 
to surfaces subjected to electroplating. (See 
Plating, Electro?) 

Adiathermancy. — Opacity to heat. 

A sub.-tance is said to be diathermanous when 
it is transparent to heat. Clear, colorless crys- 
tals of rock salt are very transparent both to light 
and to heat. Rock salt, covered with a layer or 
deposit of lampblack or soot, is quite transparent 
to heat. An adiathermanous body is one which 
is opaque to heat. 

Heat transparency varies not only with differ- 
ent substances, but also with the nature of the 
source from which the heat is derived. Thus, a 
substance may be opaque to he it from a non- 
luminous source, such as a vessel filled with boil- 
ing water, while it is comparatively transparent 
to heat from a luminous source, such as an incan- 
descent solid or a voltaic arc. 

A similar difference exists as regards transpar- 
ency to light. A colorless glass will allow light 
of any color to pass through it. A blue glass will 
allow blue light to pass freely through it, but will 
completely prevent the passage of any red light; 
and so with other colors. 

Adiathermaiiic. — Possessing the quality of 
adiathermancy. (See Adiathermancy?) 

Adjustable Condenser. — (See Condenser, 
Adjustable.) 

Adjuster, Cord A device for ad- 
justing the length of a pendant cord. 

Adjustment. — Such a regulation of any 
apparatus as will enable it to properly perform 
its functions. 

JEpinus' Condenser. — (See Condenser, 
JEpinus' ?) 

Aerial Cable.— (See Cable, Aerial?) 

Aerial Cable, Suspending Wire of 

(See Wire, Suspending, of Aerial Cable?) 

Aerial Line.— (See Line, Aerial?) 

Aerolites. — A name sometimes given to 
meteorites. 

Meteorites are masses of solids which pass 



Aff.] 



10 



[Ago. 



through the upper portions only of the earth's 
atmosphere on their approach to the orbit of the 
earth, or which fall through the air on the earth's 
surface from the sky. They are luminous at 
night and are followed by a train of fire. The 
luminosity is due to heat produced by friction 
through the air. Meteors frequently burst from 
the sudden expansion of their outer portions. 

Some meteorites are composed of nearly pure 
iron alloyed with nickel. The majority of them, 
however, are merely stones or oxidized sub- 
stances. Their average velocity is about 26 miles 
a second. 

Affinity, Chemical Atomic attrac- 
tion. 

The force which causes atoms to unite and 
form chemical molecules. 

Atomic or chemical attraction generally results 
in a lobs of the characteristic qualities or proper- 
ties which distinguish one kind of matter from 
another. In this respect chemical affinity differs 
from adhesion, or the force which holds unlike 
molecules together. (See Adhesion. Attraction, 
Molecular.) If, for example, sulphur is mixed 
with lampblack, no matter how intimate the 
mixture, the separate particles, when examined 
by a magnifying glass, exhibit their peculiar color, 
lustre, etc. If, however, the sulphur is chemi- 
cally united with the carbon, a colorless, transpar- 
ent, mobile liquid, called carbon bisulphide, re- 
sults, that possesses a disagreeable, penetrating 
odor. 

Chemical affinity, or atomic combination, is in- 
fluenced by a variety of causes, viz. : 

(1.) Cohesion. Cohesion, by binding the mole- 
cules more firmly together, opposes their mutual 
atomic attraction. 

A solid rod of iron will not readily burn in the 
flame of an ordinary lamp; but, if the cohesion be 
overcome by reducing the iron rod to filings, it 
burns with brilliant scintillations when dropped 
into the same flame. In this case the increase of 
surface and the increased temperature of the 
smaller particles al-o contribute to the result. 

(2.) Solution. Solution, by giving the molecules 
greater freedom of motion, favors their chemical 
combination. 

(3.) Heat. Heat sometimes favors atomic com- 
bination possibly by decreasing the cohesion, and, 
possibly, by altering the electrical relations of the 
atoms. If too great, heat may produce decom- 
position. There is for most substances a critical 



temperature below which chemical combination 
will not take place. (See Thermolysis.) 

(4.) Light. Decomposition, or the lessening of 
chemical affinity, through the agency of light, is 
called Actinism. Light also causes the direct 
combination of substances. A mixture of equal 
volumes of hydrogen and chlorine unites explo- 
sively when exposed to the action of full sunlight. 
(See Actinism.) 

(5.) Electricity. An electric spark will cause 
an explosive combination of a mixture of oxygen 
and hydrogen. Electricity also produces chemi- 
cal decomposition. (See Electrolysis.) 

Helmholtz accounts for the electro-chemical 
attraction of oxygen for zinc by supposing that all 
substances possess a definite amount of attraction 
for electricity, and that the attraction of zinc in 
this respect exceeds that of copper and the other 
metals. He thus regards the zinc as attracting 
its electric charge rather than as attracting the 
oxygen. Since both zinc and copper are dyad 
metals, this view, as will be seen, is at variance 
with later views. 

Chemical affinity may be caused by the opposite 
attractions of electrical charges naturally possessed 
by the atoms of matter. This would appear to be 
rendered probable by the law of electro-chemical 
equivalence. (See Equivalence, Electro-Che?nical, 
Law of. Electricity, Atom of.) 

After Currents. — (See Currents, After?) 

Aging- of Alcohol, Electric (See 

Alcohol, Electric Aging of.) 

Agonal. — Pertaining to the agone. (See 
Agone.) 

Agone. — A line connecting places on the 
earth's surface where the magnetic needle 
points to the true geographical north. 

The line of no declination or variation of 
a magnetic needle. (See Needle, Magnetic, 
Decimation of.) 

As all the places on the earth where the mag- 
netic needle points to the true north may be ar- 
ranged on a few lines, it will be understood that 
the pointing of the magnetic needle to the true 
geographical north is the exception and not the 
rule. In many places, however, the deviation 
from the true geograpical north is so small that 
the direction of the needle may be regarded as 
approximately due north. 

Agonic. — Pertaining to the agone. 



Air.] 



11 



[Ala. 



Air-Blast for Commutators. — An inven- 
tion of Prof. Elihu Thomson to prevent the 
injurious action of destructive flashing at the 
commutator of a dynamo-electric machine. 

A thin, forcible blast of air is delivered through 
suitable tubes at points on the three-part commu- 
tator cylinder of the Thomson-Houston dynamo, 
where the collecting brushes bear on its surface. 
The effect is to blow out the arc or prevent its for- 
mation and thus avoid its destructive action on 
the commutator segments. The use of the air- 
blast also permits the free application of oil, thus 
further avoiding wear. 
B 9 




Fig. 4. Air-Blast on Commuta 

The blast-nozzles are shown at B 3 , B 3 , Fig. 4, 
near the collecting brushes. 

The air-supply is obtained from a blower at- 
tached directly to the shaft of the machine. Its 
construction and operation will be readily under- 
stood from an inspection of Fig. 5, in which the 




Fig-. J. The Thomson Blower* 

top is removed for ready examination of the 
interior parts. 

Air Churning-. — (See Churning, Air?) 

Air Condenser. — (See Co7tde?iser, Air?) 

Air Field.— (See Field, Air.) 

Air-Gap.— (See Gap, Air.) 

Air-Liue Wire. — (See Wire, Air-Line?) 

Air Magnetic Circuit. — (See Circuit, Air 
Magnetic?) 

Air-Pump. — (See Pump, Air?) 

Air-Pump, Oeissler's Mercurial 

(See Pump, Air, Geissler's Mercurial?) 



Air-Pump, Mechanical (See Pump, 

Air, Mechanical?) 

Air-Pump, 3Iercurial (See Pump, 

Air, Mercurial?) ■ 

Air-Pump, Spreugel's Mercurial 

(See Pump, Air, SprengeVs Mercurial?) 

Air-Space Cut-Out. — (See Cut-Out, Air- 
space.) 

Alarm, Burglar A device, generally 

electric, for automatically announcing the 
opening of a door, window, closet, drawer, or 
safe, or the passage of a person through a 
hallway, or on a stairway. 

Electric burglar-alarm devices generally consist 
of mechanism for the operation of an automatic 
make-and-break bell on the opening or closing of 
an electric circuit. The bell may either continue 
ringing only while the contact remains closed, or, 
may, by the throwing on of a local circuit or 
battery, continue ringing until stopped by some 
non-automatic device, such as a hand-switch. 

The alarm-bell is stationed either in the house 
when occupied, or on the outside when the house 
is temporarily vacated, or may connect directly 
with the nearest police station. 

Burglar-alarm apparatus is of a variety of 
forms. Generally, devices are provided by means 
of which, in case of house protection, an annunci- 
ator shows the exact part where an entrance has 
been attempted. (See Amiunciator, Burglar- 
Alarm.) Switches are provided for disconnecting 
all or parts of the house from the alarm when so 
desired, as well as to per- 
mit windows to be partly 
raised for purposes of ven- 
tilation without sounding 
the alarm. A clock is fre- 
quently connected with the 
alarm for the purpose of 
automatically disconnect- 
ing any portion of the 
house at or for certain in- 
tervals of time. 

Fig. 6 shows a burglar- 
alarm with annunciator, 
switches, switch-key, cut-off, and clock. 

Alarm, Burglar, Central-Station 

A burglar-alarm, the contact points of which 
are placed in the places to be protected, and 




Fig. 6. Burglar- Alarm 
Annunciator. 



Ala. 



12 



[Ala. 



connected by suitable circuits with alarms 
placed in a centrally located station. 

In a system of central-station burglar-alarms, a 
number of houses, factories, banks, etc., are all 
connected telegraphically with the nearest police 
station, or other central station, constantly pro- 
vided with police officers. A series of contacts are 
placed on doors, windows, safes and money draw- 
ers, and connected with alarms and annunciators 
placed in the central station. An unauthorized 
entrance, therefore, is automatically telegraphed 
to the central station and its exact location indi- 
cated on the annunciator. Systems of central- 
station fire-alarms are constructed on a similar 
plan. 

Alarm, Electric An automatic de- 
vice by which attention is called to the occur- 
rence of certain events, such as the opening 
of a door or window; the stepping of a person 
on a mat or staircase; the rise or fall of tem- 
perature beyond a given predetermined point; 
or, a device intended to call a person to a tel- 
egraphic or telephonic instrument. 

Electric-alarms are operated by means of the 
ringing of an electro-magnetic or mechanical bell, 




Fig. 7. Electrically Started Mechanical Alarm. 

which is electrically called into action by either 
closing or opening an electric circuit, generally 
the former. 

Electric -alarms may be divided into two classes, 
viz.: 

(1.) Mechanically operated alarms, or those in 



which the alarm is given by clock-work, started 
by means of an electric current. 

(2.) Those in which the alarm is both set in ac- 
tion and operated by an electric current. 

In Fig. 7 is shown the general construction of 
an electrically started mechanical alarm. The 
attraction of the armature B, by the electro-mag- 
net A, moves the armature lever pivoted at C, 
and thus releases the catch e, and permits the 
spring or weight connected with the clock move- 
ment to set it in motion and strike the bell. 

Electrically actuated alarm-bells are generally 
of the automatic make-and-break form. The 
striking lever is operated by the attraction of the 
armature of an electro-magnet, and is provided 
with a contact-point, so placed that when the 
hammer is drawn away from the bell, by the ac- 
tion of a spring, on the electro-magnet losing its 
magnetism, a contact is made, but when the ham- 
mer is drawn towards the bell the contact is open- 
ed. When, therefore, the hammer strikes the 
bell, the circuit is opened, and the electro-magnet 
releases its armature, permitting a spring to again 
close the contact by moving the striking lever 
away from the bell. Once set into action, these 
movements are repeated while there is battery 
power sufficient to energize the magnet. 

In Fig. 8, in which is shown an electrically ac- 
tuated alarm-bell, the battery terminals are con- 

T 




Fig: S. Automatic Make-and- Break. 

-ected with the right and left hand binding-posts, 
P and M. The hammer, K, is connected with a 
striking lever, which forms part of the circuit, 
and which is attached to the armature of the elec- 
tro-magnet e. A metallic spring, g, bears against 
the armature when the latter is away irom the 
magnet, but does not touch the armature when 
it is moved towards the magnet. A small spring 
draws the lever away from the magnet when no 
current is passing. The movements of the arma- 



Aln 



13 



[Ale. 



lure thus automatically open and close the circuit 
of the electro-magnet. 

This form of make-and-break is called &n auto- 
matic make-and-break. 

Alarm, Electrically Operated An 

alarm that is maintained in operation by the 
electric current. (See Alarm, Electric?) 
Alarm, Electro-Mechanical — A 

mechanically operated alarm that is started 
or set in operation by means of an electric 
current. (See Alarm, Electric?) 

Alarm, Fire, Automatic An in- 
strument for automatically telegraphing an 
alarm from any locality on its increase in tem- 
perature beyond a certain predetermined point. 

Fire-alarms are operated by thermostats, or by 
means of mercurial contacts; i. e., a contact 
closed by the expansion of a column of mercury. 
(See Thermostat. Contact, Mercurial.) 

In systems of fire-alarm telegraphs, the alarm 
is automatically sounded in a central police sta- 
tion and in the district fire-engine house. (See 
Telegraphy, Fire- Alarm. ) 

Alarm, Mercurial Temperature 

An instrument for automatically telegraphing 
an alarm by means of a mercurial contact on 
a predetermined change of temperature. 

The action of mercurial contacts is dependent 
on the fact that, as the mercury expands more 
than glass by the action of heat, the mercury level 
reaches a contact-point placed in a glass tube and 
thus completes the circuit through its own mass, 
which forms the other or movable contact. 
Sometimes both contacts are placed on opposite 
sides of a tube and are closed when the mercury 
reaches them. 

Mercurial temperature or thermostat alarms 
are employed in hot-houses, incubators, tanks 
and buildings for the purpose of maintaining a 
uniform temperature. 

Alarm, Telegraphic An alarm-bell 

for calling the attention of an operator to 
a telegraphic instrument when the latter is of 
the non-acoustic or needle type. 

In acoustic systems of telegraphy the sounds 
themselves are generally sufficient. 

Alarm, Telephonic An alarm-bell 

for calling a correspondent to the receiving 
telephone. 



These alarms generally consist of magneto- 
electric bells. (See Bell, Magneto-Electric .) 

Alarm, Temperature An electric 

alarm automatically operated on a change of 
temperature. (See Alarm, Fire, Automatic?) 

Alarm, Thermostat An electric 

alarm that is thrown into action by a thermo- 
stat. (See Thermostat?) 

Alarm, Water or Liquid Level 

A device for electrically sounding an alarm 
when a water surface varies materially from 
a given level. 

An electric bell is placed in a circuit that is au- 
tomatically closed or broken by the movement of 
contact-points operated by the change of liquid 
level. 

A form of electric alarm for a water-level is 
shown in Fig. 9. The float is provided with 
contacts for closing an electric circuit, when it 
either rings a bell, or, by its action on some form 
of automatic cut-off, stops the water. 




^ i ,ff , ,.v: , ;. , :.,v.: » 

Fig. Q. Water-Level Alarm 




Fig. 10. 



When arranged with a double float, as shown 
in Fig. 10, the alarm may be made to signal 
either a too high or a too low water level. 

Alarm, Yale-Lock-Switch Burglar 

— An apparatus whereby the opening of a 
door by an authorized party provided with the 
regular key will not sound an alarm, but any 
other opening will sound such alarm. 




Fig. 11. Yale -Lock -Switch. 
A Yale -lock burglar-alarm switch is shown in 
Fig. 11. 

Alcohol, Electric Aging of A pro- 
cess for the rapid aging of alcohol, by ex^ 



Ale. 



14 



[All. 



posing it to the action of electrically produced 
ozone. 

Instead of the ordinary process of aging alco- 
hol, by exposing it in partially closed vessels to 
the action of air, it is exposed to the action of 
ozone, electrically produced. 

The ozone employed is obtained in substan- 
tially the usual way by the passage of a rapid 
succession of electric sparks through air. 

Alcohol, Electric Rectification of 

A process whereby the bad taste and odor of 
alcohol, due to the presence of aldehydes, 
are removed by the electrical conversion of 
the aldehydes into true alcohols through the 
addition of hydrogen atoms. 

An electric current sent through the liquid 
between zinc electrodes liberates oxygen and hy- 
drogen irom the decomposition of the water. 
The nascent or atomic hydrogen converts the 
aldehydes into alcohol and deprives the pro- 
ducts of their fusel oil, while the oxygen forms 
insoluble zinc oxide. 

Algebraic Co-efficient. — (See Co-efficient, 
Algebraic?) 

Algebraic Notation. — (See Notation, Al- 
gebraic?) 

All-Night Arc Lamp.— (See Lamp, Ail- 
Night Arc.) 

All-Night Electric Lamp. — (See Lamp, 
All-Night Arc.) 

Allotropic— Pertaining to allotropy. (See 
Allotropy.) 

Allotropic State.— (See State, Allotropic). 

Allotropy.— A variation of the physical 
properties of an elementary substance with- 
out change of composition of its molecules. — 
(See State, Allotropic) 

Alloy. — A combination, or mixture, of two 
or more metallic substances. 

Alloys in most cases appear to be true chemi- 
cal compounds. In a few instances, however, 
they may form simple mixtures. 

The composition of a few important alloys is 
here given: 

Solder, plumber's; Tin 66 parts, Lead 34 parts. 

Pewter, hard; Tin 92 parts, Lead 8 parts. 

Britannia metal; Tin 100 parts, Antimony 8 
parts, Copper 4 parts, Bismuth, I part. 



Type metal; Lead 80, Antimony 20 parts. 
Brass, white; Copper 65, Zinc 35 parts. 
Brass, red; Copper 90, Zinc 10 parts. 
Speculum metal; Copper 67, Tin 33 parts. 
Bell metal; Copper 78, Tin 22 parts. 
Aluminium bronze; Copper 90, Aluminium 10 
parts. 

Alloy. — To form a combination or mixture 
of two or more metallic substances. 

Alloy, German Silver — An alloy 

employed for the wires of resistance coils, 
consisting of 50 parts of copper, 25 of zinc, 
and 25 of nickel. 

German silver wire is suitable for resistance 
coils, because its resistance varies but slightly with 
changes of temperature. It is cheaper than plati- 
num- silver alloy, and is therefore employed ex- 
tensively. Platinum silver alloy, however, has 
more resistance for a given size of wire, and its re- 
sistance varies somewhat less than German silver 
with changes of temperature, and is therefore used 
where greater accuracy is desired. 

Alloy, Palladium An alloy of pal- 
ladium with other metals. 

Palladium forms a number of useful alloys with 
various metals. Some of the palladium alloys are 
as elastic as steel, are unaffected by moisture or 
ordinary corrosive agencies, and are entirely de- 
void of paramagnetic properties; that is to say, 
they cannot be magnetized after the manner of 
iron. 

These properties have been utilized by their 
discoverer, Paillard, in their employment for the 
hair-springs, escapements and balance wheels of 
watches, in order to permit the watches to be car- 
ried into strong magnetic fields without any ap- 
preciable effects on the rate of the watch. A 
number of careful tests made by the author, by 
long continued exposure of watches, thus pro- 
tected by the Paillard alloys, in extraordinary 
fields, show that the protection thus given the 
watches enables them to be carried into the strong- 
est possible magnetic fields without appreciably 
affecting their rate. 

The Paillard palladium alloys have the follow- 
ing composition, viz.: 

Alloy No. j. 

Palladium 60 to 75 parts. 

Copper 15 to 25 " 

Iron 1 to 5 " 



All.] 

Alloy No. 2. 

Palladium 50 to 75 parts. 

Copper 20 to 30 " 

Iron 5 to 20 " 

Alloy No. 3. 

Palladium ' 65 to 75 " 

Copper ' 15 to 25 " 

Nickel. 1 to 5 " 

Gold 1 to 2§ " 

Platinum i to 2 " 

Silver 3 to 10 " 

Steel 1 to 5 " 

Alloy No. 4. 

Palladium 45 to 50 " 

Silver 20 to 25 " 

Copper 15 to 25 " 

Gold 2 to 5 " 

Platinum 2 to 5 " 

Nickel 2 to 5 " 

Steel 2 to 5 " 

The great value of the palladium alloys, when 
employed for the hair-springs of watches, arises 
not only from their non-magnetizable properties, 
and their inoxidizability, but particularly from the 
fact that their elasticity is approximately the same 
for comparatively wide ranges of temperature. 

Alloy, Platinum-Silver An alloy 

consisting of one part of platinum, and two 
parts of silver. 

Platinum -silver alloy is now extensively em- 
ployed for resistance coils from the fact that 
changes in temperature of the alloy produce but 
comparatively small changes in its electrical re- 
sistance. (See Alloy, German Silver.) 

Alphabet, Telegraphic —An arbi- 
trary code consisting of dots and dashes, 
sounds,deflections of a magnetic needle, flashes 
of light, or movements of levers, following one 
another in a given predetermined order, to 
represent the letters of the alphabet and the 
numerals. 

Alphabet, Telegraphic : International 

Code The code of signals for letters, 

etc., employed in England and on the Euro- 
pean continent generally. 

Similar symbols are employed for the numerals 
and the punctuation marks. 

Ic will be observed that it is mainly in the 



15 [Alp. 

characters of the American Morse, in which spaces 
are used, that the Continental characters differ 
from the American. This is due to the use of the 
needle instrument, with which a space cannot well 
be represented. A movement or deflection of the 





Single 




Single 


Printing 


Needle 


Printing 


.Needle 


a . — 


./ 


r> _. 


/x 


b _..* 


/ vw 





/// 


c — . 


/,/. 


p . 


.//, 


d _.. 


/v> 


q 


//./ 


e . 


\ 


r ,_^. 


v/> 


f .. % 


wA 


s ... 


S\N 


g 


// X 


t _ 


/ 


h ..... 


t WW 


u 


vv/ 


» — 


NS 


V 


\w/ 


.9 


./// 


w , 


,// 


k 


A/ 


X .. 


/ VXA 


1 . „ 


v/\* 


y 


A// 


m 


// 


z .. 


//vx 



International Telegraphic Code. 

needle to the left signifies a dot; a movement to 
the right, a dash. 

Alphabet, Telegraphic : Morse's 

Various groupings of dots and dashes, or 
deflections of a magnetic needle to the right 
and left, which represent the letters of the 
alphabet or other signs. 

In the Morse alphabet dots and dashes are em- 
ployed in recording systems, and sounds of 
varying intervals, corresponding to the dots and 
dashes, in the sounder system. 

A dash is equal in length of time to three dots. 
The space between the separate characters of a 
single letter is equal to one dot, except in the 
American Morse, in which the following letters 
contain longer spaces: C, O, R, Y, and Z. The 
lengthened spaces are equal to two dots. L is 
one and a half times the length of T. 

The sound produced by the down stroke of the 
sounding lever in the Morse sounder is readily 
distinguishable from the up stroke. When these 
differences are taken in connection with the inter- 
vals between successive sounds there is no diffi- 
culty in reading by sound. 

(For methods of receiving the alphabet, see 
Sounder, Morse Telegraphic. Recorder, Morse. 
Recorder, Bain's Chemical. Recorder, Siphon. 
Relay. Magnet, Receiving.) In the needle tele- 
graph, the code is similar to that used in the Morse 
Alphabet. (See Telegraphy, Single-A r eedle.) 



Alt.] 16 

American Morse Code. 
Alphabet. 

a n 

b o - - 

c -- - p 

d— - q 

e - r - -- 

f s --- 

h u 

i - - v — 

j w 

k x 

1 y 

m z - - - • 

& - --- 

Numerals. 

i 6 

2 7 

4 9 

Punctuation Marks. 

Period Interrogation — 

Comma Exclamation 

Printing Sing-le Needle 

1 V //// 

2 u/// 

3 \ \ N // 

4 , — \ \ \ \ / 

5 __ \\\\\ 

6 / \ \ \ \ 

7 //vnx 

8 ///xx 

9 ////X 

10 ///// 

Period www 

Comma \ / \ / \ / 

Interrogation \\ / / \\ 

Exclamation //w, / 

Colon // /\s\ 

Semicolon /\/\/\ 

Alteration Theory of Muscle or Nerve 

Current.— (See Theory, Alteration, of 
Muscle or Nerve Current?) 

Alternating Arc— (See Arc, Alternat- 
ing.) 

Alternating Current Circuit. — (See Cir- 
cuit, Alternating Current.) 



[Alt. 

Alternating* Current Condenser. — (See 
Condenser, Alternati?ig Current?) 

Alternating Current Dynamo-Electric 
Machine. — (See Machine, Dynamo-Electric, 
Alternating Current.) 

Alternating* Current Electric Motor. — 

(See Motor, Electric, Alternating Current.} 

Alternating Currents. — (See Currents, 
Alternating?) 

Alternating Currents, Distribution of 
Electricity by (See Electricity, Dis- 
tribution of, by Alternating Currents.) 

Alternating Discharge. — (See Discharge, 
Alternating?) 

Alternating Dynamo-Electric Machine. — 
(See Machine, Dynamo-Electric , Alternat- 
ing Current?) 

Alternating Electrostatic Field. — (See 
Field, Alternating Electrostatic?) 

Alternating Electrostatic Potential. — 
(See Potential, Alternating Electrostatic?) 

Alternating Field. — (See Field, Alternat- 
ing?) 

Alternating Influence Machiue, TViins- 

hnrst's (See Machine, Wimshurst's 

Alternating Influence.) 

Alternating* Magnetic Field. — (See Field y 
Alternating Magnetic?) 

Alternating Magnetic Potential. — (See 
Potential, Alternating Magnetic?) 

Alternating Potential. — (See Potential, 
Alternating?) 

Alternating Primary Currents.— (See 
Currents, Alternating Primary?) 

Alternating Secondary Currents.— (See 
Currents, Alternating Secondary.) 

Alternation.— A change in direction or 
phase. 

Alternations. — Changes in the direction of 
a current in a circuit. 

A current that changes its direction 300 times 
per second is said to possess 300 alternations per 
second. 

Alternations, Complete A change 

in the direction of a current in a circuit from its 



Alt.] 



17 



[Aram. 



former direction and back again to that 
direction. A complete to-and-fro change. 

Complete alternations are sometimes indicated 
by the symbol ~. 

Alternations, Frequency of — A 

phrase employed to denote the number of al- 
ternations per second. 

Alternative Path.— (See Path, Alterna- 
tive?) 

Alternatives, Voltaic A term used 

in medical electricity to indicate sudden re- 
versals in the polarity of the electrodes of a 
voltaic battery. 

An alternating current from a voltaic bat- 
tery, obtained by the use of a suitable com- 
mutator. 

Sudden reversals of polarity produce more 
energetic effects of muscular contraction than do 
simple closures or completions of the circuit. 

The muscular contraction produced by a voltaic 
current is much stronger when the direction of the 
current is rapidly reversed by means of a com- 
mutator than when the current is more slowiy 
broken and the poles then reversed. 

The effect of voltaic alternatives is to produce 
quick contractions that are in strong contrast to 
the prolonged contractions that result from the 
faradic current. In the faradic machine, the 
reversals are so rapid that the muscle fails to 
return to rest before it is again contracted. 

Voltaic alternatives are sometimes indicated by 
the contraction V. A. 

Alternator. — A name commonly given to 
an alternate current dynamo. (See Machine, 
Dynamo-Electric , Alterjidting Current?) 

Alternator, Compensated Excitation of 

An excitation of an alternating current 

dynamo-electric machine, in which the field is 
but partially excited by separate excitement, 
the remainder of its exciting current being 
derived from the commuted currents of a 
small transformer placed in the main circuit 
of the machine. 

The object of compensated excitation of an 
alternator is to render the machine self-governing. 

Amalgam. — A combination or mixture 
of a metal with mercury. 
Amalgam, Electric —A substance 



with which the rubbers of the ordinary fric- 
tional electric machines are covered. 

Electric amalgams are of various compositions. 
The following formula produces an excellent 
amalgam : 

Melt together five parts of zinc and three of 
tin, and gradually pour the molten metal into 
nine parts of mercury. Shake the mixture until 
cold, and reduce to a powder in a warm mortar. 
Apply to the cushion by means of a thin layer of 
stiff grease. 

Mosaic gold, or bisulphide of tin, and powdered 
graphite, both act as good electric amalgams. 

An electric amalgam not only acts as a con- 
ductor to carry off the negative electricity, but, 
being highly negative to the glass, produces a far 
higher electrification than would mere leather or 
chamois. 

Amalgamate. — To form into an amalgam. 

Amalgamating". — Forming into an amal- 
gam. ^ 

Amalgamation. — The act of forming into 
an amalgam, or effecting the combination of 
a metal with mercury. 

Amalgamation of Zinc Plates of Voltaic 
Cell. — (See Plates, Zinc, of Voltaic Cell, 
Amalgamation of) 

Amber. — A resinous substance, generally 
of a transparent, yellow color. 

Amber is interesting electrically as being be- 
lieved to be the substance in which the proper- 
ties of electric attractions and repulsions, imparted 
by friction or rubbing, were first noticed. It was 
called by the Greeks r/\.SKrpov, from which the 
word electricity is derived. This property was 
mentioned by the Greek, Thales of Miletus, 600 
b. c, as well as by Theophrastus. 

American System of Telegraphy.— (See 

Telegraphy, American System of.) 

American Twist-Joint. — (See Joint, 
American Twist) 

American Wire Gauge. — (See Gauge, 
Wire, American) 

Ammeter. — A form of galvanometer in 
which the value of the current is measured 
directly in amperes. (See Galvanometer.) 

An ampere-meter or ammeter is a commercial 
form of galvanometer in which the deflections of 



Anim.J 



18 



[Amp. 



a magnetic needle are calibrated or valued in am- 
peres. As a rule the coils of wire in an ammeter 
are of lower resistance than in a voltmeter. The 
magnetic needle is deflected from its zero position 
by the field produced by the current whose strength 
in amperes is to be measured. This needle is held 
in the zero position by the action of a magnetic 
field, either of a permanent or an electro-magnet, 
by the action of a spring, or by a weight under the 
influence of gravity. There thus exist a variety 
of ammeters, viz.: permanent -magnet ammeters, 
electro-magnetic ammeters, spring ammeters and 
gravity ammeters. 

In the form originally devised by Ayrton and 
Perry, the needle came to rest almost imme- 
diately, or was dead-beat in action. (See Damp- 
ing.) It moved through the field of a permanent 
magnet. The instrument was furnished with a 
number of coils of insulated wire, which could 
be connected either in series or in mu/tip/e-arc by 
means of a commutator, thus permitting the scale 
reading to be verified or calibrated by the use of a 
single voltaic cell. (See Circuits, Varieties of. 
Commutator. Calibration, Absolute. Calibra- 
tion, Relative.) In this case the coils were 
turned to series, and a plug pulled out, thus intro- 
ducing a resistance of one ohm. 




Fig. T2. Ayrton and Ferry A7n?neter. 

Fig. 12 represents an ampere-meter devised by 
Ayrton and Perry. A device called a commutator 
for connecting the coils either in series or parallel 
is shown at C. Binding posts are provided at 
P, PS, and S. The dynamo terminals are con- 
nected at the posts P, PS, and the current will 
pass only when the coils are in multiple, thus 
avoiding accidental burning of the coils. In this 
case the entire current to be measured passes 
through the coils so coupled. The posts S and 
PS, are for connecting the single battery cell cur- 
rent. 

A great variety of ampere-meters, or ammeters, 
have been devised. They are nearly all, how- 



ever, constructed on essentially the same general 
principles. 

Commercial ammeters are made in a great va- 
riety of forms. When the currents to be meas- 
ured are large, as is generally the case in electric 
light or power stations, they consist of a coil of 
insulated wire, often of a single turn, or even of 
but a part of a turn, having a balanced core of 
iron or steel capable of moving freely within it. 

Ammeter, Electro-Magnetic A 

form of ammeter in which a magnetic needle is 
moved against the field of an electro-magnet 
by the field of the current it is measuring. 
(See Ami7ieter?) 

Ammeter, Gravity A form of am- 
meter in which a magnetic needle is moved 
against the force of gravity by the field of the 
current it is measuring. (See Amnteter^ 

Ammeter, Magnetic- Vane An 

ammeter in which the strength of a magnetic 
field produced by the current that is to be 
measured is determined by the repulsion ex- 
erted between a fixed and a movable iron 
vane, placed in said field and magnetized 
thereby. (See Voltmeter, Magnetic- Vane.) 

Ammeter, Permanent-Magnet A 

form of ammeter in which a magnetic needle 
is moved against the field of a permanent mag- 
net by the field of the current it is measuring. 
(See Ainmeter^) 

Ammeter, Reductenr for (See Re- 

ducteur, or Shunt for Ammeter.) 

Ammeter, Spring A form of am- 
meter in which a magnetic needle is moved 
against the action of a spring by the field of 
the current it is measuring. (See Ammeter.) 

Amorphous. — Having no definite crys- 
talline form. 

Mineral substances have certain crystalline 
forms, that are as characteristic of them as are the 
forms of animals or plants. Under certain cir- 
cumstances, however, they occur without definite 
crystalline form, and are then said to be amor- 
phous solids. 

Amperage. — The number of amperes pass- 
ing in a given circuit. 

The current strength in any circuit as indi- 
cated by an ampere-meter placed in the circuit. 



Amp.] 



19 



[Amp. 



Ampere. — The practical unit of electric 
current. 

Such a rate-of-flow of electricity as trans- 
mits one coulomb per second. 

Such a current (or rate-of-flow or trans- 
mission of electricity) as would pass with an 
electromotive force of one volt through a cir- 
cuit whose resistance is equal to one ohm. 

A current of such a strength as would 
deposit .005084 grain of copper per second. 

A current of one ampere is a current of such 
definite strength that it would flow through a cir- 
cuit of a certain resistance and with a certain 
electromotive force. (See Force, Electromotive. 
Volt. Resistance. Ohm.) 

Since the ohm is the practical unit of resistance, 
and the volt the practical unit of electromotive 
force, the ampere, or the practical unit of current, 
is the current that would flow through unit resist- 
ance, under unit pressure or electromotive force. 

To make this clearer, take the analogy of water 
flowing through a pipe under the pressure of a 
column of water. That which causes the flow is 
the pressure or head ; that which resists the flow 
is the friction of the water against the pipe, which 
will vary with a number of circumstances. The 
rate-of-Jlow may be represented by so many cubic 
inches of water per second. 

As the pressure or .head increases, the flow in- 
creases proportionally; as the resistance increases, 
the flow diminishes. 

Electrically, electromotive force corresponds to 
the pressure or head of the water, and resistance 
to the friction of the water and the pipe. The 
ampere, which is the unit rate-of-flow ptr second, 
may therefore be represented as follows, 

viz.: C = — , as was announced by Ohm in his 
R 

law. (See Law of Ohm.) 

This expression signifies that C, the current in 
amperes, is equal to E, the electromotive force in 
volts, divided by R, the resistance in ohms. 

We measure the rate-of-flow of liquids as so 
many cubic inches or cubic feet per second — that is, 
in units of quantity. We measure the rate-of-flow 
of electricity as so much electricity per second. 
The electrical unit of quantity is called the Coul- 
omb. (See Coulomb.) The coulomb is such a 
quantity as would pass in one second through a 
circuit in which the rate-of-flow is one ampere. 

An ampere is therefore equal to one coulomb per 
second. 



The electro-magnetic unit of current is such a 
current that, passed through a conducting wire 
bent into a circle of the radius of one centimetre, 
would tend to move perpendicular to its plane a 
unit magnetic pole held at its centre, and 
sufficiently long to practically remove the other 
pole from its influence, with unit force, i. e., the 
force of one dyne. (See Dyne.) The ampere, or 
practical electro-magnetic unit, is one-tenth of 
such a current ; or, in other words, the absolute 
unit of current is ten amperes. 

An ampere may also be defined by the chemical 
decomposition the current can effect as measured 
by the quantity of hydrogen liberated, or metal 
deposited. 

Defined in this way, an ampere is such a cur- 
rent as will deposit .001 118 15 gramme, or 
.017253 grain, of silver per second on one of the 
plates of a silver voltameter, from a solution of 
silver nitrate containing from 15 to 30 per cent, of 
the salt (See Voltameter), or which will decompose 
.00009326 gramme, or .001439 g ra i n °f dilute 
sulphuric acid per second, or pure sulphuric acid 
at 59 degrees F. diluted with about 15 per cent, of 
water, that is, dilute sulphuric acid of Sp. Gr. of 
about 1.1. The present scientific and commercial 
practice is to take the ampere to be such a current 
as will deposit 4. 024 grammes of silver in one hour. 

Ampere Arc. — (See Arc, Ampere) 

Ampere-Feet. — (See Feet, Ampere.) 

Ampere-Hour. — (See Hour, Ampere) 

Ampere-Meter. — An ammeter. (See Am- 
meter) 

Ampere-Meter, Balance or Neutral Wire 

An ampere-meter placed in the cir- 
cuit of the neutral wire, in the three-wire sys- 
tem of electric distribution, for the purpose of 
showing the excess of current passing over 
one side of the system as compared with the 
other side, when the central wire is no longer 
neutral. 

Ampere-Minute. — (See Minute, Ampere) 
Ampere Ring. — (See Ring, Ampere) 
Ampere-Second. — (See Second, Ampere.) 
Ampere Tap. — (See Tap, Ampere) 
Ampere-Turn. — (See Tur7i, Ampere) 

Ampere-Turn, Primary (See Turn, 

Ampere, Primary) 



Amp. 



20 



[Ane. 



Ampere-Turn, Secondary — (See 

Turn, Ampere, Secondary '.) 

Ampere-Volt. — A watt, or the T je of a 
horse-power. 

This term is generally written volt-ampere. 
(See Volt-Ampere.) 

Ampere-Winding. — (See Winding, Am- 
pere) 

Ampere's Rule for Effeet of Current on 
Needle. — (See Rule, Ampere s, for Effect of 
Current on Needle.) 

Ampere's Theory of Magnetism. — (See 
Magnetism, Ampere s Theory of) 

Amperian Currents. — (See Currents, Am- 
pler ian) 

Amplitude of Vibration or Wave. — (See 
Vibration or Wave, Amplitude of) 

Ammunition-Hoist, Electric — An 

electrically operated hoist for raising ammu- 
nition to the deck of a ship. 

In the electric ammunition-hoist the electric 
motor which moves the hoist is made to follow the 
motions of the operator's hand, both as regards 
direction and speed. The motion of a crank, or 
wheel, causes a switch to start an electric motor in 
a ctrtain direction, which tends to close the switch, 
thus necessitating a race between the operator 
and the motor. Should the operator begin to 
close the switch more slowly, the m^tor will over- 
take him, will partially close the switch, and thus 
lower the speed of the motor. 

Analogous Pole. — (See Pole, Analogous) 

Analysis. — The determination of the com- 
position of a compound substance by separ- 
ating it into the simple or elementary sub- 
stances of which it is composed. 

Analysis, Electric The determin- 
ation of the composition of a substance by 
electrical means. 

Various processes have been proposed for elec- 
tric analysis; they consist essentially in decompos- 
ing the substance by means of electric currents, 
and are either qualitative or quantitative. (See 
Electrolysis.) 

Analysis, Electrolytic A term 

sometimes used instead of electric analysis. 
(See Analysis, Electric) 

Analysis, Qualitative A chemical 



analysis which merely ascertains the kinds of 
elementary substances present. 

Analysis, Quantitative A chemical 

analysis which ascertains the relative propor- 
tions in which the different components enter 
into a compound. 

Analyzable. — Separable into component 
parts. 

Analyze. — To separate into component 
parts. 

Analyze, Electrically To separate 

electrically into component parts. 

Analyzer, Electric A gridiron of 

metallic wires which is transparent to electro- 
magnetic waves, when its length is perpendic- 
ular to them, but opaque to them — z. e., 
possessing the ability to reflect them — when 
rotated 90 degrees from its former position. 

The electric analyzer, it will be observed, is 
analogous to an analyzer for polarized light. A 
reflecting surface, for example, being able to re- 
flect polarized light in a given position, and unable 
to reflect it when rotated 90 degrees from such 
position, is capable of acting as an analyzer for 
polarized light. 

Analyzer, Gray's, Harmonic Telegraphic 

An electro-magnet, the armature of 

which consists of -a steel ribbon stretched in 
a metallic frame and capable through regula- 
tion, as to tension, by means of a screw, of 
being tuned to a certain note. 

The steel ribbon is thrown into vibration when- 
ever pulsations from the transmit ing instruments 
are sent over the line corresponding to the rate cf 
motion of the ribbon, but is not set into vibration 
by any others. If, therefore, a number of different 
analyzers, tuned to different notes, are placed on 
the same line, each will be operated only by the 
pulsations sent into the line corresponding to its 
rate of motion, and thus multiple transmission in 
the same direction is possible. In order to 
strengthen the tones of the analyzers, each is pro- 
vided with a resonant air column. (See Reson- 
ator. Telegraphy, Multiplex.) 

Analyzing. — Separating into component 
parts. 

Anelectric. — A word formerly applied to 
bodies (conductors) which it was believed 
could not be electrified by friction. 



Aiie.] 



21 



[Ani. 



This term is now obsolete. Conductors are 
easily electrified, when insulated. 

Anelectrotonic State. — (See State, Anelec- 
trotonzc.) 

Anelectrotonic Zone. — (See Zone, Anelec- 
trotonic^) 

Anelectrotonus. — In electro-therapeutics, 
the decreased functional activity which occurs 
in a nerve in the neighborhood of the anode, 
or positive electrode, when applied therapeu- 
tically. (See EZectrotonus.) 

Anemometer, Electric An appa- 
ratus to electrically record or indicate the direc- 
tion and intensity of the wind. 

In the electric recording anemometer, the force 
or velocity of the wind, or both, are recorded on 
a moving sheet of paper, on which the time is 
marked, so that the txact time of any given 
change is known. 

Anemoscope. — An instrument which indi- 
cates, but does not measure the intensity or 
record the direction of the wind. 

The word is often, though improperly, used in- 
terchangeably for anemometer. 

Angle. — The deviation in direction between 
two lines or planes that meet. 

Angles are measured by arcs of circles. The 
angle at B A C, Fig. 13, is the deviation of the 
straight line A B, from A 
C. In reading the let- 
tering of an angle the 
letter placed in the mid- 
dle indicates the angle 
referred to. Thus B A 

C, means the angle be- D A C 
tween A B and A C; B A Fig. i3> Angles. 

D, the angle between B A and A D. Angles are 
valued in degrees, there being 360 degrees in an 
entire circumference or circle. Degrees are in- 
dicated thus: 90 , or ninety degrees. 

Angle, Acute An angle whose value 

is less than a right angle or 90 degrees. 

B A E, or E A D, in Fig. 13, is an acute angle. 

Angle, Complement of What an 

angle needs to make its value 90 degrees, or a 
right angle. 

Thus in Fig. 13, B A E, is the complement of 
the angle E A D, since B AE+EAD = 9 o 
degrees. 




— — An angle whose 
value is greater than a right angle or 9a 
degrees. 

E A C, Fig. 13, is an obtuse angle. 

Angle of Declination or Variation. — (See 
Declination, Angle of. Variation, Angle of.} 

Angle of Difference of Phase Between 
Alternating Currents of Same Period. — 
(See Phase, Angle of Difference of, Between 
Alternating Currents of Same Period?) 

Angle of Dip. — (See Dip. Dip or Incli- 
nation, Angle of) 

Angle of Inclination. — (See Dip or Incli- 
nation, Angle of.) 

Angle of Lag of Dynamo-Electric Ma- 
chine. — (See Lag, Angle of, of Dynamo- 
Electric Machine) 

Angle of Lead. — (See Lead, Angle of) 

Angle of Variation. — (See Variation , 
Angle of) 

Angle, Plane An angle contained 

between two straight lines. 

Angle, Salid An angle contained 

between two surfaces. 

Angle, Supplement of What an 

angle needs to make its value 180 degress, or 
two right angles. 

Thus in Fig. 13, E A C, is the supplement of 
E A D, because EAD-)-EAC = 180 degrees, 
or two right angles. 

Angle, Unit An angle of 57.29578 

or 57 17' 44.8" nearly. — (See Velocity, An- 
gular) 

Angular Currents. — (See Currents, An- 
gular) 

Angular Velocity. — (See Velocity, Angu- 
lar) 

Animal Electricity. — (See Electricity ', 
Animal) 

Animal Magnetism. — (See Magnetism y 
Animal) 

Anion. — The electro-negative radical of a 
molecule. 

Literally, the term ion signifies a group of 
wandering atoms. An anion is that group of 
atoms of an electrically decomposed or electrolyzed 



Aui.] 



22 



[Ann. 



mol-cule which appears at the anode. (See 
Electrolysis. Anode.) 

As the anode is connected with the electro- 
positive terminal of a source, the onion is the 
electro-negative radical or group of atoms, and 
therefore appears at the electro-positive terminal. 

A kathion, or electro-positive radical, appears 
at the kathode, which is connected with the 
electro-negative terminal of the battery. Oxygen 
and chlorine are anions. Hydrogen and the 
metals are kathions. 

Anisotropic Conductor. — (See Conductor, 
Anisotropic.) 

Medium. — (See Medium, 



Anisotropic 

Anisotropic.) 

Annealing, 



Electric 



process 



for annealing metals in which electric heating 
is substituted for ordinary heating. 

Annual Inequality of Earth's Magnet- 
ism. — (See Inequality, Annual, of Earth's 
Magnetism. 

Annual Variation of Magnetic Needle. 

— (See Needle, Magnetic, Anmtal Variation 
of-) 

Annunciator, Burglar- Alarm An 

annunciator used in connection with a system 
of burglar-alarms. (See Alarm, Burglar?) 

Annunciator Clock, Electric — 

(See Clock, Electric Anmmciator.) 

Annunciator Drop.— (See Drop, Anmm- 
ciator?) 

Annunciator Drop, Automatic 

(See Drop, Automatic Annunciator?) 

Annunciator, Electro-Magnetic 

An electric device for automatically indicating 
the points or places at which one or more 
electric contacts have been closed. 

The character of the annunciator depends, of 
course, on the character of the places at which 
these points, places or stations are situated. 

Annunciators are employed for a variety of 
purposes. In hotels they are used for indicating 
the number of a room the occupant of which 
desires some service, which he signifies by push- 
ing a button, thus closing an electric circuit. 
This is indicated or announced on the annuncia- 
tor by the falling of a drop, on which is printed a 
number corresponding with the room, and by the 



ringing of a bell to notify the attendant. The num- 
ber is released by the movement of the armature 
of an electro-magnet. The drops are replaced in 
their former position by some mechanical device 
operated by the hand. In the place of a drop a 



IfllllWBaHWUEi: 






Fig. 14. Electro-Magnetic Annunciator. 

needle is sometimes u^-ed, which, by the attraction 
of the armature of an electro-magnet, points to 
the number signaling. 

Annunciators for houses, burglar-alarms, fire- 
alarms, elevators, etc., are 
of the same general con- 
struction. 

Annunciators are general- 
ly operated by electro-mag- 
netic attraction or repulsion, 
and are therefore some- 
times called electro-magnetic 
annunciators. 

Fig. 14 shows an annun- 
ciator suitable for use in 
hotels. 

The numbers 28 and 85 
are represented as having 
been dropped by the closing 
of the circuit connected 
with them. 

Annunciator, Eleva- 
tor An annuncia- 
tor connected with an 
Fig. 15. Elevator elevator to indicate the 

Annunciator. n . ,. 

floor signaling. 
One form of elevator annunciator is shown in 
Fig- 15- 




Ann.] 



23 



[Anil, 



Annunciator, Fire-Alarm An 

annunciator used in connection with a system 
of fire-alarms. 

Annunciator, Gravity-Drop — An 

annunciator whose signals are operated by 
the fall of a drop. 




1 6. Gravity-Drop Annunciator. 



A form of gravity-drop annunciator is shown 
in Fig. 16. The armature mechanism for the 
release of the drop will be understood by an in- 
spection of the drawing. 

Annunciator, Hotel An annun- 
ciator connected with the different rooms of a 
hotel. 

A hotel-annunciator is generally provided with 
a return bell and guest-call. 

Annunciator, House An annun- 
ciator connected with the rooms of a house. 

Annunciator, Needle An annun- 
ciator, the indications of which are given by 
the movements of a needle instead of the fall 
of a drop. 

A form of needle-annunciator is shown in 
Fig. 17. 

Annunciator, Oral or Speaking" Tube 

An annunciator electrically operated 



by means of a puff of breath transmitted 
through an ordinary speaking tube. 

The oral-annunciator is a contrivance whereby 
a central office is placed in communication with a 
number of speaking tubes coming from different 
points in a hotel or other place. A person 
in any room, who wishes to communicate 
with the central office, blows through the 
speaking tube in his room, and thus, by 
effecting an electric contact, rings a bell and 
operates a drop at the annunciator, thus indicat- 
ing the exact tube at which the attendant is to 
receive the message. The attendant can thus be 
placed in easy communication with each of the 
rooms whose speaking tubes connect with the 
annunciator. 

Annunciator, Pendulum or Swinging- 

— An annunciator, the indicating arm of 
which consists of a pendulous, or swinging arm, 




Fig. 17. Needle- Annunciator. 

which, when at rest, points vertically down- 
ward, and which is moved to the right or left 
by the action of the current. 

Pendulous, or swinging-annunciators are gen- 
erally so arranged as to need no replacement. 



Auo.] 



U 



[App. 



On the cessation of the current the indicator arm 
drops vertically downward. 

A relay is preferably used with pendulum- 
annunciators, since the rapid makes and breaks 
of the current by the bell alarm interlere with 
their satisfactory action. 

* Anodal. — Pertaining to the anode. (See 
Anode.) 

Anodal Diffusion.— (See Diffusion, Ano- 
dal^) 

Anode. — The conductor or plate of a de- 
composition cell connected with the positive 
terminal of a battery, or other electric source. 

That terminal of an electric source out of 
which the current flows into the liquid of a 
decomposition cell or voltameter is called the 
anode. 

That terminal of an electric source into 
which the current flows from a decomposition 
cell or voltameter is called the kathode. 

The anode is connected with the carbon or 
positive terminal of a voltaic battery, and the 
kathode with the zinc, or negative terminal. 
Therefore the word anode has been used to 
signify the positive terminal of an electric source, 
and kathode, the negative terminal, and in this 
sense is employed generally in electro-thera- 
peutics. It is preferable, however, to restrict the 
use of the words anode and kathode to those 
terminals of a source at which electrolysis is 
taking place. 

The terms anode and kathode in reality refer 
to the electro-receptive devices through which 
the current flows. Smce it is assumed that the 
current flows out of a source from its positive 
pole or terminal, and back through the source at 
its negative pole or terminal, the pole of any 
device which is connected with the positive pole 
of a source is the part or place at which the 
current enters and flows through it, and that 
connected with the negative pole, the part at 
which it leaves. Hence, probably, the change 
in the use of the words already referred to. 

Since the anion, or the electro negative radical, 
appears at the anode, it is the anode of an electro- 
plating bath, or the plate connected with the 
positive terminal of the source, that is dissolved. 
k When the term anode was first proposed by 
Faraday, voltaic batteries were the only available 
electric source, and the term referred only to the 



positive terminal of a voltaic battery when 
placed in an electrolyte. 

Anodic. — Pertaining to the anode. (See 
Anode?} 

Anodic Electro-Diagnostic Reactions. — 

(See Reactions, Kathodic and Anodic Elec- 
tro-Diagnostic?) 

Anodic Opening Contraction. — (See Con- 
tration, Anodic Openi?ig.) 

Anomalous Magnet. — (See Magnet, An- 
omalous?) 

Anomalous Magnetization. — (See Mag- 
netization, Anomalous?) 

Anti-Induction Cable (See Cable, 

Ant i- In dtiction .) 

Anti-Induction Conductor. — (See Con- 
ductor, Anti-Induction?) 

Antilogous Pole. — (See Pole, Antilogous?) 

Anvil. — The front contact of a telegraphic 
key that limits its motion in one direction. 
(See Key, Telegraphic?) 

Aperiodic Galvanometer. — (See Galva- 
nometer, Aperiodic?) 

Apparatus, Faradic-Induction 

An induction coil apparatus for producing 
faradic currents. 

A voltaic battery is connected with the primary 
of an induction coil, and its current rapidly 
broken by an automatic break, or by a hand 
break. The alternating or faradic currents thus 
produced in the secondary coils are used for 
electro-therapeutic purposes. (See Coil, Induc- 
tion?) 

Faradic induction apparatus is made in a great 
variety of forms. They all operate, however, on 
essentially the same principles. 

Apparatus, Faradic, Magneto-Electric 

A small magneto-electric machine 

employed in electro-therapeutics for producing 
faradic currents. 

Magneto-electric faradic machines consist essen- 
tially of a coil of wire wrapped on an armature 
core that is rotated before the poles of permanent 
magnets. No commutator is employed, since it is 
desired to obtain rapidly alternating currents. 

Apparatus, Interlocking — Devices 

for mechanically operating from a distant signal 



App.] 



25 



LA re. 



tower, railroad switches and semaphore signals 
for indicating the position of such switches,- 
by means of a system of interlocking levers, 
so constructed that the signals and the 
switches are so interlocked as to render it 
impossible, after a route has once been set up 
and a signal given, to clear a signal for a 
route that would conflict with the one previ- 
ously set up. (See Block System for Rail- 
roads?) 

Apparatus, Magneto-Electric Medical 
A term applied to small magneto- 
electric machines employed in medical elec- 
tricity for the production of uncommuted 
or faradic currents. (See Apparatus, Fara- 
dic, Magneto-Electric?) 

Apparatus, Registering', Electric 

Devices for obtaining permanent records by 
electrical means. 

Apparatus, Registering, Telegraphic 

— A name sometimes given to a telegraphic 
recorder. (See Recorder, Chemical, Barn's. 
Recorder, Morse. Recorder, Siphon?) 

Apparent Co-efficient of Induction. — 

(See Induction, Apparent Co-efficient of.) 

Arago's Disc. — (See Disc, Arago's.) 

Arc. — A voltaic arc. (See Arc, Voltaic?) 

Arc. — To form a voltaic arc. 

A dynamo-electric machine is said to arc at the 
commutator, when the current passes as visible 
sparks across the spaces between adjacent seg- 
ments. 

This action at the commutator is more gener- 
ally called sparking or burning. 

Arc, Alternating A voltaic arc 

formed by means of an alternating current. 

In order to avoid the extinction of the arc a 
certain number of alternations per second is nec- 
essary. The alternating arc produces a loud 
singing noise. At very high frequencies, how- 
ever, the noise disappears. 

The alternating arc, not possessing a fixed posi- 
tive crater, requires to be covered by a good 
reflector to throw the light downward. 

Arc, Ampere A single conductor 

bent in an arc of a circle, and used in electric 
balances for measuring the electric current. 



Arc Blow-Pipe.- 

tric Arc.) 
Arc, Compound- 



-(See Blow-Pipe, Elec- 



-An arc formed 



between more than two separate electrodes. 

Arc, Counter Electromotive Force of 

An electromotive force generally be- 
lieved to be set up on the formation of a 
voltaic arc, opposed in direction to the electro- 
motive force maintaining the arc. (See Force, 
Electro?notive, Counter?) 

This counter electromotive force is believed to 
have its origin partly in the energy absorbed at 
the crater of the positive carbon, where the car- 
bon is volatilized, and given out at the nipple on 
the negative carbon, where it is deposited or 
solidified. It is to be noted in this connection 
that the apparent resistance of the carbon voltaic 
arc is not directly proportional to the length of 
the arc. 

Arc, Electric A term sometimes 

used for the voltaic arc. (See Arc, Voltaic?) 

Arc, Frying of A frying sound at- 
tending the formation of a voltaic arc when 
the carbons are too near together. 

The cause of the frying sound is probably the 
same as that of hissing. (See Arc, Hissing of.) 

Arc, Hissing of A hissing sound 

attending the formation of voltaic arcs when 
the carbons are too near together. 

The cause of the hissing is not entirely under- 
stood. Prof. Elihu Thomson suggests that it is 
due to a too rapid volatilization of the carbons. 

Arc Lamp. — (See Lamp, Arc.) 

Arc Lamp, Electric (See Lamp, 

Electric Arc.) 
Arc Lamp, Triple Carbon Electric 

— (See Lamp, Arc, Triple Carbon Electric?) 
Arc Lighting. — (See Lighting, Arc.) 

Arc, Metallic A voltaic arc formed 

between metallic electrodes. 

When the voltaic arc is formed between metallic 
electrodes instead of carbon electrodes, a flaming 
arc is obtained, the color of which is characteristic 
of the burning metal ; thus copper forms a brill- 
iant green arc. The metallic arc, as a rule is 
much longer than an arc with the same current 
taken between carbon electrodes. 

Arc Micrometer. — (See Micrometer, Arc.) 



Arc] 



26 



[Arc 



Arc, Noisy 



-A voltaic 



the 



maintenance of which is attended by frying, 
hissing, or spluttering sounds. 

Arc, Quiet A voltaic arc which is 

maintained without sensible sounds. 



Arc, Roaring" of 



-A roaring sound 



attending the formation of a voltaic arc when 
the carbons are too near together and a very 
powerful current is used. 

Arc, Simple An arc formed be- 
tween two electrodes. 

Arc, Spluttering of A spluttering 

sound attending the formation of a voltaic 
arc. 

Prof. Elihu Thomson suggests that the cause of 
spluttering is due to the presence of impurities in 
the carbons, or from the sudden evolution of gas 
from insufficiently baked carbons. 

Arc, Yoltaic The brilliant arc or 

bow of light which appears between the elec- 
trodes or terminals, generally of carbon, of a 
sufficiently powerful source of electricity, when 
separated a short distance from each other. 

The source of light of the electric arc lamp. 

It is called the voltaic arc because it was first 
obtained by the use of the battery invented by 
Volta. The term arc was given to it from the 
shape of the luminous bow or arc formed between 
the carbons. 

To form the voltaic arc the carbon electrodes 
are first placed in contact and then gradually 
separated. A brilliant arc of flame is formed be- 
tween them, which consists mainly of volatilized 
carbon. The electrodes are consumed, first, by 
actual combination with the oxygen of the air; 
and, second, by volatilization under the combined 
influence of the electric current and the intense 
heat. 

As a result of the formation of the arc, a crater 
is formed at the end of the positive carbon, and 
appears to mark the point out of which the 
greater part of the current flows. 

The crater is due to the greater volatilization 
of the electrode at this point than elsewhere. 
It marks the position of highest temperature of the 
electrodes, and is the main source of the light of 
the arc. When, therefore, the voltaic arc is em- 
ployed for the purposes of illumination with 
vertically opposed carbons, the positive carbon 
should be made the upper carbon, so that the 



focus of greatest intensity of the light may be 
favorably situated for illumination of the space 
below the lamp. When, however, it is desired to 
illumine the side of a building above an arc lamp, 
the lower carbon should be made positive. 

The positive carbon is consumed about twice as 
rapidly as the negative, both because the negative 
oxygen attacks the points of the positive carbon, 
and because the positive carbon suffers the most 
rapid volatilization. 

The electric current passes through the space 
occupied by the voltaic arc because — 

(i.) The heated arc is a partial conductor of 
electricity. 

(2.) Because small charges of electricity are 
carried bodily forward from the positive to the 
negative carbon through the space of the voltaic 
arc, by means of the minute particles which are 
volatilized at the positive electrode. 

S. P. Thompson has shown that the tempera- 
ture of the light-emitting surface of the carbon is 
the temperature of the volatilization of carbon, 
and is therefore constant. 

Dr. Fleming found that " A rise of potential 
along the arc takes 
place very suddenly, 
just in the neighbor- 
hood of the crater." 

The crater in the 
end of the positive car- 
bon is seen in Fig. 18. 
On the opposed end 
of the negative carbon 
a projection or nipple 
is formed by the de- 
posit of the electrical- 
ly volatilized carbon. 
Fig. 18. Voltaic Arc. The rounded masses 
or globules that appear on the surface of the elec- 
trodes are due to deposits of molten foreign mat- 
ters in the carbon. 

The carbon, both of the crater and its opposed 
nipple, is converted into pure, soft graphite. 

Arc, Yoltaic, Resistance of The 

resistance offered by the voltaic arc to the 
passage of the current. 

As in all other conductors, the ohmic resistance 
of the arc increases with its length, and decreases 
with its area of cross- section. The apparent 
resistance, however, is not directly proportional 
to the length. An increase of temperature de- 
creases the resistance of the voltaic arc. 




Arc] 



27 



[Arm, 



The total apparent resistance of the voltaic arc 
is composed of two parts, viz.: 

(i.) The true ohmic resistance. (See Resist- 
ance, Ohmic.) 

(2.) The counter electromotive force, or spuri- 
ous resistance. (See Resistance, Spurious.) 

Arc, Watt A voltaic arc, the elec- 
tric power of which is equal to a given number 
of watts. 

The ordinary long-arc, as employed in arc 
lighting, has a difference of potential of about 45 
volts and a current strength of about 10 amperes. 
It is, therefore, a 450-watt arc. 

Arch, Auroral The archlike form 

sometimes assumed by the auroral light. (See 
Aurora Borealis) 

Arcing. — Discharging by means of voltaic 
arcs. (See Arc, Voltaic.) 

Arcing at the commutator of a dynamo-electric 
machine not only prevents the proper operation 
of the machine, but eventually leads to the de- 
struction of the brushes and the commutator. 

Areometer, Bead A form of are- 
ometer suitable for rapidly testing the density 
of the liquid in a storage cell. 

The bead areometer consists of a glass tube, 
open at both top and bottom, containing a few 
glass beads, so weighted as to float at liquid 
densities such as 1. 105, 1.170, 1.190 
and 1.200. To use the instrument, 
it is immersed in the liquid of the 
storage cell, and then withdrawn. 
The finger being kept in the upper 
opening, the liquid does not escape 
through the small opening at the 
bottom. The density is then ascer- 
tained by noting the beads that 
float. 

Areometer or Hydrometer. 

— An instrument for determin- 
ing the specific gravity of a liquid. 
A common form of hydrometer 
consists, as shown in Fig. 19, of a 
closed glass tube, provided with a 
bulb, and filled at the lower end 
with mercury or shot, so as to in- 
sure its vertical position when Fig. ig. H y - 
floating in a liquid. When placed drometer. 
in different liquids, it floats with part of the tube 
out of the liquid. The lighter the liquid, the 



smaller is the portion that remains out of the 
liquid when the instrument floats. The specific 
gravity is determined by observing the depth to 
which the instrument sinks when placed in different 
liquids, as compared with the depth it sinks when 
placed in water < 

Areometry. — The measurement of specific 
gravity by means of an areometer. 

Argand Burner, Electric Hand-Lighter 
(See Burner, Argand, Electric Hand- 
Lighter?) 

Argand Burner, Electric Plain-Pendant 

(See Burner, Plain Pendant, Argand, 

Electric?) 

Argand Burner, Electric Ratchet-Pen- 
dant (See Burner, Ratchet-Pendant, 

Argand, Electric) 

Argyrometry. — The art of determining 
the weight of electrolytically deposited silver. 
(See Balance, Plating) 

Arm, Balance One of the resist- 
ances of an electric balance. (See Arms, 
Bridge or Balance. Bridge, Electric.) 

Arm, Bridge A bridge arm. (See 

Arms, Bridge or Balance) 

Arm, Cross A horizontal beam at- 
tached to a pole for the support of the in- 
sulators for telegraph, electric light or other 
electric wires. 

A telegraphic arm. (See Arm, Tele- 
graphic) 

Arm, Rocker An arm on which the 

brushes of a dynamo or motor are mounted 
for the purpose of shifting their position on 
the commutator. 

Arm, Semaphore The movable 

arm of the signal apparatus employed in block 
systems for railroads, for the purpose of in- 
forming engineers of trains of the condition 
of the road as regards other trains. 

In the absolute block system, as used on some 
roads, there are two positions for the semaphore 
arm, viz.: 

( 1 . ) For Danger — when in a horizontal position, 
or at 90 degrees with the vertical supporting pole. 

(2. ) Clear— when dropped below the horizontal 
position through an angle of 75 degrees. 

In the Permissive Block System, a third position 



Arm.] 



28 



[Arm. 



intermediate between the 1st and the 2d, or at an 
angle of 37 degrees 30 minutes with the horizontal 
position, is used for caution. (See Block System 
for Railroads. .) 



Armature, Bi-polar 



-An armature 



Arm, Signal 



-A semaphore arm. 



(See Arm, Semaphored) 
Arm, Telegraphic - 



— a cross-arm 
placed on a telegraphic pole for the support 
of the insulators. 

These arms are generally called cross-arms. 

Armature. — A mass of iron or other 
magnetizable material placed on or near the 
pole or poles of a magnet. 

In the case of a permanent ?nagnet, the arma- 
ture, when used as a keeper, is of soft iron and is 
placed directly on the magnet poles. In this case 
it preserves or keeps the magnetism by closing 
the lines of magnetic J orce of the magnet through 
the soft iron of the armature, and is then called a 
keeper. (See Force, Magnetic, Lines of.) 

In the case of an electro-magnet, the armature 
is placed near the poles, and is moved toward 
them whenever the magnet is energized by the 
passage of the current through the magnetizing 
coils. This movement is made against the action 
of a spring or weights, so that on the loss of 
magnetism by the magnet, the armature moves 
from the magnet poles. (See Magnet, Permanent. 
Magnet, Keeper of. ) 

When the armature is of soft iron it moves to- 
ward the magnet on the completion of the circuit 
through its coils, no matter in what direction 
the current flows, and is then called a non-polar- 
ized armature. (See Armature, Non- Polarized. ) 

When made of steel, or of another electro-mag- 




Fig.20. Bi-polar Armature. 

net, it moves from or toward the poles, accord- 
ing to whether the poles of the armature are of 
the same or of a different polarity from those of 
the magnet. Such an armature is called a 
polarized armature. (See Armature, Polarized.) 



of a dynamo-electric machine the polarity of 
which is reversed twice in every revolution 
through the field of the machine. 

A form of bi-polar armature is shown in Fig. 20. 
The word bi-polar armature is not generally 
employed. The term applies rather to the field- 
magnet poles than to the armature. 

Armature Bore. — (See Bore, Armature?) 

Armature Bore, Elliptical (See 

Bore, Elliptical Armature?) 

Armature Chamber. — (See Chamber, 
Armature?) 

Armature Coils, Dynamo — (See 

Coils, Armature, of Dyna?no-Electric Ma- 
chine?) 

Armature Core, Dynamo — (See 

Core, Armature, of Dynamo-Electric Ma- 
chine?) 

Armature, Cylindrical A term 

sometimes applied to a drum armature. 
(See Armature, Drum. Armature, Dy- 
namo-Electric Machine?) 

Armature, Cylindrical Ring. — A ring 
armature with a core in the shape of a com- 
paratively long cylinder. 

Armature, Disc An armature of a 

dynamo-electric machine, in which the arma- 
ture coils consist of flat coils, supported on 
the surface of a disc. (See Armature, Dy- 
namo-Electric Machine?) 

Armature, Dissymmetrical Induction of 

Any induction produced in the arma- 
ture of a dynamo-electric machine that is un- 
equal in amount on opposite halves, or in sym- 
metrically disposed portions of the armature. 

Dissymmetrical induction in the armature may 
cause annoying or injurious sparking at the com- 
mutator. It may arise — 

( 1 . ) From a lack of symmetry in the amount of 
the armature windings. 

(2.) From a lack of symmetry in the arrange- 
ment of the armature windings on the armature 
core. 

(3. ) From a lack of symmetry of the pole pieces 
of the machine. 

(4.) From an improper position of the brushes 



Arm.] 



29 



[Arm, 



as regards the neutral point on the commutator, 
causing a temporary short-circuiting of one or 
more of the armature coils. 

Armature, Drum An armature of 

a dynamo-electric machine, in which the 
armature coils are wound longitudinally over 
the surface of a cylinder or drum. (See 
Armature, Dy7iamo-Electric Machine) 

A form of drum-armature is shown in Fig. 21. 




Fig. 21. Drum- Armature. 

Armature, Dynamo-Electric Machine 

The coils of insulated wire tog-ether 



with the iron armature core, on or around 
which the coils are wound. 

That part of a dynamo-electric machine in 
which the differences of potential which 
cause the useful currents are generated. 

Generally, that portion of a dynamo-elec- 
tric machine which is revolved between the 
pole pieces of the field magnets. 

The armature of a dynamo-electric machine 
usually consists of a series of coils of insulated 
wire or conductors, wrapped around or grouped 
on a central core of iron. The movement of 
these wires or conductors through the magnetic 
field of the machine produces an electric cur- 
rent by means of the electromotive forces so gen- 
erated. Sometimes the field is rotated ; some- 
times both armature and field rotate. 

The armatures of dynamo-electric machines 
are of a great variety of forms. They may for 
convenience be arranged under the following 
heads, viz. : 

Cylindrical or drum-armatures, dis car ma- 
tures, pole or-radial armatures, ring armatures, 
and spherical-armatures. For further particulars 
see above terms. Armatures are also divided 



into classes according to the character of the 
magnetic field through which they move — viz.: 
unipolar, bipolar, and multipolar armatures. 

The English sometimes use the word cylindrical 
armature as a synonym of ring-armature. 

A unipolar-armature is one whose polarity is 
never reversed. A bipolar -armature is one in 
which the polarity is reversed twice in every 
rotation; multipolar armatures have their po- 
larity reversed a number of times in every rota- 
tion. 

The term armature as applied to a dynamo- 
electric machine was derived from the fact that 
the iron core acts to magnetically connect the 
two poles of the field magnets in the same 
manner that an ordinary armature connects the 
poles of a magnet. 

Armature, Flat Ring" A ring-arma- 
ture with a core in the shape of a short cylin- 
drical ring. 

Armature, Girder — An armature 

with an H- sna P e d or girder-like core. 
An H -shaped armature. 

Armature, Intensity An old term 

for an armature with coils of many turns and 
of a comparatively high resistance. 

Armature, Lamination of Core of 

— A division of the iron core of the armature 
of a dynamo-electric machine or motor, so as 
to avoid the formation of eddy-currents 
therein. (See Core, Lamination of. Cur- 
rents, Eddy) 

Armature, Multipolar A dynamo- 
electric machine armature whose polarity is 
reversed more than twice during each rotation 
in the field of the machine. 

Armature, Neutral A non-polarized 

armature. (See Armature, Non-Polarized) 

Armature, Neutral-Relay A relay 

armature, consisting of a piece of soft iron, 
which closes a local circuit whenever its elec- 
tro-magnet receives an impulse over the main 
line. [See Armature, Polarized) 

This term is applied in contradistinction to a 
polarized relay armature. 

Armature, Non-Polarized — An 

armature of soft iron, which is attracted toward 
the poles of an electro-magnet on the comple- 



Arm.] 



30 



[Arm. 



tion of the circuit, no matter in what direc- 
tion the current passes through the coils. 

The term non-polarized is ustd in contradistinc- 
tion to polarized armature. (See Armature, 
Polarized. ) 

The non-polarized armature of a relay magnet 
is generally called the neutral relay armature. 

Armature of a Cable, or Cable-Armature. 

— A term sometimes employed for the sheath- 
ing or protecting coat of a cable. 

The term armor sheathing or coating is prefer- 
able. 

Armature of a Condenser, or Condenser 
Armature. — A term sometimes applied to 
the metallic plates of a condenser or Leyden 
jar. 

The use of this term is unnecessary and ill- 
advised. The term coating or plate would appear 
to be preferable. 

Armature of Holtz Machine, or Holtz- 
Machine Armature. — The pieces of paper 
that are placed on the stationary plate of the 
Holtz and other similar electrostatic induction 
machines. 

Armature Pockets. — (See Pockets, Ar7na- 
ture.) 

Armature, Polarized An armature 

which possesses a polarity independent of 
that imparted by the magnet pole near which 
it is placed. 

In permanent magnets the armatures are made 
of soft iron, and theretore, by induction, become 
of a polarity opposite to that of the magnet poles 
that lie nearest them. They have, therefore, only 
a motion of at taction toward such poles. (See 
Induction, Magnetic. ) 

In electro-magnets the armatures may either be 
made of soft iron, in which case they are attracted 
only on the passage of the current; or they may 
be formed of permanent steel magnets, or may be 
electro-magnets themselves, in which case the pas- 
sage of the current through the coils of the elec- 
tro-magnet, or electro-magnets, may cause either 
attraction or repulsion, according as the adjacent 
poles are of opposite polarity or are of the same 
polarity. 

Armature, Pole An armature the 

coils of which are wound on separate poles 



that project radially from the periphery of a 
disc, drum or ring. 
A pole-armature showing the arrangement of 




Fig. 22. Pole -Armature. 
the coils and their connection to the commutator 
segments is seen in Fig. 22. 

Armature, Quantity An old term 

for an armature wound with but a few coils 
of comparatively low resistance. 

Armature, Radial A term some- 
times used instead of pole-armature. (See 
Armature, Pole) 

Armature, Ring A dynamo-electric 

machine armature, the coils of which are 
wound on a ring-shaped core. 

. c 




Fig. 23. Ring-Armature. 

A ring-armature is shown in Fig. 23, together 
with the disposition of the coils and their connec- 
tion to the segments of the commutator. 

Armature, Shuttle A variety of 

drum armature in which a single coil of 
wire is wound in an H -shaped groove formed 
in a bobbin shaped core. 

The old form of Siemens-armature. 

Armature, Sing-le-Loop A closed 

conducting circuit consisting of a single loop, 
capable of revolving in a magnetic field so as 
to cut its lines of force. 

Armature, Spider.— (See Spider, Arma- 
ture) 



Arm.] 



31 



[Arr, 



Armature, Spherical 



-A dynamo- 



electric machine armature, the coils of which 
are wound on a spherical iron core. 

The Thomson-Houston dynamo, which is the 
only machine employing an armature of this type, 
has its armature formed by wrapping three coils 
of insulated wire on a core of iron so shaped as 
to insure an approximately spherical armature 
when wrapped. 

Armature, Toothed-Ring- An ar- 
mature, the core of which is in the shape of 
a ring, provided with a number of teeth in the 
spaces between which the armature coils are 
placed. 

Armature, Unipolar A dynamo- 
electric machine armature whose polarity is 
not reversed during its rotation in the field 
of the machine. 

Armature, Ventilation of A pro- 
cess for insuring the free passage of air 
through the armature of a dynamo-electric 
machine in order to prevent overheating. 

Armor of Cable. — (See Cable, Armor of) 

Armored Cable. — (See Cable, Armored) 

Armored Conductor. — (See Conductor, 
Armored) 

Arms, Bridge or Balance The 

electric resistances, in the electric balance or 
bridge. (See Bridge, Electric.) 

M 




Zn C 
Fig. 24. Arms of Balance. 

An unknown resistance, such, for example, as 
D, Fig. 24, is measured by proportioning the 
known resistances, A, C and B, so that no current 
■flows through the galvanometer G, across the 
circuit or bridge M G N. 

Arms, Proportionate The two re- 
sistances or arms of an electric bridge whose 
relative or proportionate resistances only are 
required to be known in order to determine, 



in connection with a known resistance, the 
value of an unknown resistance placed in the 
remaining arm of the bridge. 

Thus is Fig. 24, A and B, are the proportionate 
arms. 

Arrangement or Device, Electromotive 

A term sometimes employed to rep- 
resent a dynamo-electric machine, voltaic cell 
or other electric source, by means of which 
electromotive force can be produced. 

Electric sources do not produce electric cur- 
rents, but differences of potential or electro- 
motive force. Electric sources are therefore very 
properly termed electromotive devices. 

Arrester, Lightning' A device by 

means of which the apparatus placed in any 
electric circuit is protected from the destruc- 
tive effects of a flash or bolt of lightning. 

In the phenomena of lateral induction and 
alternative path, we have seen the tendency of a 
disruptive discharge to take a short-cut across an 
intervening air space, rather than through a 
longer though better conducting path. Most 
lightning arresters are dependent for their opera- 
tion on this tendency to lateral discharge. (See 
Induction, Lateral. Path, Alternative.) 

A form of lightning arrester is shown in Fig. 25. 




Fig. 25. Comb Lightning- Arrester. 

The line wires, A and B, are connected by two 
metallic plates to C and D, respectively. 

The~e plates are provided with points, as shown, 
and placed near a third plate, connected to the 
ground by the wire G. Should a bolt strike the 
line, it is discharged to the earth through the 
wire G. 

Various forms are given to lightning arresters 
of this type. The projections are sometimes placed 
on the ground connected plate as well as on the 
plates connected to line wires. This form is 
sometimes called a comb arrester, or protector. 



Arr.] 



3-Z 



[Ast. 



Arrester, Lightning-, Comb —A 

term sometimes applied to a lightning ar- 
rester in which both the line and ground 
plates are furnished with a series of teeth, 
like those on a comb. (See Arrester, Light- 
ning^) 

Arrester, Lightning-, Counter-Electro- 
motive Force A lightning arrester, 

in which the passage of the discharge through 
the instruments to be protected is opposed 
by a counter-electromotive force, generated 
by induction on the passage of the discharge 
of the bolt to earth. 

The counter-electromotive force lightning ar- 
rester is an invention of Professor Elihu Thomson. 

It assumes a variety of forms. In the shape 
shown in Fig. 26, the line circuit of the dynamo, 




Fig. 26. Counter-Electromotive Force Lightning 
Arrester. 

D, has one end connected to ground, and the 
other end has two conducting paths to ground. 
One of these paths is through the ordinary comb- 
protector at P, by the ground plate E; this cir- 
cuit includes a few turns 
of wire C. The other 
path is through a corres- 
ponding coil C, either 
interior or exterior to C, 
so as to be within its in- 
ductive field. As will be 
seen from the figure, C, is 
er-Elec- connected through the 
machine to the ground. 
The induction coils C 
each 
other. 

Should a lightning flash or other static discharge 
pass through the circuit C, which is of compara- 
tively low self-induction, a counter-electromotive 
force is produced in the other coil C, which 
protects the line circuit. 




Light- 



tromotive Force 
ning Arrester. 

and C, are thoroughly insulated from 



In the form of lightning arrester shown irt 
Fig. 27, the coil in the path of the direct light- 
ning discharge is formed into an exterior mesh or 
net work surrounding the dynamo to be pro- 
tected. In this case, the coils of the dynamo act 
as the secondary coils in which the counter elec- 
tromotive force is set up. 

Arrester, Lightning, Transformer 

— A form of lightning arrester designed for 
the protection of transformers. 

The Thomson arrester for transformers oper- 
ates on the same principle as his arc-line pro- 
tector. In the latter the arc, when formed, 
is blown out by the action of the field of art 
electro-magnet. This arc is formed on curved 
metallic bows, one of which is connected to line 
and the other to earth. The arc is formed at the 
smallest interval between the bows, and is extin- 
guished by being driven by action of a magnetic 
field toward greatest interval. 

Arrester Plate of Lightning" Protector. — 

(See Plate, Arrester, of Lightning Pro- 
tector?) 
Arrester Plates. — (See Plates, Arrester?) 

Articulate Speech. — (See Speech, Articu- 
late?) 

Artificial Carbons. — (See Carbons, Arti- 
ficial^ 

Artificial Illumination. — (See Illumina- 
tion, Artificial) 

Artificial Line. — (See Line, Artificial) 

Artificial Magnet.— (See Magnet, Arti- 
ficial.) 

Asphyxia. — Suspended respiration, result- 
ing eventually in death, from non-aeration of 
the blood. 

In cases of insensibility by an electric shock a 
species of asphyxia is sometimes brought about. 
This is due, probably, to the failure of the nerves 
and muscles that carry on respiration. The exact 
manner in which death by electrical shock results 
is not known. (See Death, Electric.) 

Assyinmetrical Resistance. — (See Resist- 
ance, Assymmetrical.) 

Astatic. — Possessing no directive power. 

Usually applied to a magnetic or electro-mag- 
netic device which is free from any tendency to 
take a definite position on account of the earth's 
magnetism. 



Ast.] 



33 



[Ato. 



Astatic Circuit. — (See Circuit, Astatic) 
Astatic Couple.— See Couple, Astatic?) 
Astatic Galvanometer.— (See Galvanom- 
eter, Astatic.) 

Astatic Needle. — (See Needle, Astatic?) 

Astatic Pair. — (See Pair, Astatic) 

Astatic System. — (See System, Astatic) 

Astronomical Meridian. — (See Meridian, 
Astronomical) 

Asymptote of Curve. — (See Curve, Asy?np- 
tote of) 

Atmosphere, An A unit of gas or 

fluid pressure equal to about 1 5 pounds to the 
square inch. 

At the level of the sea the atmosphere exerts a 
pressure of about 15 pounds avoirdupois, or, 
more accurately, 14.73 pounds, on every square 
inch of the earth's surface. This value has there- 
fore been taken as a unit of fluid pressure. 

For more accurate measurements pounds to the 
square inch are employed. 

In the metric system of weights and measures 
an atmosphere is considered equal to 1,033 
grammes per square centimetre. 

Atmospheric pressures are measured by instru- 
ments called Manometers. (See Manometer.) 

Atmosphere, Residual The traces 

of air or other gas remaining in a space which 
has been exhausted of its gaseous contents 
by a pump or other means. 

It is next to impossible to remove all traces of 
air from a vessel by any known form of pump or 
other appliance. (See Vacuum, Absolute) 

Atmosphere, The The ocean of 

air which surrounds the earth. 

The atmosphere is, approximately, composed, 
by weight, of oxygen 23 parts, and nitrogen 77 
parts. Besides these there are from 4 to 6 parts 
in 10,000 of carbonic acid gas (or about a cubic 
inch of carbonic acid to a cubic foot of air), and 
varying proportions of the vapor of water. 

The oxygen, nitrogen and carbonic acid form 
the constant ingredients of the atmosphere, the 
vapor of water the variable ingredient. There 
are in most localities a number of other variable 
ingredients present as impurities. 

Atmospheric Electricity. — (See Electric- 
ity, Atmospheric) 



Atmospheric Electricity, Origin of 

— (See Electricity, At?nospkeric, Origin of) 

Atom. — The smallest quantity of elemen- 
tary or simple matter that can exist. 
An ultimate particle of matter. 

Atom means that which cannot be cut. It is 
generally believed that material atoms are abso- 
lutely unalterable in size, shape, weight and den- 
sity ; that they can neither be cut, scratched, 
flattened, nor distorted ; and that they are un- 
affected in size, density, or shape, by heat or 
cold, or by any known physical force. 

Although almost inconceivably small, atoms 
nevertheless possess a definite size and mass. 
According to Sir William Thomson, the smallest 
visible organic particle, 1-4000 of a millimetre in 
diameter, will contain about 30,000,000 atoms. 

Atom, Closed-Magnetic Circuit of 

(See Circuit, Closed-Magnetic, of Atom) 

Atom, Gramme — Such a number 

of grammes of any elementary substance as is 
numerically equal to the atomic weight of 
the substance. 

The gramme-atom of a substance represents 
the number of calories required to raise the tem- 
perature of one gramme of that substance through 
1 degree C. (See Heat, Atomic. Calorie) Thus, 
in the case of chlorine, whose atomic weight is 
35.5, its gramme-atom is 35.5 ; consequently 
35.5 small calories of heat would be required to 
raise one gramme- atom of chlorine through I 
degree C. 

Atom of Electricity. — (See Electricity, 
Atom of) 

Atom, Yortex A number of particles 

of the universal ether moving in the manner 
of a vortex ring. 

The theory of vortex atoms, so formed from 
vortex rings, was propounded by Sir William 
Thomson in order to explain how a readily mov- 
able substance, like the universal ether, could be 
made to possess the properties of a rigid solid. If 
it be granted that a vortex motion has once been 
imparted to the universal ether, Thomson shows 
that such rings would be indestructible. (See 
Matter, Thomson's Hypothesis of) 

Atomic Attraction. — (See Attraction, 
Ato?nic) 



Ato.] 



34 



[Att. 



Atomic Capacity. — (See Capacity, Atom- 
ic) 

Atomic Currents. — (See Currents, Atom- 
ic) 

Atomic Energy. — (See Energy, Atomic) 

Atomic Heat.— (See Heat, Atomic) 

Atomic or Molecular Induced Currents. 

— (See Currents, Induced, Molecular or 
Atomic) 

Atomic Weight. — (See Weight, Atomic) 

Atomicity. — The combining capacity of 
the atoms. 

The relative equivalence of the atoms or 
their atomic capacity. 

The elementary atoms do not always combine 
atom for atom. Some single atoms of certain 
elements will combine with two, three, four, or 
even more atoms of another element. 

The value of the atomic capacity of an atom is 
also called its quanlivalence or valency. 
Elements whose atomic capacity is — 

One, are -called Monads, or Univalent. 
Two, " Dyads, " Bivalent. 

Three, " Triads, " Trivalent. 

Four, " Tetrads, "Quadrivalent. 

Five, " Pentads, " Quinquivalent 

Six, " Hexads, " Sexivalent. 

Seven, " Heptads, " Septivalent. 

Atoiuization. — The act of obtaining liquids 
in a spray of finely divided particles. 

In most cases the term is not literally correct, 
as each of the smallest particles so obtained usu- 
ally consist of many thousands of atoms. 

Atomize. — To separate into a fine spray by 
means of an atomizer. (See Atomizer) 

Atomizer. — An apparatus for readily ob- 
taining a finely divided jet or spray of liquid. 

A jet of steam, or a blast of air, is driven across 
the open end of a tube that dips below the surface 
of the liquid to be atomized. The partial vacuum 
so formed draws up the liquid, which is then 
blown by the current into a fine spray. 

Attract. — To draw together. 
Attracted-Disc Electrometer. — (See Elec- 
trometer, Attracted-Disc) 

Attracting'. — Drawing together. 



Attraction. — Literally the act of drawing 
together. 

In science the name attraction is given to a 
series of unknown causes which effect, or are as- 
sumed to effect, the drawing together of atoms, 
molecules or masses. 

Attraction and repulsion underlie nearly all 
natural phenomena. While their effects are well 
known, it is doubtful if anything is definitely 
known of their true causes. 

Since attraction, pure and simple, necessitates 
the belief in action at a distance, an action which 
is now generally discredited, we must, strictly 
speaking, regard the term attraction as being but 
a convenient substitution of the effect for the 
cause. 

It would appear much more reasonable to re- 
gard the effects of attraction as produced by a 
true push exerted from the outside of the bodies. 
According to this notion, two masses of matter 
undergoing attraction are pushed together rather 
than drawn or attracted together. 

It has been suggested that gravitation may per- 
haps be an effect of a longitudinal motion or vibra- 
tory thrust in the universal ether. If this is the 
case, and the ether is sensibly incompressible, the 
velocity of gravitation, it would appear, should be 
almost infinite. 

Attraction, Atomic The attraction 

which causes the atoms to combine. (See 
Affinity, Chemical) 

In the opinion of Lodge, atomic attraction is 
the result of the attraction of dissimilar charges of 
electricity possessed by all atoms, which are capa- 
ble of uniting or entering into chemical combi- 
nation. (See Electricity, Atom of) 

Attraction, Capillary The molec- 
ular attractions that are concerned in 
capillary phenomena. (See Capillarity) 

Attraction, Electro-Dynamic — The 

mutual attraction of electric currents, or of 
conductors through which electric currents 
are passing. (See Dynamics, Electro) 

Attraction, Electro-Magnetic The 

mutual attraction of the unlike poles of 
electro-magnets. (See Magnet, Electro.) 

Attraction, Electrostatic — The 

mutual attraction exerted between unlike 
electric charges, or bodies possessing unlike 



Att.] 



35 



[Aur, 



For example, the pith ball supported on an in- 
sulated string is attracted, as shown at A, Fig. 28, 





Fig. 28. E 7 ectrostatic 
Attraction. 



Fig. 2Q. Electrostatic 
Repulsion. 



by a bit of sulphur which has been briskly rubbed 
by a piece of silk. As soon, however, as the ball 
touches the sulphur and receives a charge, it is 
repelled, as shown at B, Fig. 29. 

These attractions ai d repulsions are due to the 
effects of electrostatic induction. (See Induction, 
Electrostatic. ) 

— The mutual 



Attraction, Magnetic — 

attraction exerted between unlike magnet 
pales. 

Magnetic attractions and repulsions are best 
shown by means of the magnetic needle N S, 
Fig. 30. The N. pole of an approached magnet 




Magnetic Attraction. 



attracts the S. pole of the needle but repels the 
N. pole. 

The laws of magnetic attraction and repulsion 
may be stated as follows, viz.: 

(1.) Magnet poles of the same name repel each 
other; thus, a north pole repels another north 
pole, a south pole repels another south pole. 




(2.) Magnet poles of unlike names attract each 
other; thus a north pole s 

attracts a south pole, or 
a south pole attracts a N; 
north pole. 

A small bar magnet, Fig. 31. Floating 
N S, Fig. 31, laid on the Magnet. 

top of a light vessel floating on the surface of a 
liquid, may be readily employed to illustrate the 
laws of magnetic attraction and repulsion. 

Attraction, Mass The mutual at- 
traction exerted between masses of matter. 
(See Gravitatio?i.) 

Attraction, Molar A term some- 
times employed for mass attraction. 

Gravitation is an example of mass attraction, 
where the mass of the earth attracts the mass of 
some body placed near it. (See Gravitation.) 

Attraction, Molecular The mutual 

attraction exerted between neighboring 
molecules. 

The attraction of like molecules, or those of the 
same kind of matter, is called Cohesion ; that of 
unlike molecules, Adhesion. 

The tensile strength of iron or steel is due to 
the cohesion of its molecules. Paint adheres to 
wood, or ink to paper, by cohesion or the attrac- 
tion between the unlike molecules. 

Attraction of Gravitation. — A term gen- 
erally applied to the mutual attraction be- 
tween masses. (See Gravitation.) 

Attractions and Repulsions of Currents. 
— (See Currents, Attractio7is and Repulsions 
of.) 

Audiplione. — A thin plate of hard rubber 
held in contact with the teeth, and maintained 
at a certain tension by strings attached to one 
of its edges, for the purpose of aiding the 
hearing. 

The plate is so held that the sound-waves from 
a speaker's voice impinge directly against its flat 
surface. It operates by means of some of the 
waves being transmitted to the ear directly 
through the bones of the head. 

The audiphone is sometimes called a denti- 
phona. 

Aural Electrode. — (See Electrode, Aural) 

Aurora Australis. — The Southern Light. 

A name given to an appearance in the south- 



Aur.] 



36 



[Aut. 



ern heavens similar to that of the Aurora 
Borealis. (See Aurora Borealis) 

Aurora Borealis. — The Northern Light. 

Luminous sheets, columns, arches, or pillars 
of pale, flashing light, generally of a red color, 
seen in the northern heavens. 

The auroral light assumes a great variety of ap- 
pearances, to which the terms auroral arch, bands, 
cor once, cur tarns and streatners are applied. 

The exact cause of the aurora is not as yet 
known. It would appear, however, beyond any 
reasonable doubt, that the auroral flashes are due 
to the passage of electrical discharges through the 
upper, and therefore rarer, regions of the atmos- 
phere. The intermittent flashes of light are prob- 
ably due" to the discharges being influenced by the 
earth's magnetism. 

Auroras are frequently accompanied by mag- 
netic storms. (See Storm, Magnetic.) 

The occurrence of auroras is nearly always 
simultaneous with that of an unusual number of 
sun spots. Auroras are therefore probably con- 
nected with outbursts of the solar energy. (See 
Spots, Sun.) 

The auroral light examined by the spectroscope 
gives a spectrum characteristic of luminous gaseous 
matter, i. e., contains a few bright lines; but, ac- 
cording to S. P. Thompson, this spectrum is pro- 
duced by matter that is not referable with cer- 
tainty to that of any known substance. 

Whatever may be the exact cause of auroras, 
their appearance is almost exactly reproduced by 
the passage of electric discharges through vacua. 

Aurora Polaris. — A general term some- 
times applied to aurora in the neighborhood 
of either pole, or in either the northern or 
the southern hemisphere. 
Auroral Arch. — (See Arch, Auroral.) 
Auroral Bauds. — (See Bands, Auroral?) 
Auroral Corona). — (See Corona, Au- 
roral?) 

Auroral Curtain. — (See Curtain, Au- 
roral.) 

Auroral Flashes. — (See Flashes, Auroral) 
Auroral Light. — (See Light, Auroral) 
Auroral Storm. — (See Storm, Auroral) 
Auroral Streamer. — (See Streamer, Au- 
roral) 
Auroras and Magnetic Storms, Peri- 



-Observed coincidences be- 



odicity of — 

tween the occurrence of auroras, magnetic 
storms, and sun-spots. 

The occurrence of auroras, or magnetic storms, 
at periods of about eleven years apart, corre- 
sponds to the well-known eleven-year sun-spot 
period. 

The period also agrees with a variation in the 
magnetic declination of any place, which, accord- 
ing to Sabine, occurs once in every eleven years. 

Austral Magnetic Pole. — (See Pole, Mag- 
netic, Austral) 

Autographic Telegraphy. — (See Teleg- 
raphy, Autographic) 

Automatic Annunciator Drop. — (See 
Drop, Annunciator, Automatic) 

Automatic Bell. — v See Bell, Automatic 
Electric) 

Automatic Contact Breaker. — (See Co7t- 
tact Breaker, Automatic) 

Automatic Cut-Out. — {See Cut-Out, Au- 
tomatic) 

Automatic Cut-Out for Multiple-Connect- 
ed Electro-Receptive Devices. — (See Cut- 
Out, Automatic, for Multiple-Connected 
Electro-Receptive Devices) 

Automatic Cut-Out for Series-Connected 
Electro-Receptive Devices. — (See Cut-Out, 
Automatic , for Series-Connected Electro-Re- 
ceptive Devices) 

Automatic Drop. — (See Drop, Auto- 
matic) 

Automatic Electric Burner. — [See Burn- 
er, Autojnatic Electric) 

Automatic Electric Safety System for 
Railroads. — (See Railroads, Automatic Elec- 
tric Safety System for) 

Automatic Fire-Alarm. — (See Alarjji, 
Fire, Automatic) 

Automatic Gas Cut-Oif. — (See Cut-Off, 
Automatic Gas) 

Automatic Indicator. — (See Indicator, 
Autotnatic) 

Automatic Make-and-Break. — (See Make- 
and-Break, Automatic) . 

Automatic Oiler. — (See Oiler, Automatic) 



Aut. 



37 



[B. A. U. 



Automatic Paper- Winder. — (See Winder, 
Telegraphic Paper.) 

Automatic Regulation. — See Regulation, 
Automatic?) 

Automatic Regulator. — (See Regulator, 
Automatic) 

Automatic Search-Light. — (See Light, 
Search, Automatic) 

Automatic Switch for Incandescent Elec- 
tric Lamp. — (See Switch, Automatic, for 
l7icandescent Electric Lamp.) 

Automatic Telegraphy. — (See Teleg- 
raphy, Automatic) 

Automatic Telephone Switch. — (See 
Switch, Telephone, Automatic) 

Automatic Time Cut-Outs.— (See Cut- 
Out, Automatic Time) 

Automatic Variable Resistance. — (See 
Resistance, Variable, Automatic) 

Automatically Regulable. — (See Regula- 
ble, Automatically) 

Automobile Torpedo. — (See Torpedo, Au- 
tomobile) 

Average or Mean Electromotive Force. — 
(See Force, Electromotive, Average, or 
Mean) 

Axes of Co-ordinates. — (See Co-ordinates, 
Axes of) 

Axial Magnet. — (See Magnet, Axial.) 

Axis, Magnetic The line around 

which a magnetic needle, free to move, but 
which has come to rest in a magnetic field, 
can be turned without changing the set or 
direction in which it has come to rest. 

Axis, Magnetic, of a Straight Needle 

— A straight line drawn through the magnet, 
joining its poles. 



The magnetic axis of a straight needle may be 
regarded as a straight line passing through the 
poles of the needle and its point of support. 

The magnetic axis may not correspond with 
the geometric axis of the 
needle. This leads to 
an error in reading the 
true direction in which 
the needle is pointing, 
which must be cor- 
rected. Thus, the nee- 
dle N S, Fig. 32, points 
to 31 degrees on the 
scale. In reality, if the 
magnetic axis of the 
needle lies in the line 
N' S', the true deflec- 
tion of the needle is only 
28 degrees. 




Fig. 32. Magnetic 
Axis. 



Axis of Abscissas. — (See Abscissas, Axis 
of) 

Axis of Ordinates. — (See Ordi?iates, Axis 
of) 

Azimuth. — In astronomy, the angular dis- 
tance between an azimuth circle and the 
meridian. 

The azimuth of a heavenly body in the North- 
ern Hemisphere is measured on the arc of the 
horizon intercepted between the north point of 
the horizon and the point where the great circle 
that passes through the heavenly body cuts the 
horizon. 

Azimuth Circle.— (See Circle, Azimuth?) 

Azimuth Compass. — (See Compass, Azi- 
muth) 



Azimuth, Magnetic 



-The arc inter- 



cepted on the horizon between the magnetic 
meridian and a great circle passing through 
the observed body. 



B. — A contraction used in mathematical 
writings for the internal magnetization, or the 
magnetic induction, or the number of lines of 
force per square centimetre in the magnetized 
material. 

This contraction for internal magnetization is, 



in most mathematical treatises, printed in bold- 
faced type. 

B. A. Ohm.— (See Ohm, B. A) 

B. A. IT. — A contraction sometimes em- 
ployed for the British Association unit or ohm. 



B. W. G.] 



38 



[Bal. 



B. W. G. — A contraction for Birmingham 
wire gauge. (See Gauge, Biwningham 
Wire) 

A contraction sometimes used for the new 
British wire gauge. 

Back Electromotive Force. — (See Force, 
Electromotive, Back) 

Back-Stroke of Lightning. — (See Light- 
ning, Back-Stroke of.) 

Bain's Chemical Recorder.— (See Re- 
corder, Chei?iical, Bains.) 

Bain's Printing' Solution. — (See Solution, 
Bain's Printing.) 

Balance Arms. — (See Arms, Bridge or 
Balance) 

Balance, Bi-fllar Suspension An 

instrument similar in construction to Cou- 
lomb's torsion balance, but in which the 
needle is hung by two separate fibres instead 
of by a single one. (See Bala7ice, Coulomb's 
Torsion. Suspension, Bi-filar) 

Balance, Centi-Ampere — 



A standard Thomson centi-ampere balance 
is shown in Fig. 33. In measuring a current, 



— An am- 
meter in the form of a balance, whose scale is 
graduated to give direct readings in centi- 
amperes. 

Ampere balances giving readings in various 
decimals or multiples of amperes have been de- 
vised by Sir William Thomson. The strength of 
current passing is determined by the action on a 
movable ring or coil, placed between two fixed 
rings or coils. 

The movable ring is in a horizontal plane 
nearly midway between the two fixed rings. 
The fixed rings are traversed by the current 
in opposite directions, so that one attracts 
and the other repels the movable ring. Tne 
movable iing is attached to one end of a horizon- 
tal balance arm, and a similar movable ring, also 
provided with attracting and repelling fixed rings, 
is attached to the opposite end of the balance arm. 
In order to avoid disturbance of horizontal com- 
ponents of terre:>trial, or of local magnetic force, 
the current is sent in the same direction through 
the two movable rings. The balancing is effected 
by means of a weight, sliding on a nearly hori- 
zontal arm attached to the balance. A counter- 
poise weight is used in connection with the sliding 
weight. 




Fig. 33. Centi-Ampere Balance. 

the weight is moved along the scale untd the 
balance comes to rest. 

Balance, Composite —A balance 

form of ammeter devised by Sir William Thom- 
son, which can be used for an ampere-meter, a 
watt-meter, or a volt-meter, according to the 
manner in which its sets of fine and coarse 
wire coils are connected. (See Balance, 
Centi-Ampere) 

Balance, Coulomb's Torsion An 

apparatus to measure the force of electric or 
magnetic repulsion between two similarly 
charged bodies, or between two similar mag- 
net poles, by opposing to such force the tor- 
sion of a thin wire. 

The two forces balance each other ; hence the 
origin of the name. 




Fig- 34. Coulomb's Torsion Balance. 

Fig. 34 represents a Coulomb torsion bal- 
ance, adapted to the measurement of the force 



Bal.] 



39 



[Bal. 



of electrostatic repulsion. A delicate needle of 
shellac, having a small gilded pith ball at one of 
its ends, is suspended by a fine metallic wire. A 
proof-plane, B, is touched to the electrified surface 
whose charge is to be measured, and is then 
placed as shown in the figure. (See Plane, Proof.) 
There is a momentary attraction of the needle, 
and then a repulsion, which causes the needle to 
be moved a certain distance from the ball on the 
proof-plane. This distance is measured in degrees 
on a graduated circle a a, marked on the instru- 
ment. The force of the repulsion is calculated by 
determining the amount of torsion required to 
move the needle a certain distance toward the 
ball of the electrified proof-plane. 

This torsion is obtained by the movement of the 
torsion head D, the amount of which motion is 
measured on a graduated circle at D. The 
measurement is based on the fact that the force re- 
quired to twist a wire is proportional to the angle 
of torsion. 

Balance, Deci- Ampere An ammeter 

in the form of a balance, whose scale is 
graduated to give direct readings in deci- 
amperes. (See Balance, Centi-Ampere^) 

Balance, Deka-Ampere — An am- 
meter in the form of a balance, whose scale is 
graduated to give direct readings in deka- 
amperes. (See Balance, Centi-Ainpere}} 

Balance, Electric A term fre- 
quently used for Wheatstone's electric bridge. 
(See Bridge, Electric^ 

The electric bridge is sometimes called a balance 
because, when in use in measuring resistances, 
one resistance or set of resistances balances an- 
other resistance or set of resistances. 

Balance, Hekto-Ampere An am- 
meter in the form of a balance, whose scale 
is graduated to give direct readings in hekto- 
amperes. (See Balance, Centi- Ampere.) 

Balance Indicator.— (See Indicator, Bal- 
ance.) 

Balance, Induction, Hughes' 

An apparatus for the detection of the presence 
of a metallic or conducting substance by the 
aid of induced electric currents. 

Hughes' induction balance is shown in Fig. 35. 

A, B, C and D are bobbins, wound with about 
300 feet of No. 32 copper wire. The coils are 



connected as shown, A and B, in the circuit of a 
battery, and C and D, in the circuit of a telephone. 
The coils, A and B, and C and D, are placed at 




Fig- 35' Hughes' Induction Balance. 

such a distance apart as to prevent any mutual 
induction occurring between them. The coils 
are so joined that the direction of the induction 
of A, on C, is opposite to that of B, on D. 

The coils, A and B, then act as primaries, and C 
and D, as secondaries. In the battery circuit is an 
interrupter I, which is caused to continually make 
and break the circuit. 

The coils are so adjusted that the opposing 
secondary coils produce but little noise to one 
listening at the telephone. This can readily be 
done by the adjusting of a single pair of coils. 

If a single com or mass of metal be introduced 
between either A and C, or B and D, or even 
above one of the coils, as at d, the balance 
will be disturbed, since some of the induction is 
now expended in producing electric currents in 
the interposed metal, and a sound will therefore 
be heard in the telephone. But if precisely similar 
metals are placed in similar positions, between A 
and C, and B and D, no sound is heard in the 
telephone, since the inductive effects due to the 
two metals are the same. 

The slightest difference, however, either in 
composition, size or position, destroys the balance, 
and causes a sound to be heard in the telephone. 

A spurious coin is thus readily detected when 
compared with a genuine coin. 

A somewhat similar instrument has been em- 
ployed to detect and locate a bullet or other for- 
eign metallic substance in the human body. 

In order to determine the amount of the dis- 
turbance, an instrument called a sonometer is 
used (See Sonometer, Hughes' 1 ), in which a single 
secondary coil, placed in the circuit of a telephone, 
slides on a graduated bar between two fixed 
primary coils, so wound as to exert equal and op- 
posite inductions on the secondary. When, there- 
fore, the secondary is exactly in the middle of the 



Bal.] 

graduated bar, and consequently exactly midway 
between the two fixed primary coils, no sounds are 
heard in the telephone, but when moved to one 
side or the other the sounds are heard. Switches 
are so arranged that the telephone can be readily 
switched from the induction balance to the tele- 
phone, or vice versa. When, therefore, a metallic 
disc is placed in one of the coils of the induction 
balance, and a noise is heard in the telephone, 
the coil of the sonometer is shifted so that the 
noise heard in this telephone is judged by the 
ear to be equal, and the comparison can then be 
made by means of simple calculations. 

The following table gives, in arbitrary values, 
the results of various experiments as to the sensi- 
tiveness in this respect of discs of different 
metals, of various sizes and shapes : 

Silver, chemically pure 125 

Gold .' 117 

Silver, commercial 115 

Aluminium 112 

Copper 100 

Zinc 80 

Bronze 75 

Tin 74 

Iron, ordinary 53 

German silver 50 

Iron, pure 40 

Copper, alloyed 40 

Lead 58 

Antimony 35 

Bismuth 10 

Zinc, alloyed 6 

Carbon 2 

— {Fleming.) 

An inspection of this table shows that the values 
found for different metals do not correspond with 
their electric conducting power, although, roughly 
speaking, the best conductors stand at the top of 
the table, and the worst at the bottom. The 
effects appear to be dependent for their action on 
the phenomena of magnetic screening, for — 

(1.) If slots are cut in the middle of the plate 
its disturbing action is either removed or very 
much decreased. 

(2.) If a flat coil of copper wire rep 1 aces a disc 

of metal no effect is produced on the induction 

balance when its ends are open, but when closed 

, the coil acts just like a disc, or continuous plate 

*of metal. 

(3.) The difference between various metals in- 



40 [Bal. 

serted as discs in the induction balance is less at 
high speeds of reversal than at low speeds. 

Balance, Kilo-Ampere — An am- 
meter in the form of a balance, whose scale is 
graduated to give direct readings in kilo-am- 
peres. (See Balance, Centi- Ampere?) 

Balance of Induction in Cable. — (See 
Induction, Balance of, in Cable?) 

Balance, Plating- An automatic 

device for disconnecting the current from 
the article to be plated, as soon as a certain 
increase in weight has been obtained. 

The objects to be plated are suspended at one 
end of a balance, and when a certain increase in 
weight has been gained, the balance tips and 
breaks the circuit. Edison's electric meter is 
based on this principle. 

Balance, Thermic, or Bolometer. — An 

apparatus constructed on the principle of the 
differential galvanometer, devised by Professor 
Langley for determining small differences of 
temperature. (See Galva?iometer, Differen- 
tial) 

A coil composed of two separately insulated 
wires, wound together, is suspended in a mag- 
netic field, and has a current sent through it. 
Under normal conditions, this current separates 
into two equal parts, and runs through the wires 
in opposite directions. It therefore produces no 
sensible field, and suffers no deflection by the field 
in which it is suspended. 

Any local application of heat producing a dif- 
ference in temperature in these coils, causing a 
difference in resistance, prevents this equality. A 
field is therefore produced in the suspended coil, 
which, though extremely small, is rendered meas- 
urab'e by means of the powerful field produced 
in the coil, within which the double coil is sus- 
pended. 

Differences of temperature as small as one- 
fourteen thousandth of a degree Fahrenheit are 
detected by the instrument. 

Balance, Wheatstone's Electric A 

name often given to the electric bridge or 
balance. (See Bridge, Electric) 

Balanced-Metallic Circuit. — (See Circuit, 
Balanced-Metallic) 

Balanced Resistances. — (See Resistances, 
Balanced) 



Bal. 



41 



[Bar. 



Balata. — An insulating material. 
Balata, when prepared for use as an insulating 
material, is somewhat like gutta-percha. 

Ball, Electric Time A ball, sup- 
ported in a prominent position on a tall pole, 
and caused to fall at the exact hour of noon, 
or at any other predetermined time, for the 
purpose of thus giving correct time to an 
entire neighborhood. 

The release of the ball is effected by the closing 
of an electric circuit, either automatically, or 
through the agency of an observer. 

Ball, Fire A term sometimes ap- 
plied to globular lightning. (See Lightning, 
Globular.) 

Ball Lightning. — (See Lightning, Ball.) 

Ballistic Curve.— (See Curve, Ballistic?) 

Ballistic Galvanometer. — (See Galva- 
nometer, Ballistic.) 

Balloon, Electric A balloon, or 

air ship, provided with electric power so as 
to be able to be steered or moved against the 
direction of the wind. 

Electric balloons have been moved against the 
wind and steered with a certain amount of success, 
by the use of electric motors driven by storage 
batteries. All thr.t is needed to make aerial navi- 
gation a commercial success is the ability to ob- 
tain great power with a small weight. The storage 
battery does this to a limited extent. 

Bearing in mind the high efficiency of the elec- 
tric motor, it would appear that the problem of 
successful aerial navigation will be solved when 
the discovery is made of means for directly con- 
verting the chemical potential energy of coal into 
electrical energy. 

Balloon Signaling for Military Pur- 
poses. — (See Signaling, Balloo7i, for Mil- 
itary Purposes?) 

Balls, Pith Two balls of pith, sus- 
pended by conducting threads of cotton to 
insulated conductors, employed to show the 
electrification of the same by their mutual 
repulsion. 

The pith balls connected with the insulated 
cylinder A B, Fig. 36, not only show the electri- 
fication of the cylinder, but serve also to roughly 



indicate the peculiarities of distribution of the 
charge thereon. 




Fig. j 6. Fit A Ball Cylinder. 



Bands, Auroral 



-Approximately 



parallel streaks of light sometimes seen 
during the prevalence of the aurora. (See 
Aurora Boreal is.) 

Bank of Lamps.— (See Lamps, Bank of.) 

Banked Battery. — (See Battery, Banked.) 

Bar, Detorsion A bar placed in a 

magnetic instrument called a declinometer for 
the purpose of removing the torsion of the 
suspending thread of the magnet. 

The detorsion _,ar of the declinometer is gen- 
erally made of gun metal of the same weight as 
that of the suspended magnet. A small magnet 
is placed in a rectangular aperture in the middle 
of the bar. 

Bar Electro-Magnet.— (See Magnet, 
Electro, Bar.) 

Barad. — A unit of pressure proposed by 
the British Association. 

One barad equals one dyne per square centi- 
metre. 

Barometer. — An apparatus for measuring 
the pressure or weight of the atmosphere. 

Barometric Column. — (See Column, Baro- 
metric?) 

Bars, Bus Omnibus bars. (See 

Bars, Omnibus?) 

Bars, Krizik's Cores of various 

shapes, provided for solenoids, in which the 
distribution of the metal in the bar is so pro- 
portioned as to insure as nearly as possible a 
uniform attraction or pull while in different 
positions in the solenoid. 



Bar.] 

Krizik's bars of various shapes are shown in 
Fig. 37. It will be observed that in all cases the 



42 




Fig. 37- Krizik's Bars. 
mass of metal is greater toward the middle of 
the core than near the ends. 

When a core of uniform diameter is drawn into 
a solenoid, the attraction or pull is not uniform in 
strength for different positions of the bar. When 
the bar is just entering the solenoid, the pull is 
strongest ; as soon as the end passes the middle of 
the core the attraction decreases, until, when the 
centres of the bar and core coincide, the motion 
ceases, since both ends of the solenoid attract 
equally in opposite directions. By proportioning 
the bars, as shown in the figure, a fairly uniform 
pull for a considerable length may be obtained. 

Bars, Negative-Omnibus — The 

bus-bars that are connected with the negative 
terminal of the dynamos. (See Bars, Omni- 
bus.) 

Bars, Neutral-Omnibus The bus- 
bars that are connected with the neutral 
dynamo terminal in a three-wire system of 
distribution. 



Bars, Omnibus 



-Heavy bars of con- 



ducting material connected directly to the 
poles of dynamo-electric machines, in electric 
incandescent light or electric railway installa- 
tions, and therefore receiving the entire current 
produced by the machine. 

Main conductors common to two or more 
dynamos in an electrical generating plant. 

The terms bus and omnibus bars refer to the 
fact that the entire or whole current is carried by 
them. 

Bars, Positive-Omnibus The bus- 
bars that are connected with the positive 
terminal of the dynamos. 

Bath, Bi-polar An electro-thera- 
peutic bath, the current applied to which 
enters at one part of the tub, and leaves at 
another part. 



[Bat. 

The electrodes for the bi-polar bath consist of 
suitably shaped copper plates, generally called 
shovel electrodes. 

Bath, Copper An electrolytic bath 

containing a readily electrolyzable solution 
of a copper salt, and a copper plate acting as 
the anode, and placed in the liquid near the 
object to be electro-plated, which forms the 
kathode. (See Plating, Electro?) 

The sulphate, the cyanide and the acetate of cop- 
per are used for copper baths. The use of the sul- 
phate is objectionable. The cyanide is expensive. 
The acetate is therefore very generally employed. 
Wahl gives the following formula for a copper 
bath, viz. : 

Water 1,000 parts. 

Acetate of copper, crystal- 
lized 20 " 

Carbonate of soda 20 " 

Bisulphite of soda 20 " 

Cyanide of potassium (pure) 20 " 

Bath, Electro-Plating- Tanks con- 
taining metallic solutions in which articles 
are placed so as to be electro-plated. (See 
Plating, Electro?) 

Strictly speaking a plating bath includes not 
only the vessel and its metallic solution, but abo 
the metallic plate acting as the anode and the 
article to be plated forming the kathode. 

Bath, Electro-Therapeutic A bath 

furnished with suitable electrodes and used 
in the application of electricity to curative 
purposes. 

Such baths should be used only under the advice 
of a regular physician. 

Bath, Gold An electrolytic bath 

containing a readily electrolyzable solution of 
a gold salt and a gold plate acting as the 
anode, and placed in the liquid opposite the 
object to be plated, which forms the kathode. 
(See Plating, Electro?) 

Electro gilding may beaccomp'ished either with 
or without the aid of heat. Hot gilding appears 
to give a smoother and cleaner deposit. 

The following is a fairly good solution for a 
gold bath: 

Water i,coo parts. 

Cyanide of potassium, pure. . 20 " 

Gold 10 " 

—{Wahl.) 



Bat.] 



43 



[Bat. 



The gold is first converted into neutral chloride 
by dissolving it in 25 parts of pure hydrochloric 
acid to which 12.5 parts of pure nitric acid has 
been added. When the gold is completely dis- 
solved, the liquid is heated until of a dark red 
color, in order to expel any excess of acid. 

Bath, Head, Electric A variety 

of electric breeze, applied therapeutically to 
the head of the patient. 

The patient is placed on an insulating stool and 
connected with one pole of an electrostatic induc- 
tion machine, the other pole of which is con- 
nected to a circle of insulated points suspended 
over the head. 

Bath, Hydro-Electric A bath in 

which electro-therapeutic treatment is given 
by applying one electrode to the metallic lining 
of the tub, and the other electrode to the body 
of the bather. 

Bath, Multfpolar-Electric — An 

electro-therapeutic bath, in which more than 
two electrodes are employed. 

It is not clear that the multipolar- electric bath 
possesses any decided advantages over the bi-polar 
bath. 

Bath, Nickel An electrolytic bath 

containing a readily electrolyzable salt of 
nickel, a plate of nickel acting as the anode 
of a battery and placed in the liquid near the 
object to be coated, which forms the kathode. 
(See Plating, Electro) 

The double sulphate of nickel and ammonium 
(from 5 to 8 parts dissolved in 100 parts of water) 
is used for the bath. Some prefer to add 
sulphate of ammonium and citric acid to the above 
solution. 

Bath, Shower, Electric A shower 

bath in which the falling drops carry electric 
charges to the patient subjected thereto. 

The water is rendered slightly alkaline. One 
pole is immersed in the alkaline water and the 
other connected to a metallic stool on which the 
patient is placed. 

Bath, Silver An electrolytic bath 

containing a readily electrolyzable salt of 
silver and a plate of silver acting as the 
anode of an electric source and placed in the 
liquid near the object to be coated, which 
forms the kathode. \See bating, Electro) 



The double cyanide of silver and potassium 
is the salt usually emplo\ed in the silver bath. 

The following bath is recommended by Rose- 
leur: 

Water 1,000 parts. 

Cyanide of potassium (pure) 50 " 
Pure silver 25 " 

The silver (granulated) is treated with pure nitric 
acid (43 degrees Beaume) and converted into 
nitrate of silver. The solution is then heated to 
dryness and subsequently fused. The fused nitrate 
so obtained is dissolved in fifteen times its weight 
of distilled water and treated with a solution of 
cyanide of potassium (10 per cent, of the cyanide), 
by means of which silver cyanide is thrown down 
as a precipitate. This precipitate is then sepa- 
rated and washed. It is added to the I, coo parts 
of water, dissolved, and the cyanide of potassium 
afterward added, thus forming the double cyan- 
ide required for the bath. 

Bath, Stripping" A bath for remov- 
ing an electro-plating of gold, silver, or other 
metal, either by simple dipping or by electric 
action. 

Bath, rngilding" A stripping bath 

suitable for the removal of a coating of gold. 
(See Bath, Stripping) 

Bath, Unipolar-Electric An electro- 
therapeutic bath, the water of which forms 
one of the electrodes of the source, and the 
other electrode is attached to a metallic rod 
fixed at a convenient height above the tub. 

The bath tub is formed of non-conducting sub- 
stances. The terminals of the electrode con- 
nected with the water terminate in metal plates 
located at suitable points in the tub. The cur- 
rent is applied by the patient making and break- 
ing contact at the vertical metal rod with his 
hands. 

The unipolar-electric bath is employed instead 
of local galvanization where it is desired to limit 
the application to especial organs or particular 
parts of the body. In general galvanization the 
patient is placed on an electrode of large sur- 
face, formed of a large sponge- covered metallic 
plate, on which he sits or rests. This electrode is 
connected with the kathode of the battery. The 
anode is connected with a large sponge electrode, 
which is moved regularly over the body of the 
patient; sometimes the moistened hand of the 
operator is used in place of the sponge electrode. 



Bat.] 



u 



[Bat. 



Bath, Unsilvering" 



-A stripping bath 



suitable for the removal of a coating of silver. 
(See Bath, Strippi?ig^) 

Bathometer. — An instrument invented by 
Siemens for obtaining deep-sea soundings 
without the use of a sounding line. 

The bathometer depends for its operation on 
the varied attraction of the earth for a suspended 
weight in parts of the ocean differing in depth. 
As the vessel passes over deep portions of the 
ocean, the solid land of the bottom, being further 
from the ship, exerts a smaller attraction than it 
would in shallow parts, where it is nearer; for, 
although in the deep parts of the ocean the water 
lies between the ship and the bottom, the smaller 
density of the water as compared with the land 
causes it to exert a smaller attraction than in the 
shallower parts, where the bottom is nearer the 
ship. The varying attraction of the earth is 
caused to act on a mercury column, the reading 
of which is effected by means of an electric con- 
tact. 

Battery, Banked — A term some- 
times applied to a battery from which a num- 
ber of separate circuits are supplied with cur- 
rents. 

The term banked -battery is sometimes ap- 
plied to a multiple-arc connected battery. 

Battery, Cautery — A term some- 
times employed in electro-therapeutics, for a 
multiple connected voltaic battery adapted for 
producing electric incandescence for cautery 
effects. 

Battery, Closed-Circuit A voltaic 

battery which may be kept constantly on 
closed-circuit without serious polarization. 

The gravity battery is a closed circuit battery. 
As employed for use on most telegraph lines, it is 
maintained on a closed circuit. When an operator 
wishes to use the line he opens his switch, thus 
breaking the circuit and calling his correspondent. 
Such batteries should not polarize. (See Cell, 
Voltaic, Polarization of. ) 

Battery, Connection of, for Quantity 

— A term, now generally in disuse, formerly 
.employed to indicate the grouping of voltaic 
cells, now known as parallel or multiple. 

The arrangement or coupling of a number of 
voltaic ells in multiple reduces the internal resist- 



ance of the battery, and thus permits a greater 
current, or quantity, of electricity to pass ; hence 
the origin of the term. 

Battery, Dynamo The combina- 
tion or coupling together of several separate 
dynarno-electric machines so as to act as a 
single electric source. 

The dynamos may be connected to the leads 
either in series, in multiple, in multiple-series or 
in series-multiple. 

Battery, Dynamo, Electric Machine — — 

— A dynamo battery. (See Battery, Dy- 
namo.) 

Battery, Electric A general term 

applied to the combination, as a single source, 
of a number of separate electric sources. 

The separate sources may be coupled either in 
series, in multiple, in multiple-series, or in -series- 
multiple. ( See Circuits, Varieties of.) 

The term battery is sometimes incorrectly ap- 
plied to a single voltaic couple or cell. 

Battery, Floating", De la Eire's A 

floating voltaic cell, the terminals of which are 
connected with a coil of insulated wire, em- 
ployed to show the attractions and repul- 
sions between magnets and movable electric 
circuits. 

The cell, shown in, Fig. 38, consists of a vol- 




- |i 

ll'l ill' 



Fig. 3&- Floating Cell. 

taic couple of zinc and copper, the terminals of 
which are connected to the circular coil of insu- 
lated wire, as shown, and the whole floated by 
means of a cork, in a vessel containing dilute sul- 
phuric acid. 

When the current flows through the coil in the 
direction shown by the arrows, the approach of 
the N-seeking pole of a magnet will cause the 
cell to be attracted or to move towards the mag- 
net pole, since the south face or end of the cod is 
nearer the north pole of the magnet. If the other 



Bat.] 



45 



[Bat. 



end were nearer, repulsion would occur, the cell 
turning round until the south face is nearer the 
magnet, when attraction occurs. 

This is, strictly speaking, a floating cell, and 
not a battery. (See. Battery, Voltaic.) 

Battery, Galvanic Two or more 

separate voltaic cells so arranged as to form 
a single source. 

This is more correctly called a Voltaic Battery. 
(See Battery , Voltaic.) 

Battery, Gas A battery in which 

the voltaic elements are gases as distinguished 
from solids. 

The electrodes of a gas battery generally con- 
sist of plates of platinum, or other solid substance 
which possesses the power of occluding oxygen 
and hydrogen. The lower parts of these plates 
dip into dilute sulphuric acid, and the upper parts 
are respectively surrounded by oxygen and hydro- 
gen gas derived from the electrolytic decompo- 
sition of the dilute acid. 

A gas battery consisting of plates of platinum 
dipping below into acid liquid, and surrounded 
in the space above the liquid by hydrogen and 
oxygen H, H' and O, O', etc., respectively is 
shown in Fig. 39. 



Battery, Leyden Jar- 




Fig. 3Q. Gas Battery. 

In charging this battery an electric current is 
sent through it until a certain quantity of the 
gases has been produced. If, then, the charging 
current be discontinued, a current in the oppo- 
site direction is produced by the battery. The 
gas battery is in reality a variety of storage bat- 
tery. (See Electricity, Storage of. Cell, Secon- 
dary. Cell, Storage.) 

Gas batteries can also be made by feeding con- 
tinually into the cell a gas capable of acting on 
the positive elements. 

Battery Gauge.— (See Gauge, Battery.) 



— The combina- 
tion of a number of separate Leyden jars so 
as to act as one single jar. 

A Leyden jar battery is shown in Fig, 40, 




Fig. 40, Leyden Jar Battery. 

where nine separate Leyden jars are connected 
as a single jar by joining their outer coatings by 
placing them in the box P, the bottom of which 
is lined with tin foil. The inner coatings are 
connected together by the metal rods B, as 
shown. 

A discharging rod A, may be employed for 
connecting the opposite coatings. The handles 
are made of glass or any other good insulating 
material. 

A number of Leyden jars can be coupled in 
series by connecting the inner coating of the first 
jar to the outer coating of the second, the inner 
coating of the second to the outer coating of the 
third, and so on. The battery so obtained is 
then discharged by connecting the outer coat- 
ing of the first jar with the inner coating of the 
last. 

Battery, Local A voltaic battery 

used at a station on a telegraph line to 
operate the Morse sounder, or the register- 
ing or recording apparatus, at that point 
only. (See Telegraphy, American or Morse 
System of.) 

The local battery is thrown into or out of action 
by the telegraphic relay. (See Relay.) 

Battery, Magnetic The . combina- 
tion, as a single magnet, of a number of sep- 
arate magnets. 

A magnetic battery, or compound magnet, is 



Bat.] 



46 



[Bat. 



shown in Fig. 41. It consists of straight bars of 
steel, p. p, p, with their similar poles placed near 
together and inserted in 
masses of soft iron, N and 
S, as shown. 

Battery, Main 



The plunge battery shown in Fig. 42, consists 




Fig, 4.7, Magnetic 
Battery, or Com- 
pound Magnet., 



The batter}' - , in a system 
of telegraphic communi- 
cation, that is employed 
for sending the signals 
over the main line, as dis- 
tinguished from any bat- 
tery employed for any 
other particular work, 
such, for example,, as that 
of the local battery. (See 
Battery, Local) 

Battery, Multiple-Con- 
nected — A battery the single cells of 

which are connected to one another and to the 
mains or conductors in multiple. (See Cir- 
cuit, Multiple) 

Battery, Open-Circuit A voltaic 

battery which is normally on open-circuit, 
and which is used continuously only for com- 
paratively small durations of time on closed- 
circuit. 

Leclanche-cells form an excellent open-circuited 
battery. They have a comparatively high electro- 
motive force, but rapidly polarize. They cannot 
therefore be economically used for furnishing 
currents continuously for long durations of time. 
When left on open-circuit, however, they readily 
depolarize. They therefore form an excellent 
battery for such work as annunciator bells, burg- 
lar alarms, etc., where the current is only 
required for short periods of time, separated by 
comparatively long intervals of rest. (See Cell, 
Voltaic, Leclanche.) 

Battery Plates of Secondary or Storage 

Cell, Forming of (See Plates of 

Secondary or Storage Cell, Forming of) 

Battery, Plunge A number of 

separate voltaic cells connected so as to form 
a single cell or electric source, the plates of 
which are so supported on a horizontal bar 
as to be capable of being simultaneously 
placed in, cr removed from, the exciting 
liquid. 




Fig. 42. Plunge Battery* 

of a number of zinc-carbon elements immersed in 
an electrolyte of dilute sulphuric acid, or in elec- 
tropoion liquid, contained in separate jars, J, J. 
(See Liquid, Electropoio7i) 

The mode of support to the horizontal bar 
will be understood from an inspection of the 
drawing. 

Battery, Primary The combina- 
tion of a number of separate primary cells so 
as to form a single source. 

The term primary battery is used in order to 
distinguish it from secondary or storage battery. 
(See Cell, Secondary. Cell, Storage) 

Battery, Secondary The combina- 
tion of a number of separate secondary or 
storage cells, so as to form a single electric 
source. (See Electricity, Storage of) 

Battery, Selenium The combina- 
tion of a number of separate selenium cells so 
as to form an electric source. (See Cell, 
Selenium) 

Battery, Series-Connected A bat- 
tery, the separate cells of which are con- 
nected to one another and to the line or 
conductor in series. (See Circitit, Series) 

Battery Solution. — (See Solution, Bat- 
tery) 

Battery, Split A voltaic battery 

connected in series, but having one of its 
middle plates connected with the ground. 

By the employment of the device of a split- 
battery, the poles of the battery are maintained 
at potentials differing in opposite directions from 
the potential of the earth. 

Battery, Storage A number of 

separate storage cells connected so as to 
form a single electric source. 



Bat.] 



47 



[Bel. 



A cell of a storage battery is shown in Fig. 



43- 




Fig. 43. Storage Battery. 

Battery, Storage, Element of A 

single set of positive and negative plates of a 
storage cell connected so as to be ready for 
placing in the acid liquid of the jar or cell. 

A term sometimes applied to one of the 
storage cells in a storage battery. 

This latter use of the term element is unfortu- 
nate, since from the analogous case of a primary 
cell, an element would consist of a single plate, 
either positive or negative, and not of both. That 
is, every voltaic couple consists of two elements, 
the positive and the negative. 

Battery, Thermo A term often 

applied to a thermo-electric batter}-. (See 
Battery, Thermo-Electrzc.) 

Battery, Thermo-Eleetric —The 

combination, as a single thermo-electric cell, 
of a number of separate thermo-electric cells 
or couples. (See Couple, Thermo-Electric?) 

Battery, Voltaic The combina- 
tion, as a single source, of a number of sepa- 
rate voltaic cells. 

Battery, "Water A batter}- formed 

of zinc and copper couples immersed in an 
electrolyte of ordinary water. 

Any voltaic couple can be used, the positive 
element of which is slightly acted on by water. 
When numerous couples are employed consider- 
able difference of potential can be obtained. 

Water batteries are employed for charging 
electrometers. They are not capable of giving 
ary considerable current, owing to their great in- 
ternal resistance. 



Bead Areometer or Hydrometer. — (See 
Areometer, Bead.) 

Bec-Carcel. — The Carcel, or French unit 
of light. (See Carcel?) 

Bell, Automatic-Electric An elec- 
tric bell furnished with an automatic contact- 
breaker. (See Contact-Breaker, Automatic?) 

A form of automatic-electric bell is shown in 
Yi<y. 44. The relation of the electro-magnet, its 
armature and the bell 
lever, will be readily 
understood from an in- 
spection of the draw- 
ing. 

Bell, Call 

An electric bell used 
to call the attention 
of an operator to the 
fact that his corre- 
spondent wishes to 
communicate with 
him. 

Bell, Circular 

—A bell so construct- 
ed that all its moving 
parts are contained in pf g% 44 , 
the gong. 

Bell, Continuous-Sounding Electric 

— An electric bell, which, on the completion 
of the circuit, continues striking until stopped 
either by hand or automatically. 

On the completion of the circuit, the attraction 
of an armature throws a catch off from a lever, 
and thus permits the lever to fall and^complete a 
contact and allows the current to ring the bell; or 
the bell is rung by clockwork, which is thrown 
into action by the passage of a current through an 
electro-magnet. (See Bell, Electro-Mechanical .) 

Bell, Differential Electric An 

electric bell, the magnetizing coils of which 
are differentially wound. 

Differential winding is ot advantage where a 
very strong current is required, as this winding 
decreases the sparking at the contacts, on the 
opening of the circuit. 

Bell, ElectroOIagnetic, Siemens- Arma- 
ture Form A form of electro-mag- 




Atitomatic Electric 
Bell. 



Eel.] 



48 



[Bel. 




netic bell in which the movements of the bell 
armature are obtained by the reversal of 
polarity that takes place when alternating cur- 
rents are pass- p»a^ 
ed through the \ ^\' 
coils of a sim- 
ple, single coil, 
Siemens - arma- 

F*g* 4S» Siemens-Armature Form 

The details of Electro-Magnetic Bell. 

will be readily understood from an examination 
°f Fi g- 45- 

Bell, Electro-Mechanical A bell, 

the striking apparatus of which is driven by 
a weight or spring, called into action by the 
movement of the armature of an electro- 
magnet. (See Alarm, Electric) 

Bell, Extension-Call A device for 

prolonging the sound of a magneto call. 

An alarm bell is automatically connected with 




Fig. 4b. Extension- Call Bell. 
the circuit of a local battery by means of the cur- 
rent generated by the magneto-call, and continues 
sounding after the current of the magneto- call 
has ceased. 

A form of extension-call bell is shown in Fig. 46. 

Bell, Indicating 1 An electric bell 

in which, in order to distinguish between 
different bells in the same office, a number 
is displayed by each bell when it rings. 

Bell, Magneto-Electric — An electric 

bell, the current employed to operate or 
strike which is obtained by the motion of a 
magneto-electric machine. 

Bell, Night In a telephone ex- 
change, a bell, switched into connection with 
the shunted circuit of an annunciator case, and 
intended, by its constant ringing, to call the 
attention of the night operator to the falling 
of a drop. 



Bell, Belay, Electric An electric 

bell in which a relay magnet is employed to 
switch a local battery into the circuit of the 
sounding apparatus of the bell. 

The relay bell is suitable for use when the bell 
to be sounded is situated at a great distance. As 
the current from the 1 ine, when this is long, is 
too weak to ring the bell, it throws into action a 
local battery by the action of a relay. 

Relay bells were used in the early forms of 
acoustic telegraphs as employed in England with 
relay sounders. 

The dots and dashes of the Morse alphabet were 
indicated by the sounds of two bells, a tap on 
one bell indicating a dot, and a tap on the other 
a dash. This system is now practically aban- 
doned. 

Bell-Shaped Magnet. — (See Magnet, Bell- 
Shaped) 

Bell, Shunt, Electric An electric 

bell, the magnetizing coils of which are placed 
on the line in shunt. 

In the case of shunt-connected electric bells, 
one of the bells must make and break the circuit 
for all the rest. The series-connected electric 
bell is used where the distance between the sepa- 
rate bells is great, in order to save the expense of 
multiple connections. 

In most cases, where a number of electric bells 
are to be simultaneously sounded, connection in 
multiple is adopted. 

Bell, Single-Stroke Electric An 

electric bell that gives a single stroke only for 
each make of the circuit. 




I 



Fig. Af. Single-Stroke Bell. 

Since the bell gives a single stroke for each 
completion of the circuit, its use permits of ready 
communication between any two places by any 



Bel.] 



49 



[Bla. 



system of prearranged signals. A buzzer may be 
used for the same purpose. A form of single- 
stroke bell is shown in Fig. 47. On completing the 
circuit, the current, through its coils, attracts the 
armature and causes a single stroke of the bell. 

Bell, Telephone-Call A call bell 

used to call a correspondent to the telephone. 

The telephone-call bell is generally a magneto- 
electric bell. 

Bell, Trembling' A name some- 
times given to a vibrating or an automatic 
make-and-break bell. (See Make-and-Break, 
Automatic?) 

— A trembling bell. 



Bell, Vibrating- — 

(See Bell, Trembling^) 

Bias of Relay Tongue. — (See Tongue, 
Relay, Bias of.) 

Bichromate Yoltaic Cell.— (See Cell, Vol- 
taic, Bichromate^) 

Bi-fllar Suspension. — (See Suspension, 
Bi-filar) 

Bi-fllar Suspension Balance. — (See Bal- 
ance, Bi-filar Suspe7isio7i) 

Bi-fllar Winding.— (See Winding, Bi- 
filar) 

Binary Compound.— (See Compoimd, Bi- 
nary) 

Binding Coils.— (See Coils, Binding) 

Binding-Post.— (See Post, Bi7iding) 

Binding-Screw. — (See Screw, Bindi7ig) 

Binding- Wire for Telegraph Lines. — (See 
Wire, Bindi7ig,for Telegraph Li7ies) 

Biology, Electro That branch of 

electric science which treats of the electric 
conditions of living animals and plants, and 
the effects of electricity upon them. 

Electro-Biology includes : 

(1.) Electro-rhysiology. 

(2.) Electro-Therapy, or Electro-Therapeutics. 

Bioplasm. — Any form of living matter pos- 
sessing the power of reproduction. 

Bioscopy, Electric The determina- 
tion of the presence of life or death by the 
passage of electricity through the nerves and 
muscles. 

Bi-poiar. — Having two poles. 



Bi-polar Armature. — (See Awiatitre, 
Bi-polar.) 

Bi-polar Bath.— (See Bath, Bi-polar) 

Birmingham Wire Gauge. — (See Gauge, 
Wire, Bir77iingha77i) 

Bi-Telephone. — (See Telepho7ie, Bi) 

Bitite. — A variety of insulating material. 

Black Electro-Metallurgical Deposit. — 
(See Deposit, Black Electro-Metallurgical) 

Black Lead. — A variety of carbon em- 
ployed in various electrical processes. 

Black lead is also termed plumbago or graphite, 
(See Plumbago. Graphite.') 

The term black lead is a misnomer, since the 
substance is carbon and not lead. The term is an 
old one, and is still very generally used. 

Blasting, Electric The electric 

ignition of powder or other explosive material 
in a blast. (See Fuse, Electric) 

The current required for the ignition of the 
fuse is generally obtained by means of a magneto - 
electric machine. In the form of magneto-blast- 
ing machine, shown in Fig. 48, the movement 




Fig. 48. Magneto-Blasting Machine. 

of the handle shown at the top of the figure 
causes the rapid rotation of a cylindrical armature 
constructed on the YVheatstone and Siemens prin- 
ciple. The magnets#.re of iron, and are furnished 



Ble.J 



50 



[Boa. 



with coils of insulated wire. On the rotation of 
the armature the current developed therein in- 
creases the field of the field magnet, and, when 
of the proper degree of intensity, is thrown into the 
outer circuit, and ignites the fuse. 

Bleaching-, Electric Bleaching pro- 
cesses in which the bleaching agents are 
liberated, as required, by the agency of electro- 
lytic decomposition. 

In the process of Naudin and Bidet, the cur- 
rent from a dynamo-electric machine is passed 
through a solution of common salt between two 
closely approached electrodes. The chlorine and 
sodium thus liberated react on each other and 
form sodium hypochloride, which is drawn off 
by means of a pump and used for bleaching. 
(See Electrolysis.) 

Block, Branch —A device em- 
ployed in electric wiring for taking off a branch 
from a main circuit. (See Wiring.) 

A form of branch-block, with its fuses attached, 
is shown in Fig. 49. 




Fig. 4Q. Branch-Block. 

Block, Cross-Over A device to 

permit the safe crossing of one wire over 
another in molding or cleat wiring. 

Block, Fuse — A block containing 

a safety fuse or fuses for incandescent light 
circuits. (See Fuse, Safety?) 

Block System for Railroads. — (See Rail- 
roads, Block System for.) 

Block Wire.— (See Wire, Block) 

Blow-Pipe Electric A blow-pipe 

in which the air-blast is obtained by a stream 
of air particles produced at the point of a 



charged conductor by a convection dis- 
charge. 

The candle flame, Fig. 50, is blown in the di- 
P 




Convection Blow-Pipe. 

rection of the stream of air particles passing off 
from the point P. (See Convection, Electric.) 

Blow-Pipe, Electric-Arc A de- 
vice of Werdermann for cutting rocks, or 
other refractory substances, in which the heat 
of the voltaic arc is directed, by means of a 
magnet, or a blast of air, against the substance 
to be cut. 

The carbons are placed parallel, so as to readily 
enter the cavity thus cut or fused. This inven- 
tion has never been introduced into extensive 
practice. 

In the welding process of Benardos and 
Olzewski, the welding temperature is obtained by 
means of an electric arc taken between two suit- 
ably shaped electrodes. 

In the electric-arc 
blow - pipe, shown in 
Fig. 51, the voltaic arc, 
taken between two ver- 
tical carbon electrodes, 
is deflected into a hori- 
zontal position under the 
influence of the inclined 
poles of a powerful elec- 
tro-magnet. 

The highly heated car- 
bon vapor which consti- 
tutes the voltaic arc is deflected by the magnet in 
the same direction as would be any other mov- 
able circuit or current. 

Board, Cross-Connecting' In a 

system of telegraphic or telephonic communi- 
cation, a board to which the line terminals are 
run before entering the switchboard, so as to 




Fig. 51. Electric- Arc 
Blow-Pipe. 



Boa.] 



51 



[Boa. 



readily place any subscriber in connection 
with any desired section of the switchboard. 

Board, Fuse A board of slate or 

other incombustible material on which all 
the safety fuses in an installation are as- 
sembled. 

The fuse board is u=ed for avoiding accidents 
from the firing of the fuses. 

Board, Hang-er A form of board 

provided for the ready placing or removal of 
an arc lamp from a circuit. 




Fig. jrs. Hanger-Board, 

A hanger-board contains a switch or cut-out for 
the ready opening or closing of the circuit. A 
torm of hanger-board is shown in Fig. 52. 

Board, Key Any board to which 

are connected electric keys or switches. 

Board, Leg-glng'-Key A key board 

employed for the purpose of legging an 
operator into a circuit connecting two or more 
subscribers. (See Leg.) 

Board, Multiple Switch A board 

to which the numerous circuits employed in 
systems of telegraphy, telephony, annunciator 
or electric light and power circuits are con- 
nected. 

Various devices are employed for closing these 
circuits, or for connecting or cross-connecting 
them with one another, or with neighboring cir- 
cuits. 

A multiple switchboard, for example, for a tele- 
phone exchange, will enable the operator to con- 
nect any subscriber on the line with any other 
subscriber on that line, or on another neighbor- 



ing line provided with a multiple switchboard. 
To this end the following parts are necessary: 

(i.) Devices whereby each line entering the ex- 
change can readily have inserted in its circuit a 
loop connecting it with another line. This is 
accomplished by placing on the switchboard a 
separate spring-jack connection for each sepa- 
rate line. This connection consists essentially 
of one or two springs made of any conducting 
metal, which are maintained in 
metallic contact when the plug 
key is not inserted, but which are 
readily separated from one another 
by the introduction of the plug- 
key t Fig. 53, the terminals, a and 
b, of which are insulated from 
each other, and are connected to 
the ends of a loop coming from 
another line. As the key is in- 
serted, the metallic spring or 
springs of the spring-jack are separated and the 
metallic pieces, a and b, are brought into good 
sliding contact therewith, thus introducing the 
loop into the circuit. (See Spring- Jack.) 

(2.) As many separate annunciator-drops as 
there are separate subscribers. These are pro' 
vided so as to notify the Central Office of the par- 
ticular subscriber who desires a connection. 
Alarm-bells to call the operator's attention to the 
calling subscriber, or to the falling of a drop, are 
generally added. (See Bell, Call.) 

(3.) Connecting cords and keys for connecting 
the operator's telephone, and means for ringing 
subscribers' bells, and clearing out drops. 




Fig>53' Plug- 
Key. 




Fig. S4- Multiple Switchboard 'for Electric Light. 

In Multiple Switchboards for the Electric Light 
or Distributing Switches, spring-jack contacts are 
connected with the terminals of different circuits, 



Boa.] 



52 



[Bod, 



and plug switches with the dynamo terminals. 
By these means, any dynamo can be connected 
with any circuit, or a number of circuits can be 
connected with the same dynamo, or a number 
of separate dynamos can be placed in the same 
circuit without interference with the lights. 



-A board provided 




Board, Switch — 

with a switch or switches, by means of Which 
electric circuits connected therewith may be 
opened, closed, or interchanged. 

Board, Switch, Telegraphic — A 

device employed at a telegraph station by 
means of which any one of a number of tele- 
graph instruments, in use at that station, may 
be placed in or removed from any line con- 
nected with the station, or by means of which 
one wire may be connected to another. 

The ability to readily connect one wire with 
another is of use in case of interruption to tele- 
graph lines, in which case a through circuit may 
be made up of sections of 
different circuits. 

In the switchboard shown 
in Fig. 55, the upper left- 
hand binding-post is con- 
nected to earth; the four 
remaining binding - posts 
are connected to two sepa- 
rate instruments— the sec- 
ond and third from the top to one instrument, 
and the fourth and fifth to another instrument. 
The four posts at the top of the figure are con- 
nected to two lines running east and west. 

Various connections are made by the insertion 
of plug keys in the various openings. 

Board, Switch, Trunking — A 

switchboard in which a few subscribers only 
are connected with the operator, thus enabling 
him to obtain any other subscriber by means 
of trunk wires extending to the other sections. 
(See Wire, Trunk?) 

Boat, Electric —A boat provided 

with electric motive power. 

Electric power has been applied both to ordi- 
nary vessels and to submarine torpedo boats. 

Boat, Submarine Electric A boat 

capable of being propelled and steered while 
entirely under water. 

The motive power of such boats is generally 



Fig> 55- Telegraphic 
Switchboard. 



electricity. The requisite buoyancy is obtained 
by means of an air chamber. Artificial ventila- 
tion is maintained, the fresh air requisite for 
breathing being derived from a compressed air 
cylinder. 

Boat, Torpedo ■ —A boat used for 

carrying and discharging torpedoes. (See 
Torpedo?) 

Bobbin, Electric An insulated coil 

of wire for an electro-magnet. 

Body, Charged A body containing 

an electric charge. 

Charges are bound or free. (See Charge, 
Bound. Charge, Free.) 

Body, Electrified A body con- 
taining an electric charge. 

Body, Human, Resistance of — 



The resistance which the human body offers to 
the passage of an electric current. 

The resistance of the human body to the passage 
of a current varies with the time. The re- 
sistance rapidly decreases after a short time. 

" The resistance diminishes because of the con- 
duction of water in the epidermis under the action 
of the constant current and the congestion of the 
cutaneous blood vessels in consequence of the 
stimulation . " ( Landois and Stirling. ) 

The resistance also varies markedly with the 
condition of the surface, the condition of the skin, 
and with the shape, area, position and material 
of the electrodes by which the current is led into 
and carried out of the parts. It very seldom is 
less than 1,000 ohms under the most favorable 
conditions, and with ordinary contacts is many 
times that amount. 

The muscles'offer nearly nine times the resist- 
ance in a direction transverse to the fibres than 
longitudinally to them. {Hermann.} 

The resistance of the epidermis is greater than 
that of any other tissue of the body. 

The human body probably possesses a true 
assymmetricai resistance; that is to say, when 
taken after the current has been passing for some 
time, its resistance is different in different direc- 
tions. This variation in the apparent resistance 
is believed by some to be due to polarization 
effects. 

Body, Insulated —A body sup- 
ported on an insulator, or non-conductor of 
electricity. 



Bod.] 



53 



[Box. 




Body-Protector, Electric —A de- 
vice for protecting the human body against the 
accidental passage of an electric discharge. 

To protect the human body from the acciden- 
tal passage through it of dangerous electric cur- 
rents, Delany places a light, flexible, conducting 
■wire, A A B L L, in the posi- 
tion shown in Fig. 55, for 
the purpose of leading the 
greater part of the current 
around instead of through 
the body. The body-pro- 
tector thus provides a by- 
path, or shunt of low resist- 
ance, around the body, and 
protects it from the effects 
of an accidental discharge. F*g- S&- Electric 
The resistance of the con- Body-Protector. 
tacts of the protecting conductor with the skin 
may interfere somewhat with the efficacy of the 
device. Inside insulating shoe-soles for lessening 
the danger from accidental contacts through 
grounded circuits have also been proposed. 

Boiler-Feed, Electric — A device 

for automatically opening a boiler-feed appar- 
atus electrically when the water in the boiler 
falls to a certain predetermined point. 

Boiling' of Secondary or Storage Cell.— 
(See Cell, Secondary, or Storage, Boiling of.) 

Bole. — A unit, seldom or never used, pro- 
posed by the British Association. 

One bole is equal to one gramme-kine. (See 
Kim.) 

Bolometer.— An apparatus devised by 
Langley for measuring small differences of 
temperature. 

A thermal balance. (See Balance, Titer- 
mic.) 

Bombardment, Molecular — The 

forcible rectilinear projection from the nega- 
tive electrode, of the gaseous molecules of the 
residual atmospheres of exhausted vessels on 
the passage of electric discharges. (See 
Matter, Radiant, or Ultra-Gaseous) 

Bonsalite. — An insulating substance. 

Bore, Armature ■ —The space pro- 
vided between the pole pieces of a dynamo 
cr motor for the rotation of the armature. 



Boreal Magnetic Pole.— (See Pole, Mag- 
netic, Boreal.) 

Bot. — A term sometimes used as a con- 
traction for Board of Trade unit of electric 
supply, or the energy contained in a current 
of 1,000 amperes flowing in one hour under a 
pressure of one volt. 

The term appears inadmissible. If used at all, 
it should be B. O. T. The usage of giving the 
names of distinguished dead electricians to new 
units is a good one, and should be followed here. 

Boueherize. — To subject to the boucheriz- 
ing process. (See Boucherizing.) 

Boueherizing. — A process for the preser- 
vation of wooden telegraph poles, by inject- 
ing a solution of copper sulphate into the 
pores of the wood. (See Pole, Telegraphic.) 
Bound Charge. — (See Charge, Bound.) 
Box Bridge. — (See Bridge, Box) 

Box, Cable ■ — A box placed on a 

large terminal pole and provided to receive the 
separate conductors where the air-line wires 
join a cable. 

The wires are distributed in the cable box so 
as to be readily attached to the air-line wires. 

Box, Cooling, of Hydro-Electric Ma- 
chine. — A box provided in Armstrong's 
hydro-electric machine for the steam to pass 
through before leaving the nozzle. 

In passing through the cooling -box some of the 
steam suffers condensation. The cooling-box, 
therefore, always contains some water, the pres- 
ence of which seems to be necessary to the opera- 
tion of the machine. 

Box, Distributing, of Conduit. — A name 
generally applied to a handhole of a conduit. 
(See Handhole of Conduit.) 

Box, Distribution, for Arc Light Cir- 
cuits. — A device by means of which arc 
and incandescent lights may be simultane- 
ously employed on the same line from a con- 
stant-current dynamo-electric machine or 
other source of constant currents. 

A portion of the line circuit, whcse difference 
of potential is sufficient to operate the electro- 
receptive device, as, for example, an incandescent 
lamp, is divided into such a number of multiple 



Box.] 



54 



[Box. 



circuits as will provide a current of the requisite 
strength for each of the devices. For example, if 
the normal current on the line is seven amperes, 
then each of the seven multiple-connected electro- 



F'g- 57- Series- Multiple Circuit. 
receptive devices shown in Fig. 57 will have a cur- 
rent of one ampere passing through it, provided 
the resistance of each branch is the same. 

In order to protect the remaining devices from 
variations in the current on the extinguishment of 
any of the devices, automatic cut-outs are pro- 
vided, which divert the current thus cut off 
through a resistance equivalent to that of the 
device. 

A variety of distribution boxes are in use. (See 
Circuits, Varieties of.) 

Box, District-Call — A box by 

means of which an electric signal is auto- 
matically sent over a telegraphic line and 
received by an electro-magnetic device at the 
other end of the line. 




Fig. 58. District Call Box. 

A system of district calls includes a number of 
call boxes connected by telegraphic lines with a 
central station. A wheel, or its equivalent, set in 



motion by the pulling of a lever, makes and 
breaks an electric circuit and sends over the line 
a succession of electric impulses of varying length, 
separated from one another by varying intervals 
of time. These impulses may be received at the 
central station as a series of dots and dashes, or 
may, by means of a Morse sounder, produce suc- 
cessive sounds. By pulling the lever or handle 
through different distances, different signals may 
be sent to the central station and serve as calls for 
various services, such as messenger boys, fire 
alarm, police, special, etc. 

The general appearance of a four-call district 
box is shown in Fig. 58. In order to transmit 
a call for any particular one of these four services 
the handle is pulled until it comes opposite to the 
letters indicating the required service, and is then 
released. The service required is then indicated 
at the receiving, or central station, through the 
varying signals sent over the line by the move- 
ment of the break-wheel, on the release of the 
handle. 

Box, Fire-Alarm Signal A signal 

box provided for the purpose of automatically 
sending an alarm of fire. 

The fire-alarm box shown in Fig. 59, operates 




Fig. $Q. Fire- Alarm Signal-Box. 

on the same principle as the district call box. The 
movement of the handle in the direction of the 
arrow drives a wheel that makes and breaks a 
circuit at certain intervals. 

The fire-alarm signal boxes are connected 



Box.] 



55 



[Box. 



either with a central station, cr with the engine 
houses of the district in which the alarm is 
sounded, or with both. 

Box, Fire-Alarm Telegraph An 

automatic-call signal-box employed fcr send- 
ing an alarm of fire to a central station. 

A form of fire-alarm telegraph box is shown in 
Fig. 60. It consists essentially of a circuit-breaker 




Fig. bo. Fire-Alarm Telegraph Box. 
that is moved by pulling down a lever. The 
release of the lever repeats the signal to the fire 
department at the central station a certain number 
of times. The box also contains a relay bell, 
lightning arrester and signal-bell key. 

Box, Fishing" A term sometimes 

used instead of junction box. (See Box, 
J miction.) 

Box, Flush A box or space, flush 

with the surface of a road-bed, provided in a 
system of underground wires or conduits, 
to facilitate the introduction of the conduct- 
ors into the conduit, or for the examination 
of the conductors. 

Box, Fuse The box in which the 

fuse-wire of a safety-fuse is placed. 

The fuse-box should be formed of moisture- 
proof, incombustible, insulating materials. 

Box, Junction ■ • —A moisture-proof 

box provided in a system of underground con- 




the feeders and the mains, and from which 
the current is distributed to the individual 
consumer. (See Feeder. Mam, Electric?) 

A form of junction box for coupling lengths of 
conductors is shown in Fig. 61. 

Box, Patrol Alarm — An automatic- 
signal call-box provided for use on the out- 
side of buildings. 

The call-box is placed inside a box, the outer 
door of which is furnished with a Yale lock. 




Fig. 62. Patrol Box. 
A form of patrol box is shown in Fig. 62. 
Box, Resistance — 



■A box containing 



Fig. 61. Junction Box. 

ductors to receive the terminals of the feed- 
ers, m which connection is made between 



a number of separate coils of known resist- 
ances employed for determining the value of 
an unknown resistance, and for other pur- 
poses. (See Bridge, Electric, Box Form of.) 

Box-Sounding* Relay. — (See Relay, Box- 
Sounding .) 

Box-Sounding- Telegraphic Relay. — (See 
Relay, Box-Sounding Telegraphic.) 

Box, Splice ■ — A box provided for 

holding splice joints and loops, and so ar- 
ranged as to be readily accessible for exami- 
nation, re-arrangmg, cross-connecting, etc. 

Splice-boxes vary m shape and construction 
according to the purposes ior which they are 
designed. 

Box, Splice, Four-way A splice- 
box piovided with four ways or tubular con- 
duits, 

Box, Splice, TwoTYay A splice- 



Box.J 



56 



[Bra. 



box provided with but two tubular conduits or 
ways. 

Box, Tumbling A rotating box 

in which metallic articles that are to be 
electroplated are placed so as to be polished 
by attrition against one another. 

Boxing" the Compass. — (See Compass, 
Boxing t/ie.) 

Bracket, Lamp, Electric A de- 
vice similar to a bracket for a gas burner for 
holding or supporting an electric lamp. 




; v. c ft /% 




Fig* 6 3 > Lamp Bracket. Fig. 64. Lamp Bracket. 
Lamp brackets are either fixed or movable. 




Fig. 6j. Lamp Bracket, Movable Arms. 

Those shown in Figs. 63 and 64 are fixed. That 
shown in Fig. 65 is movable. 

Bracket, Telegraphic A support 

or cross piece placed on a telegraph pole 
lor the support of the insulators of tele- 
graphic lines. 

Telegraphic insulators are supported either on 
wooden arms, or on iron or metal brackets. 

Fig. 66 shows a form of iron bracket. Fig. 6j 
shows a form of wooden arm. 





Fig. 67. Telegraphic 
Cross- Arm. 



Fig. 66. Telegraphic 
Bracket. 

Various well known modifications of these 
shapes are in common use. (For details, see Jrole, 
Telegraphic. ) 



Braid, Tuhular A braid of fibrous 

insulating material, woven in the form of a 
tube, and provided for drawing over a splice 
after two wires have been connected. 

Braided Wire. — (See Wire, Braided^ 

Brake, Electro-Magnetic A brake 

for car wheels, the braking power for which 
is either derived entirely from electro-magnet- 
ism, or is thrown into action by electro-mag- 
netic devices. 

Electro-magnetic car brakes are of a great va- 
riety of forms. They may, however, be arranged 
in two classes, 9 viz. : 

(1.) Those in which magnetic adhesion, or the 
magnetic attraction of the brake to the wheels, is 
employed. 

(2.) Ordinary brake mechanism in which the 
force operating the brake is thrown into action by 
an electro-magnet. 

Brake, Friction A name some- 
times given to a Prony brake. (See Brake, 
Prony.) 

• — A device 



Brake, Magneto-Electric — 

for checking the swing of a galvanometer, in 
which a slight inverse current is sent through 
the coils of the galvanometer. 

The Frey magneto-electric brake, as shown in 
Fig. 68, consists of a small coil, connected by a 




Fig. 68. Electric Brake. 

contact-key with the galvanometer terminals. A 
small adjustable magnet coil is provided for 
regulating the action of the inverse current. To 
avoid disturbance, the brake is placed at least 
4 or 5 feet from the galvanometer. Manipulation 
of the ordinary galvanometer key attains the same 
end in a much simpler manner. 

Brake, Prony A mechanical de- 
vice for measuring the power of a driving 
shaft. 



Bra. 



57 



[Bre. 



An inflexible beam, Fig. 69, is provided at one 
end with a clamping device for clamping the 
driving shaft or pulley, and at the other end A, 
with a pan for holding weights. 

If the brake be arranged as shown in Fig. 69, 
and the shaft rotate in the direction of the arrow, 
the tendency will be to carry the beam around 
with the shaft, placing it at some given moment 




Fig. 6q> Pro?iy Brake. 
in the position shown by the dotted line. If a 
sufficiently heavy weight be placed at x, in a pan 
hung at A, the beam will assume a position ver- 
tically downwards. If, however, the torque, or 




Fig. JO. Prony Brake. 

twisting force of the driving shaft, be balanced by 
the weight, the bar will remain horizontal. The 
power can then be calculated by multiplying the 
weight in pounds by the circumference in feet of 
the circle of which the bar is a radius, and this 
product by the number of turns of the driving 
shaft per minute. The product will be the num. 





Fig. J I. Prony Brake. 
ber of foot-pounds per minute, and, when divided 
by 33,000, will give the horse-power. 

Some modified forms of the Prony brake are 
shown in Figs. 70 and 71. 

A simple form of brake consists of a cord passed 
over the pulley of the machine to be tested. A 
weight is hung at one end of the cord. The other 



end of the cord is attached to the top of a spring 
balance, the other end of which is fastened to the 
floor. A reading of the spring balance is taken 
while the pulley is at rest and when it is in motion, 
and the result calculated. 

Branch. — A term applied to any principal 
distributing conductor from which outlets 
are taken or taps made. 

Branch-Block. — (See Block, Branch?) 

Branch Conductors. — (See Conductor, 
Branch?) 

Branch Fuse. — (See Fuse, Branch?) 

Branch, Sub A distributing con- 
ductor taken from a branch. 

Branding, Electric — A process 

whereby the branding tool is heated by elec- 
trical incandescence instead of by ordinary 
heat. 

The branding tool consists essentially of a small 
transformer with devices for regulating the cur- 
rent strength by switches and choking coils. 

Brassing", Electro Coating a sur- 
face with a layer of brass by electro-plating. 
(See Plalt7ig, Electro?) 

The plating bath contains a solution of copper 
and zinc ; a brass plate is used as an anode. 

Break. — A want of continuity in a circuit. 

Break, Circuit Loop A device for 

introducing a loop in any part of a line 
circuit. 

A form of circuit loop-break is shown in Fig. 72. 




Fig. 7 2. Circuit Loop Break. 
It consists essentially of a rigid frame with two 
porcelain or other suitable insulators for the sup- 
port of the loop wires. 



Ere.] 



58 



[Bri. 



Break-Down Switch. — (See Switch, Break- 
Down?) 

Break-Induced Current. — (See Current, 
Break-Induced?) 

Break, Mercury A form of circuit 

breaker operated by the removal cf a conduc- 
tor from a mercury surface. 

Mercury breaks assume a variety of forms. One 
end of the circuit is connected with the mercury, 
and the other with the conductor. 

Break Shock. — (See Shock, Break?) 

Breaker, Circuit Any device for 

breaking a circuit. 

Breaking 1 the Primary. — (See Primary, 
Breaking the.) 

Breaking* Weight of Telegraph Wires. — 
(See Wires, Telegraph, Breaking Weight 
of.) 

Breath Figures. — (See Figures, Breath.) 

Breeze, Electric A term some- 
times employed in electro-therapeutics for a 
brush discharge. 

One of the electrodes, consisting of a single 
point or a number of points, is held near the 
parts to be treated so that th e convective discharge 
is received thereon. The other electrode is con- 
nected to the body of the patient. 

Breeze, Electro-Therapeutic An 

electric breeze. (See Breeze, Electric?) 

Breeze, Head, Electro-Therapeutic 

— A form of electric convective discharge, 
or electric breeze, applied to the head. (See 
Breeze, Electric?) 

Breeze, Static An electric breeze 

obtained by the convective discharge of an 
electrostatic charge. 

Bridge-Arms. — (See Arms, Bridge or 
Balance?) 

Bridge, Box A box of resistance 

coils so arranged as to be capable of being 
used directly as a Wheatstone electric balance. 
(See Bridge, Electric, Box Form of?) 

The commercial form of Wheatstone's 
balance. 

Bridge, Electric — A device for 

measuring the value of electric resistances. 



The electric bridge is also called the Electric 
Balance. 

This is called a bridge because the wire M, G, 
N, bridges or joins points of equal potential. 

A, B, C and D, Fig. 73, are four electric re- 
sistances, any one of which can be determined in 
ohms, provided the absolute value of one of the 
others, and the relative values of any two of the 
remaining three are known in ohms. 

A voltaic battery, Zn C, is connected at Q 
and P, so as to branch at P, and again unite at 




Zn C 

Fig. J 3. Electric Balance. 

Q, after passing through the conductor D C, and 
B A. 

A sensitive galvanometer, G, is connected at 
M N, as shown. 

The passage of a current through any resistance 
is attended by a fall of potential proportional to 
the resistance. {See Potential, Electric.) If, then, 
the resistances A, C and B, are so proportioned 
to the value of the unknown resistance D, that no 
current passes through the galvanometer G, the 
two points, M and N, in the two circuits, Q M P 
and Q N P, are at the same potential. That is to 
say, the fall of potential along QMPandQN P, 
at the points M and N, is equal. Since the fall 
of potential is proportional to the resistance, it 
follows that 

A : B : : C : D, 
or A X D = B X C, 

If then we know the values of A, B and C, the 
value of D, can be readily calculated. 

By making the value __, some simple ratio, the 
A 

value of D, is easily obtained in terms of C. 

The resistances A, B and C, may consist of 
coils of wire whose resistance is known. To 
avoid their magnetism affecting the galvanometer 
needle during the passage of the current through 
them, they should be made of wire bent into two 



C. 



Bri.] 



59 



[Bri, 



parallel wires and wrapped in coils called resist- 
ance coils; or a resistance box may be used. (See 
Coil, Resistance. Box, Resistance.) 

There are two general forms of Wheatstone's 
Bridge, the box form, and the sliding form. 

Bridge, Electric, Arms of The 

resistances of an electric bridge or balance. 
(See Bridge, Electric?) 

Bridge, Electric, Box Form of 

A commercial form of bridge or balance in 
which all the known arms or branches of the 
bridge, except the unknown arm, consist of 
standardized resistance coils, whose values are 
given in ohms. (See Coil, Resistance.) 

The box form of bridge or balance is shown in 




Fig. 74. Box Balance. 

perspective in Fig. 74, and in plan in Fig. 75. 
The bridge arms, corresponding to the resistances 



x 1000 100 1 9 1 100 1000 




Fig. 7 J. Box Balance. 

A and B, of Fig. 73, consist of resistance coils of 
10, 100 and 1,000 ohms each, inserted in the 
arms q z, and q x, of Fig. 75. These are 
called the proportional coils. The arm corre- 
sponding to resistance C, of Fig. 73, is composed 
of separate resistances of 1, 2, 2, 5, 10, 10, 20, 50, 
100, 100, 200, 500, i,oco, 1,000, 2.000 and 5,000 
ohms. In some forms of box bridges additional 
decimal resistances are added. 

The resistance coils are wound, as shown in 
Fig. 76, after the wire has been bent on itself in 
the middle. This is done in order to avoid the 
effects of induction, among which are a disturb- 
ing action on a galvanometer used near them, 
and the introduction of a spurious resistance in 
the coils themselves. (See Resistance, Spurious.) 



To avoid the effects of changes of resistance oc- 
casioned by changes of temperature, the coils are 
made of German silver, or, preferably, of alloys 
called Platinoid or Platinum silver. Even when 
these alloys are used, care should be taken not to 
allow the currents to pass continuously through 
the resistance coils longer than a few moments. 

The coils, C, C, are connected with one another 
in series by soldering their ends to the short 




Resistance Coils. 



thick pieces of brass, E, E, E, Fig. 76. On the in- 
sertion of the plug-keys, at S, S, the coils are cut- 
out by short-circuiting. Care should be taken to 
see that the plug-keys are firmly inserted and free 
from grease or dirt, as otherwise the coil will not be 
completely cut out. As each plug-key is inserted 
it should be turned slightly in the opening, so 
as to insure good contact. 

The following are the connections, viz.: The 
galvanometer is inserted between q and r,.Fig. 77, 




Fig- 77- 



Zn ' e 
Electric Balance. 



the unknown resistance between z and r; the bat- 
tery is connected tox and z. A convenient pro- 
portion being taken for the value of the propor- 
tional coils, resistances are inserted in the arm C, 
until no deflection is shown by the galvanometer 
G. The similarity between these connections and 
those shown in Fig. 75 will be seen from an 
inspection of Fig. 77. The arms, A and B, corre- 
spond to q x and q z, of Fig. 75 ; C, to the arm 



60 



[Bri. 



x r, Fig. 75 5 and D, to the unknown resistance 
We then have as before: 

'B 



A:B::C:D, orAxD = BxC. 



D 



© 



C. 



The advantage of the simplicity of the ratios, A 
and B, or io, ioo and 1,000 of the bridge box, 
will therefore be manifest. The battery terminals 
may also be connected to q and r, and the gal- 
vanometer terminals to x and z, without disturb- 
ing the proportions. 

Bridge, Electric, Commercial Form of 

A name sometimes given to the box 

form of Wheatstone's electric balance. (See 
Bridge, Electric, Box For?n of.) 
Bridge, Electric Duplex — 



— An ar- 
rangement of telegraphic circuits in the form 
of a Wheatstone electric bridge for the pur- 
poses of duplex telegraphy. (See Teleg- 
raphy, Duplex, Bridge Method of.) 

Bridge, Electric, Proportionate Arms 

of (See Arms, Proportionated) 



Bridge, Electric, Slide-Form of 



A balance in which the proportionate arms of 
the bridge are formed of a single thin wire, of 
uniform diameter, generally of German silver, 
of comparatively high resistance. The length 
of this wire is usually one metre ; hence this 
apparatus is often called the metre bridge. 

A Sliding Contact Key slides over the wire; one 
terminal of the key is connected with the galva- 
nometer and the other with the wire when the key 
is depressed. As the wire is of uniform diameter 
the resistances of the arms, A and B, Fig. 78, will 



jsfc 



te^EaSM^?: 



I 



a 



Fig. 78. Slide Bridge. 

be directly proportional to the lengths. A scale 
placed near the wire serves to measure these 
lengths. A thick metal strip connected with the 
slide wire has four gaps at P, Q, R and S. 

When in ordinary use, the gaps at P and S, are 
either connected by stout strips of conducting ma- 
terial or by known resistances, in which latter case 
they act simply as ungraduated extensions of the 
slide wire, and, like lengthening the slide wire, 
increase the sensibility of the instrument. 



The unknown resistance is then inserted in the 
gap at Q, and a known resistance, generally the 
resistance box, in that at R. The galvanometer 
has one of its terminals connected to the metal 
strip between Q and R, and its other terminal to 
the sliding key. The battery terminals are con- 
nected to the metal strips between P and Q, and 
R and S, respectively. 

These connections are more clearly seen in the 
form of bridge shown in Fig. 79. The slide wire, 
w w, consists of three separate wires each a metre 




Fig. yg. Slide Form of Bridge. 

in length, so arranged that only one wire, or two 
in series, or all three in series, can be used. Mat- 
ters being now arranged as shown, the sliding 
key is moved until no current passes through the 
galvanometer when the key is depressed. 

The slide form of bridge is not entirely satis- 
factory, since the uncertainty of the spring-con- 
tact causes a lack of correspondence between the 
point of contact and the point of the scale on 
which the index rests. 

The loss of uniformity in the diameter of the 
wire, due to constant use, causes a lack of corre- 
spondence between the resistance of the wire and 
its length. With care, however, very accurate 
results can be obtained by the slide form. 

Bridge, Inductance An appara- 
tus for measuring the inductance of a circuit 
similar to a Wheatstone bridge. (See Indzic- 
tance^) 

Professor Hughes employed an inductance 
bridge of the following description: 

Four resistances, Q, S, R and P, arranged as 
shown in Fig. 80, form the bridge. The re- 
sistances, Q, S and R, consist of sections of Ger- 
man silver wire, one metre in length, each of 
the resistance of 4 ohms. P, is a coil of wire pos- 
sessing sensible inductance. The object of the 



Bri.] 



61 



[Bri, 



bridge is to measure the value of this inductance. 
I, is an interrupter placed in the circuit of the 
battery B. 

Suppose the interrupter, I, be placed in the tele- 
phone circuit between T and c. By shifting the 
sliding contact so as to alter the value of R, a bal- 




Fig. So 



ance can be effected and silence obtained in the 
telephone. 

Now remove the interrupter and place it in the 
battery circuit between b and a, as shown in Fig. 
80. If now, the interrupter, I, be made to rapidly 
interrupt the battery current, this balance is 
destroyed, and cannot be again obtained by any 
variation in the value of the resistance, R. 

The reason of this is evident. On the closing 
or opening of the battery current, the inductance 
of P, produces a counter electromotive force in 
P, which produces differences of potential between 
a and c. If an attempt be made to prevent this, 




Fig. St. Hughes' Inductance Bridge. 

by altering the value of R, the steady balance is 
destroyed, and the telephone will be traversed by 
a current during the time the currents have be- 
come steady. In order to obtain a balance 
during rapid alternations of the battery current, 
Professor Hughes placed a pair of mutually in- 



ductive coils in the battery and the telephone 
circuits, as shown in Fig. 81. 

The resistances, Q, S, R and P, are the same 
as already described. The mutually inductive 
coils, M x and M 2 , are placed respectively in the 
telephone and battery circuits in the manner 
shown. The coil M 2 , in the battery circuit is 
fixed, while that in the telephone circuit is so 
arranged that it can be maintained, with its centre 
coincident with that of M 2 , while its axis can be 
placed at any desired angle with M 2 . When the 
axes of the coils are at right angles, the inductance 
is zero. When they are co-linear, the inductance 
is at its maximum. 

When the coils M 1( and M 2 , are in any inter- 
mediate position, the inductive electromotive 
force produced in the telephone circuit can, if 
the value of R, be changed, be made to balance 
the impulsive electromotive force due to the in- 
ductance of P, and the value of this latter can, 
therefore, be inferred. 

Bridge, Magnetic An apparatus in- 
vented by Edison for measuring magnetic 
resistance, similar in principle to Wheatstone's 
electric bridge. 

The magnetic bridge is based on the fact that 
two points at the same magnetic potential, when 
connected, fail to produce any action on a mag- 
netic needle. The magnetic bridge consists, as 
shown in Fig. 82, of four arms or sides made of 




Fig. 82. Magnetic Bridge. 

pure, soft iron. The poles of an electro-magnet 
are connected to projections at the middle of 
the short side of the rectangle. By this means 
a difference of magnetic potential is main- 
tained at these points. The two long sides are 
formed of two halves each, which form the four 
arms of the balance. Two of these only are 
movable. 

Two curved bars of soft iron, of the same area 
of cross-section as the arms of the bridge, rest on 
the middle of the long arms, in the arched shape 
shown. Their ends approach near the top of the 



Bri.] 



62 



[Briu 



arch within about a half inch. A space is hol- 
lowed out between these ends, for the reception of 
a short needle of well-magnetized hardened steel, 
suspended by a wire from a torsion head. 

The movements of the needle are measured on 
a scale by a spot of light reflected from a mirror. 

The electro-magnet maintains a constant dif- 
ference of magnetic potential at the two shorter 
ends of the rectangle. If, therefore, the four 
bars, or arms of the bridge, are magnetically 
identical, there will be no deflection, since no 
difference of potential will exist at the ends of the 
bars between which the needle is suspended. If, 
however, one of the bars or arms be moved even 
a trifle, the needle is at once deflected, the motion 
becoming a maximum when the bar is entirely 
removed. If replaced by another bar, differing 
in cross-section, constitution, or molecular struc- 
ture, the balance is likewise disturbed. 

The magnetic bridge is very sensitive. It was 
designed by its inventor for testing the magnetic 
qualities of the iron used in the construction of 
dynamo-electric machines. 

Bridge Method of Duplex Telegraphy.— 

(See Telegraphy, Duplex ; Bridge Method 
of) 

Bridge Method of Quadruplex Teleg- 
raphy. — (See Telegraphy, Quadruplex, 
Bridge Method of.) 

Bridge, Metre A slide form of 

Wheatstone's electric bridge, in which the 
slide wire is one metre in length. (See 
Bridge, Electric, Slide Form of.) 

Bridge, Resistance —A term some- 
times applied to an electric bridge or balance. 
(See Bridge, Electric.) 

Bridge, Reversible A bridge or 

balance so arranged that the proportionate 
coils can be readily interchanged, thus per- 
mitting the bridge coils to be readily tested by 
reversing. 

Bridge, Wheatstone's Electric 



A name given to the electric bridge or balance. 
(See Bridge, Electric) 

Bridges. — Heavy copper wires suitably 
shaped for connecting the dynamo-electric 
machines in an incandescent light station to 
the bus-rods or wires. 



Bright Dipping. — (See Dipping, Bright) 
Bright Dipping Liquid. — (See Liquid, 
Bright Dipping.) 

Britannia Joint. — (See Joint, Britannia) 
Broken Circuit. — (See Circuit, Broken) 

Bronzing, Electro Coating a sur- 
face with a layer of bronze by electro-plating. 
(See Plating, Electro) 

The plating bath contains a solution of tin and 
copper. 

Brush-and-Spray Discharge. — (See Dis- 
charge, Brush-and-Spray) 

Brush Discharge. — (See Discharge, 
Brush) 

Brush Electrode. — (See Electrode, Brushy 

Brush, Faradic An electrode in 

the form of a brush employed in the medical 
application of electricity. 

The bristles are generally made of nickelized 
copper wire. 

Brush-Holders for Dynamo-Electric Ma- 
chines. — Devices for supporting the collecting 
brushes of dynamo-electric machines. 

As the brushes require to be set or placed on 
the commutator in a position which often varies 
with the speed of the machine, and with changes 
in the resistance of the external circuit, all brush - 
holders are provided with some device for moving 
them concentrically with the commutator cylin- 
der. 

Brush Rocker. — (See Rocker, Brush) 

Brush, Scratch ■ — A brush made 

of wire or stiff bristles, etc., suitable for clean- 
ing the surfaces of metallic objects before 
placing them in the plating bath. 

Scratch brushes are made of various shapes and 
are provided with wires or bristles of varying 
coarseness. 

Some forms of scratch and finishing brushes 
are shown in Fig. 83. They are circular in outline 




Fig. 8 J. Scratch Brushes. 

and are adapted for use in connection with a 
lathe. 



Bru.] 



63 



[Bui, 



Brush, Scratch, Circular — A 

scratch brush of a circular shape, so fitted as 
to be capable of being placed in a lathe and 
set in rapid rotation. 

Brush, Scratch, Hand A scratch 

brush operated by hand, as distinguished 
from a circular scratch brush operated by a 
lathe. 

Brushes, Adjustment of Dynamo-Electric 

Machines Shifting the brushes into 

the required position on the commutator 
cylinder, either non-automatically by hand, or 
automatically by the current itself. (See 
Reg2ilatio?i, Automatic, of Dynamo-Electric 
Machines') 

Brushes, Carbon, for Electric Motors 

Plates of carbon for leading current 

to electric motors. (See Brushes of Dynamo- 
Electric Machine) 

These are generally known simply as brushes. 

Brushes, Collecting, of Dynamo-Electric 

Machine Conducting brushes which 

bear on the commutator cylinder, and take off 
the current generated by the difference of 
potential in the armature coils. (See Brushes 
of Dynamo-Electric Machine) 

Brushes, Lead of The angle through 

which the brushes of a dynamo-electric ma- 
chine must be moved forward, or in the 
direction of rotation, in order to diminish 
sparking and to get the best output from 
the dynamo. 

The necessity for the lead arises from the coun- 
ter magnetism or magnetic reaction of the arma- 
ture, and the magnetic lag of its iron core. (See 
Lead, Angle of.) 

The position of the brushes on the commutator 
to insure the best output is practically the same 
in a series dynamo for any current strength. 
In shunt and compound dynamos it varies with 
the lead. 

Brushes of Dynamo-Electric Machine- 
Strips of metal, bundles of wire, slit plates of 
metal, or plates of carbon, that bear on the 
commutator cylinder of a dynamo-electric 
machine, and carry off the current generated. 

Rotary brushes consisting of metal discs are 
sometimes employed. Copper is almost univer- 



Fig. 84, is formed of 

,B 




Brtishes, 



sally used for the brushes of dynamo-electric 
machines. Carbon brushes are often used for 
dynamo-electric motors. 

The brush shown at B, 
copper wires, soldered 
together at the non- 
bearing end. A copper 
plate, slit at the bear- 
ing end, is shown at C, 
and bundles of copper 
plates, soldered together 
at the non-bearing end, 
are shown at D. 

The brushes should 
bear against the com- 
mutator cylinder with 
sufficient force to pre- 
vent jumping, and con- 
sequent burning, and 
yet not so hard as to 
cause excessive wear. 

Brushes, Rotating", of Dynamo-Electric 

Machines Discs of metal, employed 

in place of the ordinary brushes for carry- 
ing off the current from the armatures of 
dynamo-electric machines. 

Brushing 1 , Scratch Cleansing the 

surface of an article to be electroplated, by 
friction with a scratch brush. 

Scratch brushing is generally done with the 
brushes wet by various solutions. 

Buckling'. — Irregularities in the shape of 
the surfaces of the plates of storage cells, fol- 
lowing a too rapid discharge. 

Bug". — A term originally employed in quad- 
ruplex telegraphy to designate any fault in 
the operation of the apparatus. 

This term is now employed, to a limited extent, 
for faults in the operation of any electric appa- 
ratus. 

Bug-Trap. — A device employed to over- 
come the " bug " in quadruplex telegraphy. 

Bulb, Lamp — The chamber or 

globe in which the filament of an incan- 
descent electric lamp is placed. 

The chamber or globe of a lamp must be of 
such construction as to enable the high vacuum 
necessary to the operation of the lamp to be main- 
tained. 



Ban.] 



64 



[Bur. 



Bunched Cable.— (See Cable, Bunched?) 
Bunched Cable, Straightaway — 

(See Cable, Bunched, Straightaway?) 

Bunched Cable, Twisted — (See 

Cable, Bunched, Twisted?) 

Bunsen Voltaic Cell. — (See Cell, Voltaic, 
Buns en's?) 

Buoy, Electric A buoy on which 

luminous electric signals are displayed. 

Burglar Alarm.— (See Alarm, Burglar?) 

Burglar Alarm Annunciator. — (See An- 
nunciator, Burglar Alarm?) 

Burglar Alarm Contacts. — (See Contacts, 
Burglar Alarm?) 

Burglar Alarm, Tale Lock Switcli for — 
— (See Alarm, Yale-Lock-Switch Burglar?) 

Burner, Argand Electric An ar- 

gand gas-burner that is lighted by means of 
an electric spark. 

The argand electric burner assumes a variety 
of forms, such as the plain-pendant, the ratchet- 
pendant and the automatic. They are also used 
in systems of multiple gas lighting. 

Burner, Argand Electric, Automatic 

— An argand burner arranged for automatic 
electric lighting. (See Burner, Automatic- 
Electric?) 

Burner, Argand Electric, Hand-Lighter 

— A plain-pendant electric burner 

adapted for lighting an argand gas-burner. 
(See Burner, Plain-Pendant Electric.) 

Burner, Argand-Electric, Plain-Pendant 

— A plain-pendant electric burner 

adapted for lighting an argand gas burner. 
(See Burner, Plain-Pendant Electric?) 

Burner, Argand-Electric, Ratchet-Pend- 
ant A ratchet-pendant electric burner 

adapted for lighting an argand gas-burner. 
(See Burner, Ratchet-Pendant Electric?) 

Burner, Automatic-Electric An 

electric device for both turning on the gas 
and lighting it, and turning it off, by alter- 
nately touching different buttons. 

The gas-cock is opened or closed by the motion 
of an armature, the movements of which are con- 
trolled by two separate electro-magnets. One 
push-button, usually a white one, turns the gas on 




by energizing one of the electro-magnets and, 
at the same time, lights it by means of a suc- 
cession of sparks from a spark coil. Another 
push-button, usually a black one, turns the gas 
off by energizing the other electro-magnet. 
The turning on or off of the gas is accom- 
plished by positive 
motions. Automatic 
burners are also made 
with a single button. 

An Argand Electric 
Burner is shown in 
Fig. 85. 

Burner, Electric 

Candle —A 

device for electri- 
cally lighting a gas 
jet in a burner sur- 
rounded by a por- 
celain tube in imita- 
tion of a candle. 

Electric candle bur- 
ners are either simple 
or ratchet candle bur- 
ners. 

Burner, Hand- Fi s- 85- 
Lighting Electric 
A name sometimes applied to a plain- 
pendant electric burner. (See Burner, Plain- 
Pendant Electric?) 

Burner, Jump-Spark A term 

sometimes applied to a gas burner in which 
the issuing gas is ignited 
by a spark that jumps be- 
tween the metallic points \\ | |||| ^Jcjfr L 
placed on it. 

Jump -spark burners are 
used in systems of multiple 
gas lighting. (See Light- £ Q 

ing, Electric Gas.) 

Burner, Plain-Pen- 
dant Electric A 

gas - burner provided 

with a pendant for the 

purpose of lighting the 

gas by means of a spark, pig. s6. Plain- Pendant 

after the gas has been Burner. 

turned on by hand. 

The gas is first turned on by hand at the ordi- 



Argand Electric 
Burner, 




Bur.] 



65 



[But. 



nary key, and is then lighted by pulling the pend- 
ant C, Fig. $6. A spark from a spark coil ignites 
the gas. 

This is sometimes called an electric hund- 
lighting burner. 

Burner, Ratchet-Pendant Candle Elec- 
tric A burner for both lighting and 

extinguishing a candle gas jet. 

Burner, Ratchet-Pendant Electric 

— A gas-burner in which one pulling of a 
pendant turns on the gas and ignites it by 
means of an electric spark from a spark coil, 
and the next pulling of the pendant turns off 
the gas. 

A ratchet-wheel and pawl are operated by the 
motion of the pendant. The first pull of the 
pendant chain moves the ratchet so as to open a 
four-way gas cock, and at the same time light 
the gas at the burner tip by a wipe-spark from a 
spark coil. On the next pull ot the pendant, the 
four- way cock is turned so as to turn off the g?s. 
Alternate pulls, therefore, light and extinguish 
the gas. 

Burner, Simple Candle Electric 

A plain-pendant electric burner. (See Bur- 
7ier, Plain Pendant Electric.) 

Burner, Thumb-Cock Electric 

An electric gas- 
burner, in which 
the turning of an 
ordinary thumb- 
cock turns on the 
gas, and ignites it 
by a spark pro- 
duced by a wiping 
contact actuated 
by the motions of 
the thumb-cock. 
A form of thumb- 
cock burner is 
shown in Fig. 87. 

Burner, Vi- 
brating - E 1 e c - 

trie — — An Fig. 87. Thumb- Cock Burner. 

electric gas-burner in which the gas is lighted 
after it is turned on by hand, by means of the 
spark from a spark coil produced on the rapid 




making and breaking of the circuit by a 
vibrating contact. 

The vibrating-electric burner has a single elec- 
tro-magnet. It is operated by means of a button 
or switch, and may be used on single lights or on 
groups of lights. It bears the same relation to 
the automatic burner that the plain-pendant 
burner does to the ratchet burner. 

Burnetize. — To subject to the Burnetizing 
process. (See Burnetizing) 

Burnetizing". — A method adopted for the 
preservation of wooden telegraph poles by 
injecting a solution of zinc chloride into the 
pores of the wood. (See Pole, Telegraphic) 

Burning at Commutator of Dynamo. — 

An arcing at the brushes of a dynamo-elec- 
tric machine, due to their imperfect contact, 
or improper position, which results in loss of 
energy and destruction of the commutator 
segments. 

Bus. — A word generally used instead of 
omnibus. (See Omnibus.) 

Bus-Bars. — (See Bars, Bus.) 

Bus-Rod Wires. — (See Wires Bus-Rod.) 

Bus- Wire. — (See Wire, Bus) 

Butt Joint. — (See Joint, Butt) 

Button, Carbon — A resistance of 

carbon in the form of a button. 

A button of carbon is used as an electric resist- 
ance in a variety of apparatus; its principal use, 
however, is in the transmitting instrument of the 
electric telephone. In the telephone transmitter, 
the button is so placed between contact-plates that 
when the plates are pressed together by the 
sound-waves, the electrical resistance is decreased 
by a decrease in the thickness of the carbon button, 
an increase in its density, and an increase in the 
number of points where the carbon touches the 
plates. Rheostats, or resistances, have been 
made by the use of a number of carbon buttons or 
discs piled one on another and placed in a glass 
tube. Discs of carbonized cloth form excellent 
resistances ior such purposes. 

Button, Press A push button. 

(See Button, Push) 

Button, Push A device for closing 



But.] 



66 



[Cab. 



in electric circuit by the movement of a Buzzer, Electric A call, not as 

button. loud as that of a bell, produced by a rapid 

A button, when pushed by the hand, closes the 






Fig. 88. Push Button. Fig. 8q 

contact, and thus completes a circuit in which 
some electro -receptive device is placed. This 
circuit is opened by a spring, 
on the removal of the pressure. 
Some forms of push-buttons are 
shown in Figs. %%, 89 and 90. 

A floor-push for dining-rooms 
and offices is shown in Fig. 
90. 

Fig. 88 shows the general 
appearance of an ordinary bell- 
push. The arrangement of the 
interior spring contacts will be 
understood by an inspection of Fig. 91 



Fig. Q t. Spring Contact of Bell Push. 

automatic make-and-break. (See Make-and- 
Break, Automatic.) 

The buzzer is generally pk ced inside a resonant 





Fig. qo. Floor 
Push. 



Fig. Q2. Buzzer. 

case of wood in order to strengthen the sound by 
resonance. A form of buzzer is shown in Fig. 92. 



C. — An abbreviation for centigrade. 

^hus, 20 degrees C. means 20 degrees of the 
centigrade thermometric scale. (See Scale, Cen- 
tigrade Thermometer.) 

C. — A contraction for current. 

Generally a contraction for the current in 

r E 
amperes, as C = ^. 

C. C. — A contraction for cubic centimetre. 
(See Weights and Measures, Metric System 
of.) 

C. G. S. Units.— A contraction for centi- 
timetre-gramme-second units. (See Units, 
Centi7netre-Gratnme- Second.) 



C. P. — A contraction for candle power. 
(See Candle, Standard?) 

Cable. — An electric cable. (See Cable, 
Electric?) 

Cable. — To send a telegraphic dispatch, 
by means of a cable. 

Cable, Aerial A cable suspended 

in the air from suitable poles. 

Cable, Anti-Induction, Waring 

A form of anti-induction cable. 

In the Waring an ti- induction cable the separate 
conductors are covered with a fibrous insulator, 
from which all air and moisture is expelled, and 
the fibre then saturated with an insulating ma- 



Cab.] 



67 



[Cab. 



terial called ozite. The conductors are then pro- 
tected from the inductive effects of neighboring 
conductors by a continuous sheath of lead alloyed 
with tin. 

Where the cables are bunched, the bunches 
are sometimes again surrounded by insulating 
material, and the whole then covered by a con- 
tinuous lead sheathing ; generally, however, the 
separately insulated conductors are bunched, 
and then covered by a single sheathing of lead 
alloyed with tin. 

Cable, Armature of The armor of 

a cable. (See Armature of a Cabled 

Cable, Armor of The protecting 

sheathing or metallic covering on the outside 
of a submarine or other .electric cable. 

Cable, Armored An electric cable 

provided, in addition to its insulating coat- 
ing, with a protective coating or sheathing, 
generally of metal tubing or wire. 

Cable-Box.— (See Box, Cabled 

Cable, Bunched A cable contain- 
ing more than a single wire or conductor. 

Some forms of bunched, lead-covered cables, 
are shown in Fig. 93. 




Fig- 93' Bunched Cables. 

Cable, Bunched, Straightaway — 

A bunched cable the separate conductors of 
which extend in the direction of the length of 
the cable without any twisting, being placed 
in successive layers. 

In arranging the separate conductors in suc- 
cessive layers an advantage is gained in testing 
for a given wire in order to make a loop, splice, 
or branch with the next adjoining section. This is 
rendered still easier by giving the conductors 
of the successive layers some distinctive form of 
braiding in the fibrous insulating material, or 
some distinctive color. 

Cable, Bunched, Twisted —A 

bunched cable, the separate conductors of 
which are twisted-pairs placed in successive 
layers. 



Each twisted-pair of a bunched cable acts as a 
metallic circuit, and, moreover, possesses the ad- 
vantage of avoiding the ill effects of induction, so 
disadvantageous in telephone circuits. 

In laying up the twisted-pairs in successive 
layers in a bunched cable, the direction of twist- 
ing is reversed in each successive layer. This 
form is especially desirable on all long cable lines. 

In the case of twisted cables for telephone lines, 
the twists are sometimes made as frequent as one 
in every three or four inches. In such cases the 
cross-talk of induction is inappreciable. 

Cable, Capacity of The quantity 

of electricity required to raise a given length 
of a cable to a given potential, divided by the 
potential. 

The amount of charge for a given potential 
that any single conductor will take up with 
the rest of the conductors grounded. (See 
Capacity, Electrostatic?) 

The ability of a wire or cable to permit a 
certain quantity of electricity to be passed 
into it before acquiring a given difference of 
potential. 

Before a telegraph line or cable can transmit a 
signal to its further end, its difference of potential 
must be raised to a definite amount dependent on 
the character of the instruments and the nature of 
the system. 

The first effect of electricity being passed into a 
line is to produce an accumulation of electricity 
on the line, similar to the charge in a condenser. 
Cables especially act as condensers, and from the 
high specific inductive capacity of the insulating 
materials employed, permit considerable induc- 
tion to take place between the core and the 
metallic armor or sheathing, or the ground. 

The capacity of a cable depends on the capacity 
of the wire ; i. e., on its length and surface, on 
the specific inductive capacity of its insulation, 
and its neighborhood to the earth, or to other 
conducting wires, casings, armors, or metallic 
coatings. Submarine or underground cables 
therefore have a greater capacity than air lines. 

This accumulation of electricity produces a re- 
tardation in the speed of signaling, because the 
wire must be charged before the signal is received 
at the distant end, and discharged or neutralized 
before a current can be sent in the reverse direc- 
tion. This latter may be done by connecting 
each end to earth, or by the action of the reverse 
current itself. 



Cab.] 



68 



[Cab. 



The smaller the electrostatic capacity of a cable, 
therefore, the greater the speed of signaling . (See 
Retardation.) 

The capacity of a cable is measured in micro- 
farads. (See Farad, Micro.) 

Cable Clip.— (See Clip, Cable.) 

Cable-Core. — (See Core of Cabled) 

Cable, Core-Ratio of The ratio be- 
tween the diameter of the insulation of a cable 
and the mean diameter of the strand. 

D 
The core-ratio is represented by -p where D, 

is the diameter of the insulation, and d, the mean 
diameter of the strand. Should the extreme 
diameter of the strand of a cable be used in cal- 
culations for insulation resistance, inductive capa- 
city, etc., erroneous values would be obtained. 
The measured diameter of the copper conductor 
is consequently decreased some five per cent., and, 
in this way, correct values are approximately 
obtained. — [Clark 6° Sabine.) 

Cable, Duplex A conductor con- 
sisting of two separate cables placed parallel 
to each other. 

The duplex cable is used especially in the al- 
ternating current system. 

Cable, Electric The combination 

of an extended length of a single insulated 
conductor, or two or more separately insu- 
lated electric conductors, covered externally 
with a metallic sheathing or armor. 

Strictly speaking, the word cable should be 
limited to the case of more than a single con- 
ductor. Usage, however, sanctions the employ- 
ment of the word to indicate a single insulated 
conductor. 

The conducting wire may consist of a single 
wire, of a number of separate wires electrically 
connected, or of a number of separate wires in- 
sulated from one another. 

An electric cable consists of the following parts, 
viz.: 

(i.) The conducting wire or core. 

(2.) The insulating material for separating the 
several wires; and 

(3.) The armor or protecting covering, consist- 
ing of strands of iron wire, or of a metallic coat- 
ing or covering of lead. 

As to their position, cables are aerial, sub- 
marine, or underground. As to their purpose, 



they are telegraphic, telephonic, or electric light 
and power cables. As to the number of their 
conductors they are single -wire or bunched 
cables. Bunched cables are straightaway or 
twisted. 

Fig. 94 shows a form of submarine cable the 




Fig. Qj.. Electric Cable. 

armor of which is formed of strands of iron 
wire. 

Cable, Electric Light or Power 

A cable designed to distribute the electric cur- 
rent employed in electric light or power sys- 
tems. 

Electric light cables are generally underground. 
They may be submarine. (See Cable, Electric.) 

Cable, Flat A cable, the separate 

conductors of which are laid-up side by side 
so as to form a flat conductor. 

A flat cable is suitable for house work as being 
less objectionable in appearance when placed on 
the outside of ceilings or walls. 

Cable, Flat Duplex A flat, laid-up 

cable containing two wires. 

Cable-Grip.— (See Grip, Cabled 

Cable-Hanger. — (See Hanger, Cabled) 

Cable-Hanger Tongs. — (See Tongs, Cable- 
Hanger.) 

Cable Laid-Up in Layers. — A term applied 
to a cable, all the conducting wires of which 
are in layers. 



Cab.] 



69 



[Cab. 



Cable Laid-rp in Reversed Layers.— A 

term applied to a cable in which the conduct- 
ors, in alternate layers, are twisted in opposite 
directions. (See Cable, Bunched, Straight- 
away^) 

Cable Laid-Up in Twisted Pairs. — A term 
applied to a cable in which every pair of wires 
is twisted together. (See Cable, Bunched, 
Twisted?) 

Cable Lead. — (See Lead, Cable). 

Cable, Multiple-Core A cable con- 
taining more than a single core. 

Cable-Protector.— (See Protector, Cable.) 

Cable-Serving. — (See Serving, Cabled) 

Cable, Single-Wire A cable con- 
taining a single wire or conductor. 

Cable, Sub-Aqueous An electric 

cable designed for use under water. 

The term submarine is more frequently em- 
ployed. 

Cable, Submarine A cable designed 

for use under water. 

-• 
Submarine cables are either shallow-water, or 

deep-sea cables. Gutta-percha answers admirably 

for the insulating material of the core. Various 

other insulators are also used. 

Strands of tarred hemp or jute, known as the 
cable-serving, are wrapped around the insulated 
core in order to protect it from the pressure of the 
galvanized iron wire armor afterwards put on. 
To prevent corrosion the iron wire is covered 
with tarred hemp, galvanized, or otherwise 
coated. 

Submarine cables are generally employed for 
telegraphic or telephonic communication. (See 
Cable, Electric I) 

Cable, Submarine, Deep-Sea A 

submarine cable designed for use in deep 
water. 

This form of cable is not so heavily armored as 
the shallow-water submarine cable. 

Cable, Submarine, Shallow- Water . 

A submarine cable designed for use in shallow 
water. 

This cable is provided with, a heavier armor or 
sheathing than a deep-sea cable to protect it 
from chafing due to the action of the waves and 
tides in shallow water. [See Cable. Submarine.'-, 



Cable Support, Underground (See 

Support, Underground Cable.) 

Cable Tank.— (See Tank, Cable) 

Cable, Telegraphic A cable de- 
signed to establish telegraphic communication 
between different points. 

Telegraphic cables may be aerial, submarine, 
or underground. (See Cable, Electric-) 

Cable, Telephonic A cable de- 
signed to establish telephonic communication 
between different points. 

Telephonic cables may be aerial, submarine, 
or underground. (See Cable, Electric.) 

Cable-Terminal. — (See Terminal, Cabled 

Cable, Torpedo A cable, in the 

circuit of which a torpedo is placed. (See 
Torpedo, Electric?) 

Cable, Twisted-Pair A cable 

containing a single twisted pair, suitable for 
use as a lead and return, thus affording a 
metallic circuit. 

Cable, Two, Three, Four, etc., Conductor 

A cable containing two, three, four, 

or more separate conducting wires. 

Cable, Underground An electric 

cable placed underground. 

The conducting wires of an underground cable 
are surrounded by a good insulating, water-proof 
substance, and protected by a sheathing or armor. 
A coating of lead is very generally employed for 
the sheathing or armor. Underground cables, in 
order to be readily accessible, should be placed 
in an underground conduit or subway. (See 
Cable, Electric, Conduit, Underground Electric. 
Subway, Electric.) 

Cable-Worming.— (See Worming, Cable) 

Cablegram. — A message received by means 
of a submarine telegraphic cable. 

Cables, Laying-Up The placing or 

disposing of the separate cables or conduc- 
tors in a bunched cable. 

The separate conductors in cables may be laid- 
up iC straightaway " or "■twisted." (See Cable, 
Bunched, Twisted. Cable, Bunched, Straight- 
away. ) 

Cabling. — Sending a telegraphic cizpatch 
bv means of a cable. 



€al.] 



70 



[Cal. 



Calahan's Stock Printer. — (See Printer, 
Stock, Calahan's.) 

Calamine, Electric A crystalline 

variety of silicate of zinc that possesses pyro- 
electric properties. (See Electricity, Pyro.) 

Cal-Electricity. — (See Electricity, Cal.) 

Calibrate. — To determine the absolute 
or relative value of the scale divisions, or of 
the indications of any electrical instrument, 
such as a galvanometer, electrometer, vol- 
tameter, wattmeter, etc. 

Calibrating". — The act of determining the 
absolute or relative value of the deflections, 
or indications of an electric instrument. 

Calibration, Absolute The deter- 
mination of the absolute values of the read- 
ing of an electrometer, galvanometer, volt- 
meter, amperemeter, or other similar instru- 
ment. 

The calibration of a galvanometer, for ex- 
ample, consists in the determinatior of the law 
which governs its different deflections, and by 
which is obtained in amperes, either the absolute 
or the relative currents required to produce such 
deflections. 

For various methods of calibration, see stan- 
dard works on electrical testing, or on elec- 
tricity. 

Calibration, Invariable, of Galvanom- 
eter In galvanometers with absolute 

calibration, a method for preventing the oc- 
currence Of variations in the intensity of the 
field of the galvanometer, due to the neigh- 
borhood of masses of iron, etc. 

Calibration, Relative The deter- 
mination of the relative values of the reading 
of an electrometer, voltmeter, amperemeter, 
or other similar instrument. 

Caliper, Mi- .Be 

H 



crometer 

—A name some- 
times given to a 
vernier wire 
gauge. (See 
Gauge, Vernier 

Wire?) Fig, 95. Microrneter Caliper. 

A form of micrometer caliper is shown in Fig. q<,. 




Call-Bell, Extension (See Pell, 

Extension Call) 
Call-Bell, Magneto-Electric An 

electric call-bell operated by currents pro- 
duced by the motion of a coil of wire before 
the poles of a permanent magnet. 

A well known form of magneto call-bell is shown 




Fig. qb. Magneto Call Bell. 

in Fig. 96. The armature is driven by the rota- 
tion of the handle. 

Call-Bell, Telephone An electric 

bell, the ringing of which is used to call a 
person to a telephone. 

Call, Electric Bell — An electric 

bell sometimes used to call the attention of an 
operator to the fact that his correspondent 
wishes to communicate with him, or to notify 
an attendant that some service is desired. 

Call, Messenger — A district call- 
box. (See Pox, District Call) 

Call, Thermo-Electric An instru- 
ment for sounding an alarm when the tem- 
perature rises above, or falls below, a fixed 
point. 

In one form of thermo-electric call a needle is 
moved over a dial by a simple thermic device and 
rings a bell when the temperature for which it 
has been se is attained. The thermo-call is appli- 
cable to the regulation of the temperature oi 



Cal.] 



71 



[Cal. 



dwellings, incubators, hot houses, breweries, dry- 
ing rooms, etc. 

Callaud Yoltaic Cell.— (See Cell, Vol- 
taic, Callaud' s.) 

Calling-Drop. — (See Drop, Calling.) 

Calorescence. — The transformation of 
invisible heat-rays into luminous rays, when 
received by certain solid substances. 

The term was proposed by Tyndall. The light 
from a voltaic arc is passed through a hollow 
glass lens filled with a solution of iodine in bisul- 
phide of carbon. 

This solution is opaque to light but quite trans- 
parent to heat. 

If a piece of charred paper, or thin platinum 
foil, is placed in the focus of these invisible rays, 
it will be heated to brilliant incandescence. (See 
Focus.) 

Caloric. — A term formerly applied to the 
fluid which was believed to be the cause or 
essence of heat. 

The use of the word caloric at the present time 
is very unscientific, since heat is now known to 
be an effect of a wave motion and not a material 
thing. {See. Heat.) 

Calorie. — A heat unit. 

There are two calories, the small and the large 
calorie. 

The amount of heat required to raise the tem- 
perature of one gramme of water from o degree 
C. to I degree C. is called the small calorie. 

The amount of heat required to raise 1,000 
grammes, or a kilogramme, of water from o de- 
gree C. to i degree C. is called the great calorie. 
The first usage of the word is the commoner. 

This word is sometimes spelled calory. 

Calorie, Great — The amount of 

heat required to raise the temperature of one 
kilogramme of water from o degree C. to I 
degree C. 

Calorie, Small —The amount of 

heat required to raise the temperature of one 
gramme of water from o degree C. to I 
degree C. 

Calorimeter. — An instrument for measur- 
ing the amount of heat or thermal energy 
contained or developed in a given body. 

Thermometers measure temperature only. A 



thermometer plunged in a cup full of boiling 
water shows the same temperature that it would 
in a tub full of boiling water. The quantity of 
heat energy present in the two cases is of course 
greatly different, and can be measured by a cal- 
orimeter only. 

Various forms of calorimeters are employed. 

In order to determine the quantity of heat in 
a given weight of any body, this weight may be 
heated to a definite temperature, such as the boil- 
ing point of water, and placed in a vessel con- 
taining ice. The quantity of ice melted by the 
body in cooling to the temperature of the ice, is 
determined by measuring the amount of water 
derived from the melting of the ice. Care must 
be observed to avoid the melting of the ice by ex- 
ternal heat. 

In this way the amount of heat required to 
raise the temperature of a given weight of a body 
a certain number of degrees, or the capacity of 
the body for heat, may be compared with the 
capacity of an equal weight of water. This ratio 
is called the specific heat. (See Heat, Specific.) 

The heat energy, present in a given weight of 
any substance at a given temperature, can be de- 
termined by means of a calorimeter; for, since a 
pound of water heated l°F. absorbs an amount 
of energy equal to 772 foot-pounds, the energy can 
be readily calculated if the number of pounds of 
water and the number of degrees of temperature 
are known. (See Heat, Mechanical Equivalent 
of) 

Calorimeter, Electric — An instru- 
ment for measuring the heat developed in a 
conductor or any piece of electrical apparatus, 
in a given time, by an electric current. 




Fig. gj. Electric Calorimeter. 

A vessel containing water is provided with a 
thermometer T, Fig. 97. The electric current 



lal.] 



72 



[Can, 



passes for a measured time through a wire im- 
mersed in the liquid. 

The quantity of heat is determined from the 
increase of temperature, and the weight of the 
water heated. 

According to Joule, the number of heat units 
developed in a conductor by an electric current 
is proportional: 

(i.) To the resistance of the conductor. 

(2.) To the square of the current passing. 

(3.) To the time the current is passing. 

(See Heat Unit, English.) 

The heating power of a current is as the square 
of the current only when the resistance remains 
the same. (See Heat, Electric.) 

Calorimetric. — Pertaining to or by means 
of the calorimeter. 

Calorimetric measurement is the measurement 
of heat energy made by means of the calorimeter. 
(See Calorimeter.) 

Calorimetrically. — In a calorimetric man- 
ner. 

Calorimetric Photometer. — (See Photom- 
eter, Calorimetric.) 

Calorimotor. — A name applied to a defla- 
grator. (See Defiagrator? 

Calory. — A term used for calorie. 

Calorie is the preferable orthography, (See 
Calorie.) 

Cam, Electro-Magnetic — A form 

of magnetic equalizer, which depends for its 
operation on the lateral approach of a suita- 
bly shaped polar surface. (See Equalizer* 
Magnetic?) 

Cam, Listening In a telephone 

exchange system, a metallic cam by means of 
which an operator is placed in circuit with 
a subscriber. 

Candle. — The unit of photometric intensity. 

Such a light as would be produced by the 
consumption of two grains of a standard 
candle per minute. 

An electric lamp of 16 candle-power, or one of 
2,000 candle-power, is a light that gives respect- 
ively 16 or 2,000 times as much light as one stand- 
ard candle. 

Candle Burner, Electric (See Bur- 
ner, Electric Candle?) 



Candle, Electric A term applied 

to the Jablochkoff candle, and other similar 
devices. (See Candle, Jablochkoff *.) 

Candle, Foot A unit of illumina- 
tion equal to the illumination produced by a 
standard candle at the distance of 1 foot. 

According to this unit, the illumination pro- 
duced by a standard candle at the distance of 
2 feet would be but the one -fourth of a foot- 
candle; at 3 feet, the one-ninth of a foot-candle, 
etc. 

The advantage of the proposed standard lies in 
the fact that knowing the illumination in foot- 
candles required tor the particular work to be 
done, it is easy to calculate the position and 
intensity of the lights required to produce the 
illumination. 

Candle, JaMockkoff An electric 

arc light in which the two carbon electrodes are 
placed parallel to each other and maintained 
a constant distance apart by means of a sheet 
of insulating material placed between them. 

The Jablochkoff electric candle consists of two 
parallel carbons, separated by a layer of kaolin or 
other heat-resisting insulating material, as shown 
in Fig. 98. The current is passed into and out of 
the carbons at one end of the 
candle, and forms a voltaic arc at 
the other end. In order to start 
the arc, a thin strip called the 
igniter, consisting of a mixture of 
some readily ignitable substance, 
connects the upper ends of the 
carbons. 

An alternating current is em- 
ployed with these candles, thus 
avoiding the difficulty which Fi ?' <> s > Ja - 
would otherwise occur from the oc °^ an ' 
more rapid consumption of the positive than the 
negative carbon. (See Current \ Alternating.) 

Candle, Metre The illumination pro- 
duced by a standard candle at the distance of 
one metre. (See Candle, Foot?) 

Candle-Power. — (See Power, Candle) 

Candle-Power, Rated (See Power, 

Candle, Rated.) 

Candle • Power, Spherical (See 

Power, Candle, Spherical) 

Candle, Standard — 




-A candle of 



Cao.] 



[Cap. 



definite composition which, with a given con- 
sumption in a given time, will produce a light 
of a fixed and definite brightness. 

A candle which burns 120 grains of sperma- 
ceti wax per hour, or 2 grains per minute, will 
give an illumination equal to one standard candle. 
Unless considerable care is taken, erroneous re- 
suits will be obtained from the use of the stand- 
ard candle. According to Slingo and Brooker 
the following are among the most important 
causes of these errors : 

(1.) Defective forms of candle which cause a 
varying consumption of the material per second, 
and consequently a varying light for the standard 
candle. 

(2. ) Variations in the composition of the sper- 
maceti of which the candle is composed. Sper- 
maceti is not a definite chemical compound, but 
consists of a mixture of various substances ; 
therefore, even if the consumption is maintained 
constant, the light-giving power is not necessarily 
constant. 

(3.) Variations in the composition and charac- 
ter of the wick, such as the number and size of 
the threads of which it is formed and the closeness 
of the strands, all of which circumstances influence 
the amount of light given off by the candle. 

(4.) The light emitted in certain directions va- 
ries in a marked degree with the shape of the 
wick. The mere bending of a wick may, there- 
fore, cause the amount of light to vary consider- 
ably. 

(5.) The light varies with the thickness of the 
wick. Thick wicks give less light than thin 
wicks. 

(6.) The light given by the standard candle va- 
ries with the temperature of the testing-room. 
As the temperature rises the light given by the 
standard candle increases. 

(7.) Currents of air, by producing variations 
in the amount of melting wax in the cup of the 
candle, vary the amount of light emitted. 

These difficulties in obtaining a fixed amount of 
light from a standard candle, together with the 
difficulty of comparing the feeble light of a single 
candle with the light of a much more powerful 
source, such as an arc lamp, coupled with the 
additional difficulty arising from the difference in 
the colors of the lights, have led to the use of 
other standards of light than those furnished by 
the standard candle. 

Caoutchouc, or India-Rubber.— A resin- 



ous substance obtained from the milky juices 
of certain tropical trees. 

Caoutchouc possesses high powers of electric 
insulation, and is used either pure or combined 
with sulphur. 

Cap, Insulator A covering or cap 

placed some distance above an insulator, but 
separated from it by an air space. 

Insulator caps are intended for protection of the 
insulators from injury by the throwing of stones 
or other malicious acts. Insulator caps are gen- 
erally made of iron. They are highly objection- 
able, owing to the facility they offer for the ac- 
cumulation of dust and dirt. 

Capacity, Atomic The quantiva- 

lence or valency of an atom. (See Atomi- 
city^ 

Capacity, Dielectric A term em- 
ployed in the same sense as specific inductive 
capacity. (See Capacity, Specific Inductive) 

Capacity, Electro-Dynamic — A 

term formerly employed by Sir William 
Thomson for self-induction. (See Induction, 
Self) 

Capacity, Electrostatic The quan- 
tity of electricity which must be imparted to a 
given body or conductor as a charge, in order 
to raise its potential a certain amount. (See 
Potential, Electric) 

The electrostatic capacity of a conductor is not 
unlike the capacity of a vessel filled with a liquid 
or gas. A certain quantity of liquid will fill a 
given vessel to a level dependent on the size or 
capacity of the vessel. In the same manner a 
given quantity of electricity will produce, in a 
conductor or condenser, a certain difference of 
electric level, or difference of potential, dependent 
on the electrical capacity of the conductor or 
condenser. 

Or, taking the analogous case of a gas-tight 
vessel, the quantity of gas that can be forced into 
such a vesssl depends on the size of the vessel 
and the pressure with which it is forced in. A 
tension or pressure is thus produced by the gas 
on the walls of the vessel, which is greater the 
smaller the size of the vessel and the greater the 
quantity of gas forced in. 

In the same manner, the smaller the capacity 
of a conductor, the smaller is the charge required 



Cap.] 



n 



[Cap. 



lo raise it to a given potential, or the higher the 
potential a given charge will raise it. 

The capacity K, of a conductor or condenser, 
is therefore directly proportional to the charge Q, 
and inversely proportional to the potential V; or, 

K-2. 

V 

From which we obtain Q = KV; or, 

The quantity of electricity required to charge a 
conductor or condenser to a given potential is 
equal to the capacity of the conductor or condenser 
multiplied by the potential through which it is 
raised. 

Capacity, Electrostatic, Unit of — 

Such a capacity of a conductor or condenser 
that an electromotive force of one volt will 
charge it with a quantity of electricity equal 
to one coulomb. 

The farad. (See Farad) 

Capacity of Cable. — (See Cable, Capacity 
of.) 

Capacity of Condenser. — (See Condenser, 
Capacity of.) 

Capacity of Leyden Jar. — (See Jar, 
Leyden, Capacity of.) 

Capacity of Line. — (See Line, Capacity 

of) 

Capacity of Polarization of a Yoltaic 
Cell. — (See Cell, Voltaic, Capacity of Polar' 
ization of.) 

Capacity, Safe Carrying", of a Conductor 
— ■ — — The maximum electric current the 
conductor will carry without becoming unduly 
heated. 

Capacity, Specific Inductive — 

The ability of a dielectric to permit induction 
to take place through its mass, as compared 
with the ability possessed by a mass of air of 
the same dimensions and thickness, under 
precisely similar conditions. 

The relative power of bodies for trans- 
mitting electrostatic stresses and strains 
analogous to permeability in metals. 

The ratio of the capacity of a condenser 
whose coatings are separated by a dielectric 
of a given substance to the capacity of a 
similar condenser whose plates are separated 
by a plate or layer of air. 



The inductive capacity of a dielectric is com- 
pared with that of air. 

According to Gordon and others, the specific 
inductive capacities of a few substances, com- 
pared with air, are as follows: 

Air i.oo 

Glass 3-013 to 3.258 

Shellac 2.740 

Sulphur 2.580 

Gutta-percha 2.462 

Ebonite 2.284 

India-rubber 2.220 to 2.497 

Turpentine ...2.160 

Petroleum 2.030 to 2.070 

Paraffin (solid).. 1 L 994 

Carbon bisulphide 1.810 

Carbonic acid 1.00036 

Hydrogen 0/99967 

Vacuum 0.99941 

Faraday, who proposed the term specific in- 
ductive capacity, employed in his experiments a 
condenser consisting of a metallic sphere A, Fig. 
99, placed inside a large 
hollow sphere B. 

The concentric space 
between A and B was filled 
with the substance whose 
specific inductive capacity 
was to be determined. 

Capacity, Specific 

Magnetic A term 

sometimes employed in 
the sense of magnetic 
permeability. 

Conductibility for lines 
of magnetic force in the 
same sense that specific 
inductive capacity is con- 
ductibility for lines of 
electrostatic force. 

This term has received 
the name of specific mag- 
netic capacity in order to distinguish it from specific 
inductive capacity. The velocity of propagation 
of waves in any elastic medium is proportional to 
the quotient obtained by extracting the square 
root of the elasticity of the medium divided by 
the square root of its density ; or, 




Fig qq. Co7idenser. 



\D 



Cap. 



75 



[Car. 



Similarly, the speed with which inductive waves 
travel depends on the relation between the elas- 
ticity and the density of the medium. Calling = 

the electric elasticity, then its reciprocal, K, corre- 
sponds with the dielectric capacity. The elec- 
trical density, ju, corresponds with the magnetic 
permeability. The velocity of wave transmission 
is therefore, 



V 



^Kx/( 



Capacity, Storage, of Secondary Cell 

— (See Cell, Secondary or Storage, Capa- 
city of.) 

Capillarity. — The elevation or depression 
of liquids in tubes of small internal diameter. 

The liquid is elevated when it wets the walls, 
and depressed when it does not wet the walls of 
the tube. 

The phenomena of capillarity are due to the 
mutual attractions existing between the mole- 
cules of the liquid for one another, and the 
mutual attraction between the molecules of the 
liquid and those of the walls of the tube. 

In capillarity, therefore, the approximately 
level surface caused by the equal attraction of all 
the molecules towards the earth's centre is dis- 
turbed by the unequal attraction exerted on each 
molecule by the walls of the tube and by the re- 
maining molecules. 

Capillarity, Effects of, on Voltaic Cell 

Effects caused by capillary action 

which disturb the proper action of a voltaic 
cell. 

These effects are as follows: 

(i.) Creeping, or efflorescence of salts. (See 
Creepin*^ Electric. Efflorescence. ) 

(2.) Oxidation of contacts and consequent in- 
troduction of increased resistance into the battery 
circuit. The liquid enters the capillary spaces 
between the contact surfaces and oxidizes them. 

Capillary. — Of a small or hair-like diame- 
ter or size. 

A capillary tube is a tube of small hair-like di- 
ameter. (See Capillanty.) 

Capillary Attraction.— (See Attraction, 
Capillary) 



Capillary Contact-Key. — (See Key, Cap- 
illary Contact) 

Capillary Electrometer.— (See Electrom- 
eter, Capillary?) 

Carbon. — An elementary substance which 
occurs naturally in three distinct allotropic 
forms, viz.: charcoal, graphite and the dia- 
mond. (See Allotropy.) 

Carbon-Brushes for Electric Motors. — 

(See Brushes, Carbon, for Electric Motors?) 

Carbon Button. — (See Button, Carbon) . 
Carbon-Clutch or Clamp of Arc Lamp. 

— (See Clutch, Carbon, of Arc Lamp) 

Carbon-Electrodes for Arc Lamps. — (See 
Electrodes, Carbon, for Arc Lamps) 

Carbon-Holders for Arc Lamps. — (See 
Holders, Carbon, for Arc Lamps) 

Carbon Points. — (See Points, Carbon) 

Carbon Transmitter for Telephones.— 
(See Transmitter, Carbon, for Telephones) 

Carbonic Acid Gas. — (See Gas, Carbonic 
Acid) 

Carboning Lamps. — (See Lamps, Carbon- 
ing) 

Carbonizable. — Capable of being carbon- 
ized. (See Carbonization, Processes of) 

Carbonization. — The act of carbonizing, 
(See Carbonization, Processes of.) 

Carbonization, Processes of 

Means for carbonizing material. 

The carbonizable material is placed in suitably 
shaped boxes, covered with powdered plumbago 
or lamp-black, and subjected to the prolonged 
action of intense heat while out of contact with 
air. 

The electrical conducting power of the carbon 
which results from this process is increased by the 
action ot the heat, and, probably, also, by the de- 
posit in the mass, ot carbon resulting from the 
subsequent decomposition of the hydro-carbon 
gases produced during carbonization. 

When the carbonization is for the purpose of 
producing conductors for incandescent lamps, in 
order to obtain the unifo-mity of conducting 
power, electrical homogeneity, purity and high 
refractory power requisite, selected fibrous ma- 
terial, cut or shaped in at least one dimension 



Car.] 



'6 



[Car. 



prior to carbonization must be taken, and sub- 
jected to as nearly uniform carbonization as pos- 
sible. 

Carbonize. — To reduce a carbonizable ma- 
terial to carbon. (See Carbonization, Pro- 
cesses of.) 

Carbonized Cloth Discs for High Resist- 
ances. — (See Cloth Discs Carbonized, for 
High Resistances,) 

Carbonizer. — Any apparatus suitable for 
reducing carbonizable material to carbon. 

Carbonizing'. — Subjecting a carbonizable 
substance to the process of carbonization. 
(See Carbonization, Processes of.) 

Carbons, Artificial — Carbons ob- 
tained by the carbonization of a mixture of 
pulverized carbon with different carbonizable 
liquids. 

Powdered coke, or gas-retort carbon, some- 
times mixed with lamp-black or charcoal, is made 
into a stiff dough with molasses, tar, or any other 
hydro-carbon liquid. The mixture is molded 
into rods, pencils, plates, bars or other desired 
shapes by the pressure of a powerful hydraulic 
press. After drying, the carbons are placed in 
crucibles and covered with lamp-black or pow- 
dered plumbago, and raised to an intense heat at 
which they are main f ained for several hours. By 
the carbonization of the hydro-carbon liquids, the 
carbon paste becomes strongly coherent, and by 
the action of the heat its conducting power in- 
creases. 

To give increased density after baking, the 
carbons are sometimes soaked in a hydro-carbon 
liquid, and subjected to a re-baking. This may 
be repeated a number of times. 

Carbons, Concentric-Cylindrical 

A cylindrical rod of carbon placed inside a hol- 
low cylinder of carbon but separated from it 
by an air space, or by some other insulating, 
refractory material. 

Jablochkoff candles sometimes are made with a 
solid cylindrical electrode, concentrically placed 
in a hollow cylindrical carbon. 

Carbons, Cored A cylindrical carbon 

electrode for an arc lamp that is molded 
around a central core of charcoal, or other 
softer carbon. 



Much of the unsteadiness of the arc light is due 
to changes in the position of the arc. Cored car- 
bons, it is claimed, render the arc light steadier, 
by maintaining the arc always at the softer carbon 
and hence at the central point of the electrode. 

A core of harder carbon, or other refractory 
material, is sometimes provided for the negative 
carbon. 

Carbons, Flashed Carbons which 

have been subjected to the flashing pro- 
cess, (See Carbons, Flashing Process for.) 

Carbons, Flashing Process for A 

process for improving the electrical uniformity 
of the carbon conductors employed in in- 
candescent lighting, by the deposition of car- 
bon in their pores, and over their surfaces at 
those places where the electric resistance is 
relatively great. 

The carbon conductor or filament is placed in 
a vessel filled with the vapor of a hydrocarbon 
liquid called rhigolene, or any other readily de- 
composable hydrocarbon liquid, and gradually 
raised to electric incandescence by the passage 
through it of an electric current. A decomposi- 
tion of the hydrocarbon vapor occurs, the car- 
bon resulting therefrom being deposited in and on 
the conductor. 

As the current is gradually increased, the 
parts of the conductor first rendered incandes- 
cent are the places where the electric resist- 
ance is the highest, these parts, therefore, and 
practically these parts only, receive the deposit 
of carbon. As the current increases, other 
portions become successively incandescent and 
receive a deposit of carbon, until at last the 
filament glows with a uniform brilliancy, in- 
dicative of its electric homogeneity. 

A carbon whose resistance varies considerably 
at different parts could not be successfully em- 
ployed in an incandescent lamp, since if heated 
by a current sufficiently great to render the points 
of comparatively small resistance satisfactorily 
incandescent, the temperature of the points of 
high resistance would be such as to lower the life 
of the lamp, while if only those portions were 
safely heated, the lamp would not be economical. 
The flashing process is therefore of very great 
value in the manufacture of an incandescent 
lamp. 

The name " flashing " was applied to the pro- 
cess by reason of the flashing light emitted by the 



Car.] 



[Cas. 



carbons when they have been sufficiently treated. 
The process requires so little time that the dull red 
which first appears soon flashes to the full lumin- 
-osity required. 

The term "flashing 1 ' is sometimes applied to 
the electrical heating to incandescence, while the 
■carbons are in the lamp chambers, and on the 
pumps. This flashing is for the purpose of 
driving off all the gases occluded by the carbon, 
so that these gases may be carried off by the 
operation of pumping. This process is more 
properly called the process for driving off the 
■occluded gases. 

The carbons are sometimes flashed in the liquid 
itself instead of in its vapor. 

Carbons, Paper Carbons, of textile 

or fibrous origin, obtained from the carboniza- 
tion of paper. 

The carbonization of paper is readily effected 
by submitting the paper to the prolonged action 
of a high temperature while out of contact with 
air. 

For this purpose the paper is packed in retorts 
or crucibles, and covered with lamp-black, or 
powdered plumbago, in order to exclude the air. 

Since paper consists of a plane of material uni- 
formly thin in one direction, formed almost en- 
tirely of fibres of pure cellulose, the greatest 
length of which extends in a direction nearly par- 
allel to that in which the paper is uniformly thin, 
it is clear that sheets of this substance, when car- 
bonized, should yield flexible carbons of unusual 
purity and electrical homogeneity, since such 
carbons are structural in character, and are uni- 
formly affected by the heat of carbonization to an 
extent that would be impossible by the carboniza- 
tion of any material in a mass. 

Carcase of Dynamo-Electric Machine. — 

(See Machine, Dynamo-Electric, Carcase of) 
Carcel. — The French unit of light. The 
light emitted by a lamp burning 42 grammes 
of pure colza oil per hour, with a flame 40 
millimetres in height. 

The bec-carcel. One carcel = 9.5 to 9.6 stand- 
ard candles. 

Carcel Lamp. — (See Lamp, Carcel) 
Carcel Standard Gas Jet.— (See Jet, Gas, 

Carcel Standard) 

Card, Compass A card used in the 

mariner's compass, on which are marked the 



four cardinal points of the compass N, S, E 
and W, and these again divided into thirty- 
two points called Rhumbs. (See Compass, 
Azimuth) 

Cardew Yoltmeter. — (See Voltmeter ; 
Cardew.) 

Carriage, Pen The carriage in an 

electric chronograph which holds the pen and 
moves over the sheet of paper on which the 
record is made. (See Chronograph, Elec- 
tric.) 

Carriers of Replenisher.— (See Replen- 
isher, Carriers of) 
Cascade, Charging Leyden Jars by 

— A method of charging jars or condensers 
by means of the free electricity liberated by 
induction from one coating, when a charge is 
passed into the other coating. 

The jars are placed as shown in Fig. 100, with 
the inside coating of the first jar connected with 
the outside coating of the one next it. There is in 
# q 




Fig. 100. Cascade Charging of Leyden Jars. 

reality no increase in the entire charge obtained 
in charging by cascade, since the sum of the 
charges given to the separate jars is equal to 
the same charge given to a single jar separately 
charged. 

The energy of the discharge in cascade can be 
shown to be less than that of the same charge 
when confined to a single jar. This is of course 
to be expected, since it is energy that is charged 
in the jar and not electricity, and, of course, the 
energy charged in the jar can never exceed the 
energy employed in charging the jar. There is 
a small loss for each jar, and this increases ne- 
cessarily with each jar added. 

Cascade, Connection of Electric Sonrces 

in ■ — A term sometimes used for series- 
connection of electric sources. 

The term series-connection is the preferable 
one. (See Connection, Series.) 

Case-Hardening, Electric Super- 
ficially converting a piece of wire into steel 
by electrically produced heat. 



Cas.] 



78 



[Can. 



In electric case-hardening, the superficial layers 
of a piece of iron are converted into steel by 
electrically heating the same, while surrounded 
by a layer of case-hardening flux and carbonaceous 
substances such as animal charcoal, shavings of 
horn, leather cuttings or other similar substances. 

In the case of a readily oxidizable metal like 
iron, oxidation is prevented by surrounding the 
metal by a hydrocarbon gas, which, when suffi- 
ciently heated, deposits on the surfaces a pro- 
tective coating of carbon. This layer of carbon 
gradually carbonizes the iron. 

Case Wiring. — (See Wiring, Case.) 

Cataphoresis.— A term sometimes em- 
ployed in place of electric osmose. (See Os- 
mose, Electric.) 

The word cataphoresis applies to the cases where 
medicinal substances, such as iodine, cocoaine, 
quinine, etc., are caused to pass through organic 
tissues in the direction of flow of an electric cur- 
rent, or from the anode to the kathode. This 
action is probably due to an electrolytic action. 

Cataphoric Action.— (See Action, Cat a- 
fihoric.) 

Catch, Safety A wire, plate, strip, 

or box of readily fusible metal, capable of con- 
ducting, without fusing, the current ordinarily 
employed on the circuit, but which fuses and 
thus breaks the circuit on the passage of an 
abnormally large current. 

Safety-catches are generally placed on multiple- 
arc and multiple -series circuits. (See Fuse> 
Safety.) 

Catelectrotonus.— An orthography some- 
times applied to Kathelectrotonus. (See 
Katkelectrotonus.) 

Cathetometer.— An instrument for the ac- 
curate measurement of vertical height. 

The cathetometer consists essentially of an 
accurately divided vertical rod which carries a 
sliding support for a telescope. The telescope is 
provided with two spider lines at right angles to 
one another, so placed as to be seen in front of 
the object whose height is to be measured. From 
observations taken in different positions, the 
measurement of the true vertical height is readily 
obtained. 

Cathion. — A term sometimes used instead 
Oi Kathion. 



More correctl) written Kathion. (See 
Katkion.) 

Cathode. — A term sometimes used instead 
of Kathode. 

Catoptrics. — That branch of optics which 
treats of the reflection of light. 

Causty, Galvano A term some- 
times used for galvano-cautery. (See Cautery \ 
Galvano?) 

Cauterization. — The act of cauterizing, or 
burning with a heated solid or caustic sub- 
stance. 

Cauterization, Electric Subject- 
ing to cauterization by means of a wire elec- 
trically heated. (See Cautery, Electric) 

Cauterize. — To subject to cauterization, or 
burning with a heated solid or caustic sub- 
stance. 

Cauterizer, Electric A term some- 
times applied to an electric cautery. (See 
Cautery, Electric) 

Cautery, Actual A burning or sear- 
ing with a white-hot metal. 

Cautery Battery. — (See Battery, Cautery.) 

Cautery, Electric An instrument 

used for electric cauterization. 

In electro-therapeutics, the application of 
variously shaped platinum wires heated to in- 
candescence by the electric current in place 
of a knife, for removing diseased growths, or 
for stopping hemorrhages. 

The operation, though painful during applica- 
tion, is afterward less painful than that with a 
knife, since secondary hemorrhage seldom occurs, 
and the wound rapidly heals. 

Electric cautery is applicable in cases where 
the knife would be inadmissible owing to the 
situation of the parts or their surroundings. 

Cautery, Galvano — A term fre- 
quently employed in place of electric cautery. 
(See Cautery, Electric.) 

Cautery, Galvano Electric — An 

electric cautery. (See Cautery, Electric) 

Cautery, Galvano Thermal — - — A 
term sometimes used for an electric cautery. 
(See Cautery, Electric^ 



Cau. 



[Cel. 



Cautery-Knife Electrode.— (See Electrode 
Ca utery- Knife.) 

Cautery, Thermal —A cautery 

heated by heat other than that of electric ori- 
gin, as distinguished from an electric cautery. 
(See Catrtery, Electric?) 

Ceiling Rose.— (See Rose, Ceiling) 

Cell, Depositing — An electrolytic 

cell in which an electro-metallurgical deposit is 
made, (See Metallurgy, Electro) 

Cell, Electrolytic A cell or vessel 

containing an electrolyte, in which electrolysis 
is carried on. 

An electrolytic cell is called a voltameter when 
the value of the current passing is deduced from 
the weight of the metal deposited. 

Cell, Impulsion — A photo-electric 

cell whose sensitiveness to light may be re- 
stored or destroyed by slight impulses given 
to the plates, such as by blows or taps, or elec- 
tro-magnetic impulses. 

An impulsion cell may be prepared by pasting 
pieces of tin-foil, the opposite faces of which are 
respectively polished and dull, on the opposite 
faces of a plate of glass, so as to expose dissimi- 
lar sides to the light, when the cells are dipped 
in alcohol. 

Cell, Photo-Electric A cell capa- 
ble of producing differences of potential 
when its opposite faces are unequally exposed 
to radiant energy. 

Photo-voltaic cells are made in a variety of 
forms, both with selenium and with different me- 
tallic substances. (See Cell, Sele?iitcm. ) 

Cell, Porous A jar of unglazed 

earthenware, employed in double-fluid voltaic 
cells, to keep the two liquids separated. 

The use of a porous cell necessarily increases 
the internal resistance of the cell, from the de- 
crease it produces in the area of cross section of 
liquid between the two elements. When the bat- 
tery is dismantled, the porous cells should be 
kept under water, otherwise the crystallization of 
the zinc sulphate or other salt is apt to produce 
serious exfoliation, or scaling off, or even to 
crumble the porous cell. 

A porous cell is sometimes called a diaphragm, 
but only properly so when the cell is reduced to 
a single separating plate. (See Cell, Voltaic.) 



Cell, Secondary A term sometimes 

used instead of storage cell. 

The term secondary cell is used in contradis- 
tinction to primary or voltaic cell. 

Cell. Secondary or Storage, Boiling of 

■ — A term sometimes applied to the 

gassing of a storage cell. (See Cell, Storage, 
Gassing of) 

Cell, Secondary or Storage, Capacity of 

The product of the current in am- 
peres, by the number of hours the battery is 
capable of furnishing said current, when 
fully charged, until exhausted. 

The capacity of storage cells is given in ampere- 
hours. A storage battery with a capacity of 1,000 
ampere-hours can furnish, say a current of fifty 
amperes for twenty hours, or a current of one 
hundred amperes for ten hours; or a current of 
twenty-five amperes for forty hours. 

Cell, Secondary or Storage, Gassing of 

— : An escape of gas due to the decom- 
position of water on passage of too strong a 
charging current. 

Cell, Secondary or Storage, Renovation 

of The revivifying or recharging of a 

run-down, or discharged storage cell. 

Cell, Secondary or Storage, Time-Fall 

of Electromotive Force of (See 

Force. Electromotive of Seco?idary or 
Storage Cell, Time-Fall, of) 

Cell, Secondary or Storage, Time-Rise 

of Electromotive Force of (See 

Force, Electromotive of, Secondary or 
Storage Cell, Ti7)ie-Rise, of.) 

Cell, Selenium A cell consisting 

of a mass of selenium fused in between two 
conducting wires or electrodes of platinized 
silver or other suitable metal. 

A convenient manner of forming a selenium 
cell is to wind two separate spirals of platinized 
silver wire around a cylinder of hard wood, tak- 
ing care to maintain them a constant distance 
apart, so as to avoid contact between them. The 
space between these wires is filled with fused sele- 
nium, which is allowed to cool gradually. 

Exposure to sunlight reduces the resistance of 
a selenium cell to about one-half its resistance in 



Cel.] 



80 



[Cel. 



the dark, but neither the resistance nor the reduc- 
tion ratio long remains constant. 

A selenium cell produces a difference of poten- 
tial, or electromotive force, when one of its elec- 
trode faces is exposed to light, while the other is 
kept in darkness. 

According to Von Uljanin, who experimented 
with selenium melted in between two parallel 
platinized plates, cooled under pressure, and then 
reduced from the amorphous to the sensitive crys- 
talline variety by gradual cooling after two or 
three heatings in a paraffme bath up to 195 de- 
grees, the following peculiarities were observed: 

(1.) Exposure of one of the electrodes to sun- 
light produced an electromotive force which 
causes a current to flow from the dark to the 
illumined electrode. 

(2.) The maximum electromotive force was 
0.12 volt. 

(3.) The electromotive force disappeared instan- 
taneously and completely on the darkening of the 
electrodes. 

(4.) A slight difference in the electromotive 
force was observed when the positive and nega- 
tive electrodes were alternately exposed to the 
light, the maximum electromotive force being 
attained by the exposure of the negative electrode. 
(5.) If both electrodes are similarly illumined 
the resulting current strength is decreased and 
may reach zero. 

(6.) The action of light is instantaneous. 
(7.) Most of the selenium cells experimented 
with exhibited an electromotive force of polariza- 
tion. 

(8.) The electromotive force of polarization is 
diminished by exposure to light. 

(9.) The electrical resistance and sensitive- 
ness to light as regards the production of an 
electromotive force decrease with time. This 
is probably due to a gradual change in the allo- 
tropic state of the selenium. (See State, Allo- 
tropic. ) 

(10.) The electromotive force produced is pro- 
portional to the intensity of the illumination only 
when the obscure rays or heat rays are absent. 

(11.) Of different wave lengths the orange-yel- 
low rays in the diffraction spectrum, and the 
greenish-yellow in the prismatic fpectrum pro- 
duced the greatest effect. 

Among some of the more recent applications 
of selenium cells are the following: 

(1.) A selenium cell is so placed in a circuit 
containing an electro-magnet and switch, that on 



one of its electrodes being exposed to the de- 
creased illumination of coming night it automat- 
ically turns on an electric lamp, and, conversely, 
on the approach of daylight, and the consequent 
illumination of the electrode, turns it off. 

(2.) A device whereby the presence of light, 
as for example that carried by a burglar, auto- 
matically rings an alarm and thus calls the atten- 
tion of the watchman of the building. 

Cell, Standard (See Cell, Voltaic, 

Standard^ 

Cell, Storage Two relatively inert 

plates of metal, or of metallic compounds, 
immersed in an electrolyte incapable of acting 
considerably on them until after an electric 
current has been passed through the liquid 
from one plate to the other and has changed 
their chemical relations. 

A single one of the cells required to form 
a secondary battery. 

Sometimes, the jar containing a single cell 
is called a storage cell. 

This latter use of the word is objectionable. 

A storage cell is also called an accumulator. 

On the passage of an electric current through 
the electrolyte, its decomposition is effected and 
the electro-positive and electro-negative radicals- 
are deposited on the plates, or unite with them, 
so that on the cessation of the charging current, 
there remains a voltaic cell capable of generating 
an electric current. 

A storage cell is charged by the passage through 
the liquid from one plate to the other of an elec- 
tric current, derived from any external source. 
The charging current produces an electrolytic de- 
composition of the inert liquid between the 
plates, depositing the electro-positive radicals, or 
kathions, on the plate connected with the negative- 
terminal of the source, and the electro-negative 
radicals, or anions, on the plate connected with 
the positive terminal. 

On the cessation of the charging current, and 
the connection of the charged plates by a con- 
ductor outside the liquid, a current is produced, 
which flows through the liquid from the plate 
covered with the electro-positive radicals, to that 
covered with the electro-negative radicals, or in 
the opposite direction to that of the charging cur- 
rent. 

The simplest storage cell is Plan te's cell, which, 
as originally constructed, consists of two piates of 



Cel.] 



81 



[Cel. 



lead immersed in dilute sulphuric acid, H 2 S0 4 . 
On the passage of the charging current, the plates 
A and B, Fig. ioi, dipped in H 2 S0 4 , are covered 
respectively with lead peroxide, Pb0 2 , and finely 
divided, spongy lead. The peroxide is formed on 
the positive plate, and the metallic lead on the 
negative plate. The acid and water should have 
a specific gravity of about 1. 170. When the cell 
is fully charged the acid solution loses its clear- 
ness and becomes milky in appearance, and the 




Discharging? 
Figs. 10 1 and 102. Storage Cell, 

specific gravity increases to 1. 195. This increase 
is a good sign of a full charge. 

When the charging current ceases to pass, the 
cell discharges in the opposite direction, viz., 
from B' to A', that is, from the spongy lead plate 
to the peroxide plate through the electrolyte, as 
shown in Fig. 102. 

As a result of this discharging current the per- 
oxide, Pb0 2 , on A', gives up one of its atoms of 
oxygen to the spongy lead on B', thus leaving 
both plates coated with a layer of PbO, lead 
monoxide, or litharge. When this change is 
thoroughly effected, the cell becomes inert, and 
will furnish no further current until again charged 
by the passage of a current from some external 
source. 

In order to increase the capacity of the storage 
cells, and thus prolong the time of their discharge, 
the coating of lead monoxide thus left on each 
of the plates, when neutral, is made as great as 
possible. To effect this, a process called ' 'forming 
the plates" is employed, which consists in first 
charging the plates as already described, and 
then reversing the direction of the charging cur- 
rent, the currents being sent through the cell in 
alternately opposite directions, until a consider- 
able depth of the lead plates has been acted on. 

It will be noticed that during the action of the 
charging current, the oxygen is transferred from 
the PbO, on one plate, to the PbO, on the other 
plate, thus leaving one Pb, and the other Pb0 2 ; 
and that on discharging, one atom of oxygen is 



transferred from the Pb0 2 , to the Pb, thus leav- 
ing both plates covered with PbO. In reality 
this is but the final result of the action, hydrated 
sulphate of lead, PbO, H 2 S0 4 , being formed, 
and subsequently decomposed. Other com- 
pounds are formed that are but imperfectly un- 
derstood. 

In order to decrease the time required for form- 
ing, accumulators, or secondary cells, have been 
constructed, in which metallic plates covered with 
red lead Pb 3 4 replace the lead p'ates in the 
original Plante cell. On charging, the Pb 3 4 
is peroxidized at the anode, i. e., converted into 
Pb0 2 , and deoxidized, and subsequently con- 
verted into metallic lead at the kathode. Or, in 
place of the above Pb 3 4 , red lead is placed on 
the anode and PbO, or litharge, on the kathode. 

Plates of compressed litharge have also been 
recently used for this purpose. Storage cells so 
formed have a greater storage capacity per unit 
weight than those in which a grid is employed, 
but a higher resistance. 

In all cases where a metal plate is employed 
various irregularities of surface are given to the 
plates, in order to increase their extent of surface 
and to afford a means for preventing the separa- 
tion of the coatings. The metallic form thus 
provided is known technically as a grid. 

Unless care is exercised, the plates will buckle 
from the difference in the expansion of the lead 
and its filling of oxide. This buckling is attended 
with an increase in the resistance of the cell and 
the gradual separation of the oxides that cover or 
fill it. 

Cell, TJiermo-Electric ■ — A name 

applied to a thermo-electric couple. (See 
Couple, Ther mo-Electric?) 

Cell, Yoltaic The combination of 

two metals, or of a metal and a metalloid, 
which, when dipped into a liquid or liquids 
called electrolytes, and connected outside the 
liquid or liquids by a conductor, will produce 
a current of electricity. 

Different liquids or gases may take the place of 
the two metals, or of the metal and metalloid. 
(See Battery, Gas.) 

Plates of zinc and copper dipped into a solu- 
tion of sulphuric acid and water, and connected 
outside the liquid by a conductor, form a simple 
voltaic cell. 

If the zinc be of ordinary commercial purity, 



CeL] 



82 



[Cel. 



and is not connected outside the liquid by a con- 
ductor, the following phenomena occur: 

(i.) The sulphuric acid or hydrogen sul- 
phate, H 2 S0 4 , is decomposed, zinc sulphate, 
ZnS0 4 , being formed, and hydrogen, H 2 , liber- 
ated. 

(2.) The hydrogen is liberated mainly at the 
surface of the zinc plate. 

(3.) The entire mass of the liquid becomes 
heated. 

II, however, the plates are connected outside 
the liquid by a conductor of electricity, then the 
phenomena change and are as follows, viz.: 

(1.) The sulphuric acid is decomposed as be- 
fore ; but, 

(2.) The hydrogen is liberated at the surface of 
the copper plate only. 

(3.) The heat no longer appears in the liquid 
only, but in all parts of the circuit. 

(4.) An electric current now flows through the 
entire circuit, and zvill continue so to floiv as long 
as there is any sulphuric acid to be decomposed, 
and zinc with which to form zinc sulphate. 

' The energy which previously appeared as heat 
only, novo appears in part as electric energy. 

Therefore, although the mere contact of the 
two metals with the liquid will produce a differ- 
ence of potential, it is the chemical potential 
energy which became kinetic during chemical 
combination that supplies the energy required to 
maintain the electric current. (See Energy, 
Kinetic. Energy, Potential.) 

A voltaic cell consists of two plates of different 
metals, or of a metal and a metalloid (or of two 
gases, or two liquids, or of a liquid and a gas), 
each of which is called a 
voltaic ele?jient, and which, |\~ 
taken together, form what is 



called a voltaic couple. 

The voltaic couple dips in- 
to a liquid called an electro- 
lyte, which, as it transmits 
the electric current, is de- 
composed by it. The ele- 
ments are connected outside 
the electrolyte by any con- 
ducting material. 

Direction of the Current.- 



^ 




Fig. 103. Voltaic 
Couple. 



In any voltaic cell 
the current is assumed to flow through the liquid, 
from the metal most acted on to the metal least 
acted on, and outside the liquid, through the out- 
side circuit, from the metal least acted on to the 
metal most acted on. 



In Fig. 103 a zinc-copper voltaic couple is 
shown, immersed in dilute sulphuric acid. Here, 
since the zinc is dissolved by the sulphuric acid, 
the zinc is positive, and the copper negative in 
the liquid. The zinc and copper are of opposite 
polarities out of the liquid. 

There is still a considerable difference of opinion 
as to the exact cause of the potential difference of 
the voltaic cell. There can be no doubt that a 
true contact force exists, but the chemical poten- 
tial energy of the positive plate is the source 
of energy which maintains the potential differ- 
ence. 

The difference in the polarity of the zinc and 
copper in and out of the liquid is generally de- 
nied by most of the later ■writers on electricity, 
since tests by a sufficiently delicate electrometer 
show that the entire zinc plate is negative and 
the entire copper plate positive. Remembering, 
however, the convention as to the direction of 
the flow of the current, since the current flows 
from the zinc to the copper through the liquid, 
we may still fairly regard the zinc as positive and 
the copper as negative in the liquid. It will be 
remembered, that in. every source the polarity 
within the source is necessarily opposite to the 
polarity outside it. The copper plate is there- 
fore called the negative plate, and the wire con- 
nected to its end out of the liquid, the positive 
electrode. Similarly, the zinc plate is called the 
positive plate, and the wire connected to it the 
negative electrode. 

It will of course be understood that in the 
above sketch the current flows only on the com- 
pletion of the circuit outside the cell; that is, 
when the conductors attached to the zinc and 
copper plates are electrically connected. 

Amalgamation of the Zinc Plate. — When zinc 
is used for the positive element, it will, unless 
chemically pure, be dissolved by the electrolyte 
when the circuit is open, or will be irregularly 
dissolved when the circuit is closed, producing 
currents in little closed circuits from minute vol- 
taic couples formed by the zinc and such impuri- 
ties as carbon, lead, or iron, etc., always found 
in commercial zinc. (See Action, Local, of Vol- 
taic Cell.) As it is practically impossible to ob- 
tain chemically pure zinc, it is necessary to amal- 
gamate the zinc plate; that is, to cover it with a 
thin layer of zinc amalgam. 

Polarization of the Negative Plate. — Since the 
evolved hydrogen appears at the surface of the 
negative plate, the surface of this plate, unless 



Cel.] 



83 



[CeL 



means are adopted to avoid it, will, after a while, 
become coated with a film of hydrogen gas, or 
as it is technically called, will become polarized. 
(See Cell, Voltaic, Polarization of.) 

The effect of this polarization is to cause a fall- 
ing off or weakening of the current produced by 
the battery, due to the formation of a count er- 
dectromotive force produced by the hydrogen- 
covered plate; that is to say, the negative plate, 
now being covered with hydrogen, a very highly 
electro-positive element, tends to produce a 
current in a direction opposed to that of the 
cell proper. (See Force, Electromotive, Coun- 
ter.) 

This decrease in current strength is rendered 
still greater by the increased resistance in the cell, 
due to the bubbles of hydrogen, and to the de- 
creased electromotive force, due to the increase 
in the density of the zinc sulphate, in the case of 
zinc in hydrogen sulphate. 

In the case of storage cells, the counter-elec- 
tromotive force of polarization is employed as the 
source of secondary currents. (See Electricity, 
Storage of. Cell, Secondary. Cell, Storage.) 

In order to avoid the effects of polarization in 
voltaic cells, and thus insure constancy of cur- 
rent, the bubbles of gas at the negative plate are 
mechanically carried off either by roughening its 
surface, by forcing the electrolyte against the 
plate as by shaking, or by a stream of air; or else 
the negative plate is surrounded by some liquid 
or solid substance which will remove the hydro- 
gen, by entering into combination with it. (See 
Cell, Voltaic, Polarization of.) 

Voltaic cells are therefore divided into cells 
with one or with two fluids, or electrolytes, or 
into: 

(i.) Single-fluid cells; and 

(2.) Double-fluid cells. 

Very many forms of voltaic cells have been de- 
vised. The following are among the more im- 
portant, viz. : Of the Single-Fluid Cells, the 
Grenet, Poggendorff, or Bichromate, the Zinc- 
Copper, the Zinc Carbon and the Smee. Of the 
Double-Fluid Cells, Grove's, Btmsen's, Callaud 
or Gravity, DanielVs, Leclanche, Siemens-Halske 
and the Meidinger. 

Of all the voltaic cells that have been devised 
two only, viz., the Gravity, a modified Daniell, 
and the Leclanche, have continued until now in 
very general use, the gravity cell being used on 
closed-circuited lines, and the Leclanche on open- 
circuited lines ; the former being the best suited 



of all cells to furnish the continuous constant cur- 
rents employed in most systems of telegraphy, 
and the latter for furnishing the intermittent cur- 
rents required for ringing bells, operating annun- 
ciators, or for similar work. 

Cell, Voltaic, Absorption and Genera- 
tion of Heat in (See Heat, Absorption 

and Ge?ieration of, in Voltaic Cell.) 

Cell, Voltaic, Bichromate A zinc- 
carbon couple used with an electrolyte 
known as electropoion, a solution of bichro- 
mate of potash and sulphuric acid in water. 
(See Liquid, Electropoion) 

Bichromate of sodium or chromic acid are 
sometimes used instead of the bichromate of 
potassium. 

The zinc, Fig. 104, is amalgamated and placed 
between two carbon plates. 
The terminals connected 
with the zinc and carbon 
are respectively negative 
and positive. In the form 
shown in the figure, the zinc 
plate can be lifted out of 
the liquid when the cell is 
not in action. 

The bichromate cell is 
excellent for purposes re- 
quiring strong currents 
where long action is not 
necessary. As this cell 
readily polarizes it cannot 
be advantageously employ- 
ed continuously for any 
considerable period of time. It becomes depolar- 
ized, however, when left for some time on open 
circuit. 

The following chemical reaction probably takes 
place when the cell is furnishing current, viz. : 
K 3 Cr,0 7 + 7 H 2 S0 4 + 3 Zn:= 

K 2 S0 4 -f 3 ZnS0 4 + Cr 2 3(So 4 ) + 7 H 2 0. 

This cell gives an electromotive force of about 
1.9 volts. 

. Cell, Voltaic, Bunsen's A zinc- 
carbon couple, the elements of which are 
immersed respectively in electrolytes of dilute 
sulphuric and strong nitric acids. 

Bunsen's cell is the same as Grove's, except 
that the platinum is replaced by carbon. The 
zinc surrounds the porous cell containing the car- 




Fig. 104. Bichromate 
Cell. 



Cel.] 



84 



[Cel. 



bon. The polarity is as indicated in Fig. 105. 
(See Cell, Voltaic, Grove.) 




Fij. 105. Bunsen Cell. 

The Bunsen cell gives an electromotive force 
of about 1.96 volts. 

Cell, Yoltaic, Callaud's A name 

sometimes given to the gravity cell. (See 
Cell, Voltaic, Gravity) 

Cell, Yoltaic, Capacity of Polarization of 

The quantity of electricity required 

to be discharged by a voltaic cell in order to 
produce a given polarization. (See Cell, Vol- 
taic, Polarization of.) 

During the discharge of a voltaic cell an electro- 
motive force is gradually set up that is opposed 
to that of the cell. The quantity of electricity 
required to produce a given polarization de- 
pends, of course, on the condition and size of 
the plates. Such a quantity is called the capacity 
of polarization. 

Cell, Yoltaic, Closed-Circuit A 

voltaic cell that can be left for a considerable 
time on a closed circuit of comparatively 
small resistance without serious polarization. 

The term closed-circuit voltaic cell is used in 
contradistinction to open-circuit cell, and applies 
to a cell that can only be kept on closed circuit 
for a comparatively short time. 

DanielPs cell and the gravity cell are closed-cir- 
cuit cells. Leclanche's is an open-circuit cell. 

Cell, Yoltaic, Contact Theory of 

A theory which accounts for the production 
of difference of potential cr electromotive 
force in the voltaic cell by the contact of the 
elements of the voltaic couple with one an- 
other by means of the electrolyte. 



The mere contact of two dissimilar substances 
through the electrolyte will produce a difference 
of potential, but the cause of the current which a 
voltaic cell is able to maintain is the chemical 
potential energy which becomes kinetic during 
combination. (See Cell, Voltaic. Series, Contact.) 

Most authorities explain the difference of 
potential produced by the contact of different 
metals by the fact that the metals are sur- 
rounded by air. They point out the fact that the 
order of the metals in the contact-series is 
almost identical with the order of their electro- 
chemical power as deduced from their chemical 
equivalents, and their heat of combination with 
oxygen. It would appear, therefore, that the 
difference of potential between a metal and the 
air which surrounds it, is a measure of the tend- 
ency of the metal to become oxidized. 

The origin of the electromotive force of a zinc- 
copper couple, in an electrolyte of hydrogen sul- 
phate, is the superior affinity of the zinc for the 
oxygen, over that of the copper for the oxygen. 

Cell, Yoltaic, Creeping in The 

formation, by efflorescence, of salts on the sides 
of the porous cup of a voltaic cell, or on the 
walls of the vessel containing the electrolyte. 
Paraffining the portions of the walls out of the 
liquid, or covering the surface of the liquid with 
a neutral oil, obviates much of this difficulty. (See 
Efflorescence.) 

Cell, Yoltaic, Daniell's A zinc- 
copper couple, the elements of which are im- 
mersed respectively in electrolytes of dilute 
sulphuric acid, and a saturated solution of 
copper sulphate. 

In the form of Daniell's cell, shown in Fig. 106, 
the copper element is made in the form of a cylin- 
der c, and is placed in a porous cell. The cop- 
per cylinder is provided with a wire basket near 
the top, filled with crystals of blue vitriol, or cop- 
per sulphate, so as to maintain the strength of the 
solution while the cell is in use. The zinc is in 
the shape of a cylinder and is placed so as to sur- 
round the porous cell. This cell gives a nearly 
constant electromotive force. 

The constancy of action of Daniell's cell 
depends on the fact that for every molecule of 
sulphuric acid decomposed in the outer cell, an 
additional molecule of sulphuric acid is supplied 
by the decomposition of a molecule of copper sul- 
phate in the inner cell. This will be better un* 



Cel.] 



85 



[Cel. 



derstood from the following reactions which take 

place, viz.: 

Zn+H 2 S0 4 = ZnS0 4 -f H 5 
H 3 + CuS0 4 = H 2 S0 4 -f Cu. 
The H 3 S0 4 , thus formed in the inner cell, 

passes through the porous cell, and the copper is 

deposited on the surface of the copper plate. 



^m^^ 



made in a 




Fig 1 06. Daniell s Cell. 

The Daniell cell gives an electromotive force 
of about 1.072 volts. 

A serious objection to this form of cell arises 
from the fact that the copper is gradually de- 
posited over the surface and in the pores of the 
porous cell, thus greatly increasing its resistance. 
This difficulty is avoided in the gravity cell. (See 
Cell, Voltaic, Gravity.) 

Cell, Toltaic, Double-Fluid A 

voltaic cell in which two separate fluids or elec- 
trolytes are employed. 

One of the elements of the voltaic couple is 
dipped into one oi the fluids and the other ele- 
ment into the other fluid. In order to keep the 
fluids separate and distinct, they are either sep- 
arated by means of porous cells, or by the action 
of gravity. (See Cell, Porous. Cell, Voltaic, 
Gravity,) 

In the double-fluid cell the negative element is 
surrounded by a liquid which is capable of pre- 
venting polarization by combining chemically 
with the substance that tends to collect on its 
surface. In the Daniell cell this substance is the 
same as that of the negative plate. (See Cell, 
Voltaic, Polarization of.) 

Cell, Toltaic, Dry A voltaic cell 

in which a moist materia! is used in place of 
the ordinary fluid electrolyte. 



The term dry cell is in reality a misnomer, 
since all such cells are moistened with liquid 
electrolytes. 

The dry cell, like other cells, 
variety of forms. The ab- 
sence of free liquid permits 
the cell to be closed. A well 
known form of dry cell is 
shown in Fig. 107. 

Cell, Voltaic, Effects of 

Capillarity in (See 

Capillarity, Effects of, in 
Voltaic Cell.) 

Cell, Toltaic, Exciting 
Liquid of The elec- 
trolyte Of a Voltaic Cell. Fig, 107. Dry Cell. 

A voltaic cell may have a single electrolyte, in 
which case it is called a single-fluid cell, or it may 
hav-i two electrolytes, in which case it is called a 
double-fluid cell. 

Cell, Toltaic, Fuller's Mercury Bichro- 
mate — A zinc-carbon couple im- 
mersed in an electrolyte of electropoion liquid. 

The zinc is attached to a copper rod by being 
cast thereto, and is placed at the bottom of a 
porous cell, where it is covered by a layer of 
mercury. The carbon plate is placed in electro- 





Fig. 108 Fuller's Mercury Bichromate Cell. 
poion liquid, diluted with water in the proportion 
of three ot the former to two of the latter. The 
zinc is generally placed in pure water, which 
rapidly becomes acid. 

The mercury effects the continuous amalgama- 
tion of the zinc 

A Fuller mercury bichromate cell is shown 
in Fig. io3. 



Cel.] 



86 



[Cel, 



Cell, Voltaic, Gravity A zinc- 
copper couple, the elements of which are em- 
ployed with electrolytes of dilute sulphuric acid 
or dilute zinc sulphate, and a concentrated 
solution of copper sulphate respectively. 

The use of a porous cell is open to the objection 
of increased internal resistance. Moreover, the 
porous cell is apt to receive a coating of copper 
which often deposits on the cell instead of on the 
copper plate. The gravity cell was devised in 
order to avoid the use of a porous cell. As its 
name indicates, the two fluids are separated from 
each other by gravity. 

The copper plate is the lower plate, and is sur- 
rounded by crystals of copper sulphate. The 
zinc, generally in the form of an open wheel, or 
crow-foot, is sus- 
pended near the top 
of the liquid, as 
shown in Fig. 109. 

When the cell is 
set up with sul- 
phuric acid, the re- 
actions are the same 
as in the Daniell 
cell. When copper 
sulphate and zinc 
sulphate alone are 
used, zinc replaces 
the copper in the 
copper sulphate. 
The action is then 
merely a substitution process. 
DanielPs.) 

A dilute solution of zinc sulphate is generally 
used to replace the dilute sulphuric acid. It 
gives a somewhat lower electromotive force, but 
ensures a greater constancy for the cell. 

Cell, Yoltaic, Grenet A name 

sometimes given to the bichromate cell. (See 
Cell.. Voltaic, Bichromate) 

Cell, Voltaic, Grove —A zinc-plati- 
num couple, the elements of which are used 
with electrolytes of sulphuric and nitric acids 
respectively. 

The zinc, Z, Fig. no, is amalgamated and 
placed in dilute sulphuric acid, and the platinum, 
P, in strong nitric acid (HK0 3 ) in a porous cell 
to separate it from the sulphuric acid. (See C ell. 
Porous.) In the Grove cell the current is moder- 
ately constant, since the polarization of the plati- 




Fig. ioq The Gravity Cell. 

(See Cell, Voltaic, 



num plate is prevented by the nitric acid, which 
oxidizes and thus removes the hydrogen that 
tends to be liberated at its surface. The con- 
stancy of the current 
is not maintained for 
any considerable time, 
since the two liquids 
are rapidly decom- 
posed, or consumed, 
zinc sulphate forming 
in the sulphuric acid, 
and water in the nitric 
acid. 

The chemical reac- 
tions are as follows, 
viz.: 

Zn + H 2 S0 4 = 

ZnS0 4 + H a ; 
6H + 2HN0 3 = 

4H 8 + 2NO; 
2NO -f O s = N 2 4 . 

Nitrate of ammo- 
nium is sometime? formed when the nitric acid 
becomes dilute by decomposition. The reaction 
is as follows : 

2HNO3 + 4 H 2 = 3 H 2 + NH 4 N0 8 . 

The cell gives an electromotive force of 1.93 
volts. 

When the porous cell is good, the resistance of 
the Grove cell may be calculated according to 
the following formula of Ayrton: 

3-6 X d 




Grove's Cell. 



R = 



ohms, 



where d, is the distance in inches between the 
platinum and zinc plates, and A, the square inches 
of the immersed portion of the platinum plate. 

Cell, Yoltaic, Leclanche" A zinc- 
carbon couple, the elements of which are used 
in a solution of sal-ammoniac and a finely 
divided layer of black oxide of manganese 
respectively. 

The zinc is in the form of a slender rod and 
dips into a saturated solution of sal-ammoniac^ 
NH 4 C1. 

The negative element consists of a plate of car- 
bon, C, Fig. in, placed in a porous cell, in which 
is a mixture of black oxide of manganese and 
broken gas-retort carbon, tightly packed around 
the. carbon plate. By this means a greatly ex- 
tended surface of carbon surrounded by black 



CeL] 

oxide of manganese, Mn0 8 , is secured. The entire 
outer jar, and the spaces inside the porous cell are 
filled with the solution of sal-ammoniac. 



87 




Fig. in. The Leclanche Cell. 

This cell, though containing but a single fluid, 
belongs, in reality, to the class or type of double, 
fluid cells, being one in which the negative ele- 
ment is surrounded by an oxidizing substance, 
the black oxide of manganese, which replaces the 
nitric acid or copper sulphate in the other double- 
fluid cells. 

This reaction is generally given : 

Zn -f 4NH 4 C1 + 2Mn0 2 = ZnCl 2 + 2NH 4 C1 
+ 2NH 3 -f Mn 2 3 + H 2 0. 

This reaction is denied by some, who believe 
the following to take place : 

Zn + 2(NH 4 Cl) = ZnCl 2 + 2NH 3 + H 2 . 
The ZnCl 2 and NH 3 react as follows : 
ZnCl 2 -f 2(NH 3 ) = 2 (NH 2 ) ZnCl 2 + H 8 . 
2H+ 2(Mn 2 2 ) = H 2 -j- Mn 2 3 ; 
or, possibly, 4H -J- 3MnO a = Mn 2 -j-2H 2 0. 

The Leclanche cell gives an electromotive force 
of about 1.47 volts. It rapidly polarizes, and 
cannot, therefore, give a steady current for any 
prolonged time. When left on open circuit, how- 
ever, it quickly depolarizes. 

Cell, Toltaic, Local Action of 

(See Action, Local, of Voltaic Cell.) 

Cell, Toltaic, Meidinger A zinc- 
copper couple, the elements of which are em- 
ployed with dilute sulphuric acid, or solution 
of sulphate of magnesia, and strong nitric 
acid, respectively. 

The Meidinger cell is a modification of the 
Daniell cell. The zinc-copper couple is thus ar- 
ranged : Z Z, Fig. 112, is an amalgamated zinc 
ring placed near the walls of the vessel, A A, 
constricted at b b. The copper element, c, is 
similarly placed with respect to the walls of the 
vessel d d. The glass cylinder h, filled with 




[CeL 

crystals of copper sulphate, has a small hole in 
its bottom, and keeps the vessel, d d, supplied 
with saturated so- 
lution of copper 
sulphate. The cell 
is charged with di- 
lute sulphuric acid, 
or a dilute solution 
of Epsom salts, or 
magnesium sul- 
phate. 

Cell, Voltaic, 
Open -Circuit 

A voltaic 

cell that cannot be 
kept on closed cir- 
cuit, with a com- 
paratively small 

resistance, for any Fig. 112. The Meidinger Cell. 

considerable time without serious polariza- 
tion. 

A Leclanche cell is an open-circuit cell. The 
term open-circuit cell is used in contradistinc- 
tion to closed-circuit cell, such as the Daniell. 
{See Cell, Voltaic, Closed-Circuit.) 

Cell, Toltaic, Poggendorff —A 

name sometimes given to the Grenet cell. (See 
Cell, Voltaic, Grenet)) 

Cell, Toltaic, Polarization of —The 

collection of a gas, generally hydrogen, on the 
surface of the negative element of a voltaic 
cell. 

The collection of a positive substance like hydro- 
gen on the negative element or plate of a voltaic 
cell sets up a counter-electromotive force, which 
tends to produce a current in the opposite direc- 
tion to that produced by the cell. (See Force, 
Electromotive, Counter. ) 

Polarization causes a decrease in the normal 
current of a voltaic cell : 

(1.) On account of the increased resistance of 
the cell from the bubbles of gas which form part 
of its circuit. 

(2.) On account of the counter-electromotive 
force, produced by polarization. 

There are three ways in which the ill effects of 
the polarization of a voltaic cell can be avoided. 
These are : 

(1.) Mechanical.— -The negative plate is fur- 
nished with a roughened surface which enables the 



Cel.] 



88 



[CeL 



bubbles of gas to escape from the points on such sur- 
face ; or, a stream of gas, or air, is blown through 
the liquid against the plate and thus mechanically 
brushes the bubbles off. 

(2.) Chemical. — The surface of the negative 
plate is surrounded by some powerful oxidizing 
substance, such as chromic or nitric acid, which 
is capable of oxidizing the hydrogen, and thus 
thoroughly removing it from the plate. 

The oxidizing substance may form the entire 
electrolyte, as is the case of the bichromate solution 
employed in the zinc-carbon couple. Generally, 
however, it has been found preferable to employ 
a separate liquid, like nitric acid, to completely 
surround the negative plate, and another liquid for 
the positive plate, the two liquids being generally 
kept from mixing by a porous cell, or diaphragm. 
Such cells are called double -fluid cells. (See 
Cell, Voltaic, Double- Fluid.) 

(3.) Electro-Chemical. — This also necessitates a 
double-fluid cell. The negative element is im- 
mersed in a solution of a salt of the same metal as 
that forming the negative plate. Thus, a cop- 
per plate, immersed in a solution of copper sub 
phate, cannot be polarized, since metallic copper 
is deposited on its surface by the action of the 
hydrogen which tends to be liberated there. 

The constancy of action of a Daniell cell depends 
on a deposition of metallic copper on its copper 
plate as well as on the formation of hydrogen 
sulphate, and the solution of additional copper 
sulphate from the crystallized salt placed in the 
cell. (See Cell, Voltaic, Daniell 's.) 

Cell, Toltaic, Primary, Exhaustion of 

The inability of a primary voltaic 

cell to furnish any further current, unless 
fresh electrolyte, or fresh positive element, or 
both, are supplied to it. 

In the case of exhaustion of a primary voltaic 
cell the stock of fresh energy is supplied to the 
cell from the chemical potential energy of the 
positive element, or of the electrolyte or elec- 
trolytes. (See Energy, Chemical Potential.) 

In most voltaic cells a marked decrease in the 
current strength is observed soon after the cir- 
cuit is closed, and, therefore, long before the 
cell is exhausted. This decrease is due — 

(1.) To the increased internal resistance due to 
the bubbles of hydrogen on the negative plate. 

(2.) To the counter-electromotive force of po- 
larization, where zinc is employed with an elec. 
troiyte of sulphuric acid. 



(3.) To the decrease in the electromotive force 
due to an increase in the density of the zinc sul- 
phate. 

Cell, Toltaic, Secondary, Exhaustion of 

The inability of a secondary cell to 

furnish any further current, unless fresh 
electro-positive and electro-negative materials 
are formed in it by the passage of the 
charging current. 

In the case of the exhaustion of a secondary 
voltaic cell, the stock of fresh energy supplied 
to the cell is derived from the electric energy 
of the charging current. (See Energy, Electric.) 

Cell, Toltaic, Siemens-Halske 

A zinc-copper couple, the elements of which 
are employed with dilute sulphuric acid and 
saturated solution of copper sulphate respect- 
ively. 

The Siemens-Halske cell is a modification of 
Darnell's. A ring of zinc, Z Z, Fig, 113, sur- 




Fig. 1 rj. Siemens-Halske Cell. 

rounds the glass cylinder, c c. The porous 
cell is replaced by a diaphragm, f f, of porous 
paper, formed by the action of sulphuric acid on 
a mass of paper pulp. Crystals of copper sul- 
phate are placed in the glass jar, c c, and rest 
on the copper plate, k, formed of a close copper 
spiral. Terminals are attached at b and h. The 
entire cell is charged with dilute sulphuric acid. 
The resistance of the cell is high. 

Cell, Toltaic, Silver Chloride —A 

zinc and silver couple immersed in electro- 
lytes of sal-ammoniac or common salt and 
silver chloride. 



Cel.] 



89 



[Cel. 



The zinc acts as the positive element, and a 
silver wire, around which a cylinder of fused 
silver chloride is cast, as the negative element. 
The zinc, and the silver wire and silver chloride, 
are placed in a small glass test-tube and covered 
with the sal-ammoniac or common salt, and 
the tube closed by a cork of paraffin, to prevent 
the evaporation of the electrolyte. When sal- 
ammoniac is used, the strength of the solution is 
that obtained by dissolving 23 grammes of pure 
sal-ammoniac in 1 litre of water. The silver 
chloride acts as a depolarizer. 

This cell is used as a standard cell, known as 
De la Rue's standard cell, from its inventor, 
Warren De la Rue. Its electromotive force is 
I.068 volts. 



-Any voltaic 



Cell, Yoltaic, Simple — 

cell formed of a single couple immersed in a 
single exciting liquid. 

Cell, Voltaic, Single-Fluid A vol- 
taic cell in which but a single fluid or elec- 
trolyte is used. 

Single-fluid voltaic cells possess the disadvan- 
tage of polarizing during action. This polariza- 
tion is due to the electro-positive element of the 
electrolyte collecting on the surface of the nega- 
tive plate, or within its mass. For example, 
where dilute sulphuric acid is the electrolyte, 
hydrogen gas collects on the negative plate and 
lowers the electro)notive force produced by the 
cell, by a counter -electromotive force thereby 
generated. (See Force, Electromotive. Force, 
Electromotive, Counter.) 

Cell, Yoltaic, Smee A zinc-silver 

couple used with an electrolyte of dilute sul- 
phuric acid, H 2 S0 4 . 

A form of Smee cell is shown in Fig. 1 14. Here 
the plate of silver is placed between two zinc 
plates. 

The silver plate is roughened and covered with 
a coating of metallic platinum, in the condition 
known as platinum black. ( See Platinum Black. ) 
This cell was formerly extensively employed in 
electro-metallurgy but is now replaced by dynamo- 
dectric-machines. (See Metallurgy, Electro. 
Machine, Dynamo-Electric. ) 

A zinc- carbon couple is sometimes used to re- 
place the zinc-silver, couple. A couple of zinc- 
lead is also used, though not very advanta- 
geously. 




The Smee cell was one of the earliest forms 
of voltaic cells. 

In the zinc-silver couple the chemical reaction 
that takes place when the 
cell is furnishing current is 
as follows, viz. : 
Zn + H 2 S0 4 = ZnS0 4 

+ H 2 . 

The Smee cell gives an 
electromotive force of about 
.65 volt. 

Cell, Voltaic, Stand- 
ard A voltaic cell 

the electromotive force of 
which is constant, and Fig. 114. Smee Cell. 
which, therefore, may be used in the measure- 
ment of an unknown electromotive force. 

Absolute constancy of electromotive force is 
impossible to attain, but if the current of the 
standard cell is closed but for a short time the 
electromotive force may be regarded as practically 
invariable. 

Cell, Voltaic, Standard, Clark's 

The form of standard cell shown in Fig. 115. 

Latimer Clark's standard cell assumes a 
variety of forms. The H-form is arranged as 
shown in Fig. 115. The vessel to the left con- 
tains, at A, an amal- 
gam of pure zinc. The 
other vessel contains, 
at M, mercury covered 
with pure mercurous 
sulphate, Hg 2 S0 4 . 
Both vessels are then 
filled, above the level 
of the cross tube, with 
a saturated solution of 
zinc sulphate Z, Z, to 
which a few crystals 
of the same are added. 
Tightly fitting corks 
C, C, prevent loss by Fig 
evaporation. 

The voltage of this cell in legal volts is 1.438 
[1 —0.00077 (t — 15 degrees C.)]— {Ayrton.) 

The value t, is the temperature in degrees of 
the centigrade scale. 

Cell, Voltaic, Standard, Rayleigh's Form 

of Clark's A modified form of Clark's 

cell. 




US- Clark's Stand- 
ard Cell. 



Cel.] 



90 



[CeL 




Lord Rayleigh's form of Clark's standard cell 
is shown in Fig. 116. The electrodes pass respect- 
ively through the bottom and top of the test tube 
of glass. On the lower 
electrode a layer of mer- 
cury, Hg, is placed. On 
this rests a layer of mercu- 
rous sulphate paste made 
sufficiently semi-fluid with 
a solution of zinc sulphate 
to form an approximately 
level surface. The zinc, 
Zn, is attached to the up- 
per electrode and is im- 
mersed in this semi-fluid 
paste. 

The mercurous sulphate 
appears to act to keep the 
mercury free from impuri- 
ties. 

The electromotive force 
of this cell has been care- 
fully determined by Ray- p . gt fl6 Ray i eig v s 
leigh. Its Value in true Form of Clark's 

Volts is : Standard Cell. 

E= 1.435 E 1 — .00077 (t— 15)] when t, is the 
temperature in degrees Centigrade. 

This cell is often called Clark's normal element. 

Cell, Voltaic, Standard, De la Rue's 

— A form of silver-chloride cell. (See Cell, 
Voltaic, Silver-Chloride?) 

Cell, Voltaic, Stand- 
ard, Fleming's 

The form of standard 
cell shown in Fig. 117. 
The U-tube, Fig. 117, 
is connecteJ, as shown, 
by means of taps, with 
two vessels filled with 
chemically pure solutions 
of copper sulphate of sp. 
gr. 1.1 at 15 degrees C, 
and zinc sulphate of sp. 
gr. 1.4 at 15 degrees C. 
respectively. To use the 
cell the zinc rod Zn, con- 
nected with a wire pass- 
ing through a rubber 
stopper, is placed in the 
left-hand branch. The tap A, is opened and 
the entire U-tube is filled with the denser 
zinc sulphate solution. The tap at C, is then 




Fig. 1 17. Fleming's 
Standard Cell. 



opened, and the liquid in the right-hand branch 
above the tap is discharged into the lower vessel, 
but, from this part only. The tap C, is then 
closed, and the tap B, opened, and the lighter 
copper sulphate allowed to fill the right-hand 
branch above the tap C. The copper rod Cu, fitted 
to a rubber stopper and connected with a con- 
ducting wire, is then placed in the copper solution. 
Tubes are provided at L and M, for the recep- 
tion of the zinc and copper rods when not in use. 
The copper rod is prepared for use by freshly 
electro-plating it with copper. The electro- 
motive force of this cell is 1.074 volts. If the line 
of demarkation between the two liquids is not 
sharp, the arms of the vessels are emptied, and 
fresh liquid is run in. 

Cell, Voltaic, Standard, Lodge's 

A form of standard Daniell cell. 

Lodge's standard cell is shown in Fig. 118. 
Through the tube T, in a 
wide mouthed bottle, is 
passed the glass tube, in the 
mouth of which is placed a 
zinc rod. To the bottom of 
the tube T, a small test-tube 
t, containing crystals of cop- 
per sulphate, is fastened by 
means of a string or rubber 
band. The uncovered end 
of a gutta-percha insulated 
copper wire projects at the 
bottom of t, through a tube 
in a tightly fitting cork, and 
forms the copper electrode. The bottle is partly 
filled as shown with a solution of zinc sulphate. 

The internal resistance of this cell is so high 
that it is only employed in the use of zero methods 
with a condenser. 

Cell, Voltaic, Standard, Sir William 

Thomson's — A form of standard 

Daniell cell. 




Fig. 118. Lodge's 
Form of Danith's Cell. 




Fig. 1 iq. Thomson's Form of Dannll's Cell. 

Sir Wm. Thomson's standard cell is shoAvn in 
Fig. 119. A zinc disc is placed at the bottom of the 



CelJ 



91 



[Cha 



cylindrical vessel and a solution of zinc sulphate 
of sp. gr. 1.2 poured over it. By means of the 
funnel F, a half-saturated solution of copper 
sulphate is carefully poured over this and floats 
on it owing to its smaller density. The electro- 
motive force of this cell is 1.072 true volts at 
15 degrees C. 

Cell, Yoltaic, Standardizing a De- 
termining the exact value of the electromotive 
force of a voltaic cell, in order to enable it to 
be used as a standard in determining the 
electromotive force of any other electric 
source, 

Cell, Yoltaic, Two-Fluid A term 

sometimes employed in place of double-fluid 
cell. (See Cell, Voltaic, Double-Fluid?) 

Cell, Yoltaic, Water A voltaic 

cell in which the exciting liquid is merely 
water. 

Any voltaic couple can be used, the positive 
element of which is acted on by water. (See 
Battery, Voltaic.) 

Cell, Yoltaic, Zinc-Carbon ■ — A 

cell in which zinc and carbon form the posi- 
tive and negative elements respectively. 

A name sometimes given to the bichro- 
mate cell. 

Cell, Yoltaic, Zinc-Copper ■ — A 

cell in which zinc and copper form the posi- 
tive and negative elements respectively. 

Cell, Yoltaic, Zinc-Lead A zinc- 
lead couple sometimes used, though not very 
advantageously, to replace the zinc-silver 
couple in a Smee cell. (See Cell, Voltaic, 
Smee.) 

Cells, Coupled A number of sep- 
arate cells connected in any way so as to 
form a single source. 

Cells, Yoltaic, Series-Connected ■ 

A number of separate voltaic cells connected 
in series so as to form a single source. (See 
Circuit, Series?) 

Cement-Lined Conduit. — (See Conduit. 
Ce?nent-Lined.) 

Cements, Insulating ■ —Various 

mixtures of gums, resins and other substances, 
possessing the ability to bind two or more 



substances together and yet to electrically in- 
sulate one from the other. 

Centi. — (As a prefix) — The one-hundredth 
part of. 

Centi-Ampere. — One-hundredth of an am- 
pere. 

Centi-Ampgre Balance. — (See Balance, 
Centi-Ampere?) 

Centigrade Thermometer Scale. — (See 
Scale, Centigrade Thermometer?) 

Centigramme. — The hundredth of a 
gramme 

One centigramme equals 0.1544 grains avoir- 
dupoise. (See Weights and Measures, Metric 
Sy stefft of.) 

Centilitre. — The hundredth of a litre. 
One centilitre equals 0.6102 of a cubic inch. 
(See Weights and Measures, Metric System of.) 

Centimetre. — The hundredth of a metre. 
One centimetre equals 0.3937 inch. (See 
Weights and Measures, Metric System of. ) 

Centimetre-Gramme-Second Units. — (See 
Units, Centimetre- Granime-Second?) 

Central Galvanization. — (See Galvaniza- 
tion, Central?) 

Central Station. — (See Station, Central?) 

Central Station Burglar Alarm. — (See 
Alarm, Burglar, Central Station?) 

Central Station Lighting. — (See Light- 
ing, Electric Central Station?) 

Centre of Gravity.— (See Gravity, Centre 
of) 

Centre of Oscillation. — (See Oscillation^ 
Centre of.) 

Centre of Percussion. — (See Percussion, 
Centre of.) 

Centrifugal Force. — (See Force, Centrifu- 
gal?) 

Centrifugal Governor. — (See Governor, 
Centrifugal?) 

Chain Lightning. — (See Lightning > 
Chain?) 

Chain, Linked Magnetic and Electric 

■ A chain of three links, the separate 

links of which consist of the primary circuit,. 



Cha.] 



92 



[Cha. 



the magnetic circuit, and the secondary cir- 
cuit respectively, of an induction coil. 

The conception of a linked magnetic and elec- 
tric chain, in studying the action of an induction 
coil, was first developed by Kapp. A linked 
magnetic and electric chain is shown in Fig. 120. 




Fig. I20. Linked Magnetic and Electric Chain. 

If, in such a case, the magnetic core or circuit is 
of varying magnetization, when one of the electric 
circuits has a periodic current passed through 
it, the various phenomena of the induction coil 
are produced. (See Coil, Induction.) 

Chain, Molecular A polarized chain 

of molecules that is supposed to exist in an 
electrolyte during its electrolytic decomposi- 
tion, or in a voltaic cell on closing its circuit. 
(See Hypothesis, Grot thus.) 

Chain Pull.— (See Pull, Chain) 

— The armature 



Chamber, Armature — 

bore. (See Bore. Armature) 

Chamber of Lamp. — (See La?np, Cha?n- 
ber of.) 

Change, Chemical Any change in 

matter resulting from atomic combination 
and the consequent formation of new mole- 
cules. 

Some chemical changes are caused by atomic 
combinations and the formation of new molecules. 
They are necessarily attended by ? loss of the spe- 
cific identity of the substances involved in the 
change. Thus carbon, a black solid, combined 
with sulphur, a yellow solid, produces carbon 
disulphide, a colorless, odorous liquid. (See 
Atom.) 

Change, Physical Any change in 

matter resulting from a change in the relative 
position of its molecules, without the forma- 
tion of new molecules. 

Ice, when heated, is turned into water; steel, 
when stroked by a magnet, is rendered perma- 
nently magnetic; a piece of vulcanite or hard 



rubber stroked by a piece of cat skin becomes 
electrified. In all these cases, which are instances 
of physical changes, the substances retain their 
specific identity . This is true in all cases of phys- 
ical changes. (See Molecule.) 

Changing-over Switch. — (See Switch, 
Changing -over) 

Changing- Switch. — (See Switch, Chang- 
ing.) 

Characteristic Curve. — (See Curve, 
Characteristic) 

Characteristic Curve of Parallel Trans- 
former. — (See Curve, Characteristtc t of 
Parallel Transformer) 

Characteristic Curve of Series Trans- 
former. — (See Curve, Characteristic, of 
Series Transformer) 

Characteristics of Sound. — (See Sound, 
Characteristic of) 

Charge, Bound The condition of 

an electric charge on a conductor placed near 
another conductor, but separated from it by 
a medium through which electrostatic induc- 
tion can take place. (See Induction, Elec- 
trostatic) 

When a charged conductor is placed near an- 
other conductor, but separated from it by a di- 
electric or medium through which induction can 
take place, a charge of the opposite name is in- 
duced in the neighboring conductor. This charge 
is so held or bound on the conductor by the mu- 
tual attraction of the opposite charge that it is 
not discharged on connection with the earth 
unless both conductors are simultaneously touched 
by any good conductor. The bound charge was 
formerly called dissimulated or latent electricity . 
(See Electricity ', Dissimulated or Latent.) 

Charge, Density of The quantity 

of electricity per unit of area at any point on 
a charged surface. 

Coulomb used the phrase surface density to 
mean the quantity of electricity per unit of area 
at any point on a surface. 

Charge, Dissipation of The gradual 

but final loss of any charge by leakage, which 
occurs even in a well insulated conductor. 

This loss is more rapid with negatively charged 
conductors, than with those positively charged. 



Cha.f 



93 



[Cha. 



Crookes, of England, has retained a charge on 
conductors for years, without appreciable leakage, 
by placing the conductors in vessels in which a 
high vacuum was maintained. (See Vacuum, 
High.-) 

Charge, Distribution of The vari- 
ations that exist in the density of an electrical 
charge at different portions of the surface of 
all insulated conductors except spheres. 

The density of charge varies at different points 
of the surface of conductors of various shapes. It 
is uniform at all points on the surface of a sphere. 

It is greater at the extremities of the longer 
axis of an egg-shaped body, and greatest at the 
sharper end. 

It is greater at the corners of a cube than at 
the middle of a side. 

It is greatest around the edge of a circular disc. 

It is greatest at the apex oi a cone 

Charge, Electric The quantity of 

electricity that exists on the surface of an in- 
sulated electrified conductor. 

When such a conductor is touched by a good 
conductor connected with the earth, it is dis- 
charged. (See Condenser.') 

Charge, Free The condition of an 

electric charge on a conductor isolated from 
any other conductor. 

It is impossible to obtain a perfectly free charge, 
•since it is impossible to completel) isolate an 
insulated conductor. The charge, however, can 
be comparatively free. 

The charge, on a completely isolated conductor., 
readily leaves it when it is put in contact with a 
.good conductor connected with the ground. (See 
Charge, Bound.) 

Charge, Induced Electrostatic 

The charge produced by bringing a body 
into an electrostatic field. 

In order to obtain a permanent charge, i. e., a 
charge which will be maintained when the body 
is withdrawn from an electrostatic field, it is nec- 
essary to connect the body with the earth so that 
it may lose, or f part with, a charge of the same 
name as the inducing charge. Then, on the with- 
drawal of this charge, it will possess a charge op- 
posite in name to the inducing charge. (See 
Condenser.) 

Charge, Influence A charge pro- 



duced by electrostatic induction. (See /»- 
duction, Electrostatic) 

Charge, Negative According to the 

double-fluid hypothesis, a charge of negative 
electricity. 

According to the single-fluid hypothesis, 
any deficit of an assumed electrical fluid. 

Charge, Positive According to the 

double-fluid hypothesis, a charge of positive 
electricity. 

According to the single-fluid hypothesis, 
any excess of an assumed electrical fluid. 

Charge, Residual The charge pos- 
sessed by a charged Leyden jar for a few 
moments after it has been disruptively dis- 
charged by the connection of its opposite 
coatings. 

The residual charge is probably due to a species 
of dielectric strain, or a strained position of the 
molecules of the glass caused by the charge. 
Such residual charge is not present in air con- 
densers. In other words, a Leyden jar does not 
give up all the electric energy charged in it, on a 
single disruptive discharge. 

Charge, Return -A charge induced 

in neighboring conductors by a discharge of 
lightning. 

Under the influence of induction a lightning 
stroke produces during its discharge an electric 
shock in the human body, or a charge in neigh- 
boring bodies, which is called the back or re- 
turn stroke of lightning. (See Stroke^ Light- 
ning, Back or Return.) 

Charged Body.— (See Body, Charged) 

Charging Accumulators.— Sending an 

electric current into a storage battery for the 
purpose of rendering it an electric source. 

There is, strictly speaking, no accumulation of 
electricity in a storage battery, such, for example, 
as takes place in a condenser, but a mere storage 
of chemical energy, which may afterward become 
electric. (See Cell, Storage.) 

Charging Leyden Jars by Cascade.— (See 

Cascade. Charging Leyden Jars by) 

Chart, Inclination A map or chart 

on which the isoclinic lines are marked. (See 
Map or Chart, I?iclination. Lines. Lsoclinic.) 



Cha.] 



94 



[Chr. 



Chart, Isodynamic 



-A map or chart 



on which the isodynamic lines are marked. 
(See Map or Chart, Isodynamic. Lines* 
Isodynamic) 

Chart, Isogonal ■ An isogonic chart. 

(See Map or Chart, Isogonal.) 

Chart, Isogonic ■ —A map or chart 

on which the isogonic lines are marked. (See 
Map or Chart, Isogonic. Lines, Isogonic) 

Chatterton's Compound. — (See Com- 
pound, C hatter ton s) 

Chemical Change. — (See Change, Chem- 
ical^) 

Chemical Effect. — (See Effect, Chemical?) 

Chemical Equivalent. — (See Equivalent, 
Chemical?) ♦ 

Chemical Galvano-Cautery. — (See Cau- 
tery, Galvano-Chemical) 

Chemical Phosphorescence. — (See Phos- 
phorescence, Chei?iical?) 

Chemical Photometer. — (See Photometer ; 
Chemical.) 

Chemical Potential Energy. — (See En- 
ergy, Chemical Potential?) 

Chemical Recorder, Bain's (See 

Recorder, Chemical, Bains) 

Chemistry, Electro — That branch 

of electric science which treats of chemical 
compositions and decompositions effected by 
the electric current. (See Electrolysis. De- 
composition, Electrolytic?) 

That branch of chemistry which treats of 
combinations and decompositions by means 
of electricity. 

Electro-chemistry treats of the formation of 
new molecules, by the combination of atoms under 
the electric force, as well as the decomposition of 
molecules by electricity. 

The action of a series of sparks passed through 
air, in forming nitric acid, is an instance of the 
former, and electrolytic decompositions in gen- 
eral afford instances of the latter. 

Chimes, Electric Bells rung by 

the attractions and repulsions of electrostatic 
charges. 

The bells B and B, Fig. 121, are conductively 
connected to ihQj>rime ox positive conductor -\-, 




of a fractional machine. The bell C, is insulated 
from this conductor by means of a silk thread, 
but is connected with the ground by the metallic 
chain. Under these 
circumstances the 
clappers, 1, 1, insu- 
lated by silk threads, 
t, t, are attracted to 
B, B, by an induced 
charge and repelled 
to C, where they lose 
their charge only to 
be again attracted to 
B, B. In this way 
the bells will con- 
tinue ringing as long 
as the electric ma- 
chine is in operation. 

Choking Coil.— (See Coil, Choking?) 

Chronograph, Electric ■ • — An elec» 

trie apparatus for automatically measuring 
and registering small intervals of time. 

Chronographs, though of a variety of forms, 
generally register small intervals of time by 
causing a tuning fork or vibrating bar of steel, 
whose rate of motion is accurately known, to 
trace a sinuous line on a smoke-blackened sheet 
of paper, placed on a cylinder driven at a uni- 
form rate of motion by clockwork. If the fork 
is known to produce, say, 256 vibrations per 
second be used, each sinuous line will represent 
-gi^ part of a second. 



Fig. 121. Electric Chimes. 




Fig, 122* Electric Chronograph. 

An electro-magnet is used to make marks on 
the line at the beginning and the end of the 
observation, and thus permit its duration to be 
measured. 

In the form of electric chronograph shown 



Clir.] 95 

in Fig. 122, an electro-magnet, the armature of 
which carries a pen, is supported on a carriage 
moved by clockwork over a sheet of paper 
wrapped on a rotating cylinder. A clock is so 
connected with the circuit of the electro-magnet 
that it makes or breaks the circuit at the end of 
every second second, and so moves, or displaces, 
the armature, as to cause an elevation or depres- 
sion in the otherwise continuous sinuous line, that 
would be drawn on the paper by the double 
motion of its rotation and the movement of the 
pen-carriage. 

When it is desired to know with great precision 
the exact time of occurrence of any event, 
such, for example, as the transit of a star over the 
meridian, the observer, who carries in his hand a 
push button, or other form of electric key, closes 
or opens the circuit at the exact moment and so 
superposes an additional mark on the sinuous 
line. Since the exact time of starting the clock 
is known, and the intervals between the regular 
successive marks are two seconds each, it is easy to 
estimate from its position between any two such 
marks the exact value of the additional mark inter- 
posed. Fig. 122, taken from Young, shows a form 
of chronograph by Warner & Swasey. The de- 
tails of this apparatus will be understood from 
an inspection of the drawing. 

Chronograph Record. — (See Record, 
Chronograph.) 

Chronoscope, Electric An appa- 
ratus for electrically indicating, but not 
necessarily recording, small intervals of time. 

This term is often used for chronograph. 

The interval of time required for a rifle ball 
to pass between two points may be determined 
by causing the ball to pierce two wire screens 
placed a known distance apart. As the screens 
are successively pierced, an electric circuit is 
thus made or broken, and marks are registered 
electrically on any apparatus moving with a 
known velocity. 

Cigar-Lighter, Electric — (See 

Lighter, Cigar, Electric) 

Cipher Code.— (See Code, Cipher) 

Circle, Azimuth — The arc of a 

great circle passing through the point of the 
heavens directly overhead, called the Zenith, 
and the point directly beneath, called the 

Nadir. 



[Cir, 



Circle, Dipping* — A term some- 
times applied to an inclination compass. (See 
Compass, Inclination) 

Circle, Galvanic A term some- 
times used for galvanic circuit. (See Circuit, 
Galvanic) 

Circle of Reference. — The circle, by refer- 
ence to which simple harmonic motion may 
be studied, by comparison with uniform mo- 
tion around such circuit. (See Motion, 
Si?nple Harmonic) 

Circle, Yoltaic A name formerly 

employed for voltaic cell or circuit. (See 
Cell, Voltaic. Circuit, Voltaic) 

Circuit, Air-Magnetic That part 

of the path of a line of magnetic induction 
which takes place wholly through air. 

Circuit, Alternating Current A 

circuit in which an alternating current of 
electricity is flowing. (See Current, Alter- 
nating) 

Circuit, Astatic A circuit consist- 
ing of two closed curves enclosing equal sur- 
faces. 

Such a circuit is A 

not deflected by the 
action of the earth's 
field. The circuit dis- 
posed, as shown in 
Fig. 123, is astatic and 
produces two equal 
and opposite fields at 
S and S'. (See Mag- 



A 



-IS 

+is' 



Astatic Circuit. 



Fig. 123. 
netism, Ampere* s Theory of.) 

Circuit, Balanced-Metallic A me- 
tallic circuit, the two sides of which have 
similar electrical properties. 

Circuit Breaker. — (See Breaker, Circuit) 

Circuit, Broken An open circuit. 

A circuit, the electrical continuity of which 
has been disturbed, and through which the 
current has therefore ceased to pass. 

Circuit, Closed A circuit is closed, 

completed, or made when its conducting 
continuity is such that the current can pass. 

Circuit, Closed Iron-Magnetic 



The name applied to the path of any line 



Cir.] 



96 



[Cir. 



of magnetic force, which takes place entirely 
through iron, steel, or other paramagnetic sub- 
stance. 
Circuit, Closed-Loop Parallel A 

variety of parallel circuit in which the lead 
and the return circuit are arranged in the 
form of concentric circuits, with the recep- 
tive devices placed radially between them. 

Circuit, Closed-Magnetic A mag- 
netic circuit which lies wholly in iron or other 
substance of high magnetic permeability. 

All lines of magnetic force form closed circuits. 
The term closed-magnetic circuit is used in con- 
tradistinction to a divided circuit, or one in which 
an air gap exists in the substance of high mag- 




Fig. 124. Closed- Magnetic Circuit. 

netic permeability forming the remainder of the 
circuit. This introduces so high a resistance that 
such a circuit is sometimes called an open -mag- 
netic circuit. An iron ring, such as shown in 
Fig. 124, forms a closed -magnetic circuit. 

Circuit, Closed-Magnetic, of Atom 

A closed-magnetic circuit, or closed lines 
of magnetic force supposed to lie entirely in 
the atom itself. 

The assumption of closed lines of magnetic 
force in atoms or molecules was made in order to 
explain the original polarity of the same, and to 
account for some of the other phenomena of 
magnetism. 

When the atom is subjected to a magnetizing 
force, such, for example, as the field of an electric 
current, these closed lines of force are assumed 
to open out and produce lines of polarized atoms. 
According to Lodge, for every single line of force 
produced by the current passing through a coil 
of wire surrounding an iron core, some 3,000 
lines of magnetic force are added to it from the 
iron. Therefore an iron core greatly increases 
the magnetic strength of a hollow coil of wire. 



Circuit, Closed-Magnetic, of Molecule 

■ — A closed-magnetic circuit assumed to lie 
wholly within the molecule. 

As it is not known whether the assumed mag- 
netic circuit lies within the atom or the molecule^ 
it is called indifferently the closed- atomic or 
closed-molecular circuit. (See Circuity Closed- 
Magnetic, of Atom.') 

Circuit, Completed —A closed 

circuit. 

A circuit, the conducting continuity of 
which is unbroken. 

A completed circuit is also called a made or 
closed circuit. 

Circuit, Compound A circuit con- 
taining more than a single source, or more 
than a single electro-receptive device, or both, 
connected by conducting wires. 

The term compound circuit is sometimes ap- 
plied to a series circuit. (See Circuit, Series.) 
The term, however, is a bad one, and is not 
generally adopted. 

Circuit, Constant-Current A cir- 
cuit in which the current or number of am- 
peres is maintained constant notwithstanding 
changes occurring in its resistance. 

The series-circuit, as maintained for arc-lamps, 
is a constant-current circuit. (See Regulation, 
Automatic. ) 

Circuit, Constant-Potential — A 

circuit, the potential or number of volts of 
which is maintained approximately constant. 
The multiple-arc or parallel circuit is an ap- 
proximately constant-potential circuit. 

Circuit, Derivative A derived or 

shunt circuit. (See Circuit, Shunt) 
Circuit, Derived 

A term applied to a shunt 
circuit. 

If, in addition to the galva- 
nometer G, the conductor S, 
Fig. 125, be connected with 
the circuit of the battery B, a 
derived circuit will thus be 
established, and a current will 
flow through S, diminishing Fi *' T *f- Derive * 
the current in the galvanom- 
eter. (See Circuit, Shunt.) 




Cir.] 



97 



[Cir. 



Circuit, Divided-Magnetic A 

magnetic circuit which lies partly in iron, or 
other substance of high magnetic perme- 
ability, and partly in air. 
A divided-magnetic circuit is shown in Fig. 126. 




Fig. 126. Divided Magnetic Circuit. 

Where the iron ring is separated by the air gap, 
a high magnetic resistance is introduced, owing 
to the fact that the iron is at these points replaced 
by air, whose magnetic reluctance is great. 

Circuit, Double-Wire A term 

sometimes used for a simple multiple circuit 
with two conductors or wires. (See Circuit, 
Multiple) 

The term double-wire circuit is used in contra- 
distinction to single-wire circuit. (See Circuit, 
Single- Wire. ) 

Circuit, Earth A circuit in which 

the ground or earth forms part of the con- 
ducting path. 

Circuit, Earth, Telegraphic 

That portion of a telegraphic circuit which is 
completed through the earth or ground. 

Circuit, Electric The path in 

which electricity circulates or passes from a 
given point, around or through a conducting 
path, back again to its starting point. 

All simple circuits consist of the following 
parts, viz.: 

(I.) Of an electric source which may be a 
voltaic battery, a thermopile, a dynamo-electric 
machine, or any other means for producing elec- 
tricity. 

(2.) Of leads or conductors for carrying the 
electricity out from the source, through whatever 
apparatus is placed in the line, and back again to 
the source. 

(3.) Various electro-receptive devices, such as 
electro-magnets, electrolytic baths, electric 
motors, electric heaters, etc., through which 



passes the current by which they are actuated or 
operated. 

Circuit, Electrostatic The circuit 

formed by lines of electrostatic force. 

Lines of electrostatic force, like lines of mag- 
netic force, form closed circuits. Hence the 
origin of the phrase electrostatic circuit, (See 
Force, Electrostatic, Lines of.) 

Circuit, External That part of a 

circuit which is external to, or outside the elec- 
tric source. 

The circuit external to the source consists of 
two distinct parts, viz. : 

(1.) The conductors or leads. 

(2.) The electro-receptive or translating de- 
vices. 

It is in the external circuit only that useful 
work is done by the current. 

Circuit, Forked A term sometimes 

used in telegraphy for a number of circuits 
that radiate from a given central point. 

Circuit, Galvanic A term some- 
times employed instead of voltaic circuit. 

The term galvanic in place of voltaic is unwar- 
ranted by the facts of electric science. (See Cir- 
cuit, Voltaic.) 

Galvani thought he had discovered the vital 
fluid or source of animal life. Volta first pointed 
out the true explanation of the phenomena ob- 
served in Galvani 's frog, and devised means 
for producing electricity in this manner. The 
terms voltaic battery, cell, circuit, etc., are there- 
fore preferable. 

Circuit, Ground A circuit in which 

the ground forms part of the path through 
which the current passes. 

As the ground is not always a good conductor, 
the terminals should be connected with the gas or 
water pipes, or with metallic plates, called ground 
plates. Such connection, or any similar ground 
connection, is usually termed the ground or earth. 

Circuit, Ground, Telegraphic 

An earth circuit used in any system of telegra- 
phy. (See Circuit, Earth, Telegraphic) 

Circuit, Grounded A ground cir- 
cuit. 

Circuit, Incomplete An open or 

broken circuit. 



Cir.] 



98 



[Cir. 



A circuit whose conducting continuity is 
incomplete. 

Circuit, Inductive Any circuit in 

which induction takes place. 

Circuit, Internal That part of a 

circuit which is included within the electric 
source. 

The electric current passing through the inter- 
nal circuit does no useful work. 

Circuit, Leg" of One part of a 

twisted or metallic circuit. 

Circuit, Line The wire or other 

conductors in the main line of any telegraphic 
or other electric circuit. 

Circuit, Line, Telegraphic The 

conductor or line connecting different tele- 
graphic stations. 

Circuit, Local-Battery The cir- 
cuit, in a telegraphic system, in which is 
placed a local battery as distinguished from a 
main battery. (See Telegraphy, American 
or Morse System of.) 

Circuit, Loop — A term sometimes 

applied to a circuit in parallel or multiple-arc. 
(See Circuit, Multifile?) 

Circuit Loop Break. — {Set Break, Circuit 
Loofi.) 

Circuit, Made — A completed circuit. 

A circuit, whose conducting continuity is 
unbroken. 

A made circuit is often called a completed or 
closed circuit. (See Circuit, Closed.) 

Circuit, Magnetic The path through 

which the lines of magnetic force pass. 

All lines of magnetic force form closed circuits. 




is often placed around the magnet. The magnet 
is then said to be iron-clad. 

The armature of a magnet lowers the magnetic 
resistance by affording a better path for the lines 
of magnetic force than the air between the 
poles. 

The magnetic circuit always tries to shorten its 
path, or to render itself as compact as possible. 
This is seen in the action of an armature drawn 
towards a magnet pole. 

Circuit, Main-Battery —A term 

sometimes used for line circuit. (See Circuit, 
Line?) 

Circuit, Metallic A circuit in which 

the ground is not employed as any part of the 
path of the current, metallic conductors being 
employed throughout the entire circuit. 

Circuit, Multiple A compound cir- 
cuit, in which a number of separate sources 
or separate electro-receptive devices, or both, 
have all their positive poles connected to a 
single positive lead or conductor, and all their 
negative poles to a single negative lead or 
conductor. 

The connection of three Bunsen cells, in mul- 
tiple, is shown in Fig. 128, where the three car- 




Fig. 127. Magnetic Circuit. 

In the bar magnet, shown in Fig. 127, part of 
this path is through the air. In order to reduce 
or lower the resistance of a magnetic circuit, iron 



Fig. 128. Batteries connected in a Multiple Circuit. 

bons, C, C, C, are connected together so as to form 
the positive, or -f- terminal of the battery, and 
the three zincs, Zn, Zn, Zn, are similarly con- 
nected together so as to form the negative, or — 
terminal. 

The electromotive force is the same as that of 
a single cell, or source. The internal resistance 
of the source is as mach less than the resistance of 
any single source as the area of the combined 
negative or positive plates is greater than that of 
any single negative or positive plate; or, in other 
words, is less in proportion to the number of cells, 
or other separate sources so coupled. 

The connection of six cells in multiple or 
parallel circuit, is shown in Fig. 129. 



€ir.J 



99 



In the case of the six cells, the current would 



be. 



C = 



where E, is the electromotive force, r, the in- 
ternal, and r', the external resistance. 



a Q ^ gjj §JP ) 



Z^. I2q. Six Cells Connected in Multiple. 

In the case of voltaic cells the effect of multiple 
connection on the internal resistance of the source 
is to increase the area of cross-section of the 
liquid in the direct proportion of the number of 
cells added, and consequently to decrease the re- 
sistance in the same proportion. 

When strong or large currents of low electro- 
motive force are required, connections in multi- 
ple-arc are generally employed. 

The multiple-arc connection was formerly 
called comiection-f or -quantity. This term is now 
abandoned. 

The total resistance for the parallel circuit is 
obtained as follows: calling the separate resist- 
ances of the separate electro-receptive devices, 
R', R", R'", etc., etc., etc., total resistance, 

K __ R'XR'X R"' 

R' R" + R" R'" -f- R' R'" 

or, what is the same thing, the conductivity is the 
sum of the reciprocal of the separate resistances, 
**. e. : 

Conductivity = -yrr -f- Tpr _}_ -^ttt* 

The joint resistance of only two separate resist- 
ances joined in a multiple-circuit is equal to the 
product of the separate resistances divided by 
their sum. 

When the separate resistances joined in multiple 
arc are all of the same value, the joint resistance is 
equal to the resistance of one of them divided by 
their number. 



-A term often 



Circuit, Multiple-Arc — 

used for multiple circuit. (See Circuit, Mul- 
tiple^ 

Circuit, Multiple-Series A com- 
pound circuit in which a number of separate 



[Cir. 

sources, or separate electro-receptive devices, 
or both, are connected in a number of sepa- 
rate groups in series, and these separate 
groups subsequently connected in multiple. 
In Fig. 130, a multiple-series circuit of six 
c 

"Y 



J 



Fig. 130. Multiple-Series- Connected Cells. 

sources is shown, in which three separate groups 
of two series-connected cells are coupled in multi- 
ple. The current takes the paths indicated by the 
arrows. The electromotive force of the source 
will be increased in proportion to the number of 
cells in series, and the internal resistance de- 
creased in proportion to the number in parallel. 



J 



Fig. 131. Cells Connected in Multiple- Series. 
2 

In Fig. 131, six cells are arranged in two 
groups of three series-connected cells, and these 
threap groups connected in parallel. 

Calling r, the resistance of each separate cell, 
the total resistance for the multiple-series circuit 
for a circuit containing three cells in parallel and 
two in series is, 

R = -££_ 



for three in series and two in parallel, 

R=_3L_. 
2 

If, therefore, the circuit of this battery be 

closed by a resistance equal to r, the current 

would be in the case of Fig. 130, 

2E 



C=. 



+ ' 



Cir. 



100 



[Cir. 



Circuit, Negative Side of The side 

of a circuit opposite to the positive side. 
(See Circuit, Positive Side of.) 

That side or half of a circuit connected to or 
leading from the positive terminal of the source of 
current. 

Circuit, Open A broken circuit. 

A circuit, the conducting continuity of 
which is broken. 
Circuit, Open-Iron Magnetic — 

The path of a line of magnetic induction, 
which passes partly through iron, and partly 
through an air space. 

The magnetic circuit is always closed, that is 
the lines of magnetic force always form closed 
paths. The term "open" is used in contradis- 
tinction only to "closed " iron magnetic circuit, 
in which the entire path of a line of force passes 
through iron. (See Circuit, Magnetic.) 

Circuit, Parallel A name some- 
times applied to circuits connected in mul- 
tiple. (See Circuit, Multiple?) 

Circuit, Parallel-Tree A form of 

parallel circuit in which the receptive devices 
are placed in parallel between the leads and 
returns, and the branches and sub-branches 
arranged in a tree-like form. 

Circuit, Positive Side of That side 

of a circuit, bent in the form of a circle, in 
which, if an observer stood with his head in 
the positive region, he would see the current 
pass round him from his right hand towards 
his left. — {Danielle 

Circuit, Recoil A term sometimes 

applied to the circuit that lies in the alterna- 
tive path of a discharge. (See Path, Alter- 
native?) 

Circuit, Return That part of a 

circuit by which the electric current returns to 
the source. 

In a multiple-circuit the lead that is con- 
nected to the negative terminals of the 
separate sources. 

Circuit, Series A compound cir- 
cuit in which the separate sources, or the sep- 
arate electro-receptive devices, or both, are so 
placed that the current produced in each, or 
passed through each, passes successively 



through the entire circuit from the first to the 
last. 

The six cells, shown in Fig. 132, are connected 
in series by joining the positive pole of each cell 
with the negative pole of the succeeding cell, the 
negative and positive poles at the extreme ends 




Fig. 132. Series Circuit. 

being connected by conductors with the external 
circuit. 

The connection of three Leclanche cells in 
series is clearly shown in Fig. 133. The carbons, 




Fig. T 33' Voltaic Cells Connected in Series. 
C, C, of the first and second cells are connected to 
the zincs, Zn, Zn, of the second and third cells, 
thus leaving the zinc, Zn, of the first cell, and the 
carbon, C, of the third cell, as the terminals of 
the battery. The direction of the current is 
shown by the arrows. 

The resistance of such a connection is equal to 
the sum of the resistances of all of the separate 
sources. 

The electromotive force is equal to the sum of 
the separate electromotive forces. 

If the electromotive force of a single cell is 
equal to E, its internal resistance to r, and the 
resistance of the leads and electro-receptive de- 
vices to r', then the current in the circuit, 

c * . 

r + r 
If six of such cells are coupled in series, the cur- 
rent becomes 

6E 



C = 



6r + r' 

If, however, the internal resistance of each cell be 
so small as to be neglected, the formula becomes 
6E. 
r' 



C = 



Cir.] 



101 



[Cir. 



or the current is six times as great as with one 
cell. 

The total resistance of the separate sources or 
electro-receptive devices of the series circuit is 
as follows, calling R', R", R'", etc., the separate 
resistance and R, the total resistance, 
R = R'-fR"-f R "', etc. 

The series connection of battery cells is used 
on telegraph lines, where a high electromotive 
force is required in order to overcome a consider- 
able resistance in the circuit, or in similar cases 
where the resistance in the external circuit is 
great, on account of a number of electro-receptive 
devices being connected to the line in series. 

The series connection was formerly called 
connection for intensity. The term is now aban- 
doned. 

Circuit, Series-Multiple A com- 
pound circuit, in which a number of separate 
sources, or separate electro-receptive devices, 
or both, are connected in a number of sepa- 
rate groups in multiple-arc, and these sepa- 
rate groups subsequently connected in series. 

In the series-multiple circuit the resistance of 
each multiple group is equal to the resistance of 
a single branch divided by the number of branches. 

If, for example, r, is the resistance of each sepa- 
rate branch of say seven parallel circuits in each 
of the separate groups of multiple circuits, then 
the resistance, R, of each separate multiple 
group is— 

R = JL. 

7 
The total resistance of the series-multiple cir- 
cuit is equal to the sum of the resistances of the 
separate multiple groups. The total resistance of 
the three groups is— 

R'= - + I + L = *L. 

7 7 7 7 

An example of the series-multiple circuit is 
shown in Fig. 134, which is the method adopted 



Fig. 134. Series-Multiple Circuit. 
in the use of distribution boxes. Here a number 
c; multiple groups or circuits are connected with 
each other in series, as shown. (See Box, Dis~ 
tribution, for Arc Light Circuits.) 

Circuit, Short A shunt, or by-path. 



of comparatively small resistance, around the 
poles of an electric source, or around any 
portion of a circuit, by which so much of the 
current passes through the new path, as vir- 
tually to cut out the part of the circuit around 
which it is placed, and so prevent it from re- 
ceiving an appreciable current. 

Circuit, Shunt A branch or addi- 
tional circuit provided at any part of a cir- 
cuit, through which the current branches or 
divides, part flowing through the original cir- 
cuit, and part through the new branch. 

A shunt circuit is in multiple circuit with the 
circuit it shunts. 

In the case of branch circuits each of the cir- 
cuits acts as a shunt to the others. Any number 
of additional or shunt circuits may be thus pro- 
vided. (See Laws, Kirchhojfs.) 

Circuit, Simple A circuit containing 

a single electric source, and a single electro- 
receptive device, connected by a conductor. 

The term simple circuit is sometimes applied 
to a multiple circuit. The term is not, however, 
a good one, and is not in general use. 

Circuit, Single- Wire A term some- 
times used for a grounded circuit. (See 
Circuity Grounded?) 

The single-wire circuit is sometimes used in the 
distribution of incandescent lamps in multiple-arc. 
One pole of the dynamo is put to ground, and the 
other pole to a single wire or lead. The electro- 
receptive devices have one of their poles con- 
nected to this lead and the other pole to earth. 
The single- wire circuit is a very objectionable 
circuit so far as safety is concerned. 

It is frequently used, however, in the wiring of 
ships. 

Circuit, Through A telephonic or 

telegraphic circuit that has been completed 
through to a given station by cutting out inter- 
ruptions or breaks in the line by the connec- 
tion together of sections of different wires. 

Circuit, Time-Constant of —The 

time in which a current due to a constant 
electromotive force will rise in a conductor 
to a definite fraction of its maximum value. 

The ratio of the inductance of a circuit to 
its resistance. 



Cir.J 



102 



[Cle. 



The time required from the moment of 
closing the circuit, for a current to rise to 



a value equal to 



e — i 



of the full value, or 



.632 of the maximum value. 

In the above, e, equals 2.71828, or the base of 
the Napierian system of logarithms. 

The time-constant is proportional to the con- 
ductivity of the circuit and its formal resistance. 

Approximately the time constant of a circuit is 
the time from closing the circuit, in which the 
current rises to two-thirds of its maximum value, 

this maximum value being determined by the 

■p 
formula, C = _ . 

R 

The time constant of a circuit may be reduced — 

(1.) By decreasing the self-induction of the cir- 
cuit. 

(2.) By increasing the resistance. 

In the case of a magnetic conductor the time- 
constant is proportional to a quantity (the perme- 
ability) which is determined by the capacity of 
the conductor to utilize part of the energy in 
producing magnetization of its substance. — {Flem- 
ing.) 

Circuit, Toltaic The path through 

which the current flows out from a voltaic cell 
or battery, through the translating devices 
and back again to the cell or battery. 

Circuits? Forked —A term employed 

in telegraphy to indicate circuits that radiate 
from any single point. 

Forked circuits are employed in simultaneously 
transmitting messages to several stations. 

Circuits, Varieties of Conducting 

paths provided for the passage of an electric 
current. 

Electric circuits may be divided, according to 
their complexity, into— 

(1.) Simple. 

(2.) Compound. 

According to the peculiarities of their connec- 
tions, into — 

(1.) Shunt or derived. 

(2.) Series. 

(3.) Multiple, multiple-arc or parallel. 

(4.) Multiple-series. 

(5.) Series-multiple. 

Either the circuits, the sources, or the electro- 



receptive devices may be connected in series, in 
multiple, in multiple-series or in series-multiple. 

According to their resistance, circuits are 
divided into — ■ 

(1.) High-resistance. 

(2.) Low-resistance. 

According to their relation to the electric 
source, into— 

(1.) Internal circuits. 

(2.) External circuits. 

According to their position, or the work done, 
circuits are divided into very numerous classes; 
thus, in telegraphy, we have the following, viz.: 

(1.) The line-circuit. 

(2.) The earth or ground circuit. 

(3.) The local-battery circuit. 

(4.) The main-battery circuit, etc. 

Circular Bell.— (See Bell, Circular.) 
Circular Units. — (See Units, Circular) 

Circular Units (Cross-Sections), Table 

of (See Units, Circular {Cross-Sec- 
tions), Table of.) 

Clamp, Carbon A carbon clutch. 

(See Clutch, Carbon, of Arc Lamp) 

Clamp for Arc Lamps. — A clamp for 
gripping the lamp-rod, /. e„ the rod that sup- 
ports the carbon electrodes of arc lamps. 
(See Lamp, Electric, Arc) 

Clamp, Rod A carbon clutch. (See 

Cla??zp for Arc Lamps.) 

Clark's Compound. — (See Compound, 
Clark's) 

Clark's Standard Voltaic Cell.— (See 

Cell, Voltaic, Standard, Clark's) 

Clark's Standard Voltaic Cell, Ray- 

leigh's Form of —(See Cell, Voltaic, 

Standard, Rayleigtis Form of Clark's) 

Clay Electrode.— (See Electrode, Clay) 

Cleansing", Fire The removal of 

grease from metallic articles, that are to be 
electro-plated, by subjecting them to the action 
of heat. 

This cleansing is for the purpose of obtaining a 
uniform, adherent coating. 

Clearance-Space. — (See Si>ace. Clearance) 



Cle.] 



103 



[Clo* 



Clearing-Out Drops.— (See Drops, Clear- 
ing-Out) 

Cleat, Crossing A cleat so arranged 

as to permit the crossing of one pair of wires 
under or over another pair without contact 
with each other. 

Cleat- Wiring.— (See Wiring, Cleat) 

Cleats, Electric Suitably shaped 

pieces of wood, porcelain, hard rubber or 
other non-conducting material used for fasten- 
ing and supporting electric conductors to 
ceilings, walls, etc. 

A simple form of wooden cleat is shown in 
Fig. 135- 




Fig. 135. Wooden Cleat. 



-An instrument 



Clepsydra, Electric 

for measuring time by the escape of water or 
other liquid under electrical control. 

Climbers, Pole 

—Devices employed by 
linemen for climbing 
wooden telegraph poles. 

A climber with straps 
for attachment to the leg 
and foot is shown in Fig. 
136. 

Clip, Cable A 

term sometimes used for 
cable hanger. (See 
Hanger, Cable) 

Clock, Electric 

— A clock, the works of 
which are moved, con- 
trolled, regulated or 
wound, either entirely or partially, by the elec- 
tric current. 




Fig. 136. Climber and 
Straps. 



Electric clocks may be divided into three 
classes, viz.: 

(1.) Those in which the works are moved en- 
tirely or partially by the electric current. 

(2.) Those which are controlled or regulated 
by the electric current. 




Fig. 137. Controlling 
Clock. 



(3.) Those which are merely wound by the 
current. 

A clock moving independently of electric power 
is prevented from gain- 
ing or losing time, by 
means of a slight re- 
tardation or acceleration 
electrically imparted . 
The entire motion of 
the balance wheel is 
sometimes imparted by 
electricity. 

An example of one of 
many forms of controll- 
ing electric clocks is 
shown in Fig. 137, 
where the split battery 
(See Battery, Split), P 
N, is connected, as 
shown, to the spring 
contacts S and S'. In this way currents are sent 
into the circuit in alternately opposite directions. 
The pendulum bob, Fig. 138, of the con- 
trolled clock is formed of a hollow coil of insu- 
lated wire, which encircles one or both of two 
permanent magnets, A and A', placed with their 
opposite poles facing each other. 

When the pendulum of the controlling clock is 
in the position shown in Fig. 137, the current 
passes in the direction E P Sn W, etc., and through 
the coil C, Fig. 138. When the pendulum of the 
controlling clock is in con- 
tact with S', the current 
flows through Wn S' N E, 
etc., and through the coil 
C in the opposite direc- 
tion. In this manner a 
slight motion forwards or 
backwards is imparted to 
the pendulum, which is 
thus kept in time with the 
controlling clock. 

Mercury contacts are 
sometimes employed in 
place of the springs S and 
S'. Induction currents may A 1 
also be employed. 

Clocks of non-electric ac- 
tion may be electrically 
controlled, or correctly set at certain intervals, 
either automatically by a central clock, or by the 
depression of a key operated by hand from an 
astronomical observatory. 




Fig. 138. Controlled 
Clock. 



Clo. 



104 



[Clo. 



In a system of time-telegraphy, the controlling 
clock is called the master clock, and the con- 
trolled clocks, the secondary clocks. 

Secondary clocks are generally mere dials, con- 



Clock, Electrical-Controlling 



-In 




Fig. 1 39* Mechanism of Secondary Clock. 

taining step-by-step movements, for moving the 
hour, minute and second hands, as shown in 
Fig. 139. 

In Spellier's clock, a series of armatures H, 
Fig. 140, mounted on the circumference of a 

JA 




Fig. 140. Spellier's Electric Clock. 

wheel, connected with the escapement wheel, 
pass successively, with a step-by-step movement, 
over the poles of electro-magnets. On the com- 
pletion of the circuit, they are attracted towards 
the magnet, and on the breaking of the circuit 
they are drawn away by the fall of the weight F, 
placed on the lever D, pivoted at E. A pulley at 
E, runs over the surface of a peculiarly shaped 
cog on the escapement wheel. 

Clock, Electric Annunciator A 

clock, the hands or works of which, at cer- 
tain predetermined times, make electric con- 
tacts and thus ring bells, release drops, trace 
records, etc. 



a system of time telegraphy, the master clock, 
whose impulses move or regulate the second- 
ary clocks. (See Clock, Electric.) 

Clock, Electrically-Controlled In 

a system of time telegraphy, a secondary 
clock, that is either driven or controlled by 
the master clock. (See Clock, Electric.) 

Clock, Electrolytic, Tesla's A time 

piece in which the rotation of the wheel work 
is obtained by the difference in weight of the 
two halves of a delicately pivoted and well- 
balanced wheel placed in an electrolytic 
bath. 

In the electrolytic clock of Nikola Tesla, a deli- 
cately formed and balanced disc of copper is sup- 
ported on a horizontal axis at right angles to the 
shortest distance between the two electrodes, and 
placed in a bath of copper sulphate. Its two 
halves become respectively electro -positive and 
electro-negative when a current is passed through 
the bath, and consequently metal is deposited on 
one half and dissolved from the other half. The 
rotation of the disc under the influence of gravity 
is caused to mark time. 

An electrolytic clock could therefore be made 
to answer roughly as an electric meter. 

Clock, Master The central or con- 
trolling clock in a system of electric time-dis- 
tribution, from which the time is transmitted 
to the secondary clocks in the circuit. (See 
Clock, Electric) 

Clock, Secondary Any clock in a 

system of time telegraphy that is controlled 
by the master clock. (See Clock, Electric) 

Clock, Self- Winding" A clock that 

at regular intervals is automatically wound by 
the action of a small electro-magnetic motor 
contained within it. 

This motor is usually run by one or more vol- 
taic cells, concealed in the case of the clock. 

Closed-Circuit. — (See Circuit, Closed) 

Closed-Circuit Battery. — (See Battery, 
Closed- Circuit) 

Closed-Circuit, Single-Current, Signal- 
ing (See Signaling, Single-Current, 

Closed- Circuity 



Clo.] 



105 



[Coe. 



Closed-Circuit Thermostat. — (See Ther- 
mostat t Closed-Circuit?) 

Closed-Circuit Yoltaic Cell.— (See Cell, 
Voltaic, Closed-Circuit?) 

Closed-Circuit Voltmeter.— (See Volt- 
meter, Closed-Circuit?) 

Closed-Circuited. — Placed in a closed or 
completed circuit. 

A voltaic battery, or other source, is closed- cir- 
cuited when its poles or terminals are electrically 
connected with each other. 

Closed-Circuited Conductor.— (See Con- 
ductor, Closed-Circuited?) 

Closed-Circular Current. — (See Current, 
Closed-Circular?) 

Closed-Coil Disc Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Closed-Coil Disc?) 

Closed-Coil Drum Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Closed-Coil Drum?) 

Closed-Coil Dynamo-Electric Machine. — 
(See Machine, Dynamo-Electric, Closed- 
Coil?) 

Closed-Coil King Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Closed-Coil Ring?) 

Closed-Iron-Circuit Transformer.— (See 
Transformer, Closed-Iron-Circuit?) 

Closed-Loop Parallel- Circuit.— (See Cir- 
cuit, Closed-Loop Parallel?) 

Closed-Magnetic Circuit. — (See Circuit, 
Closed-Magnetic?) 

Closed-Magnetic Core. — (See Core, Closed- 
Magnetic?) 

Closure. — The completion of an electric 
circuit. 

Cloth Discs, Carbonized, for High Re- 
sistances Discs of cloth carbonized by 

heating to an exceedingly high temperature 
in a vacuum, or out of contact with air. 

After carbonization the discs retain their flex- 
ibility and elasticity and serve admirably for high 
resistances. When piled together and placed in 
glass tubes, they form excellent variable resist, 
ances when subjected to varying pressure. 



Cluh-Footed Magnet. — (See Magnet, 
Club-Footed?) 
Clutch, Carhon, of Arc Lamp A 

clutch or clamp attached to the rod or other 
support of the carbon of an arc lamp, pro- 
vided for gripping or holding the carbon. 
(See Lamp, Electric Arc.) 

Clutch Rod.— (See Rod, Clutch?) 
Coating, Metallic — : — — A covering or 
coating of metal, usually deposited from 
solutions of metallic salts by the action of an 
electric current . (See Plating, Electro?) 

Coating of Condenser. — A sheet of tin 
foil on one side of a Leyden jar or condenser, 
directly opposite a similar sheet on the other 
side for the purpose of receiving and collecting 
the opposite charges. (See Jar, LeydeTi. 
Condenser?) 

Coatings of Leyden Jar.— The sheets of 
tin foil or other conductor on the opposite 
sides of a Leyden jar or condenser. (See 
Jar, Leyden. Condenser?) 

Code, Cipher — A code in which a 

number of words or phrases are represented 
by single words, or by arbitrary words or syl- 
lables. 

The message thus received requires the posses- 
sion of the key to render it intelligible. 

Code,Telegraphic The pre-arranged 

signals of any system of telegraphy. (See 
Alphabet, Telegraphic. Alphabet, Tele- 
graphic, Morse's. Alphabet, Telegraphic, 
International Code.) 

Co-efficient, Algebraic A number 

prefixed to any quantity to indicate how 
many times that quantity is to be taken. 

The number 3, in the expression 3a, is a co- 
efficient and indicates that the a, is to be taken 
three times, as a -j- a -\- a = 3a. 

Co-efficient, Economic, of a Dynamo- 
Electric Machine — The ratio between 

the electrical energy, or the electrical horse- 
power of the current produced by a dynamo, 
and the mechanical horse-power expended in 
driving the dynamo. 

The economic co-efficient is usually called the 
efficiency. 



Coe.] 



106 



[Coi. 



The efficiency may be the commercial effi- 
ciency, which is the useful or available energy in 
the external circuit divided by the total mechan- 
ical energy; or it may be the electrical efficiency, 
which is the available electrical energy divided 
by the total electrical energy. 

The efficiency of conversion is the total elec- 
trical energy developed, divided by the total 
mechanical energy applied. 

If M, equals the mechanical energy, 

W, the useful or available electrical energy, 

and 
w, the electrical energy absorbed by the 

machine, and 
m, the stray power, or the power lost in 
friction, eddy currents, air friction, etc. 
Then, since 

M = W + w + m, 
The Commercial Efficiency 
= W_ W 

M W + w + m* 
The Electrical Efficiency 
W 



W + w 
The Efficiency of Conversion 

_ W -f w _ W + w 



M 



W + w-f-m 



Co-efficient of Electro-Magnetic Inertia. 

— (See Inertia, Electro-Magnetic, Co-effi- 
cient of.) 

Co-efficient of Expansion. — (See Expan- 
sion, Co-efficient of.) 

Co-efficient of Expansion, Linear ■ 

(See Expansion, Linear, Co-efficient of.) 

Co-efficient of Magnetic Induction. — (See 
Induction, Magnetic, Co-efficient of.) 

Co-efficient of Magnetization. — (See 
Magnetization, Co-efficient of.) 

Co-efficient of Mutual- Inductance. — (See 
Inductance, Mutual, Co-efficient of.) 

Co-efficient of Mutual-Induction. — (See 
Induction, Mutual, Co-efficient of.) 

Co-efficient of Self-induction. — (See In- 
duction, Self, Co-efficient of.) 

Coercitive Force. — (See Force, Coerci- 
tive) 

Coercive Force.— (See Force, Coercive) 

Coil, Choking A coil of wire so 



wound on a core of iron as to possess high 
self-induction. 

Choking-coils are used to obstruct or cut off an 
alternating current with a loss of power less than 
with the use of a mere ohmic resistance. 

Fig. 141 shows a choking -coil. It consists of 
a circular solenoid of insulated wire, wound 
on a core of soft iron wire. A thorough divis- 
ion of the core is obtained by forming it of coils 
of insulated iron wire. In this way, no eddy 
currents are produced in the coil. When a simple 
periodic electromotive force is applied to the 
terminals of such a coil, if 
the magnetic permeability 
of the coil is constant, a 
simple periodic current is 
produced, which lags be- 
hind the phase of the im- 
pressed electromotive force 
by a constant angle. If 
the impressed electromo= 
tive force is sufficiently great to more than satu- 
rate the core, the choking coil ceases to choke 
the current. The higher the periodicity the 
greater is the choking effect of a given coil, or the 
smaller the coil may be made to produce a given 
effect. 

Since an open-magnetic circuit requires a 
greater current to saturate it than a closed-mag- 
netic circuit, the complete throttling or choking 
power of such a coil is increased by forming its 
core of a closed- magnetic circuit, i. e., of a circuit 
in which there is no air space or gap. (See Circuity 
Divided- Magnetic. Circuit, Closed- Magnetic.) 




Fig. 141. Choking- 
Coil. 



Coil, Electric 



-A convolution of in- 



sulated wire through which an electric current 
may be passed. (See Magnet, Electro) 

The term coil is usually applied to a number 
of turns or to a spool of wire. 

Coil, Impedance A term sometimes 

applied to a choking-coil. (See Coil, Chok- 
ing) 

Such a coil has a high self-induction. Its im- 
pedance is therefore high. (See Induction, Self. 
Impedance.) 



Coil, Induction 



-An apparatus con- 



sisting of two parallel coils of insulated wire 
employed for the production of currents by 
mutual induction. (See Induction, Mutual. 
Induction, Electro-Dynainic) 



Coi.] 



107 



[Coi. 



A rapidly interrupted battery current, sent 
through a coil of wire called the primary coil, 
induces alternating currents in a coil of w.re called 
the secondary coil. 

As heretofore made, the primary coil consists of 
a few turns of a thick wire, and the secondary 
coil of many turns, often thousands, of fine wire. 
Such coils are generally called Ruhmkorff coils, 
from the name of a celebrated manufacturer of 
them. 

In the form of Ruhmkorff coil, shown in Fig. 
142, the primary wire, wound on a core formed 




Fig. 142. Ruhmkorff Coil. 

of a bundle of soft iron wires, has its ends brought 
out as shown at f, f. The fine wire, forming the 
secondary coil, is wrapped around an insulated 
cylinder of vulcanite, or glass, surrounding the 
primary coil. This wire is very thin, and in some 
coils is over one hundred miles in length. 

If the core of an induction coil were made solid 
it would heat considerably and therefore cause a 
loss of energy. The core is therefore laminated, 
usually by forming it of a bundle of soft iron wire. 

Too great a division of the core, however, is 
inadvisable, since, although the eddy currents 
therein are thereby avoided, yet, too great a 
division of the core acts practically so to 
decrease the magnetic permeability that the 
greatest efficiency cannot be obtained. 

The ends of the secondary coil are connected 
to the insulated pillars A and B. 

The primary current is rapidly broken by 
means of a mercury break, shown at L and M. 

The commutator, shown to the right and front 
of the base, is provided for the purpose of cutting 
off the current through the primary, or for chang- 
ing its direction. When a battery which produces 
a comparatively large current of but a few volts 
electromotive force is connected with the pri- 
mary, and its current rapidly interrupted, a 
torrent of sparks will pass between A and B, 
having an electromotive force of many thousands 
of times the number of volts of the primary cur- 



rent, but of a correspondingly smaller current 
strength. 

In such cases, excepting losses during conver- 
sion, the energy in the primary current, or C E, 
is equal to the energy in the secondary current, 
or C E'. As much therefore as E', the electro- 
motive force of the secondary current, exceeds E, 
the electromotive force of the primary current, 
the current strength C, of the secondary, will be 
less than the current strength C, of the primary. 
This is approximately true only, and only in in- 
duction coils possessing a closed magnetic circuit. 
(See Transformer.) 

Fig. 143 shows diagramatically the arrange- 




Fig, 143. Circuit Connections of Induction Coil. 

ment and connection of the different parts of an 
induction coil. 

The core II', consists of a bundle of soft iron 
wires, each of which is covered with a thin insu- 
lating layer of varnish or oxide. A primary wire 
P P, consisting of a few turns of comparatively 
thick wire, is wound around the core, and a 
greater length of thin wire S S, is wound upon the 
primary. This is called the secondary. So as 
not to confuse the details of the figure it is repre- 
sented as a few turns. 

The terminals of the battery B, are connected 
to the primary wire, through the automatic inter- 
rupter, in the manner shown. It will be seen that 
the attraction of the core II', for the vibrating 
armature H, will break contact at the point o, and 
cause a continued interruption of the battery 
current. 

The condenser c c', is connected as shown. It 
acts to diminish the sparking at the contact points 
on breaking contact, and thus, by making the 
battery current more sudden, to make its in- 
ductive action greater. 

The reactions which take place when a simple 



Coi.] 



108 



[Coi. 



periodic electromotive force is impressed on the 
primary of an induction coil are substantially 
thus stated by J, A. Fleming : 

(i.) The application of a simple periodic im- 
pressed electromotive force produces a simple 
periodic current, moving under an effective elec- 
tromotive force of self-induction, and brings into 
existence a counter-electromotive force of self- 
induction, which causes the primary current to 
lag behind, by an angle called the angle of lag. 

(2.) The field around the primary, and, there- 
fore, the induction through the secondary, is in 
consonance with the primary current, and the im- 
pressed electromotive force in the secondary is 
in quadrature with the primary current. (See 
Consonance. Quadrature, In.) 

(3.) The secondary -impressed electromotive 
force gives rise to a secondary current moving 
under an effective electromotive force and creat- 
ing a counter electromotive force of self-induc- 
tion. 

(4.) This secondary current reacts in its turn 
on the primary, and creates what is called the 
back -electromotive force, or the reacting -induc- 
tive-electromotive force of the primary circuit. 

(5.) There is then a phase-difference between 
the primary and secondary currents, and also be- 
tween the primary -impressed electromotive force 
and the primary current. 

If, as in Fig. 144, two electric circuits are 




ECONDABY 
CIRCUIT 



Fig. 144. Electric and Magnetic Link. 

linked with a magnetic circuit, and a small 
periodic electromotive force be impressed on the 
primary, the following phenomena occur: 

(I.) A periodic primary current is set up in 
the primary circuit, which, though of the same 
periodic time as the impressed electromotive 
force, differs from it in phase. 

(2.) A wave of counter electromotive force is 
produced in the primary circuit by the inductive 
action, which does not coincide either with the 
impressed electromotive force, nor with the 
primary current. 

(3.) A wave of magnetization is produced in 
the iron core, which lags behind the primary 



current by somewhat less than 90 degrees of 
phase. 

(4.) A wave of impressed electromotive force 
is produced in the secondary circuit, due to and 
measured by the rate of change of magnetic in- 
duction in the core, and lagging 90 degrees, or 
more, behind the magnetization wave. 

(5 . ) A wave of secondary current, lagging be- 
hind the secondary electromotive force in phase, 
except where the circuit consists of a few turns of 
conductor, or is connected with an external cir- 
cuit of practically no inductance. — [Fleming.) 

Coil, Induction, Inverted — An 

induction coil in which the primary coil is 
made of a long, thin wire, and the secondary 
coil of a short, thick wire. 

By the use of an inverted coil, a current of high 
electromotive force and comparatively small cur- 
rent strength, i. e., but of few amperes, is con. 
verted or transformed into a current of compar. 
atively small electromotive force and large cur- 
rent strength. For advantages of this conversion 
see Electricity, Distribution of, by Alternating 
Currents, 

Inverted induction coils are called converters or 
transformers. (See Transformer.) 

Coil, Induction, Medical —An 

induction coil used for medical purposes. 

A form of induction coil used for medical pur- 
poses is shown in Fig. 145. 




Fig. 145. Medical Induction Coil. 

Coil, Induction, Microphone — 



—An 

induction coil, in which the variations in the 
circuit of the primary are obtained by means 
of microphone contacts. (See Microphone^ 

The carbon-button telephone transmitter is a 
microphone in its action, its electric resistance 
varying with the varying pressure caused by the 
sound waves. The carbon-button is in the prim- 
ary circuit of an induction coil, variations in 



Coi.] 



109 



[Coi. 



primary of which, under the influence of the 
sound waves, produce corresponding variations 
in the currents induced in the secondary. 

Coil, Kicking" A term sometimes 

applied to a Choking-Coil. (See Coil, Chok- 
ing) 

The term kicking-coil has arisen from the fact 
that the impedance due to self-induction opposes 
the starting or stopping of the current somewhat 
in the manner of an opposing kick. 

Coil, Magnet A coil of insulated 

wire surrounding the core of an electro-mag- 
net, and through which the magnetizing cur- 
rent is passed. (See Magnet, Electro) 

Coil, Primary That coil or con- 
ductor of an induction coil or transformer, 
through which the rapidly interrupted or alter- 
nate inducing currents are sent. 

In the Ruhmkorff induction coil the primary 
coil consists of a comparatively short length of 
thick wire, the secondary coil being formed of 
a comparatively great length of fine wire. In 
the transformer or converter, the primary coil 
consists of wire that is longer and thinner than 
that in the secondary coil. In other words, the 
transformer or converter consists of an inverted 
induction coil. (See Co it, Induction. Trans- 
former.) 

Coii, Reaction A magnetizing coil, 

surrounded by a conducting covering or 
sheathing ; which opposes the passage of 
rapidly alternating currents less when directly 
over the magnetizing coil than when a short 
distance from it. 

A term often used for choking-coil. (See 
Coil, Choking) 

Coil, Reaction, Balanced A coil 

employed in a 
system of distri- 
bution by means 
of transformers 
for maintaining 
a constant cur- 
rent in the sec- 
ondary circuit, Fig' 146. Balanced- Reaction Coil. 

despite changes in the load placed therein. 
A balanced-reaction coil is shown in Fig. 146. 




A reaction coil is placed in the circuit of lamps in 
series in a constant potential system. The sheath- 
ing of this coil is maintained in a balanced position 
by the counter weight P, and the spring S. If now 
a lamp is extinguished in the circuit, the increase 
of current, due to decreased resistance, causes the 
sheath to be deflected, and, thus increasing the 
self-induction of the coil, reduces the lamp current 
to its normal value. 

Coil, Resistance A coil of wire 

of known electrical resistance employed for 
measuring resistance. 

In order to avoid self-induction and the mag- 
netizing effects of the coils on the needles of the 
galvanometer used in electric measurements, as 
well as the disturbing effects of self-induction, the 
wire of the resistance coil is doubled on itseli 
before being wound, and its ends connected 
with the brass bars, E, E, Fig. 147. The inser- 




Fig. 147. Connections 0/ Resistance Coils. 

tion of the plug -key cuts the coil out of the cir- 
cuit by short-circuiting. (See Box, Resistance. 
Bridge \ Electric. Coil, Resistance, Standard.) 

The coils are made of German silver, or plati- 
noid, the resistance of which is not much 
affected by heat. 

Coil, Resistance, Standard A coil 

the resistance of which is that of the stand- 
ard ohm or some multiple or sub-multiple 
thereof. 

The standard ohm, as issued by the Electric 
Standards Committee of England, has the form 
shown in Fig. 148. The coil of wire is formed of 
an alloy of platinum and silver, insulated by silk 
covering and melted paraffine. Its ends are sol- 
dered to thick copper rods, r, r', for ready con- 
nection with mercury cups. The coil is at B. 
The space above it, at A, is filled with paraffine. 
A hole, at t, runs through the coil for the readv 



Coi.] 



110 



[Coi. 



insertion of a thermometer. The lower part of 
the coil, B, is immersed in water up to the shoul- 
der of A, and the water stirred from time to 




Fig. 148. Standard Ohpi. 

time. Since the coil is heated by the current, suc- 
cessive observations should be at least ten minutes 
apart. Only mild currents should be passed 
through the coils. 

Coil, Resistance, Standardized 

Resistance coils whose resistances have been 
carefully determined by comparison with a 
standard ohm or other standard coils. 

Coil, Ruhmkorff A term some- 
times applied to any induction coil, the 
secondary of which gives currents of higher 
electromotive force than the primary. (See 
Coil, Inductioji.) 

Coil, Secondary That coil or con- 
ductor of an induction coil or transformer, 
in which alternating currents are induced by 
the rapidly interrupted or alternating currents 
in the primary coil. (See Coil, Induction. 
Transformer?) 

Coil, Shunt A coil placed in a de- 
rived or shunt circuit. (See Circuit, Shunt.) 

Coil, Spark A coil of insulated wire 

connected with the main circuit in a system 
of electric gas-lighting, the extra spark pro- 




Fig. T49. Spark Coil. 

duced on breaking the circuit of which is em- 
ployed for electrically igniting gas jets. 

Spark coils are employed where the number of 



gas jets to be simultaneously lighted is not too 
great. When this number exceeds certain limits, 
the spark from an induction coil is more advan- 
tageously used. 
A spark coil is shown in Fig. 149. 

Coils, Armature, of Dynamo-Electric 

Machine The coils, strips or bars that 

are wound or placed on the armature core. 

To avoid needless resistance the wire, or other 
conductor, of the armature coils, should be as 
short and thick as will enable the desired electro- 
motive force to be obtained without excessive 
speed of rotation. 

The armature coils should enclose as many 
lines of force as possible (i. e., they should have 
as nearly a circular outline as possible). In 
drum-armatures, the breadth of the armature is 
frequently made nearly equal to its length, unless 
other considerations prevent. 

When the armature wire consists of rods or 
bars, it should be laminated or slit in planes 
parallel to the lines of force so as to avoid 
eddy currents. Other things being equal, the 




Fig. 1 jo. Series Connection of Armature Coils. 

greater the number of coils, the more uniform 
the current generated. The separate coils should 
be symmetrically disposed; otherwise irregular in- 
duction, and consequent sparking at the commu- 
tator results. 

The coils of pole-armatures should be wound near 
the poles rather than on the middle of the cores. 
In order to avoid undue heating, spaces for 
air ventilation are not inadvisable. Various con- 
nections of the armature coils are used. 

In some machines all the coils are connected in 
a closed circuit. In some, the coils are independ- 
ent of one another, and, either for the entire 
revolution, or for part of a revolution, are on an 
open-circuit. 



Coi.] 



Ill 



[Col. 



In alternating current dynamos in order to ob- 
tain the rapid reversals or alternations of current, 
which in some machines are as high as 12,000 
per minute, a number of poles of alternate polar- 
ity are employed. The separate coils that are 
used on the armature may be coupled either in 
series or in multiple-arc. 

Where a comparatively low electromotive force 
is sufficient, such as for incandescent lamps in 
multiple-arc, the separate coils are united in 
parallel; but for purposes where a considerable 
electromotive force is necessary, as for example, 
in systems of alternate current distribution, with 
converters at considerable distances from the 
generating dynamo, they are often connected in 
series, as shown in Fig. 150. 

Coils, Binding Coils of wire wound 

on the outside of the armature coils, and at 
right angles thereto, to prevent the loosening 
of the armature wires by the action of cen- 
trifugal force. 

The binding coils are generally made of hard 
brass wire. 

Coils, Compensating 1 A term some- 
times applied to the series coils placed on a 
shunt-wound dynamo. 

Coils, Conjugate — Two coils so 

placed, as regards each other, that an interrup- 
tion of the current in one produces no induced 
current in the other. 

When two coils are conjugate to each other, the 
lines of force of one do not pass through the other. 
Consequently such coils can produce no induc- 
tion in one another. 

Coils, Henry's A number of sepa- 
rate induction coils so connected that the 
currents induced in the secondary wire of 
the first coil, are caused to induce currents 
in the secondary wire of the second coil, with 
whose primary it is connected in series, and 
so on throughout all the coils. 

A series of three of Henry's coils is shown in 
Pig. 151. An intermittent battery current is sent 

d 




secondary, d, of the second coil, is connected with 
the primary, e, of the third coil, and the cur- 
rents finally induced in f, are employed for any 
useful purpose, such as the magnetization of a 
bar of iron at g. 

The current in b, is sometimes called a Secon- 
dary Current, or a Current of the Second Order; 
that induced by this secondary current in d, is 
called a Tertiary Current, or a Current of the 
Third Order y that in f, a Ctirrent of the Fourth 
Order. Henry carried these successive induc- 
tions up to currents of the Seventh Order. 

Henry's coils in reality consist of separate in- 
duction coils, connected, as above explained, in 
series. 

In Fig. 152, the tertiary current induced in 




Fig. IJ2. Tertiary Currents of Coils. 
IV, may be employed to give shocks to a person 
grasping the handles, e and f. 

Coils, Proportional Pairs of re- 
sistance coils, generally of 10, 100 and 1,000 
ohms each, forming the proportional arms of 
the balance or bridge, and employed in the box, 
or commercial form of Wheatstone's bridge. 
(See Bridge, Electric, Co7nrnercial Form 
of.) 

Cold, Production of, by Electricity 

— An absorption of energy and consequent 
reduction of temperature at a thermo-electric 
junction by the passage of an electric current 
across such junction in a certain direction. 

When an electric current passes across a thermo- 
electric junction, the junction is either heated or 
cooled. In the case of an antimony-bismuth 
couple, if the current passes from the antimony 




Fig. 151. Henry's Coils. 
into a, the secondary, b, of which is connected 
with the primary, c, of the second coil. The 



A B 

Fig. 133. Freezing of Water by Electricity. 

to the bismuth the junction is heated; if it passes 
from the bismuth to the antimony it is cooled. 
In the apparatus shown in Fig. 153, the antimony- 
bismuth couple is arranged as shown for the 



Col.] 



112 



[Com. 



freezing of water by means of the electric cur- 
rent. A and B, represent plates of antimony and 
bismuth respectively. A small cavity, at E, serves 
to hold a drop of water. When a current has 
passed in the direction shown by the arrows, a 
drop of water, previously cooled to the tempera- 
ture of melting ice, is solidified by the lowering 
of the temperature at the junction. 

Collecting Brushes of Dynamo-Electric 
Machine. — (See Brushes, Collecting, of 
Dynamo-Electric Machine.) 

Collectors, Electric Devices em- 
ployed for collecting or taking off electricity 
from a moving electric source. 

Collectors of Electric Frictional Ma- 
chines. — The metallic points that collect the 
charge from the glass plate or cylinder of a 
frictional electric machine. 

Collectors of Dynamo Electric Machines. 
— The brushes that rest on the commutator 
cylinder, and carry off the current generated 
on the rotation of the armature. 

Collectors are properly called commutators 
when they are employed to cause an alternate 
current to become continuous, or to flow in one 
and the same direction. 

Colloids. — One of the two classes into 
which substances are separated by dialysis. 

By dialysis bodies are separated into crystal- 
loids, or bodies capable of crystallizing, and col- 
loids or jelly -like bodies, incapable of crystallizing. 
Colloids possess great cohesion and but slight 
diffusibility. (See Dialysis.) 

Colombin. — An insulating substance, con- 
sisting of a mixture of sulphate of barium 
and sulphate of calcium, placed between the 
parallel carbons of the Jablochkoff candle. 

Column, Barometric — A column, 

usually of mercury, approximately 30 inches 
in vertical height, sustained in a barometer, 
or other tube, by the pressure of the atmos- 
phere. 

The space above the barometric column con- 
tains a vacuum known as the Torricellian vac 
uum. (See Vacuum, Torricellian.') 

Column, Electric A term formerly 

applied to a voltaic pile. (See Pile, Voltaic?) 
Colza Oil.— (See Oil, Colza.) 



Combination Gas Fixtures. — (See Fix- 
tures, Gas, Combination.) 

Combined Tangent and Sine Galvanom- 
eter. — (See Galvanometer, Combined Tan- 
gent and Sine?) 

Comb Lightning Arrester. — (See Arrester* 
Lightning, Comb?) 

Comb Protector.— (See Protector, Comb) 

Commercial Efficiency. — (See Efficiency \ 
Commercial?) 

Commercial Efficiency of Dynamo. — 
(See Efficiency, Commercial, of Dynamo?) 

Commercial Form of Electric Bridge.— 
(See Bridge, Electric, Commercial Form of.) 

Communicator, Electric A term 

formerly employed for a telegraphic key. (See 
Key, Telegraphic?) 

Commutating Transformers, Distribu- 
tion of Electricity by (See Elec- 
tricity, Distribution of, by Cojnmutating 
Transformers?) 

Commutation. — The act of commuting, as 
of currents. 

Commutation, Diameter of In a 

dynamo-electric machine a diameter on the 
commutator cylinder on one side of which 
the differences of potential, produced by the 
movement of the coils through the magnetic 
field, tend to produce a current in a direction 
opposite to those on the other side. 

That diameter on the commutator cylinder 
of an open-circuited armature that joins the 
points of contact of the collecting brushes. 

Thus in Fig. 154, the directions of the induced 
electromotive forces are indicated by the arrows. 
The diameter of commutation is therefore the line 
n n'. The term neutral line is also sometimes 
given to this line. It lies at right angles to the 
line of maximum magnetization m m. 

In a; closed-circuited armature, that is, in an arm- 
ature the coils of which are connected in a closed 
circuit, the collecting brushes rest on the commu- 
tator cylinder at the neutral line, or on the diame- 
ter of commutation. 

In an open-circuited armature, however, where 
the coils are independent of each other, the 
collecting brushes must be set at m m, at right 
angles to the neutral line n n. The term diame- 



Com.] 113 

ter of commutation is, therefore, often applied to 
this second position. According to this use of the _ 



[COHU 




Fig. IJ4> Diameter of Commutation. 

term, the diameter of commutation is that diameter 
on the commutator which joins the points of con- 
tact of the collecting brushes. 

The neutral linenn', Fig. 154, it will be noticed 
does not occupy a vertical position, but is dis- 
placed somewhat in the direction of rotation, thus 
necessitating the shifting of the brushes forward' 
in the direction of rotation. This necessary shift- 
ing of the brushes is known technically as the 
lead of the brushes. (See Lead, Angle of.) 

It will thus be seen that the term diameter of 
commutation is used in two different senses. 

In reality, the term refers to the position of cer- 
tain points on the commutator as distinguished 
from points on the armature coils. On the com- 
mutator, the diameter of commutation is the line 
drawn through the two commutator bars at which 
the currents from the two sides are opposed to 
each other. 

It is evident that the commutator may be inten- 
tionally twisted with respect to the armature, so 
as to bring its diameter of commutation into any 
desired convenient position. 

Commutation, Dissymmetry of 

A commutation in which the neutral line does 
not coincide with a diameter of the commu- 
tator. (See Co?nmutation, Diameter of.) 

Commutator. — In general, a device for 
changing the direction of an electric current. 

Commutator, Burning" at Arcing 

and consequent destructive action on the 
commutator segments of a dynamo-electric 
machine. 

When the arcing is pronounced, the intense 
heat soon destroys the commutator. 

Commutator Cylinder, Neutral-Line of 

( See Line, Neutral, of Commutator 

Cylinder,) 



Commutator, Dynamo-Electric Machine 

• That part of a dynamo-electric ma- 
chine which is designed to cause the alter- 
nating currents produced in the armature to 
flow in one and the same direction in the ex- 
ternal circuit. 

One end of an armature coil is connected with 
A', Fig. 155, and the 
other with A. The brushes 
are so set that A, and A', 
are in contact with B', 
and B, respectively, as 
long as the current flows 
in the same direction in the 
armature coil connected 
therewith, but enter into 
contact with B, and B', Fig. ijs- Commutator 
when the current changes of Dynamo - Electric 
its direction, and continue Machine. 
in such contact as long as it flows in this direc- 
tion. By the use of a commutator the current 
will therefore flow through any circuit connected 
with the brushes in one and the same constant 
direction. 





Two-part Commutator. 

In action, the commutator is subject to wear 
from the friction of the brushes, and the burning 
action of destructive sparks. The commutator 

A 




Fig. 157. Two-part 
Commutator. 



Fig. 158. Two-part 
Commutator. 



segments are, therefore, made of comparatively 
thick pieces of metal, insulated from one another, 



Com.] 



114 



[Conu 




and supported on a commutator cylinder usually 
placed on the shaft of the armature. 

The ends of the armature coils are connected 
to commutator strips or segments. 

The number of metallic pieces or segments, A. 

and A', on the cotnmutator cylinder depends on 

the number, arrangement and connection of the 

armature coils, and on the 

c 

disposition of the magnetic 
field of the machine. 

Figs. 156, 157 and 158 
show the connections of an 
armature coil to the plates of 
a two-part commutator. 

A four-part commutator 

for a ring- armature, and the **>#>' 

Commutator. 

connections of the coils 

thereto, are shown in Fig. 159. 

The commutator strips may either connect the 
separate coils in a closed-circuited armature, in 
which the coils are all connected with one an- 
other, or, in an open-circuited armature, in which 
the separate coils are independent of one another. 

Commutator, KuhnikorfFs A name 

given by Ruhmkorff to a device placed on his 
induction coil for the purpose of changing or 
reversing the direction of the battery current 
through the primary. 

This reverser is shown in Fig. 160. (See 
' Coil, Ruhmkorff.) 

V 




Fig. 160. Ruhmkorff 's Commutator. 

Two metallic strips, V, V, supported on a 
cylinder of insulating material, are in contact with 
the battery terminals A, and D, through two 
vertical springs that b?ar on them. On a half 
rotation of the cylinder by the thumb screw L, 



the strips V, V, change places as regards the ver- 
tical springs, and thus reverse the direction of 
the battery current. 
Commuted Currents. — (See Currents, 



Commuter, Current Any appa- 
ratus by means of which electrical currents, 
flowing alternately in different directions, 
may be caused to flow in one and the same 
direction. 

A Commutator. 

Commuting'. — Causing to flow in one and 
the same direction. 

Commuting Currents. — (See Currents, 
Commuting?) 

Compartment Manhole of Conduit.— (See 
Manhole, Compartment, of Conduit?) 

Compass, Azimuth — A compass 

used by mariners for measuring the horizon- 
tal distance of the sun or stars from the mag- 
netic meridian. (See Azi?nutk, Magnetic.) 

A mariner's Compass. 

A single magnetic needle, or several magnetic 
needles, are placed parallel to one another on the 
lower surface of a card, called the compass card. 
This card is divided into the four cardinal points, 
N, S, E and W, and these again subdivided into 
thirty-two points called Rhumbs. 

In the azimuth compass these divisions are sup- 
plemented by a further division into degrees. 

A form of azimuth compass is shown in Fig. 
161. In order to maintain the compass box in a 




Fig. 16 1. Azimuth Compass* 

horizontal position, despite the rolling of the ship, 
the box, A B, is suspended in the larger box, P 
Q, on two concentric metallic circles, C D, and 



Com.] 



115 



[Com. 



E F, pivoted on two horizontal axes at right angles 
to each other. This kind of support is technic- 
ally termed Gimbals. Sights G, H, are provided 
for measuring the magnetic azimuth of any ob- 
ject. 

Compass, Boxing the ■ —Naming, 

consecutively, all the different points or 
rhumbs of the compass from any one of them. 
(See Compass, Points of.) 

Compass-Card. — (See Card, Compass) 



Compass, Inclination 



-A magnetic 



needle moving freely in a single vertical plane, 
and employed for determining the angle of 
dip at any place. 

An Inclinometer. (See Inclinometer) 
A dipping circle. (See Circle, Dipping) 
The needle M, Fig. 162, is supported on knife 




Fig. 162 Inclination Compass. 

edges so as to be free to move only in the vertical 
plane of the graduated vertical circle C C. This 
circle is movable over the horizontal graduated 
circle H II. In order to determine the true angle 
of dip, the vertical plane in which the needle is 
free to move must be placed exactly in the plane 
of the magnetic meridian. 

To ascertain this plane the vertical circle is 
moved until the needle points vertically down- 
wards. It is then in a plane 90 degrees from the 
magnetic meridian. The vertical circle is then 
moved over the horizontal circle 90 degrees, in 
which position it is in the plane of the magnetic 
meridian, when the true angle of the dip is read off. 

For an explanation of the reason of this see 



Component, Horizontal and Vertical, of the 
Earth's Magnetism. 

Compass, Mariner's A name often 

applied to an azimuth compass. (See Com- 
pass, Azimuth) 

Compass, Points of The thirty-two 

points into which a compass card is divided. 

Sixteen of these points are shown in Fig. 163. 
N 




Fig. 163. Points of Compass. 

The position of the remaining points will 
readily seen by an inspection of the figures. 
These points are as follows: 



be 



I. North. 


17. 


South. 


2. N. by E. 


18. 


S. by W. 


3. N. N. E. 


19. 


S. S. W. 


4. N. E. by N. 


20. 


S. W. by S. 


5. N. E. 


21. 


S. W. 


6. N. E. by E. 


22. 


S. W. by W. 


7. E. N. E. 


23. 


W. S. W. 


8. E. by N. 


24. 


W. by S. 


9. East. 


25. 


West. 


10. E. by S. 


26. 


W. by N. 


11. E. S. E. 


27. 


W. N. W. 


12. S. E. by E. 


28. 


N. W. by W. 


13. S. E. 


29. 


N. W. 


14. S. E. by S 


30. 


N. W. by N. 


15. S. S. E. 


3i. 


N. N. W. 


16. S. by E. 


32. 


N. by W. 


Boxing the Compass 


consists in naming all 


these points consecutively 


from 


any one of them. 


The direction in which the ship is sailing is de- 


termined by means of a point fixed on the inside of 


the compass box, directly 


in the line of the ves- 


sel's bow. 






Compass, Rhumbs 


of 


The points 


of a mariner's compass. 


(See Compass, 


Points of) 







Com.] 



116 



[Com. 



Compensated Alternator.— (See Alter- 
nator, Co?npensated.) 
Compensated Excitation of Alternator. 

— (See Alternator, Compensated Excita- 
tion of.) 

Compensating Coils.— (See Coils, Com- 
pensating^) 

Compensating Magnet. — (See Magnet, 
Compensating) 

Complement of Angle.— (See Angle, Com- 
plement of.) 

Completed-Circuit— (See Circuit, Com- 
pleted) 

Component. — One of the two or more sep- 
arate forces into which any single force may 
be resolved ; or, conversely, the separate forces 
which together produce any single resulting 
force. 

When two or more forces act simultaneously to 
produce motion in a body, the body will move 




Fig. lb 4. Composition 0/ Forces. 



with a given force in a single direction called the 
resultant. The separate forces, or directions of 
motion, are called the components. 

Two forces acting simultaneously on a body at 
A, Fig. 164, tending to move it in the direction 




Fig 165. Resolution oj Firces. 



of the arrows, along A B, and A C, with intensi- 
ties proportioned to the lengths of the lines A B, 
and A C, respectively, will move it in the direc- 
tion A D, obtained by drawing B D, and D C, 



parallel to A C, and A B, respectively, and then 
drawing A D, through the point of intersection, 
D. This is called the Composition of Forces. 
A D, is the resultant force, and A B and A C, 
are its components. 

Conversely, a single force, acting in the direc- 
tion of D B, Fig. 165, against a surface, B C, 
may be regarded as the resultant of the two sep- 
arate forces, D E, and D C, one parallel to C B, 
and one perpendicular to it. D E, being parallel 
to C B, produces no pressure, and the absolute 
effect of the force will, therefore, be represented 
by CD. 

This separation of a single force into two or 
more separate forces is called the resolution of 
forces ; the force, D B, being resolved into the 
components, D E and D C. 

Component Currents. — (See Currents, 
Component) 

Component, Horizontal, of Earth's Mag- 
netism That portion of the earth's 

directive force which acts in a horizontal di- 
rection. 

That portion of the earth's magnetic force 
which acts to produce motion in e. com- 
pass needle free to move in a horizontal plane 
only. 

Let A B, Fig. 166, represent the direction and 
magnitude of the earth's magnetic field on a mag- 
netic needle. The magnetic force will lie in the 
plane of the magnetic merid- 
ian, which will be assumed to D A 
be the plane of the paper C A 
D. The earth's field, A B, can 
be resolved into two compo- 
nents, A D, the horizontal com- 
ponent, and A C, the vertical 
component. 

In the case of a magnetic 
needle, like the ordinary com- 
pass needle, which is free to 
move in a horizontal plane only, 
the horizontal component alone 

directs the needle. A weight f e ' . ' .,, 
b ponents of Earth s 

is applied to balance the vertical Magnetism. 
component. 

When the needle is free to move in a vertical 
plane, and this plane corresponds with that of 
the magnetic meridian, the entire magnetic force, 
A B, acts to place the needle, supposed to be 
properly balanced, in the direction of the lines of 
force of the earth's magnetic field at that point. 




Com.] 



117 



[Con. 



Component, Yertical, of Earth's Magnet- 
ism — That portion of the earth's 

directive force which acts in a vertical direc- 
tion. 

In the vertical plane at right angles to the plane 
of the magnetic meridian, the vertical component 
alone acts, and the needle points vertically down- 
wards, in no matter what part of the earth it 
may be. In Fig. 166, A C, is the vertical com- 
ponent of the earth's directive force. 

Composite Balance. — (See Balance, Com- 
posite?) 

Composite-Field Dynamo. — (See Dynamo, 
Composite-Field) 

Composition of Forces. — (See Forces, 
Co?nposition of) 

Compound Arc.— (See Arc, Compound) 

Compound, Binary In chemistry, 

a compound formed by the union of two 
different elements. 

Water is a binary Compound, being formed by 
the union of two atoms of hydrogen with one 
atom of oxygen. Its composition is expressed in 
chemical symbols, H 2 0, which indicates that two 
atoms of hydrogen are combined, or chemically 
united, with one atom of oxygen. Water is 
therefore a binary compound, because it is formed 
of two different elementary substances. 

Compound, Chatterton's A com- 
pound for cementing together the alternate 
coatings of gutta-percha employed on a cable 
conductor, or for filling up the space between 
the strand conductors. 

The composition of Chatterton's compound is 
as follows: 

Stockholm tar I part by weight. 

Resin I " " 

Gutta-percha 3 " '• 

— {Clark &° Sabine.) 

Compound Circuit. — (See Circuit, Com- 
pound) 

Compound, Clark's A compound 

for the outer casing of the sheathing of sub- 
marine cables. 

The composition of Clark's compound is as fol- 
lows: 



Mineral pitch ...... 65 parts by weight. 

Silica 30 " " 

Tar 5 " " 

— {Clark 6° Sabine.) 

Compound - Horseshoe Magnet. — (See 
Magnet, Compound-Horseshoe) 

Compound Magnet. — (See Mag?iet, Com- 
pound) 

Compound Radical. — (See Radical, Com- 
pound) 

Compound-Winding of Dynamo-Electric 
Machines. — (See Winding, Compound, of 
Dynamo-Electric Machine) 

Compound- Wound Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Compound- Wound) 

Compound-Wound Motor.— (See Motor, 
Compound- Wound) 

Concentration of Lines of Force. — (See 
Force, Lines of, Concentratioti of) 

Concentric Carbon Electrodes. — (See 
Electrodes, Concentric Carbon) 

Concentric Cylindrical Carbons.— (See 
Carbons, Concentric Cylindrical) 

Condenser. — A device for increasing the 
capacity of an insulated conductor by bring- 
ing it near another insulated earth-connected 
conductor, but separated therefrom by any 
medium that will readily permit induction to 
take place through its mass. 

A variety of electrostatic accumulator. 

If the conductor A, Fig. 167, standing alone 




Fig. 167. sEpinus Air Condenser. 

and separated from other conductors, be con- 
nected with an electric machine, it will receive 
only a very small charge. 



Con.] 



118 



[Con. 



If, however, it be placed near C, but separated 
from it by a dielectric, such as a plate of glass 
B, and C, be connected with the ground, A, will 
receive a much greater charge. (See Dielectric.') 

Suppose, for example, that A, be connected 
with the positive conductor of a frictional electric 
machine, it will by induction establish a negative 
charge on the surface C, nearest it, and repel 
a positive charge to the earth. The presence of 
these two opposite charges on the opposed sur- 
faces of A and C, permits A, to receive a fresh 
charge from the machine. (See Induction, 
Electrostatic.) 

The charge in a condenser in reality resides 
on the opposite surfaces of the glass, or other 
dielectric separating the metallic coatings, as can 
be shown by removing the coatings after charg- 
ing. 

The condenser resulted from the discovery of 
the Leyden jar. (See Jar, Ley den.) 

The capacity of a condenser is measured in 
microfarads. (See Farad.) 

In practice condensers are made of sheets of 
tin foil, connected to A and B, respectively, and 
separated from one another by sheets of oiled 
silk, paraffined paper, or thin plates of mica, as 
shown in Fig. 168. 




Fig. 1 68. Condenser. 

A Leyden jar or condenser does not store elec- 
tricity any more than a storage battery does. 
The same quantity of electricity passes out of the 
opposite coating of the jar that is passed into the 
other coating. The jar, therefore, possesses no 
store of electricity. What it really possesses is a 
store of electrical energy. 

According to Ayrton, if the capacity of a con- 
denser, in farads, be F, and the difference of po- 
tential, with which it is charged, be V, volts, the 
store of electric energy it possesses, or the work it 
can do when discharged, is, 

FX V* 
Work = — — — - foot-pounds. 
2.712 r 

Condenser, Adjustable ■ — A con- 
denser, the plates of which can be readily 
adjusted so as to obtain the same capacity 
as that of the conductor to be measured. 



In order to obtain a comparatively wide range 
of adjustability, a condenser is composed of say 
four separate sections: consisting of one of 2 
microfarads, one of I microfarad and two of J 
microfarad, thus making in all 4 microfarads. 

Condenser, JEpinus A name given 

to an early form of condenser. (See Con- 
denser^) 

Condenser, Air —A condenser in 

which layers of air act as the dielectric. 

A form of air condenser is shown in Fig. 169. 




Fig. 169. Air Condenser. 

It consists essentially of one set of thin plates of 
glass partially coated on both sides with sheets of 
tin foil, so as to leave uncoated a space of about 
one inch around the edge of the glass. The glass 
plates do not act as dielectrics, but merely as sup- 
ports for the tin foil, hence the foil on both sides 
of the plates is connected electrically. 

Another set of plates alternating with the above 
have the tin foil placed over the whole surface of 
the glass. 

These plates are placed, alternately, over one 
another on a stand between guide rods of vulcan- 
ite E, E, E, E, in the manner shown, and are 
separated from one another by fragments of glass 
of the same thickness. The plates with the foil 
over their entire surface are all connected to- 
gether and to the terminal B, to form the outer 
coating, and the plates with the foil over nearly 
all their surfaces are all connected together and 
to the terminal A, to form the inner coating of 
the condenser. 

There is thus formed a condenser in which 
practically two extended conducting surfaces are 



Con.] 



119 



[Con. 



separated from each other by a thin layer of air, 
which acts as the dielectric. 
Condenser, Alternating-Current ■ 

A condenser suitable for use in connection with 
a system for the distribution of electric energy 
by means of alternating currents. 

Alternating-current condensers must have a very 
thin dielectric in order to avoid too great bulk. 
This, of course, introduces a difficulty as regards 
liability of failure of insulation, which must be 
carefully avoided. 

Condenser, Armature of (See Arm- 
ature of a Condenser) 

Condenser, Capacity of The quan- 
tity of electricity in coulombs a condenser is 
capable of holding before its potential in volts 
is raised a given amount. 

The ratio between the quantity of electric- 
ity in coulombs on one coating and the poten- 
tial difference in volts between the two coat- 
ings. — [Ayr ton) 

The capacity is directly proportional to the 
charge Q. and inversely proportional to the po- 
tential V, or, 

K Q 

or, since Q = KV, the quantity of electricity re- 
quired to charge a condenser to a given potential 
is equal to the capacity of the condenser multi- 
plied by the potential through which it is carried. 

The capacity of a condenser increases in direct 
proportion to the increase in the area of its coat- 
ings. 

When the coatings are plane and parallel to 
each other, the capacity of the condenser is in the 
inverse ratio to the distance between the coatings. 

Condenser, Coating' of- (See Coat- 
ing of Condenser.) 

Condenser, Plate -A condenser, the 

metallic coatings of which are placed on 
suitably supported plates. 

Condenser, Poles of . — (See Poles of 

Condenser.) 

Condenser, Time-Constant of 

The time in which the charge of a condenser 
falls to the 1-2.7 1828 part of its original 
value. 

Condensers, Distribution of Electricity 
by Means of —(See Electricity, Distri- 



bution of. by Alternating Currents, by mea?ts 
of Condensers . Electricity, Distribution of, 
by Continuous Currents, by means of Con- 
densers) 

Conduct. — To pass electricity through con- 
ducting substances. 

To determine the general direction in which 
electricity shall pass through the ether or 
dielectric surrounding the so-called conduct- 
ing substance. (See Conduction, Electric) 

Conductance. — A word sometimes used in 
place of conducting power. 
Conductivity. 

Conductance, Magnetic — A word 

sometimes used instead of magnetic permea- 
bility. (See Permeability Magnetic) 

The magnetic conductance is equal to the total 
induction through the circuit divided by the 
magnetizing force. 

Conducting Cord.— (See Cord, Conduct- 
ing) 

Conducting, Electrical Possessing 

the power of passing electricity through any 
conducting substance. 

Possessing the power of determining the 
direction in which electricity shall pass through 
the ether surrounding a substance, (See 
Conductor) 

Conducting Power.— (See Power Con- 
ducting) 

Conducting Power for Electricity.— (See 

Power, Conducting, for Electricity) 

Conducting Power for Lines of Mag- 
netic Force. — (See Force, Magnetic, Lines 
of, Conducting Power of,) 

Conducting Power, Tables of 

(See Power, Conducting , Tables of.) 

Conduction Current.— (See Current, Con- 
duct ion) 

Conduction, Disruptive A species 

of conduction in which the resistance of the 
conductor is suddenly overcome. 

. Disruptive conduction is seen in the disruptive 
discharge of a condenser, or Ley den jar. 

Conduction, Electric The so- 



Con.] 



120 



[Con, 



called flow or passage of electricity through 
a metallic or other similarly acting substance. 

The ability of a substance to determine the 
direction in which electric energy shall be 
transmitted through the ether surrounding it. 

The ability of a substance to determine the 
direction in which a current of electricity 
passes from one point to another. 

When a conducting wire has its ends connected 
with an electric source, a current of electricity is, 
in common language, said to flow through the wire, 
and this was formerly believed to be a correct 
statement. According to modern views, however, 
the electric energy is believed to pass through the 
ether or other dielectric surrounding the con- 
ductor, the so-called conductor forming merely 
a sink, where the electrical energy dissipates 
itself. The conductor simply acts to direct the 
current. 

Since, however, the energy practically passes 
by means of, and in the general direction of the 
conductor, there is no objection in speaking of 
the electricity as flowing through the conductor. 

Conduction, Electric, Disruptive 

A conduction of electric energy which ac- 
companies a disruptive discharge. (See 
Discharge, Disruptive^ 

Conduction, Electric, Metallic —A 

conducting of electric energy of the same char- 
acter as that which occurs in metallic sub- 
stances. 

Conduction, Electrolytic A term 

sometimes employed to indicate the passage 
of electricity through an electrolyte. 

There is no passage of electricity through an 
electrolyte in the same sense as through an ordi- 
nary conductor. 

When, through electrolysis, an electromotive 
force is brought to bear on a molecule of say 
HC1, it is assumed by some that the liberated 
hydrogen atoms travel on the whole in one di- 
rection, and the liberated chlorine atoms in the 
opposite direction. The atoms thus moving 
through the liquid may by their electric charges 
be assumed to convey electricity, and this fact 
has given rise to the term electrolytic conduc- 
tion. 

In electrolytic conduction the charges are 
necessarily equal, but the speeds of their motion 
are unequal. In a given liquid, each atom has 



its own rate of motion, no matter with what it 
has been combined. Hydrogen travels faster 
than any other kind of atom. The conductivity 
of a liquid depends on the sum of the speeds with 
which the two opposed atoms travel. 

This assumed double stream of oppositely mov- 
ing atoms is denied by most physicists. (See 
Hypothesis, Grotthus. ) 

Conductive-Discharge.—. (See Discharge, 
Conductive^) 

Conductivity, Electric The recip- 
rocal of electric resistance. 

Since the conductivity is greater the less the re- 
sistance, the conductivity will be equal to the recip- 
rocal of the resistance, and may be so defined. The 

conductivity is therefore equal to — # 

Conductivity, Equivalent A con- 
ductivity equal to the sum of several conduc- 
tivities. 

Conductivity per Unit of Mass.— The re- 
ciprocal of the resistance of a substance per 
unit of mass. 

Conductivity per Unit of Volume. — The 
reciprocal of the resistance of a substance 
per cubic centimetre or per cubic inch. 

The resistance is measured from one face of 
the cube to the opposite face. 

Conductivity Resistance. — (See Resist- 
ance, Conductivity^) 

Conductivity, Specific The par- 
ticular conductivity of a substance for elec- 
tricity. 

The specific or particular resistance of a 
given length and unit of cross-section of a 
substance as compared with the same length 
and area of cross-section of some standard 
substance. 

Conductivity, Specific Magnetic — 

The specific or particular permeability of a 
substance to lines of magnetic force. 

The specific magnetic conductivity is measured 
by the ratio of the magnetization produced to the 
magnetizing force which produces it. 

The specific magnetic conductivity is the an- 
alogue of specific inductive capacity, or conduc- 
tivity for lines of electrostatic force. It is also the 
analogue for specific conducting power for heat. 



Con.] 



121 



[Con, 



Conductor. — A substance which will per- 
mit the so-called passage of an electric current. 

A substance which possesses the ability of 
determining the direction in which electricity 
shall pass through the ether or other dielec- 
tric surrounding it. 

Some electrolytes, such, for example, as vari- 
ous mixtures of sulphuric acid and water, possess 
a true power of conducting electricity, and there- 
fore have a specific resistance. Generally, how- 
ever, the passage of the electrolyzing current is 
regarded as different from that of a current which 
merely heats the conductor. 

The space or region around a conductor 
through which an electric current is passing has 
a magnetic field produced in it. 

The term conductor is opposed to non-conductor ', 
or a substance which will not permit the passage 
of an electric current through it after tne manner 
of a conductor. 

The terms conductors and non-conductors are 
only relative. There are no such things as 
either perfect conductors or perfect non con- 
ductors. 

Conductors in general, are distinguished from 
electrolytes, in that the latter do not allow the 
electricity to pass save by undergoing a chemical 
decomposition. 

Conductor, Anisotropic A con- 
ductor which, though homogeneous in struc- 
ture like crystalline bodies, has different 
physical properties in different directions, just 
as crystals have different properties in the 
direction of their different crystalline axes. 

Anisotropic conductors possess different powers 
of electric conduction in different directions. 
But in opposite directions along the same axis their 
conductivity is equal. They differ in this respect 
from isotropic conductors. (See Conductor, Iso- 
tropic. ) 

Conductor, Anti-Induction A con- 
ductor so constructed as to avoid injurious 
inductive effects from neighboring telegraphic 
or electric light and power circuits. 

Such anti-induction conductors sometimes con- 
sist of a conductor for constant currents and a 
metallic shield surrounding the conductor, and 
designed to prevent induction from taking place 
in the wire itself. 

The anti-induction conductor generally con- 



sists of twin conductors surrounded by ordinary 
insulation and sometimes enclosed by some form 
of metallic shield, in order to prevent the action 
of electrostatic induction. 

When a periodic current is to be transmitted 
through a conductor, the most effective way of 
annulling its inductive effects on neighboring cir- 
cuits is to place the lead of the conductor in the 
axis of another conductor, used as a return. In 
other words, to employ concentric cylinders, in- 
sulated from one another and from the earth. 
Under these conditions, calling the current in one 
direction positive, and in the other direction 
negative, the shielding action will be perfect 
when the algebraic sum of the currents in the 
core and sheath are zero. 

The same effect is obtained in metallic circuits, 
by placing the leads parallel to the return, and 
crossing and recrossing the wires repeatedly. 
(See Connection, Telephonic Cross.) 

Elihu Thomson renders ordinary telephone 
conductors, arranged as single lines with earth 
returns, free from induction by means of the 
counter-electromotive force produced in a coil of 
wire by the disturbing cause. 

In applying this system to the case of an elec- 
tric arc or power line passing alongside a tele- 
phone line, a wire coil, whose turns are pro- 
portioned in number to the induction to be bal- 
anced, is introduced into the electric light line 
and placed near another coil of finer wire inserted 
as a loop in the telephone circuit. The second coil 
is placed parallel to or inclined at an angle to the 
first coil. In practice, the second coil is inclined 
until the counter-induction set up in the tele- 
phone wire is equal to that produced in the main 
line, and silence is thus produced, so far as in- 
duction is concerned, in the telephone. 

Conductor, Armored A conduc- 
tor provided with a covering or sheathing of 
metal placed over the insulating covering for 
protection from abrasion or external wear. 

Armored conductors are used in situations 
where the conductor is exposed to abrasion or 
other external wear. 

Conductor, Branch — A conductor 

placed in a shunt circuit. (See Circuit, 
Shunt.) 

Conductor, Closed-Circuited — A 

conductor connected as a closed or com- 
pleted circuit. 



Con.] 



122 



[Con, 



Conductor, Conjugate 



■In a system 



of linear conductors, any pair of conductors 
that are so placed as regards each other that 
a variation of the resistance or the electro- 
motive force in the one causes no variation in 
the current of the other. 

Conductor, Earth-Circuited —A 

conductor connected to the ground, or to an 
earth-connected circuit. 

Conductor, House-Service A term 

employed in a system of multiple incan- 
descent lamp distribution for that portion of 
the circuit which is included between the ser- 
vice cut-out and the centre or centres of dis- 
tribution, or between this cut-out and one or 
more points on house mains. 

Conductor, Isotropic A conduc- 
tor which possesses the same powers of elec- 
tric conduction in all directions. 

An electrically homogeneous conducting 
medium. 

Conductor, Leakage A conductor 

placed on a telegraph circuit for the purpose 
of preventing the disturbing effects of leakage 
into a neighboring line by providing a direct 
path for such leakage to the earth : 

The leakage conductor, as devised by Varley 
consists of a thick wire attached to the telegraph 
pole. The lower end of the conductor is grounded, 
and its upper end projects above the top of the 
pole. 

There exists some doubt in the minds of expe- 
rienced telegraph engineers whether it is well to 
apply leakage conductors to telegraphic or tele- 
phonic lines of over 12 or 15 miles in length, 
since such conductors greatly increase the electro- 
static capacity of the line, and thus cause serious 
retardation. 

Conductor, Lightning — A term 

sometimes used for a lightning rod. (See 
Rod, Lightning) 

Conductor, Open-Circuited — A con- 
ductor arranged as an open or broken circuit. 

Conductor, Potential of —The rela- 
tion existing between the quantity of elec- 
tricity in a conductor and its capacity. 

A given quantity of electricity will raise the 



potential of a conductor higher in proportion as 
the capacity of the conductor becomes less. 

Conductor, Potential of, Methods of 

"Varying The potential of a conductor 

may be varied in the following ways : 

(1.) By varying its electric charge. 

(2.) By varying its size or shape without alter- 
ing its charge. 

(3.) By varying its position as regards neigh* 
boring bodies. 

This resembles the case of a gas whose tension! 
or pressure may be varied as follows, viz.: 

(1.) By varying the quantity of gas. 

(2.) By varying the size of the gas holder .in 
which it is kept, and 

(3.) By varying the temperature. 

Difference of potential, therefore, corresponds — 

(1.) With difference of level in liquids. 

(2.) With difference of pressure in gases. 

(3.) With difference of temperature in heat. 

— {Ayr ton.) 

Conductor, Prime — The positive 

conductor of a frictional electric or electro- 
static machine. (See Machine, Frictional 
Electric.) 

Conductor, To Short-Circuit a 

To shunt a conductor with a circuit of com- 
paratively small resistance. 

Conductor, Underground An elec- 
tric conductor placed underground by actual 
burial or by passing it through underground 
conduits or subways. 

Underground conductors, though less unsightly 
than the ordinary aerial conductors, require to 
be laid with unusual care to render them equally 
safe, since, when contacts do occur, all the wires 
in the same conduit are apt to be simultaneously 
affected, thus spreading the danger in many dif- 
ferent directions. They are, however, less liable to 
dangers arising from occasional accidental crosses 
or contacts. 

Conductors, Service —Conductors 

employed in systems of incandescent lighting 
connected to the street mains and to the 
electric apparatus .placed in the separate 
buildings or areas to be lighted. 

Conduit, Cement-Lined — A cable 

conduit, the separate ducts of which are sur- 
rounded by any suitable cement. 



Con.] 



123 



[Con. 



Conduit, Handhole of (See Hatid- 

hole of Conduit?) 

Conduit, Manhole of (See Man- 
hole of Conduit) 

Conduit, Multiple ■ —A conduit 

formed of concrete or other insulating - mate- 
rial, and furnished with a number of separate 
ducts. 

Conduit, Open-Box —A conduit 

consisting of an open box of wood placed in 
a trench and closed with a wooden cover 
after the introduction of the cable. 

Cables or wires may be drawn through such 
conduits in the usual manner. 

Conduit, Rodding a Introducing a 

wire or rope into the duct of a closed conduit 
preparatory to drawing the cable through. 

Various methods are in use for rodding a con- 
duit. One much followed consists in using sec- 
tions of gas pipe, the ends of which are furnished 
with screw threads. 

The sections are about four feet in length. One 
section is pushed into the duct at one manhole 
and the successive sections are introduced into 
the duct and screwed onto the section in the duct 
and pushed through until a sufficient length is 
obtained to reach the next manhole, a rope or 
cable is then pulled through from one manhole to 
the next. 

Conduit, Underground Electric — 

An underground passageway or space for 
the reception of electric wires or cables. (See 
Subway, Electric?) 

Congelation. — The act of freezing, or the 
change of a liquid into a solid on loss of heat, 
or change of pressure. 

Conjugate Coils.— (See Coils, Conjugate) 

Connect. — To place or bring into electric 
contact. 

Connecting. — Placing or bringing into elec- 
tric contact. 

Connection for Intensity. — Connection in 
series. (See Connection, Series?) 

This term is now nearly obsolete. 

Connection for Quantity.— Connection in 
multiple. (See Connection, Multiple) 

This term is now nearly obsolete. 



Connection, Mercurial — A form 

of readily adjustable connection obtained by 
providing the poles of one piece of electric 
apparatus with cups or cavities filled with 
mercury, into which the terminals of another 
piece of apparatus are dipped in order to 
place the two in circuit with each other. 

This form of connection is used particularly 
when a very perfect contact or one free from 
friction is desired. 

Connection, Multiple Such a con- 
nection of a number of separate electric 
sources, or electro-receptive devices, or circuits, 
that all the positive terminals are connected 
to one main or positive conductor, and all the 
negative terminals are connected to one main 
or negative conductor. 

In the multiple connection of a number of 
electro-receptive devices, when the devices are 
connected as above described to positive and 
negative leads that are maintained at a constant 
difference of potential, the current passes through 
the devices from one lead to the other by branch- 
ing and flowing through as many separate cir- 
cuits as there are separate receptive devices, 
and the opening or closing of one of these cir- 
cuits does not affect the others. (See Circuits, 
Varieties of. ) 

Connection, Multiple-Series Such 

a connection of a number of separate electric 
sources, or separate electro-receptive de- 
vices, or circuits, that the sources or devices 
are connected in a number of separate groups 
in series, and each of these groups connected 
to main positive and negative conductors or 
leads in multiple arc. (See Circuits, Varie- 
ties of) 

Connection of Battery for Quantity. — 
(See Battery, Connection of , for Quantity) 

Connection of Electric Sources in Cas- 
cade. — (See Cascade, Connection of Electric 
Sources in) 

Connection of Toltaic Cells for Inten- 
sity. — (See Intensity, Connection of Voltaic 
Cells for) 

Connection, Series — The connec- 
tion of a number of separate electric 
sources, or electro-receptive devices, or cir- 



Con.] 



124 



[Con. 



cuits, so that the current passes successively 
from the first to the last in the circuit. (See 
Circuits, Varieties of) 

Connection, Series-Multiple —Such 

a connection of a number of separate electro- 
receptive devices, that the devices are placed 
in multiple groups or circuits, and these 
separate groups connected with one another 
in series. 

Connection, Telephonic Cross 

A device employed in systems of telephonic 
communication for the purpose of lessening 
the bad effects of induction, in which equal 
lengths of adjacent parallel wires are alter- 
nately crossed so as to alternately occupy the 
opposite sides of the circuit. 

Connector. — A device for readily con- 
necting or joining the ends of two or more 
wires. (See Post, Binding) 

Connector, Double 
A form of bind- 
ing screw suitable for 
readily connecting two 
wires together. 

A form of double con- 
nector is shown in Fig. 
170. 

Conning 1 Tower. — 
(See Tower, Conning.) 

Consequent Points.- 
quent) 

Consequent Poles. — (See 
quent) 

Conservation of Energy. 
Conservation of) 

Consonance, " In Consonance/' — A term 
employed to express the fact that one simple 
periodic quantity, z. e., a. wave or vibration, 
agrees in phase with another. 

Constant. — That which remains invariable. 

Constant-Current. — (See Current, Con- 
stant) 

Constant-Current Circuit. — (See Circuit, 
Constant Current) 

Constant-Current, Distribution of Elec- 
tricity by (See Electricity, Distri- 
bution of, by Constant Currents) 



Constant, Dielectric 



■A term some- 




170. Double 
Connector. 

(See Points, Conse? 



Poles, Conse- 



(See Energy; 



times employed in place of specific inductive 
capacity. (See Capacity, Specific Inductive) 

Constant, Galvanometer — The 

numerical factor connecting the current pass- 
ing through a galvanometer with the deflec- 
tion produced by such current. 

Sometimes a distinction is made between the 
galvanometer constant and the reduction factor, 
the former being used to indicate the relation 
between the current and the geometrical constant 
of the galvanometer, while the latter is used in 
the sense just defined of galvanometer constant. 

Constant Inductance. — (See Inductance, 
Constant) 

Constant Potential. — (See Potential, 
Constant) 

Constant-Potential Circuit. — (See Cir- 
cuit, Constant-Potential) 

Constant, Time, of Electro-Magnet 

— The time required for the magnetizing 

of its final value. 



current to rise 



to the -- 



Contact-Breaker, Automatic A 

device for causing an electric current to 
rapidly make and break its own circuit. 

The spring c, Fig. 171, carries an armature of 
soft iron, B, and is 
placed in a circuit in 
such a manner that 
the circuit is closed 
when platinum con- 
tacts placed on the 
ends of D and B, 
touch each other. In 
this case the arma- 
ture, B, is attracted to 
the core A, of the 
electro- magnet, thus 
breaking the circuit 
and causing the magnet to lose its magnetism. 
The elasticity of the spring C, causes it to fly back 
and again close the contacts, thus again energiz- 
ing the electro-magnet and again attracting B, 
and breaking the circuit. The makes and breaks 
usually follow each other so rapidly as to produce 
a musical note. (See Alarm, Electric.) . 

Contact, Dotting" An electric con- 




BATT&BY 

Fig. 171. Automatic 
Contact Breaker. 



Con.] 



125 



[Con, 



tact obtained by the approach of one con- 
tact point towards another. 

The term dotting contact is used in contradis- 
tinction to a rubbing contact. The rubbing 
contact i° generally to be preferred, since it tends 
automatically to remove dust and keep the con- 
tact surfaces polished and free from oxides. 

Contact Dynamo. — (See Dynamo, Con- 
tact) 

Contact Electricity. — (See Electricity, 
Contact) 

Contact, Fire- Alarm A contact so 

arranged that an alarm is given when any 
predetermined temperature is reached. 

Fire-alarm contacts are generally operated by 
the expansion of a metal or of a conducting fluid, 
such as mercury. (See Tker?nostat.) 

Contact Force. — (See Force, Contact) 

Contact, Full-Metallic A contact, 

which from its small resistance establishes a 
good or complete connection. (See Contact, 
Metallic) 

Contact, Intermittent The occa- 
sional contact of a telegraphic or other line 
with other wires or conductors by swing- 
ing, or by alternate contraction or expansion 
under changes of temperature. 

Contact, Metallic —A contact of 

a metallic conductor produced by its coming 
into firm connection with another metallic 
conductor. 

Contact, Partial A contact of a 

telegraphic, or other line, arising from defect- 
ive insulation, bad earths, or connection with 
an imperfect conductor. 

Contact, Rolling A contact con- 
nected with one part of an electric circuit, 
that completes the circuit by being rolled over 
a conductor connected with and forming 
another part of the circuit. 

Rolling contacts are employed on electric rail- 
roads. (See Railroad, Electric) 

Contact, Rubbing — A contact 

effected by means of a rubbing motion. 
Contact Series.— (See Series, Contact) 
Contact, Sliding A contact con- 
nected with one part of a circuit that closes 



or completes an electric circuit by being slid 
over a conductor connected with another 
part of the circuit. 

Sliding contacts are employed in electric rail- 
roads, in rheostats, switches, and a variety of other 
apparatus. (See Railroad, Electric. Rheostat. 
Key, Discharge.') 

Contact, Spring —A spring-sup- 
ported contact connected with one part of a 
circuit that completes said circuit by being 
moved so as to touch another contact con- 
nected with the other part of the circuit. 

The movement required to bring the two con- 
tacts together may be non-automatic, as in the case 
of a push-button, or automatic, as in the case of 
a thermostat. (See Button, Push. Thermostat) 

Contact Theory of Yoltaic Cell.— (See 
Cell, Voltaic, Contact Theory of ) 

Contact, Vibrating A spring con- 
tact, connected with one part of a circuit and 
so supported as to be able to vibrate towards 
and from another contact connected with 
another part of the circuit, thus automatically 
closing and opening said circuit. 

A vibrating contact is used in the automatic 
contact-breaker in which the movement of an 
armature towards an electro-magnet is caused to 
break the circuit of the coils of the electro-magnet, 
and, on its movement away from the magnet, to 
close another contact which again completes the 
circuit of the electro-magnet. (See Contact 
Breaker, Automatic.') 

Contact, Wiping —A contact ob- 
tained by a wiping movement of one con- 
ductor against another. 

The spark for electrically igniting a gas jet is 
obtained by means of a wiping contact of a spring 
moved by the motion of the pendanto (See 
Burner, Plain-Pendant Electric.) 

Contacts. — A variety of faults occasioned 
by the accidental contact of a circuit with any 
conducting body. 

The word contacts as employed above is in the 
sense of accidental contacts as distinguished from 
predetermined contacts. 

Contacts of an accidental character are of the 
following varieties, viz. : 

(I.) Pull, or metallic, as when the circuit is 



Con.] 



126 



[Con. 



accidentally placed in firm connection with an. 
other metallic circuit. 

(2.) Partial, as by imperfect conductors being 
placed across wires, or bad earths, or defective 
insulation. 

(3.) Intermittent, as by occasional contacts of 
swinging wires, etc. 

Contacts, Burglar • Alarm — Con- 
tacts fitted to windows, doors, tills, steps, 
floors, etc., so that a movement of the parts 
from their natural position gives an alarm by 
sounding a conveniently located bell. 

Contacts, Lamp Metallic plates or 

rings connected with the terminals of an incan- 
descent lamp for ready connection with the line. 

Contacts, Mercurial Electric con- 
tacts that are opened or closed by the ex- 
pansion or contraction of a mercury column. 

In the commonest forms of mercurial con- 
tacts, on the expansion of the mercury by heat it 
reaches a contact point placed in the tube, and 
thus completes the circuit through it own mass. 

Or, on contraction it breaks a contact, and thus 
disturbing an electric balance, sounds an alarm. 

Continental Code Telegraphic Alphabet. 

— (See Alphabet, Telegraphic, International 
Code?} 

Continuity of Current. — (See Current, 
Continuous?) 

Continuous Current. — (See Current, Con- 
tinuous?) 

Continuous Current, Distribution of 
Electricity by • — (See Electricity, Dis- 
tribution of, by Constant Currents) 

Continuous Current, Dynamo-Electric 
Machine ■ — (See Machine, Dynamo- 
Electric, Continuous Current?) 

Continuous-Sounding Electric Bell.— 
(See Bell, Continuous-Sounding Electric?) 

Continuous Wires or Conductors.— (See 
Wires or Conductors, Continuous?) 

Contraction, Anodic Closure —The 

muscular contraction observed on the closing 
of a voltaic circuit, the anode of which is placed 
over a nerve, and the kathode at some other 
part of the body. 

This term is generally written A. C. C. 



Contraction, Anodic Duration 

The length of time the muscle continues in 
contraction on the opening or closing of a 
circuit, the anode of which is placed over the 
part contracted. 

This term is generally written A. D. C. 

Contraction, Anodic Opening 

The muscular contraction observed on the 
opening of a voltaic circuit, the anode of which 
is placed over a nerve, and the kathode at 
some other part of the body. 

This term is generally written A. O. C. 

When the anode is placed over a nerve and a 
weak current is employed, if the circuit be kept 
closed for a few minutes, it will be noticed that, 
on opening the circuit the contraction will be 
much greater than if it had been opened after 
being closed for only a few seconds. The effect 
of the A. O. C. therefore depends not only on the 
current strength, but also on the time during 
which the current has passed through the nerve. 

Contraction of Lines of Magnetic Force. 

— (See Force, Magnetic, Contraction of 
Lines of.) 

Contractures. — In electro-therapeutics, 
prolonged muscular spasms, or tetanus, caused 
by the passage of electric currents. 

Contraplex Telegraphy. — (See Telegra- 
phy, Contraplex.) 

Controlled Clock.— (See Clock, Electric?) 

Controller. — A magnet, in the Thomson- 
Houston system of automatic regulation, 
whose coils are traversed by the main cur- 
rent, and by means of which the regulator 
magnet is automatically thrown into or out of 
the main circuit on changes in the strength 
of the current passing. (See Regulation^ 
Automatic?) 

Controlling Clock. — (See Clock, Electric?) 

Controlling Magnet. — (See Magnet, Con- 
trolling?) 

Convection Currents. — (See Currents,Con- 
vection?) 

Convection, Electric The air par- 
ticles, or air streams, which are thrown off 
from the pointed ends of a charged, insulated 
conductor. 



Con.] 



127 



[Cop. 



Convection streams, like currents flowing 
through conductors, act magnetically, and are 
themselves acted on by magnets. The same thing 
is true of the brush discharge, of the voltaic arc, 
and of convective discharges in vacuum tubes. 

Convection, Electrolytic A term 

proposed by Helmholtz to explain the appa- 
rent conduction of electricity by an electro- 
lyte, without consequent decomposition. 

Helmholtz assumes that the atoms of oxygen or 
hydrogen, adhering to the electrodes during elec- 
trolysis, are mechanically dislodged and diffused 
through the liquid, thus carrying off the elec- 
tricity by the charges received while in contact 
with the electrodes. 

Convection of Heat, Electric (See 

Heat, Electric Convection of.) 

Convection Streams. — (See Streams, C071- 
vection.) 

Convective Discharge. — (See Discharge, 
Convective.) 

Conversion, Efficiency of, of Dynamo 

— The total electric energy developed by a 
dynamo, divided by the total mechanical 
energy required to drive the dynamo. (See 
Co-efficient, Economic, of a Dynamo-Electric 
Machined) 

The efficiency of conversion 

W-j- w W-f- w 

= W~ ' W -j- w -f- m, 
where W, equals the useful or available electrical 
energy, M, the total mechanical energy, w, the 
electrical energy absorbed by the machine, and 
m, the stray power, or the power lost in friction, 
eddy currents, air friction, etc. 

Converted Currents. — (See Currents, 
Converted)} 

Converter. — The inverted induction coil 
employed in systems of distribution by means 
of alternating currents. 

A term sometimes used instead of trans- 
former. (See Transformer.) 

Converter, Closed-Iron Circuit 

A closed-iron circuit transformer. (See 
Transformer, Closed-Iron Circuit) 

Converter, Constant-Current — 

A constant-current transformer. (See Trans- 
former, Constant-Current.) 



Converter, Efficiency of The effi- 
ciency of a transformer. (See Transformer, 
Efficiency of) 

Converter Fuse. — (See Fuse, Converter) 

Converter, Hedgehog A form of 

transformer. (See Transformer, Hedge hog) 

Converter, Multiple A multiple 

transformer. (See Transformer, Multiple) 

Converter, Open-Iron-Circuit —An 

open-iron-circuit transformer. (See Trans- 
former, Open-Iron- Circuit) 

Converter, Series A series trans- 
former. (See Transformer, Series) 

Converter, Step-down A step-down 

transformer. (See Transformer, Step-down) 

Converter, Step-up —A step-up 

transformer. (See Transformer, Step-up) 



Converter, Welding 



■A welding- 



transformer. (See Transformer, Welding) 
Converting Currents. — (See Currents, 

Converting.) 
Cooling Box of Hydro-Electric Machine. 

— (See Box, Cooling, of Hydro-Electric 
Machine) 

Co-ordinates, Axes of The axes of 

abscissas and ordinates. 

The two straight lines, usually perpendicular 
to each other, to which distances representing 
values are referred for the graphic represen- 
tation of such values. (See Abscissas, Axes of) 

Copper Bath. — (See Bath, Copper) 

Copper Plating. — (See Plating, Copper) 

Copper Ribbon. — A variety of strap cop- 
per. (See Copper, Strap) 

Copper, Strap Copper conductors 

in the form of straps or flat bars. 

Strap copper is used on the armatures of some 
dynamos. Heavy copper conductors for such 
purposes are divided into strap copper so as to 
avoid eddy currents. The straps are placed 
alongside one another and insulated by a coating 
of varnish. 

Copper Wire, Hard-Drawn (See 

Wire, Copper, Hard-Drawn) 

Copper Wire, Soft-Drawn — (See 

Wire, Copper, Soft-Drawn) 



Cop.] 



128 



[Cor. 



Copper Voltameter. — (See Voltameter, 
Copper) 

Coppered Plumbago. — (See Plumbago, 
Coppered) 

Coppering, Electro Electro-plating 

with copper. (See Plating, Electro) 

Cord- Adjuster. — (See Adjuster, Cord) 

Cord, Conducting A small flexible 

cable, usually containing several conductors 
separated from one another by insulating ma- 
terial. 

Cord, Electric -A flexible, insulated 

electric conductor, generally containing at least 
two parallel wires. 

Electric cords are named from the purposes for 
which they are employed, battery cords, dental 
cords, lamp cords, motor cords, switch cords, etc. 




Fig. 172. Flexible Cord. 

A two-conductor flexible cord, in which each 
cord is composed of a number of bare copper wires 
placed parallel to and in contact with one another, 
is shown in Fig. 172. The several separate wires 
give flexibility to the cord. 

Cord, Pendant A flexible conductor 

provided for conveying the current to a hang- 
ing electric lamp supported by it. 

Cords, Telephone Flexible con- 
ductors for use in connection with a tele- 
phone. 




Fig. 173. Telephone Cords. 

Telephone cords, attached to an articulating 
telephone, are shown in Fig. 173. 



Core, Armature, Filamentous 

An armature core, the iron of which consists 
of wire. 

Core, Armature, H An armature 

core in the shape of the letter H, generally 
known as the shuttle armature, and some- 
times as the girder armature. 

This form is also called an I armature. 

The H armature core was the form originally 
given to the Siemens armature. In this form a 
single coil of wire was secured on the cross-bar 
of the H armature core, so as to fill up the entire 
space inside the letter, and the ends of the wire 
connected to a two-part commutator. 

Core, Armature, Lamination of 

The subdivision of the core of the armature 
of a dynamo-electric machine into separate 
insulated plates or strips for the purpose of 
avoiding eddy or Foucault currents. 

This lamination must always be perpendicular 
to the direction of the eddy currents that would 
otherwise be produced. (See Currents, Eddy) 

Core, Armature, of Dynamo-Electric 

Machine The iron core, on,, or around 

which, the armature coils of a dynamo-electric 
machine are wound or placed. 

The armature core is laminated for the pur- 
pose of avoiding the formation of eddy or Fou- 
cault currents. 

In drum, and in ring-armatures, the laminae 
should be m the form of thin insulated discs or 
plates of soft iron; in pole-armatures they should 
be in the form of bundles of insulated wires. 

The iron in the, cores should be of such an area 
of cross-section, as not to be readily oversaturated. 

Core, Armature, Radially-Laminated 

An armature core, the iron of which 

consists of thin iron washers. 

Core, Armature, Ribbed A cylin- 
drical armature core provided with longi- 
tudinal projections or ribs that serve as 
spaced channels or grooves for the reception 
of the armature coils. 

Core, Armature, Tangentially-Laininated^ 

An armature core, the iron of which. 

consists of a coiled ribbon. 

Core, Armature, Yentilation of 

Means for passing air through the armature 



Cor.J 



129 



[Cou. 



cores of dynamo-electric machines in order to 
prevent undue accumulation of heat. 

A properly proportioned dynamo-armature 
may need no ventilation, since in such the 
amount of heat generated is small as compared 
with the extent of the radiating surface. 

Since, however, in practice all armatures tend 
to heat at full load, especially in certain installa- 
tions in heated situations, ventilation of the ar- 
mature is desirable. 

Core, Closed-Magnetic A mag- 
netic core so shaped as to provide a complete 
iron path or circuit for the lines of magnetic 
force of its field. 



Core, Laminated 



-A core of iron 



which has been divided or laminated, in order 
to avoid the injurious production of Foucault 
or eddy currents. 



Core, Lamination of 



-Structural 



subdivisions of the cores of magnets, arma- 
tures, and pole-pieces of dynamo-electric 
machines, electric motors, or similar appa- 
ratus, in order to prevent heating and subse- 
quent loss of energy from the production of 
local, eddy or Foucault currents. 

These laminations are obtained b.y forming the 
cores of sheets, rods, plates, or wires of iron in- 
sulated from one another. 

The cores of dynamo-electric machine arma- 
tures should be subdivided in planes at right 
angles to the armature coils; or in planes parallel 
to the direction of the lines of force and to the 
motion of the armature; or, in general, in planes 
perpendicular to the currents that would otherwise 
be generated in them. 

Pole-pieces should be divided in planes per- 
pendicular to the direction of the currents in the 
armature wires. 

Magnet cores should be divided in planes at 
right angles to the magnetizing current. 

Core of Cable. — The conducting wires of 
an electric cable. (See Cable, Electric?) 

Core, Open-Magnetic Any mag- 
netic core so shaped that the lines of magnetic 
force of its field complete their circuit partly 
through iron and partly through air. 

Core Ratio of Cable.— (See Cable, Core 
Ratio of.) 



Core, Ring A hollow, cylindrical 

core of short length. 

Core, Ring, Elongated A hollow, 

cylindrical core of comparatively great length. 

Core, Solenoid A core so arranged 

as to be drawn into a solenoid on the passage 
of the current through its coils, and to be 
withdrawn therefrom, on the stopping of the 
current by the action of a spring or weight. 
(See Solenoid.) 

Core, Stranded, of Cable The 

conducting wire or core of a cable formed of 
a number of separate conductors or wires in- 
stead of a single conductor of the same weight 
per foot as the combined conductors. 

Core Transformer.— (See Transformer, 
Core. ) 
Cored Carbons. — (See Carbons, Cored) 

Cored Electrodes. — (See Electrodes, 
Cored) 

Coronae, Auroral A crown-shaped 

appearance, sometimes assumed by the auro- 
ral light. (See Aurora Borealis.) 

Corposant. — A name sometimes given by 
sailors to a St. Elmo's Fire. (See Fire, St. 
Elmo's) 

Correlation of Energy. — (See Energy, 
Correlation of) 

Corresponding Points. — (See Points, Cor- 
responding) 

Cosine. — One of the trigonometrical func- 
tions. (See Trigonometry) 

Cotangent. — One of the trigonometrical 
functions. (See Trigono7netry) 

Coulomb. — The unit of electrical quantity. 

A definite quantity or amount of the thing 
or effect called electricity. 

Such a quantity of electricity as would pass 
in one second in a circuit whose resistance is 
one ohm, under an electromotive force of 
one volt. 

The quantity of electricity contained in a 
condenser of one farad capacity, when sub- 
jected to an electromotive force of one volt. 

The quantity of electricity that flows per 
second past a cross-section of a conductor 



Cou. 



130 



[Cou. 



conveying an ampere. — (Ayrlon.) (See Am- 
pere. Farad. Volt.) 

Coulomb's Torsion Balance. — (See Bal- 
ance, CoutonVs Torsion) 

Coulomb-Volt.— A Joule, or .7373 foot- 
pound. 

The term? is generally written volt -coulomb. 
(See Volt -Coulomb.) 

Counter, Electric A device for 

counting and registering such quantities as 
the number of fares collected, gallons of water 
pumped, sheets of paper printed, revolutions 
of an engine per second, votes polled, etc. 

Various electric devices are employed for this 
purpose. They are generally electro-magnetic 
in character. 

Counter-Electromotive Force. — (See 
Force, Electromotive, Counter.} 

Counter Electromotive Force Lightning* 
Arrester. — (See Arrester, Lightning, Coun- 
ter-Electromotive Force.) 

Counter-Electromotive Force of Convec- 
tive Discharge. — (See Force, Electromotive, 
Counter, of Convective Discharge) 

Counter-Electromotive Force of Mutual 
Induction. — (See Force, Electromotive, 
Counter, of Mutual Induction.) 

Counter-Electromotive Force of Self-In- 
duction. — (See Force, Electromotive, Coun- 
ter, of Self -Induction) 

Counter-Electromotive Force of Self-in- 
duction of the Primary. — (See Force, 
Electrojnotive, Counter, of Self-induction of 
the Primary) 

Counter-Electromotive Force of Self-In- 
duction of the Secondary. — (See Force, 
Electromotive, Counter, of Self-induction of 
the Secondary) 

Counter-Electromotive Force of the 
Primary. — (See Force, Electromotive t 
Counter, of the Pri?nary) 

Counter Inductive Effect.— (See Effect, 
Counter Inductive) 

Couple. — In mechanics, two equal parallel 
forces acting in opposite directions but not in 
the same line, and tending to cause rotation. 

The moment, or effective power of a couple, is 



equal to the intensity of one of the forces multiplied 
by the perpendicular distance between the direc- 
tions of the two forces. 

Couple, Astatic — Two magnets of 

exactly equal strength so placed one over the 
other in the same vertical plane as to com- 
pletely neutralize each other. 

An astatic couple has no directive tendency. A 
pair of magnets combined as an astatic couple is 
called an astatic needle. (See Needle, Astatic.) 

Couple, Magnetic The couple which 

tends to turn a magnetic needle, placed in the 
earth's field, into the plane of the magnetic 
meridian. 

If a magnetic needle is in any other position 
than in the magnetic meridian, there will be two 
parallel and equal forces acting at A and B, Fig. 
174, in the directions shown by the arrows. 
Their effect will be to ro- 
tate the needle until it 
comes to rest in the mag- 
netic meridian N S. 

The total force acting 
on either pole of a needle 
free to move in any direc- 
tion, is equal to the 
strength of that pole mul- 
tiplied by the total inten- 
sity of the earth's field at 
that place ; or, if free to move in a horizontal 
direction only, is equal to the intensity of the 
earth's horizontal component of magnetism at 
that place, multiplied by the strength of that pole. 

The effective power or moment of a magnetic 
couple is equal to the force exerted on one of the 
poles multiplied by the perpendicular distance, 
P Q, between their directions. 

Couple, Moment of — The effective 

power or force of a couple. 

The moment of a couple is equal to the inten- 
sity of one of the forces multiplied by the perpen- 
dicular distance between the direction of the 
forces. 

Couple, Thermo-Electric Two dis- 
similar metals which, when connected at their 
ends only, so as to form a completed electric 
circuit, will produce a difference of potential, 
and hence an electric current, when one of the 
ends is heated more than the other. 

Thus if a bar of bismuth be soldered to a bar 




174. Magnetic 
Couple. 



Cou.] 



131 



[Cre. 



of antimony the combination will form a thermo- 
electric couple, and the circuit so formed will 
have a current passing through it when one junc- 
tion is hotter or colder than the other. 

There is, according to Lodge, a true contact 
force, at a thermo-electric junction, as is shown by 
the reversible heat effects produced when an 
electric current is passed across such junction; for, 
in one direction more heat is produced, and in the 
opposite direction less heat. This, as is well 
known, differs from the irreversible heat produced 
by a current through a homogeneous metallic 
conductor. The reversible heat effects, or as they 
are called the Peltier effects, may overpower and 
conceal the heating effects. But, in addition to 
these effects, since a difference of potential, called 
a Thomson effect, exists in a substance unequally 
heated, currents are so produced, and these are 
also influential in causing the difference of poten- 
tial of a thermo-electric couple* 

" There are then," says Lodge, "in a simple 
circuit of two metals with their junctions at differ- 
ent temperatures, altogether four E. M. Fs., one 
in each metal, from hot to cold, or vice versa, and 
one at each junction, and the current which flows 
around such a circuit is propelled by the resultant 
of these four." * * * "These four forces, 
two Thomson forces in the metals, and two Peltier 
forces at their junctions, may some of them help 
and some hinder the current. " * * * "When- 
ever they help, the locality is to that extent cooled; 
whenever they hinder, it is to that extent 
warmed." 

The action of a thermo-electric couple in pro- 
ducing a difference of potential is therefore a 
complicated one, and depends on Peltier and 
Thomson effects, as well as on the thermo-electric 
effect. (See Effect, Peltier. Effect, Thomson. 
Effect, Thermo -Electric.) 

Couple, Toltaic — Two materials, 

usually two dissimilar metals, capable of 
acting as an electric source when dipped in 
an electrolyte, or capable of producing a 
difference of electric potential by mere con- 
tact. 

Liquids and gases are capable of acting as 
voltaic couples. 

All voltaic cells have two metals, or a metal and 
a metalloid, or two gaseous or liquid substances 
which are of such a character that, when dipped 
into the exciting fluid one only is chemically 
acted on. 



Each one of these two substances is called an 
element of the cell, and the two taken collectively 
form a voltaic couple. 

The elements of a voltaic couple may consist of 
two gases or two liquids. (See Battery, Gas.) 

Coupled Cells.— (See Cells, Coupled) 

Coupler, Voltaic Any device by 

means of which voltaic cells may be readily 
coupled or connected in different forms of 
circuits. (See Circuits, Varieties of) 

Coupling of Toltaic Cells or Other 
Electric Sources. — A term indicating the 
manner in which a number of separate 
electric sources may be connected so as to 
form a single source. (See Circuits, Varie- 
ties of) 

Cramp, Telegrapher's An affec- 
tion of the hand of a telegrapher due to im- 
moderate and excessive use of the same 
muscles, somewhat similar to the disease 
known as writer's cramp. 

Telegrapher's cramp, like writer's cramp, may 
be defined as a professional neurosis of co-ordina- 
tion. It appears not only in certain groups of 
muscles, but is limited to such groups, only when 
they are performing certain complicated opera- 
tions. For example, telegrapher's cramp is 
practically a paralysis of certain muscles of the 
hand and wrist of the operator. These muscles, 
when called on to perform the somewhat delicate 
movements required in sending a telegraphic dis- 
patch, are incapable of performing their proper 
functions, but when called on to perform in part 
other similar actions, provided all these actions 
are not required to be used, appear to be un- 
affected. 

The ability of the operator to send with either 
hand would lessen the liability to this disease. 

Crater in Positive Carbon. — A depression 
at the end of the positive carbon of an arc 
lamp which appears when a voltaic arc is 
formed. (See Arc, Voltaic) 

Creep, Diffusion The flow of an 

electric current in portions of a conducting 
substance, outside the parts that lie in the 
direct lines between the points where the 
terminals of the same are applied to the con- 
ducting substance. 



CreJ 



132 



[Cro. 



Creeping, Electric ■ A term some- 
times applied to the creeping of a current. 
(See Current, Creeping of.) 

Creeping 1 in Yoltaic Cell. — (See Cell, Vol- 
taic, Creeping in) 

Creeping" of Current. — (See Current, 
Creeping of, Electric?) 

Creeping, Saline —The formation 

of salts by efflorescence on the walls of a solid 
immersed in a solution of a salt. 

Creosoting. — A process employed for the 
preservation of wood, as, for example, tele- 
graph poles, by injecting creosote into the 
pores of the wood. (See Pole, Telegraphic.) 

Crith. — A term proposed by A. W. Hoff- 
man, as a unit of weight, or the weight of 
one litre, or cubic decimetre, of hydrogen at 
O u C. and 760 mm. barometric pressure. 

Critical Current. — (See Current, Crit- 
ical.) 

Critical Current of a Dynamo. — (See 
Current, Critical, of a Dynamo.) 

Critical Distance of Lateral Discharge 
through Alternative Path. — (See Distance, 
Critical, of Lateral Discharge through 
an Alternative Path) 

Critical Speed of Compound-Wound Dy- 
namo. — (See Speed, Critical, of Compound- 
Wound Dyiianio) 

Crookes' Dark Space. — (See Space, Dark, 
Crookes') 

Crookes' Electric Radiometer. — (See Ra- 
diometer, Electric, Crookes '.) 

Cross Arm. — (See Arm, Cross.) 

Cross-Connecting Board. — (See Board, 
Cross-Connecting.) 

Cross, Electric A connection, gen- 
erally metallic, accidentally established be- 
tween two conducting lines. 

A defect in a telegraph, telephone or other 
circuit caused by two wires coming into 
contact by crossing each other. 

A swinging or intermittent cross is caused by 
wires, which are too slack, being occasionaly 
blown into contact by the wind. 



A weather cross arises from defective action ot 
the insulators in wet weather. 

Cross, Swinging or Intermittent 



An accidental contact, generally metallic, 
caused by wires being brought into occasional 
contact with one another, or with some other 
conductor, by the intermittent action of the 
wind. 

Cross, Weather A contact or leak 

occurring in a telegraphic or other line dur- 
ing wet weather, from the defective action of 
the insulators. 

Crossing Cleat— (See Cleat, Crossing) 

Crossing, Live-Trolley A device 

whereby a trolley moving over a line that 
crosses a second line at an angle is enabled 
to maintain its electrical connection with the 
line while crossing. 

A live-trolley crossing is necessitated where one 
line of electric railway crosses another. The 
upper line must, of course, provide a space or 
opening for crossing the lower line at the points 
of intersection. This is effected in the Bagnall 
hve-trolley crossing, shown in Fig. 175, by attach- 



Fig.iys. Live-Trolley Crossing. 

ing to the upper trolley wire a bridge piece of 
light lathe casting, provided at its centre with a 
gap through which the trolley wire passes. This 
bridge piece is insulated from the trolley wire by 
means of a disc of insulating material at the cen- 
tre of the bridge, which is provided with a hinged 
curved lever, that in its normal position rests un- 
der the influence of gravity in the position shown 
in the figure. The passage of the trolley wheel 
along the wire carries the line under it and thus 
bridges the gap, as shown by the position of the 
dotted lines. 

Crossing Wires. — (See Wires, Crossing.) 

Cross-Over Block.— (See Block, Cross- 
Over.) 

Cross-Over, Trolley A device by 

means of which a trolley is enabled to pass 
over the points where different lines cross one 
another without serious interruption. 



Cro.] 133 

A trolley cross-over, for trolley lines, is shown 
in Fig. 176. 



[Cur. 




Fig. 176. Trolley Cross Over. 

Crow-foot Zinc. — (See Zinc, Crow-foot?) 

Crucible, Electric A crucible in 

which the heat of the voltaic arc, or of elec- 
tric incandescence, is employed either to per- 
form difficult fusions, or for the purpose of 
effecting the reduction of metals from their 
ores or the formation of alloys. (See Fur- 
nace, Electric?) 

Crystal.— A solid body bounded by sym- 
metrically disposed plane surfaces. 

A definite form or shape is as characteristic of 
an inorganic crystalline substance as it is of an 
animal or plant. Each substance has a form in 
which it generally occurs. There are, however, 
certain modifications of the typical forms which 
cause plane surfaces to appear curved, and the 
Symmetrical arrangement of the face*; to disap 
pear. These modifications often render it ex 
tremely difficult to recognize the true typical 
form. 

For the different fundamental crystalline forms, 
or systems of crystals, see any standard work on 
chemistry. 

Crystal, Hemihedial — A crystal 

whose shape or form has been modified by 
the replacement of half its edges or solid 
angles, 

A hemihedral crystal possesses different forms 
at the ends or extrtmities of its axes. Hemi- 
hedral crystals, when unequally heated, develop 
electrical charges. 

Electricity produced in this way was formerly 
called pyro-electricity. (See Electricity, Pyro.) 

Crystal, Holohedral — A crystal 

whose shape or form has been modified by 
the replacement of all its edges or solid 
angles. 

Crystalline Electro-Metallurgical De- 
posit. — (See Deposit, Crystalline, Electro- 
Met a llurgical.) 

Crystallization. — Solidification from a state 
of solution or fusion in a definite crystalline 
form. 



The crystallization of a dissolved solid is fa- 
vored by any cause that gives increased freedom 
of movement to its molecules, such for example as 
solution, fusion, sublimation, or precipitation, 

Crystallization by Electrolytical Decom- 
position. — The crystalline deposition of vari- 
ous metals by the passage of an electric cur- 
rent through solutions of their salts under 
certain conditions. 

A strip of zinc immersed in a solution of sugar 
of lead (acetate of lead) soon becomes covered 
with bright metallic plates of lead, that are elec- 
trolytically deposited by the weak currents due to 
minute voltaic couples formed with the zinc by 
particles of iron, carbon, or other impurities in 
the zinc. The deposit assumes at times a tree- 
like growth, and is therefore called a lead tree. 
(See Couple, Voltaic.) 

Crystallization, Electro Crystalli- 
zation effected during electrolytic deposition. 

Crystallize. — To separate from a liquid 
or vapor, in the form of a crystalline solid. 

Crystalloid. — Those portions of a mixed 
substance subjected to dialysis, that are capa- 
ble of crystallization. (See Dialysis?) 

Cube, Faraday's —An insulated 

room cubic in shape, covered on the inside 
with tin foil, which, when charged on the 
outside gives no indications to an observer on 
the inside, though furnished with delicate in- 
struments, 

Faraday's cube illustrates the fact that an elec- 
trostatic charge resides on the outside of an insu- 
lated conductor. (See Net, Faraday" s.) 

Cup, Mercury A cup or cavity 

filled with mercury and connected with the 
pole of an electric apparatus for the ready 
placing of the same in circuit with other elec- 
tric apparatus. 

To connect apparatus it is only necessary to 
insert the free terminal of one apparatus in the 
mercury cup of the other. 

Cup, Porous A porous cell. (See 

Cell, Porous?) 

Curb, Double A device for in- 
creasing the speed of signaling, by means of 
which the line is rid of its charge before the 
next signal is sent, by sending an opposite 
charge, then another in the same direction, 



Cur.] 



134 



|Cur. 



then finally another in the same direction 
before connecting with the ground. 

The effect of the third charge is to reduce the 
potential of the line more nearly to zero at the 
end of the signal. 

Curb, Single — — — A device for in- 
creasing the speed of signaling telegraphic- 
ally by ridding the line of its previous charge 
by sending a reversed current through it be- 
fore connecting with the ground. 

In single-curb signaling the operator in dis- 
charging the line before sending another signal 
through it, before putting the line to earth, re- 
verses the battery, and then connects to earth. 

Current, Absolute Unit of A cur- 
rent of 10 amperes. (See A7npere. Units, 
Practical?) 

A current of such a strength that when 
passed through a circuit of a centimetre in 
length bent in the form of an arc of a circle 
one centimetre in radius, will act with the 
force of a dyne on a magnetic pole of unit 
strength, placed at the centre of the arc. 

The ampere, the practical unit of current, is 
but -j-L the value of the absolute unit of current. 

Current, Action of, on a Magnetic Pole 
An attraction or repulsion depend- 
ent on the name of the pole and the direction 
of the current. 

Two currents of electricity attract or repel each 
other according to the direction in which they 
are flowing, and the mutual positions of their 
circuits. A current and a magnetic pole exert an 
action on each other which, strictly speaking, is 
neither attraction nor repulsion, but which is ro- 
tation, that may, however, be regarded as being 
produced by the combined action of attraction 
and repulsion. 

Current, Alternating A current 

which flows alternately in opposite directions. 

A current whose direction is rapidly re- 
versed. 

The non-commuted currents generated by the 
differences of potential in the armature of a 
dynamo-electric machine are alternating or 
simple-periodic-currents. 

In a characteristic curve of the electromotive 
forces of alternating currents, positive electro- 
motive forces, or those that would produce cur- 



rents in a certain direction, are indicated by 
values above a horizontal line, and negative elec 
tromotive forces, by values below the line. 

The curves A B C, and C D E, Fig. 177, are 

B 




Fig, 177- 



Curve of Electromotive Forces of Alternating 
Currents. 



often called phases, and represent the alternate 
phases of the current. 

Current, Alternative —A voltaic 

alternative. (See Alternatives, Voltaic.) 
Current, Assumed Direction of Flow 

of The direction the current is as- 
sumed to take, z. e., from the positive pole of 
the source through the circuit to the negative 
pole of the source. 

The electricity is assumed to come out of the 
source at its positive pole, and to return or flow 
back into the source at its negative pole. This 
convention as to the direction of the electric cur- 
rent is in accordance with the assumption of the 
direction of flow of lines of magnetic forces. 

The old idea of a dual or double current flowing 
in opposite directions is still maintained by some. 
(See Force, Lines of, Direction of.) 

Current, Axial In electro-thera- 
peutics a current flowing in a nerve in the 
opposite direction to the normal impulse in 
the nerve. 

Current. Break-Induced The cur- 
rent induced by a current in its own, or in 
another circuit, on breaking or opening the 
same. 

The current induced in the secondary on 
the breaking of the primary circuit. 

The break -induced current set up by a current 
in its own circuit is sometimes called the direct- 
induced current. 

Lord Rayleigh has shown that within certain 
limits the break-induced current has a greater 
effect in magnetizing steel needles, the smaller 
the number of turns of wire in the secondary. In 



Cur.l 



.00 



[Cur, 



the case of a galvanometer, it is well known that 
the opposite is true. The deflection of the gal- 
vanometer needle depends on the strength of the 
whole current. The magnetizing power depends, 
for the greater part, on the strength of the cur- 
rent at the beginning of its formation- 

Current. Closed-Circular —A cur- 
rent flowing in a circular circuit. 

A small closed -circular current may be replaced 
magnetically by a thin disc of steel, magnetized in 
a direction perpendicular to its face, and the edge 
of which corresponds to the edge of the circular 
conductor. 

Current-Commuter. — (See Commuter, 
Current?) 

Current. Conduction The current 

that passes through a metallic or other con- 
ducting substance, as contradistinguished 
from a current produced in a non-conductor 
or dielectric. (See Current, Displacement^ 

Current, Constant A current that 

continues to flow in the same direction for 
some time without varying in strength, 

This term is sometimes used to mean a con 
tiruious or direct current in contradistinction to 
an alternating current, but it ought to be applied 
only to unvarying currents. such : for example as 
a constant current of 10 amperes. 

Current, Continuous — An electric 

current which flows in one and the same 
direction 

Although the term continuous current is used 
as synonymous with constant current, it is not 
entirely so; a continuous current flows constantly 
in the same direction A constant current not 
only flows continuously in the same direction, but 
maintains an approximately constant current 
strength 

This term continuous current is used in the 
opposite sense to alternating current, and in the 
same sense as a direct current. 

Current, Creeping" of Electric 

A change in the direction of path of a current 
from the direct line between the points of 
connection with the source. 

When the terminals of any electric source are 
placed in contact with any two points of a metallic 
sheet of conducting material, the flow of the cur- 
rent is not confined to the direct line between the 




Fig 17 S. Critical 
Curve of Dynamo 
Current 



points of contact, but creeps or diffuses into por- 
tions of the conducting plate surrounding this 
direct line. (See Current , Diffusion of. ) 

In a somewhat similar manner, the current 
is said to creep, or to establish a partial short- 
circuit around the poles of a poorly insulated 
voltaic battery, or other electric source. 

Current, Critical 

— The current at which a 
certain result is reached. 

Current, Critical, of a 

Dynamo That value 

of the current at which the 
characteristic curve begins 
to depart from a nearly 
straight line. — {Szhanus 
P. Thompson?) 

In Fig. 178 the critical 
current is shown in three different cases, as oc- 
curring where the dotted vertical line cuts the 
characteristic curves. 

The speed at which sl series dynamo excites 
itself is often called the critical speed. 

Current, Demarcation —A term 

sometimes applied to an electric current ob- 
tained from an injured muscle. 

" Every injury of a muscle or nerve causes at 
the point of injury a dying surface, which behaves 
negatively to the positive intact substance." — 
(Landois 6° Stirling.) 

Current Density.— The current of elec- 
tricity which passes in any part of a circuit as 
compared with the area of cross-section of 
that part of the circuit. 

In a dynamo- electric machine the current den- 
sity in the armature wire should not, according to 
Silvanus P. Thompson, exceed 2. 500 amperes 
per square inch of area of transverse section of 
conductor. 

The current density in a dynamo wire, of 
necessity depends on the sectional area of the 
coils. If, for example, a current of 50 amperes 
be safe in an armature section of eight turns it 
may be safely increased to 100 amperes if the 
conductors are cross- sectioned so as to make but 
four turns. — (Urquhart.) 

In electro-plating, for every definite current 
strength that passes through the bath> or in other 
words, for a definite number of coulombs, a 
definite weight of metal is deposited, the charac- 



Cur.] 136 [Cur. 

ter of which depends on the current density. The stant in direction, as distinguished from an 

character of an electrolytic deposit will therefore alternating current 

depend on the current density at that part of the A conti n UOU s current, 
circuit where the deposit occurs. 

The following table from Urquhart gives the Current, Direct-Induced The cur- 
practical working value for the current density rent induced in a circuit by induction on it- 
for electro-metallurgical deposits : self, or self-induction, on breaking or opening 

• the circuit. (See Currents, Extra.) 

Current Density (or Amperes on This is called the direct-induced current because 

thode). . its direction is in the same direction as the induc- 
Amperes 

Solution of per square loot. ing current. 

Copper, acid bath 5.0 to 10.0 Current, Direction of The direc- 

Copper cyanide bath 3.0 « 5.0 tion an electric current is assumed to take 

Silver, double cyanide 2.0 " 15.0 Lt . f x1 , ., 

„.,'..,/ . . J out from one pole of any source through the 

Gold, chloride in cyanide 1.0 " 2.0 . . ,. r .... , , , 

Nickel, double sulphate 6.0 « 8.0 circuit and lts translating devices back to the 

Brass, cyanide 2.0" 3.0 source through its other pole. 

Tin ... Conventionally, the current is assumed to come 

-. . ._. ... , out from the positive pole of the source and to go 

Current, Diacritical —Such a. , , . ,, .;, .. , 

7 _ back to the source at the negative pole, 

strength of the magnetizing current as pro- _ . _^. _ . „,, 

, ,. .. t , Current, Displacement The rate 

duces a magnetization 01 an iron core equal , , 

t_ ir of change of electric displacement. 

to half-saturation. „ , . , , . , 

A brief conduction current produced m a 

The diacritical current is the current which, j. , . . , , ,. , . /c 

_ . ■ ,.,",. , , r . dielectric by an electric displacement. (See 

flowing through the diacritical number of ampere- _ . , , _ r . . 

... , ,1 j , j. Displacement, Electric :) 

turns, will bring up the magnetism produced to ■ * J 

half- saturation. This is called a displacement current in order 

The diacritical number of ampere-turns is such to distinguish it from a conduction current in any 

a number of ampere-turns as would reduce the conductor. 

magnetic permeability to half its full value. The displacement current continues while the 

displacement of electricity is going on. Dis- 

Current, Diffusion of A term em- placeme nt currents have all the properties of con- 

ployed to designate the difference in the auction currents, and, like the latter, produce a 

density of current in different portions of a magnetic field; in fact, they resemble extremely 

conductor. (See Current. Creefimg of, Elec- brief conduction currents. 

trie.) The difference between conducting substances 

n j. tw^p . x. t.-i j. m , and dielectrics, lies in the fact that the conducting 

Current. Diffusion of Electro-Tlierapeu- . , , , . L . . & 

r substances do not possess an elastic force, en- 

tlc " The difference in the density of abUng them to resist e]ectric dlsplacement In 

current in different portions of the human other wordS} conduct i n g substances possess no 

body between the electro-therapeutic elec- electric elasticity, and can have no true displace- 

trodes. ment current established in them. (See Elasti- 

When the electrodes are placed at any two city, Electric.) 
given points of the human body, the current A displacement current, like a conduction cur- 
branches through various paths, extending in a rent, possesses a magnetic field, or is encircled by 
general direction from one electrode to the other, lines of magnetic force. (See Field, Magnetic, of 
according to the law of branched or derived cir- on Electric Current.) 

cuits, and flowing in greater amount, or with Current, Electric The quantity of 

greater density of current, through the relatively electricity which passes per second through 

better conducting paths. (See Current Density.) any con d uc tor or circuit. 

This is sometimes called the creeping of the The fate ^ which a definite quantity of dec _ 

current. (See Current, Creeping of.) ^.^ ^^ Qr flowg ^^ a conductQr Qr 

Current, Direct — A current con- circuit. 



Cur.] 



137 



[Cur. 



The ratio existing between the electro- 
motive force, causing the current, and the 
resistance which may, for convenience, be 
regarded as opposing it, expressed in terms 
of quantity of electricity per second. 

The unit of current, or the ampere, is equal to 
one coulomb per second. (See A7?ipere. Coulomb. ) 

The word current must not be confounded 
with the mere act of flowing; electric current 
signifies rate of flow, and always supposes an 
electromotive force to produce the current, and a 
resistance to oppose it. 

The electric current is assumed to flow out 
from the positive terminal of a source, through 
the circuit and back into the source at the nega- 
tive terminal. It is assumed to flow into the 
positive terminal of an electro-receptive device 
such as a lamp, motor, or storage battery, and 
out of its negative terminal; or, in other words, 
the positive pole of the source is always con- 
nected to the positive terminal of the electro-re- 
ceptive device. 

Professor Lodge draws the following com- 
parison between the motions of ordinary mat- 
ter, heat and electricity: ''Consider the modes 
in which water may be made to move from place 
to place; there are only two. It may be pumped 
along pipes, or it may be carried about in jugs. 
In other words, it may travel through matter, or, 
it may travel with matter. Just so it is with heat, 
also. Heat can travel in two ways: it can flow 
through matter, by what is called ' conduction, ' 
or, it can travel with matter, by what is called 
'convection.' There is no other mode of con- 
veyance of heat." * * * "For electricity 
the same is true. Electricity can travel with 
matter, or it can travel through matter, by con- 
vection, or by conduction, and by no other way." 

In the above, the radiation of heat is apparently 
lost sight of. 

In the opinion of some, an electric current con- 
sists of two distinct currents, one of positive and 
the other of negative electricity, flowing in oppo- 
site directions. Each of these currents is supposed 
to be equal in amount to the other. 

The electric current is now regarded as passing 
through the dielectric surrounding the conductor, 
rather than through the conductor itself. (See 
Current, Electric, Method of Propagation of, 
Through a Circuit.') 

The current that flows or passes in any circuit 
is, m the case of a constant current, equal to the 



electromotive force, or difference of potential, 
divided by the resistance, as — 

K 

(See Law of Ohm.) 

Current, Electric, Method of Propagation 

of, Through a Circuit When an 

electric current is propagated through a wire 
or other conductor, it is not sent or pushed 
through the conductor, like a fluid through 
a pipe or other conductor, but is, so to speak, 
rained down on the surface of the conductor 
from the medium or dielectric surrounding it. 

Poynting, who has carefully studied this mat- 
ter, remarks as follows, viz.: "A space contain- 
ing electrical currents may be regarded as the 
field where energy is transformed at certain points 
into the electric or magnetic kind, by means of 
batteries, dynamos, thermopiles, etc., and in 
other parts of th* field this energy is being again 
transformed into heat, work done by the electro- 
magnetic forces, or any other form yielded by 
currents. 

"Formerly the current was regarded as some- 
thing traveling in the conductor, and the energy 
which appeared at any part of the circuit was 
supposed to be conveyed thither through the 
conductor by the current. Bat the existence of in- 
duced currents and electro-magnetic actions have 
led us to look on the medium surrounding the 
conductor as playing a very important part in the 
development of the phenomena. If we believe in 
the continuity of the motion of energy, we are 
forced to conclude that the surrounding medium 
is capable of containing energy, and that it is 
capable of being transferred from point to point. 
We are thus led to consider the problem, how 
does the energy about an electric current pass 
from point to point; by what paths does it travel, 
and according to what laws ? Let us take a spe- 
cific case. Suppose a dynamo at one spot gen- 
erates an electric current, which is made to operate 
an electric motor at a distant place. We have 
here, in the first place, an absorption of energy 
from the prime motor into the dynamo. We find 
the whole space between and around the conduct- 
ing wires magnetized and the seat of electro- 
magnetic energy. We have further a retrans- 
formation of energy in the motor. The question 
which presents itself for solution is to decide how 
the energy taken up by the dynamo is trans- 
mitted to the motor, by what path it travels 



Cur.] 



138 



[Cuiv 



and according to what laws ? Briefly stated, the 
tendency of recent views is that this energy is 
conveyed through the electro-magnetic medium 
or ether, and that the function of the wire is to 
localize the direction or to concentrate the flow in 
a particular path, and thus provide a sink or place 
in which the energy can be dissipated. * * * •" 

Taking again, for instance, the case of the dis- 
charge of a condenser by a conductor. He says: 
"Before the discharge we know that the energy 
resides in the dielectric, between the conducting 
plates. If these plates are connected by a wire, 
according to these views, the energy is transferred 
outwards along the electrostatic, equipotential sur- 
faces, and moves on to the wire and is there con- 
verted into heat. According to this view we 
must suppose the lines of electrostatic induction, 
running from plate to plate, to move outwards, as 
the dielectric strain lessens, and while still keep- 
ing their ends on the plates, to finally converge 
in on the wire and be there broken up and their 
energy dissipated as heat." 

In other words, some of the energy of the ex- 
panding lines of induction is changed into mag- 
netic energy; this energy is contained in ring- 
shaped tubes of force, which expand outwards 
from between the plates and then contract on 
some other part of the conductor. 

The time of the discharge, then, consists of the 
following steps, viz. : 

(I.) The time during which the energy of the 
charge is nearly all electrostatic and is repre- 
sented by the energy contained in the lines or 
tubes of electrostatic induction, running from 
plate to plate of the condenser. 

(2.) The time during which the discharge is at 
its maximum and the energy consists of two parts, 
viz.: energy associated with the outward ex- 
panding lines of electrostatic induction, and energy 
associated with the closed lines or tubes of mag- 
netic force, which at first are expanding and after- 
wards contracting. 

(3.) The time when the energy has been ab- 
sorbed, or the period in which the energy in the 
wire or the conductor has either been dissipated 
in the form of non- luminous radiation or obscure 
heat. 

(4.) The time during which this non-luminous 
heat gives up its energy again to the surrounding 
medium in the shape of heat waves. 

Current, Electro-Therapeutic Polarizing* 

The current which produces the 



phenomena of electrotonus. (See Electro- 
tonus.) 

Current, Element of — A term 

employed in mathematical discussions to in- 
dicate a very small part of a current for ease 
in considering its action on a magnetic needle 
or other similar body. 

Current, Faradic — In electro- 
therapeutics, the current produced by an in- 
duction coil, or by a magneto-electric machine. 

A rapidly alternating current, as distin- 
guished from a uniform voltaic current. 

A voltaic current that is rapidly alternated by 
means of any suitable key or switch is sometimes 
called a voltaic alternative. The discharge from 
a Holtz machine is sometimes called a Franklinic 
Current. (See Alternatives, Voltaic. Current y 
Franklinic.') 

Current - Filaments. — (See Filament, 
Current?) 

Current, Franklinic — A term some- 
times used in electro-therapeutics for a cur- 
rent produced by the action of a frictional 
electric machine. 

The term, Franklinic current, is used in con- 
tradistinction to Faradic current, or that produced 
by induction coils, or, in contradistinction to a 
galvanic or voltaic current, or that produced by 
a voltaic battery. 

Current, Generation of, by Dynamo-Elec- 
tric Machine — The difference of 

potential developed in the armature coils 
by the cutting of the lines of magnetic 
force of the field by the coils, during the rota- 
tion of the armature. 

If a loop of wire whose ends are connected to 
the two-part commutator, shown in Fig. 179, be 

A 




Fig. 17 q. Induction in Armature Loop. 

rotated in the magnetic field between the magnet 
poles N and S, in the direction of the large arrow, 
differences of potential will be generated which 




Cur.] 139 [Cur. 

will cause currents to flow in the direction indi- tation as being near, or at right angles to the di- 

cated by the small arrows during its motion past ameter of greatest average magnetic density. 

the north pole from the top to the bottom, but in the (See Lead, Angle of. Lag, Angle of. ) 
opposite direction during its motion past the south Current-Governor.— (See Governor, Cur- 

pole — from the bottom to the top. If, now, col- rm f \ 

lecting brushes rest on the commutator in the Current , Homogeneous Distribution of 
positions shown in the Fig. 180. the vertical line ~ , ,. . „• „. c t . , 

r & Such a distribution of a current through 

180° 

:J5-I;Td"^H| an y concm ctor in which there is an equal 

1^H~j2!*_v3H density of current at all portions of any 

5^-~-<^lk--^~-~-;H cross-section of the conductor. 

; 90r----l€>l----270W 

When the flow of a constant current is estab- 

— *jiL^B lished in a solid conducting wire, there is a 

fc. ir_3L~_~ ZJtM homogeneous distribution of current in that con- 

Fig. 180. Action of Commutator. ductor. 

of the gap between the poles corresponding with Current, Induced The current 

the vertical gap between the commutator seg- produced in a conductor by cutting lines of 

ments, the currents generated in the loop will be force. 

caused to flow in one and the same direction, and The induced current results from differences of 

B', will become the positive brush, since the end potential produced by electro-dynamic induction. 

of the loop is connected with it only so long as it (See Induction, Electro- Dynamic.) 

is positive. As soon as it becomes negative, from Current - Induction. — (See Induction, 

the current in the loop flowing in the opposite Current r .) 

direction, the other end, which is then positive, _, . _ . 

, , . , ,, ... , , Current, Intensity of ■ — An old 

is connected with the positive brush. ' J 

A similar series of changes occur at the nega- term sometimes employed to indicate the 

tive brush B. current which resulted from a considerable 

Theoretically, the neutral points, where the difference of potential, or a great electromotive 

brushes rest, would be in the vertical line coincid- force. 

ing with that of the gap between the poles. An This term was also formerly used as synony- 

inspection of the figure shows that the neutral mous with strength of current. 
line, or the diameter of commutation, is dis- This use of the term is now abandoned, 

placed in the direction of rotation. (See Com mu- Voltaic batteries, connected in series so as to 

tation, Diameter of.) The displacement of the glve a considerable difference of potential, were 

brushes, so necessitated, is caMed the Lad. spoken of as being connected for intensity. 

The cause of the lead is the reaction that occurs This term has also been used for the quantity 

between the magnetic poles of the field magnets f electricity conveyed per second across a unit 

>^ ~ ' 1^ m area of cross -section. 

Intensity of current is more properly called 

-^/^^fc^i density of current. (See Current Density. ) 

'V r ' ''b'flfr' ^BHS Current, Intermittent A current 

J-'fo '{'^ M§Ia| that does not flow continually, but which flows 

7ty;fCr jUSM an d ceases to flow at intervals, so that elec- 
tricity is practically alternately present and 

"^MB^^pjl^^^^^ absent from the circuit. 

Fig i8i Cause If Lead of Brushes. Current, Inverse-Secondary The 

, ,. . ,,--,.,. make-induced current. (See Current, Make- 

and those of the armature, the result of which is 

to displace the field magnet poles, and to cause a ' 

change in the density in the field. This is shown Current. Jacobi's Unit of Such 

in Fig. i8i, where the density of the lines of force a current that when passed through a volta- 

indicates the position of the diameter of commu- meter will liberate a cubic centimetre of 




Cur.J 



140 



[Cur. 



oxygen and hydrogen at O degrees C. and 
760 mm. barometric pressure. • 

One Jacobi's unit of current equals . 

10.32 
ampere. (Obsolete.) 

Current, Make-Induced — The 

current induced by a current in its own circuit 
on making or closing the same. 

The current produced in the secondary of 
an induction coil on the making or com- 
pletion of the circuit of the primary. 

The make-induced current is also called the 
inverse-secondary current, because its direction 
is opposite to that of the inducing current. 

Current, Make or Break Induced, Dura- 
tion of The time during which the 

induced inverse or direct-secondary currents 
continue. 

Blaserna made a number of experiments, which 
he claims shows : 

(1.) The greater the distance apart of the pri- 
mary and the secondary, that is, the less their 
mutual-induction, the less the maximum value of 
the secondary current, and the greater the delay 
in establishing that maximum. 

(2.) The delay in establishing the maximum of 
the break or direct -secondary current is not as 
great as in the case of the make, or inverse-sec- 
ondary current. 

(3.) When the coils are near together, the in- 
duced currents at starting are established by a 
series of electric oscillations, 

(4 ) The primary current establishes itself by a 
series of electrical oscillations. 

(5,) That the interposition of dielectric sub- 
stances, such as glass between Ihe coils, reduces 
the time between tht making or breaking of the 
primary current and the beginning of the sec- 
ondary current. This last conclusion was nega- 
tived by some experiments of Bernstein. 

Blaserna determined in the case of certain ex- 
periments the following value for the durations of 
the secondary currents : 

Inverse-secondary current lasts .000485 second. 

Direct -secondary current lasts .000275 second. 

Helmholtz contradicts the results of Blaserna, 

and asserts : 

~* (1.) That no perceptible difference in the zero 

points of the currents is produced by varying 

the distance between the primary and secondary. 

(2.) That the sparks produced by the breaking 



of the primary last for an appreciable time, some- 
thing like T ^oo to **hns of a second. 

(3) The duration of the break-spark is never 
constant, but depends in great part on the amount 
of platinum given off from the contacts at each 
spark. 

Current-Meter.— A form of galvanometer. 
(See Galvanometer,) 

Cnrrent, Momentary —A current 

that continues to flow but for a short time. 

Current, Multi-Phase A rotating 

current. (See Current, Rotating.) 

Current, Muscle In electro-thera- 
peutics, the current flowing through a muscle. 

Muscle currents are produced either by stimu- 
lation, or during activity of a muscle. According 
to L. Hermann, uninjured muscles, or perfectly 
dead muscles, yield no currents, but such cur- 
rents result only from an injury, (See Current \ 
Demarcation , ) 

Current, Non-Homogeneous Distribution 

of —Such a distribution of current pass- 
ing through a conductor in which there is an 
unequal density of current at all portions of 
any cross-section of the conductor. 

When a rapidly alternating current is passed 
through any solid conductor, the current density 
is greater at the surface and less towards the 
centre. The current distribution in such a con • 
ductor is non -homogeneous, and the want of uni- 
formity of current density is greater as the rapid- 
lty of alternation or periodicity is greater. 

Current, Outgoing —The current 

sent out over the line from a station provided 
with a duple < or quadruplex transmission, as 
distinguished from the received current. (See 
Current, Received) 

Current, Periodic —A simple 

periodic current. (See Currents, Simple 
Periodic) 

Current, Periodic, Power of An 

. amount of work, per second, equal to the 
product of the electromotive force taken at 
successive moments of time during a com- 
plete cycle, multiplied by the current strength 
taken at the corresponding moments during 
the cycle. 
Since the electromotive force and current in 



Car.] 



141 



[Cur, 



a periodic circuit may be represented by two 
simple harmonic functions, the mean value of 
the two, when of different amplitude and phase, 
is equal to the product of their maximum value 
by the cosine of their difference of phase divided 
by two. 

Current, Polarization In electro- 
therapeutics, the constant current which when 
passed through a nerve produces in it the 
electrotonic state. (See Electrotonus.) 

Current. Pulsating" A pulsatory 

current. (See Current, Pulsatory}) 

Current, Pulsatory A current, the 

.strength of which changes suddenly. 

The pulsatory current usually consists of sudden 
and distinct impulses, or rushes of current, in 
contradistinction to an undulatory or harmonically 
varying current. 

Current, Received The current 

received from the distant end of the line at a 
station provided with a duplex or quadruplex 
transmission as distinguished from the out- 
going current. 

A term sometimes used in telegraphy to 
distinguish between currents that come in over 
the line from a distant station, and those 
that are sent out to a distant station. 

Current, Rectilinear — A current 

flowing through straight or rectilinear por- 
tions of a circuit. 

In studying the effects of the attractions or repul- 
sions produced by electric currents the name ex- 
pressing the peculiarity of shape of any part of 
the circuit is often applied to the current flowing 
through that part of the circuit. Thus we speak 
of a rectilinear current, a sinuous current. 

Current, Reverse-Induced —The 

-current induced by a current in its own cir- 
cuit at the moment of making or closing the 
circuit. 

The current induced in the secondary on 
closing or making the circuit of the primary. 

This is called the reverse-induced current, be- 
cause its direction is opposite to that of the current 
in the inducing circuit. 

Current, Reversed A current whose 

direction is changed at intervals. (See Cur- 
rent, Alternating.) 



Current Reverser.- 

rent.) 



■(See Reverser, Cur- 



Current, Reversing a Changing the 

direction of an electric current. 

Current, Rotating A term applied 

to the current which results by combin- 
ing a number of alternating currents, whose 
phases are displaced with respect to one an- 
other. 

A rotating current is sometimes called a poly- 
phase or maltiple-pha.se current, particularly if 
there are three or more currents combined. 

The rotating current is employed by Tesla, 
Dobrowolsky and others in a system of distribu- 
tion by transformers in place of the ordinary 
alternating current. In practice, three alternating 
current are combined. The currents and their 
combination are obtained by means of a specially 
constructed alternator. When three currents are 
combined the displacement between each set of 
phases is 120 degrees. A rotating current, unlike 
an alternating current, possesses, in a certain 
sense, a definite direction of flow. Its effect on a 
magnetic needle is to cause rotation. Hence 
motors constructed on the principle of rotating 
currents will start with a load. 

Current, Rotatory • Phase • Alternating 

A term sometimes employed for a 

rotating electric current. (See Current, Ro- 
tating?) 

Current, Secretion In electro- 
therapeutics, a current following stimulation 
of the secretory nerves. 

Current, Simple-Harmonic A term 

sometimes used instead of simple-periodic 
current. (See Currents, Simple Periodic?) 

Current, Sinuous A term some- 
times applied to currents flowing through a 
sinuous conductor. 

Sinuous currents exert the same effects of attrac- 
tion or repulsion on magnets, or on neighboring 
circuits, as would a rectilinear current whose 
length is that of the axis of such sinuous current. 

This can be shown by approaching the circuit 
A' B', Fig. 182, consisting of the sinuous con- 
ductor A', and rectilinear conductor B', to the 
movable conductor A B C, on which it produces 
no effect. The current A', therefore, neutral- 



Cur.] 



142 



[Cur 



izes the effects of the current B' ; or, it is equal to 
it in effect. 




Fig. 182. Rectilinear Equivalent of Sinuous Current. 

In calculating the effects of sinuous currents it 
is convenient to consider them as consisting of a 




Fig. 183. Sinuous Currents. 
succession of short, straight portions at right an- 
gles to one another, as shown in Fig. 183. 

Current, Steady A current whose 

strength does not vary from time to time. 

In a steady current the quantity of electricity 
flowing through each unit of area of the equi- 
potential surface of the conductor is the same for 
each succeeding interval of time. Such a current 
is sometimes called a unifor?nly distributed cur- 
rent. 

Current Streamlets. — (See Streamlets, 
Current?) 

Current Strength. — The product obtained 
by dividing the electromotive force by the 
resistance. 

The current strength for a constant current 
according to Ohm's law is— 



Current strength is proportional to the amount 
of the magnetic or chemical (electrolytic) effects 
it is capable of producing. 

For a simple-periodic current, the current 
strength necessarily varies from time to time. 

The average current strength of a simple- 
periodic current is equal to the average impressed 
electromotive force divided by the impedance. 
(See Impedance. ) 

The maximum current strength is equal to the 
maximum impressed electromotive force divided 
by the impedance. 

Current, to Transform a To 

change the electromotive force of a current 
by its passage through a converter or trans- 
former. 

To convert a current. 

Current, Transforming a Chang- 
ing the electromotive force of a current by its 
passage through a converter or transformer. 

Current, Undulating An modu- 
latory current. (See Currents, Undulatory?) 

Current, Uniformly-Distributed : 

A term sometimes employed in the same 
sense as steady current. (See Current, 
Steady?) 

Current, Unit Strength of Such 

a strength of current that when passed 
through a circuit one centimetre in length, 
arranged in an arc one centimetre in radius, 
will exert a force of one dyne on a unit mag- 
net pole placed at the centre. 

This absolute unit is equal to ten amperes or 
practical units of current. (See Ampere.) 

Current, TariaMe Period of — 

The period which exists while an electric 
current is being increased or decreased in 
strength, or while it is being reversed. 

Currents, Action Physiological cur- 
rents obtained during the activity of a muscle 
or nerve. 

Currents, After In electro-thera- 
peutics, currents produced in nervous or 
muscular tissue when a constant current, 
which has been flowing through the same, 
has been stopped. 

After currents are due to internal polarization. 

Currents, Alternating-Primary 

The currents employed in the primary of a 



Cur.] 



143 



[Cur, 



transformer to induce alternating currents in 
the secondary. (See Transformer?) 

Currents, Alternating-Secondary — 

The currents induced in the secondary of a 
transformer by the alternating currents in the 
primary. (See Transformer?) 

Currents, Alternating, Shifting of Phase 

of (See Phase, Shifting of, of Alter- 
nating Currents?) 

Currents, Amperian The electric 

currents that are assumed in the amperian 
theory of magnetism to flow around the mole- 
cules of a magnet. (See Magnetism, Ampere s 
Theory of.) 

The amperian currents are to be distinguished 
from the eddy, JFoucatitt, or parasitical currents, 
since, unlike them, they are directed so as to pro 
duce useful effects. (See Currents, Eddy ) 

It is not believed that the amperian currents 
are produced in magnetizable substances by the 
act of magnetization. The atoms or molecules 
were magnetic originally. All the magnetizing 
force does is to arrange the molecule^ or atoms, 
or to set them in one and the same direction. 

Currents, Angular Currents flow- 
ing through circuits that cross or are inclined 
to one another at any angle. (See Dynamics, 
Electro?) 

Currents, Atomic A term some- 
times used instead of molecular or amperian 
currents. (See Currents, Amperian?) 

Currents, Attractions and Repulsions 

of The mutual attractions or repul- 
sions exerted by currents on one another 
through the interaction of their magnetic 
fields. (See Dynamics, Electro?) 

Currents, Commuted Electric cur- 
rents that have been caused to flow in one 
and the same direction. (See Commutator?) 

Currents, Commuting — Causing 

several currents to flow in one and the same 
direction. 

Currents, Component The two or 

more currents into which it may be conceived 
that a single current can be divided, so as 
to produce the same effects of attraction or 
repulsion that the single current would do. 



The idea of component currents is based on the 
similar idea of the components of any single 
force. 

Currents, Continuity of — The 

freedom from variation in current strength or 
current direction. 

Currents, Convection — Currents 

produced by the bodily carrying forward of 
static charges in convection streams. (See 
Streams, Convection?) 

In a convection current, the static charge is 
bodily carried forward. 

Rowland has shown experimentally that a 
moving electric charge is the equivalent of an 
electric current. He rotated a gilded ebonite 
disc between two gilt glass discs, near which 
were placed a number of delicate magnetic 
needles. When certain rapidity of rotation was 
obtained, the discs were found to affect the mag- 
netic needles the same as would a current of elec- 
tricity flowing in a circular conductor, whose 
form coincided with the periphery of the disc. 

Currents, Converted Electric cur- 
rents changed either in their electromotive 
force or in their strength, by passage through 
a converter or transformer. (See Trans- 
former?) 

Currents, Converting Changing 

the electromotive force of currents by their 
passage through a converter or transformer. 
(See Transformer?) 

Currents, Diaphragm Electric cur- 
rents produced by forcing a liquid through 
the capillary pores of a diaphragm. (See 
Osmose, Electric.) 

Currents, Earth Electric currents 

flowing through the earth, caused by a differ- 
ence of potential at different parts. 

The causes of these differences of potential are 
various and are not well understood. 

Currents, Eddy Useless currents 

produced in the pole pieces, armatures, field- 
magnet cores of dynamo-electric machines or 
motors, or other metallic masses, either by 
their motion through magnetic fields, or by 
variations in the strength of electric currents 
flowing near them. 

Sensible eddy currents are producd in the mass 



Cur.l 



14L 



[Cur. 



of the conducting wire on the armature of a 
dynamo-electric machine when the wire is com- 
paratively heavy. 

Such currents are called eddy currents, local 
currents, Foucault currents, or parasitical cur- 
lents. They form closed -circuits of comparatively 
low resistance, and tend to cause undue heating of 
armatures or pole pieces. They not only cause a 




Fig. 184. Foucault Currents in Pole Pieces. 

useless expenditure of energy, but interfere with 
the proper operation of the device. 

To reduce them as far as practicable, the pole 
pieces, armature cores or armature wires, are 
laminated. (See Core, Lamination of.) 

These local currents are perhaps preferably 
called Foucault currents when they take place 
in magnetic cores, pole pieces or armature 
cores, and eddy currents when they occur in the 
armature wire or conductor. When the armature 
conductor is made up of copper bars, for exam- 
ple, the eddy currents in the latter, are usually 
considerable. 

Since Foucault currents in dynamo-electric ma- 
chine cores are due to variations in the magnetic 




Fig. 18 'J. Foucault Currents in Pole Pieces. 

strength of the field magnets, or of the arma- 
ture, they will be of greatest intensity when the 
changes in the magnetic strength are the greatest 
and most sudden. 

These changes are most marked, and conse- 
quently the Foucault currents are strongest at those 
corners of the pole pieces of a dynamo from which 
the armature is moved in its rotation, as will be 
seen from an inspection of Fig. 184. 

Fig. 185, shows Foucault currents generated in 
pole pieces. 



Currents, Eddy-Conduction — A 

term employed for ordinary eddy currents in 
conductors, in order to distinguish them from 
eddy-displacement currents. (See Currents, 
Eddy-Displace7nent) 



Currents, Eddy Deep Seated 



Eddy- 



currents set up in the mass of a conductor sub- 
jected to electro-dynamic induction in con- 
tradistinction to superficially seated eddy cur- 
rents. (See Currents, Eddy, Superficial)) 

Currents, Eddy-Displacement — * 

Eddy currents produced in the mass of a. 
dielectric or insulator, when lines of magnetic 
or electrostatic force pass through the di- 
electric or insulator. 

Eddy-displacement currents are produced in 
a dielectric or non-conductor, when it is moved 
across a magnetic field, so as to cut the lines of 
magnetic force. 

Eddy displacement currents would also occur 
if a dielectric is subjected to varying electrostatic 
induction. 



Currents, Eddy, Superficial 



-Eddy 



currents produced in conducting substances 
that are limited to the outer layers thereof. 

The eddy currents produced by alternating 
currents are superficial if the alternating currents. 
are sufficiently rapid. The oscillatory currents pro- 
duced during the discharge of a Leyden jar are 
more superficial in proportion as the discharge 
takes place rapidly. When currents are pro- 
duced in a magnetizable body by the discharge 
of a Leyden jar, they are more and more super- 
ficial, as the discharge of the jar is more and more 
rapid. The reason a slow discharge of a jar or 
condenser produces a greater magnetizing effect 
is, because of the checking or screening action 
the superficial eddy currents exert on the interior 
of the mass of the magnetizable substance when 
the discharge is very rapid. 

Currents, Electrotonic In electro- 
therapeutics, currents due to internal polariza- 
tion in the nerve fibre between the conduct- 
ing core of- the nerves and the enclosing 

sheaths. 

Currents, Extra Currents pro- 
duced in a circuit by the induction of the 
current on itself on the opening or closing of 



Cur.] 



145 



LCur. 



the circuit. (See Curretits, Extra, Induc- 
tion, Self.) 

The extra current induced on breaking, flows 
in the same direction as the original current and 
acts to strengthen and prolong it. 

The extra current induced on making or com- 
pleting a circuit flows in the opposite direction 
to the original current and tends to oppose or re ■ 
tard the current. 

Both of these currents are called induced or 
extra currents. The former is called the direct- 
induced current, and the \a.ttev the reversed- in- 
duced current. (See Current, Direct-Induced. 
Current, Reversed-Induced. ) 

In order to distinguish this induction from that 
produced in a neighboring conductor by the pas- 
sage of the electric current, it is called set/ -induc- 
tion. (See Induction, Self. Induction, Mutual.) 

The effect on a telegraphic line of the self-in- 
duced or extra currents is to decrease the speed of 
signaling by retarding the beginning of a signal, 
and prolonging its cessation, 

The greater the number of turns of wire m a 
circuit, or magnet, and the greater the mass of 
iron in its core, the greater the strength of the 
extra currents. 

Currents, Foucault —A name some- 
times applied to eddy currents, especially in 
armature cores. (See Currents, Eddy) 

Currents, Heating Effects of- — The 

heat produced by the passage of an electric 
current through any circuit. (See Heat, Elec- 
tric.) 

Currents, Imbibition — — —Currents 
produced in tissues by the imbibition or ab- 
sorption of a fluid. 

Imbibition currents are a species of diaphragm 
currents. The absorption of a fluid at the 
demarcation surface of an injured nerve or 
muscle, or at the contracted portion of muscles, 
produces imbibition currents. 

Such currents are also produced in plants by 
the movement of fluids produced by bending the 
stalk or leaves, or by active movements of certain 
sensitive plants. 

Currents, Induced-Molecular or Atomic 

■ — Currents induced in the atoms or 

molecules of a magnetizable substance on its 
being brought into a magnetic field. 

These currents are called induced-molecular 
or induced-atomic currents in order to distin- 



guish them from the molecular, atomic or amperian 
currents, or the currents which are assumed to be 
always present. It is by the presence of these 
assumed induced-molecular currents that the 
phenomena of diamagnetism are explained by 
Weber. (See Diamagnetism, Weber's Theory 
of.) 

Currents, Local A name sometimes 

applied to eddy currents. (See Currents, 
Eddy.) 

Currents, Molecular or Atomic ■ 

A term sometimes employed for amperian 
currents. (See Currents, Amperian.) 

Currents, Natural A term some- 
times applied to earth currents. (See Cur- 
rents, Earthy 

Currents, Negative A term em- 
ployed in single-needle telegraphy for cur- 
rents sent over a line in a negative direction 
by depressing a key that connects the line 
with the negative pole of a battery and so 
deflects the needle to the left. (See Teleg- 
raphy, Single-Needled) 

Currents, Network of A term 

sometimes applied to a number of shunt or 
derived circuits. (See Circuit, Shunt. Cir- 
cuit, Derived. Laws, Kirchhoff's) 

Currents of Motion. — A term sometimes 
employed in electro-therapeutics for the cur- 
rents of electricity that traverse healthy 
muscle or nerve tissue during the sudden con- 
traction or relaxation thereof. 

The existence of these currents is denied by 
some. 

Currents of Rest. — A term sometimes em- 
ployed in electro-therapeutics for the cur- 
rents of electricity that traverse healthy 
muscle or nerve tissue while the muscles are 
passive. 

The existence of these currents is denied by 
some. 

Currents, Orders of Induced elec- 
tric currents named from the order in which 
they are induced, as currents of the first, 
second, third, fourth, etc., orders. 

An induced current can be caused to induce an- 
other current in a neighboring circuit, and this a 
third current, and so on. Such currents are dis- 



Cur.] 



146 



[Cur. 



tinguished by the term, currents of the second, 
third, fourth, etc., order. (See Coils, Henrys.) 

Currents, Parasitical A name 

sometimes applied to eddy currents. (See 
Currents, Eddy.) 

Currents, Positive A term em- 
ployed in single-needle telegraphy for currents 
sent over the line in a positive direction by de- 
pressing a key that connects the line with 
the positive pole of a battery and so deflects 
the needle to the right. (See Telegraphy, 
Single-Needle .) 

Currents, Reversed A name some- 
times applied to alternating currents. (See 
Current, Alternating^ 

Currents, Secondary The currents 

produced by secondary batteries in contra- 
distinction to the currents produced by 
primary batteries. 

The currents producea by the secondary 
conductor of an induction coil, as distinguished 
from the currents sent into the primaries. 

This second use of the term secondary current 
is more usual. 

Currents, Self-Induced A current 

produced by self-induction. 

An extra current. (See Induction, Self. 
Currents, Extra.} 

Currents, Simple Periodic Cur- 
rents, the flow of which is variable, both in 
strength and duration, and in which the flow 
of electricity, passing any section of the con- 
ductor, may be represented by a simple peri- 
odic curve. 

A current of such a nature that the con- 
tinuous variation of the flow of electricity 
past any area of cross-section of the con- 
ductor, or the variations in the electromotive 
force of which can be expressed by a simple- 
periodic or harmonic curve. (See Curve, 
Simple-Harmonic?) 

Alternate currents are simple-periodic currents. 

The average current strength of simple-periodic 
currents is equal to the average impressed electro- 
motive force divided by the impedance. 

The transmission of rapidly varying or sim- 
ple-periodic currents through conductors differs 
very greatly from the transmission of steady cur- 



rents. With a steady current, the current density 
is the same for all areas of cross-section of the 
conductor. For a rapidly intermittent current, 
the current density is greater near the surface, 
and when the rate of intermission is sufficiently 
great, the current is entirely absent at the centre 
of the conductor. 

Lord Rayleigh has shown that when the rate of 
intermission is 1,050 per second, the effective re- 
sistance of a wire 160 mm. in length, and 30 mm. 
in diameter, is 1 .84 times its resistance to steady 
currents. He found that the increase of resist- 
ance is greater in the case of conductors of great 
diameter than in those of small diameter. 

As regards the character of conductor best 
suited for transmitting rapidly alternating cur- 
rents, it can be shown : 

(1.) That for transmitting alternate currents of 
moderate frequency, say of about 1,000 per sec- 
ond, copper conductors should be used in prefer- 
ence to rods of iron. 

(2.) That the conductor should be in the form 
of thin strips, or if tubular, of thin walls. 

(3.) That the mere stranding of the conductor, 
i. e., forming it of separate insulated conductors 
connected in parallel, will be of no effect in pre- 
venting the current from acting on the outside of 
the conductor, unless the conductor be arranged 
in the form of a cable, in which one part forms a 
lead, and another part the return. 

Stephan draws the following analogy between 
the flow of alternating currents in a conductor 
and the flow of heat in a hot wire : 

" Suppose a wire or conductor, uniformly heated 
from centre to circumference, be suddenly taken 
into a space where the temperature is high, the 
outer portions of the wire first rise in temperature, 
and afterwards the inner portions. In the case Of 
a conductor of circular cross-section, the heat 
penetrates successive concentric layers. The same 
phenomena occur when an electromotive force is 
suddenly set up between the ends of a cylindrical 
conductor. The current gradually penetrates the 
conductor from the outside to the centre. 

" Now suppose the heated wire is carried into a 
cooler space, the heat waves -pass out radially 
from the centre towards the circumference. The 
cooling wire corresponds to the case of a con- 
ductor in which the external electromotive force 
is suddenly removed." 

According to this conception, the heat conduct- 
ing power of any substance corresponds to its 
electrical conducting power. 



Cur.] 



147 



[Cur. 



According to Stephan, in the case of a con- 
ductor of iron of 4 mm. in diameter, traversed by 
an alternating current of 250 alternations per 
second, the current density on the surface is about 
twenty-five times as great as that at its axis. 

Where the conductor is of non-magnetic mate- 
rial, the difference in the current density is not so 
marked. 

Rapidly intermittent currents produce a real 
increase in the resistance of the conductor, which 
must not be confused with the fact that the impe- 
dance is greater than the ohmic resistance, but 
rather as an actual increase in the rate at which 
energy is dissipated per unit of current. 

Since current density is greatest at the outside 
portions of a conductor, and the central portions 
are nearly, if not entirely, deserted by the cur- 
rent, we may regard the conductor as having 
the ohmic resistance of a hollow cylinder of the 
same diameter as the conductor, with a cor- 
respondingly smaller area of cross-section, and 
therefore, of greater ohmic resistance per unit of 
length. 

The condition of affairs in the case of a con- 
ductor in which a current of electricity is begin- 
ning to flow, is now very generally regarded 
somewhat as follow s, viz.: 

The current begins at the surface of the con- 
ductor, and more or less slowly soaks through 
towards the centre. If the current is constant, the 
current soon reaches the deepest layers; but, if it 
is rapidly intermittent, before it can soak very far 
into the conductor towards its axis, it is turned 
back towards the surface, and so becomes con- 
fined to layers which will be more and more super- 
ficial, as the rapidity of reversal increases. 

Therefore, for convenience, we may regard a 
solid conductor, through which a rapidly inter- 
mittent current of e'ectricity is flowing, as being 
practically converted into a hollow cylinder of 
the same diameter as the solid conductor, the 
area of cross -section of which hollow cylinder 
becomes smaller and smaller, as the rapidity of 
alternation is increased. 

Another, and perhaps the more correct concep- 
tion of the condition of affairs in a solid conductor 
traversed by a rapidly alternating current of elec- 
tricity, has been pointed out by Maxwell, and after- 
wards by Heavyside, Rayleigh and Hughes. This 
conception is to regard the central portions of the 
conductor as possessing a counter electromotive 
force greater than the outer portions. The entire 
current flowing across any section of a conductor 



miy be regarded as made up of little current 
s.ream/ets, parallel to one another. 

The central streamlets, or filaments, from their 
mutual induction on one another, experience a 
greater resistance in reaching their full strength 
than the surface filaments do. Taken in this 
sense, we may state generally that the transmis- 
sion of rapidly alternating currents through con- 
ductors depends on the inductance, rather than 
on the resistance; but for steady currents, it de- 
pends more on the resistance than on the induct- 
ance. 

In periodic or oscillatory currents, as those 
produced by the discharge of a Leyden jar, or 
condenser, the surface streamlets have a current 
density far greater than the central streamlets. 

The true or ohmic resistance of the circuit is a 
minimum when the current is uniformly distrib- 
uted through all parts of the cross-section of the 
conductor, and the dissipation of energy through 
the generation of heat is less than for any other 
distribution. 

The conception of a periodic current flowing 
through a conductor, starting from the surface 
and gradually soaking in towards the centre, 
regards the energy of an electric current — not as 
being pushed through the conductor, as water 
through a pipe, but as actually being absorbed at 
its surface, from the surrounding dielectric, or as 
being, so to speak, rained down on the conductor 
from the space outside of it. 

Currents, Swelling In electro- 
therapeutics, currents that begin weak and are 
gradually made stronger and then weaker. 

Currents, Swelling-Faradic —A 

term employed in electro-therapeutics for f ara- 
die currents that are caused to gradually in- 
crease in strength and then to gradually de- 
crease to zero strength. 

Currents, Transient Currents that 

are but of momentary duration. 

Currents, Undulatory Currents the 

strength and direction of whose flow gradually 
change. 

The term undulatory currents is used in con- 
tradistinction to pulsatory currents, in which the 
strength changes suddenly. In actual practice, 
such currents differ from undulatory currents 
more in degree than in kind, since, when sent 
into a line, the effects of retardation tend to 
obliterate, to a greater or less extent, the sudden 



Cur.] 



148 



[Cur. 



differences in intensity on which their pulsatory 
character depends. 

The currents produced in the coils of the Sie- 
mens magneto- electric key, in which the me- 
chanical to-and-fro motion of the key sends elec- 
trical impulses into the line, are, in point of fact, 
undulatory in character, when they follow one an- 
other rapidly. 

The currents in most dynamo-electric machines, 
the number of whose armature coils is compara- 
tively great, are, so far as the variations in their 
intensity or strength are concerned, undulatory 
in character even when non-commuted. 

The currents on all telephone lines that trans- 
mit articulate speech are undulatory. This is 
true, whether the transmitter employed merely 
varies the resistance by variations of pressure, or 
actually employs makes-and-breaks that rapidly 
follow one another. — (See Current, Pulsatory, 
Current, Interi7iittent .) 

Curtain, Auroral — A sheet of 

auroral light having the shape of a curtain. 
(See Aurora Borealzs.) 



The ballistic curve has a smaller vertical height 
than the parabola. The projectile also has a 



Curve, Asymptote of 



-A straight 




Fig. 1 8 6. Asynnptote 
of Curve. 



line which continually approaches a curved 
line, but meets or becomes tangent to such 
curved line only at an infinite distance. 

In Fig. l86, the curve C D, continually ap- 
proaches the asymptote y z, but never meets it. 

It is at first difficult to un- 
derstand how one line can 
continually approach an- 
other and yet never meet it. 
But it will be readily under- 
stood if it is remembered 
that in all cases of asymp- 
totic approach each advance 
becomes smaller and smaller. 

This mathematical conception is like a value 
which, although constantly reduced to one-half 
of its former value, is nevertheless never reduced 
to zero or no value. 

Curve, Ballistic The curve ac- 
tually described by a projectile thrown in 
any other than a vertical direction through 
the air. 

The path of a projectile in a vacuum is a para- 
bola—that is, the path A E B, Fig. 187. In air, 
the effects of fluid resistances cause the projectile 
to take the path A C D, called a ballistic curve. 




)1 F 
Fig. 187. Ballistic Curve. 

smaller vertical range. Instead of reaching the 
point B, it continually approaches the perpen- 
dicular E F. 

Curve, Characteristic A diagram 

in which a curve is employed to represent 
the ratio of certain varying values. 

The electromotive force generated in the arma- 
ture coils of a dynamo -electric machine, when the 
magnetic field is of a constant intensity, is theo- 
retically proportional to the speed of rotation. In 
practice this is modified by a number of circum- 
stances. 

The relation existing between the speed 
and electromotive force may be graphically rep- 
resented by referring the values to two straight 
lines, one horizontal and the other vertical, called 
respectively the axes of abscissas and ordinates. 
(See Abscissas, Axis of.) If, in a given case, the 
number of revolutions 
is marked off along 
the horizontal line 
from the point o, Fig. 
188, in distances from 
o, proportional to the 
number of revolu- 
tions, and the corre- 
sponding electromo- 
tive forces are marked 
off along the vertical line in distances from O, 
proportional to the electromotive forces, the 
points where these lines intersect will form the 
characteristic curve as shown in Fig. 188. 

Curve, Characteristic, of Parallel Trans- 

■A curve so drawn that its 




100 : . 



Fig. 



) 500 

Revolutions. 
188. Characteristic 
Curve. 



1000 



former — 

ordinate and abscissa at any point represent 
the secondary electromotive force and the sec- 
ondary current of a multiple connected trans- 
former, when the resistance of the secondary 
circuit has a certain definite value. 

With a constant electromotive force in the pri- 



Car.] 



149 



[Cur. 



i 

. _— 



mary circuit, i. <?.,with the transformers in parallel, 
the characteristic curve is a straight line parallel 
to the axis of the current. This curve, as shown 
in Fig. 189, is practically a straight line. The par- 
allel transformer will be y 
practically self- regulating 
under a constant primary 
electromotive force. 

According to Forbes, if q 
a transformer has its lamp pi gt x g Q ^ Character- 
load in parallel with the istic of Parallel Trans- 
secondary circuit, the ex- former. 
tinction of its lamps will decrease the efficiency 
of the transformer. The efficiency is therefore 
less for light loads than for heavy loads of parallel 
lamps up to a certain point. 

Curve, Characteristic, of Series Trans- 
former A curve so drawn that its 

ordinate and abscissa at any point represent 
the secondary electromotive force and second- 
ary current of a series-connected transformer, 
when the resistance of the secondary current 
has a certain definite value. 

Fig. 190 shows characteristic curve of a series 




Fig. I go. Characteristic of Series Transformer. 

transformer. O a, is drawn perpendicular to the 
line representing the secondary current, and a b, 
perpendicular to O a, represents the correspond- 
ing secondary electromotive force. The various 
positions of b, as different values are given to O a, 
produce the elliptic curve which is the character- 
istic curve of the series cransformer. 

" A series transformer, " says Fleming, "with 
a core sufficiently large to avoid saturation, can 
never be self-regulating if so used. It can only 
be made self-regulating with a non- saturated core, 
when working near the extremities of its charac- 
teristic, either with a small secondary current 
or a low electromotive force. Both of these con- 
ditions are uncommercial." 

Curve, Life, of Incandescent Lamp 



—A curve in which the life of an electric 
lamp is represented by means of abscissas and 
ordinates proportional to the life in hours and 
the candle-power or the volts respectively. 

Curve, Logarithmic A curve in 

which the rate of increase or decrease of the 
ordinate is proportional to the ordinate itself. 

On the line O X, Fig. 191, mark off the time 




Fig. 1 q 1. Logarithmic Curve. 

in lengths, reckoned from O. Represent the 
current strength by lines drawn vertically to the 

time-line. Let O Y, equal C = 77- 

Applying the electromotive force, the current 
grows in the wire as represented by the graphic 
curve. 

According to Fleming, the growth of this cur- 
rent takes place according to the following law, 
viz.: "The current strength at any instant, 
added to the rate of growth of the current strength 
at that instant multiplied by the time-constant, is 
equal to the current which would exist if induc- 
tion were zero. ' ' 



Curve, Permeability 



-A curve repre- 



senting the magnetic permeability of a mag- 
netic substance. 

There is a certain temperature for every para- 
magnetic substance, at which its permeability is 
no greater than that of air. This temperature 
for iron is reached at about 750 degrees C; for 
nickel, at about 400 degrees C. 

Curve, Simple-Harmonic — The 

curve which results when a simple-harmonic 
motion in one line is compounded with a uni- 
form motion in a straight line, at right angles 
thereto. 

A harmonic curve is sometimes called a curve 
of sines, because the abscissas of the curve are 
proportional to the times, while the ordinates are 
proportional to the sines of the angles, which are 
themselves proportional to the times. 



€ur.] 



150 



[Cut. 



-Curves drawn 



Curves, Isochasmen — 

on the earth's surface between zones having 
equal frequency of auroral discharges. 

The isochasmen curves are nearly at right 
angles to the magnetic meridian. 

Curves, Magnetic — Curved lines 

showing the direction of the lines of mag- 
netic force in any field, formed by sprinkling 
iron filings on a sheet of paper or glass held 
in the field of a magnet, and gently tapping 
the support so as to permit the filings- to prop- 
erly arrange themselves. (See Figures, 
Magnetic^) 



Cut-In, To 



-To introduce an electro- 



receptive device into the circuit of an electric 
source by completing or making the circuit 
through it. 

Cut-Off, Automatic Gas A device 

for automatically cutting out the battery 
from an electric gas-lighting circuit on the 
accidental grounding of the circuit. 

Unless the battery is disconnected from the cir- 
cuit on the establishing of a ground, the battery 
will polarize and soon become useless. 

Cut-Out, A A device by means of 

which an electro-receptive device or loop may 
be thrown out of the circuit of an electric 
source. 

In any system of light or power distribution, a 
cut out is generally placed outside a building 
into which a loop or branch of t^e main circuit 
runs, so as to permit that loop or branch to be 
readily disconnected therefrom. In the same way 
cut-out keys or switches are generally placed in 
the circuit of the loop and each electro-receptive 
device. 

Cut-Out, Air-Space ■ — A modified 

form of paper cut-out, in which the disc of 
paper or mica is replaced by the resistance of 
an air-space. 

Although the resistance of an air-space is so 
high as to be practically immeasurable, yet it is 
overcome or broken by a much lower differ- 
ence of potential than an equal thickness of 
paper or mica. (See Path, Alternative. Cut- 
Out, Film.) 



Cut-Out, Automatic Any device 

that will automatically cut-out, or remove, a 
translating device, or an electric source, from 
an electric circuit, whenever any predeter- 
mined effect is produced. 

Cut-Out, Automatic, for Multiple-Con- 
nected Electro-Receptive Devices — 

A device for automatically cutting an electro- 
receptive device, such as a lamp, out of the 
circuit of the leads. 

Automatic cut-outs for incandescent lamps, 
when connected to the leads in multiple-arc, con- 
sist of strips of readily melted metal called safety 
fuses, which on the passage of an excessive cur- 
rent fuse, and thus automatically break the cir- 




Fig. IQ2, Ceiling Cut-Out. 

cuit in that particular branch. (See Catch, 
Safety.) 

A form of ceiling cut-out, made of porcelain, is 
shown in Fig. 192, with the two halves separated 




Ceiling Cut- Out, 



to show interior details, and in Fig. 193, with the 
two halves placed together. 



Cut.] 



151 



[Cyc 



Cut-Out, Automatic, for Series-Connected 

Electro-Receptive Devices A device 

whereby an electro-receptive device, such 
as an electric arc lamp, is, to all intents and 
purposes, automatically cut out, or removed 
from the circuit, by means of a shunt of low- 
resistance, which permits the greater part of 
the current to flow past the lamp. 

It will be observed that the lamp, though still in 
the circuit, is to all practical intents cut out from 
the same, since the proportion of the current 
that now passes through it is too small to oper- 
ate it. 

In most series arc lamps, cut-outs are oper- 
ated by means of an electro -magnet placed in a 
shunt circuit of high resistance around the car- 
bons., If the carbons fail to properly feed, the 
arc increases in length and consequently in resist- 
ance. More current passes through the shunt 
magnet, until finally s when a certain predeter- 
mined limit is reached, the armature of the elec- 
tro-magnct is attracted to the magnet pole and 
mechanically completes the short circuit past the 
lampo 

In some automatic cut-outs the fusion of a 
readily fused wire, placed in a shunt circuit 
around the carbons, permits a spring to complete 
the short circuit. 

The automatic cut-out prevents the accidental 
extinguishing of any single lamp in a series cir- 
cuit from extinguishing the remaining lamps on 
that circuit. 

Cut-Out, Automatic Time — A 

device arranged so as to automatically cut out 
a translating device, or an electric source, from 
a circuit, at the end of a certain predetermined 
time. 

Cut-Out, Duplex A cut-out so 

arranged that when one bar or strip is fused 
or melted by an abnormal current another can 
be immediately substituted for it. 

Cut-Out, Film A cut-out in which 

a film, or sheet of paper or mica, is interposed 
between a line plate and an earth plate, which, 
when punctured by a spark, short circuits the 
instruments on the line. 

Cut-Out, Main-Line — An auto- 
matic cut-out placed on the main line. (See 
Cut-Out, Automatic') 



A form of main-line cut-out is shown in Fig. 




Fig. IQ4. Main-Line Cut'Out. 

194. The fuses are shown as attached to the fuse- 
block. 

Cut-Out, Paper A term sometimes 

employed instead of film cut-out. (See Cut- 
Out, Film?) 

Cut-Out, Rosette — - A rosette for an 

electrolier, containing a cut-out. (See Ro- 
sette) 

Cut-Out, Spring-Jack A device 

similar in general construction to a spring- 
jack, but employed to cut out a circuit. 

An insulated plug is thrust between spring 
contacts, thus breaking the circuit by forcing 
them apart. 

Cut Out, To To remove an elec- 
tro-receptive device from the circuit of an 
electric source by disconnecting or diverting 
the circuit from it. 

Cutting" Lines of Force. — (See Force, 
Lines of. Cutting) 

Cycle. — A period of time within which a 
certain series of phenomena regularly recur, 
in the same order. 

Cycle, Magnetic A single round 

of magnetic changes to which a magnetizable 



Cyc] 



152 



[Dam. 



substance, such as a piece of iron, is subjected 
when it is magnetized from zero to a cer- 
tain maximum magnetization, then decreased 
to zero, reversed and carried to a negative 
maximum, and then decreased again to zero. 

Cyclical Magnetic Variation. — (See Va- 
riation, Cyclical Magnetic?) 

Cyclotrope, — A name proposed in place 
of transformer or converter. (See Trans- 
former) 

Cylinder, Yortex A number of 

vortex stream-lines grouped parallel to one 
another about a straight line which forms the 
axis or core of the vortex. 

Cylindrical Armature. — (See Armature, 
Cylindrical?) 

Cylindrical Carbon Electrodes.— (See 
Electrodes, Cylindrical Carbon) 

Cylindrical Electro-Magnet. — (See Mag- 
net, Electro, Cyli?idrical) 



Cylindrical Magnet. — (See Magnet, Cyl- 
indrical) 

Cylindrical Ring Armature. — (See Arm- 
ature, Cylindrical Ring) 

Cymogene.-^-An extremely volatile liquid 
which is given off from crude coal oil during 
the early parts of its distillation. 

The two liquids which are obtained from the 
condensation of the vapors given off during the 
first parts of the distillation of coal oil are called 
cymogene, and rhigolene. These liquids are em- 
ployed on account of their extreme volatility for 
the artificial production of cold. 

Rhigolene is employed by some for the treat- 
ment or flashing of the carbons used in incan - 
descent lamps. (See Carbons, Flashing Process 
for.) 

Cystoscopy, Electric A name given 

to Hitze's method of ocular examination 
of the human bladder by electric illumina- 
tion. 



Damped Magnetic Needle. — (See Needle, 
Magnetic, Damped) 

Damper. — A metallic cylinder provided in 
an induction coil so as to partially or com- 
pletely surround the iron core, for the purpose 
of varying the intensity of the currents induced 
in the secondary. 

The metallic cylinder acts as a screen or shield 
for the rapidly alternating currents traversing the 
field of the primary. (See Screening, Magnetic.} 
As the damper is pulled out, a greater length of 
the core is exposed to the induction. 

Damper. — A term sometimes applied to a 
dash-pot or other similar apparatus provided 
for the purpose of preventing the too sudden 
movement of a lever or other part of a device. 
(SeeDasn-Pot) 

Some form of damper or dash-pot is used on 
most electric arc lamps, the upper carbon of 
which is fed by a direct fall. 

The double use of this word is unfortunate. 

Damping. — The act of stopping vibratory 
motion such as bringing a swinging mag- 



netic needle quickly to rest, so as to deter- 
mine the amount of its deflection, without 
waiting until it comes to rest after repeated 
swingings to and fro. 

Damping devices are such as offer resistance 
to quick motion, or high velocities. Those gen- 
erally employed in electrical apparatus are either 
air or fluid friction, obtained by placing vanes 
on the axis of rotation, or by checking the move- 
ments of the needle by means of the currents it 
sets up, during its motion, in the mass of any con- 
ducting metal placed near it. These currents, as 
Lenz has shown, always tend to produce motion 
in a direction opposed to that of the motion caus- 
ing them. Bell-shaped magnets are especially 
suitable for this kind of damping. (See Magnet ', 
Bell Shaded.) 

The needle of a galvanometer is dead-beat when 
its moment of inertia is so small that its oscillations 
in an intense field are very quick, and the mirror, 
acting as a vane, causes the movements to die out 
very rapidly, and the needle therefore moves 
sharply over the scale from point to point and 
comes quickly to a dead stop. When the needle 
or swinging coil is heavy and moves in an intense 



Dam.] 



153 



[Dea, 



field, as in the Deprez-d' Arson val galvanometer, 
the movements are dead-beat. 

Damping by means of pieces of india rubber is 
often applied to telephone diaphragms to prevent 
their excessive or continued vibration. 

Damping 1 , Electric A term some- 
times employed to express a decrease in 
the intensity of the electric oscillations pro- 
duced in a conductor by electric resonance, 
under circumstances where higher overtones 
are set up in the conductor. 

Daniell's Toltaic Cell.— (See Cell, Vol- 
taic, Darnell's.) 

Dark-Space, Crookes' (See Space, 

Dark, Crookes '.) 

Dark-Space, Faraday's (See Space, 

Dark, Faraday's?) 

Dash-Pot. — A mechanical device to prevent 
too sudden motion in a movable part of any 
apparatus. 

The dash-pot of an automatic regulator, or of 
an arc -lamp, is provided to prevent too sudden 
movements of the collecting brushes on the com- 
mutator cylinder, or the too sudden fall of the 
upper carbon. Such devices consist essentially of 
a loose fitting piston that moves through air or 
glycerine. 

Dash-pots are species of damping devices, and, 
like the damping arrangements on galvanometers 
or magnet needles, prevent a too free movement 
of the parts with which they are connected. (See 
Damper. Damping.) 

Day, Normal Magnetic A day dur- 
ing which the value of the earth's magnetic 
elements does not vary greatly from their 
mean value. (See Elejnents, Magnetic, of a 
Place.) 

Day of Disturbance, Magnetic — 

A day during which the mean departure of 
the readings of a declinometer at any place, 
from the normal monthly value at that place, 
is once and a half the average. — {Lloyd.) 

Dead-Beat. — Such a motion of a galvanom- 
eter needle in which the needle moves sharply 
over the scale from point to point and comes 
quickly to rest. (See Damping.) 

Dead-Beat Discharge. — (See Discharge, 
Dead-Beat.) 



Dead-Beat Galvanometer. — (See Galva- 
nometer, Dead-Beat) 
Dead Dipping. — (See Dipping, Dead.) 
Dead Earth. — (See Earth, Dead or Total) 

Dead Turns of Armature Wire, or Dead 
Wire. — (See Turns, Dead, of Armature 
Wire) 

Death, Electric — Death resulting 

from the passage of an electric current 
through the human body. 

The exact manner in which an electric current 
causes death is not known. When the current is 
sufficiently powerful, as in a lightning flash, or a 
powerful dynamo current, insensibility is prac- 
tically instantaneous. 

Death may be occasioned: 

(i.) As the direct result of physiological shock. 

(2.) From the action of the current on the res- 
piratory centres. 

(3.) From the actual inability of the nerves or 
muscles, or both, to perform their functions. 

(4.) From an actual electrolytic decomposition 
of the blood or tissues of the body. 

(5.) From the polarization of those parts of the 
body through which the current passes. 

(6.) From an actual rupture of parts by a dis- 
ruptive discharge. 

The current required to cause death will de- 
pend on a variety of circumstances, among 
which are: 

(1.) The particular path the current takes 
through the body, with reference to the vital 
organs that may lie in this path. 

(2.) The freedom or absence of sudden varia- 
tions of electromotive force. 

(3.) The time the current continues to pass 
through the body. 

In some fatal cases, it is probably the extra- 
current, or the induced-direct current on break- 
ing, that causes death, since, as is well known, 
its electromotive force may be many times 
greater than that of the original current. 

A comparatively low-potential continuous-cur- 
rent, cannot, therefore, be properly regarded 
as entirely harmless, simply because its electro- 
motive force is necessarily small. In the case of 
alternating currents the danger increases after a 
certain point with the number of alternations per 
second. When, however, the number of alter- 
nations per second reaches a given number, the 
danger decreases as the frequency of alternations 



Dec] 



154 



LDeg. 



increases. This was conclusively shown by the 
independent investigations of Tatum and Tesla. 

Decalescence. — A term proposed by Prof. 
Elihu Thomson for an absorption of sensible 
heat, which occurs at a certain time during 
the heating of a bar of steel. 

Decalescence will thus be observed to be the 
reverse of recalescence, which is the phenome- 
non of the emission of sensible heat at a certain 
time during the cooling of a heated bar of 
steel. (See Recalescence.) 

Deci (as a prefix). — The one-tenth. 

Deci-Ampere. — One-tenth of an ampere. 

Deci-Amp§re Balance. — (See Balance, 
Deci-Ampere?) 

Deci-Lux. — The one-tenth of a lux. (See 
Lux.) 

Declination. — The variation of a mag- 
netic needle from the true geographical north. 

The magnetic declination is east or west. (See 
Needle, Magnetic, Declination of.) 

Declination, Angle of The angle 

which measures the deviation of the mag- 
netic needle to the east 
or west of the true geo- 
graphical north. 

The angle of variation 
of a magnetic needle. 

In Fig. 195, if N S, rep- 
resents the true north and 
south line, the angle of de- 
clination is N O A, and Fig 
the sign of the variation is 
east, because the deviation of the needle is to- 
ward the east. (See Needle, Magnetic, Declina- 
tion of.) 

Declinometer. — A magnetic needle suit- 
ably arranged for the measurement of the 
value of the magnetic declination or varia- 
tion at any place. 

Decomposition. — In chemistry the separa- 
tion of a molecule into its constituent atoms 
or groups of atoms. (See Molecule. Atom.) 

Decomposition, Electric — Chem- 
ical decomposition by means of an electric dis- 
charge or current. 

This decomposition may result from an increase 




igS- Declination 
0/ Needle. 



of temperature produced by the electric discharge, 
or from the passage of the current. In the latter 
case it is more properly called electrolytic decom- 
position. 

Decomposition, Electric, Crystallization 
by (See Crystallization by Electro- 
lytic al Decomposition?) 

Decomposition, Electrolytic The 

separation of a molecule into its constituent 
atoms or groups of atoms by the action of 
the electric current. 

These atoms or groups of atoms are either 
electro-positive or electro-negative in character. 
(See Electrolysis, Anion. Kathion.) 

De-energize. — To deprive an electro-recep- 
tive device of its operating current. 

De-energizing. — Depriving an electro- 
receptive device of its operating current. 

Deep-Seated Eddy Currents. — (See Cur- 
re Jits, Eddy, Deep-Seated?) 

Deep-Water Submarine Cable. — (See 
Cable, Submarine, Deep- Sea.) 

Deflagration, Electrical The fusion 

and volatilization of metallic substances by the 
electric current. 

Deflagrator. — The name given to a voltaic 
battery, of small internal resistance, employed 
by Hare in the electric deflagration of metal- 
lic substances. 

Deflection Method.— (See Method, Deflec- 
tion.) 

Deflection of Magnetic Needle. — (See 
Needle, Magnetic, Deflection of.) 

Degeneration. — Such a degeneration of the 
muscular or cellular structure of any cell or 
organ that incapacitates it from performing its 
functions. 

Degeneration of Energy.— (See Energy, 
Degeneration of) 

Degeneration, Partial, Reaction of 

— That form of alteration to electric stimula- 
tion, in which the nerves show no abnormal 
reaction to electric stimulation, while the 
muscles, when directly stimulated by the con- 
stant current, exhibit the reaction of degen- 
eration. (See Degeneration, Reactio?i of?) 



Deg.] 



155 



[Dep. 



Degeneration, Reaction of — A 

qualitative and quantitative alteration of 
nerves and muscles to electric stimulation. 

According to Landois and Stirling the following 
conditions characterize essentially the reaction of 
degeneration: "The excitability of the muscles 
is diminished or abolished for the faradic cur- 
rent, while it is increased for the galvanic current 
from the third to the fif:y -eighth day ; it again 
diminishes, however, with variations, from the 
seventy-second to eightieth day ; the anodic clos- 
ing contraction is stronger than the kathodic 
closing contraction." * * * "The diminu- 
tion of the excitability of the nerves is similar for 
the galvanic and faradic currents." 

Deka (as a prefix). — Ten times. 

Deka-Ampere. — Ten amperes. 

Deka-Ampere Balance. — (See Balance, 
Deka- Ampere.) 

De la Rue's Standard Toltaic Cell. — (See 
Cell, Voltaic, Standard, De la Rues.) 

Deliquescence. — The solution of a crystal- 
line solid arising- from its absorption of vapor 
of water from the atmosphere. 

DeinagnetizaMe. — Capable of being- de- 
prived of magnetism. 

Demagnetization. — A process, generally di- 
rectly opposite to that for producing a magnet, 
by means of which the magnet may be de- 
prived of its magnetism. 

A magnet may be deprived of its magnetism, 
or be demagnetized — 

(i.) By heating it to redness. 

(2. ) By touching to its poles magnet poles of the 
same name as its own. 

(3.) By reversing the directions of the motions 
by which its magnetism was originally imparted, 
if magnetized by touch, by stroking it with a 
magnet in the opposite direction from that which 
would have to be given in order to produce the 
magnetization which is to be removed from it. 

(4.) By exposing it in a helix to the influence of 
currents which will impart magnetism opposite to 
that which it originally possessed. 

Avria claims that a smaller magnetizing force is 
required to demagnetize a needle than is required 
to magnetize it. 

Demagnetization of Watches. — (See 
Watches, Demagnetization of.) 



Demagnetize. — To deprive of magnetism. 

Demagnetizing. — Depriving of magnetiza- 
tion. 

Demarcation Current. — (See Current, De- 
marcation^) 

Demarcation Surface. — (See Surface, De- 
marcation) 

Density, Electric The quantity of 

free electricity on any unit of area of surface. 

The density is said to be positive or negative 
according as to whether the charge is positive or 
negative. (See Charge, Density of. Plane, 
Magnetic Proof. ) 

Density, Magnetic The strength 

of magnetism as measured by the number of 
lines of magnetic force that pass through a 
unit area of cross-section of the magnet, i. e., 
a section taken at right angles to the lines of 
force. (See Field, Magnetic) 

Density of Charge. — (See Charge, Den- 
sity of.) 

Density of Current. — (See Current 
Density.) 

Density of Field. — (See Field, Density of) 

Density, Surface A phrase used 

by Coulomb to mean the quantity of elec- 
tricity per unit of area at any point on a sur- 
face. (See Charge Density. Density, 
Electric.) 

Dental-Mallet, Electro-Magnetic 

A mallet for rilling teeth, the blows of which 
are struck by means of electrically-driven 
mechanism. 

Electro-magnetism was first employed for this 
purpose by Bonwill, of Philadelphia. 

Dentiplione. — An audiphone. (See Audi- 
phone) 

Depolarization. — The act of reducing or 
removing the polarization of a voltaic cell 
or battery. (See Cell, Voltaic, Polarization 
of) 

Depolarize. — To deprive of polarization. 

Depolarizing. — Depriving of polarization. 

Depolarizing Fluid. — (See Fluid, De- 
polarizing) 



Dep. 



156 



LDev, 



Deposit, Black, Electro-Metallurgical 

— — — A crystalline variety of electro- 
metallurgical deposit, (See Deposit, Electro- 
Metallurgical?) 

Deposit, Crystalline, Electro-Metallurgi- 
cal A non-adherent, non-coherent 

film of electrolytically deposited metal. (See 
Deposit, Electro-Metallurgical?) 

Deposit, Electro-Metallurgical 

The deposit of metal obtained by any electro- 
metallurgical process. 

To obtain a good metallic deposit the density 
of the current must be regulated according to the 
strength of the metallic solution employed. 

Electro -metallurgical deposits are either — 

(i.) Reguline, or flexible, adherent and strongly 
coherent metallic films, deposited when neither 
the current nor the solution is too strong; or, 

(2.) Crystalline; or non-adherent and non-co- 
herent deposits. 

The crystalline deposit may either be of a loose, 
sandy character, which is thrown down when too 
feeble a current is used with too strong a metallic 
solution, or it may consist of a black deposit, which 
is thrown down when the current is too strong as 
compared with the strength of the solution. This 
latter character of deposit is sometimes technically 
called burning, and takes place most frequently 
at sharp corners and edges, where the current 
density is greatest. (See Current Density.) 

Deposit, Electro-Metallurgical Nodular 

A coherent, irregular electro-metal- 
lurgical deposit which occurs whenever the 
current density falls below its normal value. 
Deposit, Electro-Metallurgical, Keguline 

A flexible, adherent and strongly 

coherent film of metal electrolytically de- 
posited. (See Deposit, Electro-Metalhtr- 
gical.) 

Deposit, Electro-Metallurgical, Sandy 

A non-coherent electro-metallurgical 

deposit which occurs whenever the current 
density exceeds its normal value. 
Depositing Cell.— (See Cell, Depositing.) 
Depositing Tat.— (See Vat, Depositing.) 
Deposition, Electric The deposit- 
ing of a substance, generally a metal, by 
the action of electrolysis. (See Electrolysis.) 



The electric deposition of a metal on any con- 
ducting surface is sometimes called an electro- 
metallurgical deposition. (See Metallurgy^ 
Electro. ) 

Deprez-d'Arsonval Galvanometer.— (See 

Galvanometer, Deprez-d'Arsonval.) 

Derivative Circuit. — (See Circuity De- 
rivative?) 

Derived Circuit.— (See Circuit, Derived.) 

Derived Units. — (See Units, Derived.) 

Destructive Distillation. — (See Distilla- 
tion, Destructive?) 

Detector Galvanometer. — (See Galva- 
nometer, Detector?) 

Detector, Ground In a system 

of incandescent lamp distribution, a device 
placed in the central station, for showing by 
the candle-power of a lamp the approximate 
location of a ground on the system. 

Fig. 196, shows a form of ground-detector, in 




Fig. iqb. Ground-Detector, 

which a small transformer is placed on a board in 
connection with a lamp and a two-way switch. 
One terminal of the primary of the transformer is 
put to ground, while the other can be connected 
by means of the switch to one or the other of the 
two primary mains of the distribution circuit. 
Should an earth exist on either main, then when 
the testing transformer has its pole connected to 
the other main, the lamp in its secondary circuit 
will light up, providing the leak is of sufficient 
magnitude to permit a sufficiently great current 
to pass through the primary circuit. 

Detorsion Bar. — (See Bar, Detorsion.) 
Device, Electro-Receptive Various 



Dev.] 



157 



[Dev, 



devices placed in an electric circuit, and 
energized by the passage through them of the 
-electric current. 

A translating device. 

The following are among the more important 
electro-receptive devices, viz. : 

(i.) Electro magnets. 

(2.) Electric motors. 

(3.) Electro-magnetic signal apparatus. 

(4.) Telegraphic or telephonic apparatus. 

-(5.) An arc or incandescent lamp. 

(6. ) An electric heater. 

(7.) A plating bath or voltameter. 

(8.) An uncharged storage cell. 

(9.) A converter or transformer. 

Electro-Receptive Devices. 
Motion Reproduced. 

(I.) Electric motor. 
(2.) Telpherage system. 
(3.) Telephone receiver. 
(4.) Telegraphic apparatus. 
{5.) Telephote receiver. 

Radiant Energy Produced, 
(6.) Arc or incandescent electric lamp. 
(7.) Electric heater. 
(8. ) Electric welder. 
(9.) Ley den jar or battery. 

Che?nical Decomposition Effected. 
(10.) Electrolytic bath. 
(II.) Uncharged storage battery. 

Electro-Magnetism Produced. 
(12.) Electro-magnet. 
Device, Feeding, of an Arc Lamp 



A device for maintaining the carbon electrodes 
of an arc lamp at a constant distance apart 
during their consumption. (See Lamp, 
Electric Arc) 

Device, Magneto-Receptive . — Any 

-device that is capable of being energized 
when placed in a magnetic field. 

The term magneto-receptive device is used in 
contradistinction to electro-receptive device. (See 
Device^ Electro- Receptive.} 

Device or Arrangement, Electromotive 

A term sometimes employed instead 

of an electnc source. (See Source, Electric, 
Arrangement or Device, Electromotive) 



Device, Safety, for Arc Lamps, or Series 
Circuits Any mechanism which auto- 
matically provides a path for the current 
around a lamp, or other faulty electro-recep- 
tive device in a series circuit, and thus pre- 
vents the opening of the entire circuit on the 
failure of such device to operate. (See La7np, 
Electric Arc) 

Device, Safety, for Multiple Circuits 

— A wire, bar, plate or strip of readily 
fusible metal, capable of conducting, without 
fusing, the current ordinarily employed on the 
circuit, but which fuses and thus breaks the 
circuit on the passage of an abnormally great 
current. 

The terms safety-catch, safety-plug, safety- 
strip and safety -fuse are also used for this safety 
device. (See Euse, Safety.) 

Device, Translating ■ — A term em- 
bracing electro-receptive and magneto-recep- 
tive devices. (See Device, Electro-Recep- 
tive) 

Translating devices are placed in an electric 
circuit, and when traversed by the current effect 
a change, or translation in the form of the electric 
energy whereby useful work is accomplished. 

Translating devices depend for their operation 
on the luminous, heating, magnetic, or chemical 
effects of the current. 

Devices, Electro-Receptive, Multiple- 
Connected ■ — A connection of electro- 
receptive devices, in which the positive poles 
of a number of separate devices are all con- 
nected with a single positive lead or conduc- 
tor, and the negative poles all connected with 
a single negative lead or conductor. 

The multiple-arc-connection of electro-receptive 
devices is suitable for constant potential circuits^ or 
those in which the electromotive force is main- 
tained approximately constant. In such circuits 
the energy absorbed by each device will increase 
as its resistance decreases, since the energy ab- 
sorbed is proportional to the current passing. 
(See Circuits, Varieties of.) 

Multiple-arc- connected electro-receptive devices 
are employed in incandescent lamp distribution. 
Each device added reduces the resistance of ihe 
entire circuit. 



Dev.] 



158 



[Dia* 



DeTices,Electro-Receptiye,Multiple- Arc- 
Connected A term used in place of 

multiple-connected electro-receptive devices. 
(See Devices, Electro-Receptive, Multifile- 
Connected?) 

Devices, Electro-Receptive, Multiple- 
Series-Connected -A connection of 

electro-receptive devices in which a number of 
separate electro-receptive devices are con- 
nected in groups in series, and each of these 
separate groups afterwards connected in mul- 
tiple-arc. 

The multiple-series connection permits electro- 
receptive devices to be placed on mains whose 
electromotive force would be too high to permit 
a single service to be connected directly to them. 
It is of great value in the distribution of incandes- 
cent lamps by constant currents, since by per- 
mitting a higher electromotive force to be em- 
ployed on the main conductors, it reduces the 
dimensions of the conductors required for the 
economical distribution of the current. (See 
Circuits, Varieties of.) 

Devices, Electro-Receptive, Series-Con- 
nected The connection of electro- 
receptive devices in which the devices are 
placed consecutively in the circuit, so that the 
current passes successively through all of 
them from the first to the last. 

The series-connection of electro-receptive de- 
vices is suited to constant-current circuits. The 
work done in the device is developed by the fall 
of potential in each device. This kind of con- 
nection is used in most systems of arc light and 
telegraphic lines. (See Circuits, Varieties of.) 

Devices, Electro-Receptive, Series-Mul- 
tiple-Connected ■ — A connection of 

electro-receptive devices in which a number 
of separate electro-receptive devices are joined 
in separate multiple groups, and each of these 
groups subsequently connected with one an- 
other in series. 

The effect of series-multiple connections is to 
split up the current into a number of separate 
currents of smaller strength, but of the same 
electromotive force. It is applicable to such cases 
as the combination of arc and incandescent lamps 
in the same circuit. (See Circuits, Varieties of .) 

Devices, Translating, Multiple-Con- 



nected A term sometimes used for 

multiple-connected electro-receptive devices. 
(See Devices, Electro-Recefitive, Multifile- 
Connected?) 

Devices, Translating, Multiple- Arc-Con- 
nected ■■ — A term used in place of 

multiple-connected electro-receptive devices. 
(See Devices, Electro-Recefitive, Multifile- 
Connected?) 

Devices, Translating, Multiple-Series- 
Connected ■• — A term sometimes used 

instead of multiple-series-connected electro- 
receptive devices. (See Devices, Electro- 
Recefitive, Multifile-Series-Connected.) 

Devices, Translating, Series-Connected 
A term sometimes used for series- 
connected electro-receptive devices. (See 
Devices, Electro - Receptive, Series - Con- 
nected.) 

Devices, Translating, Series-Multiple- 

Connected A term sometimes used 

for series-multiple-connected electro-recep- 
tive devices. (See Devices, Electro-Recefi- 
tive, Series-Multifile- Connected?) 

Dextrorsal Helix. — (See Helix, Dex- 
trorsal?) 

Dextrorsal Solenoid. — (See Solenoid, Dex- 
trorsal?) 

Diacritical Current. — (See Current, Dia- 
critical?) 

Diacritical Number. — (See Number, Dia- 
critical?) 

Diacritical Point of Magnetic Satura- 
tion. — (See Saturation, Magnetic, Diacrit- 
ical Point of.) 

Diagnosis, Electro. — Diagnosis by means 
of the exaggeration or diminution of the re- 
action of the excitable tissues of the body 
when subjected to the varying influences of 
electric currents. 

The electric current has also been applied in 
order to distinguish between forms of paralysis, 
and as a final test of death. 

Diagnostic, Electro — Pertaining to 

electro-diagnosis. (See Diagnosis, Electro) 

Diagometer, Rousseau's —An ap- 
paratus in which an attempt is made to 



Dia.] 



159 



[D.a. 



determine the chemical composition and con- 
sequent purity of certain substances by their 
electrical conducting powers. 

The arrangement of the apparatus is shown in 
Fig 197. A dry pile. A, has its negative, or — 




Fig. IQ7- Rousseau's Diagometer. 

terminal, m', grounded. Its positive, or -\- ter- 
minal is connected to a delicately supported, and 
slightly magnetized needle, M, terminated by a 
conducting plate, L. Opposite L, and at the same 
height, is a fixed plate of slightly larger size. The 
needle M, when at rest in the plane of the magnetic 
meridian, is in contact at L, with the fixed plate. 
If, therefore, the upper plate of the pile is con- 
nected with the needle M, both plates are similarly 
charged and repulsion takes place, the needle 
coming to rest at a certain distance from the fixed 
plate. 

The substance whose purity is to be determined 
is placed i-n the cup G, which is connected, 
through L, with the fixed plate, A branch wire 
from the -\- terminal of the pile is then dipped into 
the substance in G, and its purity determined 
from the length of time required for the two plates 
at L, to be discharged through the material in G. 

It is claimed that the instrument will detect the 
difference between pure coffee and chicory. Its 
practical application, however, is very doubtful. 

Diagram, Thermo Electric —A 

•diagram in which the thermo-electric power 
between different metals is designated for 
different temperatures. 

The differences of potential, produced by the 
mere contact of two metals, varies, not only with 
the kind of metals, and the physical state of each 
metal, but also with their temperature. This 
difference of potential, maintained in conse- 
quence of the difference of temperature between 
the junctions of a thermo-electric couple, is ap- 
proximately proportional to the differences of 
temperature of these junctions, if these differences 
are not great, and is equal to the product of such 



differences of temperature and a number dependent 
on the metals in the couple. This number is 
called the thermo-electric power. (See Couple^ 
Ther?no-Electric. Thermo-Electric Poiver. ) 
In Fig. 198 (after Tait), the thermo-electric 

0°c 50°i 100°c 1500c 2<XPc 2o0°c 300°c 350°c 400°c 450"c 



J 


























Lead 






A' 








B 


_Copper_ 
















V5^ 








B' 










A 












^" 



















563>5 



Fig. iq8. Theruto-Electric Diagram. 
power is shown between lead and iron, and lead 
and copper. The numbers at the top of the table 
represent degrees of the centigrade thermometer. 
Those at the sides represent the differences of 
potential m micro -volts. 

The thermo-electric power of the copper-iron 
couple decreases from the freezing point of water, 
O degrees C, to a temperature of 274.5 degrees 
C, when it becomes zero. Beyond that temper- 
ature the thermo-electric power increases, but in 
the opposite direction. The point at which this 
occurs is called the neutral point. 

Dial Telegraph. — (See Telegraphy, Dial.) 

Dialysis. — The act of separating a mixture 
of crystalloids and colloids by diffusion 
through a membrane. 

If, for example, the contents of a stomach, in a 
case of suspected poisoning, be placed in a vessel, 
the bottom of which is formed of a sheet of 
parchment paper and floated in water, the 
crystalloid or substances capable of crystalliz- 
ing, will pass into the water and the colloid, an 
uncrystallized jelly-like substance, will remain in 
the vessel. This process has been used to detect 
the presence of poison in the stomach in post- 
mortem cases. 

Diamagnetic. — The property possessed by 
substances like bismuth, phosphorus, anti- 
mony, zinc and numerous others, of being 
apparently repelled when placed between the 
poles of powerful magnets 

When diamagnetic substances in the form of 
rods or bars are placed, as m Fig. 199, between 
the poles of a powerful electro-magnet, they 
place themselves at right angles to the poles, or 
are apparently repelled. 

Paramagnetic substances like iron or steel, on 
the contrary, come to rest under similar circum- 



Dia.] 



160 



[Dia. 




Fig. igg Effect of Para- 
magnetism, 



stances in a straight line joining the poles, at 
right angles to the position shown in Fig. 199. 

Paramagnetic substances are sometimes called 
ferro-magnetic, or substances magnetic after the 
manner of iron. This word is unnecessary and 
ill-advised. The term sidero-magnetic, which has 
also been proposed in place of paramagne.ic, is 
also unnecessary. 

Paramagnetic substances appear to concentrate 
the lines of magnetic force on them; that is, their 
magnetic resistance is 
smaller than that of the 
air or other medium in 
which the magnet is 
placed. They, there- 
fore, come to rest with 
their greatest dimen - 
sions in the direction of 
the lines of magnetic 
force. 

Diamagnetic sub- 
stances appear to have 
a greater magnetic re- 
sistance than that of 
the air around them. 
They, therefore, come 
to rest with their least 
dimensions in the direction of the lines of mag- 
netic force. 

The difference between paramagnetic and dia- 
magnetic substances is generally believed to be 
due to the varying resistance these substances 
thus offer to lines of magnetic force as compared 
with that offered by air or by a vacuum. 

Tyndall comes to the conclusion as the result of 
extended experimentation: il That the diamag- 
netic force is a polar force, the polarity of dia- 
magnetic bodies being opposed to that of para- 
magnetic ones under the same conditions of 
excitement." 

This view, however, is not generally accepted 
by scientists, 

Diamagnetism is also possessed by certain liquid 
and gaseous substances. 

Diamagnetic Polarity. — (See Polarity, 
Diamagnetic?) 

Diamagnetically. — In a diamagnetic man- 
ner, 

Diamagnetism. — A term applied to the 
magnetism of diamagnetic bodies. (See Dia- 
magnetic?) 



Diamagnetism, Weber's Theory of • 

—A theory to account for the phenomena, 
of diamagnetism. 

Weber's theory of diamagnetism, like Ampere's 
theory of magnetism, supposes that magnetic 
substances consist of originally magnetized mole- 
cules or atoms, and that the act of magnetization 
consists of polarizing these atoms or molecules, 
or turning them in one and the same direction. 
That the original condition of the molecules or 
atoms is probably due to the passage of electricity, 
which continually circulates through their mass,, 
the atoms being supposed to possess perfect con- 
ductivity. 

Suppose the substance through whose mole- 
cules or atoms these currents are flowing be 
immersed in a magnetic field. All of the mole- 
cules or atoms which can turn so as to look along 
lines of force in the right direction will have the 
current flowing in them thereby weakened so long 
as they remain in the field. When drawn out of" 
it, however, these currents will regain their nor- 
mal strength. 

Suppose now the case of a substance, in which 
the currents are normal but weak, immersed in a 
strong magnetic field. There may thereby be 
effected a complete reversal of the direction of 
these currents, and others may be produced 
which flow in the opposite direction, and which 
will continue so to flow as long as the substance 
remains in the field. Such currents would then 
be sufficient to explain the phenomena of diamag- 
netic action. 

An electric current produced in a circuit near 
which a momentary current of electricity is sud • 
denly brought has now the opposite direction to 
that which produces it, and this momentary cur- 
rent would tend to produce repulsion. When r 




Fig. 200. Weber's Theory of Diamagnetism. 
too, the circuit is drawn out of the neighborhood 
in which another current is flowing, another mo- 



Dia.] 



161 



[Die. 



mentary current is produced in. the same direc- 
tion. This produces attraction. 

Now, regarding the same phenomena from the 
standpoint of lines of magnetic force, when a 
conductor through which a current is passing is 
placed in a magnetic field, any increase in the 
number of lines of magnetic force passing through 
it tends to move the conductor out of the magnetic 
field, while any decrease in the number of lines 
of force tends to move the conductor into the 
field, To experimentally show the attractions 
and repulsions produced by magnetization or 
demagnetization, the following apparatus may be 
employed : 

A stout disc of copper, Fig. 200, is supported 
on a horizontal arm in the position shown in front 
of the pole of a powerful electro-magnet. When 
the current is sent through the electro- magnet the 
disc of copper is repelled from the magnetic pole. 
When the magnetism is being destroyed by the 
opening of the circuit and by the weakening of 
the current, the copper disc is attracted. 

Diamagnetometer. — An apparatus de- 
signed for studying diamagnetism. (See Dia- 
magnetism. ) 

The apparatus for the study of paramagnetism 
generally receives simply the name of magnet- 
ometer. 

Diamagnets. — Diamagnetic substances 
subjected to magnetic induction and formerly 
called diamagnets in contradistinction to or- 
dinary magnets. 

Diamagnets are supposed by some to possess a 
polarity the same as that of the inducing pole, 
instead of the opposite polarity, as in paramagnetic 
substances. (See Diamagnetism.') 

Diaphragm. — A sheet of some solid sub- 
stance, generally elastic in character and cir- 
cular in shape, securely fixed at its edges and 
capable of being set into vibration. 

The receiving diaphragm of a telephone is 
generally a thin plate or disc of iron, fixed at its 
edges, placed near a magnet pole and set into 
vibration by variations in the magnetic strength 
of the pole, due to variations in the current that 
is passed over the line. 

The transmitting diaphragm of the telephone 
or of a phonograph, consists of a plate fixed at its 
edges and set into vibration by the sound waves 
striking it. 



Diaphragm. — A term sometimes employed 
for a plate form of porous cell. 

Diaphragm Currents.— (See Currents, 
Diaphragm. Cell, Porous) 

Diaphragm of Voltaic Cell.— A term 
sometimes used for the porous cell of a 
double fluid voltaic cell when in the form of 
a plate. 

Dice-Box Insulator. — (See Insulator, 
Dice-Box.) 

Dielectric. — A substance which permits 
induction to take place through its mass. 

This word is sometimes, but improperly, writ- 
ten Di-Electric. 

The substance which separates the opposite 
coatings of a condenser is called the dielectric. 
All dielectrics are non-conductors. 

All non-conductors or insulators are dielectrics, 
but their dielectric power is not exactly propor- 
tional to their non-conducting power. 

Substances differ greatly in the degree or ex- 
tent to which they permit induction to take place 
through or across them. Thus, a certain amount 
of inductive action takes place between the insu- 
lated metal plates of a condenser across the layer 
of air between them. 

A dielectric may be regarded as pervious to 
rapidly reversed periodic currents, but opaque to 
continuous currents. There is, however, some 
conduction of continuous currents. 

According to Swinburne, there are three species 
of conduction that may take place in dielectrics, 
all of which produce a heating of the dielectric, 
viz.: 

(I.) Metallic Conduction, i. e., such a conduc- 
tion as takes place in a metal. This kind of con- 
duction arises from the presence of metallic par- 
ticles embedded in the dielectric. 

(2.) Disruptive Conduction, or a momentary 
current accompanying a disruptive discharge. 

(3.) Electrolytic Conduction, or that kind of 
conduction which accompanies the electrolysis 
of a conductor. This kind of conduction may 
take place in some kinds of glass. 

Faraday regarded the dielectric as the true seat 
of electric phenomena. Conducting substances 
he considered as mere breaks in the continuity of 
the dielectric. This is the view now generally 
held. 

Dielectric Capacity.— (See Capacity, Di- 
electric^) 



Die. 



162 



[Dim, 



Dielectric Constant. — (See Constant, 
Dielectric?) 
Dielectric Density of a Gas. — (See Gas, 

Dielectric Density of.) 
Dielectric, Polarization of — A 

molecular strain produced in the dielectric of a 
Leyden jar or other condenser by the attrac- 
tion of the electric charges on its opposite 
faces, or by the electrostatic stress. (See 
Strain, Dielectric.) 

A term formerly employed in place of 
electric displacement. 

Faraday, in his study of the action of induction, 
in denying the possibility of action at a distance, 
thought that the dielectric through which induc- 
tion takes place was polarized, and that in this 
way the induction was transmitted across the 
intervening space between the inducing and the 
induced body, by the action of the contiguous 
particles of the dielectric. 

The polarization of the glass of a Leyden jar, 
and the accompanying strain, are seen by the 
frequent piercing of the glass, and by the 
residual charge of the jar. (See Charge, Resid- 
ual.) 

Dielectric Resistance.— (See Resistance, 
Dielectric) 

Dielectric Strain. — (See Strain, Dielec- 
tric?) 

Dielectric Strength of a Gas.— (See Gas, 
Dielectric Strength of.) 

Dielectric Stress.— (See Stress, Dielec- 
tric.) 

Difference of Potential.— (See Potential, 
Difference of.) 

Differential Electric Bell.— (See Bell, 
Differential Electric?) 

Differential Galvanometer. — (See Gal- 
vano7neter, Differential?) 

Differential Inductometer.— (See Induc- 
tometer, Differential) 

Differential Method of Duplex Teleg- 
raphy. — (See Telegraphy, Duplex,, Differ- 
ential Method of.) 

Differential Relay.— (See Relay, Differ- 
ential) 

Differential Thermo-Pile.— (See Pile, 
Thermo, Differential) 



Differential Voltameter.— (See Voltam- 
eter, Siemens' Differential) 

Differentially Wound Motor. — (See 
Motor, Differentially Wound.) 

Diffusion, Anodal A term applied 

to the introduction of any drug into the human 
body by electricity. 

The cataphoretic introduction of drugs 
into the body. (See Cataphoresis.) 

A sponge or other similar electrode, saturated 
with a solution of the drug, is connected with 
the anode of a source and placed over the part 
to be treated and its kathode connected to 
another part of the body in a nearly direct line 
with the anode and the current passed, 

Diffusion Creep. — (See Creep Diffusion) 

Diffusion of Electric Current— (See 

Current, Diffusion of) 

Diffusion of Lines of Force.— (See Force. 
Lines of Diffusion of) 

Dimensions of Acceleration.— (See Ac* 

c deration. Dimensions of) 

Dimensions of Units — (See Units, Dimen- 
sions of) 

Diminished Electric Irritability. — (See 

Irritability , Electric, Diminished) 

Dimmer A choking coil, employed 

in a system of distribution by converters or 

transformers, for regulating the potential of 

the feeders. 

The dimmer consists essentially of a choking 

coil wound around a laminated ring of soft iron, 




Fig. 20 T. Reaction Coil Dimmer. 

and provided with an envelope of heavy copper. 
The copper ring, by its position as regards the 
choking coil, adjusts or regulates the self-induc- 
tion of the coil, and consequently regulates the 
potential of the feeders. The dimmer is used in 
theatres or similar situations to turn the lights up 
or down. 



Dio.] 



163 



[Dip. 



The reaction coil or dimmer is shown in Fig. 
201. The choking coil is wound on a ring of 
iron. The copper sheath is furnished with a 
handle to permit its position to be readily 
changed with respect to the coil of insulated wire. 
A laminated iron drum is supported on bearings 
inside the ring. When the sheath is over the 
coil, the coil offers but a small resistance to the 
passage of the current. When away from it the 
self-induction of the coil is increased. 

Dioptre. — A unit of refracting power. 

A lens of one dioptre has a focal length of 
one metre. One of two dioptres has a focal 
length of 50 centimetres; one of four dioptres 
25 centimetres. This is also spelled dioptry. 

Dioptric. — Relating to dioptrics. 
Dioptrics. — The science which treats of 
the refraction of light. 

Dioptry. — A word sometimes used for di- 
optre. (See Dioptre?) 

Dip, Magnetic The deviation of a 

magnetic needle from a true horizontal posi- 
tion. 

The inclination of the magnetic needle to- 
wards the earth. 

The magnetic needle shown in Fig. 202, though 




202. Angle 0/ Dip. 



supported at its centre of gravity, will not retain 
a horizontal position in all places on the earth's 
surface. 



In the northern hemisphere its north-seeking 
end will dip or incline at an angle B O C, called 
the angle of dip. In the southern hemisphere 
its south seeking end will dip. 

The cause of the dip is the unequal distance of 
the magnetic poles of the earth from the poles of 
the needle. 

The magnetic equator is a circle passing 
around the earth midway (in intensity) between 
the earth's magnetic poles. There is no dip at 
the magnetic equator. At either magnetic pole 
the angle of dip is 90 degrees. 

Dip, or Inclination, Angle of 

The angle which a magnetic needle, free to 
move in both a vertical and a horizontal plane, 
makes with a horizontal line passing through 
its point of support. 

The angle of dip of a magnetic needle. 
(See Inclination, A?igle of.) 

Diplex Telegraphy. — (See Telegraphy, 
Diplex.) 

Dipping. — An electro-metallurgical process 
whereby a deposit or thin coating of metal 
is obtained on the surface of another metal 
by dipping it in a readily decomposable 
metallic salt. 

Cleansing surfaces for electro-plating pro- 
cesses by immersing them in various acid 
liquors. 

Dipping, Bright Dipping in acid 

liquors for the purpose of obtaining a bright 
electro-metallurgical coating. 

Dipping Circle. — (See Circle, Dipping?) 

Dipping, Dead Dipping in acid 

liquors for the purpose of obtaining a dead or 
unpolished surface on an electro-metallurgical 
coating. 

Dipping, Electro-Metallurgical 

A process for obtaining an electro-metallur- 
gical deposit on a metallic surface by dipping 
it in a solution of a readily decomposable 
metallic salt. 

A bright, polished iron surface, when simply 
dipped into a solution of copper-sulphate, re- 
ceives a coating of metallic copper from the elec- 
trolytic action thus set up. 

This process is known technically as dipping. 
The term dipping is also used in electro metal- 
lurgy to indicate the process of cleaning the 



Din] 



164 



[Dis. 



articles, that are to be electro-plated, by dipping 
them in various acid or alkaline baths. 

Direct Current. — (See Current, Direct) 
Direct-Current Electric Motor. — (See 
Motor, Electric, Direct-Current) 

Direct Electromotive Force. — (See Force, 
Electrojnotive, Direct?) 

Direct Excitation. — (See Excitation, 
DirectX) 

Direct-Induced Current. — (See Current, 
Direct-Induced?) 

Direct, or Break-Induced Current 

— (See Current, Direct. Current, Break- 
Induced.) 
Direct Working. — (See Working, Direct) 
Direction, Negative, of Electrical Con- 
vection of Heat A direction in which 

heat is transmitted through an unequally 
heated conductor by electric convection, 
during the passage of electricity through the 
conductor, opposite that of the current. (See 
Heat, Electric Convection of.) 

Direction of Lines of Force. — (See Force, 
Lines of, Direction of.) 

Direction, Positive, of Electrical Con- 
vection of Heat A direction in 

which heat is transmitted through an un- 
equally heated conductor by electric convec- 
tion, during the passage of electricity through 
the conductor, the same as that of the cur- 
rent. (See Heat, Electric Convection of) 
Direction, Positive, Bound a Circuit 

In a plane circuit looked at from 

one side, a direction opposite to that of the 
hands of a clock. 

This is a convention which has been made in 

order to conveniently connect the direction of the 

electromotive force produced by induction, with 

the direction of the induction. 

Direction, Positive, Through a Circuit 

In a plane circuit, looked at from 

one side, a direction through the circuit away 
from the observer. 

Directive Tendency of Magnetic Needle. 
■ — (See Needle, Magnetic, Directive Ten- 
dency of) 
Disc, Ara^o's A disc of copper 



or other non-magnetic metallic substance, 
which, when rapidly rotated under a mag- 
netic needle, supported independently of the 
disc, causes the needle to be deflected in the 
direction of rotation, and, when the velocity 
of the disc is sufficiently great, to rotate with it. 
Such disc is shown in Fig. 203 at b. The move- 




Fig. 203. Arago s Disc. 

ment of the needle is due to electric currents, in- 1 
duced by the disc moving through the field of the 
needle so as to cut its lines of magnetic force. To 
obtain the best results the disc must move very 
rapidly, and should be near the needle. More- 
over, the needle should be powerful. 

This effect was discovered by Arago, in 1824. 
Since a magnetic needle moving over a metallic 
plate produces electric currents in a direction 
which tends to stop the motion of the needle, a 
damping of the motion of a magnetic needle is 
sometimes effected by causing it to move near a 
metal plate. The induced currents, which the 
needle produces in the plate by its motion over it, 
tend to retard the motion of the needle. (See 
Damping. Law, Lenz's.) 

Disc Armature. — (See Armature, Disc) 

Disc, Faraday's A metallic disc 

movable in a magnetic field on an axis 
parallel to the direction of the field. 

Such a disc is shown in Fig. 204, and moves, 



03*- 




Fig. 204. Faraday's Disc. 

as will be seen, so as to cut the lines of magnetic 
force at right angles. 

The difference of potential generated by the 
motion of such a disc may be caused to produce 
a current, by providing a circuit which is com- 
pleted through the portion of the disc that at any 



His.] 



165 



[Dis. 



moment of its rotation is situated between spring 
contacts resting on the axis of rotation and the 
circumference of the disc, respectively. 

In Barlow s or Sturgeon' 's wheel, Fig. 205, the 




Fig. 205. Barlow's Wheel. 

wheel itself rotates in the direction shown, when 
a current is sent through it in a direction indicated 
by the arrows. 

Discharge. — The equalization of the dif- 
ference of potential between the terminals of 
a condenser or source, on their connection by 
a conductor. 

The removal of a charge from the surface 
of any charged conductor by connecting it 
with the earth, or another conductor. 

The removal of a charge by means of a 
stream of electrified air particles. 

The discharge of an insulated conductor, a 
cloud, a condenser, or a Leyden battery, is oscil- 
latory. The oscillatory currents continue but for 
a short time. The discharge is therefore often 
spoken of as producing momentary currents. 

The discharge of a voltaic battery, or a stor- 
age battery, is nearly continuous, and furnishes a 
current which is practically continuous, as dis- 
tinguished from the momentary currents produced 
by the discharge of a condenser. 

A discharge may be alternating, brush, brush 
and spray, conductive, convective, dead-beat, 
disruptive, fla7iiing, glow, lateral, oscillatory, 
periodic, stratified, streaming, impulsive and 
periodic. 

Discharge, Alternating An elec- 
tric discharge which changes its direction at 
regular intervals of time. 

A periodic discharge. 

Discharge, Brush — A faintly lu- 
minous discharge that occurs from a pointed 
positive conductor. 

The brush discharge is a species of convective 
discharge. In it, the streams of electrified air 
particles assume the characteristic brush shape. 
(See Discharge, Convective.) 



Discharge, Brush-and-Spray — A 

form of streaming discharge obtained by in- 
creasing the frequency of the alternations 
of a high potential current which assumes 
the appearance of a spray of silver-white 
sparks, or a bunch of thin silvery threads 
around a powerful brush. 

Some idea of the brush-and-spray discharge 
may be obtained from Fig. 206, taken from 




Fig. 206. Brush- and- Spray Discharge ( Testa). 

Tesla, who has carefully studied these phenom- 
ena. 

The brush-and-spray discharge is best obtained, 
according to Tesla, by bringing the terminals 
of a source of rapidly alternating electrostatic 
currents of high potential somewhat nearer to- 
gether, when the streaming discharge has been 
obtained, and preferably increasing the frequency 
of the alternations. 

The brush-and-spray discharge, when power- 
ful, closely resembles a gas flame from gas escap- 
ing under great pressure. Says Tesla: "But 
they do not only resemble, they are veritable 
flames, for they are hot. Certainly they are not 
as hot as a gas-burner, but they would be so if the 
frequency and the potential would be sufficiently 
high:' 

The brush-and-spray discharge, at higher fre- 
quencies, passes into a form of discharge for which 
Tesla has proposed no particular name. He de- 
scribes this form, in a publication of a lecture 
before the American Institute of Electrical Engi- 
neers, as follows, viz.: 

' ' If the frequency is still more increased, then 
the coil refuses to give any spark unless at com- 
paratively small distances, and the fifth typical 
form of discharge may be observed (Fig. 207). 
The tendency to stream out and dissipate is then 
so great that when the brush is produced at one 
terminal no sparking occurs, even if, as I have re- 
peatedly tried, the hand, or any conducting ob- 
ject, is held within the stream ; and, what is more 



Dis.] 



166 



[Dis. 



singular, the luminous stream is not at all easily 
deflected by the approach of a conducting body. 

"At this stage the streams seemingly pass with 
the greatest freedom through considerable thick- 
nesses of insulators, and it is particularly interest- 
ing to study their behavior. For this purpose it 
is convenient to connect to the terminals of the 
coil two metallic spheres, which may be placed at 
any desired distance (Fig. 208). Spheres are pref- 




ix 207. Fifth, Typical Form of Discharge ( Tesla). 

erable to plates, as the discharge can be better 
observed. By inserting dielectric bodies between 
the spheres, beautiful discharge phenomena may 
be observed. If the spheres be quite close and a 
spark be playing between them, by interposing a 
thin plate of ebonite between the spheres the 
spark instantly ceases and the discharge spreads 
into an intensely luminous circle several inches in 
diameter, provided the spheres are sufficiently 
large. The pas age of the stream heats, and, 
after a while, softxis the rubber so much that two 




Fig. 208. Lwninons Discharge with Interposed 
Insulators. 

plates may be made to stick together in this man- 
ner. If the spheres are so far apart that no spark 
occurs, even if they are far beyond the striking 
distance, by inserting a thick plate of glass the 
discharge is instantly induced to pass from the 
spheres to the glass in the form of luminous 
streams. It appears almost as though these 



streams pass through the dielectric. In reality 
this is not the case, as the streams are due to the 
molecules of the air which are violently agitated 
in the space between the oppositely charged sur- 
faces of the spheres. 

'" When no dielectric other than air is present, 
the bombardment goes on, but is too weak to 
be visible ; by inserting a dielectric the induc- 
tive effjct is much increased, and besides, the 
projected air molecules find an obstacle and the 
bombardment becomes so i.itense that the streams 
become luminous. If by any mechanical means 
we could effect such a violent agitation of the 
molecules we could produce the same phenom- 
enon. A jet of air escaping through a small 
hole under enormous pressure and striking 
against an insulating substance, such as glass, 
may be luminous in the dark, and it might be 
possible to produce phosphorescence of the glass 
or other insulators in this manner. 

" The greater the specific inductive capacity of 
the interpose 1 dielectric, the more powerful the 
effect pi oduccd. Owing to this the streams show 
themselves with excessively high potentials even 
if the glass be as much as one and one-half to two 
inches thick. But besides the heating due to bom- 
bardment, some heating goes on undoubtedly in 
the dielectric, being apparently greater in glass 
than in ebonite. I attribute this to the greater 
specific inductive capacity of the glass in conse- 
quence of which, with the same potential differ- 
ence, a greater amount of energy is taken up in it 
than in rubber. It is like connecting to a battery 
a copper and a brass wipe of the same dimen- 
sions. The copper wire, though a more perfect 
conductor, would heat more by reason of its tak- 
ing more current. Thus what is otherwise con- 
sidered a virtue of the glass is here a defect. 
Glass usually gives way much quicker than ebo- 
nite ; when it is heated to a certain degree the 
discharge suddenly breaks through at one point, 
assuming then the ordinary form of an arc." 

Discharge, Conductive — A dis- 
charge effected by leading the charge off 
through a conductor placed in contact with 
the charged body. 

Discharge, Connective — A dis- 
charge which occurs from the points on the 
surface of a highly charged conductor, 
through the repulsion by the conductor of air 
particles that in this manner carry off minute 
charges. 



Dis.] 



167 



[Dis. 



A convective discharge, though often attended 
"by a feeble sound, is sometimes called a silent 
discharge, in order to distinguish it from the 
noisy, disruptive discharge, which is attended by 
a sharp snap, or when considerable, by a loud 
report. 

A convective discharge is also called a glow or 
brush discharge. The latter is best seen at the 
small button at the end of the prime or positive 
conductor of a factional electric machine. 

The positive discharge from a point or small 
rounded conductor is always 'brush -shaped; the 
negative discharge is always star shaped. 

In rarefied gases, the discharge is convective in 
character and produces various luminous effects 
of great beauty, the color of which depends on 
the kind of gas, and the size, shape and material 
of the electrodes, and on the degree of the vacuum. 
Thus in the rarefied 
space of the vessel shown 
in Fig. 209, the discharge 
becomes an ovoidal mass 
of light, sometimes called 
the Philosopher' s Egg. 

When the discharges 
in rarefied gases follow 
one another very rapid- 
ly, alternations of light j 
and darkness, or stratifi- 
cations, or stria are pro- 
duced. 

The breadth of the 
dark bands increases as 
the vacuum becomes 
higher. The light por- 
tions start at the positive 
electrode, and are hotter 
than the dark portions. 

The effects of luminous 
convective discharges are 
best seen in exhausted gUss tubes, called Geissler 
tubes, containing residual atmospheres of various 
gases. (See Tubes, Geissler.') 

Discharge, Dpad-Beat — A non- 
oscillatory discharge. (See Discharge, 
Oscillatory?) 

Discharge, Disruptive A sudden, 

and more or less complete, discharge that 
takes place across an intervening non-con- 
ductor or dielectric. 

A mechanical strain of the dielectric occurs, 
which suddenly breaks down as it were and per- 




20Q. Discharge in 
Rarefied Air. 



mits the discharge to pass as a spark, or rapid 
succession of sparks. 

In air, the spark, when long, generally takes 
the zigzag path, as shown in Fig. 210. 

The sparks produced by disruptive discharges 
consist of healed gases, 
together with portions of 
the conductor that are 
volatilized by the heat. 

The discharge of a Ley- 
denjar or condenser may 
be disruptive, as when 
the discharging rod is 
held with one knob con- 
nected with one coating, 
and the other near the 
other coating. It may 
be gradual, as when the 
two coatings are alter- 
nately connected with the 
ground. The discharge 
of a Leyden jar as, in- 
deed, the disruptive dis- 
charge in general, is os- 
cillatory. 

The stress is often suf- 
ficient to pierce the glass. 

Discharge, Dura- 
tion of The 

time required to effect a complete disruptive 
discharge. 

The disruptive discharge is not instantaneous; 
some time is required to effect it. Estimates of 
the duration of a flash of lightning based on the 
duration of a Leyden jar discharge, are mislead- 
ing from the enormous difference in the quantity 
and the potential in the two cases. The fact that 
the disruptive discharge is oscillatory and consists 
of a number of discharges taking place in alter- 
nately opposite directions shows that the discharge 
is not instantaneous. 

Leyden jar discharges, are, however, accom- 
plished in very small periods of time. 

Discharge, Flaming — The white 

and flaming arc-like discharge that occurs 
between the terminals of the secondary of an 
induction coil, when, with a great number of 
alternations per second, the current through 
the primary is increased beyond that required 
for the sensitive-thread discharge. (See Dis- 
charge, Sensitive- Thread.) 




Fig. 2 to. Disruptive 
Discharge. 



Pis.] 



168 



[Dis. 



According to Tesla the flaming discharge is 
best produced when the number of alternations is 
not too great and certain re ations between ca- 
pacity, self-induction and frequency are observed. 
These relations must be such as will permit the 
flow through the circuit of the maximum current, 
and thus may be obtained with wide variations in 
the frequency. The flaming discharge develops 
considerable heat, and is characterized by the 
absence of the shrill note accompanying less pow- 
erful discharges. This is probably due to the 
enormous frequency. 

Some idea of the flaming discharge may be had 




Fig. 211. Flaming Discharge (Tesla). 

from an inspection of Fig. 211, taken from Tesla. 

Discharge, Glow A form of con- 

vective discharge. (See Discharge, Con- 
vective^) 

Discharge, Impulsiye A dis- 
charge produced in conductors by suddenly 
created differences of potential. 

Impulsive discharges are influenced more by the 
inductance of a conductor than by its true ohmic 
resistance. (See Inductance. Resistance, Ohmic. ) 

A mass of guncotton simply ignited in the 
open air, produces but little effect on any resisting 
object placed below it. If, however, it be rapidly 
ignited by means of a detonator, and is thus fired 
with much greater rapidity, it may shatter any- 
thing placed beneath it. 

In a similar manner, a rapidly discharged cur- 
rent, or impulsive discharge, produces, through the 
inductance of the conductor, a series of effects 
somewhat similar to the above, in which a great 
impedance is produced by a sudden change of 
direction. 

Discharge, Induced Currents, Effects 

Produced by — Varying classes of 

effects produced by the discharges of induced 
currents. 



The effects produced by discharges of induced 
currents are classified by Fleming as follows: 

(1.) Effects depending on the entire quantity of 
the discharge. 

a. Galvanometric effects. 

If the needle of the galvanometer has a period 
or time of oscillation that is long, as compared 
with the time of duration of the discharge, the sine 
of one-half the angle of deflection is proportional 
to the whole quantity of the discharge. 

b. Electro-chemical effects. 

The quantity of an electrolyte broken up is 
proportional to the quantity of electricity which 
passes through it. 

(2.) Effects depending on the average of the 
square of the current strength at any instant dur- 
ing the discharge. 

a. Heating effects. 

The rate of dissipation as heat, according to 
Joule's law, is proportional to the square of the 
current strength passing. 

b. Electro-dynamic effects. 

When a discharge passes through a circuit, 
part of which is fixed and part movable, the forces 
of attraction and repulsion which take place be- 
tween them at any instant are proportional to 
the square of the current strength. 

(3.) Effects depending on rate of change of 
the current. 

a. Physiological effects. 

The effect of the discharge m. producing physi- 
ological shock increases with the suddenness of 
the discharge. Of two discharges which reached 
the same maxima that which reached it first would 
produce the greatest physiological effect. Recent 
investigations by Tesla and others would appear to 
partly disprove the above statement. 

b. Telephonic effects. 

The telephone, like the body of an animal, is 
affected more by the rate of change than by the 
current strength at any instant. 

c. Magnetic effects. 

Rayleigh has shown that the magnetic effects of 
the discharge depend upon the maximum current 
strength during the discharge, or upon the initial 
current strength, in cases where the current dies 
away gradually. Since the time required for the 
permanent magnetizing of a steel wire is small 
compared with the duration of the induced cur- 
rent, the amount of magnetism acquired depends 
essentially on the initial or maximum current 
strength during the discharge, irrespective of the 
time during which said discharge lasts. 



Dis.] 



169 



[Dis. 



d. Luminous effects. 

These are also dependent in the case of induced 
discharges on the rate of change of the current. 

Discharge-Key. — (See Key, Discharge) 

Discharge, Lateral A discharge, 

taking place on the discharge of a Leyden jar, 
or other disruptive discharge, between parts 
of the jar or conductors, not in the circuit of 
the main discharge. 

If a charged Leyden jar is placed on an insulat- 
ing stool, and is then discharged by the discharg- 
ing rod, the lateral discharge is seen as a small 
spark that passes between the outside coating of 
the jar and a body connected with the earth at 
the moment of the discharge through the rod. 

A lateral discharge is also seen in the sparks 
that can be taken from a conductor in good con- 
nection with the earth, by holding the hand near 
the conductor, while it is receiving large sparks 
from a powerful machine in operation. These 
discharges are due to induction. 

If a Leyden jar be discharged by means of a con- 
ducting wire bent as shown in Fig. 212, in which 




Fig. 212. 

two parts of the circuit are closely approached as at 
A, whenever a spark occurs at B, another spark 
produced by a lateral discharge occurs at A. 
Although the resistance of the metallic circuit is 
enormously less than the resistance of the air 
space through which the lateral discharge occurs, 
yet the counter electromotive force produced in 
the metallic circuit by the impulsive discharge, 
renders its resistance far greater than that of 
the air space. The path of a lateral discharge 
is called the alternative path. (See Path, Al- 
ternative. ) 

Discharge, Luminous Effects of — 



The luminous phenomena attending and pro- 
duced by an electric discharge. 

The luminous effects vary as to color, intensity, 
shape and accompanying acoustic phenomena 
according to a variety of circumstances, the prin- 
cipal of which are as follows, viz. : 

(1.) With the kind of gaseous medium through 
which the discharge passes. Thus, a spark passed 
through hydrogen has a crimson or reddish color; 



through carbonic acid or chlorine, a greenish 
color. 

(2.) With the density of the medium. In a 
partial vacuum, the discharge from an induction 
coil becomes an ovoidal mass of light. As the 
vacuum increases, the light at first grows brighter, 
but as a higher vacuum is reached, striae of al- 
ternate dark and light bands appear. Finally, 
with very high vacua the discharge fails to pass. 
(See Discharge, Convective.) 

(3.) With the nature of the substances forming 
the points from which the discharge is taken. 
This is due to the partial volatilization of the ma- 
terial of the electrodes. 

(4.) With the kind of electricity, i. <?., whether 
positive or negative. A positive charge assumes 
the shape of a fan; a negative discharge, that of 
a star. 

(5.) On the density of the discharge. The in- 
troduction of a Leyden jar or condenser in the 
circuit of a Holtz machine, for example, causes 
the spark to change from, the faint bluish to the 
silvery white. 

(6.) The disruptive discharge through air is at- 
tended by snapping or crackling sound, which, in 
the case of lightning, reaches the intensity of thun- 
der. When the disruptive discharge takes place 
through a vacuum a faint hissing sound is heard, 
or all sound may entirely disappear. 

(7.) Luminous effects resulting from molecular 
bombardment occurring in comparatively high 
vacua. These luminous effects may result : 

(a.) From actual incandescence of some refrac- 
tory material produced by the blows of the mole- 
cules; or, 

(b.) As a result of phosphorescence or fluores- 
cence due to such blows. 

Canary glass, or glass stained by uranium oxide, 
fluoresces and emits a yellowish green light; solu- 
tion of sulphate of quinine emits a bluish light. 

Discharge, Non-Oscillatory — A 

dead-beat discharge. (See Discharge, Dead' 
Beat) 



Discharge, Oscillating 



-A number 



of successive discharges and recharges which 
occur on the disruptive discharge of a Leyden 
jar, or condenser. 

A discharge which periodically decreases 
by a series of oscillations. 

A discharge which produces a dying-away- 
backwards and forwards current. 



Dis.] 



170 



[Dis. 



The disruptive discharge of. a Leyden jar, or 
condenser, is not effected by a single rush of elec- 
tricity. When discharged through a compara- 
tively small resistance, a number of alternate 
partial discharges and recharges occur, which 
produce true oscillations or undulalory discharges. 

These oscillations are caused by the induction 
of the discharge on itself, and are similar to the 
self-induction of a current. 

The existence of the oscillating discharge in the 
case of a Leyden jar or condenser, proves, in the 
opinion of some, that electricity, taken along 
with matter, possesses a property similar to 
inertia. 

Discharge, Oscillatory A term 

sometimes used for an oscillating discharge. 
(See Discharge, Oscillating.) 

Discharge, Periodic — An electric 

discharge which changes its direction at reg- 
ular intervals or periods. 

An alternating discharge. 

Discharge, Periodically-Decreasing- 

— An oscillating discharge whose decrease is 
periodic. (See Discharge, Oscillating) 

Discharge, Sensitive-Thread The 

thin, thread-like discharge that occurs be- 
tween the terminals of the secondarv of an in- 
duction coil of high frequency. 

The sensitive-thread discharge occurs, accord- 
ing to Tesla, when the number of alternations per 




Fig. 2 13. Sensitive- Thread Discharge ( Tesla). 

second is high and the current through the 
primary small. This discharge has the form of 
a thin, feebly -colored thread. Though very sensi- 
tive, being deflected by a mere breath, it is never- 
theless quite persistent, if the terminals be at 
one-third of the striking distance apart. Tesla 
ascribes its extreme sensitiveness, when long, to 
the motion of suspended dust particles in the air. 
The general appearance of the sensitive-thread 
discharge is shown in Fig. 213, taken from Tesla. 



Discharge, Silent A name given 

to a convective discharge in order to distin- 
guish it from the more noisy disruptive dis- 
charge. 

The convective discharge in reality is attended 
by a feeble sound, which, however, is quiet when 
compared with the more pronounced sound of the 
disruptive discharge. (See Discharge, Convec- 
tive.) 

Discharge, Stratified The form 

of alternate light and dark spaces assumed by 
the discharges of an induction coil through a 
partially exhausted gas. (See Tube, Strati- 
fication') 

The striae are explained by Curtis as follows: 
" Under the influence of the electric rhythm of 
the rapidly following discharges the molecules 
of the residual gas collect in alternately dense 
and rarefied spaces. The light bands correspond to 
the spaces where the molecules are comparatively 
crowded together, and their concomitant friction 
produces the luminous disturbance. The dark 
spaces are where the molecules are further apart, 
and where their collisions are consequently less 
frequent. ' ' 

Discharge, Streaming A form as- 
sumed by the flaming discharge between the 
terminals of the secondary of an induction 
coil when the frequency of the alternations 
increases beyond a certain limit, and the 
potential has consequently increased. 

The streaming discharge partakes of the general 
characteristics of the flaming discharge. Lumi- 
nous streams pass in abundance, not only between 
the terminals of the secondary, but, according to 
Tesla, who has carefully studied these phe- 
nomena, between the primary and the second ary, 
through the insulating dielectric separating 




Fig. 214. Streaming Discharge {Tesla). 

them. The streams not only pass between the 
terminals, but also issue from all points and pro- 



Dis. 



171 



[Dis. 



jections, as will be seen from Fig. 214, taken from 
Tesla. 

When the streaming discharge reaches a cer- 
tain higher limit it becomes a brush-and spray 
discharge. (See Discharge, Brush- and- Spray.) 

The streaming discharge obtained from an in- 
duction coil with high frequencies differs from that 
of an electrostatic machine in that it neither pos- 
sesses the violet color of the positive static dis- 
charge nor the brightness of the negative, but is 
intermediate in color. 

Discharge, Surging A term some- 
times applied to an oscillatory discharge. (See 
Discharge, Oscillatory^) 

Discharge, to Electrically — To 

equalize differences of potential by connecting 
them by means of a conductor. 

Discharge, Undulatory — A dis- 
charge, the strength and direction of which 
gradually change. (See Currents, Undu- 
latory^) 

Discharge, Unidirectional — An 

electric discharge which takes place from the 
beginning to the end, in one and the same di- 
rection. 

Discharge, Telocity of The time 

required for the passage of a discharge 
through a given length of conductor. 

According to modern views it is the ether sur- 
rounding the wire or conductor which conveys 
the electric pulses. All the energy which gets into 
the conductor is dissipated as heat. 

The velocity of propagation of discharge of the 
pulses produced by the oscillating discharge of a 
Leyden jar through the interatomic or inter- 
molecular ether, i.e., through the fixed ether within 
different substances, varies with the substance. 
Through free ether the velocity is that of light, or 
185,000 miles a second. 

The velocity of discharge through long con- 
ductors or cables is much lessened by ^Cae capacity 
of the cable, and the effects of induction, and will 
therefore vary in different cases. (See Retard- 
ation.) 

Discharger, Universal An appa- 
ratus for sending the discharge of a powerful 
Leyden battery or condenser in any desired 
direction. 

The universal discharger consists essentially of 



metallic rods, supported on insulated pillars and 
capable of ready motion, both towards and from 
one another, as well as in vertical and horizon- 
tal planes. The object which is to receive the 
discharge is placed on an insulated table between 
the rods, and the latter connected with the 
opposite coatings of the battery or condenser, 
when the discharge passes through it. 

The term universal discharger is sometimes ap- 
plied to the discharging tongs. 

Discharging, Electrically — The 

act of equalizing differences of potential by 
connection with a conductor. 

Discharging Kod. — (See Rod, Discharg- 
ing.) 

Discharging Tongs. — (See Tongs, Dis- 
charging.) 

Disconnect. — To break or open an electric 
circuit. 

Disconnecter. — A key or other device for 
opening or breaking a circuit. 

Disconnecting. — The act of opening or 
breaking an electric circuit. 

Disconnection. — A term employed to des- 
ignate one of the varieties of faults caused 
by the accidental breaking or disconnection 
of a circuit. 

Disconnections of this kind may be : 

(1.) Total ; as by a switch inadvertently left 
open; or by the accidental breaking of a part of 
the circuit. 

(2.) Partial; as by a dirty contact; a loose, or 
badly soldered joint; a poorly clamped binding 
screw; a loose terminal, or a bad earth. 

(3.) Intermittent; as by swinging joints, alter- 
nate expansions or contractions on changes of 
temperature; the collection of dust and dirt in dry 
weather, and their washing out in wet weather. 

Disconnection, Intermittent — 

Any fault in a line which occurs at intervals 
or intermittently. 

Disconnection, Partial A partial 

fault in a line caused by any imperfect con- 
tact. 



Disconnection, Total 



-A fault in 



a line occasioned by a complete break in the 
circuit. 

Disguised Electricity.— (See Electricity, 
Disguised.) 



Dis.] 



172 



[Dis. 



Disjunctor. — A device employed in a sys- 
tem for the distribution of electric energy by 
means of continuous currents by condensers, 
for the purpose of periodically reversing the 
constant current sent over the line. (See 
Electricity, Distribution of, by Continuous 
Current by Means of Condensers) 

Dispersion Photometer. — (See Photome- 
ter, Dispersion) 

Displacement Current. — (See Current, 
Displacement) 

Displacement, Electric A displace- 
ment of electricity in a uniform and non- 
crystalline dielectric when lines of electro- 
static or magnetic force pass through it. 

The quantity of electricity displaced in any 
homogeneous, non-crystallizable dielectric, 
by the action of an electric force through 
the unit area of cross-section, taken perpen- 
dicular to the direction of the electric force. 

Electric displacement is produced under an 
elastic strain, which continues only while the elec- 
tric force is acting. 

Displacement, Electric, Lines of 

Lines of electric induction along which elec- 
tric displacement takes place. 

Displacement, Electric, Oscillatory 

— A displacement of electricity in a di- 
electric or non-conductor of an oscillatory 
character. 

Displacement, Electric, Theory of 

— A theory which regards the electricity 
produced on an insulated conductor, by in- 
duction through a dielectric, as displaced out 
of the dielectric on to the conductor, or into 
the dielectric from the conductor, by the in- 
fluence of the electric force. 

This conception was introduced into science by 
Maxwell, after a careful study of Faraday's denial 
of action at a distance. 

Suppose a small insulated sphere to receive a 
charge of electricity + Q. It will, by induction, 
produce an equal and opposite charge — Q, on 
the inner surface, and a similar charge on the 
' outer surface of the small hollow sphere, placed 
near it, but separated by the dielectric. There 
has, therefore, been a displacement of electricity 
through the dielectric. The medium of the 



dielectric has connected the two bodies, and the 
phenomena have appeared by the action of the 
electric force on the substance of the dielectric; 
or, in other words, there has been no action at 
a distance. 

According to this conception, an electric cur- 
rent, called a displacement current, exists in the 
dielectric, while displacement is taking place. 

Displacement Waves. — (See Waves, Dis- 
placement) 

Disruptive Electric Conduction. — (See 
Conductioii, Electric, Disruptive) 

Dissimulated or Latent Electricity. — 

(See Electricity, Dissimulated or Latent) 
Dissipation of Charge. — (See Charge \ 

Dissipatio7i of) 

Dissipation of Energy. — (See Energy, 

Dissipation of) 

Dissipation of Energy, Hysteresial 

— (See Energy, Hysteresial, Dissipation of. 
Hysteresis) 

Dissipation, Specific Hysteresial 

The specific loss of energy by hysteresis in 
the case of a particular substance. (See 
Hysteresis) 

Dissociate. — To separate a compound sub- 
stance into its constituents. 

Dissociation. — The separation of a chemi- 
cal compound into its constituent parts. 

Dissymmetrical Induction of Armature. 

— (See Armature, Dissymmetrical Induc- 
tion of) 

Dissymmetrical Magnetic Field. — (See 
Field, Magnetic, Dissymmetrical) 

Dissymmetry of Commutation. — (See 
Com?nutation, Dissymmetry of) 

Distance, Critical, of Lateral Discharge 

Through an Alternative Path The 

distance at which a discharge will take place 
through an air space of given dimensions, in 
preference to passing through a metallic cir- 
cuit of comparatively small resistance. 

Distance, Explosive — A term some- 
times employed for sparking distance. (See 
Distance, Sparking.) 

Distance, Sparking — The distance 



Dis.] 



173 



[Dot. 



at which electrical sparks will pass through 
an intervening air space. (See Spark, Length 

¥■) 

Distant Station. — (See Station, Distant.) 

Distillation, Destructive — The 

action of heat on an organic substance, 
while out of contact with air, resulting in the 
decomposition of the substance into simpler 
and more stablecompounds. 

The different products resulting from destruc- 
tive distillation may be successively collected by 
the ordinary processes of distillation. 

Distillation, Dry A species of de- 
structive distillation. (See Distillatio?i, De- 
structive.) 

Distillation, Electric The dis- 
tillation of a liquid in which the effects of 
heat are aided by an electrification of the 
liquid. 

Beccaria discovered that a liquid evaporates more 
rapidly when electrified than when unelectrified. 
Crookes has shown that evaporation is aided 
by negative electrification, or that evaporation 
takes place more rapidly at the negative terminal 
during a discharge than at the positive. (See 
Evaporation, Electric. ) 

Distributing Box of Conduit. — (See Box, 
Distributing, of Conduit) 

Distributing Station. — (See Station, Dis- 
tributing) 

Distributing 1 Switch for Electric Light. 

— (See Switch, Distributing, for Electric 
Eights) 

Distribution-Box for Arc Light Circuits. 

— (See Box, Distributio?i, for Arc Light 
Circuits) 

Distribution, Centre of In a sys- 
tem of multiple-distribution, any place where 
branch cut-outs and switches are located in 
order to control communication therewith. 

The electrical centre of a system of distri- 
bution as regards the conducting network. 

Distribution of Charge.— (See Charge, 
Distributio?i of) 

Distribution of Electricity. — (See Elec- 
tricity, Distribution of) 



Distribution of Electricity by Alternat- 
ing" Currents (See Electricity, Dis- 
tribution of, by Alternating Currents) 

Distribution of Electricity by Alternat- 
ing Currents by Means of Condensers. — 
(See Electricity, Distribution of, by Alter- 
nating Currents by Means of Condensers) 

Distribution of Electricity by Conimu- 
tating Transformers. — (See Electricity, 
Distribution of, by Commutating Trans- 
formers) 

Distribution of Electricity by Constant 
Potential Circuit. — (See Electricity, Multi- 
ple Distribution of, by Constant Potential 
Circuit) 

Distribution of Electricity by Contin- 
uous Current by Means of Transformers. — 
(See Electricity, Distribution of, by Contin- 
uous Current by Means of Transformers.) 

Distribution of Electricity by Motor- 
Generators.— (See Electricity, Distribution 
of, by Motor-Generators) 

Distribution, Series, of Electricity by 
Constant Current Circuit. — (See Electricity, 
Series Distribution of, by Constant Current 
Circuit) 

District Call-Box. — (See Box, District 
Call) 

Diurnal Inequality of Earth's Magnet- 
ism. — (See Inequality, Diurnal, of Earth's 
Magnetisjn) 

Divided Magnetic Circuit. — (See Circuit, 
Divided Magnetic) 

Door-Opener, Electric — A device 

for opening a door from a distance by elec- 
tricity. 

Various devices consisting of electro-magnets, 
acting against, or controlling springs or weights, 
are employed for this purpose. 

Dosage, Electro-Therapeutical 

The apportioning of the amount of the cur- 
rent and the duration of its application to the 
body for the treatment of disease. 

Dosage, Galvanic —Electro-thera- 
peutical dosage. (See Dosage, Electro- 
Therapeutical) . 

Dotting Contact.— (See Contact, Dotting.) 



Dou, 



m 



. TDro. 



D o u b 1 e-Break Knife Switch.— (See 

Switch, Double-Break Knifed 

Double-Carbon Arc Lamp. — (See Lamp, 
Electric Arc, Double-Carbon?) 

Double-Cone Insulator. — (See Insulator, 
Double-Cone?) 

Double- Connector. — (See Connector, 
Double?) 

Double-Contact Key.— (See Key, Double- 
Contact?) 

Double-Cup Insulator. — (See Insulator, 
Double-Cup?) 

Double-Curb. — (See Curb, Double.) 

Double-Curb Signaling-.— (See Signaling, 
Curb, Double?) 

Double-Current Signaling.— (See Signal- 
ing, Double-Current ) 

Double-Current Translator.— (See Trans- 
lator, Double-Current?) 

Double-Curr ent Transmitter. — (See 
Transmitter, Double-Current?) 

Double-Current Working —The 

employment, in systems of telegraphy, by 
means of suitable keys, of currents from 
voltaic batteries, in alternately opposite 
directions, thus increasing the speed of 
signaling. (See Working, Reverse-Current?) 

Double-Fluid Electrical Hypothesis. — 
(See Electricity, Double-Fluid Hypothesis 
of) 

Double-Fluid Voltaic Cell.— (See Cell, 
Voltaic, Double-Fluid?) 

Double-Magnet Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Double-Magnet?) 

Double-Pen Telegraphic Register. — (See 
Register, Double-Pen, Telegraphic) 

D o u b 1 e-Refraction. — (See Refraction, 
Double?) 

Double-Refraction, Electric— (See Re- 
fraction, Double, Electric) 

Double-Shackle Insulator. — (See Insula- 
tor, Double-Shackle) 

Double-Shed Insulator. — (See Insulator, 
Double-Shed) 



Double-Tapper Key.— (See Key, Double- 
Tapper) 
Double-Touch, Magnetization by 

A method for producing magnetization by 
the simultaneous touch of two magnet poles. 
(See Magnetization, Methods of) 

Double-Transmission.— (See Transmis- 
sion, Double) 

Double-Trolley.— (See Trolley, Double) 

Doubler of Electricity. — An early form of 
continuous electrophorus. (See Electro- 
phorus) 

Drifting Torpedo.— (See Torpedo, Drift- 
ing) 

Drill, Electro-Magnetic — A drill 

applied especially to blasting or mining opera- 
tions, operated by means of electricity. 

Drip Loop.— (See Loop, Drip) 

Driven Pulley.— (See Pulley, Driven) 

Driven Shaft. — (See Shaft, Driven) 

Driving Pulley. — (See Pulley, Driving) 

Driving Shaft— (See Shaft, Driving) 

Driving Spider. — (See Spider, Driving?) 

Drop, Annunciator — A movable 

signal operated by an electro-magnet, and 
placed on an annunciator, the dropping of 
which indicates the closing or opening of the 
circuit with which the electro-magnet is con- 
nected. 

The falling of the drop may be attended by the 
sounding of a bell or other alarm, or, it may give 
a silent indication. 

Drop, Annunciator, Automatic A 



drop for an annunciator, which on the closing 
of a circuit, falls and holds the circuit closed 
until the drop is raised. 

Drop, Annunciator, Gravity — A 

drop for an annunciator, acted on by gravity 
when released by the movement of the arma- 
ture of an electro-magnet. 

Drop, Automatic A device for au- 
tomatically closing the circuit of a bell and 
holding it closed until stopped by resetting a 
drop. 



Dro.] 



175 



[Dyn. 




The automatic drop is especially applicable to 
burglar alarms. On the opening of a door or 
shutter, the closing of the circuit moves the 
armature of an elec- 
tro - magnet, and, 
by the falling of a 
drop, closes the cir- 
cuit and holds it 
closed until me- 
chanically opened 
by the replacing of 
the drop. The 
general appearance 
of the automatic 
drop is shown in 
Pig. 215. 

Drop, Calling" 

^ n an _ Fig. 2 is- Automatic Drop. 

nunciator drop employed to indicate to the 
operator in a telegraphic or telephonic system 
that one subscriber wishes to be connected 
with another. 

Drop of Potential. — (See Potential, Drop 

"/■) 

Drops, Clearing" Out ■ — Restoring 

the drops of annunciators to their normal 
position after they have been thrown out of 
the same by the closing of the circuits of their 
magnets. 

These clearing -out devices as placed on most 
forms of annunciators are generally mechanical in 
operation. 

Drum Armature. — (See Armature, 
Drum) 

Drum, Electro-Magnetic —A drum, 

used in feats of legerdemain, operated by 
an automatic electro-magnetic make and 
break apparatus. 

Dry Distillation. — (See Distillation, 
Dry) 

Dry Electrode. — (See Electrode, Dry) 

Dry Pile.— (See Pile, Dry) 

Dry Voltaic Cell.— (See Cell, Voltaic, 
Dry.) 

Dub's Laws.— (See Laws, Dub's) 

Duplex Cable.— (See Cable, Duplex.) 

Duplex Cut-Out.— (See Cut-out, Duplex.) 



Duplex Flat Cable.— (See Cable, Flat 
Duplex.) 

Duplex Telegraphy. — (See Telegraphy, 
Duplex?) 

Duplex Wire. — (See Wire, Duplex) 

Duration of Electric Discharge. — (See 
Discharge, Duration of) 

Duration of Make-Induced Current. — 

(See Current, Make or Break Diduced, Du- 
ration of) 

Dust Figures, Lichtenberg's — 

(See Figures, Lichtenberg's Dust.) 

Dyad. — A chemical element which has two 
bonds by which it can unite or combine with 
another element. 

An element whose atomicity is bivalent. 

Dyeing, Electric The application 

of electricity either to the reduction or the 
oxidation of the salts used in dyeing. 

GoppelsrOder, in his processes of electric dyeing % 
forms and fixes ani'ine black on cloth as follows, 
viz. : the cloth, saturated with an aniline salt, is 
placed on an insulated metallic plate, inert to the 
aniline salt, and connected with one pole of a 
battery or other electric source. The other pole 
is connected with a metallic plate on which the 
required design is drawn. On the passage of the 
current, the design is traced in aniline black on 
the cloth. A minute or two suffices for the 
operation. 

A species of electrolytic writing is obtained on 
cloths arranged as above by substituting a carbon 
1 encil for the metallic plate. On writing with 
this pencil, as with an ordinary pencil, the pas- 
sage of the current so directed is followed by the 
deposition of aniline black. 

By means of a somewhat similar process writ- 
ing in white on a colored ground is obtained. 

Dynamic Electricity. — (See Electricity, 
Dynamic) 

Dynamics, Electro That branch 

of electric science which treats of the action 
of electric currents on one another and on 
themselves or on magnets. 

The principles of electro -dynamics were dis- 
covered by Ampere in 182 1. 

A convenient form of apparatus, for showing 
experimentally the action cf ore current on 
another, consists of two upright metallic columns 



DjnJ 



i:g 



[Byn. 



or pillars, which support horizontal metallic arms 
containing mercury cups, y, and c, -Fig. 216. 




Deflection of a Circuit by a Current. 

The circuit is bent in the form of a rectangle, 
circle or solenoid, and terminates in points that 
dip in the mercury cups. The current is led into 
and out of the apparatus at the points -f- and — 
at the base of the upright supports. 

When a magnet, or another circuit, is ap- 
proached to the movable circuit thus provided, 
attractions or repulsions are produced according 
to th^ position of the magnet, or the direction of 
the currents in the two circuits. 

If a magnet A B, Fig. 217, be placed, as shown, 




Fig. 217. Deflection 0/ Circuit by a Magnet. 

below the movable circuit C C, the circuit will 
tend to place itself at right angles to the axis of 
the magnet. This movement is the same as 
would occur if electric currents were circulating 
around the magnet in the direction cf the assumed 
Amperian currents. It also illustrates the prin- 
ciple of the electric motor. (See Magnetism, Am- 
pere's Theory of.) 

Ampere has given the results of his investigations 
as to the mutual attractions and repulsions of cur- 



rents in the following statements, which are 
known as At?ipere''s Laws : 

(i.) Parallel portions of a circuit attract one 
another if the currents in them are flowing in the 
same direction, and 
repel one another if 
the currents are flow- 
ng in opposite direc- 
tions. 

A current flowing 
through a spiral tends 
to shorten the spiral 
from the attraction of 
the parallel currents in contiguous turns. 

Similar poles of two solenoids repel each other,. 
as at A, A', Fig. 218, because, when opposed to 
each other, the currents that produce these poles- 



A 




Fig. 218. 



Action of Solenoid^ 
Poles. 




Fig. 2iq. Ampere's Stand. 

are flowing in opposite directions, as may be 
seen from an inspection of the drawing. 

Dissimilar solenoid poles, on the contrary, at- 
tract each other as at A, B, in Fig. 218, since 




C 

Fig. 220. Electro- Dynamic Attraction. 

the currents which produce them flow in the same 
direction. 

In Fig. 219, a form of Ampere's stand is shown, 
in which one of the circuits is in the form of the 



Byn.] 



177 



[Dyn. 




coil M N ; its action on the movable circuit C B, 
is to repel it, since the currents, as shown, are 
flowing in an opposite direction in the adjacent 
portions of the fixed and movable circuits. 

(2.) Two portions of a circuit intersecting each 
other mutually attract each other when the cur- 
rents in both circuits flow 
either towards or front 
the point of intersection, 
but repel each other ?°f 
they flow in opposite di- 
rections from this point. 

Thus, in Fig. 220, the 
currents in both circuits 
P Q and A B C D, flow 
towards and from the 
point of intersection Y, and attract one another 
and cause a motion until the two circuits are 
parallel. 

If the currents flow in opposite directions they 
repel each other, and, if free to move, will come 
to rest when parallel to each other ; therefore, 
two portions of a circuit crossing each other tend 
to move until they are parallel, and their currents 
are flowing in the same direction. 

(3.) Successive portions of the circuit of the 
same rectilinear current ', that is, a current flowing 
ia the same straight line, repel one another. 

A circuit O A, Fig. 221, movable on O, as a 



P Q. 

Fig. 221. Continuous 

Rotation of Current. 




Fig, 222. Mutual Action of Magnetic Fields. 

centre, will be continuously rotated in the direc- 
tion of the curved arrow by the rectilinear cur- 
rent, P Q; for, the directions of the currents being 
as shown by the arrows, there will be attraction 
in the positions (1) and (2), and repulsion in po- 
sition (4). 

The cause of the mutual attractions and repul- 
sions of electric circuits will readily appear from 
a consideration of the mutual action of their 
magnetic fields. 

Thus an inspection of Fig. 222 shows : 



(1.) That parallel currents flowing in the same 
direction attract, because their lines of force have 
opposite directions in adjoining parts of the cir- 
cuit of these lines. 

(2.) That parallel currents flowing in opposite 
directions repel, because their lines of force have 
the sa??ie directions in adjoining parts of the cir- 
cuit. 

These laws may therefore be generalized thus, 
viz.: Lines of magnetic force extending, in oppo- 
site directions attract one another ; lines of 
magnetic force extending in the same direction 
repel one another. 

Ampere proved that a circuit, doubled on itself 
so that the current flows in opposite directions in 
the two parts, exerts no force on external objects. 
This expedient is adopted in resistance coils to 
prevent any disturbance of the galvanometer 
needles. He also showed that a sinuous circuit, 
or one bent into zigzags, produces the same effects 
of attraction or repulsion as it would if it were 
straight. (See Coil, Resistance.) 

The term sinuous current is sometimes applied 
to the current in a sinuous circuit. (See Current, 
Sinuous.) This must be distinguished from the 
term sinusoidal current, which applies to fluctua- 
tions in the current and not to peculiarities in the 
shape of the conductor. 

When two inclined magnets, free to move, are 
left to their mutual attractions and repulsions, they 
gradually come to rest with their axes parallel to 
each other. 

Two conductors through which electric cur- 
rents are flowing act on one another as two 
magnets would. 

A conductor conveying a current of electricity 
tends to rotate round a magnetic pole. A mag- 
netic pole tends to rotate continuously round an 
electric current. 

The motion of a magnet near a conductor 
produces an electromotive force in that conductor 
provided the conductor cuts the lines of force. 

A magnetized substance becomes magnetized 
when placed in a magnetic field. 

A conductor through which a current of elec- 
tricity is passing tends to wrap itself around a 
neighboring magnetic pole. The following ex- 
periments illustrate this tendency: 

(1.) The experiment suggested by Lodge: A 
powerful current of electricity is passed through 
some eight feet in length of gold thread such as 
is employed for making lace. The thread is 
hung in a vertical position, near a vertical bar 



Dyn.] 



178 



[Djn. 



magnet. As soon as the current passes, the 
thread will wrap itself around the bar magnet, 
one half of it twisting itself round the north pole, 
the other half round the south pole. 

(2.) The experiment suggested by Professor S. 
P. Thompson: An electric current is sent through 
a stream of mercury while it is flowing between 
two poles of a powerful electro-magnet; when 
the current is sent through the magnet, the 
stream is twisted in spiral directions which vary, 
either with the direction of the current, or with 
the direction of the magnetic polarity. 

(3.) Somewhat similar effects can be shown by 
the rotation of a stream of gas round a magnetic 
pole placed in an exhausted glass receiver. 

Dynamo. — The name frequently applied to 
a dynamo-electric machine used as a gener- 
ator. (See Machine, Dynajno-Electric?) 

Dynamo Balancing Rheostat. — (See 
Rheostat, Dynamo Balancing^) 

Dynamo-Battery. — (See Battery, Dy- 
namo.) 

Dynamo Brush Trimmer. — (See Trim- 
mer, Dynamo Brushy 

Dynamo, Composite-Field — — — A 

dynamo whose field coils are series and 
separately excited. 

Additional separately excited coils placed on 
the field of a series wound dynamo render it self- 
regulating. 

A composite dynamo is a form of compounded 
dynamo. 

Dynamo, Compound-Wound. — A com- 
pound-wound dynamo-electric machine. (See 
Machine, Dynamo-Electric, Comftound- 
WouJid.) 

Dynamo, Contact A form of dyna- 
mo in which the space between the arma- 
ture and field magnet poles is so reduced that 
they actually touch one another. 

In contact dynamos both field and armature 
revolve. This form of dynamo has not been very 
successful in practice. 

Dynamo-Electric Machine. — (See Ma- 
chine, Dynamo-Electric?) 

Dynamo-Electric Machine, Alternating 
Current — (See Machine, Dynamo- 
Electric, Alternating Current.) 



Dynamo-Electric Machine Armature. — 

(See Armature, Dynajno-Electric Machine.) 

Dynamo-Electric Machine Armature 
Coils. — (See Coils, Armature, of Dynamo- 
Electric Machine?) 

Dynamo-Electric Machine Armature 
Core. — (See Core, Armature, of Dynamo- 
Electric Machine?) 

Dynamo-Electric Machine Battery. — 
(See Battery, Dyjiamo-Electric Machine?) 

Dynamo-Electric Machine, Bi-Polar 

— (See Machine, Dynajno-Electric, Bi- 
Polar?) 

Dynamo-Electric Machine, Collecting 

Brushes of (See Brushes, Collecting, 

of Dynamo-Electric Machine?) 

Dynamo-Electric Machine Commutator 

(See Commutator, Dynajno-Electric 

Machine?) 

Dynamo-Electric Machine, Compound- 
Wound — (See Machine, Dynamo- 
Electric, Cojnpoujid- Wound?) 

Dynamo-Electric Machine, Generation of 
Current by (See Currejit, Genera- 
tion of, by Dynajno-Electric Machine?) 

Dynamo-Electric Machine, Field Mag- 
nets (See Magnets, Field, of Dynamo- 
Electric Machine?) 

Dynamo-Electric Machine, Methods of 
Increasing the Electromotive Force Gene- 
rated by (See Force, Electrojnotive, 

Generated by Dyjiajno-Electric Machine, 
Method of Ijicr easing.) 

Dynamo-Electric Machine, Mouse-Mill, 
Sir William Thomson's — (See Ma- 
chine, Dyjiajno-Electric, Mouse-Mill, Sir 
Williajn Thojjzson's.) 

Dynamo-Electric Machine, Multipolar 

(See Machine, Dyjiajno-Electric, 

Multipolar?) 

Dynamo-Electric Machine, Pole-Pieces of 

(See Pole-Pieces of Dynajno-Electric 

Machine?) 

Dynamo-Electric Machine, Reversibility 

of (See Machme, Dynamo-Electric, 

Reversibility of.) 



Djn.] 



179 



[Djn, 



Dynamo-Electric Machine, Varieties of 

—(See Machine, Dynamo-Electric, 

Varieties of.) 

Dynamo, Inductor • A dynamo- 
electric machine for alternating currents in 
which the differences of potential causing the 
currents are obtained by magnetic changes in 
the cores of the armature and field coils by 
the movement past them of laminated masses 
of iron inductors. 

The coils corresponding to the armature and 
field magnets of the ordinary dynamo are sta- 
tionary. The laminated masses of iron, employed 
to cause magnetic changes in the cores of the field 
and armature coils, are fixed on an inductor wheel 
which is rapidly revolved in front of them. The 
magnets corresponding to the field magnets are 
called the primary poles, and are magnetized by 
an exciter. The magnets corresponding to the 
armature are called the secondary poles and are 
placed so as to alternate with the primary poles. 
The inductors are so shaped that they carry the 
magnetism of one pole of the primary magnet 
to the secondary poles when the inductor is in 
one position, and of the opposite pole when in a 
slightly different position. The inductor wheel 
therefore acts as a magnetic commutator and 
changes the position of the secondary magnet as 
it rotates, thus producing electromotive force. 
The number of alternations per revolution is 
equal to twice the number of inductors placed on 
the inductor wheel. 

Dynamo, Inverted A dynamo-elec- 
tric machine in which the armature bore or 
chamber is placed below the field magnet 
coils. 

The term inverted is used in contradistinction 
to the overtype dynamo. (See Dynamo, Over- 
type.) 

Dynamo, Mouse Mill A form of 

dynamo-electric machine designed by Sir 
William Thomson to act as the replenisher of 
one of his electrometers. (See Replenisher?) 

Dynamo, Multiphase A polyphase 

dynamo. (See Dyna7no, Polyphase. Dy?ia- 
mo, Rotating Current?) 

Dynamo, Overtype A dynamo- 
electric machine, the armature bore or cham- 
ber of which is placed above the field magnet 
coils instead of below them as in many forms. 



The overtype form of dynamo possesses the 
advantage of better avoiding magnetic leakage. 

Dynamo, Polyphase A name some- 
times applied to a rotating current dynamo. 
(See Dynamo, Rotating Current?) 

Dynamo, Pyromagnetic ■ A name 

sometimes applied to a pyromagnetic gen- 
erator. (See Generator, Pyromagnetic.) 

Dynamo, Rotary-Phase A term 

sometimes employed for a rotating current 
dynamo. (See Dynamo, Rotating Current.) 

Dynamo, Separately-Excited —A 

separately-excited dynamo-electric machine. 
(See Machine, Dynamo-Electric, Separ- 
ately-Excited?) 

Dynamo, Series A series-wound 

dynamo- electric 
machine. (See Ma- 
chine, Dynamo- 
Electric, Series- 
Wound?) 

Dynamo, Shunt 

■ — A shunt- 
wound dynamo- 
electric machine. 
(See Machine, 
Dynamo - Electric, 
Shunt- Wound?) 

Dynamograph. 

— A term some- 
times applied to a 
type-writing tele- 
graph that records 
the message in 
type-written char- 
acters, both at the 
sending and the 
receiving ends. 

Dynamometer. 
— A name given to 

a variety of appar- F{g , 223 , Parsons' Dyna- 

atus for measuring mometer. 

the power of an engine or motor. 

In all dynamometers the strain on the belt or 
other moving part is measured, say in pounds, 
and the speed of the moving part is also measured 
in feet per second. The product of the strain in 




Dyn.] 



180 



[Dyn. 



pounds by the velocity in feet per second, di- 
vided by 550, will give the horse power. 

One of the many forms of dynamometers is 
shown in Fig. 223. It is known as Parsons' Dy- 
namometer. 

The driving pulley is shown at A, and the 
driven pulley at C. Weights hung at Q 15 are va- 
ried so as to maintain the axes of the suspended 
pulleys, D and B, as nearly as possible at the 
same height. Then the tension T t and T 2 , on 
the sides O and O', of the belts, will be repre- 
sented by the following equation : 

from which, knowing the belt speed, the horse 
power may be deduced. 

There are several other forms of dynamometer, 
such as the cradle dynamometer, in which the 
machine is supported on knife edges and the 
torque or pull exerted on or by the machine is 
balanced by weights sliding on a lever. In these 
dynamometers the power is transmitted through 
them and they are therefore called transmission 
dynamometers. 

Dynamometer, Electro A form of 

galvanometer for the measurement of electric 
currents. 

In Siemens' Electro-Dynamometer, shown in 
Fig. 224, there are two coils ; a fixed coil, C, se- 
cured to an upright support, and a movable coil, 
L, consisting often of but a single turn of wire. 
The movable coil is suspended by means of a 
thread and a delicate spring, S, capable of being 
twisted by turning a milled screw-head through 
an angle of torsion measured on a scale by means 
of an index connected to the screw-head. The 
two ends of the movable coil dip into mercury 
cups so connected that the current to be measured 
passes through the fixed and movable coils in 
series. 

When ready for use the movable coil is at right 
angles to the fixed coil. The current to be meas- 
ured is then sent into the coils, and their mutual 
action tends to place the movable coil parallel to 
the fixed coil against the torsion of the spring, S. 
The amount of this force can be ascertained by 
determining the amount of torsion required to 
bring the movable coil back to its zero position. 



Since the same current passes through both the 
fixed and movable coils, and they both act on 
each other, the deflecting force here is evidently 
proportional to the square of the strength of the 




Fig. 224* Siemens' Electro- Dynamometer, 

current to be measured. The deflecting force, 
and consequently the current strength, is there- 
fore proportional to the square root of the angle 
of torsion, and not directly to the angle of tor- 
sion. 

Dyne. — The unit of force. 

The force which in one second can impart 
a velocity of 1 centimetre per second to a 
mass of 1 gramme. 

The dyne is the unit of force, or a force capa- 
ble, after acting for one second on a mass of I 
gramme, of giving it a velocity of I centimetre 
per second. The weight of a body in dynes , or the 
force with which it gravitates, is equal to its 
mass in grammes, multiplied by the acceleration 
imparted to it in centimetres per second. For 
this latitude the acceleration is about 981 centi- 
metres per second. 



E.J 



181 



[ElI<L 



E. — A contraction sometimes used for 
earth. 

A contraction sometimes used for electro- 
motive force, or E. M. F., as in the well- 
known formula for Ohm's law, 

R 

E. M. D. P.— A contraction for electro- 
motive difference of potential. (See Poten- 
tial, Difference of, Electromotive?) 

E. M. F. — A contraction generally used for 
electromotive force. (See Force, Electro- 
motived) 

Earth. — A fault in a telegraphic or other 
line, caused by accidental contact of the line 
with the ground or earth, or with some con- 
ductor connected with the latter. 

This is more frequently called a ground. 

Earths are of three kinds, viz.: 

(I.) Dead or Total Earth. 

(2.) Partial Earth. 

(3.) Interjnittent Earth. 

The term earth is also applied to a plate buried 
in the ground, and intended to make a good con- 
tact between the earth and a wire circuit, which 
is connected with the plate. 

Earth Circuit. — (See Circuit, Earthy 

Earth-Circuited Conductor. — (See Con- 
ductor, Earth-Circuited?) 

Earth Currents. — Electric currents flow- 
ing through different parts of the earth caused 
by a difference of potential at different points. 

The causes of these differences of potential are 
various and are not well understood. 

Earth, Dead or Total A fault in 

a telegraphic or other line in which the line 
is thoroughly grounded or connected with 
the earth. 

Dead earth is sometimes called total earth. 

Earth-Grounded Wire. — (S e e Wire, 
Earth-Grounded. ) 

Earth, Intermittent A swinging 

earth. (See Earth, Swinging or Intermit- 
tent.) 

Earth or Ground. — That part of the earth 



or ground which forms part of an electric 
circuit. 

A circuit is put to earth or ground when the 
earth is used for a portion of the circuit. 

The resistance of an earth connection may vary 
in time from the following causes, viz. : 

(i.) The corrosion of the ground plate. This is 
especially apt to occur in the case of a copper 
plate. 

(2.) From polarization, a counter- electro- 
motive force being produced, thus introducing a 
spurious resistance into the circuit. (See Resist- 
ance ; Spurious.) 

Earth, Partial A fault in a tele- 
graphic or other line in which the line is in 
partial connection with the earth. 

The term partial earth is used in contradistinc- 
tion to dead or total earth. 

Earth, Return A circuit in which 

the return current passes back to the source 
through the earth. 

Earth, Swinging* or Intermittent 

— A fault in a telegraphic or other line in 
which the action of the wind, or occasional 
expansion by heat, brings the line into inter- 
mittent contact with the earth. 

Earth, Total A term sometimes 

used for dead earth. (See Earth, Dead or 
Total?) 

Ebonite. — A tough, hard, black substance, 
composed of india rubber and sulphur, which 
possesses high powers of insulation and of 
specific inductive capacity. 

Ebonite is often called vulcanite. 

Vulcanite rubbed with cat-skin acts as one of 
the best known substances for becoming electri- 
fied by friction. For this purpose both substances 
should be thoroughly dried. 

Economic Co-efficient of Dynamo-Elec- 
tric Machine — (See Co-efficient, Economic* 
of a Dyna7no-Electric Machine?) 

Eddy Currents. — (See Currents, Eddy.) 

Eddy Currents, Deep-Seated (See 

Currents, Eddy, Deep-Seated?) 

Eidy Currents, Superficial (See 

Currents, Eddy, Superficial?) 



Edd.] 



182 



[Eff. 




225. Electric 
Eeh 



Eddy-Displacement Currents.— (See Cur- 
rents, Eddy- Displacement^) 

Eel, Electric An eel possessing 

the power of giving powerful electric shocks 

The gymnotus electricus. 

The electricity is produced by an organ ex- 
tending the entire length of 
the body. 

According to Faraday, the 
shock given by a specimen 
of the animal examined by 
him was equal to that of 15 
Leyden jars, having a total 
surface of 25 square feet. 
Fig. 225 shows the general 
appearance of the animal. 

Effect, Acheson 

The increase in the electro- 
motive force of the sec- 
ondary of a transformer by 
the action of the changes 
in temperature of its core. 
(See Electricity, Cat) 

Effect, Chemical 

— The effect occasioned by atomic combina- 
tion, which results in a loss of those properties 
or peculiarities by which the substances en- 
tering into combination are ordinarily recog- 
nized. 

Atomic combination, resulting in the for- 
mation of new molecules. 

The formation of new molecules necessitates the 
possession by the new substance of properties dis- 
tinct and separate from those of its constituents. 

Black carbon, and yellow sulphur, for example, 
both solids, unite chemically to form a trans- 
parent colorless liquid. 

Chemical changes differ from physical changes, 
which latter can occur in a substance without the 
formation of new molecules, and consequently 
without the loss by it of the properties it ordi- 
narily possesses. 

Thus a sheet of vulcanite, electrified by friction, 
still retains its characteristic density, shape, color, 
etc. 

Effect, Counter-Inductive — - — The 

cpposal of current or charge by means of a 
counter-electromotive force produced by in- 
duction. 



In the Thomson counter- electromotive force 
lightning arrester, a counter-electromotive force, 
produced by the inductive effects of the passage 
of the bolt to earth, protects the instrument by 
opposing the passage of the bolt. (See Arrester^ 
Lightnings Counter -Electromotive Force. ) 

Effect, Edison • An electric dis- 
charge which occurs between one of the ter- 
minals of the incandescent filament of an 
electric lamp, and a metallic plate placed near 
the filament but disconnected therefrom, as 
soon as a certain difference of potential is 
reached between the lamp terminals. 

The effect of the discharge is to produce a cur- 
rent in a circuit connected to one pole of the lamp 
terminals and the metallic plate, as may be shown 
by means of a galvanometer. 

Effect, Electrotonic —An altered 

condition of excitability of a nerve produced 
when in the electrotonic state. (See Elec- 
trot onus.) 

Effect, Faraday ■ ,— The rotation of 

the plane of polarization of a beam of plane 
polarized light by its passage through a 
magnetic field. 

Lodge suggests the following explanation for 
the Faraday effect : As is well known, a strongly 
magnetized medium possesses a different magnetic 
susceptibility to additional magnetizing forces in 
the same direction than it does in the opposite 
direction. It therefore follows that the vibra- 
tions are resolved into two opposed circular com- 
ponents, which travel through the medium with 
different rates of velocity, since one tends to mag- 
netize it and the other to demagnetize it. The 
plane of rotation will therefore be rotated. 

He also suggests the following explanation for 
the Faraday effect, viz.: He assumes that the 
Amperian molecular currents in such substances 
as exhibit rotation in a magnetic field do not 
consist of two equal and opposite electrical cur- 
rents, but that one of the currents is slightly 
stronger than the other. Suppose, for example, 
that in iron the positive Amperian current is 
weaker than the negative, and that the ether as 
a whole is rotating with the negative current. 
Any ethereal vibration entering such a medium 
will begin to screw itself in the direction opposed 
to that of the magnetizing current. In copper, 
or other similar substances, the rotation should 
take place in the opposite direction. 



EX J 



183 



[Eff. 



Effect, Ferranti 



-An increase in the 



electromotive force, or difference of potential, 
of mains or conductors towards the end of the 
same farthest from the terminals that are con- 
nected with a source of constant potential. 

The Ferranti effect refers to the increase of the 
electromotive force on the mains employed in 
systems for the transmission of electrical energy 
by means of alternating currents. It was found, 
for example, in the currents used on the 
mains connected with one of Mr. Ferranti's alter- 
nating dynamos and leading to the town of Dept- 
ford, that instead of finding a drop of potential at 
the ends of the mains farthest from the dynamo, 
as was expected, a notable increase in the poten- 
tial occurred. These effects were observed dur- 
ing the laying of the mains. Testing the poten- 
tial by placing an incandescent lamp in the circuit 
across the mains, the increase of the potential 
with the increase of the length of the main was 
shown by the increased brilliancy of the light of 
the incandescent lamp. 

Various explanations have been given as the 
cause of the Ferranti effect. 

Effect, Hall A transverse elec- 
tromotive force, produced by a magnetic 
field in substances undergoing electric dis- 
placement. 

This transverse electromotive force is probably 




Fig. 226. Hall Effect. 
due to magnetic whirls, in a manner similar to 
the Faraday effect. 

The Hall effect is produced by placing a very 
thin metallic strip, conveying an electric current, 
in a strong magnetic field. 

The cross A B C D, Fig. 226, is cut out of a 



gold leaf or other very thin metallic sheet. The 
ends A and B, are connected with the terminals 
of a battery S, and . the ends C and D, with the 
galvanometer G. 

None of the battery current can therefore flow 
through the galvanometer. 

If, now, the metallic cross be placed in a power- 
ful magnetic field, the lines of force of which are 
perpendicular to the plane of the cross, the deflec- 
tion of the galvanometer needle will show the 
existence of a current, which, if the battery cur- 
rent flows in the direction of the arrow, or from A, 
to B, and the lines of magnetic force pass through 
the paper from the front to the back of the sheet, 
when the cross is formed of gold, silver, platinum 
or tin-foil, will flow through C D, from C to D, 
but in the opposite direction if formed of iron. 
These effects cease if the conductor is increased 
in thickness beyond a certain extent. 

As regards the production of the Hall effect by 
the influence of a magnetic field on conductors, 
Mr. Shelford Bidwell suggests that since magnet- 
ism affects the conductivity of metals in a 
complicated manner, it is possible that metallic 
substances conveying an electric current in a 
magnetic field are more or less strained by the 
mechanical forces, and that, therefore, heat may 
be unequally developed, and that the resistance 
thus being modified in places, there may be pro- 
duced disturbances of the flow which may 
rapidly produce in part a transverse electromotive 
force. 

Effect, Hall, Real A transverse elec- 
tromotive force produced in conductors con- 
veying electric currents, by magnetic whirls, 
in a manner similar to that in which the Far- 
aday effect is produced. (See Effect, Fara- 
day.) 

Effect, Hall, Spurious An appa- 
rent transverse electromotive force produced 
in conductors conveying electric currents in 
magnetic fields, by changes, produced by mag- 
netism, in the conductivity of the metals, and 
the consequent production of local distur- 
bances in the electrical flow, thus resulting 
in an apparent transverse electromotive force. 

Effect, Impulsion The restoration 

or loss of sensitiveness of a photo-voltaic cell 
to the action of light, produced by means of 
an impulse such as that of a tap or blow, or 
electro-magnetic impulse. 



Eff.J 



184 



[Eff. 



Effect, Joule ■ —The heating effect 

produced by the passage of an electric cur- 
rent through a conductor, arising merely from 
the resistance of the conductor. 

The rate at which this occurs is proportional to 
the resistance of the conductor through which 
the current is passing multiplied by the square 
of the current. (See Heat, Electric.) 

Effect, Kerr ■ — A term applied to 

the electrostatic optical effect discovered by 
Dr. Kerr, viz., that a beam of plane polarized 
light is elliptically polarized when transmitted 
across an electrostatic field. 

The Kerr effect does not take place in free space, 
but occurs in different senses or directions in dif- 
ferent media. 

Like the Faraday effect, the Kerr effect de- 
pends on the presence of a dense medium, and the 
direction of the effect depends on the character of 
the medium. 

Effect, Mordey — A term some- 
times applied to a decrease in the value of 
hysteresis in the iron of a dynamo armature at 
full load. 

Effect, Peltier The heating ef- 
fect produced by the passage of an electric 
current across a thermo-electric junction or 
surface of contact between two different met- 
als. (See Junction, Thermo-Electric.) 

The passage of the current across a thermo- 
electric junction produces either heat or cold. If • 
heat is produced by its passage in one direction, 
cold is produced by its passage in the opposite 
direction. The Peltier effect may, therefore, 
mask the Joule effect. 

The Peltier effect is the converse of the thermo- 
electric effect, where the unequal heating of metal- 
tic junctions results in an electric current. (See 
Effect, Joule. Effect, Thomson.) 

The quantity of heat absorbed or emitted by 
the Peltier effect is proportional to the current 
strength, and not, as in the Joule effect, to the 
square of the current. 

Effect, Plioto-Yoltaic The change 

in the resistance of selenium or other 
substances effected by their exposure to 
light. The photo-voltaic effect is seen in 
the case of the selenium cell. (See Cell, 
Selenium.) 



Effect, Seebeck 



-A term sometimes 



used instead of thermo-electric effect. (See 
Effect, Thermo-Electric.) 

This term has nearly passed out of use. 

Effect, Skin The tendency of alter- 
nating currents to avoid the central portions 
of solid conductors and to flow or pass mostly 
through the superficial portions. 

The so-called skin effect is more pronounced 
the more frequent the alternations. 

Effect, Thermo-Electric The pro- 
duction of an electromotive force at a 
thermo-electric junction by a difference of 
temperature between that junction and the 
other junction of the thermo-electric couple. 
(See Couple, Thermo-Electric. Junction, 
Thermo-Electric.) 

Effect, Thomson — The production of 

an electromotive force in unequally heated 
homogeneous conducting substances. 

A term also applied to the increase or de- 
crease in the differences of temperature in an 
unequally heated conductor, produced by the 
passage of an electrical current through the 
conductor. 

The Thomson effects vary according to whether 
the current passes from a colder to a hotter part 
of the conductor, or the reverse. 

The Thomson effects differ in direction in differ- 
ent metals, and are absent in lead. Thomson has 
pointed out the similarity between this species of 
thermo-electric phenomena, and convection by 
heat, or the phenomena of a liquid circulating in 
a closed rectangular tube, under the influence of 
differences of temperature, in which the heated 
Jluid gives out heat in the cooler parts of the cir- 
cuit, and takes in heat in the warmer parts. 
This would presuppose that positive electricity 
carries heat in copper like a real fluid, but that 
in iron it ac^s as though its specific heat were a 
negative quantity, in which respect it is unlike a 
true fluid. 

" We may express," says Maxwell, " both the 
Peltier and the Thomson effects by stating that 
when an electric current is flowing from places of 
smaller ^o places of greater thermo-electric power, 
heat is absorbed, and when it is flowing in the 
reverse direction heat is generated, and this 
whether the difference of thermo-electric power 
in the two places arises from a difference in the 



Eff.] 



185 



[Ele. 



nature of the metals, or from a difference of tem- 
perature in the same metal." 

Effect, Toltaic A difference of 

potential observed at the point of contact of 
two dissimilar metals. 

This difference of potential was formerly as- 
cribed to the mere contact of dissimilar metals, 
and is even yet believed by some to b * due to 
such contact. It is, however, perhaps more ac^ 
curately ascribed to the greater affinity of oxygen 
of the air for the positive metal than for the 
negative metal; that is, to a chemical action on 
the positive element of a voltaic couple. 

Effective Electromotive Force.— (See 
Force, Electromotive, Effective?) 

Effective Secondary Electromotive 
Force. — (See Force, Electromotive, Second- 
ary, Effective?) 

Effects of Capillarity on Toltaic Cells.— 
(See Capillarity, Effects of, on Voltaic Cell?) 

Efficiency, Commercial The useful 

or available energy produced divided by the 
total energy absorbed by any machine or ap- 
paratus. 

The Commercial Efficiency = 
W W 

~M~ ~~ \V -j- w -f- m, 
when W = the useful or available energy ; M = 
the total energy ; w, the energy absorbed by the 
machine, and m, the stray power, or power lost 
in friction of bearings, etc., air friction, eddy cur- 
rents, etc. 

Efficiency, Commercial, of Dynamo 

—The useful or available electrical energy in 
the external circuit, divided by the total 
mechanical energy required to drive the 
dynamo that produced it. (See Co-efficient, 
Economic, of a Dyna?no-Electric Machine?) 

Efficiency, Electric The useful or 

available electrical energy of any source, 
divided by the total electrical energy. 

W 



The electric efficiency 



where W, 



W + w 

equals the useful or available electrical energy, 
and w, the electrical energy absorbed by the 
machine. 

Efficiency of Conversion. — The ratio be- 
tween the energy present in any result and 
the energy expended in producing that result. 



Efficiency of Conversion of Dynamo. — 

(See Conversion, Efficiency of, of Dynamo?) 
Efficiency of Transformer. — (See Trans- 
former, Efficiency of) 

Efficiency, Quantity, of Storage Battery 

— The ratio of the number of ampere- 
hours taken out of a storage or secondary 
battery, to the number of ampere-hours put in 
the battery in charging it. 

Efficiency, Real, of Storage Battery 

— The ratio of the number of watt-hours 
taken out of a storage battery, to the number 
of watt-hours put into the battery in charg- 
ing it. 

Efflorescence. — The drying of crystals by 
losing their water of crystallization and be- 
coming pulverulent or crumbling. 

The term is sometimes loosely applied to 
the deposition of solid matter by the crystal- 
lization of a salt, above the line of the liquid, 
on the surface of a vessel containing a vaporiz- 
able saline solution. 

The liquid, by capillarity in a porous vessel, or 
by adhesion to the walls of an impervious vessel, 
rises above the level of the main liquid line, and, 
evaporating, deposits crystals on the vessel. 

This process is technically called creeping, and 
is often the cause of much annoyance in voltaic 
cells. 

Egg, Philosopher's A name given 

to the ovoidal, or egg-shaped mass of light 
that appears when a convective discharge is 
taken between two electrodes in a partial 
vacuum. 

The philosopher's egg is but one of the shapes 
assumed by the convective discharge. (See Dis- 
charge, Convective. ) 

Elasticity, Electric The quotient 

arising from dividing the electric stress by 
the electric strain. 

It can be shown mathematically that the elec- 
tric elasticity is equal to 4, or 4 x 3.1416, divided 
by the specific inductive capacity. 

Electrepeter. — An instrument for chang- 
ing the direction of an electric current. 

The old term for switch, key, or pole changer. 
(Obsolete.) 

Electric. — Pertaining to electricity. 



Ele.] 



1S6 



[Ele. 



Electric Absorption. — (See Absorption, 
Electric?) 

Electric Acoutemeter. — (See Acouteme- 
ter, Electric?) 

Electric Actinometer. — (See Actinomecer, 
Electric) 

Electric Adhesion. — (See Adhesion, Elec- 
tric?) 

Electric Aging of Alcohol. — (See Alco- 
hol, Electric Aging of) 

Electric Alarm. — (See Alarm, Electric?) 

Electric Alarm Speaking-Tube Mouth- 
Piece. — (See Sneaking-Tube Mouth-Piece, 
Electric Alarm?) 

Electric Amalgam. — (See Amalgam, 
Electric?) 

Electric Ammunition Hoist. — (See Hoist, 
Ammunition, Electric?) 

Electric Analysis. — (See Analysis, Elec- 
tric?) 

Electric Analyzer. — (See Analyzer, Elec- 
tric) 

Electric Anemometer. — (See Anemome- 
ter, Electric?) 

Electric Annealing. — (See Annealing, 
Electric?) 

Electric Annunciator Clock. — (See 
Clock, Electric A?inunciator?) 

Electric Arc. — (See Arc, Electric.) 

Electric Arc Blow-Pipe.— (See Blow- 
Pipe, Electric Arc?) 

Electric Argand Burner, Hand-Lighter 
(See Burner, Argand Electric , Hand- 
Lighter?) 

Electric Argand Burner, Plain-Pendant 

— (See Burner, Argand Electric, 

Plain-Pendant?) 

Electric Argand Burner, Ratchet-Pend- 
ant (See Burner, Argand Electric, 

Patchet-Pendant) 

Electric Balance. — (See Balance, Elec- 
tric?) 

Electric Balloon. — (See Balloon, Elec- 
tric?) 

Electric Battery, — (Gee Battery, Elec- 
tric?) 



Electric Bell, Continuous-Sounding 

— (See Bell, Continuous-Sounding Electric?) 
Electric Bell, Differential.— (See Bell, 

Differential Electric) 
Electric Bell, Mechanical.— (See Bell, 

Electro-Mechanical) 

Electric Bell Pull.— (See Pull, Bell, Elec- 
tric) 

Electric Bioscopy. — (See Bioscopy, Elec- 
tric) 

Electric Bi-Polar Bath.— (See Bath, Bi- 
polar) 

Electric Blasting. — (See Blasting, Elec- 
tric) 

Electric Bleaching. — (See Bleaching, 
Electric) 

Electric Blow-Pipe. — (See Blow-Pipe, 
Electric) 

Electric Boat. — (See Boat, Electric) 
Electric Bobbin. — (See Bobbin, Electric) 
Electric Body-Protector.— (See Body-Pro- 
tector, Electric) 

Electric Boiler-Feed. — (See Boiler-Feed, 
Electric) 

Electric Branding. — (See Branding, Elec- 
tric) 

Electric Breeze. — (See Breeze, Electric) 
Electric Bridge. — (See Bridge, Electric) 
Electric Buoy. — (See Buoy, Electric) 
Electric Burner. — (See Burner, Auto- 
matic Electric) 

Electric Buzzer. — (See Buzzer, Electric) 
Electric Cable.— (See Cable, Electric) 
Electric Calamine. — (See Calamine, Elec- 
tric) 
Electric Call-Bell.— (See Bell, Call) 
Electric Calorimeter. — (See Calorimeter, 
Electric) 

Electric Candle. — (See Candle, Electric) 
Electric Case-Hardening. — (See Case- 
Hardening, Electric) 

Electric Cauterization. — (See Cauteriza- 
tion, Electric) 

Electric Cauterizer. — (See Cauterizer, 
Electric) 



Eie.' 



187 



[Ele. 



Electric Cautery. — (See Cautery, Elec- 
tric^ 

Electric Charge — (See Charge, Electric?) 
Electric Chimes. — (See Chimes, Electric?) 

Electric Chronograph. — (See Chrono- 
graph, Electric?) 

Electric Chronoscope. — (See Chronoscope, 
Electric?) 

Electric Cigar-Lighter. — (See Lighter, 
Cigar, Electric?) 

Electric Circuit. — (See Circuit, Electric?) 

Electric Cleats. — (See Cleats, Electric?) 

Electric Clepsydra. — (See Clepsydra, Elec- 
tric?) 

Electric Clock.— (See Clock, Electric?) 
Electric Coil.— (See Coil, Electric?) 
Electric Column. — (See Column, Elec- 
tric?) 

Electric Communicator.— (See Commu- 
nicator, Electric?) 

Electric Conducting. — (See Conducting, 
Electrical?) 

Electric Conduction.— (See Conduction, 
Electric.) 

Electric Convection of Heat.— (See Heat, 
Electric Convection of) 

Electric Cord.— (See Cord, Electric?) 

Electric Counter. — (See Counter, Elec- 
tric?) 

Electric Creeping. — (See Creeping, Elec- 
tric?) 

Electric Cross. — (See Cross, Electric?) 

Electric Crucible. — (See Crucible, Elec- 
tric?) 

Electric Current. — (See Current, Elec- 
tric?) 

Electric Cystoscopy. — (See Cystoscopy^ 
Electric?) 

Electric Damping. — (See Damping, Elec- 
tric?) 

Electric Death. — (See Death, Electric?) 

Electric Decomposition. — (See Decotn- 
position, Electric?) 



Electric Density. — (See Density, Elec- 
tric?) 

Electric Deposition. — (See Deposition, 
Electric?) 

Electric Determination of Longitude. — 
(See Longitude, Electric Determination 
of-) 

Electric Displacement, — (See Displace- 
ment, Electric?) 

Electric Distillation. — (See Distillation,, 
Electric?) 

Electric Door-Bell Pull.— (See Pull, 
Electric Door-Bell?) 

Electric Double-Refraction. — (See 
Double-Refraction, Electric?) 

Electric Dyeing. — (See Dyeing, Electric?) 

Electric Dynamometer, Siemens'. — (See 
Dy?iamometer, Electro?) 

Electric Eel. — (See Eel, Electric?) 

Electric Efficiency. — (See Efficiency, Elec- 
tric?) 

Electric Elasticity. — (See Elasticity, Elec- 
tric?) 

Electric Elevator. — (See Elevator, Elec- 
tric?) 

Electric Endosmose. — (See E?idosmose, 
Electric?) 

Electric Energy. — (See Energy, Electric?) 

Electric Entropy. — (See Entropy, Elec- 
tric?) 

Electric Escape. — (See Escape, Electric?) 

Electric Etching. — (See Etching, Elec- 
tro?) 

Electric Evaporation. — (See Evapora- 
tion, Electric?) 

Electric Excitability of Nerve or Mus- 
cular Fibre. — (See Excitability, Electric, 
of Nerve or Muscular Fibre?) 

Electric Exhaustion. — (See Exhaustion, 
Electric?) 

Electric Expansion. — (See Expansion, 
Electric?) 

Electric Exploder. — (See Exploder, Elec- 
tric Mine?) 



Ele.] 



188 



[Ele. 



Electric Explorer. — (See Explorer, Elec- 
tric^ 

Electric Field. — (See Field, Electric?) 

Electric Figures, Breath — (See 

Figures, Electric, Breath?) 

Electric Figures, Lichtenberg's 

(See Figures, Electric, Lichtenberg's?) 
Electric Fishes. — (See Fishes, Electric.) 
Electric Fly. — (See Fly, Electric.) 
Electric Flyer. — (See Flyer, Electric?) 
Electric Fog. — (See Fog, Electric) 
Electric Force. — (See Force, Electric?) 
Electric Furnace. — (See Furnace, Elec- 
tric?) 
Electric Fuse. — (See Fuse, Electric?) 
Electric Gas-Lighting. — (See Gas-Light- 
ing, Electric?) 

Electric Gas-Lighting, Multiple 

(See Gas-Lighting, Multiple Electric?) 

Electric Gas-Lighting Torch. — (See 
Torch, Electric Gas-Lighting?) 

Electric Gastroscope. — (See Gastroscope, 
Electric?) 

Electric Gilding. — (See Gilding, Electric?) 
Electric Goyernor. — (See Governor, Elec- 
tric?) 

Electric Hand-Lighter for Argand 
Burner. — (See Burner, Argand Electric 
Hand-Lighter?) 

Electric Head-Bath. — (See Bath, Head, 
Electric?) 

Electric Head-Light. — (See Head-Light, 
Locomotive, Electric?) 

Electric Heat. — (See Heat, Electric?) 
Electric Heater. — (See Heater, Electric?) 
Electric Horse Power. — (See Power, 
Horse, Electric?) 

Electric Hydrotasimeter. — (See Hydro- 
tasimeter, Electric?) 

Electric Ignition. — (See Ignition, Elec- 
tric?) 
Electric Images. — (See Images, Electric?) 
Electric Incandescence. — (See Incandes- 
cence, Electric?) 



Electric Indicator for Steamships. — (See 
Indicator, Electric, for Steamships?) 

Electric Indicators. — (See Indicators, 
Electric?) 

Electric Inertia. — (See Inertia, Electric?) 

Electric Insolation. — (See Insolation, 
Electric?) 

Electric Installation. — (See Installation, 
Electric?) 

Electric Insulation. — (See Insulation, 
Electric?) 

Electric Irritability. — (See Irritability, 
Electric?) 

Electric Jar. — (See Jar, Electric?) 

Electric Jewelry. — (See Jewelry, Elec- 
tric?) 

Electric Lamp, Arc (See La7np, 

Electric. Arc.) 

Electric Lamp-Bracket. — (See Bracket, 
Lamp, Electric?) 

Electric Lamp, Incandescent (See 

La?np, Electric, Incandescent?) 

Electric Lamp, Semi-Incandescent 

— (See Lamp, Electric, Semi-Inca?idescent .) 

Electric Lamp, Socket for. — (See Socket, 
Electric Lamp?) 

Electric Launch. — (See Launch, Elec- 
tric?) 

Electric Letter-Box. — (See Letter-Box, 
Electric?) 

Electric Light. — (See Light, Electric?) 

Electric Lighting, Central Station 

— (See Station, Central?) 

Electric Lighting, Isolated (See 

Lighting, Electric, Isolated?) 

Electric Light or Power Cable. — (See 
Cable, Electric Light or Power?) 

Electric Lock. — (See Lock, Electric?) 

Electric Locomotive. — (See Locomotive, 
Electric?) 

Electric Log. — (See Log, Electric?) 

Electric Loom. — (See Loom, Electric.) 

Electric Loop. — (See Loop, Electric?) 

Electric Machine, Frictional (See 

Machine, Frictional Electric?) 



He.] 



189 



[Eie. 



Electric Main. — (See Main, Electric?) 
Electric Masses. — (See Masses, Electric^ 
Electric Measurements. — (See Measure- 
ments, Electric?) 

Electric Megaloscope. — (See Megalo- 
scope, Electric?) 
Electric Meter. — (See Meter, Electric?) 
Electric Mine-Exploder. — (See Mine-Ex- 
ploder, Electro-Magnetic. Euse, Electric?) 

Electric Motor. — (See Motor, Electric?) 

Electric Motor, High-Speed (See 

Motor, Electric, High-Speed?) 

Electric Motor, Low-Speed (See 

Motor, Electric, Low-Speed?) 

Electric Multipolar Bath (See 

Bath, Multipolar, Electric?) 

Electric Musket. — (See Musket, Electric?) 
Electric Organ. — (See Organ, Electric?) 
Electric Oscillations. — (See Oscillations, 
Electric?) 

Electric Osmose. — (See Osmose, Electric?) 
Electric Osteotome. — (See Osteotome, 
Electric?) 

Electric Overtones.— (See Overtones, 
Electric?) 

Electric Pen. — (See Pen, Electric?) 
Electric Pendant. — (See Pendant, Elec- 
tric.) 

Electric Pendant-Lamps. — (See Lamps, 
Electric Pe?idant.) 

Electric Pendulum. — (See Pendulum, 
Electric?) 

Electric Permeancy. — (See Permeancy, 
Electric?) 

Electric Phosphorescence. — (See Phos- 
phorescence, Electric?) 

Electric Photometer.— (See Photometer?) 
Electric Piano. — (See Piano, Electric?) 
Electric Plow. — (See Plow, Electric?) 
Electric Position-Finder. — (See Finder, 
Position, Electric?) 

Electric Potential. — (See Potential, Elec- 
tric?) 



Electric Power. — (See Power, Electric.) 
Electric Probe. — (See Probe, Electric?) 
Electric Prostration. — (See Prostration, 

Electric?) 

Electric Protection.— (See Protection, 

Electric, of Houses, Ships and Buildings?) 
Electric Protection of Metals. — (See 

Metals, Electrical Protection of) 

Electric Pulse. — (See Pulse, Electrical?) 

Electric Pyrometer, Siemens'. — (See 
Pyrometer, Siemens', Electric.) 

Electric Radiometer, Crookes' 

(See Radiometer, Electric, Crookes'.) 

Electric Range-Finder. — (See Finder, 
Range, Electric?) 

Electric Ratchet-Pendant for Argand 
Burner. — (See Burner, Argand Electric, 
Ratchet-Pendant. ) 

Electric Ray. — (See Ray, Electric.) 

Electric Reaction Wheel. — (See Wheel, 
Reaction, Electric?) 
Electric Rectification of Alcohol. — (See 

Alcohol, Electric Rectification of.) 

Electric Refining of Metals. — (See Metals, 
Electric Refining of.) 

Electric Register, Watchman's 

(See Register, Watchman's Electric?) 

Electric Registering Apparatus. — (See 
Apparatus, Registering, Electric?) 

Electric Relay-Bell.— (See Bell, Relay, 
Electric.) 

Electric Repulsion. — (See Repulsion, 
Electric?) 

Electric Resistance. — (See Resistance, 
Electric.) 

Electric Resonance. — (See Resonance, 
Electric.) 

Electric Retardation.— (See Retardation, 
Electric?) 

Electric Rings. — (See Rings, Electric?) 

Electric Safety Lamps. — (See Lamp, 
Electric Safety.) 

Electric Saw. — (See Saw, Electric?) 



Ele.] 



190 



[Ele. 



Electric Seismograph. — (See Seismo- 
graph, Electric?) 

Electric Shadow. — (See Shadow, Elec- 
tric) 

Electric Shock. — (See Shock, Electric) 

Electric Shower Bath. — (See Bath, 
Shower Electric.) 

Electric Shunt Bell.— (See Bell, Shunt, 
Electric.) 

Electric Single-Stroke Bell.— (See Bell, 
Single-Stroke Electric.) 

Electric Siphon. — (See Siphon, Electric.) 

Electric Soldering. — (See Soldering, 
Electric.) 

Electric Sphygmograph. — (See Sphygmo- 
graph, Electrical) 

Electric Sterilization. — (See Steriliza- 
tion, Electric) 

Electric Storm. — (See Storm, Electric) 

Electric Striae. — (See Strice, Electric) 

Electric Submarine Boat. — (See Boat, 
Sub?narine, Electric.) 

Electric Sunstroke. — (See Sunstroke, 
Electric) 

Electric Surgings. — (See Surging s, Elec- 
tric.) 

Electric Swaging. — (See Swaging, Elec- 
tric.) 

Electric Tanning. — (See Tanning, Elec- 
tric.) 

Electric Target. — (See Target, Electric) 

Electric Teazer. — (See Teazer, Electric 
Current) 

Electric Telehydrobarometer. — (See Tel- 
ehydrobaro7neter, Electric) 

Electric Tell-Tale Signal. — (See Signal, 
Electric Tell-Tale) 

Electric Tempering.^(See Teinpering, 
Electric.) 

Electric Tension. — (See Tension, Elec- 
tric) 

Electric Thermo-Call. — (See Thermo- 
Call, Electric.) 

Electric Thermometer. — (See Thermom- 
eter, Electric) 



Electric Throwback-Indicator. — ( See 

Indicator, Electrical Throwback) 

Electric Time-Ball. — (See Ball, Electric 
Time) 

Electric Time-Meter. — (See Meter, Elec- 
tric Time) 

Electric Torpedo.— (See Torpedo, Elec- 
tric) 

Electric Tower. — (See Tower, Electric) 

Electric Tramway. — (See Tramway. Elec- 
tric) 

Electric Transmitters. — (See Transmit- 
ter, Electric) 

Electric Trumpet. — (See Trumpet, Elec- 
tric) 

Electric Turn-Table.— (See Turn-Table, 
Electric) 

Electric Typewriter.— (See Typewriter^ 
Electric.) 

Electric Yalve. — (See Valve, Electric) 
Electric Yalve Burner, Argand 

(See Valve Burner, Argand Electric^ 

Electric Varnish. — (See Varnish, Elec- 
tric) 

Electric Vibrating Burner. — (See Burner, 
Vibrating, Electric) 

Electric Volatilization. — (See Volatiliza- 
tion, Electric) 

Electric Water or Liquid Level Alarm. — 

(See Alarm, Water or Liquid Level) 

Electric Welding. — (See Welding, Elec- 
tric) 

Electric Whirl.— (See Whirl, Electric) 

Electric Whistle, Automatic Steam 

— (See Whistle, Steam, Automatic Elec- 
tric) 

Electric Wood Mouldings. — (See Mould- 
ings, Electric Wood) 

Electric Work. — (See Work, Electric) 

Electrical Controlling Clock. — (See 
Clock, Electrical Controlling) 

Electrically. — In an electrical manner. 

Electrically Controlled Clock. — (See 
Clock, Electrically Controlled) 



Ele.] 



191 



[Ele. 



Electrically Discharge, To (See 

Discharge, To Electrically^) 

Electrically Discharging. — (See Dis- 
charging; Electrically.) 

Electrically Energizing. — (See Energiz- 
ing, Electrically^) 

Electrically Operated Alarm. — (See 
Alarm, Electrically Operated^) 

Electrically Ketarding. — (See Retard- 
ing, Electrically^) 

Electrician. — One versed in the principles 
and applications of electrical science. 

Electrician, Electro-Therapeutical 

— A medical electrician. 

Electrician, Medical —One skilled 

in the application of electricity to the human 
body for diagnosis or curative purposes. 

A medicai electrician should possess a full 
knowledge, not only of the principles and appli- 
cations of electric science, but also of physics and 
chemistry and of the medical sciences. 

Electricity. — The name given to the un- 
known thing, matter or force, or both, which 
is the cause of electric phenomena. 

Electricity, no matter how produced, is oe- 
lieved to be one and the same thing. 

The terms frictional '-electricity, pyro-electricity, 
magneto-electricity , voltaic or galvanic electricity, 
thermo-electricity^ contact-electricity, animal or 
'vegetable-electricity ', etc., etc., though convenient 
for distinguishing their origin, have no longer 
the significance formerly attributed to them as 
representing different kinds of the electric force. 
(See Electricity, Single-Fluid Hypothesis of. ) 

Electricity, Accumulated — Elec- 
tricity collected in or by means of accumula- 
tors. 

Electricity, Accumulating ■ —Ob- 
taining successively increasing electrical 
charges. (See Electricity, Accutnulation of.) 

Electricity, Accumulation of A 

general term applied indifferently to — 

(i.) The gradual collecting of electric 
energy in a Leyden jar or condenser. 

(2.) The increase of an electric charge by 
the action of various devices called accumu- 
lators. 



(3.) The production of a charge by the use 
of machines called influence machines. 

(4.) The collection of electric energy in the 
so-called storage batteries or accumulators. 

Electricity, Animal — Electricity 

produced during life in the bodies of animals. 

All animals produce electricity during life. In 
some, such as the electric eel or torpedo, the 
amount is comparatively large. In others, it is 
small. 

Some of these animals, when of full size, are able 
to give very severe shocks, and use this curious 
power as a means of defense against their enemies. 

If the spinal cord of a recently killed frog be 
brought into contact wi.h the muscles of the 
thigh, a contraction will ensue. — (Matteucci.) 

The nerve and muscle of a frog, connected 
by a water contact with a sufficiently delicate 
galvanometer, show the presence of a current 
that may last several hours. Du Bois-Reymond 
showed that the ends of a section of muscular 
fibres are negative, and their sides positive, and 
has obtained a current by suitably connecting 
them. 

In the opinion of some electro-therapeutists no 
electric current exists in passive, normal nerve or 
muscular tissue. In an in j ured tissue a current, 
called a demarcation current, is produced. (See 
Current, Demarcation.} 

All muscular contractions, however, apparently 
produce electric currents. 

In electro-therapeutics, it is probable that 
greater success would accrue in practice if the 
human body were regarded as an electric source 
as well as an electro-receptive device. 

Electricity, Atmospheric The free 

electricity almost always present in the atmos- 
phere. 

The following facts have been discovered con- 
cerning atmospheric electricity, viz.: 

(1.) The free electricity of the atmosphere is 
generally positive, but often changes to negative 
on the approach of fogs and clouds. 

(2.) It exists in greater quantity in the higher 
regions of the air than near the earth's surface. 

(3.) It is stronger when the air is still than 
when the wind is blowing. 

(4.) It is subject to yearly and daily changes 
in its intensity, being stronger in winter than in 
summer, and at the middle of the day than either 
at the beginning or the close. 



Ele.] 



192 



LEle* 



Electricity, Atmospheric, Origin of 

• — The exact cause of the free electricity of 
the atmosphere is unknown. 

Peltier ascribes the cause of the free electricity 
of the atmosphere to a negatively excited earth, 
which charges the atmosphere by induction. (See 
Induction, Electrostatic.) Free atmospheric elec- 
tricity has also been ascribed to the evaporation 
of water; to the condensation of vapor; to the 
friction of the wind; to the motion of terrestrial 
objects through the earth's magnetic field; to in- 
duction from the sun and other heavenly bodies; 
to differences of temperature; to combustion, and 
to gradual oxidation of plant and animal life. It 
is possible that all these causes may have some 
effect in producing the free electricity of the at- 
mosphere. 

Whatever is the cause of the free electricity of the 
atmosphere, there can be but little doubt that it 
is to the condensation of aqueous vapor that the 
high difference of potential of the lightning flash 
is due. (See Potential, Difference of.) As the 
clouds move through the air they collect the free 
electricity on the surfaces of the minute drops of 
water of which they are composed, and when 
many thousands of these subsequently collect in 
larger drops the difference of potential is enor- 
mously increased in consequence of the equally 
enormous decrease in the surface of any single 
drop over the sum of the surfaces of the drops 
that have coalesced to form it. 

Electricity, Atom of A quantity 

of electricity equal in amount to that pos- 
sessed by any chemical monad atom. 

Professor Lodge points out the fact that the 
charge of a monad atom of any element is the 
smallest charge a body can possess, and is possibly 
as indivisible as the atom itself. He points out the 
fact that chemical affinity or atomic attraction may 
be due to the electrical attraction of atoms contain- 
ing unlike charges; that although the difference of 
potential between the atoms is small, probably 
somewhere between I and 3 volts, the distances 
separating them are so very small that their 
mutual attractive force must be almost infinitely 
great. 

As D'Auria has pointed out, if the centres of at- 
traction of the atoms be the cei tres of the 
atoms themselves, then the atoms, if approached 
to actual contact, would be separated f om one 
another by a distance equal to half the sum of 
their diameters. If, however, the centre of at- 



traction be situated at any point on the surface of 
the atoms the distance of separation would be- 
come equal to zero, calling d, the distance be- 
tween them, m and m 1 , their respective masses, 
and S, a co-effecient varying with the substance,, 
and f, the force of mutual attraction, then : 



f 



/m m'\ 



from which we see that the value of f x becomes 
infinite when the atoms are in contact. 

Electricity, Cal — Electricity pro- 
duced by changes of temperature in the core 
of a transformer. 

The changes of temperature in the transformer 
core can produce a difference of potential in the 
secondary circuit which increases the electro- 
motive force induced in the secondary by the 
variations in the primary. This is sometimes 
called the Acheson effect. (See Effect, Acheson.) 

Electricity, Conservation of — A 

term proposed by Lippman to express the 
fact that when a body receives an electric 
charge in the open air, the earth and heavenly- 
bodies receive an equal and opposite charge, 
thus preserving the sum of the total positive 
and negative electricities in the universe, 

Electricity, Contact — Electricity 

produced by the mere contact of dissimilar 
metals. 

The mere contact of two dissimilar metals re- 
sults in the production of opposite electrical, 
charges on their opposed surfaces, or in a differ- 
ence of electric potential between these surfaces* 
The cause of this difference of potential is now 
very generally ascribed to the voltaic couple being 
surrounded by the atmosphere, the oxygen of 
which acts more energetically on the positive 
element than it does on the negative element. 

The mere contact of dissimilar metals cannot 
produce a constant electric current. An electric 
current possesses kinetic energy. To produce a 
constant electric current, therefore, energy must 
be expended. 

The voltaic pile through the contact of dis- 
similar metals produces a difference of potential, 
yet the cause of the current is to be found in 
chemical action. (See Cell, Voltaic.) 

Electricity, Disguised —Dissimu- 
lated electricity. (See Electricity, Dissimu- 
lated or Latent.) 



Ele.] 



193 



[Ele. 



Electricity, Dissimulated or Latent 

--The condition of an electric charge when 
placed near an opposite charge, as in a Leyden 
jar or condenser. 

In this case, merely touching one of the 
charged surfaces will not effect its complete dis> 
charge. 

Electricity in the condition of a bound charge 
was formerly called latent electricity. This term 
is now in disuse. Such a charge is now called a 
bound charge. (See Charge, Bound. C/iarge, 
Free.) 

Electricity, Distribution of — Va- 
rious combinations of electric sources, circuits 
and electro-receptive devices whereby elec- 
tricity generated by the sources is carried or 
distributed to more or less distant electro- 
receptive devices by means of the various cir- 
cuits connected therewith. 

A number of different systems for the distribu- 
tion of electricity exist. Among the most import- 
ant are the following, viz. : 

(i.) Direct or continuous-current distribution. 

(2.) Alternating- current distribution. 

(3.) Storage battery or secondary distribution. 

(4.) Distribution by means of condensers. 

(5.) Distribution by means of motor-gener- 
ators. 

Electricity, Distribution of, by Alterna- 
ting Currents A system of electric 

distribution by the use of alternating currents. 

A system of electric distribution in which 
lamps, motors, or other electro-receptive de- 
vices are operated by means of alternating 
currents that are sent over the line, but which, 
before passing through said devices, are modi- 
fied by apparatus called transformers or con- 
verters. 

Such a system embraces : 

(1.) An alternating-current dynamo- electric 
machine or battery of machines. 

(2.) A conductor or line wire arranged in a 
metallic circuit. 

(3.) A number of converters or transformers 
whose primary coils are placed in the circuit of 
the line wire. 

(4.) A number of electro-receptive devices 
placed in the circuit of the secondary coil of the 
converter. (See Transformer.') 



Electricity, Distribution of, by Alterna- 
ting 1 Currents by Means of Condensers 

— A system of alternate current distribution 
in which condensers are employed to trans- 
form current of high potential received from 
an alternating current dynamo to currents 
of low potential which are fed to the lamps or 
other electro-receptive devices. 

In the system of McElroy the conversion from 
high to low potential is obtained by making the 
primary plates of the condensers charged by 
the dynamo smaller than the secondary plates, 
the ratio of the area of the primary plates to that 
of the secondary plates being made in accordance 
with the ratio of conversion desired. 

Electricity, Distribution of, by Commuta- 

ting Transformers A system of elec° 

trical distribution in which motor-generators 
are used, but neither the armature nor the 
field magnets are revolved, a special commu- 
tator being employed to change the polarity 
of the magnetic circuits. 

Electricity, Distribution of, by Constant 

Currents A system for the distribution 

of electricity by means of direct, z. e., con- 
tinuous, steady or non-alternating currents, 
as distinguished from alternating currents. 

Distribution by means of direct currents may 
be effected in a number of ways ; the most im- 
portant are: 

(1.) Distribution with constant current or 
series -distribution. 

(2.) Distribution with constant potential or 
multiple-distribution. 

Strictly speaking, these, as, indeed, all systems, 
are systems for the distribution of electric energy 
rather than the distribution of electricity. 

In a system of series-distribution, the electro- 
receptive devices are placed in the main line in 
series, so that the electric current passes succes- 
sively through each of them. In such a system 
each device added increases the total resistance of 
the circuit so that the total resistance is equal to 
the sum of the separate resistances on the line. 

In order, therefore, to maintain the current 
strength constant, independent of the number of 
devices added to or removed from the circuit, the 
electromotive force of the source must increase 
with each electro-receptive device added, and de- 
crease with each electro-receptive device taken 



Bio.] 



194 



[Eie. 



out. If the number of electro-receptive devices 
be great, such a circuit is necessarily character- 
ized by a comparatively high electromotive force. 

Since the current passes successively through 
all the electro-receptive devices, an automatic 
safety device is necessary in order to automatically 
provide a short circuit of comparatively low resist- 
ance past a faulty device, and thus prevent a 
single faulty device from invalidating the action 
of all other devices in the circuit. 

Arc lamps are usually connected to the line 
circuit in series. 

In a system of multiple -distribution, the electro- 
receptive devices are connected to the main line 
or leads in multiple -arc, or parallel, so that each 
device added decreases the resistance of the circuit. 
In order, therefore, to maintain a proper current 
through the electro-receptive devices, the mains 
must be kept at a nearly constant difference of 
potential. The electro-receptive devices employed 
in such a system of distribution are generally of 
high electric resistance, so that the introduction or 
removal of a few of the electro-receptive devices 
will not materially alter the resistance of the whole 
circuit, and will not, therefore, materially affect 
the remaining lights. 

In this system automatic safety devices, opera- 
ting by the fusion of a readily melted alloy or 
metal, are provided for the purpose of preventing 
too powerful currents from passing through any 
branch connected with the main conductors or 
leads. (See Plug, Fusible.) 

Incandescent lamps are generally connected 
with the main conductors or leads in parallel or 
multiple-arc. 

Distribution of incandescent lamps by series 
connections is sometimes employed. Such lamps 
are usually of comparatively low resistance, and 
are provided each with an automatic cut-out, 
which establishes a short circuit past the lamp on 
its failure to properly operate. 

During the passage of an electric current 
through any series-distribution circuit, energy is 
expended in different portions of the circuit, in 
proportion to the resistance of these parts. In 
any system, economy of distribution necessitates 
that the energy expended in the electro-receptive 
devices must bear as large a proportion as prac- 
ticable to the energy expended in the source and 
leads. In series-distribution, this can readily be 
accomplished even if the resistance of the leads is 
comparatively high, since the total resistance of 
the circuit increases with every electro-receptive 



device added. Comparatively thin wires can 
therefore be employed for a very considerable 
extent of territory covered, without very great 
loss. 

In systems of multiple-distribution, however, 
this is impossible ; for, since every electro -recep- 
tive device added decreases the total resistance of 
the circuit, unless the resistance of the leads is 
correspondingly decreased the economy becomes 
smaller, unless the resistance of the leads was orig- 
inally so low as to be inappreciable when com- 
pared with the change of resistance. 

In systems of distribution by alternating cur- 
rents this is avoided by passing a current of but 
small strength and considerable difference of 
potential over a line connecting distant points, 
and converting this current into a current of large 
strength and small difference of potential at the 
places where it is required for use. 

Electricity, Distribution of, by Contin- 
uous Current, by Means of Condensers 

A system of distribution devised by 

Doubrava, in which a continuous current is 
conducted to certain points in the line where 
a device called a " disjunctor " is employed, to 
reverse it periodically, and the reversed cur- 
rents so obtained directly used to charge con- 
densers in the circuit of which induction coils 
are used. 

This method of distribution is a variety of dis- 
tribution by means of constant currents. 

The condensers are used to feed incandescent 
lamps or other electro-receptive devices. 

Electricity, Distribution of, by Continu- 
ous Current, by Means of Transformers 

■ — A system for the transmission of elec- 
tric energy by means of continuous or direct 
currents that are sent over the line to suitably 
located stations where motor-dynamos are 
used for transformers. 

The dynamo armature is used with two sepa- 
rate circuits, one of a short and coarse wire, and 
one of a long fine wire. This construction will 
permit the conversion of a high to a low potential 
or vice versa; or two separate dynamos can be 
placed on the same shaft and one used as the 
motor. 

It is evident that a motor generator can be con- 
structed to convert continuous currents into alter- 
nate, or alternate currents into continuous cur- 



Ele.] 



195 



[Ele, 



rents. In this last case the armature and fixed 
circuits must be kept separate. 

Another form of continuous current conversion 
is effected by means of the motion of a commutator 
which effects a rotation of magnetic polarity in a 
double- wound armature of fine and coarse wire. 

Electricity, Distribution of, by Motor 
Generators A system of electric dis- 
tribution in which a continuous current of 
high potential, distributed over a main line, is 
employed at the points where its electric en- 
ergy is to be utilized for driving a motor, 
which in turn drives a dynamo, the current of 
which is used to energize the electro-recep- 
tive devices. 

This method of distribution is a variety of dis- 
tribution by means of continuous or direct cur- 
rents. 

In another system of distribution by means of 
motor generators, the motor and dynamo are 
combined in one with a double-wound armature, 
the fine wire coils in which receive the high po- 
tential driving current and the coarse wire coils 
furnish the low potential current used in the dis- 
tribution circuits. 

Electricity, Double Fluid Hypothesis of 
A hypothesis which endeavors to ex- 
plain the causes of electric phenomena by the 
assumption of the existence of two different 
electric fluids. 

The double fluid hypothesis assumes: 

(i.) That the phenomena of electricity are due 
to two tenuous and imponderable fluids, the posi- 
tive and the negative. 

(2.) That the particles of the positive fluid repel 
one another, as do also the particles of the nega- 
tive fluid; but that the particles of positive fluid 
attract the particles of the negative and vice versa. 

(3.) That the two fluids are strongly attracted 
by matter, and when present in it produce elec- 
trification. 

(4.) That the two fluids attract one another and 
unite, thus masking the properties of each. 

(5.) That the act of friction separates these 
fluids, one going to the rubber and the other to 
the thing rubbed. 

Professor Lodge is disposed to favor the double 
rather than the single fluid hypothesis. He states 
in support of this belief the following facts, viz. : 

(1.) An electric wind or breeze is produced 
both at the positive and negative terminals of an 



electrical machine, and this whether the point be 
attached directly to these terminals, or whether 
it be held in the hand of a person near them. 

(2.) The well known peculiarities connected 
with the spark discharge, seen in Wheatstone's 
experiments on the velocity of electricity. 

(3.) An electrostatic strain scarcely affects t 1 e 
volume of the dielectric, thus suggesting or show- 
ing a distorting stress, which alters the shape of 
the substance of the dielectric, but not its size. 

(4.) The effects of electrolysis in what he as- 
sumes the double procession of the atoms past 
each other in opposite directions. 

(5.) The phenomena of self-induction, or the 
behavior of a thick wire on an alternating current. 

(6.) The apparent absence of momentum in the 
electric current, or moment of inertia in an elec- 
tro-magnet so far as tested. 

Electricity, Dynamic A term some- 
times employed for current electricity in con- 
tradistinction to static electricity. 

Electricity, Franklinic —A term 

sometimes employed in electro-therapeutics, 
for the electricity produced by a frictional 
or an electrostatic-induction machine. (See 
Curre?it t Franklinic.) 

Electricity, Frictional Electricity 

produced by friction. 

This term as formerly employed to indicate 
static charges as distinguished from currents, is 
gradually falling into disuse, and the frictional 
electric machines are being generally replaced by 
continuous-induction machines, like those of 
Holtz, Tupler-Holtz, or Wimsrmrst. 

The character of the charge produced by fric- 
tion depends on the nature of the rubber as well 
as on that of the thing rubbed. 

In the following table the substances are so ar- 
ranged that any one in the list becomes positively 
electrified when rubbed by any which follows it : 

Positive. 
Cat's fur. 
Polished glass. 
Wool. 

Cork at ordinary temperatures. 
Coarse brown paper. 
Cork heated. 
White silk. 
Black silk. 
Shellac. 
Rough glass. — {Forbes.) 



Elc] 



196 



[Ele. 



Negative. 

It will be seen that the character of the charge 
produced by friction depends on the character of 
the surfaces rubbed. This is seen from the fore- 
going table, where — 

(i.) The roughness of the surface, as in the 
case of glass, produces a difference in the nature of 
the charge; thus, rough glass is at the bottom of 
the table, and smooth, polished glass near the top. 

(2.) The state of the surface as shown by the 
color. Black silk rubbed with white silk is nega- 
tive to it. 

(3.) The state of the surface, as varied by the 
temperature. Hot cork receives a negative charge 
when rubbed against a piece of cold cork. 

Forbes has pointed out that these differences 
are probably due to the change produced in the 
ability of the surface to radiate heat or light. A 
substance or body which radiates the most light 
or heat is negative. Thus, a hot body radiates 
more heat than a cold body, and is negative to it. 
A rough surface is negative to a smooth surface 
because it radiates more heat than a smooth sur- 
face. For the same reason a black surface is neg- 
ative to a white surface. In this latter case, how- 
ever, the black surface is the worse radiator of 
light. 

The contact of dissimilar substances has long 
been considered by some as one of the requisites 
for the ready production of electricity by friction. 
In fact, the production of electricity by friction 
has been ascribed as an effect due to a true contact 
force at the points of junction of the rubber and 
the thing rubbed. Others, however, deny the 
existence of a true contact force of this nature. 
(See Force, Contact.) 

Electricity, Galvanic A term used 

by some in place of voltaic electricity. (See 
Electricity, Voltaic^) 

The use of the term galvanic electricity would 
appear to be less logical than the word voltaic, 
since Volta, and not Galvani, was the first to find 
out the true origin of the difference of potential 
produced in the voltaic pile. 

Electricity, Hertz's Theory of Electro- 
Magnetic Radiations or Waves — A 

theory, now generally accepted, which regards 
light as one of the effects of electro-magnetic 
pulsations or waves. 

The recent brilliant researches of Dr. Hertz, of 
Carlsruhe, show that when an impulsive discharge 



is passing through a conductor, ether waves are 
radiated or propagated in all directions in the 
space surrounding the conductor, and that these 
waves are in all respects similar to those of light, 
except that they are much longer. 

The electro-magnetic waves are set up in the 
luminiferous ether, and move through it with the 
same velocity as that of light. Moreover, electro- 
magnetic waves possess the same powers of reflec- 
tion, refraction, interference, resonance, etc., etc., 
as are possessed by waves of light. (See Resona- 
tor, Electric.) 

When an alternating or simple faradic current 
or pulse of electricity is transmitted from one end 
to the other of a long metallic conductor, the 
pulses are believed to travel through the universal 
ether surrounding the conductor rather than 
through the conductor itself. The velocity of this 
propagation in free ether is the same as that of 
light, and, indeed, is identical with that of light 
itself. In the inter-atomic or inter -molecular 
ether, whether of conductors, or of dielectrics, the 
velocity of propagation varies with the nature of 
the medium. 

The waves produced by electric pulses are of 
much greater length than those of light. 

According to Lodge a condenser of the capacity 
of a micro-farad, if discharged through a coil hav- 
ing the self-induction of I ohm, will give rise 
to waves in the ether 1,200 miles in length, and 
will possess a rate of oscillation equal to about 157 
complete wave-lengths per second. 

A common pint Ley den jar discharged through 
an ordinary discharging rod, will produce a se- 
ries of waves about 15 to 20 metres in length, 
and will possess a rate of oscillation equal to about 
ten million per second. 

Lodge calculates that in order to obtain the short 
waves requisite to influence the retina of the eye, 
and thus produce light, the circuit in which the 
electrical oscillations take place must have at least 
atomic dimensions, and that the phenomena of 
light may therefore be due to local oscillations or 
surgings in circuits of atomic dimensions. (See 
Light, Maxwell's Electro-Magnetic Theory of.) 



-A term for- 



Electricity, Latent — 

merly applied to bound electricity. 

Electricity, Magneto Electricity 

produced by the motion of magnets past con- 
ductors, or of conductors past magnets. 

Electricity produced by magneto-electric 



Ete.] 



197 



[Ele. 



induction. (See Induction, Electro-Dyna- 
mic.') 

Electricity, Multiple-Distribution of, by 
Constant Potential Circuit — Any 

system for the distribution of continuous cur- 
rents of electricity in which the electro- 
receptive devices are connected to the leads 
in multiple-arc or parallel. (See Electricity, 
Distribution of, by Cotistant Currents.) 

Electricity, Natural Unit of A 

term sometimes used in place of an atom of 
electricity. 

The natural unit of electricity is an amount 
equal to the charge possessed by any monad atom 
of a chemical element. 

The natural unit of electricity is equal to the 
hundred thousand millionth of the ordinary 
electrostatic unit, or less than a hundred tril- 
Honth of a coulomb. (See Electricity, Atom of .) 

Electricity, Negative One of the 

phases of electrical excitement. 

The kind of electric charge produced on 
yesin when rubbed with cotton. 

Electricity, Photo Electrical dif- 
ferences of potential produced by the action 
of light 

Electricity, Plant Electricity pro- 
duced in plants during their growth. 

Electricity, Positive One of the 

phases of electric excitement. 

The kind of electric charge produced on 
cotton when rubbed against resin. 

Electricity, Production of, by Light 

- — The production of electric differences of 
potential by the action of light. 

Hallwachs has noticed that a clean metallic 
plate becomes electrified when light falls upon it. 

Differences of potential are produced in a 
selenium cell when its electrodes are unequally 
illumined. A thermo cell is an illustration of a 
difference of potential produced by non-luminous 
radiation. 

Electricity, Pyro Electricity de- 
veloped in certain crystalline bodies by un- 
equally heating or cooling them. 

Tourmaline, in the crystalline state, possesses 
this property in a marked degree. When a 
crystal of tourmaline is heated or cooled, it 




V^ 




acquires opposite electrifications at opposite 
ends or poles. 

In the crystal of tourmaline shown in Fig. 227, 
the end A, called the analogous pole, acquires a 
positive electrification, 
and the end B, called the 
antilogous pole, a nega- 
tive electrification, while 
the temperature of the 
crystal is rising. While 
cooling, the opposite 
electrifications are pro- 
duced. 

A heated crystal of 
tourmaline, suspended by 
a fibre, is attracted or 
repelled by an electrified 
body or by a second A 

heated tourmaline, in the Fi S- 227. Pyro Electric 
same manner as an elec- Crystal. 

trifled body. 

Many crystalline bodies possess similar prop- 
erties. Among these are the ore of zinc known 
as electric calamine or the silicate of zinc, bora- 
cite, quartz, tartrate of potash, sulphate of 
quinine, etc. 

Electricity, Radiation of — The 

radiation of electric energy by means of elec- 
tro-magnetic waves. (See Electricity, Hertz's 
Theory of Electro-Magnetic Radiations or 
Waves.) 

Electricity, Resinous A term 

formerly employed in place of negative elec- 
tricity. 

It was at one time believed that all resinous 
substances are negatively electrified by friction. 
This we now know to be untrue, the nature of 
electrification depending as much on the char- 
acter of the rubber as on the character of the 
thing rubbed. Thus resins rubbed with cotton, 
flannel or silk, become negatively excited, but when 
rubbed with sulphur or gun cotton, positively 
excited. The terms positive and negative are 
now exclusively employed. 

Electricity, Series Distribution of, by 
Constant Current Circuit Any sys- 
tem for the distribution of constant currents 
of electricity in which the electro-receptive 
devices are connected to the line-wire or 
circuit in series. (See Electricity, Distribu- 
tion of, by Constant Ctirrents.) 



Ele.] 



198 



[Ele. 



Electricity, Single-Fluid Hypothesis of 

-A hypothesis which endeavors to ex- 



plain the cause of electrical phenomena by 
the assumption of the existence of a single 
electric fluid. 

The single-fluid hypothesis assumes: 

(i.) That the phenomena of electricity are due 
to the presence of a single, tenuous, imponder- 
able fluid. 

(2 ) That the particles of this fluid mutually 
repel one another, but are attracted by all matter. 

(3.) That every substance possesses a definite 
capacity for holding the assumed electric fluid, 
and, that when this capacity is just satisfied no 
effects of electrification are manifest. 

(4.) That when the body has less than this 
quantity present, it becomes negatively excited, 
and when it has more, positively excited. 

(5.) That the act of friction causes a redistribu- 
tion of the fluid, part of it going to one of 
the bodies, giving it a surplus, thus positively 
electrifying it, and leaving the other with a 
deficit, thus negatively electrifying it. 

The single-fluid hypothesis has been provis- 
ionally accepted by some with this modification, 
that a negatively excited body is thought to be 
the one which contains the excess of the assumed 
fluid, and a positively excited body the one which 
contains the deficit. 

They make this change on account of the 
phenomena observed in Crookes' tube, where 
the molecules of the residual gas are observed to 
be thrown off" from the negative and not from the 
positive terminal. (See Tube, Crookes\) 

Another view considers electricity to be due to 
differences of ether pressure, electricity being the 
ether itself, and electromotive force, the differences 
of ether pressures. Positive electrification is as- 
sumed to result from a surplusage of energy, and 
negative electrification from a deficit of energy. 

At the present time the views of Hertz are 
generally accepted. (See Electricity, Hertz's 
Theory of Electro-Magnetic Radiations or Waves.') 

Electricity, Specific Heat of A 



term proposed by Sir William Thomson to 
indicate the analogies existing between the 
absorption and emission of heat in purely 
thermal phenomena, and the absorption and 
emission of heat in thermo-electric phe- 
nomena. (See Heat, Specific?) 

As we have already seen heat h either given 



out or absorbed, when an electric current passes 
from one metal to another across a junction be- 
tween them. (See Effect, Peltier.} 

So, too, when electricity passes through an un- 
equally heated wire, the current tends to increase 
or decrease the differences of temperature, ac- 
cording to the direction in which it flows, and 
according to the character of the metal. (See 
Effect, Thomson.) 

1 ' If electricity were a fluid," says Maxwell, 
" running through the conductor as water does 
through a tube, and always giving out or ab- 
sorbing heat till its temperature is that of the 
conductor, then in passing from hot to cold it 
would give out heat, and in passing from cold to 
hot it would absorb heat, and the amount of this 
heat would depend on the specific heat of the 
fluid." 

Electricity, Static A term applied 

to electricity produced by friction. 

The term static electricity is properly em- 
ployed in the sense of a static charge but not as 
static electricity, since that would indicate a par- 
ticular kind of electricity, and, as is now gen- 
erally recognized, electricity, from no matter 
what source it is derived, is one and the same 
thing. 

Electricity, Storage of A term 

improperly employed to indicate such a 
storage of energy as will enable it to directly 
reproduce electric energy. 

A so-called storage battery does not store elec- 
tricity, any more than the spring of a clock can 
be said to store time or sound. The spring stores 
muscular ene-gy, i. e., renders the muscular 
kinetic energy potential, which, again becoming 
kinetic, causes the works of the clock to move 
or strike. 

In the same way in a so-called storage battery, 
the energy of an electric current is caused to 
produce electrolytic decompositions of such a 
nature as independently to produce a current on 
the removal of the electrolyzing current. (See 
Cell, Secondary. Cell, Storage.) 

Electricity, Thermo Electricity 

produced by differences of temperature at the 
junctions of dissimilar metals. 

If a bar of antimony is soldered to a bar of bis- 
muth, and the free ends of the two metals are 
connected by means of a galvanometer, an appli- 
cation of heat to the junction, so as to raise its 



Elo.J 



199 



[Ele. 



temperature above the rest of the circuit, will pro- 
duce a difference of potential, which, if neutral- 
ized, will cause a current to flow across the junc- 
tion from the bismuth to the antimony (against 
the alphabet, or from B to A). If the junction be 
cooled below the rest of the circuit, a current is 
produced across the junction from the antimony 
to the bismuth (with the alphabet, or from A to B). 
These currents are called thermo-electric currents, 
and are proportional to the differences of tem- 
perature. 

Even the same metal, in different physical 
states or conditions, such as a wire, part of which 
is straight and the remainder bent into a spiral as 
at H C, Fig. 228, if heated at F by the flame of 
F 




Fig. 228. Thermo- Electricity. 

a lamp will have a difference of potential devel- 
oped in it. 

The same thing may also be shown by placing 
a cylinder of bismuth J, Fig. 229, in a gap in a 

A 




Fig. 2 2Q. Thermo- Electric Circuit. 

hollow rectangle of copper A B, inside of which 
a magnetic needle, M, is supported. 

The rectangle of copper being placed in the 
magnetic meridian, on heating the junction by the 
flame of a lamp F, the needle will be deflected 
by a current produced by the difference of tem- 
perature. 

Thermo-electricity is generally obtained by 
means of the combination of a thermo-electric 
couple, in a thermo-electric cell. (See Couple, 
Thermo- Electric. Cell, Thermo-Electric.) 

Since the difference of potential produced by 
a single thermo-electric couple is small, a number 
of such couples or cells are generally connected in 



series to produce a thermo-electric battery. (See 
Battery, Thermo-Electric. ) 

Electricity, Unit Quantity of — 

The quantity of electricity conveyed by unit 
current per second. 

The practical unit quantity of electricity is the 
coulomb, which is the quantity conveyed by a 
current of one ampere in one second. 

Electricity, Unit Quantity of, Natural 

The quantity of electricity pos- 
sessed as a charge by any elementary monad 
atom. (See Electricity, Atom of) 

Electricity, Yarieties of A classi- 
fication of electricity according to its state of 
rest or motion, or to the peculiarities of its 
motion. 

Lodge classifies the different varieties of elec- 
tricity as follows, viz. : 

(1.) Electricity at Rest, or Static Electricity. 

This branch of electric science treats of phenom- 
ena belonging to stresses and strains in insulated 
media, when brought into the neighborhood of 
electric charges, together with the modes of ex- 
citing such electric charges, and the laws of their 
interactions. 

(2. ) Electricity in Locomotion, or Current Elec- 
tricity. 

This branch of electric science treats of the phe- 
nomena produced in metallic conductors, chem- 
ical compounds and dielectric media, by the pas- 
sage of electricity through them, and the modes 
of exciting electricity into motion, together with 
the laws of its flow. 

(3.) Electricity in Rotation, or Magnetism. 

This branch of electric science treats of the phe- 
nomena produced in electricity in whirling or 
vortex motion, the manner in which such whirls 
may be produced, the strains and stresses which 
they produce, and the laws of their interactions. 

(4.) Electricity in Vibration, or Radiation. 

This branch of electric science treats of the study 
of the propagation of periodic or undulatory dis- 
turbances through various kinds of media, the 
laws regulating wave velocity, wave length, re- 
flection, interference, dispersion, polarization and 
other similar phenomena generally studied under 
light. 

A misleading classification of electricity is 
sometimes made according to the sources which 
produce it. This is misleading, since electricity, 
no matter how produced, is one and the same. 



Ele.] 



200 



[Ele. 



The so-called varieties of electricity may be di- 
vided into different classes according to the nature 
of the source. The principles of these are as fol- 
lows : 

(i.) Frictional-Electricity, or that produced by 
the friction of one substance against another. 

(2.) Voltaic-Electricity, or that produced by 
the contact of dissimilar substances under the in- 
fluence of chemical action. 

(3.) Thermo-Electricity, or that produced by 
differences of temperature in a thermo couple. 

(4.) Pyro-Electricity, or that produced by dif- 
ferences of temperature in certain crystalline 
solids. 

(5.) Magneto-Electricity, or that produced by 
the motion of a conductor through the field of 
permanent magnets. This is a variety of — 

(6.) Dynamo-Electricity, or that produced by 
moving conductors so as to cut lines of magnetic 
force. 

(7.) Vital-Electricity, or that produced under 
the influence of life or accompanying life. 

Electricity, Vitreous — A term for- 
merly employed to indicate positive elec- 
tricity. 

It was formerly believed that the friction of 
glass with other bodies always produces the 
same kind of electricity. This, however, is now 
known not to be the case. 

The term is now replaced by positive elec- 
tricity. (See Electricity, Resinous.) 

Electricity, Voltaic ■ ■ — Differences of 

potential produced by the agency of a vol- 
taic cell or battery. 

Electricity is the same thing or phase of energy 
by whatever source it is produced. 

Electrics. — Substances capable of becom- 
ing electrified by friction. 

Substances like the metals, which, when held 
in the hand could not be electrified by friction 
were formerly called non-electrics. 

These terms were used by Gilbert in the early 
history of the science. 

This distinction is not now generally employed 
since conducting substances if insulated, may be 
electrified by friction. 

Electrifiable. — Capable of being endowed 
with electric properties. 

Electrification. — The act of becoming 
electrified. 

The production of an electric charge. 



Electrified Body.— (See Body, Electri- 
fied^ 

Electrify. — To endow with electrical prop- 
erties. 

Electrine. — Relating to electrum, or am- 
ber. 

Electrization, Therapeutical — Sub- 
jecting different parts of the human body to 
the action of electric currents for the cure of 
diseased conditions. 

Electro-Biology. — (See Biology, Electro?) 

Electro-Brassing. — (See Brassing, Elec- 
tron 

Electro-Bronzing". — (See Bronzing, Elec- 
tro^ 

Electro ■ Capillary Phenomena. — (See 
Phenomena, Electro-Capillary?) 

Electrocesis. — A word proposed for cur- 
ing by electricity. 

Electro-Chemical Equivalent. — (See 
Equiva lent, Electro- Chem ica I.) 

Electro-Chemical Meter. — (See Meter, 
Electro- Ch em ica I.) 

Electro-Chemical Telephone. — (See Tele- 
phone, Electro-Chemical.) 

Electro-Chemistry. — (See Chemistry, 
Electro?) 

Electro-Chromic Rings. — (See Rings, 
Electro- Ch rom ic.) 

Electro-Contact Mine. — (See Mine, Elec- 
tro-Contact.) 

Electro-Coppering. — (See Copperi7ig, 
Electro?) 

Electro-Crystallization. — (See Crystalli- 
zation, Electro?) 

Electrocution. — Capital punishment by 
means of electricity. 

Electrode. — Either of the terminals of an 
electric source. 

The term was applied by Faraday to either of 
the conductors placed in an electrolytic bath and 
conveying the current into it, and this is its staict 
meaning. The terms pole or terminal apply to 
the ends of a break in any electric circuit. 

Electrode, Aural A therapeutic 

electrode, shaped for the treatment of the 



Ele.] 



201 



[Ele. 



ear. (See Electrode, Electro-Thera- 
peutic?) 

Electrode, Brush A therapeutic 

electrode fashioned like a wire brush or other 
conducting brush. (See Electrode, Electro- 
Therapeutic?) 

Electrode, Cautery-Knife A knife- 
shaped electrode, that is rendered incan- 
descent by the passage of the electric cur- 
rent. 

Electrode, Clay A therapeutic elec- 
trode of clay shaped to fit the part of the 
body to be treated. (See Electrode, Electro- 
Therapeutic?) 

Electrode, Disc A disc-shaped elec- 
trode employed in electro-therapeutics. (See 
Electrode, Electro- Therapeutic?) 

Electrode, Dry A therapeutic elec- 
trode applied in a dry state. (See Electrode, 
Electro- Therapeutic?) 

Electrode, Electro-Therapeutic 

In electro-therapeutics the electrode mainly 
concerned in the treatment or diagnosis of the 
diseased parts. 

Either the positive or the negative electrode 
may be the therapeutic electrode, and one or the 
other is employed according to the particular 
character of the effect it is desired to obtain. 
The other electrode is placed at any convenient 
and suitable part of the body, and is called the 
indifferent electrode. 

The therapeutic electrode is generally placed 
nearer the organ or part to be treated than the 
indifferent electrode. 

Electrode-Handle, Pole-Changing- and 

Interrupting -A handle provided for 

the ready insertion of electro-therapeutic 
electrodes, and provided with means for inter- 
rupting or changing the direction of the cur- 
rent. 

Electrode, Illumined That elec- 
trode of a selenium cell which is exposed to 
the light. (See Cell, Seleniu?n.) 

Electrode, Indifferent In electro- 
therapeutics the electrode that is employed 
merely to complete the circuit through the 
or^an or part subjected to the electric cur- 



rent, and is not directly concerned in the 
treatment or diagnosis of the diseased parts. 
Either the positive or the negative electrode 
may be the indifferent electrode. (See Electrode, 
Electro- Therapeutic.) 

Electrode, Moist A therapeutic- 
electrode applied in a moist condition. (See 
Electrode, Electro- Therapeutic) 

Electrode, Needle A therapeutic 

electrode in the shape of a needle, and em- 
ployed for electrolytic treatment. (See Elec- 
trode, Electro- Therapeutic?) 

Electrode, Negative The electrode 

connected with the negative pole of an elec- 
tric source. 

Electrode, Non-Illumined — That 

electrode of a selenium cell that is protected 
from the direct action of light. (See Cell, Sel- 
enium?) 

Electrode, Non-Wasting A term 

sometimes applied to the negative electrode 
of an arc-lamp when made of iridium or other 
similar material. 

Electrode, Positive The electrode 

connected with the positive pole of an electric 
source. 

Electrode, Rectal A therapeutic 

electrode, suitably shaped for the treatment of 
the rectum. (See Electrode, Electro-Thera- 
peutic?) 

Electrode, Sponge A moistened 

sponge connected to one of the terminals of 
an electric source and acting as the electro- 
therapeutic electrode. 

Electrode, Urethral An electro- 
therapeutic electrode suitably shaped for the 
treatment of the urethra. (See Electrode, 
Electro- Therapeutic?) 

Electrode, Taginal — An electro- 
therapeutic electrode suitably shaped for the 
treatment of the vagina. (See Electrode, 
Electro- Therapeutic?) 

Electro-Deposits. — (See Deposits, Elec- 
tro?) 

Electrodes. — The terminals of an electric 
source. 

The positive electrode is sometimes called the 



Ele.] 



202 



[Ele. 



Anode, and the negative electrode the Kathode. 
No matter for what purposes employed, they are 
generally in electro-therapeutics termed electrodes. 
In precise use these terms should be restricted 
to the electrodes when used for electrolytic de- 
composition. 

The electrodes are made of different shapes and 
of different materials according to the character of 
the work the current is to perform. 

Electrodes, Carbon, for Arc-Lamps 

Rods of artificial carbon employed in arc 
lamps. 

These are more properly called simply arc- 
lamp carbons. 

Arc-lamp carbons are moulded into the shape 
of rods, from plastic mixtures of carbonaceous 
materials and carbonizable liquids. On the sub- 
sequent carbonization of these rods the ingredients 
are caused to cohere in one solid mass by the de- 
posit of carbon derived from the carbonizable 
materials. (See Carbons. Artificial.) 

Carbons for arc-lamps are generally copper- 
coated, so as to somewhat decrease their resist- 
ance, and insure a more uniform consumption. 
Arc-lamp carbons are sometimes provided with a 
central core of softer carbon, which fixes the po- 
sition of the arc and thus insures a steadier light. 
(Sec Pardons, Cored.) 

Electrodes, Cored Carbon elec- 
trodes of a cylindrical shape provided with a 
central cylinder of softer carbon. 

The use of cored electrodes for arc lamps is 
for the purpose of steadying the light by maintain- 
ing the arc in a central position. This is effected 
by the greater vaporization of the softer carbon 
of the core. 

Electrodes, Cylindrical Carbon 

Carbon cylinders used for electrodes of arc- 
lamps, or for battery plates. 

Electrodes, Electro-Therapeutic 

Electrodes of various shapes employed in 
electro-therapeutics. 

The electro-therapeutic electrode, as distin- 
guished from the indifferent electrode, is especially 
shaped for the particular purpose for which it is 
designed. 

When the electricity is intended to affect the 
skin or superficial portions of the body only, it is 
applied dry, and is then generally metallic. To 
reach the deeper structures, such as the muscle 
or nerve trunks, moistened sponge electrodes are 



employed. Before their use the skin should be 
thoroughly moistened. Sponge-electrodes are 
generally made conducting by a solution of some 
saline substance, such as common salt. 

Electrodes, Erb's Standard Size of 

— Standard sizes of electrodes generally 
adopted in electro-therapeutics. 

The following standard sizes have been pro- 
posed by Erb, viz. : 

( i.) Fine electrode y 2 centimetre diameter. 

(2.) Small •« 2 " " 

(3.) Medium " 7.5 " " 

(4.) Large " ...6x2 " '.' 

(5.) Very large do 8x16 " " 

Electrodes, Non-Polarizable — 

Electrodes employed in electro-therapeutics, 
that are so constructed as to avoid the effects 
of polarization. 

Non-polarizable electrodes are obtained by 
employing two amalgamated zinc wires, dipped 
into saturated solution of zinc chloride placed in 
glass tubes, and closing the lower ends of the 
tubes by a piece of potter's clay. The contact of 
an electrode so prepared with the tissues of the 
body does not produce a polarization. 

Electro-Diagnosis. — (See Diagnosis, Elec- 
tro?) 

Electro-Diagnostic. — (See Diagnostic, 
Electro?) 

Electro-Dynamic Attraction. — (See At- 
traction, Electro-Dynamic?) 

Electro-Dynamic Capacity. — (See Ca- 
pacity, Electro-Dyna7nic.) 

Electro-Dynamic Induction. — (See Induc- 
tion, Electro-Dynamic?) 

Electro-Dynamic Repulsion. — (See Re- 
pulsion, Electro-Dyna?nic.) 

Electro-Dynamics. — (See Dynamics, 
Electro?) 

Electro-Dynamometer. — (See Dynamom- 
eter, Electro?) 

Electro-Etching 1 .— Electric etching. (See 
Etching, Electro?) 

Electrogenesis. — Results following - the 
application of electricity to the spinal cord or 
nerve after the withdrawal of the electrodes. 

Electro-Gilding. — (See Gilding, Electro? 



Efe.] 



203 



[Ele. 



Electro-Kinetics. — (See Kinetics, Elec- 
tro) 

Electrolier. — A chandelier for holding- 
electric lamps, as distinguished from a chan- 
delier for holding gas-lights. 

Electrology. — That branch of science 
which treats of electricity. (Obsolete.) 

Electrolysis. — Chemical decomposition 
effected by means of an electric current. 

When an electric current is sent through an 
electrolyte, i. e., a liquid which permits the cur- 
rent to pass only by means of the decomposition 
of the liquid, the decomposition that ensues is 
called electrolytic decomposition. 

The electrolyte is decomposed or broken up 
into atoms or groups of atoms or radicals, called 
ions. 

The ions are of two distinct kinds, viz. : The 
electro-positive ions, or kathions, and the electro- 
negative ions, or anions. 

Since the anode of the source is connected with 
the electro-positive terminal, it is clear that the 
anions, or the electro-negative ions, must appear 
at the anode, and the kathions, or electro-positive 
ions, must appear at the kathode. 

Hydrogen, and the metals generally, are 
kathions. Oxygen, chlorine, iodine, etc., are 
anions. 

The vessel containing the electrolyte, in which 
these decompositions take place, is sometimes 
called an electrolytic cell. 

An electrolytic cell is called a volta?neter when 
it is arranged for measuring the current passing 
by means of the amount of decomposition it 
effects. (See Voltameter.) 

Electrolysis hj Means of Alternating* 
Currents. — Electrolytic decomposition ef- 
fected by means of alternating currents. 

When an alternating current is passed through 
dilute sulphuric acid, in a voltameter provided 
with large platinum electrodes, no visible decom- 
position occurs. If, however, the size of the 
electrodes be decreased below a certain point, 
then visible decomposition occurs. 

Verdet showed that when no other break ex- 
ists in the circuit of the alternating current 
within the voltameter, no indications of elec- 
trolysis are obtained, unless the alternating 
current is very powerful. If, however, a break is 
made in the secondary circuit, so that the dis- 



charge has to pass as a spark, then visible signs 
of electrolysis are produced by comparatively 
feeble alternating currents. 

When electrolysis occurs by means of alternat- 
ing currents — 

(i.) The gases collected at both electrodes 
have the same composition. 

(2.) Where the quantities of electricity that al- 
ternately pass in opposite directions are unequal, 
the electrodes show manifest polarization, and, 
when connected by a conductor, yield a current 
like a secondary battery. 

(3.) The electrodes manifest no sensible polari- 
zation where the quantities of electricity that al- 
ternately pass in opposite directions are equal. 

Electrolysis, Faraday's Laws of 



The principal facts of electrolysis are given 
in the following laws: 

(1.) The amount of chemical action in any 
given time is equal in all parts of the circuit. 

(2.) The number of ions liberated in a given 
time is proportional to the strength of the cur- 
rent passing. Twice as great a current will 
liberate twice as many ions. The current may 
be regarded as being carried through the elec- 
trolyte by the ions: since an ion is capable of 
carrying a fixed charge only of -f- or — electri- 
city, any increase in the current strength necessi- 
tates an increase in the number of ions. 

(3.) When the same current passes successively 
through several cells containing different elec- 
trolytes, the weights of the ions liberated at the 
different electrodes will be equal to the strength 
of the current multiplied by the electro-chemical 
equivalent of the ion. (See Equivalence, Elec- 
tro-Chemical, Law of.) 

The chemical equivalent is proportional to the 
atomic weight divided by the valency. (See 
Equivalent, Chemical. ) 

The electro -chemical equivalent of any element 
is equal to the weight in grammes of that element 
set free by one coulomb of electricity, and is found 
by multiplying the electro-chemical of hydrogen 
by the chemical equivalent of that element. (See 
Equivalent, Electro- Che?7iical. ) 



Electrolyte, Polarization of 



-The 



formation of molecular groups or chains, in 
which the poles of all the molecules of any 
chain are turned in the same direction, viz.: 
with their positive poles facing the negative 
plate, and their negative poles facing the 



Ele.] 



204 



[Ele, 



positive plate. (See Cell, Voltaic. Hypoth- 
esis, Grotthus'.) 

Electrolytic or Electrolytical. — Pertain- 
ing to electrolysis. 

Electrolytic Analysis. — (See Analysis, 
Electrolytic?) 

Electrolytic Cell.— (See Cell, Electro- 
lytic, Testa's?) 

Electrolytic Clock.— (See Clock, Electro- 
lytic.) 

Electrolytic Conduction. — (See Conduc- 
tion, Electrolytic.) 

Electrolytic Convection. — (See Convec- 
tion, Electrolytic.) 

Electrolytic Decomposition. — (See De- 
composition, Electrolytic?) 

Electrolytic Hydrogen. — (See Hydrogen, 
Electrolytic?) 

Electrolytic Writing. — (See Writing, 
Electrolytic?) 

Electrolytically. — In an electrolytic man- 
ner. 

Electrolyzable. — Capable of being elec- 
trolyzed, or decomposed by means of elec- 
tricity. 

Electrolyzed. — Separated or decomposed 
by means of electricity. 

Electrolyzing. — Causing or producing 
electrolysis. 

Electro-Magnet. — (See Magnet, Electro?) 

Electro-Magnetic Ammeter.— (See Am- 
meter, Electro-Magnetic?) 

Electro-Magnetic Annunciator.— (See 
Annunciator, Electro-Magnetic?) 

Electro-Magnetic Attraction. — (See At- 
traction, Electro-Magnetic?) 

Electro-Magnetic Bell-Call.— (See Call, 
Bell, Magneto-Electric?) 

Electro-Magnetic Bell, Siemens' Arma- 
ture (See Bell, Electro-Magnetic, 

Siemens' Armature Form?) 
. Electro-Magnetic Brake.— (See Brake, 
Electro-Magnetic?) 

Electro-Magnetic Cam.— (See Cam, 
Electro-Magnetic?) 



Electro-Magnetic Dental-Mallet. — (See 

Dental- Mallet, Electro-Magnetic?) 

Electro-Magnetic Drill.— (See Drill, 

Electro-Magnetic?) 

Electro-Magnetic Engine. — (See Engine, 
Electro-Magnetic.) 

Electro-Magnetic Exploder. — (See Ex- 
ploder, Electro-Magnetic.) 

Electro-Magnetic Eye. — (See Eye, Elec- 
tro-Magnetic.) 

Electro-Magnetic Impulse. — (See Im- 
pulse, Electro-Magnetic.) 

Electro-Magnetic Induction. — (See In- 
duction, Electro-Magnetic.) 

Electro-Magnetic Medium. — (See Me- 
dium, Electro-Magnetic?) 

Electro-Magnetic Meter. — (See Meter, 
Electro-Magnetic.) 

Electro-Magnetic Momentum of Sec- 
ondary Circuit. — (See Momentum, Elec- 
tro-Magnetic, of Secondary Circuit?) 

Electro-Magnetic Pop-Gun. — (See Pop- 
Gun, Electro-Magnetic.) 

Electro-Magnetic Badiation. — (See Ra- 
diation, Electro-Magnetic?) 

Electro-Magnetic Bepulsion. — (See Re- 
pulsion, Electro-Magnetic?) 

Electro-Magnetic Resonator. — (See Res- 
onator, Electro-Magnetic.) 

Electro-Magnetic Shunt. — (See Shunt, 
Electro-Magnetic?) 

Electro-Magnetic Solenoid. — (See Sole- 
noid, Electro-Magnetic?) 

Electro-Magnetic Strain. — (See Strain, 
Electro-Magnetic?) 

Electro-Magnetic Stress. — (See Stress, 
Electro-Magnetic?) 

Electro-Magnetic Theory of Light, Max- 
well's (See Light, Maxwell's Elec* 

tro-Magnetic Theory of.) 

Electro-Magnetic Yibrator— (See Vi- 
brator, Electro-Magnetic.) 

Electro-Magnetic Voltmeter.— (See Volt- 
meter, Electro-Magnetic.) 



Hie.] 



205 



[Ele. 



Electro-Magnetic Units. — (See Units, 
Electro-Magnetic?) 

Electro-Magnetics. — (See Magnetics, 
Electro?) 

Electro-Massage. — (See Massage, Elec- 
tro?) 

Electro-Mechanical Alarm. — (See Alarm, 
Electro-Mechanical.) 

Electro-Mechanical Gong. — (See Gong, 
Electro-Mechanical?) 

Electro-Metallnrgical Crystalline De- 
posit. — (See Deposit, Crystalline, Electro- 
Metallurgical?) 

Electro-Metallnrgical Galvanization.— 

(See Galvanization, Electro- Metallurgical?) 

Electro-Metallurgical Nodular Deposit. 

— (See Deposit, Electro - Metallurgical 
Nodular?) 

Electro - Metallurgical Reguline De- 
posit. — (See Deposit, Electro-Metallurgical 
Eeguline.) 

Electro-Metallurgical Sandy Deposit. — 

(See Deposit, Electro-Metallurgical Sandy?) 

Electro-Metallurgy.— (See Metallurgy, 
Electro?) 

Electrometer. — An apparatus for measur- 
ing differences of potential. 

Electrometers operate, in general, by means 
of the attraction or repulsion of charged conduc- 
tors on a suitably suspended needle or . disc. As 
no current is required to flow through the appa- 
ratus electrometers are especially adapted to many 
cases where voltmeters could not be so readily 
used. 

Electrometer, Absolute An elec- 
trometer the dimensions of which are such 
that the value of the electromotive force can 
be directly determined from the amount of 
the deflection of the needle. 

A form of attracted-disc electrometer. 
(See Electrometer, Attracted-Disc?) 

Electrometer, Attracted-Disc A 

form of electrometer devised by Sir William 



Thomson, in which the force is measured by 
the attraction between the two discs. 

Thomson's Attracted-Disc Electrometer is 
shown in Fig. 230. It consists of a plate C, sus- 
pended from the longer end of a lever 1, within the 
fixed guard plate, or guard ring B, immediately 
above a second plate A, supported on an insulated 
stand, and capable of a measurable approach 




Fig. 230. Attracted- Disc Electrometer. 

towards C, or a movement away from it. The 
plate, C, is placed in contact with B, by means of 
a thin wire. By means of this connection the 
distribution of the charge over the plate, C, is 
uniform. The electrostatic attraction is meas- 
ured by the attraction of the fixed disc, A, on the 
movable disc, C, connected respectively to the two 
bodies whose difference of potential is to be 
measured. One of these may be the earth. The 
fulcrum of the lever 1, is formed of an aluminium 
wire, the torsion of which is used to measure the 
force of the attraction; or, it may be measured 
directly by the counterpoise weight Q. 

This instrument is sometimes called an absolute 
electrometer, because, knowing the dimensions of 
the apparatus, the value of the difference of poten- 
tial can be directly determined from the amount 
of the motion observed. 



Electrometer, Capillary An elec- 
trometer in which a difference of potential is 




Fig. 231. Capillary Electrometer. 

measured by the movement of a drop of 
sulphuric acid in a tube filled with mercury. 



Ele.] 



206 



[Ele. 



A form of capillary electrometer is shown in 
Fig. 231, in which a horizontal glass tube with 
a drop of acid at B, has its ends connected with 
two vessels M and N, filled with mercury. If 
a current be passed through the tube, a move- 
ment of the drop towards the negative pole 
will be observed. Where the electromotive 
force does not exceed one volt, the amount of 
the movement is proportional to the electro- 
motive force. 

Electrometer, Quadrant An elec- 
trometer in which an electrostatic charge is 
measured by the attractive and repulsive 
force of four plates or quadrants, on a light 
needle of aluminium suspended within them. 

The sectors or quadrants are of brass, and are 
so shaped as to form a hollow cylindrical box 
when placed together. The four sectors, or quad- 
rants, are insulated from one another, but the 
opposite ones are connected by a conducting wire, 
as shown in Fig. 
232. A light needle < 
of aluminium, u, 
maintained at some 
constant potential, 
by connection with 
the inner coating 
of a Leyden jar, is 
suspended, gener- 
ally by two par- 
allel silk threads, 
so as to freely swing inside the hollow box. This 
needle, when at rest, is in the position shown by 
the dotted lines, with its axis of symmetry exactly 
under one of the slots or spaces between two 
opposite sectors. (See Suspension, Bi- Filar.) 

The quadrant electrometer, shown in Fig. 233, 
has one of its quadrants removed so as to show 
the suspended aluminium needle. 

A similar form of instrument is shown in Fig. 
234, with all the quadrants in place, and the 
whole instrument covered by a glass shade. 

To use the quadrant electrometer the pairs of 
sectors are connected with the two bodies whose 
difference of potential is to be measured, and the 
deflection of the needle observed, generally 
through a telescope, by means of a spot of light 
reflected from a mirror attached to the upper part 
of the needle. 

Sometimes the segments are made in the shape 
of a cylinder, and the needle in the shape of a 
suspended rectangle. 



Electrometer, Registering 



An elec- 



trometer, the deviations of the needle oi 
which are automatically registered. 




232. Quadrant Elec- 
trometer. 




Fig. 233. Quadrant Electrometer, Showing Suspended 
Needle. 

The registration of this class of electrometer is 
obtained by means of photography. The spot of 




Fig. 234. Quadrant Electrometer. 

light, reflected from the mirror of the electrometer, 
falls on a fillet of sensitized paper, moved by 

clockwork. 



Ele. 



207 



[Ele, 



Electromotive Arrangement or Device. 

— (See Arrangement or Device, Electromo- 
tive?) 

Electromotive Difference of Potential. — 
{See Potential, Difference of Electromotive?) 

Electromotive Force. — (See Force, Elec- 
tro?notive.) 

Electromotive Force, Average (See 

Force, Electromotive, Average or Mean.) 

Electromotive Force, Back or Counter 
(See Force, Electromotive. Back?) 

Electromotive Force, Direct (See 

Force, Electromotive, Direct?) 

Electromotive Force, Inductive 

(See Force, Electrojnotive, Inductive?) 

Electromotive Force, Secondary-Im- 
pressed — (See Force, Electromotive, 

Secondary-Impressed?) 

Electromotive Force, Simple-Periodic 
— (See Force, Electromotive, Simple- 
Periodic?) 

Electromotive Force, Transverse 

(See Force.. Electromotive, Transverse?) 

Electromotive Impulse. — (See Impulse, 
Electromotive?) 

Electro-Motograph. — (See Motograph, 
Electro?) 

Electro-Muscular. — (See Muscular, Elec- 
tro?) 

Electro-Muscular Excitation. — (See Ex- 
citation. Electro-Muscular?) 

Electronecrosic— Pertaining to capital 
punishment by means of electricity. 

Electron ecrosis.— A word proposed for 
capital punishment by means of electricity. 

Electro-Negative Ions. — (See Ions, Elec- 
tro-Negative?) 

Electronegatives.— The atoms or radicals 
that appear at the anode or positive terminal 
during electrolysis. 

The anions. (See Electrolysis. Anion?) 

Electro-Nervous Excitability. — (See Ex- 
citability., Electro-Nervous?) 

Electro- Nickeling. — (See Nickeling, 
Electro?) 

Electro-Optics.— (See Optics, Electro?) 



Electrophanic. — Pertaining to capital pun- 
ishment by means of electricity. 

Electrophanical. — Pertaining to capital 
punishment by means of electricity. 

Electrophanize.— To inflict capital pun- 
ishment by means of electricity. 

Electrophany. — Capital punishment by 
means of electricity. 

The word electrophany would appear to be far 
preferable to the word electrocution, since it is in 
accordance with etymological usage, while elec- 
trocution is not. 

Electrophila. — A devotee of electricity. 

Electrophobia. — A word proposed for fear 
of electricity. 

Electrophoric. — Pertaining to an electro- 
phorus. (See Electrophorus.) 

Electrophorus. — An apparatus for the 
production of electricity 
by electrostatic induc- 
tion. (See Induction, 
Electrostatic?) 

A disc of vulcanite, or 
hard rubber B, contained 
in a metallic form, is rub- 
bed briskly by a piece of 
cat's skin and the insu- 
lated metallic disc, A, is Fig. 235. Electrophorus, 
placed on the centre of the Charging. 

vulcanite disc, as shown in Fig. 235. 

The negative charge produced in B, by fric- 
tion, produces by induction a positive charge on 
the part of A, nearest it, 
and a negative charge 
on the part furthest from 
it. 

In this condition, if 
the disc be raised from 
the plate by means of its 
insulating handle, as 
shown in Fig. 236, no 
electrical effects will be 
noticed, since the two op- 
posite and equal charges 
unite and neutralize each ^%T- 2 3^> 
other. If, however, the 
disc A, be first touched by the finger, and then 
raised from the disc B, it will be found to he pos- 
itively charged. 





Electrophorus, 
Discharging. 



Ele.] 



208 



[Ele. 



E 1 e c t r o-Physiology. — (See Physiology, 
Electro?) 

Electropic Medium. — (See Medium, Elec- 
tropic) 

Electro-Plating. — (See Plating, Electro) 

Electro-Plating Bath. — (See Bath, Elec- 
tro-Plating.) 

Electro-Pneumatic Signals. — (See Sig- 
nals, Electro-Pneumatic) 

Electro-Pneumatic Thermostat. — (See 
Thermostat, Electro-Pneumatic.) 

Electropoion Liquid. — (See Liquid, Elec- 
tropoion) 

Electro-Positive Ions. — (See Ions, Elec- 
tro-Positive.) 

Electropositives. — The atoms or radicals 
that appear at the kathode or negative termi- 
nal of any source during electrolysis. 

Thekathions. (See Electrolysis. Kathion.) 

E 1 e c t r o-Prognosis. — (See Prognosis, 
Electric) 

Electro-Puncture. — (See Puncture, Elec- 
tro) 

Electro-Receptive Devices. — (See Device, 
Electro-Receptive) 

Electro-Receptive Devices, Multiple-Arc- 
Connected (See Devices, Electro- 
Receptive, Multiple-Arc-Connected) 

Electro-Receptive Devices, Multiple-Se- 
ries-Connected (See Devices, Elec- 
tro-Receptive, Multiple-Series-Connected) 

Electro-Receptive Devices, Series-Con- 
nected (See Devices, Electro-Recep- 
tive, Series-Connected) 

Electro-Receptive Devices, Series-Mul- 
tiple-Connected — (See Devices, Elec- 
tro-Receptive, Series-Multiple- Connected) 

Electroscope. — An apparatus for showing 
the presence of an electric charge, or for de- 
termining its sign, whether positive or nega- 
tive, but not for measuring its amount or 
value. 

In the gold-leaf electroscope, two gold leaves, 
n, n, Fig. 239, suspended near each other, show 
by their repulsion the presence of an electric 
charge. Two pith balls may be used for the same 
purpose. 



The pith balls B, B, shown in Fig. 237, form 
a simple electroscope. If repelled by a charge, 
when approached by a similar charge in S, they 
will at once be still further repelled, as shown by 
the dotted lines. 

To use an electroscope for determining the signoi 




Fig. 237. Pith Ball Electroscope. 

an unknown charge, the gold leaves or pith balls are 
first slightly repelled by a charge of known name, 
as, for example, positive, applied to the knob C, 
Fig. 239. They are then charged by the electrified, 
body whose charge is to be determined. If they 
are further repelled, its charge is positive. If 
they are first attracted and afterwards repelled, 
its charge is negative. 

Two posts B, Fig. 239, connected with the 
earth, increase the amount of divergence by in- 
duction. 

Electroscope, Condensing, Yolta's 

An electroscope employed for the detection 
of feeble charges, the leaves of which are 
charged by means of a condenser. 

The condensing electroscope 
formed of two metallic 
plates, placed at the 
top of the instrument, 
and separated by a 
suitable dielectric. 
The upper plate, P, is 
removable by means 
of the insulated han- 
dle, G. 

To employ the elec 
troscope, as for exam- 
ple, to detect the free 
charge in an unequal- Figm 238 r~Condensing Elec- 
ly heated crystal of troscope. 

tourmaline, the crystal is touched to the lower 
plate, while the upper plate is connected to the 
ground by the finger. On the subsequent re- 
moval of the upper plate an enormous decrease 




Ele.J 



209 



[Ele. 




ensues in the capacity of the condenser, and the 
charge now raises the potential of the lower 
plate, and causes a marked divergence of the 
leaves L, L. (See Electricity \ Pyro.) 

Electroscope, Gold-Leaf An elec- 
troscope in which two leaves of gold are used 
to detect the presence of an electric charge, 
or to determine its character whether positive 
or negative. 

When a charge is imparted to the knob C, Fig. 
239, the gold leaves n, n, diverge. This will oc- 
cur whether the charge be 
positive or negative. 

To determine the char- 
acter of an unknown 
charge, the leaves are first 
caused to diverge by means 
of a known positive or neg- 
ative charge. The un- 
known charge is then given 
to the leaves. If they di- 
verge still further, then the charge is of the same 
name as that originally possessed by the leaves. 
If, however, they first move to- 
gether and are afterwards re- 
pelled, the charge is of the 
opposite name. 

Electroscope, Pith - Ball 

— An electroscope 

which shows the presence of 
a charge by the repulsion of 
two similarly charged pith 
balls. (See Electroscope^) 

Any two pith balls, suspend- 
ed by conducting threads, but 
insulated from the earth, will 
serve as an electroscope. 

Electroscope, Quadrant, 
Henley's An electro- 
scope sometimes employed 
to indicate large charges of 
electricity. 

A pith ball placed on a light 
arm A, of straw or other simi- 
lar material, Fig. 240, is pivoted 
at the centre of a graduated 
circle B. The arm, C, is at- Fig. 240. Henley's 
tached by means of the screw Electroscope. 
to the prime conductor of an electric machine. 
The similar charge imparted to A, by contact 



Fig. 23Q. Gold- Leaf 
Electroscope . 



with C, causes a repulsion which may be meas- 
ured on the graduated arc. 

This instrument approaches the electrometer in 
the character of its operation, since by its means, 
approximately correct measurements may be made 
of the value of the repulsion. It should not, how- 
ever, be confounded with the quadrant electrom- 
eter. (Set Electrometer, Quadrant.) 

Electroscopically. — By means of the elec- 
troscope. (See Electroscope.) 

Electroscopy. — The art of determining the 
kind of charge a body possesses, by means 
of an electroscope. 

Electro - Sensibility. — (See Se7isibility, 
Electron 

Electro-Silvering. — (See Silvering, Elec- 
tro^ 

Electro-Smelting.— (See Smelting, Elec- 
tro.) 

Electrostatic Attraction. — (See Attrac- 
tion, Electrostatic.) 

Electrostatic Capacity.— (See Capacity, 
Electrostatic^) 

Electrostatic Circuit. — (See Circuit, 
Electrostatic^) 

Electrostatic Field. — (See Field, Electro- 
static^) 

Electrostatic Induction. — (See Induction, 
Electrostatic^) 

Electrostatic Induction Machine. — (See 
Machine, Electrostatic Induction.) 

Electrostatic Leakage.— (See Leakage, 
Electrostatic^) 

Electrostatic Lines of Force. — (See Force, 
Electrostatic, Lines of.) 

Electrostatic Repulsion. — (See Repulsion, 
Electrostatic.) 

Electrostatic Screening.— (See Scree?iing, 
Electrostatic^) 

Electrostatic Stress. — (See Stress, Elec- 
trostatic.) 

Electrostatic Units. — (See Units, Electro- 
static?) 

Electrostatics. — That branch of electric 
science which treats of the phenomena and 
measurement of electric charges. 



Ele.] 



210 



[Ele. 



The principles of electrostatics are embraced 
in the following laws, viz. : 

(i.) Charges of like name, i. e., either positive 
or negative, repel each other. Charges of unlike 
name attract each other. 

(2.) The forces of attraction or repulsion be- 
tween two charged bodies are directly propor- 
tional to the product of the quantities of elec- 
tricity possessed by the bodies and inversely 
proportional to the square of the distance be- 
tween them. 

These laws can be demonstrated by the use of 
Coulomb's torsion balance. (See Balance, Tor- 
sion.) 

Calling q, and q 1 , the quantities of electricity 
possessed by the two bodies, and r, the distance 
between them, then, if f, is the force exerted by 
their mutual action, 

J ■ r 2 

Electro-Technics.— (See Technics, Elec- 
tro?) 

Electrothanasing.— Producing death by 
electricity. 

Electrothanasis.— A word proposed for 
death by electricity. 

The death referred to here is death other than 
that caused by capital punishment. 

Electrothanasise. — To produce death by 
electricity. 

The death here referred to is other than that 
caused by capital punishment. 

Electrothanatose. — To cause death by 
electricity. 

Electrothanatosic. — Pertaining to capital 
punishment by means of electricity. 

Electrothanatosing. — Causing death by 
electricity. 

Electrothanatosis. — A word proposed for 
death by electricity. 

The death here referred to is death other than 
that caused by capital punishment. 

Electro-Therapeutic Bath.— (See Bath, 
Electro- Therapeutic?) 

Electro-Therapeutic Breeze. — (See 
Breeze, Electro- Therapeutic?) 



Electro-Therapeutic Diffusion of Cur- 
rent. — (See Current, Diffusion of, Electro- 
Therapeutic?) 

Electro-Therapeutic Dosage.— (S e e 
Dosage, Electro- Therapeutical?) 

Electro-Therapeutic Electrode.— (See 

Electrode, Electro- Therapeutic?) 

Electro-Therapeutic Electrodes.— (See 
Electrode, Electro- Therapeutic?) 

Electro-Therapeutic Galvanization. — 

(See Galvanization, Electro-Therapeutical?) 

Electro-Therapeutic Head-Breeze. — 

(See Breeze, Head, Electro-Therapeutic?) 

Electro-Therapeutics. — (See Therapeu- 
tics, Electro?) 

Electro-Therapeutist. — (See Therapeu- 
tist, Electro?) 

Electro-Therapy. — (See Therapy, Elec- 
tro?) 

Electro-Thermal Meter.— (See Meter, 
Electro- Thermal?) 

Electro-Tinning. — (See Tinning, Elec- 
tro?) 

Electrotisic. — Pertaining to capital pun- 
ishment by means of electricity. 

Electrotising". — Producing capital punish- 
ment by means of electricity. 

Electrotisis. — A word proposed for capi- 
tal punishment by means of electricity. 

Electrotonic Current. — (See Current, 
Electrotonic?) 

Electrotonic Effect. — (See Effect, Electro- 
tonic?) 

Electrotonic Excitability. — (See Excita- 
bility, Electrotonic?) 

Electrotonic State.— (See State, Electro- 
tonic?) 

Electrotonus.— A condition of altered 
functional activity which occurs in a nerve 
when subjected to the action of an electric 
current. 



Ele.] 



211 



[Ele. 



The electrotonic state is produced by the 
passage through a nerve of a constant current 
called the polarizing current. 

Electrotonus is attended by the modification of 
the nerve in the following respects, viz. : 

(i.) In its electromotive force. 

(2.) In its excitability. 

The passage of the constant current produces 
a change in the electromotive force of that part of 
the nerve traversed by the current. 

This alteration in muscular excitability may 
consist in either an increased or a decreased func- 
tional activity. The decreased functional activity 
occurs in the neighborhood of the anode, or the 
positive terminal, and is called the anelectrotonic 
state. The increased functional activity occurs in 
the neighborhood of the kathode, or the negative 
terminal, and is called the kathelectrotonic state. 
(See Anelectrotonus. JCathelectrotonus.) 

This altered functional activity affects not only 
the intra polar parts of the nerve, or that part 
between the electrodes, but also the extra-polar 
portions, or, in other words, the remainder of the 
nerve. 

The electrotonic state is characterized by two 
varieties, viz. : those in which the electromotive 
force of the nerve is decreased, and those in which 
the electromotive force of the nerve is increased. 
These varieties of electrotonus are called respec- 
tively the negative and positive phase of electro- 
tonus. (See Electrotonus, Negative Phase of. 
Electrotonus, Positive Phase of.) 

Electrotonus, Negative Phase of 

A decrease in the electromotive force of a 
nerve effected by sending a current through 
the nerve in the opposite direction to the 
nerve current. (See Current, Nerved) 

Electrotonus, Positive Phase of 

An increase in the electromotive force of a 
nerve effected by sending a current through 
the nerve in the same direction as the nerve 
current. 

The increase in the electromotive force not only 
affects the portions of the nerve in the intra-polar 
regions, but in the extra polar regions as well. 

Electrotype. — A type, cast, or impression 
of an object obtained by means of electro- 
metallurgy. (See Metallurgy, Electro, Elec- 
trotypmg^) 

Electrotyping, or the Electrotype Pro- 



cess Obtaining casts or copies of 

objects by depositing metals in molds by 
the agency of electric currents. 

The molds are made of wax, or other plastic 
substance, rendered conducting by coating it with 
powdered plumbago. 

The mold is connected with the negative 
battery terminal, and placed in a metallic solu- 
tion, generally of copper sulphate, opposite a 
plate of metallic copper, connected with the posi- 
tive battery terminal. As the current passes, the 
metal is deposited on the mold at the kathode, 
and dissolved from the metallic plate at the 
anode, thus producing an exact copy or cast and 
at the same time maintaining constant the strength 
of the bath. 

Electrozemia. — A word proposed for capi- 
tal punishment by means of electricity. 

Electrum. — A name given by the ancients 
to various substances that could be readily 
electrified by friction. 

The term electrum included a number of sub- 
stances, but was applied mainly either to amber 
or to an alloy of gold and silver. 

Element. — Any kind of matter which can- 
not be decomposed into simpler matter. 

Matter that is formed or composed of but 
one kind of atoms. 

Oxygen and hydrogen are elements or varie- 
ties of elementary matter. They cannot be de- 
composed into anything but oxygen or hydrogen. 
Water, on the contrary, is compound matter, 
since it can be decomposed into its constituent 
parts, oxygen and hydrogen. 

There are about seventy well-known elements, 
some of which are very rare, occurring in ex- 
tremely small quantities. 

The evidence of the true elementary condition 
of many of the elements is based, to a great ex- 
tent, on the fact that so far they have resisted all 
efforts made to decompose them into simpler sub- 
stances. We should bear in mind, however, that 
until Davy's use of the voltaic battery, potash, 
soda, and many other similar compounds were re- 
garded as true elements. It is not improbable 
that many of the now so-called elements, may 
hereafter be decomposed into simpler constitu- 
ents. 

The following table gives the names, chemical 



EIc] 



212 



[Ele. 



symbols, approximate atomic weights and equiva- 
lents of the principal elements : 



Names ot 
Elements. 



Aluminium . , 
Antimony ... 

Arsenic , 

Barium , 

Beryllium ... 
Bismuth.... . 

Boron 

Bromine 

Cadmium.. .. 
Caesium. ... 
Calcium .. 

Carbon 

Cerium 

Chlorin .... 
Chn mium . . 

Cobalt 

Copper 

Didymium... 

E bmm 

Fluorine 

Gallium 

Germanium.. 
Glucinum. .., 

Goid 

Hydrogen ... 

lnuium 

Iodine ....... 

Iridium 

Iron 

Lanthanum.. 

Lead 

Lithium 

Magnesium.. 
Manganese.. 

Mercury 

M olybdenum 

Nickel 

Niobium. ... 
Nitrogen 

Osmium 

Oxygen .... 
Palladium... 
Phosphorus. . 

Platinum 

Potassium.... 
Rhodium ... 
Rubidium ... 
Ruthenium... 
Samari'im ... 
Scandium . .. 

Selenium 

Silicon. 

Silver 

Sodium 
Strontium ... 

Sulphur 

Tantalum. . .. 
Tellurium .. . 
Thallium .... 
Thorium . .. 

Tin 

Titanium 

Tungsten.... 
Uranium 
Vanadium ... 
Ytterbium... 

Yttrium 

Zmc 

Zirconium.... 



Al. 

Sb. 

As. 

Ba. 

Be. 

Bi. 

B. 

\'r. 

Cd 

Cs. 

Ca. 

c. 

Ce. 

CI. 

Cr. 

Co 

Cu. 

D 

E. 

F. 

Ga. 

Ge. 

G. 

Au. 

H. 

In. 



Fe. 

La. 

Pb. 

Li. 

Mg. 

Mn. 

Hg. 

Mo. 

Ni. 

Nb. 

N. 

Os. 

O. 

Pd. 

P. 

Pt. 

K. 

R. 

Rb. 

Ru. 

Sm. 

Sc. 

Se. 

hi. 

Ag. 

Na. 

Sr. 

S. 

Ta. 

Te 

Tl. 

Th. 

Sn. 

Ti. 

W. 

U. 

Va. 

Yd. 

Y. 

Zn. 

Zc. 



o 2'3 



27. 
120. 

74-9 

136.8 

9.1 

207.5 

10.9 

79.8 

in. 8 

132.6 

40. 

12. 

140.4 

3S-4 

52- 

58 9 

63., 

144.6 

165.9 

19. 

68.9 

72-3 

196.2 

1. 
"3-4 
126.6 
192.7 
55-9 
138.5 
206.5 

7- 

a 4 . 

53-9 
199.7 

95-5 

57-9 

93-8 

14. 
198.5 

16. 
105.7 

3i- 
194.4 

39- 1 
104. 1 

85-3 
104.2 
150.02 
44. 
78.8 
28.2 
107.7 
23- 
87.4 

32- 

182. 1 

128. 

203.7 

233-4 
117. 7 
48. 
183.6 
238.5 
5*-3 
172.8 
89.8 
64.9 
89.4 



Chemical Equivalent.* 



9 _ [compounds 

40 in ous, 24 in zV 
24.9 in ous, 15 in ic 
68.4 

4.6 
69.2 

3-6 
79.8 

55-9 
66.3 



35-4 

26 mous, 17.3 in ic 

29.5 

3i-6 



196.2 \nous, 65.4 in ie 

37-8 
126.6 

9.). 4. 64.2, 48.2 
20 in ous, 18.6 in ie 

to3-3 
7 



199 . 7 in ous, 99 . 9 in ic 
28 



52 . 9 in ous, 26 . 4 in ic 

6. a in pnosphates 
97 . 2 in ous, 48 . 6 in ic 

39- 

52 in ous, 34.7 in te 

8 5-3. 

52.1 in ous t 34 . 7 in ic 



7- 
107.7 
23 
43-7 



203 . 7 in ous, 67.9 in ic 

58 . 9 in ous, 29 . 4 in ic 
24 in ous, 12 in ic 
91.8 in o us 
1 19. 2 in ous 
17. 1 iaous 



3 2 -5 



* Atomic weight divided by the valency. 



Element, Negative — One of the 

substances forming a voltaic couple. (See 
Couple, Voltaic?) 
Element, Negative, of a Toltaic Cell 

— That element or plate of a voltaic cell into 
which the current passes from the exciting- 
fluid of the cell. 

The plate that is not acted on by the elec- 
trolyte during the generation of current by 
the celL 

The copper or carbon plate, respectively, 
in a zinc-copper or zinc-carbon couple. 

It must be carefully borne in mind that the 
conductor attached to the negative element of a 
voltaic pile is the positive conductor or electrode 
of the pile, since the current that flows into the 
plate from the liquid or electrolyte must flow out 
of the plate where it projects beyond the liquid. 

Element of Current. — (See Current, Ele- 
ment of.) 

Element of Storage Battery. — (See Bat- 
tery, Storage, Element of.) 

Element, Positive That element or 

plate of a voltaic cell from which the current 
passes into the exciting fluid of the cell. 

The element of a voltaic couple which is 
acted on by the exciting fluid of the cell. 
(See Couple, Voltaic.) 

Element, Thermo-Electric One of 

the two metals or substances which form a 
thermo-electric couple. (See Couple, Ther- 
mo-Electric?) 

Element, Toltaic One of the two 

metals or substances which form a voltaic 
couple. (See Couple, Voltaic?) 

Elements, Electrical Classification of 

A classification of the chemical ele- 
ments into two groups or classes according 
to whether they appear at the anode or kathode 
when electrolyzed. 

The chemical elements may be arranged into 
electro-positive and electro-negative according to 
whether, during electrolysis, they appear at the 
negative or positive terminal of the source respec- 
tively. 

The electro-positive elements or radicals are 
called kathions, and appear at the kathode or 
electro-negative terminal. The electro-negative 



EL .J 



213 



[Ene. 



elements are called anions, and appear at the 
anode, or the electro-positive terminal. (See 
Ions.) 

The metals generally are electro-positive; oxy- 
gen, chlorine, iodine, fluorine, etc., are electro- 
negative. 

Elements, Magnetic, of a Place 



The values of the magnetic intensity, the mag- 
netic declination or variation, and the mag- 
netic inclination or dip at any place. 

Elevator Annunciator. — (See Annuncia- 
tor, Elevator.) 

Elevator, Electric An elevator 

operated by electric power. 

Elongated Ring Core. — (See Core, Ping, 
Elongated?) 

Elongation, Magnetic An increase 

in the length of a bar of iron on its magnetiza- 
tion. 

This increase in length is thought to greatly 
strengthen Hughes' theory of magnetism. (See 
Magnetism, Hughes' 1 Theory of.) 

Elongation of Needle. — (See Needle, Eton- 
g-ation of.) 

Embosser, Telegraphic An appa- 
ratus for recording a telegraphic message in 
raised or embossed characters. 

Emptied. — A term sometimes applied to a 
completely discharged secondary or storage 
cell. 

It is difficult to determine exactly when a stor- 
age cell is completely emptied or " discharged ." 
The cell is generally regarded as discharged 
when its voltage falls below a certain point. 

Endosmose. — The unequal mixing of two 
liquids or gases through an interposed me- 
dium. 

The presence of an electric current affects the 
endosmose. (See Currents, Diaphragm.) 

Endosmose, Electric. — Differences in the 
level of liquids capable of mixing through the 
pores of a diaphragm separating them, pro- 
duced by the flow of an electric current 
through the liquid. 

Wiedemann, who investigated these phenom- 
ena, employed a porous earthenware vessel closed 
at the bottom and terminated at its upper end by 
a o-lass bell provided with a glass tubulure, to 



which was attached a horizontal arm for the es- 
cape of the liquid raised in the tubulure. The 
battery terminals were attached to platinum elec- 
trodes placed respectively inside the porous cell, 
and in a vessel of water outside of the porous cell, 
in which the porous cell was placed ; on the passage 
of the current from the outside of the cell to the 
inside the liquid rose in the glass tubulure and ran 
over the horizontal tube into a vessel placed ready 
to receive it. 

Energizing, Electrically Causing 

electricity to produce any effect in an electro- 
receptive device. 

An electro-magnet is energized by the passage 
of a current through its coils. 

Energy. — The power of doing work. 

The amount of work done is measured by the 
product of the force, by the space through which 
the force moves. Thus one pound raised verti- 
cally through ten feet, ten pounds raised through 
one foot, or five pounds raised through two feet, alL 
represent the same amount of work; viz., ten foot- 
pounds. 

If a weight of ten pounds be raised through a 
vertical height of one foot, by means of a string 
passing over a pulley, there will have been ex- 
pended an amount of energy represented by the 
work often foot-pounds. If the weight be pre- 
vented in any way from falling, as by securing 
the string to a fixed support, the weight will have 
stored in it an amount of energy equal to ten foot- 
pounds, and if permitted to fall, will be capable 
of doing an amount of work which, leaving out air 
resistance and friction, is exactly equal to that 
originally expended in raising it to the position 
from which it fell; viz., ten foot-pounds of work. 

Energy, Actual Energy actually 

employed in doing work as distinguished 
from energy that only possesses the power of 
doing work, but not actually doing such 
work. 

This term is also used in the sense of kinetic 
energy or energy due to motion, but kinetic en- 
ergy is no more actual than potential energy. 

Energy, Atomic Chemical-potential 

energy. (See Energy, Ckemzcal-Potential.) 
Energy, Chemical-Potential The 

potential energy possessed by the elementary 
chemical atoms. (See Energy, Potential.) 
If a weight of one pound be raised vertically 



Ene.] 



214 



[Ene. 



against the earth's attraction, through a distance 
of say ten feet, and placed on a suitable support, 
an amount of energy, equal to the ten foot-pounds 
of work done on the weight, becomes potential. 

In the same manner if the elementary atoms of 
carbon and oxygen, when combined so as to form 
carbonic acid, are raised or separated from one 
another sufficiently to decompose the carbonic 
acid and separate the carbon from the oxygen, the 
amount of potential energy the carbon and oxygen 
possess, as a result of having been separated, is 
equal precisely to that originally required to sepa- 
rate them. In this manner each chemical element 
possesses a store of chemical potential energy 
peculiar to it, and any element with which it may 
subsequently enter into combination. When ele- 
ments combine chemically this potential energy is 
expended in producing heat. 

Energy, Conservation of The in- 
destructibility of energy. 

The total quantity of energy in the universe is 
unalterable. 

The total energy of the universe is not, how- 
ever, available for the production of work useful 
for man. 

When energy disappears in one form it reap- 
pears in some other form. This is called the con- 
servation or indestructibility of energy. The com - 
monest form in which energy reappears is as heat, 
and in this case some of the heat is lost to the 
earth by radiation. This degradation or dissipa- 
tion of energy causes some of the energy of the 
earth to become non-available to man. 

Energy is therefore available and non-available. 
(See Entropy.) 

Energy, Correlation of A term 

sometimes applied to the different phases un- 
der which energy may appear. 

Since energy is indestructible, when it disap- 
pears in one form or pha^e, it must reappear in 
another form or phase. The correlation of the 
different phases of energy, therefore, necessarily 
follows from the fact that all energy is indestruc- 
tible. 

Energy, Degradation of Such a 

dissipation of energy as to render it non- 
available to man. (See Energy, Co?iserva- 
tion of. Entropy?) 

Energy, Dissipation of The ex- 
penditure or loss of available energy. 



Energy, Electric —The powei 

which electricity possesses of doing work. 

In the case of a liquid mass at different levels, 
the liquid at the higher level possesses a certain 
amount of potential energy measured by the 
quantity of the liquid at the higher level, and the 
excess of its height over that of the lower level; 
or, by the difference between the two levels. Any 
difference of level will produce a flow of the liquid 
from the higher to the lower level, and during 
the flow of this current of liquid, potential energy 
will be lost, and a certain amount of work will be 
done. 

In the case of electricity, the difference of elec- 
tric level, ox potential, between any two points of 
a conductor, causes an electric current to flow 
between these points toward the lower electric 
level, during which electric potential energy is 
lost, and work is accomplished by the electric 
current. (See Potential, Electric.') 

The amount of this electric work is measured by 
the quantity of electricity that flows, multiplied 
by the difference of potential under which it 
flows. (See Joule. Volt-Coulomb.) 

Electric energy, however, is generally meas- 
ured in electric power, or rate of doing electric 
work. 

Since an ampere is one coulomb-per-second, if 
we measure the difference of potential in volts, 
the product of the amperes by the volts will give 
the electrical power in volt -amperes, or watts, or 
■units of electric power. C E = Watts. (See 
Ampere. Volt. Watt.) 

One horse-power equals 550 foot-pounds per 
second. One watt or volt-ampere = T |g of a 
horse-power, or one horse-power equals 746 volt 
amperes or watts, therefore: 

The current in amperes, multiplied by the dif- 
ference of potential in volts, divided by 746, 
equals the rate of doing work in horse-powers. 

Thus, if .7 ampere is required to operate a 
16 candle, no volt, incandescent lamp, it requires 
4.8 watts per candle. 

One Watt = 44.2394 foot-pounds per minute. 

One Watt = .737324 foot-pound per second. 

The Beat Activity, or the heat-per-second 
produced by an electric current, is also propor- 
tional to the product C E, or the watts, for the 
heat is proportional to the square of the current 
in amperes multiplied by the resistance in ohms, 
or C 2 R = the watts. (See Calorimeter, Elec- 
tric.) 



Ene.] 



215 



[Ene. 



By Ohm's Law (See Ohm's Law) 
E 



= ^ (i), or C R 



E(2), 



But the electric power, or the watts, = C E (3). 
If, now, we substitute the value of E, taken 
frcm equation (2) in equation (3) we have 
CE = CXCR = C2R; 

therefore C2R = Watts. 

To determine the heating power of a current 
in small calories, calling H, the amount of heat 
required to raise I gramme of water through i° 
Cent., and C, the current in amperes — 

H = C 2 R X .24. 
Or, for any number of seconds, I, 

H = C 2 R* X .24. 
(See Calorie.) 

But from Ohm's Law, 
E 



C^= 



R 



(1), 



and the formula for electric power or the watts 
= C E. (2) By substituting in equation (2) 
and the value of C, in equation (1), 



C E = Ex 



R 



E 2 

IT 



Watts. 



That is to say, the electric power in any part of 
a circuit varies directly as the square of the 
electromotive force. 

We, therefore, have three expressions for the 
value of the watt, or the unit of electric power , 
viz. : 

C E = Watts. (1) 
C 2 R = Watts. (2) 

E2 



R 



= Watts. 



(3) 



(1.) CE = Watts; or the electric power is pro- 
portional to the product of the quantity of elec- 
tricity per-second, that passes, in amperes, and 
the difference of electric potential or levels 
through which it passes, in volts. 

(2.) C 2 R = Watts; or the electric power 
varies directly as the resistance R, when the cur- 
rent is constant, or as the square of the current, 
if the resistance is constant. That is to say, if 
with a given resistance the power of a given 
current has a certain value, and the current 
flowing through this same resistance be doubled, 
the power is four times as great, or is as the 
square of the current. 

E 2 

(3.) jf = Watts, or the electric power is in- 



versely as the resistance R, when the electro- 
motive force is constant, and is directly propor- 
tional to the square of the electromotive force if 
the resistance is constant. 

A circuit of one ohm resistance will have a 
power of one watt, when under an electromo- 
tive force of one volt, since it would then have 
a current of one ampere flowing through it, and 
C E = 1. If, however, the resistance be halved 
or becomes .5 ohm, then two amperes pass, or 
the power equals 2 watts. 

The power varies as the square of the electro- 
motive force in any part of a circuit, when the 
resistance is constant in that part. Thus 2 am- 
peres, and 2 volts, in a circuit of one ohm 
resistance, give a power, C E = 2 X 2 =4 watts. 
If now, R, remaining the same, the electro- 
motive force be raised to 4 volts, then since E, is 
doubled, C, or the amperes, is doubled, and C 

E 2 16 
XE = 4X4=i6 watts, or -p- = — = 16. 
R I 

Energy, Electric, Transmission of ■ 

— The transmission of mechanical energy be- 
tween two distant points connected by an 
electric conductor, by converting the me- 
chanical energy into electrical energy at one 
point, sending the current so produced 
through the conductor, and reconverting the 
electrical into mechanical energy at the other 
point. 

A system for the electric transmission of energy 
embraces: 

(1.) A conducting circuit between the two 
stations. 

(2.) An electric source or battery of electric 
sources or machines at one of the stations, gener- 
ally in the form f a dynamo-electric machine 
or machines, for converting mechanical energy 
into electric energy. 

(3.) Electro-receptive devices, generally electric 
motors, at the other station for reconverting the 
electric into mechanical energy. (See Motor, 
Electric. ) 

Energy, Flow of The flow or trans- 
mission of energy from the medium or die- 
lectric surrounding a conductor which is 
directing a current of electricity on to the 
conductor. (See Law, Poynlz'ng's.) 

Energy, Hysteresial, Dissipation of 

— The dissipation of energy by means of 



Ene.] 



213 



[Ent. 



hysteresis. (See Energy, Dissipation of. 
Hysteresis) 

Energy, Kinetic Energy which is 

due to motion as distinguished from potential 
energy, (See Energy, Potential) 

Energy-Meter.— (See Meter, Energy) 

Energy of Position.— (See Position, En- 
ergy of.) 

Energy of Stress.— (See Stress, Energy 
of.) 

Energy, Potential Stored energy. 

Potency, or capability of doing work. 

Energy possessing the power or potency of 
doing work, but not actually performing such 
work. 

The capacity for doing work possessed by 
a body at rest, arising from its position as 
regards the earth, or from the position of its 
atoms as regards other atoms, with which it 
is capable of combining. 

A pound of coal, if raised vertically one foot, 
possesses, as a mere weight, an amount of energy 
capable of doing an amount of work equal to one 
foot-pound. The atoms of carbon, however, of 
which it is composed, have been raised or sepa- 
rated from those of oxygen, or some other elemen- 
tary substance, and when the coal is burned, or 
the carbon atoms fall towards the oxygen atoms 
(i. e., unite with them), the coal gives up the 
potential energy of its atoms in the form of heat. 

All elementary substances possess in the same 
way atomic or chemical-potential energy^ or the 
energy with which they tend to fall together, 
or enter into combination. This energy varies in 
amount in different elements and becomes kinetic, 
as heat, on combination with other elements. (See 
Energy, Chemical- Potential.) 

Energy, Radiant Energy trans- 
ferred to or charged on the universal ether. 

Radiant energy is of three forms, viz.: 
(i.) Obscure radiation, or heat. 
(2.) Luminous radiation, or light. 
(3.) Electro-magnetic radiation. 

Energy, Static — A term used to ex- 
press the energy possessed by a body at rest, 
resulting from its position as regards other 
bodies, in contradistinction to kinetic energy 
or the energy possessed by a body whose 



atoms, molecules or masses are in actual 

motion. 

Potential energy. 

The general term for static energy is potential 
energy. (See Energy, Potential.) 

Energy, Storage of —The change 

from any form of kinetic energy, to any form 
of potential energy. (See Energy. Kinetic. 
Energy, Potential) 

Engine, Electro-Magnetic A mo- 
tor whose driving power is electricity. (See 
Motor ; Electric) 

Engraving, Acoustic — Engraving 

by the human voice. 

In the Phonograph, Graphophone and Gramo~ 
phone, a diaphragm, set in vibration by the 
speaker's voice, cuts or engraves a record of its 
to-and-fro movements on a sheet of tin foil, a 
cylinder of hardened wax, or a specially coated 
plate of metal or glass. This record is employed 
in order to reproduce the speech. (See Phonograph. ) 

Engraving, Electric — A method 

for electrically etching or engraving a me- 
tallic plate by covering it with wax, tracing 
the design on the wax so as to expose the 
metal, connecting the metal with the positive 
terminal of a battery, and placing it in a 
bath opposite another plate of metal. 

By the action of electrolysis the metal is dis- 
solved 'from the exposed portions and deposited 
on the plate connected with the other terminal 
of the battery. (See Electrolysis.) 

In this manner the design is obtained in the 
form of an etching or cutting of the plate. 

By connecting the waxed plate to the negative 
terminal of the electric source, the metal will be 
deposited on the exposed portions of the plate, 
thus producing the design in relief. Unless 
great care is taken, this latter method is not, 
however, apt to produce a sufficiently uniform 
deposit to enable the plate so formed to be used 
for printing from. 

Electric engraving is sometimes called electro- 
etching. 

Entropy. — In thermo-dynamics the non- 
available energy in any system. — {Clausius 
and Mayer) 

In thermo-dynamics, the available energy 
in any system. — ( Tail, Thomson and Max- 
well) 



Ent.] 



217 



[Equ, 



As will be noticed, this term is used in entirely 
different and opposite senses by different scientific 
men. The latter sense is, perhaps, the one most 
generally taken. 

Heat energy is available for doing useful exter- 
nal work only when the source of heat utilized is 
hotter than surrounding bodies, that is, when the 
heat is transferred from a hotter to a colder body. 
When all bodies have acquired the same temper- 
ature, they can do no more external work. In 
the various transformations of energy some of the 
energy is converted into heat, and this heat is 
gradually diffused through the universe and thus 
becomes non-available to man. Therefore, the 
entropy of our earth is decreasing. 

"Entropy, in thermodynamics," says Max- 
well, "is a quantity relating to a body such that 
its increase or diminution implies that heat has 
entered or left the body. The amount of heat 
which enters or leaves the body is measured by the 
product of the increase or diminution of entropy 
into the temperature at which it takes place." 

Entropy, Electric — A term pro- 
posed by Maxwell for use in thermo-elec- 
tric phenomena to include the doctrine of 
entropy in electric science. 

"When an electric current," says Maxwell, 
"passes from one metal to another, heat is 
emitted or absorbed at the junction of the metals. 
We should, therefore, suppose that the electric 
entropy has diminished or increased when the 
electricity passes from one metal to the other, the 
electric entropy being different according to the 
nature of the medium in which the electricity is, 
and being affected by its temperature, stress, 
strain, etc." 

Equalizer, Feeder An adjustable 

resistance placed in the circuit of a feeder for 
the purpose of regulating the difference of 
potential at the junction box. 



Equalizer, Magnetic 



-A device for 



equalizing the otherwise unequal force ex- 
erted between a magnet pole and its arma- 
ture at varying distances. 

Since the force of magnetic attraction increases 
rapidly with the decrease of the distance, it fol- 
lows that any force sufficiently great to cause the 
motion of an armature towards a pole, against the 
force of gravity, will result in the movement of the 
armature to the pole, and that, therefore, no dif- 
ferentiation as to the final result will be produced 



by a powerful current, and a current just strong 
enough to start the action. If, however, the 
armature move against the action of a spring, the 
latter can be so arranged that the force with 
which it opposes the motion of the armature in- 
creases, the nearer the armature is to the pole, 
and in this way the movement of the armature 
can be made proportional to the strength of the 
current energizing the electro-magnet. 

A similar method consists in mechanical devices 
that cause the armature to work with lessened 
mechanical advantage as it approaches the pole. 

Or, the polar surfaces may be so shaped by cut- 
ting, or by the addition of suitable projections, 
as to cause the approach of the armature to be 
attended by a nearly constant force. 

Equator, Geographical An imag- 
inary great circle passing around the earth 
midway between its poles. 

Equator, Magnetic ■ — The magnetic 

parallel or circle on the earth's surface where 
a magnetic needle, suspended so as to be free 
to move in a vertical as well as in a horizontal 
plane, remains horizontal. 

An irregular line passing around the earth 
approximately midway between the earth's 
magnetic poles. (See Dip or Inclination, 
Angle of.) 

Equator of Magnet. — (See Magnet, Equa- 
tor of) 

Equatorial.— Pertaining to the equator. 

Equatorially. — In the direction of the 
equator. 

Equipotential Surface of a Conductor 
through which a Current is Flowing. — 
(See Surface, Equipotential, of a Conductor 
through which a Current is Flowmg) 

Equipotential Surface, or Level Surface 
Of Escaping Fluid. — (See Surface, Equipo- 
tential, or Level Surface of Escaping Fluid) 

Equipotential Surfaces,Electrostatic 

— (See Surfaces, Equipotential, Electro- 
static) 

Equipotential Surfaces, Magnetic 

— (See Surfaces, Equipotential, Magnetic) 

Equivalence, Electro-Chemical, Law of 
— The amount of chemical action pro- 
duced by an electric current, passed through 
various chemical substances, is proportional 
to the chemical equivalent of each substance, 



Equ.] 



218 



[Equ- 



that is, to its atomic weight, divided by its 
valency. (See Valency.) 

Thus, the atomic weight of oxygen is sixteen 
times greater than the atomic weight of hydrogen. 
Oxygen is a diad; that is, has twice the combin- 
ing power of hydrogen. The passage of a given 
quantity of electricity will liberate eight times, by 
weight, as much oxygen as hydrogen; or, to put 
it in another way, the passage of a given quan- 
tity of electricity will liberate two atoms of 
hydrogen for every atom of oxygen. 

The atomic weight of chlorine is 35.4. The 
passage of a given amount of electricity will 
liberate a weight of chlorine 35.4 greater than the 
weight of hydrogen; or, for every atom of 
chlorine it will liberate one atom of hydrogen. 
Here the passage of a given amount of electricity 
liberates one atom of the monad element hydrogen 
for every atom of the monad element chlorine. 

The atomic weight of gold is 196.2, and its 

atomicity or valency is 3. The passage of a 

196.2 
given amount of electricity will liberate — -— = 

65.4 in ic compounds as great a weight of the 
triad element gold as of hydrogen ; or, will liberate 
them in the proportion of one atom of gold for 
every three atoms of hydrogen. 

Generalizing, it appears, therefore, that the 
passage of the same quantity of electricity through 
an electrolyte liberates the same number of atoms 
of a monad element, no matter what their nature 
may be. It liberates one-half as many of the diad 
atoms as it does of the monads, and one-third as 
many of the triad atoms as of the monads. 

Professor Lodge points out, that assuming the 
truth of the theory that a current of electricity 
flows in an electrolyte by means of a true electric 
convection, each atom carrying an electric 
charge, then it would seem that every monad 
atom carries an equal charge of electricity, 
whether it be an atom of hydrogen, chlorine, 
potassium, silver, or mercury. That each diad 
element carries twice as much-, and that each 
triad element carries three times as much. 

In general, the number of atoms liberated by a 
given current of electricity is equal to the num- 
ber of atoms of hydrogen, divided by the valency 
of the atom. ' ' The electric charge, ' ' says Lodge, 
" belonging to each atom of matter, is a simple 
multiple of a definite quantity of electricity, which 
quantity is an absolute constant, quite independent 
of the nature of the particular substance to which 
the atom belongs." 



The specific charge thus hypothetically given to 
each atom of matter is believed never to be lost. 

Atoms capable of entering into combination are 
supposed to be oppositely charged, and chemical 
affinity is, according to this supposition, believed 
to be the result of the mutual attractions of opposite 
electric charges naturally and originally pos- 
sessed by the atoms of matter. 

Lodge points out the following results which 
naturally flow from the hypothesis that the atoms 
of matter possess definite positive and negative 
charges of electricity, viz.: 

(1.) That the amount of electricity possessed 
by each monad atom is exceedingly small, being 
about the hundred thousand millionth part of 
the ordinary electrostatic unit, or less than the 
hundred trillionth of a coulomb. 

(2.) The charge being small, the potential is 
necessarily low. 

Probably something between one and three 
volts is a high difference of potential between two 
oppositely charged atoms. 

(3.) The nearness of the attracting atoms, how- 
ever, can cause a very strong electrostatic attrac- 
tion between them. 

(4. ) That chemical affinity, or atomic attraction, 
is caused by the presence of these electric charges. 
(5.) That the electrical force between two 
atoms at any distance is ten thousand million 
billion billion times greater than their gravitation 
attraction at the same distance, or, the force has 
an intensity per unit of mass capable of producing 
an acceleration, nearly one trillion times greater 
than that of gravity at the earth's surface. 

Equivalent, Chemical The quo- 
tient obtained by dividing the atomic weight 
of any elementary substance by its atomicity. 
(See Weight, Atoinic. Atomicity?) 

The ratio between the quantity of an ele- 
ment and the quantity of hydrogen it is 
capable of replacing. 

That quantity of an elementary substance 
that is capable of combining with or replac- 
ing one atom of hydrogen. 

The chemical equivalent has a different value 
from the atomic weight whenever the valency 
is greater than unity. Thus the atomic weight 
of gold is 196.2, but since in ic compounds one 
atom of gold is capable of combining with three 
atoms of hydrogen, the weight of the gold equiva- 
lent to that of one atom of hydrogen is one- third 
of 196.2, or 65.4. 



Equ.] 



219 



[Esc. 



Equivalent Conductivity.— (See Conduc- 
tivity, Equivalent) 
Equivalent, Electro-Chemical A 

number representing the weight in grammes 
of an elementary substance liberated during 
electrolysis by the passage of one coulomb of 
electricity. (See Electrolysis. Coulomb) 

The chemical equivalent of a substance 
multiplied by the electro-chemical equivalent 
of hydrogen. 

The electro-chemical equivalent is, therefore, 
found by multiplying the electro-chemical equiva- 
lent of hydrogen by the chemical equivalent of 
the element. 

It may be determined experimentally that one 
coulomb of electricity, expended electrolytically, 
will liberate .0000105 gramme of hydrogen.' 
Therefore a current of one a?npere % or one coulomb - 
j)er -second, will liberate .0000105 gramme of hy- 
drogen per second. The number .0000105 * s the 
electro-chemical equivalent of hydrogen. 

In the same manner the electro-chemical equiva- 
lents of the other elements are obtained by multi- 
plying the electro-chemical equivalent of hydrogen 
by the chemical equivalent of the substance. 

Thus, the chemical equivalent of potassium is 
39. 1, therefore its electro-chemical equivalent is 
39.I X .0000105 = .00041055. By multiplying 
the strength of the current that passes by the 
electro-chemical equivalent of any substance we 
obtain the weight of that substance liberated by 
electrolysis. (See Equivalence, Electro- Chemical, 
Law of.) 

To determine the electro-chemical equivalent 
of the other elements see table of chemical equiva- 
lents on page 212. 

Equivalent, Joule's The mechan- 
ical equivalent of heat. (See Heat, Mechan- 
ical Equivalent of.) 

Equivalent of Heat, Mechanical 

(See Heat, Mechanical Equivale7it of.) 

Equivalent Resistance.— (See Resistance, 
Equivalent) 

Equivolt.— A term proposed by J. T. 
Sprague for the unit of electrical energy, ap- 
plied especially to chemical decomposition. 

Sprague defines an equivolt as follows : "The 
mechanical energy of one volt electromotive force 
exerted under unit conditions through one equiva- 
lent of chemical action in grains." 



This term has not been generally accepted. 
(See Volt -Coulomb. Joule.') 

Erb's Standard Size of Electrodes. —(See 
Electrodes, Erb's Standard Size of.) 

Erg". — The unit of work, or the work done 
when unit force is overcome through unit 
distance. 

The work accomplished when a body is 
moved through a distance of one centimetre 
with the force of one dyne. (See Dyne) 
A dyne centimetre. 

The work done when a weight of one gramme 
is raised against gravity through a vertical height 
of one centimetre is equal to 981 ergs, because 
the weight of one gramme is 1 X 981 dynes, or 
981 ergs. 

The following values for the erg, the unit of 
work, and the dyne, the unit of force, are taken 
from Hering: 

1 erg = 1 dyne centimetre. 
1 erg = 0.0000001 joule. 
981 ergs = 1 gramme centimetre. 
1,937.5 ergs = 1 foot grain. 
13,562,600 ergs — 1 foot-pound. 

1 dyne = 1. 0194 milligrammes. 
I dyne = 0.015731 grain. 
I dyne = 0.0010194 grammes. 
I dyne = 0.00003596 ounce avoirdupois. 
63.568 dynes = I grain. 
981 dynes = 1 gramme. 

Ergmeter. — An apparatus for measuring 
the work of an electric current in ergs. 

Erg-ten. — A term proposed for ten million 
ergs or 1 X 10 10 = 10,000,000,000. 

In representing large numbers containing many 
ciphers the following plan is generally adopted for 
representing the number of ciphers that are to be 
added to a given number. Thus, suppose it is 
desired to represent the number 3,800,000,000. 
When written 38 X io 8 it indicates that 38 is to 
be multiplied by io 8 or 100,000,000, or, in other 
words, that 38 is to be followed by 8 ciphers, 
thus 3,800,000,000. 

A negative exponent, as 3 X i°~ 8 represents 
the corresponding decimal thus, .00000003. 

I erg X io 10 , or 10,000,000,000 is called an 
erg-ten. 1 X i° 6 = an erg-six. These terms 
are not in general use. Ten meg-ergs is a pref- 
erable phrase to an erg-ten. (See Meg-erg: ) 

Escape, Electric A term some- 



Esc] 



220 



[Eva. 



times employed to indicate the loss of charge 
on an insulated conductor. (See Leakage, 
Electric?) 

Escaping Fluid, Flow-Lines of 

(See Flow-Lines of Escaping Fluid.) 

Escaping' Fluid, Stream-Lines of 

(See Stream-Lines of Escaping Fluid?) 

Essential Resistance. — (See Resistance, 
Essential?) 

Etching, Electro A term some- 
times employed instead of electro-engraving. 
(See Engraving, Electric?) 

Electro-En- 



Etching, Galvanic 

graving. (See Engraving, Electric?) 

Ether. — The tenuous, highly elastic fluid 
that is assumed to fill all space, and by vibra- 
tions or waves in which light and heat are 
transmitted. 

Although the existence of the ether is assumed 
in order to explain certain phenomena, its actual 
existence is very generally credited by scientific 
men, and, in reality, proofs are not wanting to 
fairly establish such existence. 

Light and heat are believed to be due to trans- 
verse vibrations in the ether. Magnetism appears 
to be due to whirls or whirlpools, and an elec- 
tric current is believed by some to be due to 
pulses of waves of ether set in motion by differ- 
ences in the ether pressures. 

It is not correct to regard the luminiferous 
ether as possessing no weight, or as being im- 
ponderable. Maxwell estimates its density as 
936 



that of water. It 

1 , 000, 000, 000, 000, 000, 000, 000 

is very readily moved or set into vibration, its 

rigidity being estimated at about 

& J & 1,000,000,000 

that of steel. 

According to the speculations of some physi- 
cists the ether is not discontinuous or granular, 
but it is similar to what might be regarded as an 
almost impalpable jelly. 

Ethereal. — Pertaining to the universal 
ether. 

Eudiometer. — A voltameter in which sep- 
arate graduated vessels are provided for the 
reception and measurement of the gaseous 
products evolved during electrolysis. (See 
Voltameter?) 




In all cases electrodes for eudiometers must be 
used which do not enter into combination with the 
evolved gaseous products. In the case of oxygen 
and hydrogen, platinum is generally used. 

A form of eudiometer is shown in Fig. 241. 
Two separate glass ves- 
sels, provided at the top 
with stop cocks, and 
open at their lower 
• ends, rest in a vessel of 
water A, over platinum 
electrodes, connected 
electrically with binding 
posts K, K. Both ves- 
sels are filled with water 
slightly acidulated with 
sulphuric acid, and, 
when connected with 
a battery of sufficient 
electromotive force (not 
less than 1.45 volts), 
electrolysis takes place, Fig. 241. Eudiometer. 
and hydrogen gas collects in the vessel over 
the platinum electrode connected with the neg- 
ative battery terminal, and oxygen in the vessel 
over the electrode connected with the positive 
battery terminal. The volume of the hydrogen 
is approximately twice as great as that of the 
oxygen. (See Water, Electrolysis of.) 

The proportion is not exactly 2 to 1 , because, 

(I.) Some of the hydrogen is occluded or ab- 
sorbed by the platinum electrode. 

(2.) Some of the oxygen is given off as tri- 
atomic oxygen, or ozone, which is denser and 
occupies less space than free atomic oxygen. 

Eudiometric. — Pertaining to the eudiom- 
eter. (See Eudiometer?) 

Eudiometrically. — By means of the eudi- 
ometer. 

Evaporation.— The change from the liquid 
to the vaporous state. 

Wet clothes exposed to the air are dried by the 
evaporation of the water. 

Evaporation is greater: 

(1.) The more extended the surfaces exposed. 

(2.) The higher the temperature of the air. 

(3.) The dryer the air, or the smaller the 
quantity of vapor it contains already. 

(4.) The stronger the wind. 

(5.) The smaller the barometric pressure. 

Evaporation, Electric The forma- 



Hva.] 



221 



LExc. 



lion of vapors at the surfaces o* substances 
by the influence of negative electrification, 

The term electric evaporation was proposed by 
Crookes for the formation of metallic vapors of 
such substances as metallic platinum, exposed in 
"high vacua to the effects of negative electrifica- 
tion, He shows that under these circumstances 
the surface molecules of the platinum lose their 
power of cohering and fly off into the space 
around them, i. e '., suffer true evaporation. This 
action takes p'ace under atmospheric pressures, 
but, like ordinary evaporation, is greatly facili- 
tated by the presence of a high vacuum. 

True electric evaporation takes place with 
liquids as well as with solids. In an experiment 
with water, the influence of the kind of the elec- 
trification was clearly shown. A vessel of water 




Fig. 242- Electrical Evaporation. 

•exposed to the air was first positively electrified, 
but after an exposure of if hours only a trifling 
evaporation was noticeable. The water was 
then negatively electrified, and at the end of ii 
hours had lost yoVcr part of its weight more than 
did the positively charged water. 

Professor Crookes experimented with cadmium, 
and, in order to show that electric evaporation is 
different from evaporation produced by the agency 
of heat, tried the following, viz. : A high vacuum 
U-tube, shaped as shown in Fig. 242, was pro- 

A 




Fig 243. Electrical Evaporation. 

^vided with platinum poles sealed in the glass at 
A and B. Two "pieces of cadmium, C and D, 
were placed in the tube in the position shown, 
and the tube uniformly heated by means of a gas- 
burner and air bath, and maintained at a constant 
temperature. The current was then passed for 
about an hour, B, being made the negative pole. 



No metal was deposited in the neighborhood of 
the positive pole, the portions of the tube sur- 
rounding the positive pole being quite clean, 
while the corresponding portions of the other limb 
of the tube were thickly coated, as shown by the 
shading m the drawing- 

In another experiment, in which the tempera- 
ture was kept lower than in the preceding, viz., 
just below the melting point of the cadmium, 
after the current had passed for an hour, the limb 
of the tube through which the current had passed 
had received a thick coating, while the other was 
nearly free from coating, as shown in Fig. 243. 
Here the increase in the amplitude of the mole- 
cular oscillation under the influence of the elec- 
tricity is manifest. 

Evaporation, Electrification by 



An increase in the difference of potential ex- 
isting in a mass of vapor attending its sudden 
condensation. 

The free electricity of the atmosphere is be- 
lieved by some to be due to the condensation of 
the vapor of the air that results in rain, hail, 
clouds, etc. It is probable, however, that the 
true effect of condensation is mainly limited to 
the increase of a feeble electrification already 
possessed by the air or its contained vapor. The 
small difference of potential of the exceedingly 
small drops of water in clouds is enormously in- 
creased by the union or coalescing of many 
thousands of such drops into a single rain drop. 
(See Electricity, Atmospheric.) 

Exchange, Telephonic, System of 

— A combination of circuits, switches and 
other devices, by means of which any one of 
a number of subscribers connected with a 
telephonic circuit, or a neighboring telephonic 
circuit or circuits, may be placed in electrical 
communication with any other subscriber 
connected with such circuit or circuits. 

A telephone exchange consists essentially of a 
multiple switchboard, or a number of multiple 
switchboards, furnished with spring-jacks, an- 
nunciator drops, and suitable connecting cords. A 
call bell, or bells, is also provided. The annun- 
ciator drops are often omitted. (See Board, 
Multiple Switch.) 

Excitability. Electric, of Nerve or Mus- 
cular Fibre The effect produced by an 

electric current in stimulating the nerve of a 



ExcJ 



222 



[Exh* 



living animal, or in producing an involuntary- 
contraction of a muscle. 

Du Bois-Reymond has shown that these effects 
depend : 

(i.) On the strength of the current employed. 
The excitability occurs only when the current 
begins to flow, and when it ceases flowing; or, 
when the electrodes first touch the nerves, and 
when they are separated from it. Subsequent 
investigations have shown that this is true only 
for the frog's nerves, and is true for the human 
nerves only in the case of moderate currents, 
strong currents producing tetanus. 

(2.) On the rapidity with which the current 
used reaches its maximum value, that is, on the 
rapidity of change of current density. (See 
Current Density.) 

Excitability, Electro-Nervous — 

In electro-therapeutics the electric excitation 
of a nerve. 
Excitability, Electrotonic — The 

actual excitability of a nerve when in the 
electrotonic condition. (See Electrotonus. 
Anelectrotonus. Kathelectrotonus.) 

Excitability, Faradic — Muscular or 

nervous excitability following the employment 
of the rapidly intermittent currents produced 
by induction coils. (See Coil, Induction.) 

Faradic excitability is different from galvanic 
excitability, or that produced by means of a con- 
tinuous voltaic current. (See Excitability, Gal- 
vanic. ) 

Excitability, Galvanic — A term 

sometimes employed for electric excitability 
of nerve or muscular fibre. (See Excitability, 
Electric, of Nerve or Muscular Fibred) 

Excitation, Compensated, of Alternator. 
— (See Alternator, Compensated Excitation 
of.) 

Excitation, Direct — The excitement 

of a muscle by placing an electrode on the 
muscle itself. 

Excitation, Electro-Muscular — 

In electro-therapeutics the galvanic or faradic 
excitation of the muscle, or its excitation by 
the continuous currents of a voltaic battery, or 
the alternating currents of an induction coil. 

Excitation, Faradic Excitation of 

muscle or nerve fibre by means of rapidly 



alternating currents of electricity. (See 
Excitability, Faradic?) 

Excitation, Indirect The excite- 
ment of a muscle from its nerve. 

Exciter of Field.— (See Field, Exciter of.) 

Exciting" Liquid of Toltaic Cell. — (See 
Cell, Voltaic, Primary, Exciting Liquid of.) 

Execution, Electric Causing the 

death of a criminal, in cases of capital pun- 
ishment, by means of the electric current. 

Electric execution has been adopted by the 
State of New York, in accordance with the 
following law : 

"The Court shall sentence the prisoner to- 
death within a certain week, naming no day or 
hour, and not more than eight nor less than five 
weeks from the day of sentence. The execution 
must take place in the State prison to which con- 
victed felons are sent by the Court, and the execu- 
tioner must be the agent and warden of the prison. 

"No newspaper may print any details of the 
execution, which is to be inflicted by electricity. 
A current of electricity is to be caused to pass 
through the body of the condemned of sufficient 
intensity to kill him, and the application is to be 
continued until he is dead." 

Exhaustion, Electric Physiological 

effects resembling those produced by sun- 
stroke, resulting from prolonged exposure 
to the radiation of unsually large voltaic arcs, 
(See Sun-Stroke, Electric I) 

Exhaustion of Primary Toltaic Cell.— 
(See Cell, Voltaic, Primary, Exhaustion of) 

Exhaustion of Secondary Toltaic Cell.— 

(See Cell, Voltaic, Secondary, Exhaustion of I) 

Exhaustion of Toltaic Cell.— (See Cell, 
Voltaic, Exhaustio7i of.) 

Exhaustion, Reaction of A con- 
dition of nervous and muscular irritability to 
electric excitation when a certain reaction, 
produced by a given current strength, cannot 
be reproduced without an increase of current 
strength. 

The reaction of exhaustion may be regarded as 
a special variety of the reaction of degeneration. 
(See Degeneratioti, Reaction of.) 

The reaction of degeneration embraces the 
following modifications of irritability, viz.: 



Exp.] 223 

(i.) Disappearance or diminution of nervous 
irritability to both galvanic and taradic currents. 

(2.) Disappearance of faradic and increase of 
galvanic irritability of muscles, generally associ- 
ated with, an increase of mechanical irritability. 

(3.) Disappearance of faradic and increase of 
galvanic muscular irritability associated generally 
with increased mechanical irritability. 

(4. ) Tardy, delayed contraction of muscles in- 
stead of quick reaction of normal muscle. 

(5.) Marked modifications of normal sequence 
of contraction. — Liebig cV Rohe. 

Expanding Magnetic Whirl. — (See 
Whirl, Expanding Magnetic.) 

Expansion, Co-efficient of The 

fractional increase in the dimensions of a bar 
or rod when heated from 32 degrees to 33 
degrees F. or from o degree to I degree C. 

The fractional increase in the length of the bar 
is called the Co -efficient of Linear Expansion. 

The fractional increase in the surface is called 
the Co-efficient of Surface Expansion. 

The fractional increase in the volume is called 
the Co-efficient of Cubic Expansion. 

Expansion, Electric The increase 

in volume produced in a body on giving such 
body an electric charge. 

A Leyden jar increases in volume when a 
charge is imparted to it. This result is due to an 
expansion of the glass due to the electric charge. 
According to Quincke, some substances, such as 
resinous or oily bodies, manifest a contraction of 
volume on the reception of an electric charge. 

Expansion Joint. — (See Joi?it, Expan- 
sion) 

Expansion, Linear, Co-efficient of 

A number expressing the fractional increase in 
length of a bar for a given increment of heat. 

The co-efficients of expansion of a few sub- 
stances are given in the following table: 
Temp. 

Aluminium 16 to 100 degrees C . .0.0000235 

Brass. o ' k 100 " '* ..0.0000188 

Copper o " 100 " " ..0.0000167 

German silver., o " 100 " " ..0.0000184 

Glass o ' 5 100 " " ..0.0000071 

Iron 13" 100 *' " ..0.0000123 

Lead o" 100 " " ..0.0000280 

Platinum O" 100 " " .0.0000089 

Silver o" 100 " " ..0.0000194 

Zinc o" 100 " " ..0.0000230 

— {Anthony O 3 Brackett.) 



[Eye. 



Exploder, Electric Mine A small 

magneto-electric machine used to produce the 
currents of high electromotive force employed 
in the direct firing of blasts. 

Exploder, Electro-Magnetic —A 

small magneto-electric machine used to pro- 
duce the currents of high electromotive force 
employed in the direct firing of blasts. 

Explorer, Electric An apparatus 

operated by means of induced currents, and 
employed for the purpose of locating bullets 
or other foreign metallic substances in the 
human body. (See Balance, Induction, 
Hughes'.) 

Explorer, Magnetic A small, flat 

coil of insulated wire, used, in connection with 
the circuit of a telephone, to determine the 
position and extent of the magnetic leakage 
of a dynamo-electric machine or other similar 
apparatus. (See Magnetophone) 

Explosive Distance. — (See Distance, Ex- 
plosive.) 

Extension Call-Bell.— (See Bell, Exten- 
sion Call) 

External Circuit. — (See Circuit. Exter- 
nal) 

External Secondary Resistance. — (See 
Resistance, Exter?ial Secondary ) 

Extra Currents. — (See Currents, Extra) 

Extraordinary Resistance. — (See Resist- 
ance, Extraordinary) 

Extra-Polar Region. — (See Region, Ex- 
tra-Polar) 

Eye, Electro-Magnetic A term pro- 
posed for a certain form of spark-micrometer 
employed by Hertz in his experiment on elec- 
tro-magnetic radiation. 

This apparatus has received the above name 
because it enables the observer to see or localize 
an electromagnetic disturbance. 

The particular spark-micrometer that has re- 
ceived the name of the electro-magnetic eye had 
the form of a circle 35 centimetres in radius, and 
was formed of a copper wire 2 millimetres in di- 
ameter. Like all spark-micrometer circuits, it 
had its terminals separated by a small air-space. 

Eye, Selenium An artificial eye in 



Fac] 



224 



[Far. 



which a selenium resistance takes the place 
of the retina and two slides the place of the 
eyelids. 

The selenium resistance is placed in the circuit 
of a battery and a galvanometer. When the 
slides L, L, Fig. 244, are shut, the galvanometer 
deflection is less than when they are open. 

The opening of the aperture between the slides 
L, L, may be automatically accomplished by the 
action of the light itself, by moving them by an 
electro-magnet placed in the circuit of a local bat- 
tery, and a selenium resistance may be so arranged 
that when light falls on it the slides L, L, are 
moved together, and when the amount of such 
nght is small they are moved apart, by the action 



of a spring, In this way there is obtained a 
device roughly resembling the dilatation or con- 




Selenium Eye. 



traction of the pupil of the eye from the action of 
light on the iris. (See Photometer, Selenium.) 



Fac-Simile Telegraphy, or Panteleg- 

raphy. — (See Telegraphy, Fac-Simile) 

Fahrenheit's Thermometer Scale. — (See 
Scale, Thermometer, Fahrenheit's) 

Fall of Potential.— (See Potential, Fall 
of) 

False Magnetic Pole (See Pole, 

Magnetic, False.) 

False Resistance. — (See Resistance, 
False) 

False Zero. — (See Zero, False) 

Fan Guard. — (See Guard, Fan) 

Farad. — The practical unit of electric 
capacity. 

Such a capacity of a conductor or condenser 
that one coulomb of electricity is required to 
produce in the conductor or condenser a 
difference of potential of one volt. 

As in gases, a quart vessel will hold a quart of 
gas under unit pressure of one atmosphere, so, in 
electricity, a conductor or condenser, whose capa- 
city is one farad, will hold a quantity of electricity 
equal to one coulomb when under an electromotive 
force of one volt. 

It may cause some perplexity to the student to 
understand why there should be in electricity one 
unit of capacity to represent the size of the vessel 
or conductor, and another to represent the 
amount or quantity of electricity required to fill 



such vessel. But, like a gas, electricity acts, ir* 
effect, as if it were very compressible, so that the 
quantity required to fill any condenser will de- 

P ' N 




Fig. 243. Elevation of Standardized Condenser. 
pend on the electromotive force under which it is 
put into the conductor or condenser. 

For purposes of measurement, capacities of 
conductors are compared with those of condensers. 




Fig, 24b. Plan of Standardized Condenser. 

whose capacities are known in microfarads, or 
fractions thereof. The microfarad, or the 



of a farad, is used because of the 



1,000,000 

great size of a farad. 



very 



Far,.] 



225 



[Fan. 



Fig. 245 shows an elevation, and Fig. 246 a 
plan of the form often given to a standardized 
condenser or microfarad. The condenser is 
charged by connecting the terminals of the elec- 
tric source to the binding posts N and N. It is 
discharged by means of the plug key P', that 
connects the brass pieces A and B, when pushed 
firmly into the conical space between them. 

The condenser is made by placing sheets of tin 
foil between sheets of oiled silk or mica in the 
box and connecting the alternate sheets to one of 
the brass pieces B, and the other set to the brass 
pie j : A, as will be better understood from an 
inspection of Fig. 247. 

b 



Fig. 247 Method of Construction of a Condenser. 

Condensers are generally made of the capacity 
of the i of a microfarad. Sometimes, however, 
they are made so that either all or part of the 
condenser may be employed, by the insertion of 
the different plug keys. 

The form of condenser shown in Fig. 248 is 




Fig. 248 '. Standard Condenser 

capable of ready division into five separate val- 
ues, viz.: .05, .05, .2, .2 and .5 microfarad. 

Farad, Micro ■ —The millionth part 

of a farad. (See Farad) 

Faraday Effect.— (See Effect, Faraday.) 
Faraday's Cube.— (See Cube, Faraday • s) 



Faraday's Dark Space.— (See Space, 
Dark, Faraday's) 

Faraday's Net— (See Net, Faraday s.) 

Faradic Apparatus, Magneto-Electric 

(See Apparatus, Faradic. Mag- 
neto-Electric) 

Faradic Brush.— (See Brush, Faradic) 

Faradic Curreut.— (See Current Fara- 
dic) 

Faradic Excitation.— (See Excitation, 
Faradic) 

Faradic Induction Apparatus.— (See 

Apparatus, Faradic Induction) 

Faradic Irritability.— (See Irritability, 
Faradic) 

Faradic Machine. — (See Machine, Fara- 
dic) ■ 

Faradization. — In electro-therapeutics, the 
effects produced on the nerves or muscles 
by the use of a faradic current, in order to 
distinguish such effects from galvanization 
or those produced by a voltaic current. (See 
Galvanization) 

Faradization, General A method 

of applying the faradic current similar to 
that employed in general galvanization. 
(See Galvanization, General) 

Faradization, Local A method of 

applying the faradic current in general simi- 
lar to that employed in local galvanization. 
(See Galvanization Local.) 

Fault. — Any failure in the proper working 
of a circuit due to ground contacts, cross- 
contacts or disconnections. (See Contacts. 
Cross.) 

Faults are of three kinds, viz. : 

(1.) Disconnections. (See Disconnection.) 

(2.) Earths. (See Earth.) 

(3.) Contacts. (See Contacts.) 

Various methods are employed for detecting 
and localizing faults, for the explanation of 
which reference should be had to standard elec- 
trical works on testing or measurements. 

Fault, Ironwork, of Dynamo A 

ground or connection between the current of 
a dynamo and any part of its ironwork. 



Pan.] 



226 



[Fie. 



If the dynamo is in good connection with the 
ground, as is frequently the casein marine plants, 
this fault is the same as a ground. 

Faults, Localization of Determin- 
ing the position of a fault on a telegraph line 
or cable by calculations based on the fall in 
the potential of the line measured at different 
points, or by loss of charge, etc. 

For details, see standard works on electrical 
measurements. 

Feed, Clockwork, for Arc Lamps 

An arrangement of clockwork for obtaining 
a uniform feed motion of one or both elec- 
trodes of an arc lamp. 

The clockwork is automatically thrown into or 
out of action by an electro-magnet, usually placed 
in a shunt circuit around the carbons. 

Feed, To To supply with an electric 

current, as by a dynamo or other source. 

Feeder. — One of the conducting wires or 
channels through which the current is dis- 
tributed to the main conductors. 

Feeder, Standard or Main The 

main feeder to which the standard pressure 
indicator is connected, and whose pressure 
controls the pressure at the ends of all the 
other feeders. 

The term pressure in the above definition is 
used in the sense of electromotive force or differ- 
ence of potential. 

Feeder-Wires. — (See Wires, Feeder) 
Feeders. — In a system of distribution by 
constant potential, as in* incandescent elec- 
tric lighting, the conducting wires extend- 
ing between the bus-wires or bars, and the 
junction boxes. 

A feeder differs from a main in that a main 
consists of a conductor that maybe tapped at any 
point to supply a customer, while a feeder leads 
direct from the dynamo or other source to a main 
and is not tapped at any point. 

Feeders, Negative The feeders 

that are connected with the negative terminal 
of the dynamo. (See Feeders.) 

Feeders, Positive The feeders that 

are connected with the positive terminal of 
the dynamo. (See Feeders.) 



Feeding Device of Electric Arc Lamp. — 

(See Device, Feeding, of an Arc Lamp. 
Feed, Clockwork, for Arc-La7nps.) 
Feeding-Wire. — (See Wire, Feeding) 

Feet, Ampdre The product of the 

current in amperes by the distance in feet 
through which that current passes. 

It has been suggested that the term ampere- 
feet should be employed in expressing the strength 
of electro-magnetism in the field magnets of 
dynamo-electro machines or other similar ap- 
paratus. 

Ferranti Effect.— (See Effect, Ferranti) 

Ferro-Magnetic Substance. — (See Sub- 
stance, Ferro-Magnetic.) 

Fibre, Quartz A fibre suitable for 

suspending galvanometer needles, etc., made 
of quartz, 

The quartz fibre is obtained by fusing quartz and 
drawing out the fused material as a fine thread, 
in a manner similar to the production of glass 
fibres. Quartz fibres possess marked advantage 
over silk fibres, in that they are 5.4 times stronger 
for equal diameters, and especially, in that they 
return to the zero point, after very considerable 
deflections. 

Quartz fibres are readily obtained by fusing 
quartz pebbles together in the voltaic arc, and 
drawing them apart with a rapid, but steady, uni- 
form motion. 

Fibre Suspension. — (See Suspension, 
Fibre.) 

Fibre, Vulcanized A variety of in- 
sulating material suitable for purposes not 
requiring the highest insulation. 

Vulcanized fibre is, however, seriously affected 
by long exposure to moisture. 

Fibrone. — An insulating substance. 

Field, Air That portion of a mag- 
netic field in which the lines of force pass 
through air only. 

Field, Alternating An electrostatic 

or magnetic field the positive direction of the 
lines of force in which is alternately reversed 
or changed in direction. 

Field, Alternating Electrostatic 

An electrostatic field, the potential of which 
is rapidly alternating. 



Fie.] 



227 



[Fie. 



An alternating electrostatic field is, according 
to Tesla's experiments, produced in the neighbor, 
hood of the terminals of the secondary of an in- 
duction coil, through whose primary, alternations 
of high frequency are passing. 

Field, Alternating Magnetic. — A mag- 
netic field the direction of whose lines of 
force is alternately reversed. 

Field, Density of The number of 

lines of force that pass through any field, per 
unit of area of cross-section. 

Field, Electric A term sometimes 

used in place of an electrostatic field. (See 
Field, Electrostatic) 

Field, Electro-Magnetic The space 

traversed by the lines of magnetic force pro- 
duced by an electro-magnet. (See Field, 
Magnetic?) 

Field, Electrostatic The region of 

electrostatic influence surrounding a charged 
body. 

Electrostatic attractions or repulsions take 
place along certain lines called lines of electro- 
static force. These lines of force produce a field 
called an electrostatic field. Electric level or 
potential is measured along these lines, just as 
gravitation levels are measured with a plumb line 
along the lines of gravitation force. (See Poten- 
tial, Electric.) 

Work is done when a body is moved along the 
lines of electrostatic force in a direction from an 
oppositely charged body, or towards a similarly 
charged body, just as work is done against 
gravity when a body is moved along the lines of 
gravitation force, away from the earth's centre, 
or vertically upwards. 

Field, Exciter of In a separately 

excited dynamo-electric machine, the dyna- 
mo-electric machine, voltaic battery, or other 
electric source employed to produce the field 
of the field magnets. (See Machine, Dyna- 
mo-Electric.) 

Field, Intensity of The strength 

of a field as measured by the number of lines 
of force that pass through it per unit of area 
of cross-section. (See Field, Electrostatic. 
Field, Magnetic) 



magnetic influence surrounding the poles of a 
magnet. 

A space or region traversed by lines of 
magnetic force. 

A place where a magnetic needle, if free 
to move, will take up a definite position, under 
the influence of the lines of magnetic force. 

Unit strength of magnetic field is the field 
which would be produced by a magnetic pole of 
unit strength at unit distance. 

Magnetic attractions and repulsions are assumed 
to take place along certain lines called lines of 
magnetic force. The directions of these lines in 
any plane of a magnetic field may be shown by 
sprinkling iron filings over a sheet of paper held 
in a horizontal position to a magnet pole inclined 




Field, Magnetic 



■The region of 



Fig. 24Q. Magnetic Field. 

to the paper in the desired plane and then gently 
tapping the paper. 

The groupings of iron filings so obtained are 
sometimes called magnetic figures. 

The directions of the lines of force thus shown 
will appear from an inspection of Fig. 249, taken 
in a plane joining the two poles of a straight bar 
magnet, and Fig. 250, taken in a plane at right 
angles to the north pole of a straight bar magnet. 

In Fig. 249, the repulsion of the lines of force 
at either pole is shown by the radiation of the 
chains ot magnetized iron particles. The mutual 
attraction of unlike polarities is shown by the 
curved lines. 

In Fig. 250, the repulsion of the similarly mag- 
netized chains is clearly shown. 

Lines of magnetic force are assumed to pass 
out fr 0171 the north pole and back again into the 
magnet at its south pole. This assumed direction 



Fie.] 



228 



[Fie. 



is called the direction of the lines of magnetic 
force. 

Faraday expressed his conception of lines of 
magnetic force as follows: 

" Every line of force must therefore be consid- 
ered as a closed circuit, passing, in some part of 
its course, through a magnet and having an equal 
amount of force in every part of its course. There 




Fig. 2 SO. Magnetic Field. 

exist lines of force within the magnet of the same 
nature as those without. What is more, they are 
exactly equal in amount to those without. They 
have a relation in direction to those without and 
are, in fact, continuations of them." 

When a conductor, such as a wire through 
which a powerful current of electricity is flowing, 
is dipped in a mass of iron filings, a chain of iron 
filings is formed, the north end of which is urged 
around the conductor in one direction and the 
south end in the opposite direction, so that the 
movable chain of filings surrounds or grips the 
conductor in concentric rings or circles. 

The density of a magnetic field is directly pro- 
portional to the number of lines of force per unit 
of area of cross-section. 

A single line of fo v ce, or a unit line of force, is 
such an intensity of field as exists in each square 
centimetre of cross-section of a unit magnetic 
field. 

A magnetic field is uniform, or possesses uni- 
form intensity, when it possesses the same num- 
ber of lines of force per square centimetre of area 
of cross-section. 

Field, Magnetic, Alternating The 

magnetic field produced by means of an 
alternating current. 



Field, Magnetic, Dissymmetrical 

A field whose lines of force are not symmet- 
rically distributed in adjacent halves. 

Field, Magnetic, Expanding of 

An increase in the length of the lines of mag- 
netic force in any field, or an increase in the 
length of their magnetic circuit. 

Field, Magnetic, of an Electric Current 
The magnetic field surrounding a cir- 




fmsssuM 






Fig. 251. Field of Current. 

cuit through which an electric current is flow- 
ing. 

An electric current produces a magnetic field. 
This was discovered by Oersted j> 

in 18 19, and may be shown by 4 

sprinkling iron filings on a sheet 
of paper, placed on the wire 
conductor conveying the cur- 
rent, at right angles to the direc- 
tion in which the current is pass- 
ing. Here the lines of force 
appear as concentric circles, ex- 
tending around the conductor, 
as shown in Fig. 251. Their 
direction, as regards the length 
of the conductor, is shown in 
Fig. 252. The electric current 
sets up these magnetic whirls 
around the conductor on its 
passage through it. | 

The direction of the lines of „ 

J J Fig. 252. Direc- 

magnetic force produced by an tioH of U nes of 
electric current, and hence its Force, 
magnetic polarity, depends on the direction in 
which the electric current flows. This direction 




Fie. 



229 



[Fie. 



may be remembered as follows: If the current 
flows towards the observer, the directions of the 
lines of magnetic force is opposite to that of the 
hands of a watch, as shown in Fig. 253. 



^JLQJULQJ^rr 




Fig 233. Direction 0/ Lines of Force. 

It is from the direction of the lines of magnetic 
force that the polarity of a helix carrying a cur- 
rent is deduced. (See Solenoid, Magnetic. Mag- 
net, Electro. ) 

A magnetic field possesses the following prop- 
erties, viz.: 

(1.) All magnetizable bodies are magnetized 
when brought into a magnetic field. (See Indue 
tion, Magnetic.) 

(2.) Conductors moved through a magnetic 
field so as to cut its lines of force have differences 
of potential generated in them at different points, 
and if these points be connected by a conductor, 
an electric current is produced. (See Induction, 
Electro-Magnetic . ) 

Field, Magnetic, Pulsatory A field, 

the strength of which pulsates in such manner 
as to produce oscillatory currents by induc- 
tion. 

Field, Magnetic, Reversing That 

portion of the field of a dynamo-electric ma- 
chine, produced by the field-magnet coils, in 
which the currents flowing in the armature 
coils are stopped or reversed after the coil has 
passed its theoretical position of neutrality. 

Sparkless commutation is obtained by placing 
the brushes on the commutator so as to corre- 
spond with the reversing field. 

Field, Magnetic, Shifting A term 

proposed by Professor Elihu Thomson to ex- 
press a field of magnetic lines of changing 
position with respect to the axis of the pole 
from which they emanate. 

A shifting magnetic field is especially a phe- 
nomenon of a rapidly alternating magnetic field 



occurring in a substance like hardened steel in 
which the coercive force is fairly nigh. It, for 
example, a single magnet pole of an electro- 
magnet, whose coils are traversed by a rapidly 
alternating current of electricity, is placed near one 
end of a steel file, the changing polarity developed 
thereby moves or shifts trom the point directly 
over the pole towards the distant end. The 
presence of this shifting field can be shown by the 
rotation of discs of copper suitably inclined to i.he 
end of the file. In a similar manner a prismatic 
mass of steel, placed with one of its flat sides 
on the pole of a rapidly alternating magnetic 
field, will have a magnetic field developed in it, 
which will move or shift from the flat base 
towards the upper edge. Movable masses of good 
conducting metal, such as copper, will be set in 
rotation in a direction such as would be caused 
by an escape of gas therefrom. 

The shifting magnetic field travels from the 
upper portions of the prism just as a stream of 
escaping gaseous substance would. 

Field, Magnetic, Spreading-Out A 

term sometimes used to represent an expand- 
ing magnetic field. (See Field, Mag?ielic> 
Expanduig of,) 

Field, Magnetic, Stray That por- 
tion of the field of a dynamo-electric machine 
which is not utilized for the development of 
differences of potential in the armature, be- 
cause its lines of force do not pass through 
the armature. 

Field, Magnetic, Strength of The 

dynamic force acting on a free magnetic pole, 
placed in a magnetic field. 

If a free magnetic pole could be placed in a 
magnetic field, it would begin to move towards 
the opposite pole of the field, under its magnetic 
attraction, just as an unsupported body, free to 
move, would begin to fall towards the earth. 
The strength of a magnetic field corresponds to 
the acceleration of the force of gravity in the 
case of a falling body. The strength of the mag- 
netic pole corresponds to the mass of the falling 
body. The force impressed in the case of the 
magnetic field is equal to the strength of the pole 
multiplied by the strength of the held. 

Field, Magnetic, Symmetrical A 

field whose lines of force are symmetrically 
distributed in adjacent halves. 



Fie.] 



230 



[Fil. 



Field, Magnetic, Uniform A field 

traversed by the same number of lines of 
magnetic force in all unit portions of area of 
cross-section. (See Field, Magnetic) 

Field, Magnetic, Waste A term 

sometimes employed for stray field. (See 
Field, Magnetic, Stray) 

Field, Rotating-Current A mag- 
netic field produced by means of a rotating 
current. (See Current, Rotating) 

Field, Uniform Density of A uni- 
form density in all equal areas of cross- 
section of field. 

■ —The field of 



Field, Yortex-Ring — 

influence possessed by a vortex-ring. 

Professor Dolbear points out the fact that the 
direction of the rotation of a fluid constituting a 
vortex-ring resembles the magnet flux in a mag- 
netic field, and shows, from the action of such rings 
on one another, that they possess a true field, or 
atmosphere of influence outside their actual 
bodies. He infers that such rings possess true 
polarity, since the motions producing them have 
different directions on opposite sides or ends. 

Figure of Merit of Galvanometer. — (See 
Galvanometer, Figure of Merit of.) 

Figures, Breath Faint figures of 

condensed vapor produced by electrifying a 
coin, placing it momentarily on the surface of 
a sheet of clean, dry glass, and then breath- 
ing gently on the spot where the coin was 
placed. 

The moisture collects on the electrified portions 
of the plate and lorms a iairly distinct image ot 
the coin. 



Figures, Electric 



-Figures of various 



shapes produced on electrified surfaces by the 
arrangement of dust particles or vapor 
vesicles under the influence of electric charges. 

Electric figures are ot two varieties, viz.: 

(i.) Dust figures. 

(2.) Breath figures. 

Figures, Lichtenberg's Dust — 

Figures produced by writing on a sheet of shel- 
lac with the knob of a charged Leyden jar and 
then sprinkling over the sheet dried and 
powdered sulphur and red lead, which have 



been previously mixed together, and are so 
rendered, respectively negative and positive. 

The red lead collects on the negative parts of 
the shellac surface, and the sulphur on the posi- 
tive parts, in curious figures, known as Lichten- 
berg's Dust Figures, one of which is shown in 
Fig. 254. 




Fig. 254. Lichtenberg' s Dust Figures. 

These figures show very clearly that an electric 
charge tends to creep irregularly over the surface 
of an insulating substance. 

Figures, Magnetic A name some- 
times applied to the groupings of iron filings 
on a sheet of paper so held in a magnetic fie^d 
as to be grouped or arranged under the in- 
fluence of the lines of force of the same. (See 
Field, Magnetic.) 

Filament.— A slender thread or fibre. 
The term is applied generally to threads or 
fibres varying considerably in diameter. 

Filament, Current A term some- 
times employed in place of current streamlet. 
(See Streamlets, Current) 

Filament, Magnetic A polarized 

line or chain of ultimate magnetic, particles. 

This is sometimes called a uniform magnetic 
filament. 

A bar-magnet possesses but two free poles. 
When broken ai its neutral point or equator, the 
bar will develop free poles at the broken ends. 
This is explained by considering the magnet to 
be composed of a number of separate particles, 
separately magnetized. A single chain or fila- 
ment of such particles is called a magnetic 
filament. (See Magnet, Neutral Point of. Mag' 
netistn, Hughes' Theory of. Magnetism, 
Ewing^s Theory of) 

Filament of Incandescent Electric Lamp. 



FilJ 



231 



[Fir. 



— (See Lamp, Incandesce?it Electric, Fila- 
ment of) 

Filament, Uniform Magnetic A 

term sometimes applied to a magnetic fila- 
ment. (See Filame?it, Magnetic.) 

Filaments, Flashed Filaments for 

an incandescent lamp, that have been sub- 
jected to the flashing process. (See Carbons, 
Flashing Process for .) 

Filamentous Armature Core. — (See Core, 
Armature, Fila?nentous.) 

Film Cut-Out— (See Cut-Out, Film.) 

Finder, Induction A term some- 
times employed for a magnetic explorer. 

Finder, Position, Electric A de- 
vice by means of which the exact position of 
an object can be obtained. 

By means of a position-finder a gunner can 
be telephoned or otherwise ordered to fire at ob- 
jects he cannot see, and yet obtain a fair degree 
of accuracy. 

Finder, Range, Electric A de- 
vice by means of which the exact distance of 
an enemy's ship or other target can be readily 
determined. 

The operation of an electric range-finder is based 
on a method somewhat similar to the solving of a 
triangle for the purpose of determining distances. 
If the base line of a triangle and the two angles 
at the base are known, the other two sides and 
the included angle can be determined. 

In the range-finder, the resistance of a German 
silver wire corresponds to the graduated arc of 
the theodolite used to measure the angles, and a 
rheostat, as a receiving instrument, measures the 
values of the angles. The base line is a constant, 
so that the receiving instrument is marked in 
yards instead of angles. To use the range-finder, 
two observers watch the target object continu- 
ously through a telescope. They do this and 
nothing else, while a third observer watches a 
galvanometer and so alters a resistance, by moving 
a contact or slide key along a resistance wire, as 
to keep the needle of the galvanometer constantly 
at zero. The exact distance being thus ascer- 
tained, the gunner can make the proper allowance 
in firing. 

Finder, Wire Any form of galva- 
nometer used to locate or find the corre- 



sponding ends of different wires in a bunched 
cable. 

The different wires in a cable are usually tagged 
and numbered at the end of the cable and at the 
joints. The telephone has been successfully em- 
ployed as a wire finder. 

Fire Alarm Annunciator. — (See Annun- 
ciator, Fire Alarm) 

Fire Alarm, Automatic (See 

Alarm, Fire, Automatic?) 

Fire Alarm Contact. — (See Contact, Fire 
Alarm?) 

Fire Alarm Signal Box. — (See Box, Fire 
Alarm Signal.) 

Fire Alarm Telegraph Box.— (See Box, 
Fire Alar?n Telegraph.) 

Fire Ball.— (See Ball, Fire.) 

Fire Cleansing.— (See Cleansing, Fire) 

Fire Extinguisher, Electric A 

thermostat or mercury contact, which auto- 
matically completes a circuit and turns on a 
water supply for extinguishing a fire, on a 
certain predetermined increase of tempera- 
ture. 

Fire, Hot, St. Elmo's A term pro- 
posed by Tesla for a form of powerful brush 
discharge between the secondary terminals of 
a high frequency induction coil. (See Dis- 
charge, Br ush-and- Spray) 

This form of St. Elmo's fire differs from the 
ordinary form in being hot. Its general appear- 
ance is shown in Fig. 255, taken from Tesla. 




Fig- 255- st - Elmo's Hot Fire. 
Describing its production he says : '• In many of 
these experiments, when powerful effects are 
wanted for a short time, it is advantageous to use 



Fir.] 



232 



[Flo. 



iron cores with the primaries. In such case a 
very large primary coil may be wound and placed 
side by side with the secondary, and, the nearest 
terminal of the latter being connected to the 
primary, a laminated iron core is introduced 
through the primary into the secondary as far as 
the streams will permit. Under these conditions 
an excessively powerful brush, several inches 
long, which may be appropriately called ' St. 
Elmo's hot fire,' may be caused to appear at the 
other terminal of the secondary, producing strik- 
ing effects. It is a most powerful ozonizer ; so 
powerful indeed, that only a few minutes are suf- 
ficient to fill the whole room with the smell of 
ozone, and it undoubtedly possesses the quality of 
exciting chemical affinities." 

Fire, St. Elmo's — Tongues of faintly 

luminous fire which sometimes appear on the 
pointed ends of bodies in connection with the 
earth, such as the tops of church steeples or 
the masts of ships. 

The appearance of the St. Elmo's fire is due to 
brush discharges of electricity. 

Fishes, Electric A term applied to 

various fishes, such as the eel and the ray, 
which possess the ability of protecting them- 
selves by giving electric shocks to objects 
touching them. (See Eel, Electric) 

Fishing Box. — (See Box, Fishing) 

Fittings or Fixtures, Electric Light 

— The sockets, holders, arms, etc., required 
for holding or supporting incandescent electric 
lamps. 

Fixed Secondary. — (See Secondary, 
Fixed) 

Fixtures, Telegraphic A term gen- 
erally limited to the variously shaped supports 
provided for the attachment of telegraphic 
wires. 

Fixtures, Telegraphic House-Top 

Telegraphic fixtures placed on the roofs of 
buildings for the support of the lines. 

Flaming Discharge. — (See Discharge, 
Flaming.) 

Flash, Side A sparking or lateral 

discharge taking place from the sides of a 
conductor, when an impulsive rush of elec- 
tricity passes through it. 



The phenomenon of siae flashing is due to a 
lateral discharge which takes the alternative path, 
instead of a path of much smaller ohmic resist- 
ance. The tendency to side flash results from 
the fact that the metallic circuit possesses induct- 
ance. (See Path, Alternative. Discharge, Lat- 
eral. Inductance. ) 

Flashed Carbons. — (See Carbons, 
Flashed.) 

Flashed Filaments. — ( See Filaments, 

Flashed) ' 

Flashes, Auroral Sudden variations 

in the intensity of the auroral light. 

Intermittent flashes of auroral light that 
occur during the prevalence of an aurora. 
(See Aurora Borealis) 

Flashing of Carbons, Process for the 

— (See Carbons, Flashing Process for.) 

Flashing of Dynamo-Electric Machine.— 

(See Machine, Dynamo-Electric, Flashing 
of) 
Flat Cable.— (See Cable, Flat) 

Flat Duplex Cable.— (See Cable, Flat 
Duplex) 

Flat Ring Armature. — (See Armature, 
Flat Ring) 

Flats. — A name sometimes applied to those 
parts of commutator segments the surface of 
which, through wear, has become lower than 
the other portions. (See Commutator) 

Fleming's Gauss. — (See Gauss, Flem- 
ing's.) 

Fleming's Standard Yoltaic Cell.— (See 
Cell, Voltaic, Standard, Fleming's) 

Flexible Electric Light. Pendant. — (See 
Penda?it, Flexible Electric Light) 

Flexible Lead. — (See Lead, Flexible) 

Floating Battery, De la Rive's. — (See 
Battery, Floating, De la Rives) 

Flow.— In hydraulics, the quantity of 
water or other fluid which escapes from an 
orifice in a containing vessel, or through a 
pipe, in a given time. 

Flow-Lines of Escaping Fluid. — Lines 
within the mass of a fluid in motion, drawn at 



Flo.] 



233 



[Fly. 



a number of points, so that the flow at any- 
instant is tangential at such points to the 
curved path. 

Flow, Magnetic — The magnetic 

flux. (See Flux, Magnetic) 

Flow of Current, Assumed Direction of 

— (See Current, Assumed Directio7i 

of Flow of.) 

Flow of Energy. — (See Energy, Flow of.) 
Flow of Lines of Electrostatic Force. — 

(See Force, Electrostatic, Lines of, Assumed 
Flow of) 

Flow of Magnetic Induction. — (See In- 
duction, Magnetic, Flux or Flow of) 

Fluid, Depolarizing An electro- 
lytic fluid in a voltaic cell that prevents polari- 
zation. (See Cell, Voltaic, Polarization of) 

Fluid Insulator. — (See Insulator., Fluid) 

Fluoresce. — To become self-luminous 
when exposed to light. 

A body is said to fluoresce when it shines, by 
means of the light it produces. In this respect it 
differs from an illumined body, which shines by 
reflected light. 

Fluorescence. — A property possessed by 
certain solid or liquid substances of becoming 
self-luminous while exposed to light. 

In fluorescence the refrangibility of rays of 
light is changed. The invisible rays beyond the 
violet, the ultra-violet, become visible, so that 
the light is transformed, the particles absorbing 
one wave length and emitting another. (See Incan- 
descence.) 

Canary glass, or glass colored yellow by oxide 
of uranium, or a solution of sulphate of quinine, 
possesses fluorescent properties. The path of a 
pencil of light brought to a focus in either of these 
substances, or a beam or cone of light passed 
through them, is rendered visible by the particles 
lying in this path becoming self-luminous. The 
path of a beam of light entering the dusty air of 
a darkened chamber is visible from the light being 
diffused or scattered in all directions by the float- 
ing dust particles. 

In a fluorescent substance, the path of the light 
is also rendered visible by the particles which lie 
in its path, throwing out light in all directions. 
There is, however, this difference, that in the 



case of the dust particles the light which comes 
directly from the beam is reflected ; while in the 
case of the fluorescent body the light comes from 
the particles themselves, which are set into vibra- 
tion by the light that is passing through, and has 
been absorbed by their mass. 

Fluorescence is, therefore, a variety of phos- 
phorescence. (See Fhosphorescetzce.) 

Fluorescent. — Possessing the capability of 
fluorescing. 

Fluorescing. — Exhibiting the property of 
fluorescence. 

Flush Box.— (See Box, Flush) 

Fluviograpli. — An apparatus for electri- 
4 cally registering the varying height of water 
in a tidal stream or in the ocean ; or, in general, 
differences of water levels. 

Flux, Magnetic ■ — The number of 

lines of magnetic force that pass or flow 
through a magnetic circuit. 

The total number of lines of magnetic force 
in any magnetic field. 

The magnetic flux is also called the magnetic 
flow. 

A Committee of the American Institute of 
Electrical Engineers on " Units and Standards " 
proposed the following as the definition of mag- 
netic flux. 

"The magnetic flux through a surface bounded 
by a closed curve is the surface integral of mag- 
netic induction taken over the bounded surface, 
and when produced by a current is also equal to 
the line integral of the vector potential of the cur- 
rent taken round the boundary." 

" The uniform and unit time rate of change in 
flux through a closed electric circuit establishes 
unit electromotive force in the circuit." 

Fluxes range in present practical work from 
ioo to 100,000,000 C. G. S. lines, and the working 
units would perhaps prefix milli- and micro-. 

Flux of Magnetic Induction. — (See In- 
duction, Magnetic, Flux or Flow of) 

Flux or Flow of Magnetism. — (See Mag- 
netism, Flux or Flow of) 

Fly, Electric A wheel or other de- 
vice driven by the reaction of a convective 
discharge. (See Flyer, Electric. Convec- 
tion, Electric.) 



Fly.] 



234 



LFor. 



•A wheel arranged 





Flyer, Electric — 

so as to be set into rotation by the escape of 
convection streams from its points when 
connected with a charged conductor. 

A wheel formed of 
light radial arms P, P, P, 
etc., shaped as shown in, 
Fig. 256, and capable of 
rotation on the vertical 
axis A, is set into rapid 
rotation when connected 
with the prime conduc- 
tor of a frictional or in- 
fluence machine, through 
the convection strea?ns of 
air particles, which are Fig. 23b. Electric Flyer. 
shot off from the points or extremities of the 
radial arms. The wheel is driven by the reac- 
tion of these streams in a direction opposite to 
that of their escape. (See Discharge, Convective. ) 

Focus. — A point in front or back of a lens 
or mirror, where all the rays of light meet or 
seem to meet. (See Lens, Achromatic) 

Fog, Electric A dense fog which 

occurs on rare occasions when there is an 
unusual quantity of free electricity in the 
atmosphere. 

Daring these electric fogs the free electricity of 
the atmosphere changes its polarity at frequent 
intervals. 

Following Horn of Pole Pieces of 
Dynamo-Electric Machine. — (See Horns, 
Following, of Pole Pieces of a Dynamo- 
Electric Machine) 

Foot-Candle.— (See Candle, Foot.) 

Foot-Pound. — A unit of work. (See 
Work.) 

The amount of work required to raise I 
pound vertically through a distance of 1 foot. 

The same amount of work, viz., 3 foot-pounds, 
is done by raising I pound through a vertical 
distance of 3 feet, or 3 pounds through a verti- 
cal distance of 1 foot. 

Apart from air friction, the amount of work 
done in raising I pound through I foot, viz., I 
foot-pound, is the same whether this work be 
done in one second or in one day. The power, 
or the rate of doing work, is, however, very dif- 
ferent in the two cases. (See Power.) 

Force. — Any cause which changes or tends 



to change the condition of rest or motion of 
a body. 

Force, Centrifugal The force that 

is supposed to urge a rotating body directly 
away from the centre of rotation. 

If a stone be tied to a string and whirled around, 
and the string break, the stone will not fly off di- 
rectly away from the centre, but will move along 
the tangent to the point where it was when the 
string broke. 

The centrifugal force in reality is the force 
which is represented by the tension to which the 
string is subjected during this rotation. 

Force, Coercitive A name some- 
times applied to coercive force. (See Force, 
Coercive.) 

Force, Coercive The power of re- 
sisting magnetization or demagnetization. 

Coercive force, in the sense of resisting demag- 
netization, is sometimes called magnetic reten- 
tivity. 

Hardened steel possesses great coercive force; 
that is, it is magnetized or demagnetized with 
difficulty. 

Soft iron possesses very feeble coercive force. 

It is on account of the feeble coercive force of 
the soft iron ~ore of an electro-magnet that its 
main value depends, since it is thereby enabled to 
rapidly acquire its magnetization, on the comple- 
tion of a circuit through its coils, and to rapidly 
lose iti magnetization on the opening of such 
circuit. 

Force, Contact A difference of elec- 
trostatic potential, produced by the contact of 
dissimilar metals. 

That a difference of potential is produced by 
the mere contact of dissimilar metals is now gen- 
erally recognized. Such a force is generally 
called the true contact force. (See Force, True 
Contact. ) 

According to Lodge, a true contact force has 
no existence. There is no evidence, he thinks, 
of a peculiar electromotive force at the point of 
contact, but that the phenomena are due simply 
to the fact that the metals are immersed in air or 
oxygen, which is capable of combining with one 
of them, and that, therefore, the cause of the 
phenomena is the greater action, for instance, of 
the oxygen of the air on the zinc than on the 
copper. 



For.] 



235 



[For. 



According to this view, the voltaic effect is 
due not to the difference of potential between 
the zinc and copper, but to the difference of the 
action of the air or moisture. 

Force de Clieval or Clieval Yapeur. — 

The French term for horse-power. 

The force de cheval is equal to 75 kilogramme- 
metres per second, or 32,549 foot-pounds per 
minute. 

The English horse-power is equal to 33,000 
foot-pounds per minute. I force de cheval equals 
.98634 horse-power; I horse-power equals 1.01385 
force de cheval. — {Htring.) 



-The force developed 



Force, Electric— 

by electricity. 

This term is generally limited to the force of 
attraction or repulsion produced by an electro- 
static charge. 

Force, Electromotive The force 

starting electricity in motion, or tending to 
start electricity in motion. 

The force which moves or tends to move 
electricity. 

The term is an unfortunate one. Strictly speak- 
ing, electromotive force is not a force at all : 
at least, it is not a force in the Newtonian sense, 
where force is only that which acts on ??iatter. 

The term electromotive force is generally writ- 
ten thus : E. M. F. 

The unit of electromotive force is the volt. 

When electric induction takes place, there 
results a change in the distribution of the thing 
called electricity, whereby a movement occurs that 
results in a positive and a negative charge. The 
cause which produces this movement 13 called the 
electromotive force. 

There is an unfortunate want of uniformity at 
present in the use of the term "electromotive 
force." By some, the electromotive force is re- 
garded as something which causes the difference 
of potential ; by others the electromotive force is 
regarded as being produced by the difference of 
potential; and, by still others, electromotive force 
is regarded as the entire electric moving cause 
produced by any source; while anything less than 
this is called by them potential difference. 

Those who regard the electromotive force as 
the cause which produces the potential difference 
look on the electromotive force as acting within 



the source and maintaining a potential difference 
at its terminals. 

Silvanus P. Thompson uses the term electro- 
motive force in his "Elementary Lessons in 
Electricity and Magnetism" as follows: "The 
term ' electromotive force ' is employed to denote 
that which moves or tends to move electricity 
from one place to another. For brevity we some- 
times write it E. M. F. In this particular case it 
is obviously the result of difference of potential 
and proportional to it ; just as in water pipes, a 
difference in level produces a pressure, and the 
pressure produces a flow as soon as the tap is 
turned on, so difference of potential produces 
electromotive force, and electromotive force sets 
up a current as soon as a circuit is completed for 
the electricity to flow through." 

Mascart and Joubert, in their work on "Elec- 
tricity and Magnetism," Vol. I., say: "In all 
cases the difference of potential V^— V 2 , may be 
considered as producing the motion of electrical 
masses ; it is often called the electromotive force." 

Maxwell, in his "Elementary Treatise on Elec- 
tricity, " speaking of the potential differences 
which may be shown to exist at the terminals of 
a Daniell voltaic cell when on open circuit, says : 
' ' This difference of potential is called the electro- 
motive force of a Daniell cell." 

Balfour Stewart, in his " Electricity and Mag- 
netism," says: " This difference of electric level 
we shall call E, and, indeed, it is merely a manner 
of expressing the cause of electromotive force." 

Prof. Fleming, in his "Short Lectures to Elec- 
trical Artisans," says: "The difference of elec- 
trical level or potential must be caused by some 
electromotive force acting in the conductor." 

Prof. Anthony, in "A Review of Modern 
Electrical Theories," regards the potential dif- 
ference as due to electromotive force. He says : 
" Difference of potential results from a changed 
electrical distribution, an electrical strain, and 
represents the tendency to return to the state of 
equilibrium. Electromotive force is the some- 
thing from without that produced the electric 
strain." 

Hering, in his "Principles of Dynamo-Electric 
Machines/' says : " Difference of poteniial is, as 
the name implies, the difference of electrical po- 
tential between any two points of a circuit, and 
may, therefore, be applied to that at the poles of 
a machine, battery or lamp, or at the ends of 
leads, or, in general, to any two points in a cir- 
cuit. The term 'electromotive 101 ce,' however, 



For.] 



236 



[For. 



applies only to the maximum difference of potential 
which exists in the circuit, or, in other words, the 
total generated difference of potential." 

This lait paragraph expresses the distinction 
between the two terms as ordinarily used in con- 
nection wilh dynamos and batteries. 

Force, Electromotive, Absolute Unit of 
A unit of electromotive force ex- 
pressed in absolute or C. G. S. units. 

The one-hundred millionth part of a volt, 
since I volt equals 10 s C. G. S. units of elec- 
tromotive force. (See Units, Practical) 

Force, Electromotive, Average or Mean 

■ The sum of the values of a number of 

separate electromotive forces divided by their 
number. 

The square root of the mean square of the 
electromotive force of an alternating or \ ari- 
able current. 

When a wire in the armature of a dynamo- 
elecuic machine cuts the lines of magnetic force 
in the field of the machine, the electro motive 
force produced depends on the number of lines 
of force cut per second. This will vary for dif- 
ferent positions of the coil. The mean value of 
the varying electromotive forces between the 
brushes is the average electromotive force. 

Force, Electromotive, Back — A 

term sometimes used for counter electro- 
motive force. 

Counter electromotive force is the preferable 
term. (See Force, Electromotive, Counter.) 

Force, Electromotive, Counter 

An opposed or reverse electromotive force, 
which tends to cause a current in the oppo- 
site direction to that actually produced by 
the source. 

In an electric motor, an electromotive force 
contrary to that produced by the current 
which drives the motor, and which is pro- 
portional to the velocity attained by the 
motor. 

Counter electromotive force acts to diminish 
the current in the same manner as a resistance 
would, and is therefore sometimes called spurious 
resistance in order to distinguish it from an ohmic 
* or true resistance. 

Counter electromotive force is sometimes ex- 
pressed in ohms, though it is not a true ohmic 
resis.ance. (Sec; Resistance, Spurious.) 



The counter electromotive force of a voltaic 
battery is due to the polarization of the cells. 
Since this force is due to the current in the cell, it 
can never exceed such current or reverse its direc- 
tion. It may, however, equal it and thus stop its 
flow. (See Cell, Voltaic, Polarization oj .) 

In a storage cell, the charging current produces 
an electromotive force counter to itself, which, as 
in a motor, is a true measure of the energy stored 
in the cell. Economy requires that the electro- 
motive force of the charging current should be as 
little as possible greater than that of the counter 
electromotive force of the cell it is charging. 

In a voltaic arc a counter electromotive force is 
believed to be set up by polarization. 

Force, Electromotive, Counter, of Con- 

vective Discharge Resistance to the 

passage of an electric discharge through a 
high vacuum, somewhat of the nature of a 
counter electromotive force. 

The resistance to the passage of convective dis- 
charges, therefore, is due to the following causes: 

(i.) True ohmic resistance. 

(2.) Counter electromotive force. 

Force, Electromotive, Counter, of Mutual 

Induction The counter electromotive 

force produced by the mutual induction of 
the primary and secondary circuits on each 
other. 

Force, Electromotive, Counter, of Self- 
induction That part of the impressed 

electromotive force which is producing, or 
which tends to produce, at any instant a 
change in the current strength. 

Force, Electromotive, Counter, of Self- 
induction of the Primary A counter 

electromotive force produced in the primary 
circuit of an induction coil by the action 
thereon of a simple periodic electromotive 
force. 

The counter electromotive force produced 
in the primary circuit of an induction coil by 
the application of a simple periodic impressed 
electromotive force to the primary circuit. 

Force, Electromotive, Counter, of Self- 
induction of the Secondary — A 

counter electromotive force produced in the 
secondary by the periodic variations in the 
effective electromotive force in the secondarv. 



lor.} 



23 



[For. 



Force, Electromotive, Direct An 

electromotive force acting in the same direc- 
tion as another electromotive force already 
existing. 

The term direct electromotive force is em- 
ployed in contradistinction to counter electromo- 
tive force. (See Force, Electromotive, Counter. ) 

Force, Electromotive, Effective 

The difference between the direct and the 
counter electromotive force. 

Force, Electromotive, Effective, of Sec- 
ondary The difference between the 

direct and the counter electromotive force in 
the secondary of an induction coil. 

Force, Electromotive, Generated by Dy- 
namo-Electric Machine, Method of Increas- 
ing" The electromotive force of a dy- 
namo-electric machine may be increased in 
the following ways, viz : 

(i.) By increasing its speed of rotation. 

(2.) By increasing the strength of the magnetic 
field in which the armature rotates. 

(3.) By increasing the size of the field through 
which the armature passes in unit time, the in- 
tensity remaining the same. 

(4.) By increasing the number of armature 
windings, i. e., by making successive parts ot the 
same wire pass simultaneously through the field. 

Force, Electromotive, Impressed 

The electromotive force acting on any cir- 
cuit to produce a current therein. 

The impressed electromotive force may be re- 
garded as producing two parts, viz. : The effective 
electromotive force and the counter electromotive 
force. 

Force, Electromotive, Inductive 

A term sometimes used in place of counter 
electromotive force of self-induction. 

An 



Force, Electromotive, Inverse — 

electromotive force which acts in the oppo- 
site direction to another electromotive force 
already existing. (See Force, Electromotive, 
Counter.) 

Force, Electromotive, Motor A 

term proposed by F. J. Sprague for the coun- 
ter electromotive force of an electric motor. 
(See Force, Electromotive, Counter?) 

This term was proposel by Sprague as express- 



ing the necessity for the existence of a counter 
electromotive force in an electric motor, in order 
to permit it to utilize the energy of the electric 
current which drives it. 

Force, Electromotive, of Induction 

— The electromotive force developed by any 
inductive action. 

In a coil of wire undergoing induction, the 
value of the induced electromotive force dues not 
depend in any manner on the nature of the ma- 
terial of which the coil is composed. 

It has been shown : 

(l.) That the electromotive force of induction is 
independent of the width, thickness or material of 
the wire windings. — {Faraday.) 

(2.) That it is dependent on the form of the 
conductor, and the character of the change it ex- 
periences as regards the magnetic inducdon which 
takes place through it. 

Since any increase in the strength of a current 
flowing through a coiled circuit, produces a coun- 
ter electromotive force, which opposes the electro- 
motive force producing the current, it is clear 
that the impressed electromotive force must do 
work against this counter electromotive force all 
the time the current strength is incr asing. 

The movement of a circuit of a given length 
through a given field with a given velocity pro- 
duces the same electromotive force whether the 
circuit be formed of conducting material or non- 
conducting material, or consists of an electrolyte. 

Force, Electromotive, of Secondary or 

Storage Cell, Time-Fall of A gradual 

decrease in the potential difference of a stor- 
age battery observed during the discharge of 
the same. 

When a secondary or storage battery is first 
discharged, a slight decrease of its potential dif- 
ference takes place and a potential difference of a 
slightly decreased value is maintained nearly con- 
stant during a protracted period of discharge. 

Force, Electromotive, of Secondary or 

Storage Cell, Time-Rise of A gradual 

increase in the potential difference of a 
secondary or storage cell observed on begin- 
ning the discharge after a prolonged rest. 

When a secondary or storage cell is discharged 
and then given a prolonged rest by opening its 
circuit, a gradual but decided rise in its potential 
difference is observed on again beginning its dis- 
charge. 



For. 



23S 



[For. 



Force, Electromotive, Photo 



■An 



electromotive force produced by the action of 
light on selenium. (See Cell, Selenium?) 

Force, Electromotive, Reacting Induc- 
tive, of the Primary Circuit The back 

or counter electromotive force produced in the 
primary circuit by the current set up by in- 
duction in the secondary. 

Force, Electromotive, Secondary Im- 
pressed An electromotive force pro- 
duced in the secondary coil or circuit by a 
periodic electromotive force impressed on the 
primary. 

Force, Electromotive, Simple-Periodic 

An electromotive force which varies 

in such manner as to produce a simple 
periodic current, or an electromotive force the 
variations of which can be correctly repre- 
sented by a simple-periodic curve. 

Force, Electromotive, Thermo An 

electromotive force, or difference of potential, 
produced by differences of temperature 
acting at thermo-electric junctions. 

Force, Electromotive, Transverse 

An electromotive force excited by a mag- 
netic field in a substance in which electric 
displacement is occurring. 

It is to a transverse electromotive force that the 
Hall effect is due. (See Effect, Hall. ) 

Force, Electromotive, Zigzag An 

electromotive force, the curve of which would 
have the general form of a zigzag. 

Force, Electrostatic The force pro- 
ducing the attractions or repulsions of charged 
bodies. 

Force, Electrostatic, Lines of 

Lines of force produced in the neighborhood 
of a charged body by the presence of the 
charge. 

Lines extending in the direction in which 
the force of electrostatic attraction or repul- 
sion acts. 

An insulated charged conductor produces 
around it an electrostatic field, in a manner some- 
what similar to the magnetic field produced by 
a magnet or an electric current. (See Field, 
Electrostatic. ) 



Lines of electrostatic force pass through dielec- 
trics. Whether the force acts to produce electro- 
static induction, by means of a polarization of the 
dielectric, or by means of a tension set up in the 
substance of the dielectric, is not known. 

Force, Electrostatic, Lines of, Assumed 

Flow of A mathematical conception in 

which the phenomena of electricity are com- 
pared with the similar phenomena of heat. 

In heat no flow of heat occurs over isothermal 
surfaces, or surfaces at the same temperature. 
Between different isothermal surfaces, the flow 
will vary with the power of heat conduction. In 
electricity, no flow occurs over equipotential sur- 
faces. Specific inductive capacity corresponds to' 
heat conductivity, and the lines of force to the 
lines of heat conduction. (See Capacity, Specific 
Inductive.) 

Force, Lines of, Contraction of 



A decrease that occurs in the length of the 
circular lines of force that surround a circuit 
through which an electric current is passing, 
while the current is decreasing in intensity or 
strength. 

The contraction or decrease in the average 
diameter of the circular lines of force of an elec- 
tric circuit is similar to the expansion or growth 
of lines of force, excepting that the movement is 
one of decrease in diameter, and takes place in 
the opposite direction, i. <?., towards the circuit, 
instead of away from it. (See Force, Lines of, 
Growth or Expansion of.) 



-Passing a 



Force, Lines of, Cutting — 

conductor through lines of magnetic force, so 
as to cut or intersect them. 

The cutting of lines of magnetic force produces 
differences of potential. This is true whether the 
conductor moves through a stationary field or 
whether the field itself moves through the 
stationary conductor, so that the lines of force and 
the conductor cut one another. This cutting is 
mutual. Each line of force cuts and is cut by the 
circuit. Since all lines of force form closed-cir- 
cuits or paths, the cutting of the circuit by the 
lines of force, or the reverse, forms a link or chain, 
and the cutting takes place at the moment of 
linking or unlinking, i. e., of cutting. 

Force, Lines of, Diffusion of The 

deflection of the lines of magnetic force from 



For.] 



239 



[For, 



their ordinary position, between the poles 
that produce them. 

Force, Lines of, Direction of The 

direction in which it is assumed that the lines 
of magnetic force pass. 

It is generally agreed to consider the lines of 
magnetic force as coming out of the north pole of 
a magnet and passing into its south pole, as 
shown in Fig. 257. 




Fig. 25 7 . Direction of Lines of Force. 

This is sometimes called the positive direction 
of the lines of force and agrees in general with the 
direction in which the electric current is assumed 
to flow, which is from the positive to the nega- 
tive. That is to say, the lines of magnetic force 
are assumed to flow or pass out of the north pole 
and into the south pole of a magnet. Of course 
there is no direct evidence of any flow, or of any 
particular direction characterizing the lines of 
force. (See Field, Magnetic.) 

The lines of electrostatic force are assumed to 
pass out of a positively charged surface and into 
a negatively charged surface. 

Force, Lines of, Growth or Expansion of 

The increase in the length of path 

through which lines of force pass, consequent 
on an increase in the strength of the mag- 
netization of a magnet, or on an increase in 
the strength of the magnetizing current. 

The circular lines of force which surround a con- 
ductor through which a current is flowing, may be 
regarded as starting from the surface of the con- 
ductor and growing in size as they spread out- 
wards, at the same time new lines of force being 
formed in their places. This action continues while 
the strength of the current is increasing, somewhat 
like the series of concentric waves which are 
formed on the surface of water, when a stone is 
dropped into it. 

In their growth or expansion outwards from 
the conductor, if the lines of force cut or pass 
through neighboring conductors, they produce 



therein differences of electric ootential, capable, 
on being connected by a conductor, of produc* 
ing electric currents. 

Force, Lines of, Radiation of :The 

passing of lines of force out of the north 
pole of a magnet or solenoid. 

In gross matter all lines of magnetic induction 
either pass through magnetized iron, or other 
paramagnetic substance which surrounds an 
electric circuit. Since lines of force pass through 
a vacuum, the ether which occupies such a space 
must also be regarded as permitting the passage 
of lines of force. 

Force, Loops of A term sometimes 

employed in the sense of lines of force. (See 
Force, Magnetic, Lines of.) 

The term "Lines of Force" is generally 
aiopted in place of Faraday's term "Loops of 
Force." 

Force, Magnetic The force which 

causes the attractions or repulsions of mag- 
netic poles. 

Force, Magnetic, Line of Arbitra- 
rily a single line of magnetic force. 

Practically the lines of magnetic force 
which pass through a unit area of cross-sec- 
tion of a magnetic field of unit strength. 

Force, Magnetic, Lines of Lines 

extending in the direction in which -the mag- 
netic force acts. 

Lines extending in the direction in which 
the force of magnetic attraction or repulsion 
acts. (See Field, Magnetic.) 

Faraday regarded the lines of magnetic force as 
possessing tension along one direction. Lines of 
force act as if they were stretched elastic threads, 
possessed of the property of lengthening or short- 
ening, and of repelling one another. 

Force, Magnetic, Lines of, Conducting 
Power for A term employed by Fara- 
day for magnetic permeability. (See Perme- 
ability, Magnetic) 

Force, Magnetic, Lines of, Positive 

Direction of ■ — The direction in which 

a free north-seeking pole would move along 
the lines of force when placed in a magnetic 
field. 



For.] 



240 



[For. 



Force, Magnetic, Telluric — The 

earth's magnetic force. 

Force, Magneto-Motive The force 

that moves or drives the lines of magnetic 
force through a magnetic circuit against the 
magnetic resistance. 

A Committee of the American Institute of Elec- 
trical Engineers on "Units and Standards " pro- 
posed the following definition. 

The magneto-motive force in a magnetic cir- 
cuit is 47T multiplied by the flow of the current 
linked with that circuit. The magneto-motive 
force between two points connected by a line is 
the line integral of the magnetic force along that 
line. Difference of magnetic potential constitutes 
magneto-motive force." 

The same committee gave the electro-magnetic 
dimensional formula Li M^ T _1 . 

The flow or flux of lines of magnetic force in 
any magnetic circuit is proportional to the mag- 
neto-motive force divided by the magnetic resist- 
ance ; or, expressing the law in the form of Ohm's 
law for current: 

,,. .. ^. Magneto-Motive Force 

Magnetic Flux = — ^ft~; ■ 

Reluctance. 

In this formula the word reluctance is used in 
place of magnetic resistance. In the case of an 
electro-magnet, the magneto-motive force is pro- 
portional to the strength of the current which flows 
and the number of times it circulates; or, more 
simply, is proportional to the number of ampere 
turns. (See Turns, Ampere.) 

Force, Magneto-Motive, Absolute Unit of 

— 47r multiplied by unit current of one 

turn. 

Force, Magneto-Motive, Practical Unit 

of A value of the magneto-motive force 

equal to ^it multiplied by the amperes of one 
turn, or to ■$$ of the absolute unit. 

Force, Motor Electromotive — A 

term proposed by F. J. Sprague for the 
counter electromotive force of a motor. 

During the rotation of the armature of an 
electric motor in its field, a counter electromotive 
force is produced in its coils, which acts as a 
spurious resistance and opposes the flow or pass- 
age of the driving current through its coils. As 
the speed of the motor increases, this counter 
electromotive force increases and the strength of 
tiie driving current decreases until a certain 



maximum speed is reached, when, theoretically, 
no current passes. 

When a load is placed on the electric motor,, 
the speed, and consequently the counter electro- 
motive force, is decreased and more driving cur- 
rent is permitted to pass. It was this considera- 
tion, viz. : that the load automatically regulates 
the current required to drive the motor, that led 
to the name motor-electromotive force. (See 
Force, Electromotive, Counter.) 

Force, Resolution of The separa- 
tion of a single force, acting with a given 
intensity in a given direction, into a number 
of separate forces 
acting in some other 
direction. 

Thus the force D B, 
Fig. 258, acting with 
the intensity and in the 
direction shown, may 
be resolved into two 
component forces, D 




Fig. 2j8. Resolution of 
Force. 



E and D C, acting in the directions and having 
the intensities shown. The single force D B, ha* 
been resolved into two separate forces D E and 
CD. 



■A force or 



Force, True Contact — 

effect entirely distinct from the voltaic effect, 
which exists at the points of contact be- 
tween two dissimilar metals. 

The truth of the existence of a true contact force 
at the junction of dissimilar metals is seen by the 
reversible heat effects observed, when a current 
of electricity is passed across a junction of two 
dissimilar metals. When the current is passed in 
one direction, an increase of temperature is pro- 
duced, but when passed in the opposite direction, 
a decrease of temperature. (See Effect, Peltier.) 

Hence there would appear to be a force existing 
at the junction, helping the electricity along in 
one direction, but opposing it in the opposite di- 
rection. In one direction the electricity does 
work and consumes its own energy in so doing. 
In the other direction it opposes the passage of 
the current, and there results a generation of 
heat. 



Force, Tubes of 



-Tubes bounded by 



lines of electrostatic or magnetic force. 

Lines of force never intersect one another. 
Hence a tube of force may be regarded as con- 



For.] 



241 



[Fie. 



taining the same number of lines of force at any 
and every cross -section. 

Tubes ot electrostatic force always terminate 
against equal quantities of positive and negative 
electricity respectively. They terminate when 
they meet a conducting surface. 

The term tubes ot force is somewhat mislead- 
ing, since such so-called tubes are in general 
cones rather than tubes. 

Force, Twisting A term sometimes 

used for torque. (See Torque^ 

Force, Unit of A force which, act- 
ing for one second on a mass of one 
gramme, will give it a velocity of one centi- 
metre per second. 

Such a unit of force is called a dyne. (See 
Dyne.) 

Forces, Composition of Finding 

the direction and intensity of a single force 
which represents the total effect of two or 
more forces acting simultaneously on a body. 
(See Component.) 

Forces, Parallelogram of A para 1 - 

lelogram constructed about the two lines that 
represent the direction and intensity with 
which two forces are simultaneously acting 
on a body, in order to determine the direction 
and intensity of the resultant force with 
which it moves. 

If the two forces A C and A B, Fig. 259, simul- 
taneously act in the direc- 
tion of the arrows on a 
body at A, the direction 
and intensity of the re- 
sultant A D, is deter- 
mined by drawing C D 
and B D, parallel respectively to A B and A C. 
The diagonal A D, of the parallelogram A C D B, 
thus produced, gives this resultant. (See Com- 
ponent.) 

Fork, Trolley The mechanism 

which mechanically connects the trolley wheel 
to the trolley pole. (See Trolley.) 

Forked Circuits. — (See Circuits, Forked.) 

Forked Lightning. — (See Lightning, 
Forked.) 

Formal Inductance of Circuit— (See In- 
ductance, Formal, of Circuit.) 




Fig. 2JQ. Farallelo- 
gram of Forces. 



Forming Plates of Secondary or Stor. 
age Cells. — (See Plates of Secondary or Stor- 
age Cells, Forming of.) 

Formulae. — Mathematical expressions for 
some general rule, law, or principle. 

Formulae are of great assistance in science in 
expressing the relations which exist between cer- 
tain forces or values, and the effects that result 
from their operations, since they enable us t) ex 
press these relations in clear and concise forms. 

Thus in th^ formulation of Ohm's law: 

we see that the continuous current C, in any cir- 
cuit, is equal to the elec'romotive force E, divided 
by the resistance R. Again, we see that the cur- 
rent is directly proportional to the electromotive 
force, and inversely proportional to the resistance. 

Formulae are usually written in the form of an 
equation and therefore contain the sign of equality 
or =. 

Formulae, Photometric (See Pho- 
tometric Formulce.) 

Foncault Currents.— (See Currents, Fou- 
cault.) 

Four-Way Splice Box.— (See Box, Splice, 
Four- Way.) 

Frames, Sectional Plating Frames 

employed for so holding the objects to be 
plated that they shall receive a greater depth 
of deposit on certain portions of their surface 
than elsewhere. 

Sectional printing frames depend for their 
action on the fact that the portions receiving the 
greater depth of deposit are nearer one of the 
electrodes than the rest of the surface. 

Franklinic Electricity. — (See Elec- 
tricity, Franklinic.) 

Franklinization. — Electrization by means 
of a frictional or influence machine as distin- 
guished from faradization or electrization by 
means of an induction coil. 

This term is used only in medical electricity. 

Free Charge. — (See Charge, Free.) 

Free Magnetic Pole.— (See Pole, Mag- 
netic, Free.) 

Frequency of Alternations. — (See Alter- 
nations, Frequency of.) 



Fri 



242 



[Fun, 



Friction Brake.— (See Brake, Friction?) 
Frictional Electrical Machine. — (See 

Machine, Frictional Electric?) 
Frictional Electricity. — (See Electricity , 

Frictional?) 

Frog\ Galvanoscopic The hind legs 

cf a recently killed frog- employed as an elec- 
troscope or galvanoscope, by sending an elec- 
tric current from the nerves to the muscles. 
(See Electroscope?) 

In 17S6, Luigi Galvani made the observation 
that when the legs of a recently killed frog were 
touched by a metallic conductor connecting the 
nerves with the muscles, the legs were convulsed 
as though alive. He repeated this experiment 
and found the move- 
ments were more pro- 
nounced when two dis- 
similar metals, such as 
iron and copper, were 
employed in the manner 
shown in Fig. 260. 

The classic experi- 
ment created intense 
excitement in the scien- 
tific world, and Galvani 
at first believed that he 
had discovered the true vital fluid of the animal, 
but afterwards recognized it as electricity, which 
he believed to be obtained from the body of the 
animal. Volta claimed that the movements were 
due to electricity caused by the contact of dissimi- 
lar metals, and thus produced his famous voltaic 
pile. (See Pile, Voltaic.) 

Frog, Trolley The name given to 

the device employed in fastening or holding 
together the trolley wires at any point where 
the trolley wire branches, and properly guiding 
the trolley wheel along the trolley wire on the 
movement of the car over the track. 

Frog, Trolley, Right-Hand A trol- 
ley frog used at the point where the branch 
trolley wire leaves the main line on the right 
of the direction in which the car is moving. 

Frog Trolley, Standard The trol- 
ley frog used at the point where two branch 
lines make equally converging angles to the 
main line. 

Frog, Trolley, Three- Way A trol- 




Fig. 2 bo. Galvanoscopic 
Frog. 



ley frog used where the line branches in three 
directions. 
Frying of Arc— (See Arc, Frying of) 
Fulgurite. — A tube of vitrified sand, be- 
lieved to be formed by a bolt of lightning. 

The fulgurite consists of an irregular shaped 
tube of glass formed of sand which has been 
melted by the electric discharge. 

Full Contact— (See Contact, Metallic?) 

Fuller's Mercury Bichromate Voltaic 
Cell. — (See Cell, Voltaic, Fuller's Mercury 
Bichro?nate?) 

Fulminate. — The name of a class of highly 
explosive compounds. 

Fulminating gold, silver and mercury are 
highly explosive substances. Fulminates are 
employed in percussion caps. 

Function, Trigonometrical Cer- 
tain quantities, the values of which are de- 
pendent on the length of the arcs subtended 
by angles, which are taken for the measures 
of the arcs or angles instead of the arcs 
themselves. 

The trigonometrical functions are the sine, the 
co-sine, the tangent, the co-tangent, the secant 
and the co-secant. 

These are generally abbreviated thus, viz. : sin., 
cos., tan., cot., sec. and co-sec. 

The sine of an angle or arc is the perpendic- 
ular distance from one L C 
extremity of the arc to 
the diameter passing 
through the other ex- 
tremity. 

Thus in Fig. 261 B D, 
is the sine of the angle 
B O A, or of the arc, 
B A. 

The co-sine of an an- 
gle or arc is that part of Fig. 261. Trigonometric 
the diameter which lies cal Functions. 

between the foot of the sine and the centre. Thus, 
D O, is the co-sine cf the angle B O A, or of the 
arc B A. 

The co-sine of an arc is equal to the sine of its 
complement. Thus E O B, or B E, the comple- 
ment of B A* has for its sine I B, which is equal 
to O D. (See Angle, Complement of ".) 

If the arc is greater than a right angle, or 90 



Kn 


E 


j/1 


r 


^ — 


~~~^\^ 


(\ B 




1 / 


h 


1 


\ C 


> 



Fun.] 



243 



[Fus. 



degrees, such, for instance, as the angle TOG, 
or the arc B E F G, B D, is its sine. This is also 
the sine of B O A, or B A, which is the supple- 
ment of T O G, or B E F G. Hence the sine of 
an arc is equal to the sine of its supplement. 

The same is true of the co-sine. 

The tangent of an angle or arc is a straight 
line touching the arc at one extremity, drawn 
perpendicular to the diameter at that end of the 
arc, and limited by a straight line connecting the 
centre of the circle and the other end of the arc. 
Thus C A, is the tangent of the angle B O A, or 
the arc B A. 

The co-tangent of an angle or arc is equal to 
the tangent of its complement. Thus E T, is the 
co-tangent of the angle B O A, or the arc B A. 

The tangent of an angle or arc is equal to the 
tangent of its supplement. Thus A C, is the tan- 
gent of the angle B O A, or the arc B A. It is 
also equal to the tangent of the angle B O G, or 
the arc B E F G, the corresponding supplement of 
the angle B O A, or the arc B A. 

The secant of an angle or arc is the straight 
line drawn from the centre of the circle through 
one extremity of the arc and limited by the tan- 
gent passing through the other extremity. Thus 
O C, is the secant of the angle B O A, or of the 
arc B A. 

The secant of an angle or arc is equal to the 
secant of its supplement. 

The co-secant of an angle or arc is equal to 
the secant of its complement. 

Thus O T, is the co-secant of the angle BOA, 
or of the arc B A. 

It will be observed that the co-sine, the co- 
tangent and the co-secant are respectively the 
sine, tangent and secant of the complement of 
the arc, or in other words, the complement-sine, 
the complement-tangent and the complement- 
secant. 

Fundamental Units. — (See Units, Funda- 
mental.) 

Furnace, Electric — A furnace in 

which heat generated electrically is employed 
for the purpose of effecting difficult fusions 
for the extraction of metals from their ores, 
or for other metallurgical operations. 

In electric furnaces, the heat is derived either 
from electric incandescence or from the voltaic arc. 
The latter form is frequently adopted. 

The substance to be treated is exposed directly 



to the voltaic arc. In some forms of furnace the 
crushed ore is permitted to fall through the arc, 
and the melted matter received in a suitable ves- 
sel in which the separation of the substances so 
formed is afterwards completed. In other forms 
of furnace, the ore is placed between two elec- 
trodes of carbon or other refractory substance, 
between which a powerful current is passed. In 
the Cowles furnace, when aluminium is reduced, 
molten copper forms an alloy with the aluminium 
as soon as separated. 

Very numerous applications of electricity to 
furnace operations have been made. 

Fuse Block.— (See Block, Fuse.) 

Fuse Board.— (See Board, Fuse.) 

Fuse Box.— (See Box, Fuse.) 

Fuse, Branch A safety fuse or 

strip placed in a branch circuit. (See Fuse, 
Safety.) 

Fuse, Converter A safety fuse con- 
nected with the circuit of a converter or 
transformer. 

Fuse, Electric A device for elec- 
trically igniting a charge of powder. 

Electric fuses are employed both in blasting 
operations and for firing cannon. 

Electric fuses are operated either by means of 
the direct spark, or by the incandescence of a 
thin wire placed in the circuit. They are there- 
fore either high tension, or low tension fuses. 

The advantages of an electric fuse consist in 
the fact that its use permits the simultaneous fir- 
ing of a number of charges in a mining operation, 
thus obtaining a greater effect from the explosion. 
A fulminate of mercury is frequently employed 
in connection with some forms of electric fuses. 

Fuse, Electric, Hisrh-Tension A 



fuse that is ignited by the heating power of 
an electric spark. 

High-tension fuses, therefore, require a high 
electromotive force. This is obtained either by 
means of induction coils or by some form of 
electrostatic induction machine. 

Fuse, Electric, Low-Tension A 

fuse that is ignited by heating a wire to incan- 
descence by the passage through it of an 
electric current. 
Fuse, Electric, Stratham's A form 



Fus.] 



244 



[Gal. 



of fuse, in which the ignition is effected by the 
electric spark, is shown in Fig. 262. 

The spark passes through a break A B, in the in- 
sulated leads D. Since gunpow- 
der is not readily ignited by an 
electric spark, a peculiar priming 
material is employed at AB, in the 
place of ordinary powder. 

Fuse Links. — (See Li7iks, 
Fuse.) 

Fuse, Magazine — A 

safety fuse so arranged as to 
readily permit the replacement 
of the fuse when burned out. 

A spool contains a coil of fuse ^y~ 2 (, 2 . 
wire. In order to release the Stratham's 
burned-out fuse, a wedge-shaped Fuse. 
device is provided to open the clamps that hold 
the fuse strip to release the portions of burned- 
out fuse left, and connection with the fuse strip 
is severed while the attachment of the new strip 
is being made. 

Fuse, Main A safety fuse or strip 

placed in a main circuit. (See Fuse, Safety?) 

Fuse, Platinum A thin platinum 

wire rendered incandescent by the passage of 
an electric current and employed for the igni- 
tion of a charge of powder. (See Fuse, 
Electric?) 

Fuse, Safety A strip, plate or bar 

of lead, or some readily fusible alloy, that au- 
tomatically breaks the circuit in which it is 
placed on the passage of a current of suf- 



ficient power to fuse such strip, plate or bar^ 
when such current would endanger the safety 
of other parts of the circuit. 

Safety fuses are often called safety strips or 
safety plugs. 

Safety fuses are made of alloys of lead, and 
are placed in boxes lined with non-combustible 
material in order to prevent fires from the molten 
metal. 

Fig. 263 shows a fusible strip F, connected with 
leads L, L. Safety fuses are placed on all branch 
circuits, and are made of sizes proportionate to 
the number of lamps they guard. 




Fig. 263. Safety Fuse. 

Since incandescent lamps are generally placed 
in the circuit in multiple- arc, or in multiple-series, 
one or more of the circuits can be opened by the 
fusion of the plug without interfering with the 
continuity of the rest of the circuits. In series 
circuits, however, such as arc-light circuits, when 
a lamp is cut out, a short circuit or path around 
it must be provided in order to avoid the extin- 
guishing of the rest of the lights. 

Fuse Wire. — (See Wire, Fuse?) 

Fusible Plug. — A term commonly applied 
to a safety plug. (See Fuse, Safety 



G 



Gains. — The spaces cut in the faces of 
telegraph poles for the support or placing of 
the cross arms. 

Galvanic Battery. — (See Battery, Gal- 
vanic?) 

Galvanic Cell. — (See Cell, Voltaic?) 

Galvanic Circle. — (See Circle, Galvanic?) 

Galvanic Circuit. — (See Circuit, Gal- 
vanic.) 



Galvanic Dosage. — (See Dosage, Gal- 
vanic?) 

Galvanic Electricity. — (See Electricity, 
Galvanic?) 

Galvanic Excitability of Nerve or Mus- 
cular Fibre. — (See Excitability, Electric, 
of Nerve or Muscular Fibre?) 

Galvanic Irritability. — (See Irritability t 
Galvanic?) 



tial.] 



245 



[Gal 



Galvanic Multiplier.— (See Multiplier, 
Galvanic?) 

Galvanic Polarization. — (See Polariza- 
tion, Galvanic.) 

Galvanic Taste.— (See Taste, Galvanic?) 

Galvanism. — A term sometimes employed 
to express the effects produced by voltaic 
electricity. 

Galvanization, Central A variety 

of general galvanization in which the kathode 
is placed on the epigastrium and the anode 
moved over the body. 

Galvanization, Electro-Metallurgical 
The process of covering any conduc- 
tive surface with a metallic coating by elec- 
trolytic deposition, such, for example, as the 
thin copper coating deposited on the carbon 
pencils or electrodes used in systems of arc 
lighting. 

The term is borrowed from the French, in 
which it has the above signification. It is prefer- 
ably replaced by the term electro-plating. (See 
Plating, Electro.) 

The term galvanization is never correctly ap- 
plied to the process for covering iron with zinc or 
other metal by dipping the same in a bath of 
molten metal. 

Galvanization, Electro-Therapeutical 

In electro-therapeutics, the effects 

produced on nervous or muscular tissue by 
the passage of a voltaic current. 

Galvanization, General A method 

of applying a current therapeutically by the 
use of electrodes of sufficient size to direct 
the current through practically the entire 
body. 

Galvanization, Labile — A term 

employed in electro-therapeutics, in contradis- 
tinction to stabile galvanization, to designate 
the method of applying the current by keep- 
ing one ebctrode at rest in firm contact with 
one part of the body, and connecting the other 
electrode to a sponge which is moved over 
the parts of the body that are to be treated. 

Galvanization, Local The applica- 
tion of galvanization to parts or organs of the 
body in contradistinction to general galvani- 
zation. 



Galvanization, Stabile A term 

employed in electro-therapeutics in which the 
current is caused to pass continuously and 
steadily through the portions of the body un- 
dergoing galvanization. 

In stabile galvanization, the current is applied 
to and removed from the body gradually, in order 
to avoid shocks at the beginning and end of the 
application. 

Galvanized Iron. — (See Iron, Galvan- 
ized?) 

Galvano. — A word sometimes used in 
France in place of the word electro, to signify 
an article reproduced in copper by electro- 
metallurgy, especially an electrotype or wood- 
cut. 

Galvano-Causty. — (See Causty, Galvano.) 

Galvano-Cautery. — 'See Cautery, Gal- 
vano?) 
Galvano-Cautery, Chemical — A 

term sometimes applied to electro puncture 
or the application of electrolysis to the treat- 
ment of diseased growths. (See Cautery, 
Electric. Puncture, Electro?) 

The term chemical galvano-cautery would ap- 
pear to be poorly chosen, as it would imply the 
existence of a cautery action, which in point of 
fact does not exist. 

Galvano-Faradization. — In electro-thera- 
peutics, the simultaneous excitation of a nerve 
or muscle by both a voltaic and a faradic cur- 
rent. 

Galvano-Magiiet. — A term sometimes used 
for electro-magnetic. 

Electro magnetic is by far the preferable term, 
and is almost universally employed in the United 
States. 

Galvanometer. — An apparatus for meas- 
uring the strength of an electric current by 
the deflection of a magnetic needle. 

The galvanometer depends for its operation on 
the fact that a conductor, through which an elec- 
tric current is flowing, will deflect a magnetic 
needle placed near it. This deflection is due to 
the magnetic field caused by the current. (See 
Field, Magnetic, of an Electric Current.) 

This action of the current was first discovered 
by Oersted. A wire conveying a current in the 



Gal.] 



246 



[Gal. 



direction shown by the straight arrow, Fig. 264, 
or from + to — , will deflect a magnetic needle in 
the direction shown by the curved arrows. 

The following rules show the direction of the 




Fig. 264. Oersted's Experiment. 

deflection of a magnetic pole by an electrical cur- 
rent : 

(1.) Place the right hand on the conductor 
through which the current is flowing, with the 
palm facing the north pole, and with the fingers 
pointing in the direction of the current. The 
thumb will indicate the direction in which the 
north pole tends to move. 

(2.) Suppose an ordinary corkscrew so placed 
along the conductor, through which a current of 
electricity is passing, that when twisted, it will 
move in the direction of the current. The han- 
dle will then turn in the direction in which the 
north pole of the magnet tends to move. 

(3.) Imagine one swimming along the con- 
ductor in the direction of the current and facing 
the magnet. The north pole will tend to move 
towards the left hand of the swimmer. 

Prof. Forbes has shown that the direction of 
the deflection of a magnet by a current is such 
A B C 




Fig. 26 J. Ampere's Apparatus. 

that if the magnet were flexible, it would wrap 
itself round the current. 

If the wire be bent in the form of a hollow rec- 
tangle F, D, E, G, Fig. 265, and the needle, M, 



be placed inside the circuit, the upper and lower 
branches of the current will deflect the needle in 
the same direction, and the effect of the current 
will thus be multiplied. Mercury cups are pro- 
vided at A, B and C, for a ready change in the 
direction of the current. (See Needle, Astatic.) 

This principle of the multiplication of the de- 
flecting power of a current was first applied to gal- 
vanometers by Schweigger, who used a number of 
turns of insulated wire for the purpose of obtain- 
ing a greater deflection of the needle. He called 
such a device a multiplier. In extremely sensi- 
tive galvanometers, very many turns of wire are 
employed, in some cases amounting to many 
thousands. Such galvanometers are of high re- 
sistance. Others, of low resistance, often con- 
sist of a single turn of wire and are used in the 
direct measurement of large currents. 

A Schweigger's multiplier or coil C, C, of 
many turns of insulated wire, is shown in Fig. 266. 
The action of such a coil on the needle M, is com- 
paratively great, even when the current is small. 




Fig. 2 06. Schweigger's Mtiltiplier. 

In the case of any galvanometer, when no cur- 
rent is passing, the needle, when at rest, should in 
general occupy a position parallel to the plane of 
the coil. On the passage of the current, the 
needle tends to place itself in a position at right 
angles to the direction of the current, or to the 
length of the conducting wire in the coil. The 
strength of the current passing is determined by 
observing the amount of this deflection as meas- 
ured in degrees on a graduated circle over which 
the needle moves. 

The needle is deflected by the current from a 
position of rest, either in the earth's magnetic 
field or in a field obtained from a permanent or 
an electro magnet. In the first case, when in use 
to measure a current, the plane of the galvanom- 
eter coils must coincide with the planes of the 
magnetic meridian. In the other case, the instru- 



Gal.] 



247 



[Gal, 



ment may be used in any position in which the 
needle is free to move. 

Galvanometers assume a variety of forms ac- 
cording either to the purposes for which they are 
employed, or to the manner in which their deflec- 
tions are valued. 

Galvanometer, Absolute A galva- 
nometer whose constant can be calculated 
with an absolute calibration. (See Calibra- 
tion, Absolute') 

Such a galvanometer is called absolute because 
if the dimensions of its coil and needle are known, 
the current can be determined directly from the 
observed deflection of the needle. 



Galvanometer, Aperiodic 



-A gal- 



vanometer the needle of which comes to its 
position without any oscillation. 

A dead-beat galvanometer. (See Galva- 
nometer, Dead-Beat.) 

Galvanometer, Astatic A galva- 
nometer, the needle of which is astatic. (See 
Needle, Astatic) 

Nobili's astatic galvanometer is shown in Fig. 
267. The astatic needle, suspended by a fibre b, 
has its lower needle placed inside a coil, a, con- 
sisting of many turns of insulated wire, its upper 
needle moving over the graduated dial. The cur- 
rent to be measured is led into and from the 
coil at the binding posts, x and y. 




Fig. 267. Astatic Galvanometer. 

In this instrument, if small deflections only are 
employed, the deflections are sensibly propor- 
tional to the strength of the deflecting currents. 



Galvanometer, Ballistic 



-A galva- 



nometer designed to measure the strength of 
currents that last but for a moment, such, for 
example, as the current caused by the dis- 
charge of a condenser. 



The quantity of electricity passing in any cir- 
cuit is equal to the current multiplied by the time. 
Since the current caused by the discharge of a 
condenser lasts but for a small time, during which 
it passes from zero to a maximum and back again 
to zero, the magnetic needle in a ballistic galva- 
nometer takes the form of a ballistic pendulum, 
i. e., it is given such a mass, and acquires such a 
slow motion, that its change of position does not 




Fig. 268. Ballistic Galvanometer. 

practically begin until the impulses have ceased 
to act. 

In the ballistic galvanometer of Siemens and 
Halske, the coils R, R, Fig. 268, have a bell- 
shaped magnet, M, suspended inside them by 
means cf an aluminium wire. The magnet is pro- 
vided with a mirror S, for measuring the deflec- 
tions. The bell-shaped magnet is shown in ele- 
vation at M, and in plane at n, s. 

In using the ballistic galvanometer, it is neces- 
sary to see that the needle is absolutely at rest be- 
fore the charge is sent through the coils. 

A form of ballistic galvanometer by Nalder is 
shown in Fig. 269. 

The ordinary form of compensating magnet 
is, in this galvanometer, replaced by the small mag- 
net A, capable of rotation in a horizontal plane, but 
incapable of being raised or lowered, as is usual 
in such magnets. This form of compensating mag- 
net possesses the advantage of being able to alter 
the direction of the field on the needle system, 



Gal.] 



248 



[Gal. 



without considerably altering its intensity. When 
the galvanometer is for ready use the magnet A, is 
turned until the needle is brought to zero. The 




Fig. 2bq. Nalder's Galvanometer. 
combined field of earth and magnet A, are then 
brought to the degree of sensitiveness required 




Fig. 270. Nalder's Galvanometer. 

by rotating magnet B, on its shaft, or altering 
its distance from the needle. In order to insure 
ease in replacing the fibre, the front coil is hinged 
as shown. The fibre D, is supported on E, one 
end of which it is free to turn, so as to permit of 
the removal of torsion; D, being twisted can be 
raised or lowered at E. The needle system with 
heavy bell-shaped magnet is shown in Fig. 270. 

Galvanometer, Combined Tangent and 

Sine A galvanometer furnished with 

two magnetic needles of different lengths. 
The small needle is used for tangent measure- 
ments, and the long needle for sine measure- 
ments. 

Galvanometer Constant. — (See Constant, 
Galvano?neter.) 

Galvanometer, Dead-Beat A gal- 
vanometer, the needle of which comes quickly 
to rest, instead of swinging repeatedly to-and- 
fro. (See Damping) 

Galvanometer, Deprez-D'Arsonval 

— A form of dead-beat galvanometer. 

The movable part of the Deprez-D'Arsonval 
galvanometer consists of a light rectangular coil 



C, Fig. 271, of many turns of wire, supported 
by two silver wires H J and D E, between the 
poles of a strong permanent horseshoe magnet 
A A. The position of 
the coil may be altered 
as to height by screws 
at H and E. The sup- 
porting wires, prevent 
by their torsion the 
swinging of the coil, as 
does also the cylinder 
of soft iron B, placed 
inside the coil, and sup- 
ported independently 
of it. The movements 
of the coil are observed 
by means of a spot of 
light reflected from a 
mirror J, attached to Fig. 271 
the wire H J. 




Deprez-D' Arson- 
val Galvanometer. 



Galvanometer, Detector A form of 

galvanometer employed for rough testing 
work. 

A form of detector galvanometer is shown in 
Fig. 272. 




Fig. 2 "j 2. Detector Galvanometer. 

Galvanometer, Differential —A gal- 
vanometer containing two coils so wound as 
to tend to deflect the needle in opposite 
directions. 

The needle of a differential galvanometer shows 
no deflection when two equal currents are sent 
through the coils in opposite directions, since, 
under these conditions, each coil neutralizes the 
other's effects. Such instruments may be used 
in comparing resistances. The Wheatstone 
Bridge, however, in most cases, affords a prefer- 
able method for such purposes. (See Bridge, 
Electric. ) 



Gal.] 



249 



[Gal. 



A form of differential galvanometer is shown in 
Fig. 273. , 

Sometimes the current is so sent through the 
two coils, that each 
coil deflects the nee- 
dle in the same di- 
rection. In this case 
the instrument is no 
longer differential in 
action. 

If the magnetic 
needle, in such cases, 
is suspended at the 
exact centre of the 
line which joins the 
centres of the coils, 
the advantage is 
gained by obtaining 
a field of more nearly 
uniform intensity 
around the needle. 

Galvanometer. 




Fig. 273. Differential Galva- 
nometer. 



The reciprocal of the current required to pro- 
duce a deflection of the galvanometer needle 
through one degree of the scale. 

The smaller the current required to produce a 
deflection of one degree, the greater the figure 
of merit, or the greater the sensitiveness of the 
galvanometer. 

Galvanometer, Marine A galva- 
nometer devised by Sir William Thomson for 
use on steamships where the motion of mag- 
netized masses of iron would seriously disturb 
the needles of ordinary instruments. 

An unscreened needle would be so much af- 
fected by the motion of the engines, the shaft and 
the screw, as to be useless for galvanometric 
measurement. 

The needle of the marine galvanometer is 
shielded or cut off from the extraneous fields so 
produced, by the use of a magnetic screen or 
shield, consisting of an iron box with thick sides, 
inside of which the instrument is placed. 

The needle is suspended by means of a silk 
fibre attached both above and below, in line with 
the centre of gravity of the needle. In this man- 
ner, the oscillations of the ship do not affect the 
needle. 

Galvanometer, Mirror A galva- 
nometer in which, instead of reading the de- 
flections of the needle directly by its move- 



ments over a graduated circle, they are read 
by the movements of a spot of light reflected 
from a mirror attached to the needle. 

This spot of light moves over a graduated 
scale, or its movements are observed by means of 
a telescope. 




Fig. 274. Mirror Galvanometer. 

A form of mirror galvanometer designed by Sir 
William Thomson is shown in Fig. 274. The 
needle is attached directly to the back of a light, 
silvered glass mirror, and consists of several small 
magnets made of pieces of a watch spring. The 
needle and mirror are suspended by a single silk 
fibre and are placed inside the coil. A compen- 
sating magnet N S, movable on a vertical axis, is 
used to vary the sensitiveness of the instrument. 
The lamp L, placed back of a slot in a wide 
screen, throws a pencil of light on the mirror Q, 
from which it is reflected to the scale K. 

A form of lamp and scale with slot for light is 
shown in Fig. 275. 




Fig. 2 7 J. Galvanometer Lamp and Scale. 

Galvanometer, Potential A term 

sometimes applied to a voltmeter. (See 
Voltmeter?) 

Galvanometer, Reflecting A term 

sometimes applied to a mirror galvanometer, 
(See Galvanometer, Mirror.) 



Gal.] 



250 



[GaL 



Galvanometer, Sensibility of 



—The 

readiness and extent to which the needle of a 
galvanometer responds to the passage of an 
electric current through its coils. (See Gal- 
vanometer.) 

Galvanometer-Shunt. — (See Shunt, Gal- 
vanometer?) 

Galvanometer, Sine — A galva- 
nometer in which a vertical coil is movable 
around a vertical axis, so that it can be made to 
follow the magnetic needle in its deflections. 

In the sine galvanometer, the coil is moved so 
as to follow the needle until it is parallel with the 
coil. Under these circumstances, the strength 
of the deflecting currents in any two different 
cases is proportional to the sines of the angles of 
deflection. 

A form of sine galvanometer is shown in Fig. 
276. The vertical wire coil is seen at M. A 
needle of any length less than the diameter of the 
coil M, moves over the graduated circle N. The 
coil M, is movable over the graduated horizontal 
circle H, by which the amount of the movement 




Sine Galvanometer. 



necessary to bring the needle to zero is measured. 
The current strength is proportional to the sine 
of the angle measured on this circle, through 
which it is necessary to move the coil M, from its 



position when the needle is at rest in the plane of 
the earth's magnetic meridian, until the needle 
is not further deflected by the current, although 
parallel to the coil M. 

— An instru- 



Galvanometer, Tangent — 

ment in which the deflecting coil consists of 
a coil of wire within which is placed a needle 
very short in proportion to the diameter of 
the coil, and supported at the centre of the 
coil. 




Fig. 277. Tangent Galvanometer. 

A galvanometer acts as a tangent galvanometer 
only when the needle is very small as compared 
with the diameter of the coil. The length of the 
needle should be less than one-twelfth the diameter 
of the coil. 

A form of tangent galvanometer is shown in 
Fig. 277. The needle is supported at the exact 
centre of the coil C. 

Under these circumstances, the strengths of 
two different deflecting currents are proportional 
to the tangents of the angles of deflection. Tan- 
gent galvanometers are sometimes made with 
coils of wire containing many separate turns. 

Galvanometer, Tangent, Ofoach's — - — 

A form of galvanometer in which the deflect- 
ing coil, instead of being in a fixed vertical 
position, is movable about a horizontal axis, 
so as to decrease the delicacy of the instru- 
ment, and thus increase its range of work. 

Galvanometer, Torsion A galva- 
nometer in which the strength of the deflecting 
current is measured by the torsion exerted on 
the suspension system. 

A ball-shaped magnet, shown at the right of 
Fig. 278, is suspended by a thread and spiral 



Gal.] 



251 



[Gal. 



spring between two coils of high resistance, 
placed parallel to each other in the positions 
shown. On the deflection of the magnet, by the 
current to be measured, the strength of the current 
is determined by the amount of the torsion re- 
quired to bring the magnet back to its zero point. 




Fig. 2 J 8. Torsion Galvanometer. 

The angle of torsion is measured on the horizontal 
scale at the top of the instrument. 

In the torsion galvanometer, unlike the electro - 
dynamometer, the action between the coils and the 
movable magnet is as the current strength causing 
the deflection. In the electro-dynamometer, 
since an increase of current in the deflecting coils 
also takes place in the deflected coil, the mutual 
action of the two is as the square of the current 
strength causing the deflection. 

Galvanometer, Upright A gal- 
vanometer, the needle of which moves in a 
vertical plane. (See Galvanometer, Ver- 
tical. 

Galvanometer, Vertical A gal- 
vanometer the needle of which is capable of 
motion ki a vertical plane only. 

In the vertical galvanometer, the north pole of 
the needle is weighted so that the needle as- 
sumes a vertical position when no current is pass- 
ing. In the form shown in Fig. 279, two needles 




Fig, 2JQ. Vertical Galva~ 
nometer. 



are sometimes employed, one of which is placed 
inside the coils C, C. 

The vertical galvanometer is not as sensitive as 
the ordinary forms. It is employed, however, 
in various forms for an 
electric current indica- 
tor, or even for a 
rough current meas- 
urer. 

Galvanometer 
Voltmeter. — An in- 
strument devised by 
Sir William Thom- 
son, for the meas- 
urement of differ- 
ences of electric 
potential. 

This instrument is so arranged that by a single 
correction for the varying strength of the earth's 
field in any place, the results are read at once in 
volts. 

A coil of insulated wire shown at A, Fig. 280, 
has a resistance of over 5,000 ohms. A magnetic 
needle, formed of short parallel needles placed 
above one another, and called a magnetometer 
needle, is attached to a long but light aluminium 
index, moving over a graduated scale. A mova- 
ble, semi-circular magnet B, called the restoring 
magnet, is placed over the needle, and is used 
for varying the effect of the earth's field at any 
point. The sensitiveness of the instrument may 
be varied either by the restoring magnet or by 
sliding the magnetometer box nearer to or further 
away from the coil. 

The voltmeter galvanometer depends for its 
operation on the fact that when a galvanometer 
of sufficiently high resistance is introduced be- 




Fig. 280. Galvanometer Voltmeter. 

tween any two points in a circuit, the current that 
passes through it, and hence the deflection of its 
needle, is directly proportional to the difference 
of potential between such two points. 



tial.] 



252 



[Gas. 



Galvanometers for the commercial measure- 
ments of currents assume a variety of forms. 
They are generally so constructed as to read off 
the amperes, volts, ohms, watts, etc., directly. 
They are called amperemeters or ammeters, volt- 
meters, ohmmeters, wattmeters, etc. For their 
fuller description reference should be had to 
standard works on electrical measurement. 

Galvanonietric. — Of or pertaining to the 
galvanometer. (See Galvanometer.) 

Galvanometrical. — Of or pertaining to the 
galvanometer. (See Galvanometer.) 

Galvanoinetrically. — In a galvanometric 
manner. 

Galvano-Plastics. — (See Plastics, Gal- 
vano.) 

Galvanoplasty. — The art of galvano- 
plastics. (See Plastics, Galvano.) 

Galvano-Puncture. — (See Puncture, Gal- 
vano?) 

Galvanoscope. — A term sometimes im- 
properly employed in place of galvanometer. 

A galvanoscope, strictly speaking, is an instru- 
ment intended rather to show the existence of an 
electric current than to measure it in degrees. 
It may, however, be roughly calibrated, and then 
it differs from a galvanometer only in delicacy 
and accuracy. 

Galvano-Therapeutics. — A term some- 
times used for electro-therapeutics. 

Electro- therapeutics is by far ihe preferable 
term and is almost universally employed in the 
United States. 

Gap, Air A gap, or opening in 

a magnetic circuit containing air only. (See 
Gap, Air, Magnetic?) 

The air gap between two magnetic poles may 
be regarded as the space in which an armature 
acting as a magneto-receptive device is placed, 
which by the action upon it of the lines of mag- 
netic force passing through the gap has differ- 
ences of potential generated in its coils of insulated 



Gap, Air, Magnetic 



-A gap filled 



with air which exists in the opening at any 
part of a core of iron or other medium of high 
permeability. 

The space between the pole pieces and arma- 



ture core is called the air gap in dynamos or 
motors even though partly filled with copper con- 
ductors. It is also called the interference space. 

The gap or air space of an electro-magnet de- 
creases the strength of its magnetization be- 
cause — 

The increased reluctance of the air gap causes 
a decrease in the number of lines of magnetic 
force which pass through the magnetic circuit. 

Gap, Spark A gap forming part of 

a circuit between two opposing conductors, 
separated by air, or other similar dielectric 
which is closed by the formation of a spark 
only when a certain difference of potential 
is attained. 

Gap, Wire-Gauge — (See Gauge, 

Wire, Gap.) 

Gas-Battery. — (See Battery, Gas.) 

Gas Burner, Argand, Plain-Pendant, 

Electric — (See Burner, Argand 

Electric, Plain-Pendant?) 

Gas Burner, Argand, Ratchet-Pendant, 
Electric (See Burner, Argand Elec- 
tric, Ratchet-Pendant.) 

Gas Burner, Automatic Electric 

(See Burner, Auto?natic Electric.) 

Gas Burner, Plain-Pendant, Electric 
(See Burner, Plain-Pendant Elec- 
tric^) 

Gas Burner, Ratchet-Pendant, Electric 
(See Burner, Ratchet-Pendant Elec- 
tric^) . 

Gas, Carbonic Acid A gaseous sub- 
stance formed by the union of one atom of 
carbon with two atoms of oxygen. 

Carbonic acid gas is formed during the com- 
bustion of carbon by a sufficient supply of air. 

Gas, Dielectric Density of A term 

sometimes emploved instead of dielectric 
strength of gas. (See Gas, Dielectric 
Strength of.) 

Gas, Dielectric Strength of The 

strain a gas is capable of bearing without 
suffering disruption, or without permitting a 
disruptive discharge to nass through it. 

The dielectric strength of a gas depends— 

(i.) On the nature of the gas. 

(2.) On its pressure. 



OilS.] 



253 



[Gau. 




It has been calculated roughly that it requires 
40, coo volts per centimetre to pass a disruptive 
discharge through dry air at ordinary pressures. 

Gas-Jet, Carcel Standard (See 

Car eel Standard Gas-jet.) 

Gas-Jet Photometer. — (See Photometer.) 

Gas-Lighting", Electric The electric 

ignition of a gas-jet from a distance. 

Gas-Lighting", Multiple Electric 

A system of electric gas-lighting in which a 
number of gas-jets are lighted by means of 
a discharge of high electromotive force, 
derived from a Ruhmkorff coil or a static 
induction machine. 

Such devices are operated by means of minute 
electric sparks which are 
caused to pass through 
the escaping gas-jets. 

The spark for this pur- 
pose is obtained either by 
means of the extra current 
from a spark coil, by means 
of an induction coil or by 
static discharges. (See 
Currents, Extra. Coil, 
Spark. Coil, Induction.) 

A gas tip for use in multiple gas-lighting ap- 
paratus is shown in Fig. 281. The spark is 
formed immediately over the slot in the burner, 
and therefore ignites the escaping gas. 

Gas, Occlusion of The absorption 

or shutting up of a gas in the pores, or on the 
surfaces of various substances. 

Carbon possesses in a marked degree the prop- 
erty of occluding or absorbing gases in its pores. 
These occluded gases must be driven out from the 
carbon conductor employed in an incandescent 
lamp, since otherwise their expulsion, on the in- 
candesence of the carbon, consequent on the light- 
ing of the lamp, will destroy the high vacuum of 
the lamp chamber and thus lead to the ultimate 
destruction of the filament. (See La?)ip, Electric, 
Incandescent.) 

Gassing. — The evolution of gas from the 
plates of a storage or secondary cell. 

Gastroscope. — An electric apparatus for 
the illumination and inspection of the human 
stomach. 



Fig. 28 1. Multifile Gas- 
jet. 



The light is obtained by means of a platinum 
spiral in a glass tube surrounded by a layer of 
water to prevent undue heating. The platinum 
spiral is placed at the extremities of a tube, pro- 
vided with prisms, and passed into the stomach 
of the patient. A separate tube for the supply 
of air for the extension of the stomach is also 
provided. 

Gastroscopy.— The examination of the 
stomach by the gastroscope. (See Gastro- 
scope?) 

Gauge, Battery. — A form of portable gal- 
vanometer, suitable for ordinary testing work. 
A form of battery gauge is shown in Fig. 282. 




Fig. 282. Battery Gauge. 

Gauge, Electrometer A device em- 
ployed in connection with some of Sir Wil- 
liam Thomson's electrometers to ascertain 
whether the needle, connected with the layer 
of acid that acts as the inner coating of the 
Leyden jar used in connection therewith, is at 
its normal potential. 

Gauge, Wire, American A name 

sometimes applied to the Brown & Sharpe 
Wire Gauge. (See Gauges, Wire, Varieties 
of) 

Gauge, Wire, Birmingham A term 

sometimes applied to one of the English wire 
gauges. 

Gauge, Wire, Gap A wire gauge in 

which gaps are left for the introduction of the 
wire to be measured. 



Gau.] 



254 



[Gau. 



Gauge, Wire, Micrometer 



-A gauge plete turn, the end C, advances towards B, the 



employed for accurately measuring the di- 
ameter of a wire in thousandths of an inch, 
based on the principle of the vernier or mi- 
crometer. (See Fig. 283.) 

The wire to be measured is placed between a 
fixed support B, and the end C, of a long mova- 
ble screw, which accurately fits a threaded tube a. 
A thimble D, provided with a milled head, fits 
over the screw C, and is attached to the upper 
part. The lower circumference of D, is divided 
into a scale of twenty equal parts. The tube A,is 
graduated into divisions equal to the pitch of the 
screw. Every fifth of these divisions is marked 
as a larger division. 

The principle of the operation of the gauge is 
as follows: Suppose the screw has fifty threads to 
the inch, the pitch of the screw, or the distance 
between two contiguous threads, is therefore -^ 
or .02 of an inch. 

One complete turn of the screw will, therefore, 
advance the slfceve D, over the scale a, the .02 of 
an inch. If the screw is only moved through 
one of the twenty parts marked on the end of 
the thimble or sleeve parts, or the ^ of a com- 



°* A 



,,^or.ooiinch. 



Suppose now a wire is placed between B and 
C, and the screw advanced until it fairly fills the 




Fig. 283. Vernier Wire Gauge. 
space between them, and the reading shows two 
of the larger divisions on the scale a, three of the 
smaller ones and three on the end of the sleeve 
D, then 

Two large divisions of scale a = .2 inch 

Three smaller divisions of scale a.. = .06 " 
Three divisions on circular scale 

on D = .003 " 

Diameter of wire .263 

Serious inconvenience has arisen in practice 



NEW LEGAL STANDARD WIRE GAUGE (ENGLISH). 

Tables of Sizes, Weights, Lengths and Breaking Strains of Iron Wire. 



Size on 
Wire 

Gauge, 



7/0, 
6/0, 

5/o, 

4/0. 

3/0. 

2/0 

1/0, 

1 

2 

3 

4 

5 

6 

7 

8 

9 
10 
11 
12 

13 

14 
15 
16 

»7 

18 

*9 



Diameter. 



Inch. 



.500 
.464 
•432 
.400 
•372 
.348 
•324 
.300 
.276 
.252 
.232 
.212 
.192 
.176 
.160 
.144 
.128 
.116 
.104 
.092 
.080 
.072 
.064 
.056 
.048 
.040 
.036 



Millimetres. 



9.4 





Weight of 




Sectional 




Length of 
Cwt. 


area in 






sq. inches. 


100 yards. 


Mile. 






Lbs. 


Lbs. 


Yards. 


.1963 


193-4 


3404 


58 


.1691 


166 


S 


2930 


6 7 


.1466 


144 


4 


2541 


78 


• I2 57 


123 


8 


2179 


9i 


.1087 


107 


1 


1885 


105 


.0951 


93 


7 


1649 


120 


.0824 


81 


2 


1429 


138 


.0707 


09 


9 


1225 


101 


.0598 


5« 


9 


1037 


190 


.0499 


49 


1 


864 


228 


.0423 


4 1 


6 


732 


269 


•0353 


34 


8 


612 


322 


.0290 


28 





502 


393 


.0243 


24 




422 


467 


.0201 


19 


8 


348 


566 


.0163 


16 




282 


700 


.0129 


12 


7 


223 


882 


.0106 


10 


4 


183 


1077 


.0085 


8 


4 


148 


1333 


.0066 


6 


5 


114 


1723 


.0050 


5 




88 


2240 


.0041 


4 




70 


2800 


.0032 


3 


2 


56 


3500 


.0025 


2 


4 


42 


4067 


.0018 


1 


8 


32 


6222 


.0013 


1 


2 


21 


9333 


.0010 


1. 


18 


1 1 200 



Breaking Strains. 



Annealed. 



Lbs. 

10470 

9017 
7814 
6702 
5796 
5072 
4397 
3770 
3190 
2660 

2254 

1883 

1544 

1298 

1072 

869 

687 

564 

454 

355 

268 

218 

172 

131 

97 

67 

55 



Bright. 



Lbs. 
15700 
13525 
11723 
10052 
8694 
7608 
6595 
5655 
4785 
399o 
338r 
2824 
2316 
1946 
1608 

1303 
1030 
845 

680 
532 
402 
326 

257 
197 
i45 
100 



Size on 
Wire 
Gauge. 



7/0 

6/0 

5/o 

4/0 

3/0 

2/0 

1/0 

1 

2 

3 

4 

5 

6 

7 

8 

9 



(Issued by the Iron and Steel Wire Manufacturers' Association.) 



Gau.] 



255 



[Gail. 



from the numerous arbitrary numbers of sizes of 
wires employed by different manufacturers. 
These differences are gradually leading to the 
abandonment of arbitrary sizes for wires and em- 
ploying in place thereof the diameters directly in 
inches or thousandths of an inch. 

— A device for 



Gauge, Wire, Round — 

accurately measuring the diameter of a wire. 

The round wire gauge shown in Fig. 284 is 

very generally used for telegraph lines. Notches 




Fig. 284. Round Wire Gauge. 

for varying widths, cut in the edges of a circular 
plate of tempered steel, serve to approximately 
measure the diameter of a wire, the sides of the 
wire being passed through the slots. Numbers, 
indicating the different sizes of the wire, are 
affixed to each of the 
openings. 

Gauge, Wire, Self- 
Registering A 

wire gauge arranged 
to give the exact di- 
ameter of the wire to 
be measured directly 
without calculation. 

A form of self- register- 
ing wire gauge is shown 
in Fig. 285. The wire 
or plate is inserted in the 
gap between a fixed and Fig. 28s. Wire and 
a movable plate. The Plate Gauge. 

numbers corresponding to the diameter of the 
wire or plate are shown on one side of the gauge 
and the gauge numbers on the other side. 




Gauge, Wire, Standard A wire 

gauge adopted by the National Telephone 
Exchange Association at Providence, R. I., 
and by the National Electric Light As- 
sociation, at Baltimore, Md., in February, 
1886. 

The value of the standard as compared with 
the other gauges will be seen from 'an inspection 
of the table in this column: 

Gauges, Wire, Varieties of The 

following table gives a comparison of the 
principal wire gauges in use. 

COMPARISON OF THE DIFFERENT WIRE 
GAUGES. 



O bJJ 

3 
u rt 


u 
O 


£ . 

Is 

n 


Washburn & 
Moen Mfg. 

Co., Worces- 
ter, Mass. 


£2 

•— ' c • 

£ ° 


t = 

So 

c 
rt « 


SflS 


000000 






. 4 6 








00000 






■43 


■45 






0000 


: 4 6"" 


• 45+ 


•393 


•4 


400 




000 


.40964 


.425 


.362 


•36 


372 




00 


om 


• 38 


•33i 


•33 


348 







•3-2495 


• 34 


•307 


•305 


324 




1 


.2893 


• 3 


.283 


.2S5 


30 j 




2 


•25763 


.284 


.263 


.265 


276 




3 


.22942 


• 259 


.244 


.245 


252 




4 


.20431 


.238 


.225 


.225 


232 




5 


.i8i 94 


.22 


.207 


.205 


212 




6 


.16202 


.203 


.192 


.19 


192 




7 


.14428 


.18 


.177 


•175 


176 




8 


.12849 


.165 


.162 


.16 


160 




9 


"443 


.148 


.148 


•145 


144 




10 


.10189 


.134 


•*35 


•13 


128 




n 


.090742 


.12 


.12 


."75 


116 




12 


.080808 


• 109 


.105 


.105 


104 




13 


o 7 iqni 


.095 


.092 


.0925 


092 




14 


.064084 


.083 


.08 


•08 


080 


.083 


15 


.057068 


.072 


.072 


.07 


072 


.072 


16 


•05082 


.065 


.05 3 


.061 


064 


•065 


17 


•04525' 


.0,8 


.052 


.0525 


056 


.058 


18 


.040303 


.049 


.O47 


•045 


048 


.049 


*9 


.035390 


.042 


.04I 


•039 


040 


.04 


20 


.031961 


.035 


•035 


•034 


036 


•035 


21 


.028462 


.0^2 


.032 


•03 


032 


•0315 


22 


■°25347 


.028 


.028 


.27 


028 


.0295 


23 


.022571 


.025 


.C2 5 


.024 


024 


.027 


24 


.0201 


.022 


.023 


.0215 


022 


.025 


2=; 


.0179 


.02 


.02 


.019 
.018 


020 


.023 


26 


.01594 


.018 


.Ol8 


018 


.0205 


27 


.014195 


.016 


.OI7 


.017 


oi6<i 


.01875 


28 


.012641 


.014 


• Ol6 


.016 


0148 


.0165 


29 


.011257 


.013 


.OI5 


•015 


0136 


•0155 


30 


.010025 


.012 


.OI4 


.014 


0124 


.C1375 


31 


.008028 


.01 


.OI35 


.013 


0116 


.01225 


3 2 


.00795 


.009 


.013 


.012 


0108 


.01125 


33 


.00708 


.008 


.Oil 


.011 


0100 


.01025 


34 


.006304 


.007 


.OI 


.01 


0092 


.0095 


35 


.005614 


.005 


.OO95 


.009 


0084 


.009 


36 


.005 


.004 


.OO9 


.co8 


0076 


.0075 


VJ 


•OO4453 




.O085 


.00723 


0068 


.0065 


38 


.003965 




.008 


.0065 


006 


•00575 


39 


•003531 




•OC75 


• 00575 


005 -> 


.005 


40 


003144 




.OO7 


.005 

I 


004S 


.0045 



tiau.J 



256 



[Gau. 



NUMBER, DIAMETER, WEIGHT, LENGTH AND RESISTANCE OF PURE COPPER 

WIRE. 

American Gauge. 







Weight, sp. gr. =8.889. 


Length. 


Resistance of Pure Copper at 70 


Fahrenheit. 


No. 


Diameter. 
Inches. 














Grs. per it. 


Lbs. per 1,000 
feet. 


Ft. per lb. 


Ohms per 1,000 ft. 


Feet per ohm. 


Ohms per lb. 


oooo. . . 


.46000 


4475-33 


640.40 


1.56 


.051 


19605.69 


.0000798- 


ooo. .. 


.40964 


3549-°7 


507.01 


1.97 


.064 


I5547-87 


.000127 


oo.,.. 


.36480 


2814.62 


402.09 


2.49 


.o8c 


12330.36 


.000202 


o. .. 


.32486 


2233.28 


319.04 


3-i3 


.102 


97"-3-63 


.000320 


I... 


.28930 


1770.13 


252.88 


3-95 


.129 


7754.66 


.00051 


2... 


•25763 


1403.79 


200.54 


4.99 


.163 


6149.78 


.ojo8ii 


3--- 


.22942 


1113.20 


159-03 


6.29 


• 205 


4876.73 


.001289. 


4... 


.20431 


882.85 


1 .-6. 12 


7-93 


•259 


3867.62 


.00205 


5... 


.18194 


700.10 


100.01 


10.00 


.326 


3067 . 06 


.00326 


6... 


.16202 


555- 


79-32 


12.61 


.411 


2432.22 


.00518 


7... 


• 14429 


440.27 


62.90 


15.90 


.519 


1928.75 


.00824 


8... 


.12849 


349.18 


49.88 


20.05 


•654 


1529.69 


.01311 


9... 


•"443 


276.94 


39-56 


25.28 


.824 


1213.22 


.02083. 


10... 


.10190 


2^9-57 


3i-37 


31.88 


1.040 


961.01 


•03314 


11. . . 


.09074 


174-^5 


24.88 


40.20 


1. 311 


762.93 


.05269. 


12. . . 


.08081 


138. 11 


19-73 


50.69 


1-653 


605.03 


•08377 


13--- 


.07196 


109.52 


15-65 


63.91 


2.084 


479 80 


.13321 


14... 


.06408 


86.86 


12.41 


80.59 


2.628 


380.51 


.2118 


15. • 


•05707 


68.88 


9.84 


101.63 


3-314 


3QI-75 


.3368 


16... 


.05082 


54.63 


7.81 


128.14 


4.179 


239-3 2 


•5355 


17... 


•04525 


43-32 


6. 19 


161.59 


5-269 


189.78 


.8515 


18 .. 


. 04030 


34-35 


4.91 


203.76 


6.645 


15050 


1-353* 


19... 


.03589 


26 49 


3-78 


264 . 26 


8.617 


116.05 


2.2772 


20. . . 


.03196 


21.61 


3-°9 


324.00 


10. 566 


94.65 


3-423 


21. .. 


.02846 


I7-I3 


2.45 


408.56 


J 3-323 


75.06 


5,443 


22. .. 


•025347 


13-59 


1.94 


sis-js 


16.799 


59-53 


8.654 


23... 


.022572 


10.77 


i-54 


649.66 


21.185 


47.20 


I3-76? 


24... 


.0201 


8-54 


1.22 


819.21 


26.713 


37-43 


21.885 


25-.. 


.0179 


6.78 


•97 


1032.96 


33 684 


29.69 


34-795 


26... 


•oi594 


5-37 


•77 


1302.61 


42.477 


23-54 


55-331 


27... 


.014195 


4.26 


.61 


1642.55 


53-563 


18.68 


87.979 


28... 


.012641 


3-38 


.48 


2071.22 


67.542 


14.81 


i39-893 


29... 


.011258 


2.68 


.38 


2611.82 


85.170 


11.74 


222.449 


30... 


.010025 


2.13 


•30 


3293-97 


107.39: 


9-3 1 


353-742 


3i •• 


.008928 


1.69 


.24 


4152.22 


135.402 


7-39 


562.221 


32... 


.00795 


1-34 


.19 


5236.66 


170.765 


5.86 


894.242 


33--- 


.00708 


1.06 


•15 


660.271 


215.312 


4.64 


1421.646 


34... 


.0063 


.84 


. 12 


8328.30 


271.583 


3.68 


2261.82 


35- •• 


.00561 


•67 


.10 


10501.35 


342-4I3 


2.92 


3596.104 


36... 


.005 


•53 


.08 


13258.83 


431.712 


2.32 


57I5-36 


37--- 


.00445 


.42 


.06 


10691.06 


544.287 


1.84 


9084.71 


38... 


.003965 


•34 


•05 


20854.65 


686.511 


1.46 


14320.26 


39- •• 


•003531 


.27 


.04 


26302.23 


865.046 


1.16 


22752.6 


40... 


.003144 


.21 


•03 


33175-94 


1091.865 


.92 


36223.59 



Gauss.- 

field. 



-The unit of intensity of magnetic 



The term gauss for unit of intensity of mag- 
netic field was proposed by S. P. Thompson as 
being that of a field whose intensity is equal to 
108 C. G. S. units, that is, io« lines of force per 
square centimetre. 

J. A. Fleming proposes, for the value of the 
gauss, such strength of field as would develop an 
electromotive force of one volt in a wire one 
million centimetres in length, moving through 
such a field with unit velocity. 

Fleming's value for the'gauss was assumed on 
account of the small value of the gauss proposed 



by S. P. Thompson. It is one hundred times 
greater in value than Thompson's gauss. 

Sir William Thomson proposes, for the value of 
the gauss, such an intensity of magnetic field as is 
produced by a current of one weber (ampere) at 
the distance of one centimetre. 

Gauss, Fleming's Such a strength 

of magnetic field as is able to develop an 
electromotive force of one volt in a wire one 
million centimetres in length moved through 
the field with unit velocity. (See Gauss.) 

Gauss, S. P. Thompson's Such a 

strength of magnetic field that its intensity 
is equal to 10 s C. G. S. units. (See Gauss.) 



Gail.] 



257 



[Gen. 



Gauss, Sir William Thomson's 

Such an intensity of magnetic field as would be 
produced by a current of one ampere at the 
distance of one centimetre. (See Gauss.) 

Geissler Mercurial Pump.— (See Pump, 

Air, Geissler, Mercurial?) 

Geissler Tubes.— (See Tubes, Geissler) 

General Faradization.— (See Faradiza- 
tion, General) 

General Galvanization.— (See Galvaniza- 
tion, General) 

Generation of Current by Dynamo-Elec- 
tric Machine.— (See Curre?it, Generation of, 
by Dynamo-Electric Machine) 

Generator, Dynamo-Electric An 

apparatus in which electricity is produced by 
the mechanical movement of conductors 
through a magnetic field so as to cut the 
lines of force. 

A dynamo-electric machine. (See Machine, 
Dyna mo-Electric) 

A dynamo electric machine operates on the 
general principles ot electro-dynamic induction. 
Strictly speaking, however, in a dynamo-electric 
generator the conductors are actually moved 
through the lines of force. In this respect, there • 
fore, a dynamo-electric generator differs from a 
transformer, in which the lines of force are moved 
through the conductor. (See Induction, Electro- 
Dynamic. Transformer. Inauction, Mutual) 

Generator, Motor A dynamo-elec- 
tric generator in which the power required to 
drive the dynamo is obtained from an elec- 
tric current. 

Motor generators are used in systems of elec- 
trical distribution for the purpose of changing 
the potential of the current. They consist of 
dynamos, the armatures of which are furnished 
with two separate windings, of fine and coarse 
wire respectively. One of these, generally the 
fine wire, receives the driving or motor cur- 
rent, usually of high potential, and the other, 
the coarse wire, furnishes the current used, usu- 
ally of low potential. 

The advantage of having the windings, which 
receive the driving current, of fine wire, is to 
enable a current of high potential to be dis- 
tributed ever the line from distant stations to 



places where it is desired to use the energy of the 
current at a much lower potential. 

Motor generators often consist simply of two 
distinct machines mechanically connected, one 
acting as a motor and the other as a dynamo. 

Motor generators are sometimes called dynamo- 
motors or dynamotors. 

Aldrich draws the following distinction between 
a dynamo-motor and a dynamotor : 

(I.) A dynamo-motor is an energy transformer 
with the dynamo and motor in the same electric 
circuit. 

(2.) A dynamotor is an energy transformer with 
the dynamo and motor ia the same magnetic cir- 
cuit. 




Fig. 286, Edison s Pyro-Jlfa netic Generator, 

Generator, Pyro-Magnetic An ap- 
paratus for producing electricity directly from 
heat derived from the burning of fuel. 



flenj 



258 



[Gil. 



The operation of the pyro-magnetic generator 
is dependent upon the fact that any variation in 
the number of lines of magnetic force that pass 
through a conductor will develop differences of 
electric potential therein. Such variations may 
be effected either by varying the position of the 
conductor as regards the magnetic field, or by 
varying the magnetic field itself. The latter 
method of generating differences of potential is 
utilized in the pyro-magnetic generator, and is 
effected in it by varying the magnetization of rolls 
of thin iron or nickel by the action of heat. 

A form of pyro-magnetic generator devised by 
Edison is shown in Figs. 286 and 287. 




Fig. 287. Edison's Pyro- Magnetic Generator. 

This apparatus is sometimes called a pyro- 
magnetic dynamo. 

Eight electro -magnets are provided, each with 
an armature consisting of a roll of corrugated 
iron. Each of these armatures is provided with 
a coil of insulated wire wound on it and pro- 
tected by asbestos paper. The armatures pass 
through two iron discs as shown. The armature 
coils are connected in series in a closed -circuit, 
the wires from the coils being connected with 
metallic brushes that rest on a commutator sup- 
ported on a vertical axis. A pair of metallic 
rings is provided above the commutator to carry 
off the current generated. 

The vertical axis is provided below with a semi- 
circular screen called a guard plate which rotates 
with the axis and cuts off or screens one half the 
iron armatures from the heated air. 

When the axis is rotated, the difference in the 



magnetization of the armatures, when hot and 
cold, develops electromotive forces which result 
in the production of an electric current. 

Generator, Secondary A term fre- 
quently employed for a converter or trans- 
former. 

The word transformer is now almost univer- 
sally employed. (See Transformer.) 

Generator, Watt A term sometimes 

employed for stating the power in watts that 
any electric source is capable of producing. 

Estimating the power of a dynamo-electric 
machine by the number of watts it is capable of 
producing is very convenient in practice, and is 
now very generally adopted. A dynamo capable 
of furnishing a difference of potential of 1,000 
volts, and a current of 10 amperes, would be said 
to be a 10,000 watt-generator. 

The term watt-generator, though applicable to 
the case of any electric source, is in practice 
generally limited to the case of dynamo-electric 
machines or secondary batteries. 

Generators, Motor, Distribution of Elec- 
tricity by (See Electricity, Distribu- 
tion of, by Motor Generators^ 

Geographical Distribution of Thunder 
Storms. — (See Storms, Thunder, Geograph- 
ical Distribution of.) 

Geographical Equator. — (See Equator, 
Geographical.) 

Geographical Meridian. — (See Meridian, 
Geographical^) 

German Silver Alloy. — (See Alloy, Ger- 
man Silver.) 

Gilding, Electric The electrolytic 

deposition of gold on any object. 

Electro-plating with gold. (See Plating, 
Electro.) 

The surfaces of the object to be gilded are 
made electrically conducting, if not already so, 
and are then connected to the negative terminal 
of a voltaic cell or other source, and immersed in 
a plating bath containing a solution of a salt of 
gold, directly opposite a plate of gold, connected 
with the positive terminal of the source. The 
objects to be plated thus become the kathode, and 
the plate of gold the anode of the plating bath. 
On the passage of a suitable current, the gold is 
dissolved from the plate at the anode and deposited 



Oil.] 



259 



[Gov. 



on the object at the kathode. (See Bath, Gold. 
Kathode. Anode. ) 

Gilt Plumbago. — (See Plumbago, Gilt) 

Gimbals. — Concentric rings of brass, sus- 
pended on pivots in a compass box, and on 
which the compass card is supported so as to 
enable it to remain horizontal notwithstand- 
ing the movements of the ship. (See Com- 
pass, Azimuth) 

Each ring is suspended on two pivots placed 
directly opposite each other, that is, at the ends 
of a diameter, which in one ring is at right angles 
to that in the other. 

Girder Armature. — (See Armature, Gir- 
der) 

Globe, Vapor, of Incandescent Lamp 
A glass globe surrounding the cham- 
ber of an incandescent electric lamp, for the 
purpose of enabling the lamp to be safely- 
used in an explosive atmosphere, or to permit 
the lamp to be exposed in places where water 
is liable to fall on it. 

Such a vapor globe is shown in Fig. 288. In 
the event of accidental breakage of the outside 
globe, the lamp chamber 
proper prevents the igni- 
tion of the explosive 
gases. In such cases, 
however, the outer pro- 
tecting chamber should 
be promptly replaced. 

In some forms of vapor 
globes, a valve is pro- 
vided, opening outwards, 
in order to permit the ex- 
panded air to escape 
when a given pressure is 
reached, and yet, at the 
same time, to prevent the 
entrance of gas or vapor 
from without. 

Glow Discharge.— 
(See Discharge, Glow.) 

Glow Lamp. — (See Lamp, Electric Glow.) 

Gold Bath.— (See Bath, Gold.) 

Gold-Leaf Electroscope. — (See Electro- 
scope, Gold-Lea/.) 

Gold-Plating-. — (See Plating, Gold) 
Gong-, Electro-Mechanical A gong 




Fig, 2S8 Vapor Globe. 



struck or operated by mechanical force at 
times which are dependent on the passage of 
an electric current. 

The motive power is the mechanical force de- 
veloped by a bent spring, the fall of a weight, 
etc., and, by suitable mechanism, is permitted to 
act only on the passage of an electric current. 

Governor, Centrifugal A device for 

maintaining constant the speed of a steam 
engine or other prime mover, despite sudden 
changes in the load or work. 

In a ball governor, any increase in speed 
causes the balls to fly out from the centre of rota- 
tion by centrifugal force. This motion is utilized 
to control a valve or other regulating device. If 
the speed of the engine falls, the balls move 
towards the centre, shifting the valve or regulat- 
ing device in the opposite direction. 

Governor, Current A current regu- 
lator. 

A device for maintaining constant the cur- 
rent strength in any circuit. 

Current governors are either automatic or non- 
automatic. (See Regulation, Automatic.) 

Governor, Electric A device for 

electrically controlling the speed of a steam 
engine, the direction of current in a plating 
bath, the speed of an electric motor, the re- 
sistance of an electric circuit, the flow of 
water or gas into or from a containing vessel, 
or for other similar purposes. 

The particular form assumed by the apparatus 
varies with the character of the work it is intended 
to accomplish. In some cases an ordinary ball 
or centrifugal governor is employed to open or 
close a circuit; or, a mass of mercury in a rotat- 
ing vessel is caused, at a certain speed, to open or 
close a circuit; or, the resistance of a bundle of 
carbon discs is caused to vary, either by pressure 
produced by centrifugal force, or by the move- 
ment of an armature. 

Governor, Periodic A name ap- 
plied by Ayrton & Perry to a form of gover- 
nor for an electric motor, in which the cur- 
rent is automatically cut out for a certain 
portion of each revolution. 

Governor, Spasmodic — A name 

given by Ayrton & Perry to a form of gover- 
nor for an electric motor, in which the cur- 



Gov.] 



260 



[Gra- 



rent is automatically cut off in proportion as 
the work is cut off. 

The spasmodic governor consists essentially of a 
cone dipping into the surface of mercury in a rotat- 
ing vessel. As the speed of the governor increases 
on a lightening of the load, the surface of the mer- 
cury is curved by the increased centrifugal force, 
until finally the mercury leaves the contact point 
and thus cuts off the current. 

Governor, Steam, Electric A de- 
vice used in connection with a valve to so 
electrically regulate the supply of steam to an 
engine, that the engine shall be driven at 
such a speed as will maintain either a con- 
stant current or a constant potential. 

In the electric governor, the steam valve is 
operated by an electro-magnet, whose coils, in 
the case of a constant current machine, are of 
thick wire placed in the main circuit, and, in 
that of a constant potential machine, are of thin 
wire placed in a shunt around the mains. 

Graduators. — Devices, generally electro- 
magnetic, employed in systems of simultane- 
ous telegraphic and telephonic transmission 
over the same wire, so inserted in the line cir- 
cuit as to obtain the makes and breaks re- 
quired in a system of telegraphic communi- 
cation so gradually that they fail to sensibly 
influence the diaphragm of a telephone placed 
in the same circuit. 

Gramme. — A unit of weight equal to 
1543235 grains. 

The gramme is equal to the weight of one cubic 
centimetre of pure water at the temperature of its 
maximum density. It has various multiples and 
decimal divisions — of the former, the kilogramme 
or one thousand grammes is the most frequently 
used; of the latter, the centigramme or the one- 
hundredth of a gramme, and the milligramme or 
the one-thousandth of a gramme. (See Weights 
and Measures, Metric System of.) 

Gramme Atom.— (See Atom, Gramme) 

Gramme 'Molecule. — (See Molecule, 
Gramme) 

Gramophone. — An apparatus for record- 
ing and reproducing articulate speech. (See 
Phonograph) 

Gramophone Record. — (See Record, 
Gramophone) 



Graphite.— A soft variety of carbon suit- 
able for writing on paper or similar surfaces. 

Graphite is the material that is employed for 
the so-called black lead of lead pencils. It is 
sometimes called plumbago. Strictly speaking, 
the term graphite is only applicable to the variety 
of plumbago suitable for use in lead pencils. 

Graphite is used for rendering surfaces to be 
electro-plated, electrically conducting, and also for 
the brushes of dynamos and motors. For the 
latter purpose it possesses the additional advantage 
of decreasing the friction by means of its marked 
lubricating properties. 

Graphophone, Micro A modifica- 
tion of the phonograph in which, instead of a 
single diaphragm, a number of separate non- 
metallic diaphragms are caused to act on a 
single diaphragm to record the speech, so that 
the separate diaphragms can be thrown into 
strong vibration when reproducing the speech. 

Graphophone, Phonograph A term 

sometimes applied to the graphophone. (See 
Graphophone, Micro. Phonograph) 

Graphophone Record. — (See Record, 
Graphophone) 

Gray's Harmonic Telegraphic Analyzer. 
— (See Analyzer, Gray's Harmonic Tele- 
graphic) 

Gray's Harmonic Telegraphy. — (See Te- 
legraphy, Grays Harmonic Multiple) 

Gravitation. — A name applied to the force 
which causes masses of matter to tend to 
move towards one another. 

This motion is assumed to be that of attraction, 
that is, the bodies are assumed to be drawn to- 
gether. It is not impossible, however, that they 
may be pushed together. 

Gravitation, like electricity, is well known, so 
far as its effects are concerned ; but, as to the true 
cause of either, particularly the former, we are in 
comparative ignorance. 

The general facts of gravitation may be suc- 
cinctly stated by the following law, generally 
known as Newton's law. 

Every particle of matter in the universe is at- 
tracted by every other particle of matter, and 
itself attracts every other particle of matter, with 
a force which is directly proportional to the pro- 
duct of the masses of the two quantities of matter 



tira.] 



261 



[Gua. 



and inversely proportional to the square of the 
distance between them. 

Gravity Ammeter. — (See Ammeter, Grav- 
ity) 

Gravity, Centre of The centre of 

weight of a body. 

Bodies supported at their centres of gravity are 
in equilibrium, since their weight is then evenly 
distributed around the point of support. 

Gravity-Drop Annunciator. — (See An- 
nunciator, Gravity-Drop) 

Gravity, Yoltaic Cell (See Cell, 

Voltaic, Gravity?) 

Gravity Voltmeter. — (See Voltmeter, 
Gravity?) 

Great Calorie. — (See Calorie, Great) 

Grenet Toltaic Cell.— (See Cell, Voltaic, 
Grenet) 

Grid. — A lead plate, provided with perfor- 
ations, or other irregularities of surface, and 
employed in storage cells for the support of 
the active material. 

The support provided for the active material 
on the plate of a secondary or storage cell. 

The grid receives its name from its resemblance 
to a gridiron. The active material is generally 
maintained on the grid by means of variously 
shaped apertures or holes. These are generally 
larger near the centre, so as to prevent the falling 
out of the material after it has been hardened by 
compression. (See Cell, Secondary. Cell, Stor- 
age.) 

Various forms have been given to the grid. 
The object of these forms, in general, is to in- 
sure the retention of the active material by the 
grid. 

The grids are preferably suspended from suit- 
able supports fastened to the top of the battery 
jars, instead of resting on the bottom of the bat- 
tery jars. 

Grip, Cable A grip provided for 

seizing the end of a cable when it is to be 
drawn into a duct or conduit. 

Grove's Voltaic Cell. — (See Cell, Voltaic, 
Grove.) 

Grothuss' Hypothesis. — (See Hypothesis, 
Grothuss'.) 



Ground Circuit— (See Circuit, Ground.) 

Ground Detector.— ( See Detector, 
Ground) 

Ground or Earth.— A general term for 
the earth when employed as a conductor, or 
as a large reservoir of electricity. 

The term ground is also applied to a fault 
caused by an accidental and undesired connection 
between an electric circuit, line or apparatus and 
the ground. (See Fault.) 

Ground Plate of Lightning Protec- 
tor. — (See Plate, Ground, of Light fling 1 
Protector.) 

Ground-Return. — A general term used 
to indicate the use of the ground or earth 
for a part of an electric circuit. 

The earth or ground which forms part of 
the return path of an electric circuit. 

The ground-return is generally used in the 
Morse system of telegraphy as practiced in the 
United States. 

Ground- Wire. — The wire or conductor 
leading to or connecting with the ground or 
earth in a grounded circuit. 

This is sometimes called an earth-grounded 
wire. 

A circuit is grounded when it is completed in 
part by the ground or earth. 



Grounded Circuit. 

Grounded.) 



(See Circuit, 



Growth or Expansion of Lines of Force. 

— (See Force, Lines of, Growth or Expan- 
sion of) 



Guard, Fan 



-A wire netting placed 



around the fan of an electric motor for the 
purpose of preventing its revolving arms 
from striking external objects. 

Guard, Lightning- A term some- 
times used for lightning rod. (See Rod, 

Lightning.) 

Guard, Transformer, Lightning — 

A transformer lightning arrester. (See Ar- 
rester, Lightning, Transformer) 



Giia.] 



262 



[Hal. 



Guard, Wire Shade A guard of 

wire netting provided for the protection of a 
shade. 

A form of wire shade is shown in Fig. 289. 




Fig. 28Q. Wire Shade Guard. 

Gutta-Percha. — A resinous gum obtained 
from a tropical tree, and valuable electrically 
for its high insulating powers. 

Gutta-percha readily softens by heat, but on 



cooling becomes hard and tough. Unlike India- 
rubber, it possesses but little elasticity. Its 
specific inductive capacity is 4.2, that of air being 
1, and of vulcanized rubber, 2.94. (See Capacity, 
Specific Inductive.) 

Gutta-percha is obtained largely from the East 
Indies, from a tree which yields a brownish gum. 
It is a fibrous and tenacious substance with but 
little flexibility, and is unaffected by acids. Oils 
produce less effect upon it than on India-rubber. 

Gutta-percha is one of the best insulating mate- 
rials known for sub-aqueous cables. 

Gymnotus Electricus.— The electric eel. 
(See Eel, Electric?) 

Gyrometer.— A speed indicator. (See In- 
dicator, Speed?) 



H. — A contraction for the horizontal inten- 
sity of the earth's magnetism. 

H. — A contraction proposed for one unit 
of self-induction. 

H. — A contraction used in mathematical 
writings for the magnetizing force that exists 
at any point, or, generally, for the intensity of 
the magnetic force. 

The letter H, when used in mathematical 
writings or formulae for the intensity of the 
magnetic force, is always represented in bold or 
heavy faced type, thus : H . 

H-Armature Core. — (See Core, Arma- 
ture, H.) 
Hail, Assumed Electric Origin of 

A hypothesis, now generally rejected, framed 
to explain the origin of the alternate coatings 
of ice and snow in a hail stone, by the alter- 
nate electric attractions and repulsions of 
the stones between neighboring, oppositely 
charged, snow and rain clouds. 

It is now generally recognized that the electric 
manifestations attending hail storms are the 
effects and not the causes of the hail. (See Para- 
greles.) 

Hair, Electrolytic Bemoral of — = 

The permanent removal of hair from any part 



of the body, by the electrolytic destruction of 
the hair follicles. 

A platinum negative electrode is inserted in the 
hair follicle and the positive electrode, covered with 
moist sponge or cotton, is held in the hand of the 
patient. A current of from two to four milli-am- 
peres from a battery of from eight to ten Le- 
clanche elements is then passed for from ten to 
thirty seconds. A few bubbles of gas appear, 
and the hairs are then removed from the follicles 
by a pair of forceps. (See Milli- Ampere.) 

When the work is properly done there is no 
destruction of the skin and therefore no marks or 
scars. 

In the removal of hair from the face, it is pref- 
erable that the current should slowly reach its 
maximum strength. 

Half-Shades for Incandescent Lamps. 

— Shades for incandescent electric lamps, in 
which one-half of the lamp chamber proper 
is covered with a coating of silver, or other 
reflecting surface for reflecting the light, or is 
ground for the purpose of diffusing the light. 
The half-shade is applicable to cases where it 
is desired to throw out the light, not in all direc- 
tions, but on one side only of any plane. Some- 
times the dividing plane is taken parallel to the 
length of the incandescing filament and sometimes 
at right angles to it. When the lamp is placed 



Hal.J 



263 



[Hea. 



within a surrounding globe the reflecting surface 
may be placed on this globe instead of on the 
lamp chamber. 

Hall Effect— (See Effect, Hall.) 

Halleyan Lines. — (See Lines, Halleyan.) 

Halpine-Savage Torpedo.— (See Torpedo, 
H alp me- Savage.) 

Haudliole of Conduit.— A box or opening 
communicating with an underground cable, 
provided for readily tapping the cable, and 
of sufficient size to permit of the introduction 
of the hand. 

Hand-Lighting- Argand Electric Burner. 
— (See Burner, Argand Electric, Ha?id- 
Lighter?) 

Hand-Lighting Electric Burner. — (See 
Burner, Hand- Lighting Electric.) 

H a n d - R e gulation. — ( See Regulation, 
Hand.) 

Hand-Regulator. — (See Regulator, 
Hand.) 

Hanger-Board. — (See Board, Hanger.) 

Hanger, Cable A hanger or hook 

suitably secured to the cable and designed to 
sustain the weight 
of the cable by 
intermediately sup- 
porting it on iron or 
steel wires strung 
above the cable. 

A cable hanger or 
cable clip is shown in 
Fig. 290. The mode 
of supporting the cable 
C, by the hanger hook 
H, will be readily un- 
derstood from an in- 
spection of the figure. Fis ' 29 °' Cable Hanger ' 

The weight per foot of an aerial cable is gener- 
ally so great that the poles or supports would re- 
quire to be very near together, unless the device 
of intermediate supports, by means of cable clips 
or hangers, were adopted. 

Hanger, Double-Curve Trolley A 

trolley hanger generally employed at the ends 
of single and double curves, and on inter- 
mediate points on double track curves, sup- 
ported by lateral strain in opposite directions. 




Hanger, Single-Curve Trolley A 

trolley hanger supported on a single track 
curve, except at the ends and on the inside 
curve of a double track line, by lateral strain 
in one direction. 
Hanger, Straight-Line Trolley A 



trolley hanger on a straight trolley line suit- 
ably supported by a span wire so as to have 
a vertical strain only. 

Hanger, Trolley A device for sup- 
porting and properly insulating trolley wires. 

Hard-Drawn Copper Wire. — (See Wire, 
Copper, Hard-Drawn.) 

Harmonic Receiver. — (See Receiver, Har- 
monic.) 

Harmonic Telegraphy. — (See Telegraphy, 
Grafs Harmonic Multiple?) 

Head Bath, Electric (See Bath, 

Head, Electric?) 

Head Breeze, Electro-Therapeutic 

(See Breeze, Head, Electro- Therapeutic.) 

Head Light, Locomotive, Electric 



An electric light placed in the focus of a par- 
abolic reflector in front of a locomotive engine. 
The lamp is so placed that its voltaic arc is a 
little out of the focus of the reflector, so that, by 
giving a slight divergence to the reflected light, 
the illumination extends a short distance on either 
side of the tracks. 

Heat. — A form of energy. 

The phenomena of heat are due to a vibratory 
motion impressed on the molecules of matter by 
the action of some form of energy. 

Heat in a body is due to the vibrations or 
oscillations of its molecules. Heat is transmitted 
through space by means of a wave motion in the 
universal ether. This wave motion is the same 
as that causing light. 

A hot body loses its heat by producing a wave 
motion in the surrounding ether. This process 
is called radiation. (See Radiation.) 

The energy given off by a heated body cooling 
is called radiant energy. 

Radiant energy is transmitted by means of 
ether waves; it is of two kinds, viz. : 

(1.) Obscure Heat, or heat which does not 
affect the eye, although it can impress a photo- 
graphic image on a sufficiently sensitive photo- 
graphic plate. 



Hea.] 



264 



[Hea. 



(2.) Luminous Heat, or heat which accompanies 
light. (See Energy, Radiant.) 

Heat is conducted, or transmitted through 
bodies, with different degrees of readiness. 

Some bodies are good conductors of heat, 
others are poor conductors. 

Heat is transmitted through liquids by means 
of currents occasioned by differences in density 
caused by differences of temperature. These 
currents are called convection currents. 

Heat is measured as to its relative degree of in- 
tensity by the thermometer. It is measured as to 
its amount or quantity by the calorimeter. (See 
Ther?7io?neter, Elddric. Calorimeter. ) 

The heat unit most commonly employed is, 
perhaps, the calorie, or the amount of heat re- 
quired to raise one gramme of water one degree 
centigrade. 

Another heat unit, very generally employed in 
the United States and England, is the quantity of 
heat required to raise one pound of water one de- 
gree Fahrenheit. This is called the English heat 
unit. (See Calorie. Units, Heat. Joule. Volt- 
Coulomb.') 

Heat, Absorption and Generation of, in 

Yoltaic Cell The heat effects which 

attend the action of a voltaic cell. 

The chemical action of the exciting liquid or 
electrolyte on the positive plate or element of a 
voltaic cell, like all cases of chemical combination, 
is attended by a development of heat. 

When, however, the circuit of the cell is closed, 
the energy liberated during the chemical combi- 
nation appears as electricity, which develops heat 
in all parts of the circuit. (See Heat, Electric. 
Cell, Voltaic.) 



Heat, Atomic 



A constant product 



obtained by multiplying the specific heat of 
an elementary substance by its atomicweight. 
(See Weight, Ato?nic.) 

Dulong and Petit have discovered the remark- 
able fact that the product of the specific heat of 
all elementary substances by their atomic weights 
is nearly the same. The product is called the 
atomic heat, and is about equal to 6.4. 

Dulong and Petit's law may be stated as fol- 
ows, viz.: All elementary atoms require the same 
quantity of heat to heat them to the same number 
of degrees. 

The atomic heat of any body divided by its 
specific heat gives its atomic weight. 



The heat imparted to any body performs three 
kinds of work, viz.: 

(1.) That expended in external work, such, 
for example, as in overcoming the atmospheric 
pressure. 

(2.) That expended in internal work, or in 
overcoming the attractions of the atoms and driv- 
ing them apart. 

(3.) That expended in overcoming the temper- 
ature, or the true specific heat, or heat expended 
in increasing the molecular vis-viva. 

The expenditure of energy is greatest in the 
third head. The exact value of the three factors 
is as yet unknown, and in the opinion of Weber 
and others the correctness of Dulong and Petit's 
law cannot be regarded as being satisfactorily 
established. 

Regnault has proved that Dulong and Petit's law 
is true for compound bodies, i. e., in all compounds 
of similar composition the product of the specific 
heat by the total chemical equivalent is constant. 

The following table from Anthony and Bracket 
illustrates the law of Dulong and Petit: 



Elements. 



Iron .... 

Copper. . 
Mercury- 
Silver ... 
Gold.... 

Tin 

Lead 

Zinc 



Specific Heat 


Atomic 


of Equal Weigh.. 


Weight. 


0.114 


55-9 


0.095 


63-17 


0.0314 (Solid) 


199.71 


0.057 


107.67 


0.0329 


196.15 


0.056 


117. 7 


0.0314 


206.47 


0.0955 


64.9 



Product of 
Specific 

Heat into 
Atomic 
Weight. 



6.372 

6.00T 
6.128 
6.137 

6-453 
6.591 

6.483 
6.108 



"This product— the atomic heat of elements, 
the molecular heat of compounds — has the follow- 
ing physical meaning: Of any substance whose 
atomic or molecular weight we know, we may 
take a number of grammes numerically equal to 
the atomic or molecular weight; for example, 
35-5 grammes of chlorine, 16 grammes of marsh 
gas; we may call such quantity the gramme atom 
or the gramme molecule of the substance. The 
atomic heat or the molecular heat of a substance 
is the number of calories of heat necessary to 
raise the temperature of a gramme atom or a 
gramme molecule of the substance through 1 
degree C."— (Dame//.) 

Heat, Electric The heat developed 

by the passage of an electric current through 
a conductor. 



Hea.] 



2H5 



[Hea. 



Heat is developed by the passage of a current 
through any conductor, no matter what its resist- 
ance may be. 

If the conductor is of considerable length, and 
of good conducting power, the heat developed is 
not very sensible, since it is spread over a consid- 
erable area, and is rapidly lost by radiation. 

H, the heat generated in any conductor of a 
resistance R, by the passage through it of an elec- 
tric current C, is equal to 

H = C 2 R, in watts. 

But one watt = .24 small calorie per second. 

Therefore, the heat which is generated, 
H = C 2 R X -24 calories per second. 

For the case of a uniform wire of circular cross- 
section the resistance R, in ohms is directly pro- 
portional to the length 1, and inversely propor- 
tional to the area of cross-section 7tr 2 , or 



R = ^ ; thati3 > H 



( w • 



The temperature to which a wire of a given re- 
sistance is raised, will of course vary with the 
mass of the wire, its radiating surface, and its 
specific heat capacity. If the same number of 
heat calories are generated in a small weight of a 
conductor, whose radiating surface is small, the 
resulting temperature will of course be far higher 
than if generated in a larger mass provided with 
a much greater radiating surface. In general, 
however, its temperature increases as the square 
of the current strength when the resistance is con- 
stant, and increases as the resistance of the wire 
per unit of length is greater. 

The temperature a wire acquires by the passage 
of a current through it varies inversely as the 
third power of the radius. If two wires of the 
same material have the same lengths, but different 
radii, the temperature, acquired by the pas- 
sage of an electric current, will depend on the 
heat developed per second, less that radiated per 

second. Since the former varies as — ,, and the 

r 2 

latter as r, that is, as 1 X 2ttt, the temperatures 

attained vary as — , and not as — , as frequently 
r 3 r 2 

stated. — (Larden.) 

The current required to raise the temperature 

of a bare copper wire a given number of degrees 

above the temperature of the air is given in the 

following table : 



BARE COPPER WIRES. 

Current required to increase the temperature of a copper 
wire t° Centigrade above the surrounding air, the 
copper wire being bright polished or blackened. 



Diameter in 




Current in 


Amperes. 




Centimetres 








and Mils 








(thousandths of 










an inch). 


t = ] 


°C. 


t = 9°C. 


t = 25 C. 


Cm. 


Mils. 


Bright 


Black 


Bright 


Black 


Bright 


Black 


. 1 


40 


1.0 


1.4 


3-o 


4.1 


4.8 


6.6 


.2 


80 


2.8 


3-9 


8-3 


"•5 


13-5 


18.7 


•3 


120 


5-2 


7.2 


i5-3 


21.2 


24.9 


34-4 


•4 


160 


8.0 


11. 


23.6 


3 2 -7 


38,3 


53-0 


• 


200 


II. I 


15.4 


33-o 


45-7 


53-5 


74-1 


.0 


240 


14. b 


20.3 


43-4 


60.0 


Z?' 3 


97-4 


•7 


280 


18.5 


25.6 


54 6 


75.6 


88. 7 


123 


.8 


310 


22.6 


3i-3 


66.7 


92.4 


108 


!50 


•9 


350 


26.9 


37-3 


79.6 


no 


129 


179 


1.0 


390 


S r -s 


43-6 


93-3 


129 


151 


210 


2.0 


790 


89.2 


i 2 3 


264 


36s 


428 


593 


3-o 


1180 


164 


227 


485 


671 


787 J1090 


4.0 


1570 


252 


349 


74 b 


1035 


121 1 11675 


5-o 


1970 


353 


488 


1043 


1444 


1699 2 343 


6.0 


2360 


463 


642 


I 37 I 


1828 


2225 3080 


7.0 


2760 


584 


808 


1728 


2392 


2803 


3882 


8.0 


3150 


7i4 


988 


2110 


2922 


3422 


4741 


9.0 


354o 


851 


1.78 


2519 


3486 


4088 


5659 


10. 


3940 


997 


1380 


2950 


4084 


4788 


6626 


34-4 
































— {Forbes.) 

Heat, Electric Convection of A 

term employed to express the dissymmetrical 
distribution of temperature that occurs when a 



Hea.] 



26b* 



[Hea. 



current cf electricity is sent through a 
metallic wire, the middle of which is main- 
tained at a constant temperature, and the 
ends at the temperature of melting ice. 

The distribution of heat during the pas- 
sage of a current through an unequally 
heated conductor. 

If the central portions of a metallic bar are 
heated the curve of heat distribution is sym- 
metrical. On sending an electric current through 
the wire it is heated according to Joule's law, 
and the curve of heat distribuiion is still sym- 
metrical. But the current in passing from the 
colder to the hotter parts of the wire produces 
an additional heating effect at this point, and in 
passing from the warmer to the colder parts of 
the wire produces a cooling effect. (See Effect, 
Peltier. Effect, Thomson.) The curve of heat 
distribution is then no longer symmetrical. The 
term Electrical Convection of Heat, has been 
given to the dissymmetrical distribution of heat 
so effected. 

Sir William Thomson, who studied these 
effects, found that the electrical convection of 
heat in copper takes place in the opposite 
direction to that in iron; that is to say, the elec- 
trical convection of heat is negative in iron, (i. e., 
the direction is opposite to that of the current), 
and positive in copper. 

Heat, Irreversible Heat pro- 
duced in a homogeneous conductor by the 
passage of electricity through it. 

This heat, according to Joule's law, is propor- 
tional to the square of the current, and is produced 
no matter in what direction the current is pass- 
ing. In this respect it is unlike the heat pro- 
duced by the passage of electricity through a 
heterogeneous conductor, in which case heat is 
developed or liberated only by the passage of the 
current in a given direction : on the passage of the 
current in the opposite direction, heat being 
absorbed and the temperature lowered. (See 
Heat, Reversible.) 

Heat Lightning. — (See Lightning, Heat?) 



•A variety of radi- 



Heat, Luminous — 

ant energy which affects the eye, as light. 

Radiant heat and light are, in reality, different 
effects produced by one and the same cause, viz., 
by vibrations or waves in the universal ether. 
In general the waves producing heat are of 



greater length and smaller frequency than are 
those producing light. 

Heat, Mechanical Equivalent of 

The amount of mechanical energy, converted 
into heat, that would be required to raise the 
temperature of i pound of water I degree 
Fahr. 

The mechanical equivalence between the 
amount of energy expended and the amount 
of heat produced, as measured in heat units. 

Joule's experiments, the results of which are 
generally accepted, gave 772 foot-pounds as the 
energy equivalent to that expended in raising the 
temperature of I pound of water I degree Fahr. 

Heat, Molecular The number of 

calories of heat required to raise the tempera- 
ture of one gramme-molecule of any sub- 
stance 1 degree C. (See Molecule, Gramme. 
Heat, Atomic?) 

Heat, Obscure A variety of radiant 

energy which does not effect the eye. 

Radiant heat is sometimes divided into lumi- 
nous heat and obscure heat. (See Heat, Lumi- 
nous.) 

Heat, Red ■ — The temperature at 

which a body, whose temperature is gradually 
increasing, begins to glow or to emit red rays 
of light. 

When a refractory solid body is gradually 
heated to incandescence, the red waves of light 
are first emitted, then the orange, and successively 
afterwards the yellow, green, blue, indigo and 
violet, when the body emits white light or is 
white hot. 

Heat, Reversible The heat pro- 
duced in a heterogeneous conductor by the 
passage through it of an electric current in a 
certain direction. 

Reversible heat is produced at the junction of 
two metals, where a difference of potential exists 
between them, or where their heterogeneity is 
greatest. It is called reversible because it de- 
pends upon the direction in which the :urrent 
is passing. If the current be passed in a certain 
direction across the junction, heat is liberated; 
while, if it be passed in the opposite direction, 
heat is absorbed, or cold results. 

Reversible heat effects are seen in the Peltier 
effect. (See Effect, Peltier.) 



Hea.] 



267 



[Kel. 



Heat, Specific — The capacity of a 

substance for heat as compared with the 
capacity of an equal quantity of some other 
substance taken as unity. 

Water is generally taken as the standard for 
comparison, because its capacity for heat is greater 
than that of any other common substance. 

Different quantities of heat are required to 
raise the temperature of a given weight of dif- 
ferent substances through I degree. The spe- 
cific heats of substances are generally compared 
with water or with hydrogen, the capacity of 
these substances for heat being very great. 

According to Dulong and Pettit, the specific 
heat of all elementary atoms is the same. For 
example, the heat energy of an atom of hydrogen 
is equal to that of an atom of oxygen, but since 
a given, mass of hydrogen, under similar condi- 
tions of temperature and pressure, contains sixteen 
times as many atoms as an equal mass of oxygen, 
therefore, when compared weight for weight, 
hydrogen has a specific heat sixteen times greater 
than that of oxygen. 

Or, in general, comparing equal weights, the 
specific heat of an elementary substance is in- 
versely proportional to its atomic weight. (See 
Heat, Atomic.} 



Heat, Specific, of Electricity 

Electricity, Specific Heat of.) 



-(See 



Heat Unit. — The quantity of heat required 
to raise a given weight of water through 
a single degree. 

There are a number of different heat units. 
The most important are: 

(i.) The British Heat Unit, or Thermal Unit, or 
the amount of heat required to raise I pound 
of water I degree Fahr. This unit represents an 
amount of work equal to 772 foot-pounds. 

(2.) The Greater Calorie, or the amount of heat 
required to raise the temperature of i,oco 
grammes of water I degree C. (See Calorie.) 

(3.) The Smaller Calorie, or the amount of heat 
required to raise the temperature of one gramme 
of water 1 degree C. 

(4.) The Joule, or the quantity of heat developed 
in one second by the passage of a current of one 
ampere through a resistance of one ohm. 

I joule equals .0002407 large calories. 

I joule equals. 2407 small calories. 

I foot-pound equals 1.356 joules. 



I pound-Centigrade equals 1884.66 joules. 

1 " - 4 '• 1389.6 foot pounds. 

I " Fahrenheit *' 1047.03 joules. 

Heat Unit, English — (See Units, 

Heat.) 

Heat Unit or Calorie.— (See Calorie-) 

Heat Unit or Joule. — (See Joule) 

Heat, White The temperature at 

which light of all wave lengths from the red 
to the violet is emitted from a heated body, 
and the body, therefore, glows with a white 
light. 

A solid substance heated to white incandescence 
emits a continuous spectrum, i. <?., a spectrum in 
which all the wave lengths of light from the red 
to the violet are present. 

Heater, Electric A device for the 

conversion of electricity into heat for purposes 
of artificial heating. 

Electric heaters consist essentially of coils or 
circuits of some refractory metal through which 
the current is passed. These coils or circuits are 
surrounded by air or finely divided solids, and are 
placed inside metallic boxes or radiators, which 
throw off or radiate the heat produced. 

When employed for the heating of liquids the 
coils are placed directly in the liquid to be 
heated, or are surrounded by radiating boxes 
placed in the liquid. 

Heating- Effects of Currents. — (See Cur- 
rents, Heating Effects of.) 

Hedgehog* Transformer. — (See Trans- 
former, Hedgehog.) 

Hecto-Ampere One hundred am- 
peres. 

Heliograph. — An instrument for tele- 
graphic communication that operates by em- 
ploying flashes of light to represent the dots 
and dashes of the Morse alphabet, or the 
movements of the needles of a needle tele- 
graph to the right or the left. (See Alphabet, 
Telegraphic.) 

The flashes of light are thrown from the sur- 
face of a plane mirror. Motions to the right or 
left may be employed in order to distinguish 
between the dots anil dashes, or the same may be 
effected by the relative durations of the flashes of 



He!.] 



268 



[Hoi. 



light, or by the intervals between successive 
flashes. 

Telegraphic communication has been carried 
on between steamers during foggy weather by 
means of their fog horns; or between locomotives 
by their steam whistles. 

Helix, Dextrorsal A name some- 
times applied to a dextrorsal solenoid. (See 
Solenoid, Dextrorsal.) 

The magnetic polarity of a helix or solenoid 
depends not only on the direction in which the 
current is passed, but also on the direction in 
which the wire is coiled or wound. (See Magnet, 
Electro.) 

Helix, Sinistrorsal A name some- 
times applied to a sinistrorsal solenoid. (See 
Solenoid, Sinistrorsal) 

Hemihedral Crystal.— (See Crystal, Hem- 
ihedral) 

Henry, A The practical unit of self- 
induction. 

It has been generally agreed in the United 
States to call the practical unit of self-induction 
a henry, in place of a secohm or quadrant. 
The name henry should be adopted, not only by 
American electricians, but also by those of other 
countries, since the terms secohm or quadrant 
are contrary to the generally adopted usage of 
employing for such the names of distinguished 
electricians, who have passed from their labors. 

The fact that of all discoverers in the field of self- 
induction, none possesses so great a claim as that of 
Prof. Henry, must be generally acknowledged. 
As early as 1832 he published in Silliman's Jour- 
nal a paper in which he described experiments, 
showing clearly that the spark obtained by break- 
ing the current of a battery, in which along wire 
was interposed, was greater than when a short 
wire was employed, and that this increased length 
of spark was further increased by coiling the wire, 
and that the phenomena were ascribed to the ac- 
tion of the current on itself. 

A committee of the American Institute of 
Electrical Engineers, after careful consideration, 
recommended to the Institute that the value of 
the practical unit of inductance should be equal to 
io^ C. G. S. units of inductance, usually ex- 
pressed by a length equal to one earth quadrant 
or 1 000,000,000 centimetres. 

The value of the practical unit of inductance, 
or the ' • henry, " m3y in some cases be too high for 



convenience; in such cases it may be expressed 
by some fractional dimension, such, for example, 
as milli- henry. 

Hercules Stone.— (See Stone, Hercules) 
Hermetical Seal. — (See Seal, Hermeti- 
cal.) 

Hertz's Theory of Electricity. — (See Elec- 
tricity, Hertz 's Theory of) 

Heterostatic. — A term applied by Sir 
William Thomson to distinguish a form of 
electrometer in which the electrification is 
measured by determining the mutual influ- 
ence of the attraction exerted by the charge 
to be measured and the attraction of an oppo- 
site charge imparted to the instrument by a 
source independent of the charge to be meas- 
ured. 

The term heterostatic distinguishes this form of 
electrometer from an idiostatic instrument, or one 
in which the measurement is effected by deter- 
mining the repulsion between the charge to be 
measured and the repulsion of a charge of the 
same name, i. <?., positive or negative, imparted 
to the instrument from an independent source. 
(See Electrometer.) 

Hick's Automatic Button Repeater.— 

(See Repeaters, Telegraphic) 

High-Bars. — A term applied to those com- 
mutator segments, or parts of commutator 
segments, which, through less wear, faulty 
construction or looseness, are higher than ad- 
joining portions. (See Commutator) 

High-Frequency Currents, Electric Light- 
ing* by (See Lighting, Electric, by 

High-Frequency Currents) 

High Resistance Magnet. — (See Magnet, 
High Resistance) 

High Speed Electric Motor. — (See Mo- 
tor, Electric, High Speed) 

High Tension Electric Fuse. — (See Fuse, 
Electric High Tension) 

Hissing of Arc. — (See Arc, Hissing of) 

Holder for Safety Fuse. — A box or other 
receptacle of refractory material for holding 
a safety fuse, and catching the molten metal 
when fused. 

The holder or fuse box is provided to prevent the 



Hoi.] 



269 



[Hor. 



imolten metal of the fuse from setting fire to any 
combustible material on which it might other- 
wise fall. 

Holders, Carbon, for Arc Lamps 

A clutch or clamp attached to the end of the 
lamp rod or other support, and provided to 
hold the carbon pencils used on arc lamps. 
(See Lamp, Arc, Electric) 

Holders for Brushes of Dynamo-Electric 
Machine.— A device for holding the collect- 
ing brushes of a dynamo-electric machine. — 
(See Machine, Dynamo-Electric) 

Hole, Armature A term sometimes 

applied for armature bore or chamber. (See 
Bore, Armaiure) 

Hole, Armature Bore, Elliptical 

An armature bore or chamber ellipsoidal in 
shape. 

Holohedral Crystal. — (See Crystal, Holo- 
hedral) 

Holtz Machine. — (See Machine, Holtz.) 

Home Station. — (See Station, Home.) 

Homogeneous Current Distribution. — 
(See Current, Homogeneous Distribution of) 

Hood for Electric Lamp. — A hood pro- 
vided for the double purpose of protecting the 




Fig. 2QI. Arc Lamp Hood. 

b)ody of an electric lamp from rain or sun, 
and for throwing its light in a general down- 
ward direction. 

Hoods for arc lamps are generally conical in 
shape. 



A form of hood for an exposed arc lamp is 
shown in Fig. 291. 

Horizontal Component of Earth's Mag- 
netism. — (See Component, Horizontal, of 
Earth's Magnetism) 

Horns, Following, of Pole Pieces of 

a Dynamo - Electric Machine —The 

edges or terminals of the pole pieces of a dy- 
namo-electric machine towards which the 
armature is carried during its rotation. 




Fig. 2Q2. Horns of Dynamo. 

According to S. P. Thompson, the following 
horns, b, d, Fig. 292, are those towards which 
the armature is carried ; the leading horns, a, c, 
those from which it is carried. 

As the change in the magnetic intensity is more 
sudden when the armature is moved from the 
pole pieces, and least when moved towards them, 
it is clear that the leading horns in a dynamo - 
electric machine, and the following horns in an 
electric motor, become heated during rotation by 
the production of Foucault currents. (See Cur- 
rents, Foucaidt. Machine, Dynamo Electric.) 

Horns, Leading, of Pole Pieces of a Dy- 
namo-Electric Machine The edges 

or terminals of the pole pieces of a dynamo- 
electrical machine from which the armature 
is carried during its rotation. 

Thus, in Fig. 292, a and c, are the leading horns 
of the pole pieces. 

Horns of Pole Pieces of Dynamo-Electric 
Machine.— The edges of the pole pieces of a 
dynamo-electric machine towards or from 
which the armature is carried during its rota- 
tion. 

These are called the following and the leading 
horns. 

Horse-Power. — A commercial unit for 
power or rate of doing work. 



Hor.] 



270 



[Hou, 



A rate of doing work equal to 33,000 pounds 
raised 1 foot per minute, or 550 pounds raised 
1 foot per second. 

A rate of doing work equal to 4,562.33 
kilogrammes raised 1 metre per minute. 

A careful distinction must be drawn between 
work and power. The same amount of work 
is done in raising I pound through 10 feet 
whether it be done in one minute or in one hour. 
The power expended or the rate of doing work 
is, however, quite different, being in the former 
case sixty times greater than in the latter. 
1 horse-power = 550 foot-pounds per second. 

" = 33,000 foot-pounds per min- 

ute. 
" = 4,562.33 kilogramme-metres 

per minute. 
" = 745,941 watts. 

" = 1. 01385 metric horse-power. 

Horse-Power, Electric (See Power, 

Horse, Electric?) 

Horse-Power Hour. — (See Hour, Horse- 
Power). 

Horse-Power, Metric A unit of 

power in which rate of doing work is equal 
to 75 kilogramme-metres. (See Horse- 
Power^ 

Horseshoe Electro-Magnet. — (See Mag- 
net, Electro, Horseshoe?) 

Horseshoe Magnet. — (See Magnet, Horse- 
shoe.) 

Hot, Red — Sufficiently heated to 

emit red light only (See Heat, Red.) 

Hot St. Elmo's Fire.— (See Fire, Hot, St. 
Elmo's.) 

Hot, White —Sufficiently heated to 

emit all the colored lights of the spectrum. 
(See Heat, White.) 

Hotel Annunciator. — (See Annunciator, 
Hotel.) 

Hour, Ampere ■ —A unit of electrical 

quantity equal to one ampere flowing for one 
hour. 

The ampere-hour is in reality a unit of quanti- 
ty like the coulomb. It is used in the service of 
electric currents, and is equal to the product of 
the current delivered by the time in hours. The 
ampere-hour is not a measure of energy, but when 



combined with the volt, and expressed in watt 
hours, it is a measure of energy. 

The capacity of any service for maintaining a 
flow of current is measured in ampere-hours. 
Thus, if any service, such as a primary or sec- 
ondary battery, has a capacity of 80 ampere- 
hours, it will supply 8 amperes for ten hours, or 
it may give 10 amperes for eight hours. 

The storing capacity of accumulators is gener* 
ally given in ampere-hours. The same is true of 
primary batteries. 

One coulomb equals .0002778 ampere-hours. 

One ampere-hour equals 3,600 coulombs. 

Hour, Horse-Power A unit of work. 

An amount of work equal to one horse- 
power for an hour. 

One horse power is equal to 1,980,000 foot- 
pounds, or 745.941 watt hours. 

Hour, Kilo-Watt — A unit of electri- 
cal power equal to a kilo-watt maintained for 
one hour. 

Hour, Lamp Such a service of elec- 
tric current as will maintain one electric lamp 
during one hour. 

The number of lamp-hours is obtained by mul- 
tiplying the number of lamps by the average 
number of hours during which the lamps are 
burning. 

The use of lamp-hours is for the purpose of 
estimating the current supplied to a consumer by 
counting the number of hours each lamp is in 
service. 

To convert lamp-hours to watt-hours, multiply 
the number of lamp-hours by the number of 
watts per lamp. The watt hours, divided by 746, 
will then give the electrical horse-power hours. 
(See Hour, Watt.) 

Hour, Watt A unit of electrical 

worko 

An expenditure of an electrical work of 
one watt for one hour. 

Lamp-hours are converted to watt-hours by 
multiplying the number of lamp-hours by the 
number of watts per lamp. (See Hour, Lamp.) 

House Annunciator. — (See Annunciator, 
House.) 

House Main.— (See Main, House.) 
House -Service Conductor.— (See Conduc- 
tor, House-Service.) 



Hou.] 



271 



[Hyp. 



House-Top Fixtures, Telegraphic 



(See Fixtures, Telegraphic House- Top.) 

House Wire. — (See Wire, Housed) 

Hughes' Electro-Magnet.— (See Magnet, 
Electro, Hughes'.) 

Human Body, Electric Resistance of 

— (See Body, Hutnan, Resistance of.) 

Hydro-Electric Bath.— (See Bath, Hydro- 
Electric.) 

Hydro-Electric Machine, Armstrong's 
(See Machine, Armstrong's Hydro- 
Electric.) 

Hydrogen, Electrolytic Hydrogen 

produced by electrolytic decomposition. 

It is the electrolytic hydrogen liberated in a 
voltaic cell at the surface of the negative plate, 
which causes polarization and consequent de- 
crease in the resulting current strength, by rea- 
son both of the counter-electromotive force it 
produces and the increased resistance it produces 
in the cell. 

Electrolytic hydrogen is atomic hydrogen; i. e., 
hydrogen with its bonds open or free. It there- 
fore possesses much stronger chemical affinities 
than does molecular hydrogen. Electrolytic 
oxygen which is evolved at the same time as the 
electrolytic hydrogen has been successfully em- 
ployed in electric bleaching. Hydrogen per- 
oxide is also formed and acts as a bleaching agent. 

Hydrometer or Areometer. — An appa- 
ratus for determining the specific gravity of 
liquids. (See Areometer or Hydrometer.) 

Hydro-Plastics. — (See Plastics, Hydro.) 

Hydro-Plasty. — The art of hydro-plastics. 
(See Plastics, Hydro.) 

Hydrotasimeter, Electric An elec- 
trically operated apparatus designed to show 
at a distance the exact position of any water 
level. 

In most forms of the electric hydrotasimeter a 
float placed in the liquid and connected with an 
electric circuit breaks this circuit, and, at intervals, 
sends positive impulses into the line when rising 
and negative impulses when falling. These are 
registered by means of an index moved by a step- 
by-step motion, positive currents moving it in 
o^e direction and negative currents moving it in 
ihe opposite direction. 



Hygrometer. — An apparatus for determin- 
ing the amount of moisture in the air. 

Hygrometrical. — Of or pertaining to the 
hygrometer. 

Hygrometrically. — In the manner of the 
hygrometer. 

Hypothesis. — A provisional assumption of 
facts or causes the real nature of which is 
unknown, made for the purpose of studying 
the effects of such causes. 

When the facts assumed by a hypothesis can 
be shown to be presumably true the hypothesis 
becomes a theory. A theory, therefore, gives a 
more correct expression of the relations between 
the causes and effects of natural phenomena than 
does a hypothesis. 

Hypothesis, Double-Fluid Electric 

— (See Electricity, Double-Fluid Hypothesis 
of.) 

Hypothesis, Grothiiss' A hypothe- 
sis proposed by Grothiiss to account for the 
electrolytic phenomena that occur on closing 
the circuit of a voltaic cell. 

Grothiiss' hypothesis assumes: 

(i.) That before the electric circuit is closed 
the molecules of the electrolyte are arranged in 
an irregular or unpolarized condition, as repre- 




Fig. SQS- Grotkuss' Hypothesis of Electrolytic Polari- 
zation. 

sented at (i), Fig. 293. These molecules are 
shaded as shown in Fig. 294, to indicate their com- 
position and polarity. 

(2.) When the circuit is closed and a current 



Hyp.] 



272 



[Hys, 




begins to pass, a polarization of the electrolyte, as 
shown at (2), ensues, whereby all the negative 
ends of the molecules of hydrogen sulphate, o 
sulphuric acid, are turned towards the positive 
or zinc plate, and all the positive ends towards 
the negative or copper plate. This, as will be 
seen, will turn the S0 4 ends towards the zinc, 
and the H 2 ends towards the copper. 

(3.) A decomposition of the polarized chain, 
whereby the S0 4 
unites with the zinc 
and the H 2 liberated 
reunites with the S0 4 
of the molecule next 
to it in the chain, and 

its liberated H 3 with Fig. 294.. Conventionalized 
the one next to it, and Molecule, 

so on until the last liberated H 2 in the chain is 
given off at the surface of the copper or negative 
plate. This leaves the chain of molecules as 
shown at (3). 

(4.) A semi-rotation of the molecules of the 
chain, as at (3), until they assume the position 
shown at (4). This rotation is required, since all 
the molecules in (3) are turned with their similar 
poles towards similarly charged battery plates. 

Hypothesis, Single-Fluid Electric 

— (See Electricity, Single-Fluid Hypothe- 
sis of) 

Hypothetical.— Of or pertaining to a hy- 
pothesis. 

Hypsometer. — An apparatus for determin- 
ing the height of a mountain or other eleva- 
tion by ascertaining the exact temperature at 
which water boils at such elevation. 

The use of a thermometer to measure the 
height of a mountain or other elevation is based 
on the fact that a given decrease in the tempera- 
ture of the boiling point of water invariably at- 
tends a given decrease in the atmospheric press- 
ure. Therefore, as the observer goes further 
above the level of the sea, the boiling point of 
water becomes lower, and from this decrease the 
height of the mountain or other elevation may be 
calculated. 

Hypsometrical. — Of or pertaining to the 
hypsometer. 

Hypsometrically. — In the manner of the 
hypsometer. 



Hysteresial Dissipation of Energy.— (See 

Energy, Hysteresial Dissipation of.) 

Hysteresis. — Molecular friction to mag- 
netic change of stress. 

A retardation of the magnetizing or de- 
magetizing effects as regards the causes 
which produce them. 

The quality of a paramagnetic substance 
by virtue of which energy is dissipated on the 
reversal of its magnetization. 

The ratio of magnetic induction to the mag- 
netizing force producing it, or, in other words, 
the magnetic permeability, is greater when the 
magnetizing force is decreasing, than when it is- 
increasing. This phenomenon is seen in the weil 
known retention of magnetism in iron after the 
withdrawal of the force causing the magnetization, 
and was called by Ewing hysteresis, from 
'v6rEpka), to lag behind. 

If a curve is constructed in which the hori- 
zontal abscissas represent the magnetizing force, 
or the magnetizing current to which they are 
proportional, and the vertical ordinates the 
number of lines of induction passing through the 
body that is being magnetized, both in the case 
of gradually increasing and gradually decreasing 
currents, the curve will be found to have greater 
values for the decreasing than for the increasing 
current. Constructing a curve in this manner for 
the case of a ring of 
iron, which has been 
first suddenly magnet- 
ized and then demag- 
netized, taking the 
magnetizing force along 
the line F H, Fig. 
295, and the result- 
ing magnetization 
along the line M N, a 
loop is formed in the 
curve, as shown in the 
figure. The arrows 
show the direction of Fig. 295. Curves of Hys- 
the magnetizing force; teresis (Ewing). 

the shaded area the work done due to hysteresis. 

The area of this loop represents the amount of 
energy per unit of volume expended in perform- 
ing a magnetic cycle, i. <?., in carrying the iron 
ring through a magnetization and subsequent 
demagnetization. 

The physical meaning of the loop is that a lag- 




Hys.] 

ging of magnetization has occurred. This lag- 
ging of the magnetization is due to hysteresis. 
Ewing gives the value for the energy in ergs 
dissipated per cubic centimetre, for a complete 
magnetic cycle for a number of substances, as 
follows : 

Energy dissipatpd 
in ergs per cubic 
centimetre, during 
a complete cycle of 
doubly reversed 
strong magnetiza- 
Sample of Iron operated upon. tion. 

Very soft annealed iron 9,300 ergs. 

Less soft annealed iron 16,300 " 

Hard drawn steel wire 60.000 " 

Annealed steel wire 70,500 " 

Same steel, glass hard 76,000 " 

Piano-forte steel wire, normal 

temper 116,000 " 

Same, annealed . 94,000 ' ' 

Same, glass hard 117,000 " 

Approximately 28 foot-pounds of energy are 
required to make a double reversal of strong 
magnetization in a cubic foot of iron. Energy 
expended in this way takes the form of heat. 
This heat, however, is to be distinguished from 
heat produced by Foucault currents. 

According to Ewing, hysteresis is greatly de- 
creased by keeping the iron in a state of mag- 
netic vibration. In this way, the energy dis- 
sipated in a complete magnetic cycle is corre- 
spondingly decreased. This observation of Ewing 
agrees with the prior observation of Hughes, who 
noticed that tapping or twisting a bar of iron 
greatly accelerates the removal of its residual 
magnetism. 

The phenomena of hysteresis, according to 
Fleming, accounts for part of the energy which 
is dissipated in a dynamo-electric machine: 

(1.) In the field magnets. 

In an ordinarily constructed continuous- current 
dynamo, work is done in magnetizing the field 
magnets; not only to give the iron its initial mag- 
netism, but also to constantly reproduce the mag- 
netism which the machine loses by reason of the 



273 



[Hys. 



continual vibrations to which it is subjected dur- 
ing its run. If sufficient residual magnetism 
were retained, on the withdrawal of the magneti- 
zing force there would be no necessity for the 
current in the field magnets ; but, since this is 
removed by even a small vibration, the energy of 
the exciting current must needs be expended. 

(2.) In the armature of the dynamo. 

The soft iron of the core is subjected to succes- 
sive magnetizations and demagnetizations. Ac- 
cording to Fleming, in the case of a core having 
a volume of 9,000 cubic centimetres, with fifteen 
reversals per second, the loss is equal to about £ 
horse-power. 

Hysteresis, Static That quality in 

iron, or other paramagnetic substance, by 
virtue of which. energy is dissipated during 
every reversal of its magnetization. 

Static hysteresis is so named in order to dis- 
tinguish it from viscous hysteresis. (See Hystere- 
sis, Viscous.) 

Hysteresis, Viscous The time-lag 

observed in magnetizing a bar of iron, 
which is referable neither to induction in the 
iron, nor to self-induction in the magnetizing 
current, but to the magnetic viscosity of the 
substance. 

A sluggishness exhibited by iron for mag- 
netization or demagnetization due to magnetic 
viscosity. 

The difference between static and viscous 
hysteresis is thus stated by Fleming in consider- 
ing the analogous mechanical case of lifting a 
weight in a viscous fluid. "Apart from fluid 
resistance, the work done in lifting the weight 
against gravity, say one hundred times, is a hun- 
dred times the work required to be spent to lift 
it once ; but if fluid resistance comes into play, 
and if this varies as the square of the velocity of 
the moving body, then the total work done in 
lifting the weight through the fluid will be de- 
pendent also upon the rate at which the cycle is 
performed." 



Ihp.] 



274 



[111. 



I. H. P. — A contraction for indicated horse- 
power, or the horse-power of an engine as 
obtained by the means of an indicator card. 

I. W. G. — A contraction for Indian wire 
gauge. 

Idio-Electrics. — A name formerly applied 
to such bodies as amber, resin or glass, which 
are readily electrified by friction, and which 
were then supposed to be electric in them- 
selves. 

This distinction was based on an erroneous 
conception, and the word is now obsolete, 

Idiostatic. — A term employed by Sir Wil- 
liam Thomson to designate an electrometer 
in which the measurement is effected by de- 
termining the repulsion between the charge 
to be measured and that of a charge of the 
same sign imparted to the instrument from 
an independent source. (See Heterostatic) 

Idle Poles.— (See Poles, Idle) 

Igniter, JaMochkoff A small strip 

of carbon, or some carbonaceous material 
that is readily rendered incandescent by the 
current, placed between the free ends of the 
parallel carbons of a Jablochkoff candle, for 
the establishment of the arc on the passage 
of the current. 

The igniter is necessary in the Jablochkoff elec- 
tric candle, since the parallel carbons are rigidly 
kept at a constant distance apart by the insulat- 
ing material placed between them, and cannot 
therefore be moved together as in the case of the 
ordinary lamp. (See Candle, Jablochkoff.) 

Ignition, Electric The ignition of 

a combustible material by heat of electric 
origin. 

The electric ignition of wires is generally ac- 
complished by electric incandescence. Ignition 
may be accomplished by the heat of the voltaic 
arc. {See If eat. Electric. Furnace, Electric.) 

The ignition of combustible gases is accom- 
plished by the heat of the electric spark. (See 
Burner, Automatic, Electric.) 

Illumination, Artificial The em- 
ployment of artificial sources of light. 



A good artificial illuminant should possess the 
following properties, viz.: 

(i.) It should give a general or uniform illumi- 
nation as distinguished from sharply marked 
regions of light and shadow. 

To this end a number of small lights well dis- 
tributed are preferable to a few large lights. 

(2.) It should give a steady light, uniform in 
brilliancy, as distinguished from a flickering, 
unsteady light. Sudden changes in the intensity 
of a light injure the eyes and prevent distinct 
vision. 

(3.) It should be economical, or not cost too 
much to produce. 

(4.) It should be safe, or not likely to cause 
loss of life or property. To this intent it should, 
if possible, be inclosed in or surrounded by a 
lantern or chamber of some incombustible mate- 
rial, and should preferably be lighted at a dis- 
tance. 

(5.) It should not give off noxious fumes or 
vapors when in use, nor should it unduly heat 
the air of the space it illumines. 

(6.) It should be reliable, or not apt to be un- 
expectedly extinguished when once lighted. 

The electric incandescent lamp is an excellent 
artificial illuminant. 

(1.) It is capable of great subdivision, and can, 
therefore, produce a uniform illumination. 

(2.) It is steady and free from sudden changes 
in its intensity. 

(3.) It compares favorably in point of economy 
with coal oil or gas, provided its extent of use is 
sufficiently great. 

(4.) It is safer than any known illuminant, 
since it can be entirely inclosed and can be 
lighted from a distance or at the burner without 
the dangerous friction match. 

The leads, however, must be carefully insu- 
lated and protected by safety fuses. (See Fuse, 
Safety. ) 

(5.) It gives off no gases, and produces far less 
heat than a gas-burner of the same candle power. 

It perplexes many people to understand why 
the incandescent electric light should not heat 
the air of a room as much as a gas light, since it 
is quite as hot as the gas light. It must be re- 
membered, however, that a gas-burner, when 
lighted, not only permits the same quantity of 



111.] 



275 



[Imp. 



gas to enter the room which would enter it if 
the gas were simply turned on and not lighted, 
but that this bulk of gas is still given off, and is, 
indeed, considerably increased by the combina- 
tion of the illuminating gas with the oxygen of the 
atmosphere ; and, moreover, this great bulk of 
gas escapes as highly heated gases. Such gases 
are entirely absent in the incandescent electric 
light, and consequently its power of heating the 
surrounding air is much less than that of gas 
lights. 

(6.) It is quite reliable, and will continue to 
burn as long as the current is supplied to it. 

Illumination, Lighthouse, Electric 

— The application of the electric arc light 
to lighthouses. 

A powerful arc light is placed in the focus of 
the dioptric lens now commonly employed in 
lighthouses. Since the consumption of the carbon 
electrodes would alter the position of the focus of 
the light, electric lamps for such purposes are 
constructed to feed both of their carbons, instead 
of the upper carbon only, as in the case of the 
ordinary arc lamp. Such lamps are called focus- 
ing lamps. 

Illumination, Unit of A standard 

of illumination proposed by Preece, equal to 
the illumination given by a standard candle 
at the distance of 12.7 inches. 

According to Preece, the illumination of the 
average streets of London, where gas is employed, 
is equal to about one-tenth of this standard in the 
neighborhood of a gas lamp, and about one- 
fiftieth in the middle space between two lamps. 

The term unit of illumination, in place of in- 
tensity of light, was proposed by Preece in order 
to avoid the very great difficulty in determining 
the intensity of a light in a street or space where 
there were a number of luminous sources, and 
where the directions of incidence of the different 
lights vary so greatly. 

A carcel standard at the distance of a metre 
will illumine a surface to the same intensity of 
illumination as a standard candle at the distance 
of 12.7 inches. (See Candle, Foot.) 

Illumined Electrode.— (See Electrode, 
Illumined?) 

Imbibition Currents. — (See Currents, Im- 
bibition.) 

linages, Electric — A term some- 



times applied to the charge produced on a 
neighboring surface by induction from a 
known charge. 

A positive charge produces, by induction, on a 
flat metallic surface near it, a negative charge 
which is distributed with varying density over the 
surface, but acts electrically as would an equal 
quantity of negative electricity placed back of the 
plate at the same distance the positive charge is 
in front of it. The correspondence of this charge 
with the image of an object seen in a plane mirror, 
has led to the term electric image. 

Maxwell defines electric image as follows: " An 
electric image is an electrified point, or system of 
points, on one side of a surface, which would pro- 
duce, on the other side of that surface, the same 
electrical action which the actual electrification of 
the surface really does produce." 

Impedance. — Generally any opposition to 
current flow. 

The sum of the ohmic resistance and the 
spurious resistance of a circuit measured in 
ohms. 

A quantity which is related to the strength 
of the impressed electromotive force of a sim- 
ple periodic or alternating current, in the same 
manner that resistance is related to the steady 
electromotive force of a continuous current. 

In the case of steady currents, the current 
strength is equal to the electromotive force dl. 
vided by the resistance ; or, 

_, ', Electromotive force 

Current strength = - 

Resistance. 

In the case of a simple periodic or alternating cur» 
rent, the average current strength is equal to the 
average impressed electromotive force divided by 
the impedance; or, 
Average current strength = 

Average impressed electromotive force 
Impedance. 

Since impedance, like true resistance of the cir- 
cuit, can be measured in ohms, it is sometimes 
called the virtual resistance. 

Impedance is a quantity equal to the square 
root of the sum of the squares of the inductive 
resistance of the circuit and the ohmic resistance. 

In the case of simple periodic or alternating 
currents, the average current strength is equal to 
the average impressed electromotive force, divided 
by the impedance ; the maximum current strength 



Imp.j 



276 



[Inc. 




is equal to the maximum impressed electromotive 
force, divided by the impedance. 

The impedance of a circuit can be repre- 
sented geometrically as fol- 
lows: Draw a right angled 
triangle (Fig. 296), the base 
of which represents the 
ohmic resistance of the cir- 

., j ,i !• i OHMIC RESISTANCE 

cuit, and the perpendicular, „. ■ . „ , . , 
. . r . Fig. 2QO. Geometrical 

the inductive resistance; Re p resenta tion of Im- 
then the hypothenuse will j>edance. 
represent the impedance. 

Since the ohmic resistance equals R, and the in- 
ductive resistance equals the inductance L, mul- 
tiplied by 2 it n, in which n, is the frequency, the 
value of the impedance is equal to 
-/R 2 +4?r 2 ns L*. 

Impedance Coil. — (See Coil, Impedance?) 

Impedance, Impulsive or Oscillatory 

The impedance which a conductor 

offers to an impulsive or oscillatory dis- 
charge. 

The impulsive impedance varies in simple pro- 
portion to the frequency of the periodic current. 
It depends on the form and size of the circuit, but 
it is independent of its resistance or permeability. 

Imponderable. — That which possesses no 

weight. 

A term formerly applied to the luminiferous 
or universal ether, but now generally aban- 
doned. 

It is very questionable whether it is possible for 
any form of matter to be actually imponderable 
or to possess no attraction for other matter. 

An imponderable fluid, as, for example, the 
universal ether, as the term is now generally em- 
ployed, is a fluid whose weight is comparatively 
small and insignificant, and not a fluid an infinite 
quantity of which would be entirely devoid of 
weight. 

Impressed Electromotive Force. — (See 
Force, Electromotive, Impressed?) 

Impulse, Electro-Magnetic An im- 
pulse produced in the ether surrounding a 
conductor by the action of an impulsive dis- 
charge, or by a pulsating field. 

Impulse, Electromotive An im- 
pulse producing an impulsive rush of elec- 
rr'city. 



The term is employed to distinguish between 
the ordinary electromotive force which produces a 
steady current of electricity and an electromotive 
impulse which produces an impulsive rush of elec- 
tricity or impulsive discharge. 

Impulsion Cell. — (See Cell, Impulsion) 

Impulsion Effect. — (See Effect, Impul- 
sion?) 

Impulsive Impedance. — (See hnpedance, 
Impulsive or Oscillatory) 

Incandesce. — To shine or glow by means 
of heat. 

Incandescence. — The shining or glowing of 
a substance, generally a solid, by reason of a 
sufficiently high temperature. 

Incandescence, Electric The shin- 
ing or glowing of a substance, generally a 
solid, by means of heat of electric origin. 

Electric incandescence of solid substances differs 
from ordinary incandescence, in the fact that un- 
less the substance is electrically homogeneous 
throughout, the temperature is not uniform in all 
parts, but is highest in those portions where the 
resistance is highest and the radiation smallest. 

The deposition of carbon in and on a carbon 
conductor by the flashing process is quite different 
as performed by electrical incandescence, than it 
would be if the carbons were heated by ordinary 
furnace or other heat. (See Carbons, Flashing 
Process for.) 

Incandescence, Thermal The shin- 
ing or glowing of a substance, generally a 
solid, by means of heat other than that of 
electric origin. 

Incandescent. — Shining or glowing with 
heat. 

Incandescent Ball Electric Lamp. — (See 
Lamp, Electric, Incandescent Ball) 

Incandescent Electric Lamp, Life Curve 

of — (See Curve, Life, of Incandescent 

Lamp?) 

Incandescent Electric Lamp, Life of 

— (See Lamp, Electric, Incandescent, Life 
of.) 

Incandescent Straight Filament Lamp. 
— (See Lamp, Incandescent, Straight Fila- 
ment?) 



Inc. J 



277 



[Ind 



Incandescing.— Glowing or shining by 
means of heat. 

Inclination, Angle of The angle 

which a magnetic needle, free to move in a 
vertical and horizontal plane, makes with a 
horizontal line passing through its point of 
support. 

The angle of magnetic dip. 

A magnetic needle, supported at its centre of 
gravity, and capable of moving freely in a ver- 
tical as well as in a horizontal plane, does not 
retain a horizontal position at all parts of the 
earth's surface. 

The angle which marks its deviation from the 
horizontal position is called the angle of dip or 
inclination, (See Dip, Magnetic.) 

Incandescent Electric Lamp. — (See 
Lamp, Electric, Incandescent.) 

Inclination Chart. — (See Chart, Inclina- 
tion.) 

Inclination Compass. — (See Compass, In- 
clination) 

Inclination, Magnetic The an- 
gular deviation from a horizontal position of 
a freely suspended magnetic needle. (See 
Dip, Magnetic. Chart, Inclination) 



(See Map or Chart, 
-(See 



Inclination Map. 

Inclination) 

Inclination of Magnetic Needle.- 

Needle, Magnetic, Inclination of) 

Inclinometer. — A name sometimes given 
to an inclination compass. (See Compass, 
Inclination) 

Incomplete Circuit. — (See Circuit, In- 
complete) 

Increased Electric Irritability.— (See 
Irritability, Electric, Increased) 

Increment Key. — (See Key, Increment) 

Increment Key of a Quadruplex Tele- 
graphic System. — (See Key, Incre7nent, of 
Quadruplex Telegraphic System.) 

India Rubber. — A resinous substance ob- 
tained from the milky juices of several tropi- 
cal trees. 

India rubber or caoutchouc is obtained from 
the Siphonia elastica of South America. 



India rubber is quite elastic and possesses high 
powers of electric insulation. When vulcanized 
or combined with sulphur, it still retains its 
powers of electric insulation in a high degree. 
In this state it is highly electrified by friction. 
(See Caoutchouc.) 

Indicating Bell. — (See Bell, Indicating) 

Indicator, Automatic Any auto- 
matic device for electrically indicating the 
number of times a circuit has been opened or 
closed, and thus the number of times a given 
operation has occurred which has caused the 
opening or closing of such circuit. 

An annunciator with an automatic drop is 
sometimes called an automatic indicator. (See 
Annunciator, Electro-Magnetic. Annunciator 
Drop, Automatic.) 

Indicator, Electric A name ap- 
plied to various devices, generally operated 
by the deflection of a magnetic needle, or the 
ringing of a bell, or both, for indicating, at 
some distant point, the condition of an electric 
circuit, the strength of current that is passing 
through it, the height of water or other liquid, 
the pressure on a boiler, the temperature, the 
speed of an engine or line of shafting, the 
working of a machine or other similar events 
or occurrences. 

A term sometimes used in place of annun- 
ciator. (See Annunciator, Electro-Magnetic) 

Indicators are of various forms. They are 
generally electro-magnetic in character. They 
are automatic in action. 

Indicator, Electric Circuit A de- 
vice, generally in the form of a vertical gal- 
vanometer, employed to indicate the presence 
and direction of a current in a circuit, and 
often to roughly measure its strength. (See 
Galvanometer, Vertical) 

Indicator, Electric, for Steamships 

— An electric indicator operated by circuits 
connected with the throttle valve and revers- 
ing gear of the steam engine. 

The signal "stop," for example, sent by the 
navigating officer to the engineer, causes him to 
close the throttle. This act places the indicator 
needle at "stop," and thus informs the officer 
that his signal has been obeyed. In the same 



Ind.] 



278 



[Lid. 



manner, the opening of the throttle sets the in- 
dicator needle to "ahead," etc. 

Indicator, Electric Throwback 

An annunciator with a drop that is electrically 
replaced. (See Annunciator, Electro-Mag- 
netic^) 

Indicator, Lamp —An apparatus 

used in the central station of a system of in- 
candescent lamp distribution to indicate the 
presence of the proper voltage or potential 
difference on the mains. 




Fig. 2QJ. Edison-Howell La7tip Indicator. 

The lamp indicator of Edison and Howell is 
shown in Fig. 297. It consists es-entially of a 
Wheatstone bridge with the resistances arranged 
as shown. A galvanometer at G, serves, by the 
movements of its magnetic needle, to act as an 
indicator. This needle remains at zero, when 
the potential difference is the exact voltage re- 
quired on the circuit with which the indicator is 
connected. The incandescent lamp at L, being 
one of the resistances, and being constantly 
traversed by the current, will have a fixed resist- 
ance for the temperature at which it is designed 
to run. The other resistances are so proportioned 
as to insure the needle at G, remaining at zero. 
If, however, the potential varies, the temperature 
of the lamp L, varies, and, being carbon, its re- 
sistance also varies, a rise of temperature cor- 
responding to a fall of lamp resistance, which 
destroys the balance of the bridge and deflects 
the galvanometer needle. The attendant then 
regulates the potential to bring the needle back to 
zero. 

Indicator, Mechanical Throwback 

— An annunciator with a mechanical drop. 
(See Annunciator, Electro-Magnetic. An- 
nunciator, Droji. Annunciator, Gravity?) 

Indicator, Pendulum — An annun- 
ciator, the indicating- arm of which is operated 



by means of a pendulum. (See An7tunciator, 
Pendulum) 

Indicator, Potential An apparatus 

for indicating the potential difference between 
any points of a circuit. 

A voltmeter is a potential indicator. It is, 
however, more than an indicator, since it gives 
the value of the potential difference in volts. (See 
Voltmeter.) A lamp indicator is a potential in- 
dicator. (See Indicator, Lamp.) 

Indicator, Semaphore An annun- 
ciator in which a gravity drop or shutter is 
caused to fall by the action of the electric 
current, thus exposing a number of other 
signals back of the drop or shutter. 

Indicator, Speed A name some- 
times applied to a tachometer. (See Tachom- 
eter) 

A form of speed indicator is shown in Fig. 
298. The endless screw drives the wheel when 
the triangular point is held firmly against the 
centre of the revolving shaft or pulley. 




Fig. 2Q8. Sped Indicator. 

Indicator, Toltaic Battery A de- 
vice for indicating the condition of a voltaic 
battery. 

Indifferent Point. — (See Point, Indif- 
ferent) 

Indirect Excitation.— (See Excitation, 
Indirect) 

Induced Atomic Currents.— (See Cur- 
rents, Induced, Ato?nic or Molecular) 

Induced Current. — (See Current, In- 
duced) 

Induced Direct Current. — (See Current, 
Direct, Induced) 

Induced Electrostatic Charge. — (See 
Charge, Induced Etectrostatic) 

Induced Molecular Currents. — (See Cur- 
rents, Induced Molecular :) 



Ind.] 



TO 



[Ind. 



Induced Reverse Currents. — (See Cur- 
rent, Reverse, Induced?) 

Inductance The induction of a 

circuit on itself, or on other circuits. 

Self-induction. 

A term now generally employed instead of 
self-induction. 

That property in virtue of which a finite 
electromotive force, acting on a circuit, does 
not immediately generate the full current due 
to its resistance, and when the electromotive 
force is withdrawn, time is required for the 
current strength to fall to zero. — {Fleming?) 

A quality by virtue of which the passage of 
an electric current is necessarily accompanied 
by the absorption of electric energy in the 
formation of a magnetic field. 

The inductance of a circuit depends: 

(i ) On the form or shape of the circuit. 

(2.) On the magnetic permeability of the space 
surrounding the circuit. 

(3. ) On the magnetic permeability of the circuit 
itself. 

tor the variations of current strength in elec- 
tric circuits, inductance is not unlike mass, or 
moment of inertia, as regards variations of velo- 
city. Time is required to produce velocity in a 
heavy body by the action of any force; so also 
time is required to produce a current by the 
action of an electromotive force. 

The electro-magnetic energy present in any 
given current is equal to the square of the current 
multiplied by the inductance. Since one of these 
factors (the current strength) represents the 
force, the other, the inductance, mu>t have the 
dimension of a distance or length. Inductance, 
therefore, is measurable in units of length. If 
the circuits are formed of magnetizable materials, 
the inductance of a circuit is the ratio between the 
total inductance taking place through the circuit 
to the current producing it. 

If the circuit is formed entirely of non-magnetic 
material, surrounded entirely by materials of 
constant magnetic permeability (such as air, in- 
sulators and diamagnetic materials generally), the 
inductance is a constant quantity and depends 
only on the form or shape of the circuit. In this 
case, the total induct ance through the circuit is pro- 
portional to the magnetizing force, and the mag- 
netic resistance, or the magnetic conductance of 
the magnetic circuit, is equal to the total induc- 



tion through the circuit, divided by the magnetiz- 
ing force. 

In cases where the magnetic circuit is partly or 
wholly of paramagnetic substances, where the 
induction bears no constant ratio to the magnetiz- 
ing force, and where the induction takes place 
partly or wholly in media of variable permeability, 
the co-efficient of self induction, or the inductance, 
must be defined in three ways: 

(1.) As the ratio between the counter electro- 
motive force in any circuit and the time rate of 
variation of the current producing it. 

(2.) As the ratio between the total induction 
through the circuit and the current producing it. 

(3.) As the energy associated with the circuit 
in the form of magnetic field, due to unit current 
in that circuit, or as the co-efficient by which half 
the square of the current must be multiplied to 
obtain the electro-kinetic energy of the circuit at 
that instant. — {Fleming. ) 

A flat sheet or strip of metal possesses less in- 
ductance than a round conductor of equal cross- 
section. 

This may be explained by conceiving that a 
flat conductor presents a greater absorption sur- 
face to the dielectric. 

Therefore, the perfect form for a conductor 
transmitting rapidly alternating currents is that 
of a flat sheet or strip of copper, or preferably a 
copper tube. 

The experiments of Hughes show that the in- 
ductance of a conductor may be regarded as an 
effect due to the time required for the rapidly 
periodic current to penetrate the conductor^ and 
that the decrease in the inductance, produced by 
forming the conductor of a strip or bar, is due 
to the decreased distance the current has to pass 
to the inner parts. 

Inductance, Absolute Unit of A 

unit of length equal to one centimetre. 

A length equal to an earth quadrant or IO 9 
centimetres is called the practical unit of induct- 
ance. The practical unit of inductance was form- 
erly called a secohm or quadrant. It is now gen- 
erally called a henry. (See Henry, A.) 

Inductance Bridge, — (See Bridge, In- 
ductance?) 

Inductance, Co-efficient of A con- 
stant quantity, such that when multiplied by 
the current strength passing in any coil or cir- 
cuit, will represent numerically the induction 
through the coil or circuit due to that current. 



Iiid. 



280 



rind. 



A term sometimes used for co-efficient of 
self-induction. (See Induction, Co-efficient 
of.) 

Inductance, Constant The induct- 
ance which occurs in circuits formed wholly 
of non-magnetic materials, immersed in cr 
surrounded by media of constant magnetic 
permeability or magnetic conductance for 
lines of magnetic force, (See Permeability, 
Magnetic?) 

When the lines of magnetic force pass through 
such materials as ordinary insulators, or diamag- 
netic materials, such as copper, the inductance is 
constant, provided the geometric form of the cir- 
cuit remains the same. 

Inductance, Formal, of Circuit 



That part of the counter electromotive force 
of a circuit which depends on the form of the 
circuit. 

Inductance, or Self-induction, Practical 

Unit of —A length equal to the earth 

quadrant or io° centimetres. 

The absolute unit of inductance is equal to I 
centimetre. 

Inductance, Oscillatory, Electric 

Inductance produced by electric oscillations. 

Inductance, Unit of A term now 

generally used for unit of self-induction. 

The value of the inductance may be given 
either in absolute or in practical units of induct- 
ance. The absolute unit of inductance is equal 
to a length of one centimetre. The practical unit 
of inductance is equal to 1,000,000,000 centi- 
metres or iC centimetres. 

The practical unit of inductance was formerly 
called a secohm. The term henry is generally 
used for this unit. (See Henry, A.) 

Inductance, Variable The induc- 
tance which occurs in circuits formed partly 
or wholly of substances like iron or other 
paramagnetic substances, the magnetic 
permeability of which varies with the inten- 
sity of the magnetic induction, and where the 
lines of force have their circuit partly or 
wholly in such material of variable magnetic 
permeability. 

Induction. — An influence exerted by a 



charged body or by a magnetic field on neigh- 
boring bodies without apparent communica- 
tion. 

A medium is necessary to connect the body 
producing the induction and that in which the 
induction is produced. (See Induction, Electro- 
static. Induction, Magnetic. Induction, Electro- 
Dynamic. ) 

Induction, Apparent Co-efficient of 

—A term sometimes used for co-efficient of 
apparent magnetic induction. (See Induc- 
tion, Magnetic, Apparent Co-efficient of.) 

It is called the apparent co -efficient of induction 
because its value is different from what it would 
be if the eddy currents were entirely suppressed. 
The eddy currents increase the resistance of the 
primary and decrease its inductance. 

Induction-Balance, Hughes' (See 

Balance, Induction, Hughes'.) 
Induction, Balance of, in Cable 

The removal of induction in a cable by 
neutralization by the presence of equal and 
opposite effects. 

A balance is obtained of the inductive effects of 
the neighboring conductors, whether in the 
bunched cable or outside of it. 

Induction-Bridge.— (See Bridge, Induc- 
tance^) 

Induction, Co-efficient of A term 

sometimes used for co-efficient of magnetic 
induction. (See Induction, Magnetic, Co- 
efficient of.) 

Induction Coil. — (See Coil, Induction) 

Induction Coil, Inverted • — (See 

Coil, Induction, Inverted. Transformer) 

Induction, Current A term some- 
times used for voltaic induction. (See Induc- 
tion, Voltaic, hiduction, Electro-Dynamic) 

Induction, Dissymmetrical, of Armature 

An induction produced by the passage 

of a different number of lines of magnetic 
force through adjoining halves of the arma- 
ture. 

Induction, Electro-Dynamic Elec- 
tromotive forces set up by induction in con- 
ductors which are either actually or practically 
moved so as to cut the lines of magnetic 
force. 



Ind.] 



231 



[Ind. 



These electromotive forces, when permitted to 
act through a circuit, produce an electric current. 

Electro-dynamic induction may be produced in 
any circuit in two ways: 

(I.) By causing expanding or contracting lines 
of magnetic force to pass through that circuit. 

(2.) By causing the circuit or conductor to pass 
through the lines of magnetic force. 

In all cases the lines of force are made to pass 
through the conductor or wire. 

There are four cases of electro- magnetic induc- 
tion: 

(i.) That in which expanding or contracting 
lines of magnetic force, produced by rapidly vary- 
ing the current in any circuit, are caused to pass 
through or cut that circuit and consequently to 
produce differences of potential therein. 

(2.) That in which expanding or contracting 
lines of magnetic force produced by any circuit by 
the rapidly varying strength of the electric 
current passing through that circuit, are caused 
to pass through another neighboring circuit and 
thus produce differences of potential therein. 

(3.) That produced by moving a conductor 
through a magnetic field so as to cut its lines of 
magnetic force. In this way the strength of the 
magnetic field may remain practically constant, 
but this strength as regards the field of the fixed 
conductor is varying, as the magnet producing 
such a field is moved toward or from such cir- 
cuit, and in this way differences of potential are 
produced in the circuit. 

(4.) That produced by moving an inducing field 
past a fixed conductor. This may I e accom- 
plished by moving an electro-magnet, an electric 
circuit, or a permanent magnet past the conductor 
in which the difference of potential is to be in- 
duced. 

There are therefore four distinct varieties of 
electro-dynamic induction: 

( 1 . ) Self-induction or inductance. (See Induct- 
ance.) 

(2.) Mutual induction, or, as it is sometimes 
called, voltaic current induction. (See Induction, 
Mutual.) 

(3.) Electro-magnetic induction, or, as it is 
sometimes called, dynamo-electric induction. 

(4.) Magneto-electric induction. 

If the terminals of a voltaic cell be connected 
with the ends of a comparatively long coil of in- 
sulated wire, no appreciable spark will be observed 
on closing the cell, because the current induced 
by self-induction is in the opposite direction to the 



current of the cell and weakens it. On breaking 
contact, however, a spark is readily observed. 
This is due to the induced current on breaking, 
which, flowing in the same direction as the cur- 
rent of the cell, strengthens it. 




Fig. 2QQ. Mutual Induction 

The coil B, Fig, 299, consists of two parallel 
coils of insulated wire, the terminals of one of 
which, called the primary coil, are connected 
with the battery cell P N, and those of the 
other, called the secondary coil, with the galva- 
nometer G. 

Under these circumstances it is found : 

(1.) That at the moment of closing the circuit 
through the primary coil, a momentary current 
is produced in the secondary coil in a direction 
opposite to that of the current through the priniary, 
as is shown by the direction of the deflection of 
the needle of the galvanometer. 

(2.) At the moment of breaking the circuit 
through the primary coil, an induced current is 
produced in the secondary coil in the same direc- 
tion as that flowing through the primary coil. 

(3.) These induced currents are momentary, 
and continue in the secondary only while the in- 
tensity of the current in the primary is varying, 
i. e., while variations are occurring in the strength 
of the magnetic field in which the secondary coil 
is placed, therefore while the expanding or con- 
tracting-lines of force are passing through the sec- 
ondary coil. 

If, for instance, when the current is established 
in the primary coil, and no current exists in the 




Fig. 300. Mutual Induction. 

secondary, the intensity of the current in the 
primary be varied by establishing a shunt circuit 
across the battery terminals, as by placing a short 
wire d, Fig. 300, in the mercury cups g, g, thus 



Ind.] 



282 



[Ind. 



decreasing the intensity of the current in the 
primary, an induced current will be set up in the 
secondary circuit in the same direction as the 
primary current. 

From all of these phenomena, we see that any 
increase of current in a conductor produces in a 
neighboring conductor an induced inverse current, 
or one in the opposite direction to the inducing 
current, while a decrease of such current produces 
a direct induced current, or one in the same 
direction as the inducing current. 

If the induction coil be made, as in Fig. 301, 
with its primary coil movable into and out of the 
secondary coil, then the following phenomena will 
occur: 

(1.) When the primary coil is moved toward 
the secondary coil an inverse current is induced 
in the secondary ; and, 

(2.) When the primary coil is moved away from 
the secondary coil a direct current is induced in 
the secondary. 

The movements of permanent magnets towards 
or from a coil will also produce an induced cur- 
rent. 

If, for example, the apparatus be arranged as 
in Fig. 302, then: 



These facts may be expressed by the following 
laws : 

(1.) Any increase in the number of lines of force 




Fig* 301. Electro-Dynamic Induction. 

(1.) A motion of the magnet towards the coil 
produces an induced current in the coil in one 
direction, and 

(2.) Its motion away from the magnet produces 
an induced current in the coil in the opposite 
direction. 

The directions of these induced currents are 
respectively inverse and direct as compared with 
the direction of the amperian currents which are 
assumed to produce the magnetic poles cf perma- 
nent magnets, or of the currents that actually 
produce electro-magnets. (See Magnetism, Am- 
pere's Theory of.) 




Fig. 302. Magneto- Electric Induction. 

which pass through a circuit produces an inverse 
current in that circuit, while any decrease in the 
number of such lines of force which pass through 
any circuit produces a direct current in that 
circuit. 



OF CURftENTJZ 
INDUCED ' 




Fig. 303 



(2.) The intensity of the induced current, or, 
more correctly, the difference of potential pro- 
duced, is proportional to the rate of increase or 
decrease of the lines of force passing through the 
circuit. 

A conductor, therefore, when moved through 



lud.J 



283 



[Ind. 



a magnetic field so as to cut the lines of magnetic 
force, will have a difference of potential generated, 
and if its circuit is closed so that the difference of 
potential can neutralize itself, it will have a cur- 
rent produced in it by induction. 

A simple but effective manner of remembering 
the direction of such currents is that proposed by 
Fleming. 

If the hand be held with the fingers extended, 
as in Fig. 303, and the direction of the forefinger 
represent the positive direction of the lines of 
force, i. e., those coming out of the N. pole of a 
magnet, then, if a wire or other conductor be 
moved in the direction in which the thumb points, 
so as to cut these lines of force at right angles, 
that is, if the conductor have its length moved 
directly across these lines, it will have an induced 
current developed m it in the direction in which 
the middle finger points. (See Force, Lines of, 
Direction of.) 

Or, the same thing can, perhaps, be even more 
readily remembered by 
cutting a piece of paper 
in the shape shown in 
Fig. 304, marking it as a £ 
shown, and then bending "£> *g 
the arm P, upward at the Jj 8 
dotted line, so as to form g 
three axes at right angles 
to one another. «,_ 

As has been already a -g 
remarked, a difference of V ? 
potential, and not a cur- "u o 
rent, is produced by mov- 
ing a conductor through 
a magne.ic field so as to 
cut its lines of force. 

It can be shown that in order to generate a dif- 
ference of potential of one volt, 100,000,000 C. G. 
S. lines of force must be cut per second. 

In electro-dynamic induction, the induced cur- 
rent is produced by the energy absorbed in moving 
the conductor through the magnetic field. Lenz 
has shown that in all cases of electro-dynamic 
induction, produced by the movement either of 
the circuit or of the magnet, the current induced 
in the circuit is in such a direction as to produce 
a magnet pole which would tend to oppose the 
motion. 

Indnction, Electro-Magnetic — — —A 

variety of electro-dynamic induction in which 
electric currents are produced by the motion 



Direction of 
Motion. 



M 



C 

Kg- 304. 



Fleming's Rule. 



of electro-magnets or electro-magnetic sole- 
noids. (See Induction, Electro-Dynamic?) 

Induction, Electrostatic The pro- 
duction of an electric charge in a conductor 
brought into an electrostatic field. 

If the insulated conductor A B, Fig. 305, be 
brought into the positive electrostatic field of the 
insulated conductor C, then, 

(1.) A charge will be produced on A and B, as 
will be indicated by the divergence of the pith 
balls. 

(2.) This charge is negative at the end A y 
nearest C, and positive at the end B, furthest 
from C, as canbeshown by an electroscope. (See 
Electroscope. ) 





Fig. 30s • Electrostatic Induction. 

(3.) The charges at A and B, are equal to each 
other ; for, if the conductor A B, be removed from 
the field of C, without touching it, the opposite: 
charges completely neutralize each other. 

(4.) If, however, the conductor A B, be touched' 
at any place by a conductor connected with the 
earth, it will lose its positive charge, and will 
remain negatively charged when removed from 
the field of C. It is in this manner that an electro- 
phones is charged. (See Electrophorus. ) 

(5.) The amount of the charges produced in the 
conductor, A B, can never be greater than that 
in the inducing body C. That is to say, the 




Fig. 30b. Induction Precedes Attraction. 

negative electricity at A, may be sufficient in 
amount to neutralize the positive charge on C, if 
allowed to do so. In point of fact the charge in- 



Ind.] 



284 



[Ind. 



duced is less in amount than the inducing charge, 
according to the distance between C and A, and 
the nature and condition of the medium which 
separates them, 

The attractions of light bodies by charged sur- 
faces are due to the opposite charge produced on 
those parts of th; light bodies that are nearest the 
charged body 

The pith ball B, Fig. 306, suspended by a silk 
thread between an insulated positively charged 
conductor A, and the uninsulated conductor C, 
will receive by induction a negative charge on 
the side nearest A, and a positive charge on the 
side nearest C. It is therefore attracted to A, 
where, receiving a positive cnarge, it is repelled to 
C, where it is discharged and again assumes a 
vertical position. Induction again occurs, and 
consequent attraction and repulsion. These 
movements follow one another so long as a suffi- 
cient charge remains in A. 

Induction, Faradic, Apparatus 

(See Apparatus, Faradic Induction?) 



Induction, Magnetic 



-The produc- 



-(See Fi7ider, Induc- 



Induction-Finder. 

tion.) 

Induction, Lateral An induction 

observed between closely approached portions 
of a circuit through which an impulsive dis- 
charge, such as the disruptive discharge of a 
Leyden jar, is passed as a long spark, thereby 
making the resistance of the circuit high. 

A long copper wire, bent in the form of a rec- 
tangle, has its free ends near their extremities 
bent so as to approach within half an inch of each 
other. One of the ends of the wire is provided 
with a metallic ball and the other end connected 
with the earth. If, now, a Leyden jar charge is 
passed through the wire by connecting the outer 
coating with the end of the earth-connected wire 
and holding the inside coating near the knob, a 
spark will pass through the half inch of space be- 
tween the approached portions of the circuit. 

This discharge is due to what was formerly 
called lateral induction. The discharge of a 
Leyden jar is an oscillatory discharge, and it 
passes through the intervening air space instead 
of through the conductor because the resistance 
' of the latter to the rapid alternations produces a 
counter electromotive force which acts as a re- 
sistance whose value is greater than that of the 
airspace itself. (See Path, Alternative.) 



tion of magnetism in a magnetizable substance 
by bringing it into a magnetic field. 

Suppose a small portion of a magnetizable body 
is placed in a magnetic field produced in a gap 
separating two closely approximated poles. To 
simplify matters, suppose this small portion to be 
a free unit pole. It will be acted on by two 
forces: 

(1.) The force due to the magnetic field. 

(2.) The force dae to the free magnetism, 
which appears at the surface of the gap or cut. 

The force on the unit pole is compounded of 
these two separate forces, and is called the magnetic 
induction of the space. Magnetic induction is, 
therefore, strictly speaking, a quantity. 

The direction of magnetic force and the mag- 
netic induction are the same in an air space out- 
side a magnet. Within a bar of iron or other 
paramagnetic material, under induction in a mag- 
netic field, the magnetic force at any point is due 
not only to the external or original field, but also 
to the field produced by the polarity induced, 
which acts opposed to the magnetic force at 
points. Magnetic force and magnetic induction 
are identical only where there is no magnetism. — 
(Fleming.) 

When a magnetizable body is brought into a 
magnetic field the following phenomena occur, 
viz.: 

( 1 . ) The lines of magnetic force pass through 
the body and are condensed upon it. (See Fietd, 
Magnetic. Paramagtietic. ) 

(2.) If the body is free to move around an axis, 
but is not free to move bodily towards the magnet 
pole, i\ will come to rest with its greatest extent 
or length in the direction ol the lines of force; 
i. <?., in the direction in which it will offer the 
least resistance to the lines of force that thread 
through it. 

(3.) The body will therefore become a magnet, 
its south pole being situated where the lines of 
force enter it and its north pole where they pass 
out from it. Since the lines of magnetic force 
are assumed to come out of the north pole of a 
magnet and to enter its south pole, if a magnet- 
izable substance is brought near a north pole, 
the lines of force from that north pole will enter 
it at those parts nearest such north pole, thereby 
rendering such points south, and will pass out of 
its further end, which will thereby become north. 

(4.) The intensity of the induced magnetism 



Iiid.] 



285 



[Lid. 



"will depend on the number of lines of force that 
pass through it. 

(5.) The direction of the axis of magnetization 
will depend on the directions in which the lines 
of force thread through the body. (See Axis, 
Magnetic.) 




N S" N' 

Fig- 307. Magnetic Induction. 

If a bar of iron, N' S' ,Fig. 307, be brought near 
the magnetized bar, N S, poles will be produced 
in it by induction, as may be shown by throwing 
iron filings on it. 

The nearer thebody to be magnetized is brought 
to the magnetizing pole the greater will be the 
number of lines of force that thread through it. 
Consequently, the intensity of the induced mag- 
netism will be greater ; this will be greatest when 
the bodies actually touch each other. 

The production of magnetism, therefore, by 
contact or touch is only a special case of the pro- 
duction of magnetization by induction. 

The attraction of a magnetizable body by a 
magnet pole is caused by the mutual attraction 
which exists between the pole produced by induc- 
tion and the pole producing the induction. This, 
it will be seen, is similar to the attraction caused 
by an electric charge. 

The following terms are given by Fleming as 
employed in the same sense as magnetic induc- 
tion of an area: 

(i.) The number of unit tubes of induction 
passing through the area. 

(2.) The number of lines of force (induction) 
passing through the area., —(fraraday.) 

(3.) The total magnetic induction through the 
area. — {Maxwell. ) 

(4.) The flux or flow of magnetic induction 
through an area. — [Mascart &= Joubert.) 

(5.) The surface-integral of magnetic induction 
over an area. — {Fleming.) 

Induction, Magnetic, Apparent Co-effi- 
cient of The co-efficient of induction 

as influenced by the presence of eddy cur- 
rents. 

This is called the co-efficient of apparent in- 
duction, because its value is not the same as it 
would be if the eddy currents were entirely sup- 
pressed. 



The value of the co-efficient of apparent induc- 
tion depends on the amount of the retardation of 
the magnetism; or, what is the same thing, on 
the strength of the eddy currents. 

Induction, Magnetic, Co-efficient of 

— A term sometimes used instead of magnetic 
permeability. (See Permeability, Magnetic?) 

The ratio existing between the number of 
lines of magnetic induction that pass through 
any area of cross-section of a magnetic cir- 
cuit and the magnetizing force producing 
such induction. 

If B, equals the magnetic induction, or the num- 
ber of lines of force that pass through any area of 
cross-section, and H, equals the magnetizing force, 
and ju, equals the permeability, or the co-efficient 
of magnetic induction; then, 
B 



M = 



II 



Induction, Magnetic, Dynamic 



The induction which takes place in the field 
of a magnet whose field is moving as regards 
the body in which induction is occurring. 

This movement of the field may be attained, 

(1.) By the movement of the magnet. 

(2.) By the movement of the body in which 
induction is taking place. 

(3.) By the expansion or contraction of the lines 
of magnetic force produced by variations of the 
strength of the magnetic field ; or, in other words, 
by the movement of the field. (See Induction, 
Electro- Dynamic. ) 

Induction, Mag netic, Flux or Flow of 

A term employed in the same sense 

as the magnetic induction which takes place 
through any given area. 

The flux or flow of magnetic induction is equal 
to the magnitude of the area multiplied by the 
normal induction which takes place in one unit 
of that area. 

Induction, Magnetic, Lines of 

Lines which show not only the direction in 
which magnetic induction takes place, but 
also the magnitude of the induction. 

A line of induction may be regarded as a line 
along which induction takes place, or as the axis 
of a tube of induction. 

This term is often loosely used for lines of force. 

Induction, Magnetic, Static The 



Ind.] 



286 



[Ind. 



induction which takes place in the field of a 
magnet whose field is stationary as regards 
the body in which induction is occurring. 

The term static magnetic induction is used in 
contradistinction to dynamic magnetic induction 
which occurs in a moving field. (See Induction, 
Electro- Dynamic. ) 

Induction, Magnetic, Surface-Integral 

of A term employed in the same sense 

as the magnetic induction which takes place 
over a given area. 
Induction, Magneto - Electric A 

variety of electro-dynamic induction in which 
electric currents are produced by the motion 
of permanent magnets, or of conductors past 
permanent magnets. (See Induction, Elec- 
tro-Dynamic) 

Induction, Mutual Induction pro- 
duced by two neighboring circuits on each 
other by the mutual interaction of their mag- 
netic fields. (See Induction, Electro-Dy- 
namic. Currents, Extra) 

Induction produced in neighboring charged 
conductors by the mutual interaction of their 
electrostatic fields. (See Field, Electro- 
static) 

The mutual induction of two conductors or cir- 
cuits, is equal to the ratio of the induction which 
takes place through one of the circuits, to the 
strength of current in the other circuit, which is 
producing the induction 

Induction, Mutual, Co-efficient of 

The quantity which represents the number 
of lines of force which are common to or 
linked in with two circuits, which are pro- 
ducing mutual induction on each other. 

The maximum value the co-efficien£ of mutual 
induction can have, is equal to the square root of 
the product of the inductance of the two circuits, 
cr t/L X N, in which L and N, are the constant 
co-efficients of self-induction of the two circuits. 

Induction, Mutual, Loops of Loops 

or lines of induction produced in any circuit 
by variations in the intensity of the current 
flowing in a neighboring circuit. 

The lines of induction produced by a circuit, in 
which a current of electricity is flowing, are 
closed loops or circles surrounding the circuit 
once or more. The wire or circuit is formed by 



coiling a conductor a number of times in a cir- 
cular coil, and this circular coil is placed near 
another coil in which a varying current is flowing. 
As the lines of induction grow or increase,, 
they cut the circular coil, forming lines of induc- 
tion in the shape of loops, a number of which pass 
around it„ They are called loops of mutual in- 
duction. 

Induction, Open-Circuit The in- 
duction produced in an open circuit by means 
of electric pulses in neighboring circuits. 

The researches of Hertz have shown that when 
an impulsive discharge, or an oscillatory dis- 
charge, occurs, an induction occurs even in open 
circuited conductors. He shows that these induc- 
tive effects are due to electro-magnetic waves or 
oscillations set up in the surrounding ether, 
which are propagated through free ether with the 
velocity of light. When these electro-magnetic 
waves or radiations impinge on any circuit, if its 
dimensions be such that sympathetic vibrations 
can be excited therein, such vibrations are set up 
and cause similar phenomena to those of the ex- 
citing cause, viz., oscillatory discharges or elec- 
tro-magnetic vibrations. Hertz calls these sym- 
pathetic circuits, resonators, from their resem- 
blance to acoustic resonators. (See Resonators, 
Electric.) 

Induction, Oscillatory A name 

sometimes applied to open-circuit induction, 
(See Induction, Open-Circuit) 

Induction, Reflection of A term 

proposed by Fleming to express an action 
which resembles a reflection of inductive 
power. 

The coils A and B, Fig. 308, are arranged as 




Fig. 308. Reflection of Induction. 

shown, so as to act as the primary and secondary 
respectively of an induction coil, and are placed 



lad.] 



287 



[Ind, 



conjugate or perpendicular to each other. (See 
Coils, Conjugate.) Therefore, no sounds are 
heard in the telephone T, when the current is 
rapidly reversed. If, however, a plate of copper, 
C, is placed in the position shown, then sounds 
are heard in the telephone. The action here 
resembles a reflection of the inductive action from 
A to B, by means of the plate C. The explana- 
tion is, of course, simple. Though A, can exert 
no action on B, because the two coils are conju- 
gate to each other, yet A, can produce secondary 
currents i.i C; and these reacting on B, produce 
tertiary currents in C, and, therefore, sounds in 
the telephone. 



Induction, Self 



-Induction produced 



in a circuit at the moment of starting or stop- 
ping the currents therein by the induction of 
the current on itself. (See Currents, Extra.) 
A coil having unit self-induction, is sometimes 
said to have one tube of induction, or line of force 
added to its field for each increase of one unit of 
current. 

Induction, Self, Absolute Unit of 

A term sometimes employed for absolute unit 
of inductance. (See hiductance, Absolute 
Unit of.) 

Induction, Self, Ayrton & Perry's 

■Standard of A standard for the com- 
parison of values of self-induction. 

The standard of self-induction of Ayrton & 
Perry consists of three bobbins of wire, two fixed 
and one movable. The movable bobbin is so ar- 
ranged as to be capable of motion through 180 
degrees within the fixed bobbins. The coils are 
wound on the surface of the zone of a sphere. 

This apparatus permits of the ready compari- 
son of the self-induction in different circuits, or in 
the same circuit under different conditions. 

Induction, Self, Co-efficient of — 

The number of lines of force the current would 
induce or enclose in itself when the current 
flowing through it is equal to one absolute 
unit. 

A term sometimes employed in the sense 
of inductance of a circuit. 

The co-efficient of self-induction is defined by 
Fleming as follows : "In the case of circuits con- 
veying electric currents, which are wholly made 
of non-magnetic material, and wholly immersed 



in a medium of constant magnetic permeability, 
the total induction through the circuit per unit of 
current flowing in that circuit, when removed 
from the neighborhood of all other magnets and 
circuits, is called the co-efficient of self-iaduction; 
otherwise the ratio of the numerical values of the 
electro-magnetic momentum of such circuit, and 
the current flowing in it, when totally removed 
from all other currents and magnets, is the nu- 
merical value of the inductance of the circuit." 

Since the magnetic lines due to a current in a 
circuit thread through the convolutions of the cir- 
cuit itself, any variation in the current induces 
a difference of potential in the circuit itself, since 
the lines of force produced by the current in the 
circuit pass through or cut the circuit. 

The ratio between this self-induced electromo- 
tive force, and the rate of change in the current 
which causes it, is called the co-efficient of self- 
induction.- (S. P. Thompson.) 

For a given coil the co-efficient of self-induction 
is, according to S. P. Thompson : 

(i.) Proportional to the square of the number 
of convolutions. 

(2.) Is increased by the use of an iron core, 

(3.) If the magnetic permeability is assumed as 
constant, the co-efficient of self-induction is nu- 
merically equal to the product of the number of 
lines of magnetic force due to the current, and 
the number of times they are enclosed by the 
circuit. 

Induction, Self, Magnetic A re- 
tardation in the appearance of magnetization, 
after the application of the magnetizing force, 
due to the influence of the magnetic lag. 

Magnetic retardation. 

This retardation in the magnetization has re- 
ceived the name of magnetic self-induction or re- 
tardation because it corresponds to the retarda- 
tion in the starting or stopping of a current, in a 
conducting circuit, due to the self-induction of the 
current. 

Induction, Self, Unit of The unit 

of inductance. (See Inducta?ice, Unit of.) 

The unit of se'.f-induction is now generally 
called the unit of inductance. 

Induction, Symmetrical, of Armature 

An induction produced by the simul- 
taneous passage of the same number of lines 
of magnetic force through adjoining halves of 
the armature. 



Ind.] 



288 



[IttJ. 



Induction Telegraphy, Current Induc- 
tion System of ■ — (See Telegraphy, In- 
duction, Current Induction System of.) 

Induction Telegraphy, Static Induction 
System of ■ — (See Telegraphy, Induc- 
tion, Static Induction Syste?n of.) 

Induction Top. — (See Top, Induction?) 

Induction, Total Magnetic —The 

total magnetic induction of any space is the 
number of lines of magnetic induction which 
pass through that space, where the magnetiz- 
able material is placed, together with the lines 
added by the magnetization of the magnetic 
material. 



magnetic field as to continuously cut its lines 
of force. 
If the conducting wire, ABC, Fig. 309, be ro» 



Induction, Tubes of 



-A portion of 



a magnetic field containing a number of 
closely contiguous lines of induction termi- 
nated by equipotential surfaces, or surfaces 
perpendicular to the lines of induction. 

Tubes of induction possess the following char- 
acteristics : 

(I.) The product of a normal cross-section of a 
tube and the mean magnetic induction which 
takes place over that section is the same for all 
tross-sections of the tube. In other words, the 
flux or flow of induction is constant throughout 
the entire length of the tube. 

(2.) The normal cross-section of any equipoten- 
tial surface at any point of a tube of induction is 
inversely proportional to the magnetic induction 
at that point. 

(3.) All tubes f f induction form endless tubes. 
This is necessary, since all lines of induction form 
closed circuits. 

(4.) All tubes of induction may be expressed 
by a single line of induction, which, in the case of 
a uniform field, occupies the centre of the tube. 
(See Force, Tubes of.) 

Induction, Toltaic A variety of 

electro-dynamic induction produced by cir- 
cuits on themselves or on neighboring circuits. 

Mutual induction. (See Induction, Elec- 
tro-Dynamic.) 

This kind of induction is usually called current 
induction. 

Induction, Unipolar A term some- 
times applied to the induction that occurs 
when a conductor is so moved through a 




Fig- 30(). Unipolar Induction. 
tated (in a direction toward the observer) around 
the pole N, of a magnet, it will continuously cut 
its lines of magnetic force in practically the same 
direction, and will therefore produce a difference 
of potential that will result in a continuous cur- 
rent in the direction of the arrows. The end A, 
is supported in a recess in N, while the end near 
C, slides on a projection on the middle of the 
magnet. 

Unipolar induction occurs in the case of Stur- 
geon's wheel, in which a metallic disc mounted 
on an axis is rotated between the poles of a mag- 
net so as to cut the lines of magnetic force. In 
this case a difference of potential is generated 
which will produce a current that flows from the 
axis to the periphery, provided contact points are 
placed on the axis of rotation and the periphery 
of the disc connecting these parts of the disc in a 
closed circuit. 

Unipolar dynamos operate by the continuous 
cutting of lines of magnetic force. 

Strictly speaking, there is no such thing as a 
unipolar dynamo or unipolar induction, since a. 
single magnetic pole cannot exist by itself. Con- 
tinuous cutting of lines of magnetic force, how- 
ever, can exist, and produces, unlike the ordinary 
bipolar induction, a continuous current without 
the use of a commutator. 

Inductionless Resistance. — (See Resist- 
ance, Inductionless.) 

Inductive Capacity, Specific (See 

Capacity, Specific Inductive.) 

Inductive Circuit. — (See Circuit, Induc- 
tive.) 



[nd. 



289 



[Ine. 



Inductive Electromotive Force.— (See 

Force, Electro?notive, Inductive?) 

Inductive Retardation.— (See Retarda- 
tion, Inductive.) 

Inductive Resistance. — (See Resistance, 
Inductive.) 

Inductivity, Specific Magnetic ■ 

A term sometimes employed for specific mag- 
netic conductivity. (See Conductivity, Spe- 
cific Magnetic.) 

Inductometer, Differential — An 

apparatus for measuring, by means of a gal- 
vanometer, the momentary currents produced 
by the discharge of a cable. 

Currents produced by the discharge of a cable 
are of so short a duration that they do not pro- 
duce much more than a momentary effect on a 
galvanometer needle. 

The inductive charge in a cable, or the quan- 
tity of electricity produced in it by induction, is: 

(i.) Directiyas the electromotive force of the 
charging battery ; 

(2.) Inversely as the square root of the thick- 
ness of the coating of gutta-percha or other insu- 
lating material between the conducting wires and 
the metallic sheathing ; 

(3.) Directly as the square root of the diameter 
of the copper wire of the conductor; and 

(4.) Dependent on the specific inductive capa- 
city of the insulating material employed in the 
cable. 

In order to cause the cable discharge to more 
thoroughly affect the galvanometer needle, Mr. 
Latimer Clark employed a differential instrument 
with a large battery and three reversing keys, by 
means of which he gave a rapid succession of 
charges to the cable. He called the instrument a 
Differential Inductometer. 

Inductophone.— A device, suggested by 
Mr. Willoughby Smith, for obtaining electric 
communication between moving trains and 
fixed stations by means of the currents devel- 
oped by induction in a spiral of wire fixed on 
the moving engine, by its motion past spirals 
on the line, into which intermittent currents 
are passed. 

The spiral on the engine is placed in the circuit 
of a telephone. (See Telezrabh . / ductive.) 



Inductor Dynamo. — (See Dynamo, Induc- 
tor.) 

Inductorium. — A name sometimes applied 
to a Ruhmkorff induction coil. (See Coil, 
Induction.) 

Inequality, Annual, of Earth's Magnetic 

Variation or Inclination Annual 

variations in the value of the magnetic varia- 
tion or inclination at any place. (See Varia- 
tion, Magnetic. Inclination, Magnetic.) 

Inequality, Annual, of Earth's Magnet- 
ism Variations in the value of the 

earth's magnetism during the earth's revolu- 
tion depending on the position of the sun. 

Annual variations in the earth's magnetism* 
(See Variations, Magnetic, Annual.) 

Inequality, Diurnal, of Earth's Magnetic 

Variation or Inclination Diurnal 

variations in the value of the earth's magnetic 
variation or inclination. (See Variation, 
Magnetic. Inclination, Magnetic?) 

Inequality, Diurnal, of Earth's Magnet- 
ism ■■ Inequalities or variations in the 

value of the earth's magnetism, dependent on 
the position of the sun during the earth's 
rotation. 

Inequality, Lunar, of Earth's Magnetic 
Variation or Inclination Small va- 
riations in the value of the magnetic variation 
or inclination, dependent on the position of 
the moon as regards the magnetic meridian. 

Inequality, Lunar, of Earth's Magnet- 
ism Small variations in the value of 

the earth's magnetism dependent on the po- 
sition of the moon as regards the magnetic 
meridian. 

Inertia. — The inability of a body to change 
its condition of rest or motion, unless some 
force acts on it. 

The inertia of matter is expressed in Newton's 
first law of motion, as follows : 

"Every body tends to preserve its state of rest 
or of uniform motion in a straight line, except ia 
so far as it is acted on by an impressed force. ' ' 

All matter possesses inertia. 

Inertia, Electric A term some- 
times employed instead of electro-magnetic 
inertia. (See Inertia, Electro-Magnetic.) 



Ine.] 



290 



[Iiis. 



A term employed to indbate the tendency 
of a current to resist its stopping or starting. 

By self-induction an electromotive force is pro- 
duced in a wire or other conductor at the moment 
of starting the current in it that tends to oppose 
the starting of such current, and also an electro- 
motive force at the moment of stopping the cur- 
rent, in such a direction as to prolong or continue 
the current. In other words, self-induction tends 
to retard the rise or fall of the current. 

Fleming traces the following comparison be- 
tween the moment of inertia of a rotating wheel 
and the energy of its rotation on the one side, and 
the inductance of a circuit and the electro-mag- 
netic energy of the circuit on the other. 

(i.) The angular momentum of a fly-wheel is 
equal to the numerical product of its moment of 
inertia and the angular velocity of the wheel. 
Similarly the electro-magnetic momentum is equal 
to the product of the inductance of the circuit by 
the current flowing through it at any instant. 

(2.) The rate of change of the angular mo- 
mentum of the wheel, at any instant, is a measure 
of the rotational force of the couple acting at that 
instant. 

Similarly the rate of change of the electro-mag- 
netic momentum of the circuit is the measure of 
the electromotive force acting on it so far as 
mere change of current is concerned, and irre- 
spective of that part cf the electromotive force re- 
quired to overcome the ohmic resistance. 

An electric current does not start or stop in- 
stantaneously. It requires time to do either, just 
as a stream of water or other fluid does, and it is 
this property which is referred to by the term 
electric inertia. Inertia does not appear to be 
possessed by electricity apart from matter. " It 
is doubtful," says Lodge, "whether electricity 
of itself, and disconnected from matter, has any 
inertia." 

Inertia, Electro-Magnetic A term 

sometimes employed instead of inductance, 
or the self-induction of a current. (See In- 
ductance. Inertia, Electric?) 

Inertia, Electro-Magnetic, Co-efficient of 

A term sometimes employed in place 

of the co-efficient of inductance or self-induct- 
ance of a circuit* 

Inertia, Magnetic The inability of 

a magnetic core to instantly lose or acquire 
magnetism. 



A magnet core tends to continue in the mag. 
netic state in which it was placed. 

The magnetic inertia is sometimes called the 
magnetic lag. 

To decrease the magnetic inertia, the strength 
of the magnetizing current is increased and the 
length of the iron core decreased. The iron 
should also be quite soft. (See Lag, Magnetic. 
Force, Coercive.) 

Inferred Zero.— (See Zero, Inferred.) 

Infinity Plug.— (See Plug, Infinity.) 

Influence. — A term sometimes used instead 
of electrostatic induction. (See Induction, 
Electrostatic) 

The word influence is used by some to apply 
to the case of electrostatic induction, as distin- 
guished from electro-magnetic or magnetic induc- 
tion. 

Influence Charge. — (See Charge, Influ- 
ence.) 

Influence Machine. — (See Machine, In- 
fluence) 

Inker, Morse —A form of tele- 
graphic ink-writer. (See Ink- Writer, Tele- 
graphic) 

Ink- Writer, Telegraphic A device 

employed for recording the dots and dashes 
of a telegraphic message in ink on a fillet or 
strip of paper. 

A telegraphic ink-writer is a form of telegraphic 
recorder. (See Recorder, Morse. ) 

Inside Wiring. — (See Wiring, Inside) 

Insolation, Electric A term some- 
times employed for electric sunstroke, or 
electric prostration. (See Sunstroke, Elec- 
tric. Prostration, Electric) 

Installation. — A term embracing the 
entire plant and its accessories required to 
perform any specified work. 

The act of placing, arranging or erecting 
a plant or apparatus. 

Installation, Electric The estab- 
lishment of any electric plant. 

An electric light installation, for example, in- 
cludes the steam engine and boilers, or other 
prime movers, the dynamo-electric machines, the 
line wires or leads, and the lamps. 

Insulated Body. — (See Body, Insulated) 



Ins.] 



291 



fins. 



Insulating- Cements. — (See Cements, In- 
sulating^) 

Insulating Sleeve. — (See Sleeve, Insula- 
ting.) 

Insulating Stool. — (See Stool, Insula- 
ting.) 

Insulating Tape. — (See Tape, Insula- 
ting.) 

' Insulating Tube. — (See Tube, Insula- 
ting.) 

Insulating Tarnish. — (See Varnish, Elec- 
tric.) 

Insulation, Electric Non-conduct- 
ing material so placed with respect to a con- 
ductor as to prevent the loss of a charge, or 
the leakage of a current. 

In the case of coils the character of the insula- 
tion of the coil of wires through which the cur- 
rent is to pass must be considered from the stand- 
point of the cooling of the coil by radiation. 

In considering the safest and most economical 
current density to employ in any dynamo or 
motor, the depth of the coil, i. e., the thickness of 
its coils, must be considered, as well as the char- 
acter of the materials employed for the insulation. 
Such substances as silk or wool, which are char- 
acterized by low heat conduction, retain the heat 
longer than cotton. Hence the depth of a silk 
covered coil should necessarily be less than that of 
one covered with cotton. 

Insulation Joint. — (See Joint, Insula- 
tion.) 

Insulation, Porous An insulating 

material containing air or gas placed between 
the conductor and the insulating covering. 

A strip of perforated paper is used for cover- 
ing the bare conductor, and the insulating ma- 
terial is placed on the outside of this ; or, a cord 
is wrapped separately around the conductor, and 
the insulating material is placed on the outside of 
this. By these means, as will be seen, a layer of 
air exists between the conductor and its insulating 
covering. 

Insulation Resistance. — (See Resistance, 
Insulation^) 

Insulation, Static ■ — A term em- 
ployed in electro-therapeutics for a method 
of treatment by convection streams or dis- 



charges, in which the patient is seated on an 
insulated stool connected to one pole or 
electrode of an influence machine, while the 
other pole or electrode is connected to the 
ground. 

Insulator Cap. — (See Cap, Insulator.) 

Insulator, Dice-Box A name some- 
times applied to a double-cone insulator. (See 
Insulator, Double-Cone.) 

Insulator, Double-Cone An insu- 
lator in which the line wire passes through and 
is supported by means of a tube consisting of 
two inverted cones joined at their smaller 
bases. 

Insulator, Double-Cup An insula- 
tor consisting of two funnel-shaped cups, 
placed in an inverted position on the sup- 
porting pin and insulated from one another 
by a free air space, except near the ends, 
which are cemented. 

The wire is wrapped in a groove on the outside 
of the outer cup. This possesses the advantage 
of exposing it to the rain, which thus cleanses the 
insulator and improves its power of insulation. 
The inner cup is supported on a pin and the outer 
cup cemented to it. Any leakage must, there- 
fore, pass over the entire surface of both cups. 

Insulator, Double-Shackle A form 

of insulator used in shackling a wire, consist- 
ing of two single-shackle insulators. 

Insulator, Double-Shed A double- 
cup insulator. (See Insulator, Double-Cup.) 

Insulator, Fluid An insulator pro- 
vided with a small, internally placed, annular, 
cup-shaped space, filled with an insulating 
oil, thus increasing the insulating power of the 
support. 

The line wire is wrapped in a groove on the 
outside of the insulator. Any surface leakage 
between the wire and ground in wet weather 
must occur between the outer surface of the insu- 
lator, which is kept cleansed by the rain, and the 
inner surface, where it is supported by the pin, 
But to do this, the current must cross the oil in 
the cup, which, from its high power of insulation, 
effectually prevents leakage. 

Insulator, Invert — An insulator 



Ins.] 



293 



[Int, 



placed on the top of the wire instead of under- 
neath it, as was formerly done. 

Insulator, Oil —A fluid insulator 

filled with oil. (See Insulator, Fluid.) 

Insulator Pins.— (See Pins, Insulator?) 

Insulator, Single-Shackle A form 

of insulator used for shackling a wire. (See 
Shackling a Wire?) 

Insulator, Single-Shed An insula- 
tor with a single inverted cup. 

The wire is wrapped around a groove on the 
outside of the cup, where it is exposed to the 
cleansing action of the rain. The cup is inverted 
and supported on a pin, to which it is screwed and 
cemented. 

Insulator, Telegraphic or Telephonic 
A non-conducting support of tele- 
graphic, telephonic, electric light or other 
wires. 

Insulators are generally made of glass, earthen. 





Fig. 310. Glass 
Insulator. 



Fig. 311. Porcelain 

Insulator. 



ware, porcelain or hard rubber, and assume a 
variety of forms, some of which are shown in Figs. 
310, 311 and 312. Of whatever material they are 
made, it is necessary that the 
surface on which the wire rests, 
or around which it is wrapped, 
should be smooth, so as to avoid 
abrasion, either of its insulat 
ing covering or of the wire it- 
self. 

Two things are to be con 
sidered in the selection of an 
insulator, viz.: 

(1.) The insulating power of 
the material of which the in- 
sulator is composed, so as to 
reduce the leakage as much as 
possible. (See Leakage, Electric.) 

(2.) The tensile strength of the material, so 




Fig. 3 1 2. Hard 
Rubber Insulator. 



that in case of heavy wires no breaks may result 
from the fracture of the insulator. 

Some forms of insulators are shown in Figs. 
310, 311 and 312. They are screwed to the pins 
by the threads shown. The insulating materials 
of which they are formed are of glass, porcelain 
and hard rubber respectively. 

Insulator, Window-Tube A tube 

of vulcanite or other insulating material pro- 
vided for the insulation of a wire entering a 
room. 

The wire conductor passes through the middle 
of the tube, which is firmly fixed in an opening 
passing through the window frame. 

Insulator, Z — A form of double-cup 

insulator in which the insulating material, 
earthenware or porcelain, is made in a single 
piece, instead of in two separate pieces. 

The body of the insulator is conical in form, 
and the interior air space presents a shape ap- 
proximately that of the letter Z. 

The double form is used in order to diminish 
the leakage. 

Intensity Armature. — (See Armature, 
Intensity?) 

Intensity, Connection of Yoltaic Cells for 

• A term formerly employed for series- 
connected voltaic battery cells. (Obsolete.) 

Intensity, Magnetic — Density of 

magnetic induction. 

Magnetic flux per square centimetre. 

A committee of the American Institute of Elec- 
trical Engineers on "Units and Standards," pro- 
poses the following definition for magnetic inten- 
sity: 

The induction density at a point within an ele- 
ment of surface is the surface differential at that 
point. 

The practical unit of magnetic intensity is 
io 8 or 100,000,000 C. G. S. lines per square cen- 
timetre. 

In practice, excluding the earth's field, intensi- 
ties range from 100 to 20,000 C. G. S. lines per 
square centimetre, and the working unit should, 
perhaps, have the prefix milli or micro. 

Intensity, Magnetic, Pole of The 

earth's magnetic poles as determined by 
means of the oscillations of a magnetic 
needle. 



Illte] 



293 



[Ion. 



The points ot the earth's greatest magnetic 
intensity. 

Intensity of Current.— (See Current, In- 
tensity of) 

Intensity of Field.— (See Field, Inten- 
sity of) 

Intensity of Light.— (See Light, Inten- 
sity of.) 

Intensity of Magnetization.— (See Mag- 
netization, Intensity of.) 
Intensity, Photometric, Unit of 

The amount of light produced by a candle 
that consumes two grains of snermaceti wax 
per minute. (See Candle.) 

Inter Air Space.— (See Space, Inter Air.) 

Intercrossing". — In a system of telephonic 
communication, a device for avoiding the dis- 
turbing effects of induction by alternately 
crossing equal sections of the line. (See 
Connection, Telephonic Cross.) 

Interference of Electro-Magnetic 
Waves. — (See Waves, Electro-Magnetic, 
Interference of) 

Interlocking Apparatus.— (See Appa- 
ratus Interlocking) 

Intermittent Contact. — (See Contact, In- 
termittent) 

Intermittent Cross.— A form of electric 
cross. (See Cross, Electric) 

Intermittent Current. — (See Current, In- 
termittent) 

Intermittent Disconnection. — (See Dis- 
connection, Intermittent ) 

Intermittent Earth.— (See Earth, Inter- 
mittent) 

Internal Circuit. — (See Circuit, In- 
ternal) 

Internal Polarization of Moist Bodies.— 
(See Polarization, Internal, of Moist 
Bodies) 

Interrupter. — Any device for interrupting 
or breaking a circuit. 

Interrupter, Automatic An auto- 
matic contact breaker, (See Make-and- 
Break. Automatic.) 



Interrupter, Reed A term some- 
times applied to a tuning-fork interrupter. 
(See Interrupter, Tuning-Fork) 

Interrupter, Tuning-Fork An in* 

terrupter in which the successive makes and 
breaks are produced by the vibrations of a 
tuning-fork or reed. 

The tuning-fork or reed is maintained in vibra- 
tion by any suitable means. Such interrupters 
are applied to various uses. Synchronous mul- 
tiplex telegraphy affords an example of such uses. 

Invariable Calibration of Galvanometer. 

— (See Calibration, Invariable, of Galva- 
nometer) 

Inverse Electromotive Force. — (See Force, 
Electromotive, Inverse) 

Inverse or Make-Induced Current. — (See 
Current, Make-Induced) 

Inverse Secondary Current.— (See Cur- 
rent, Inverse Secondary) 

Inversion, Thermo-Electric An 

inversion of the thermo-electric electromotive 
force of a couple at certain temperatures. 
(See Diagram, Thermo-Electric ) 

Invert Insulator. — (See Insulator, Di- 
vert) 

Inverted Induction Coil. — (See Coil, 
Induction, Inverted) 

Inverted Type of Dynamo, — (See Dy- 
namo, Inverted) 

Invisible Electric Floor Matting. — (See 
Matting, Invisible Electric Floor) 

Ions. — Groups of atoms or radicals which 
result from the electrolytic decomposition of 
a. molecule. 

The ions are respectively electro-positive and 
electro-negative. The electro-positive ion ap- 
pears at the plate connected with the electro- 
negative terminal, or at the kathode, and is called 
the kaihion* 

The electro -negative ion appears at the plate 
connected with the electro-positive terminal, or 
at the anode 3 and is called the anion. (See 
Electrolysis, Kathion. Anion) 

Ions, Electro-Negative —The neg- 
ative atoms, or groups of atoms, called rad- 
icals, into which the molecules of an electro- 



Ion.J 



294 



[ISO. 



lyte are decomposed by electrolysis. (See 
Electrolysis.) 

The electro-negative ions are called the anions, 
because they appear at the anode of a decompo- 
sition cell. (See Anions. Anode.) 

Ions, Electro-Positive The pos- 
itive atoms, or groups of atoms, called rad- 
icals, into which the molecules of an electro- 
lyte are decomposed by electrolysis. (See 
Electrolysis) 

The electro-positive ions are called the kathions, 
because they appear at the kathode of a decom- 
position cell. (See Kathion. Kathode.) 

Iron-Clad Electro-Magnet. — (See Mag- 
net, Electro, Iron- Clad.) 

Iron-Clad Magnet.— (See Magnet, Iron- 
Clad) 

Iron Core, Effect of, on the Magnetic 
Strength of a Hollow Coil of Wire 

An increase in the number of lines of mag- 
netic force, beyond those produced by the 
current itself, due to the opening out of the 
closed magnetic circuits in the atoms or 
molecules of the iron. 

The atoms or molecules of the iron possess 
naturally closed magnetic circuits, or closed lines 
of magnetic force, lying entirely within the mass 
of the iron. When the iron is placed in a magnetic 
field, these minute closed circuits open out and 
are added to the lines of force produced by the 
circuit itself. The opening out of these closed 
atomic or molecular lines of magnetic force is at- 
tended by the formation of lines of polarized 
molecules or atoms. 

Roughly speaking, according to Lodge, for 
each single line of magnetic force produced by the 
electric current, there are some 3,000 lines of 
magnetic force added to it from the iron, the ex- 
act number varying with the kind of iron, the 
physical condition of the iron and the degree of 
magnetization. 

Iron, Galvanized — Iron covered by 

a layer of zinc by dipping it in a bath of 
molten zinc. 

The process of galvanizing iron is designed to 
prevent the corrosion or rusting of the iron on 
exposure to the air. {See Metals, Electrical Pro- 
tection of.) 

The word galvanized probably had its origin in 



an assumed galvanic or voltaic action, in causing 
the zinc to adhere to the iron. The true galvanic 
or voltaic action, viz., the galvanic protection, 
comes after the galvanizing process is completed. 

Iron-Work Fault of Dynamo. — (See 
Fault, Iron- Work, of Dynamo) 

Irreversible Heat. — (See Heat, Irreversi- 
ble) 

Irritability, Electric Irritability 

of nervous or muscular tissue by an electric 
discharge. 

Irritability, Electric, Diminished 

A decreased irritability of nervous or muscu- 
lar tissue, produced by an electric current of 
given strength. 

Diminished electric irritability is often present 
in certain diseases of the motor apparatus. 

Irritability, Electric, Increased 

An irritability of nervous or muscular tissue 
produced by a much weaker electric current 
than that required to produce it in normal 
tissue. 

Irritability, Faradic —Muscular 

contractions produced by the action of a 
faradic current on a nerve. 

The action of the faradic current is to cause a 
prolonged tonic contraction, which, continues 
while the current continues. Though, the natural 
action is to produce a contraction, followed by a 
relaxation on each make and break, yet the makes 
and breaks follow one another so rapidly that the 
relaxation has not time to occur before the next 
contraction follows. 

Irritability, Galvanic Muscular 

contractions produced by the action of a gal- 
vanic current. 

The action of a galvanic current is to cause a 
single, quick, momentary contraction of a muscle 
on each starting or completion of the circuit. 

The contractions are stronger in the case of 
galvanic currents when the direction of the cur- 
rent is reversed with a commutator instead of by 
an actual break at the poles. Such a break is 
called a voltaic alternative, and the currents so pro- 
duced voltaic alternatives. (See Alternatives, 
Voltaic.) 

Isobaric Lines. — (See Lines, Isobaric.) 

Isobars. — Lines connecting places on the 



Iso.] 



295 



[Jar. 



earth's surface which have the same barome- 
tric pressure. 

The isobaric lines are generally corrected for 
differences of elevation of the surface. 

Isobars are often called isobaric lines. 

A study of the isobaric lines, or isobars, is of 
great assistance in making forecasts or predictions 
of coming changes in the weather. 

ISOCliasmen Curves.— (See Curves, Iso- 
ckasmen?) 

Isochronism. — Equality of time of vibra- 
tion or motion. 

Isoehronize. — To produce equality of 
time of vibration or motion. — (See Isochron- 
ism^) 

Isochroiiizing. — Producing equality of 
time of vibration or motion. (See Isochron- 
ism^) 

Isochronous Titrations or Oscillations. 
— (See Vibrations or Oscillations, Isochron- 
ous.) 

Isoclinic Chart. — (See Chart, Inclina- 
tion?) 

Isoclinic Lines. — (See Lines, Isoclinic?) 

Isc dynamic Chart. — (See Chart, Isody- 
namis.) 



Isodynamic Lines. — (See Lines, Isody- 
namic.) 

Isodynamic Map. — (See Chart, Isody- 
namic.) 

Iso-Eleetric Points.— (See Points, Iso- 
electric.) 

Isogonal. — Pertaining to the isogonic lines. 

Isogonal Lines. — (See Lines, Isogonal?) 

Isogonal Map or Chart.— (See Map or 
Chart, Isogonal?) 

Isogonic. — Pertaining to the isogonal lines. 

Isotonic Chart. — (See Chart, Isogonic.) 

Isogonic Lines. — (See Lines, Isogonic) 

Isogonic Map.— (See Map, Isogonic) 

Isolated Electric Lighting.— (See Light- 
ing, Electric, Isolated?) 

Isolatine. — A kind of insulating material. 

Isothermal Surfaces. — (See Surfaces, Iso- 
thermal.) 

Isotropic Conductor. — (See Co7iductor t 
Isotropic?) 

Isotropic Medium. — (See Medium, Iso- 
tropic.) 



J. — A contraction proposed for Joule. 

Jablochkoff Candle. — (See Candle, Jab- 
loch koff.) 

Jacketed Magnet. — (See Magnet, Jack- 
eted.) 

Jacohi's LatY. — (See Lazv.Jacobi's?) 

Jar, Electric — A name formerly 

given to the Leyden jar. 

Jar, Leyden A condenser in the 

form of a jar, in which the metallic coatings 
are placed opposite each other on the outside 
and the inside of the jar respectively. 

The metal coatings should not extend to more 
than two-thirds of the height of the jar, the rest 
of the glass being varnished to avoid the creeping 
of the charges over the glass in damp weather. 
The inside coating is connected by means of a 



metallic chain to a knob on the top of the jar, as 
shown in Fig. 313. The conductor supporting 
the knob passes through a dry cork or plug of 
some insulating material. 

To charge the jar, the outside coating is con- 
nected with the earth, as 
by holding it in the hand, 
and the outside coating 
is connected with the 
conductor of a machine. 
(See Condenser. Accu- 
mulator. ) 

The inner coating of 
the jar is usually con- 
nected with the knob by 

£ 1 . . Fif. 3 t?. Leyden Jar. 

means of a chain or wire J J 

as shown above. This necessitates a support for 
the ball and stem, which is generally obtained by 
a cork or wooden plug inserted in the mouth of 




Jar.] 



296 



[Jet. 



the jar. Such a form, however, is extremely ob- 
jectionable, since, although the top of the jar be 
covered with shellac varnish to avoid leakage, it 
affords but a poor insulation in damp weather, be- 
cause both the metallic rod supporting the ball and 





Fige 314° Sir William Thomson's Ley den Jar* 

the damp wood or cork are in connection with the 
glass and thus facilitate leakage. 

To overcome these objections a form of jar has 
been devised by Sir William Thomson, in which the 
knob is supported on three feet, which rest on the 
inner coating. In this form the uncoated glass 
can be readily kept dry and clean. This form is 
shown in Fig. 314. 

A layer of sulphuric acid is sometimes employed 
for the inner coating of the Ley den jar. This 
serves the double purpose of acting as a coating 
and an absorber of moisture during damp 
weather. 

Jar, Leyden, Capacity of —The 

quantity of electricity a Leyden jar will hold 
at a given difference of potential. 

The capacity of a jar is equal to the quantity 
of electricity divided by the difference of potential 
such quantity produces in the jar; or the capacity 

= ~, where Q = the quantity, and V, the differ- 
ence of potential. 

Jar, Leyden, Coatings of — (See 

Coatings of Leydeii Jar.) 

Jar, Lightning A Leyden jar, the 

coatings of which consist of metallic filings. 

As the discharge passes, an irregular series of 
sparks appear, which somewhat resemble in their 
shape a lightning flash. Hence the origin of the 
term. 

Jar of Secondary Cell. — The containing 



vessel in which the plates of a single secondary 
cell are placed. 

Jar, Porous A porous cell. (See 

Cell, Porous.) 

Jar, Scintillating A Leyden jar, 

the coatings of which, instead of being formed 
of continuous sheets of tin-foil or other con- 
ducting substances, are formed of small pieces 
of such substances, placed at regular intervals 
on the glass or dielectric so as to leave a small 
space between them. 

Such a jar has received the name of scintillat- 
ing jar, because when discharged by connecting 
its two opposite coatings the discharge appears as 
minute sparks, which jump across the space 
between the metallic pieces. 

Jar, Unit A small Leyden jar some- 
times employed to measure approximately the 
quantity of electricity passed into a Leyden 
battery or condenser. 

As shown in Fig. 315, the unit jar consists of a 
small Leyden jar j, whose outer coating is con- 
nected with a sliding metallic 
rod b, provided at each end 
with a rounded knob, and the 
inner coating of which is con- 
nected with a metallic knob c, 
placed as shown, inside a 
glass jar d, opposite a ball on 
the lower end of b. 

When, now, the inside of 
the unit jar, or the end con- 
nected with c, is connected 
with the charging source, such 
as a machine, and the outside 
at a, is connected with the jar 
or jars to be charged, for 
every spark that passes be- 
tween d and c, a definite quantity has passed a. 

The value of this unit charge may be varied by 
varying the distance between d and c. 

The smaller the unit jar is in proportion to the 
jar to be charged, and the shorter the distance 
between c and d, the more reliable are the com- 
parative results obtained. 

Jars, Leyden, Charging, by Cascade 

— (See Cascade, Charging Leyden Jars by.) 
Jet, Gas, Carcel Standard — A 

lighted gas jet employed for determining the 
candle-power of gas by measuring the height 




Fig>3T5. Unit Jar. 



Jet. 



297 



[Joi. 



of a jet of gas burning under a given press- 
ure, and used in connection with the light of 
a larger gas burner, burning under similar 
conditions, for the photometric measurement 
of electric lights. 



The twisted joint is sometimes subsequently- 
soldered. 




Fig, 31 6. Seven- Ca reel 
Standard Gas Jet. 



Fig, 317. Carcel Candle 
Burner. 



In Fig. 316 is shown a section of a seven-carcel 
standard gas jet, and in Fig. 317, a section of a 
candle burner, connected within the same service 
pipe. The gas for both burners is received in a 
chamber, from whence it passes by an opening to 
the burner, under the constant pressure obtained 
by the weight of the bell C, ar.d the tube A. The 
burner shown in Fig. 317, which is used as the 
standard of comparison, will give a candle-power 
determined from the height of the jet of the 
burning gas. This height is measured in milli- 
metres by the motion of a circular screen. 

The determination of the candle-power of gas by 
means of a jet photometer is only approximately 
correct, unless many precautions are taken. 

Jet Photometer. — (See Photometer, Jet) 
Jewelry, Electric Minute incan- 
descent electric lamps substituted for the 
rarer gems in articles of jewelry. 

The lamps are lighted by means of small pri- 
mary or storage batteries, carried in the pocket or 
elsewhere on the person. 

Joint, American Twist A tele- 
graphic or telephonic joint in which each of 
the two wires is twisted around the other. 
(Szz Joint, Telegraphic or Telephonic?) 



Fig. 3 18. American Twist Joint. 

The American twist joint is shown in Fig. 318. 
This joint is easily made and is very serviceable. 

Joint, Bell-Hanger's A joint for 

telegraphic or telephonic wires in which the 
ends are merely looped together. (See Joi?it , 
Telegraphic or Telephonic?) 

Joint, Britannia A telegraphic or 

telephonic joint in which the wires are laid 
side by side, bound together and subsequently 
soldered. (See Joint, Telegraphic or Tele- 
pho?iic.) 




Fig. 3ig. Britannia Joint. 

The Britannia joint is shown in Fig. 319. No. 
16 wire, B. W. G., is used as the binding wire. 

Joint, Butt An end-to-end joint. 

A joint effected in wires by placing the 
wires end on and subsequently soldering. 

Butt joints are formed by bringing the ends to 
be joined together and securing them while in 
such position. 

Joint, Butt and Lap, of Belts —The 

joint in a leather belt, employed for transmit- 
ting power from a line of shafting where the 
ends are simply brought together and laced, 
is called a butt joint, in contradistinction to a 
lap joint, or a joint formed by placing one end 
of the belt over the other and lacing or rivet- 
ing the two. 

In using delicate galvanometers, the slightest 
change in the speed of the engine driving the 
dynamo-electric machine producing the current, 
causes an annoying fluctuation of the needle that 
prevents accurate reading, when lap joints are used 
in the belt instead of butt joints, unless the former 
are very carefully made. Lap joints may also cause 
a flickering in the lights. Wh°n, however, lap 
joints are made by cutting the belt by an oblique 
section and properly securing them so that their 



Joi.] 



298 



[Joi. 



elevation at the joint is no greater than elsewhere, 
the lap joint is preferable to the butt joint. 

Joint, Expansion A j oint for under- 
ground conductors, tubes or pipes, exposed 
to considerable changes of temperature, in 
which a sliding joint is provided to safely 
permit a change of length on expansion or 
contraction. 

Joint, Insulation A joint in an insu- 
lating material or covering in which a conti- 
nuity is insured in the conducting as well as 
the insulating substance. 

Joint, Lap A joint effected by over- 
lapping short portions near the ends of the 
things to be joined, and securing them while 
in such position. 

Joint, Lap, for Wires A joint 

effected between two wires by overlapping 
their ends and subsequently soldering. 



Joint, Magnetic 



-The line of junc- 



tion between two separate parts of magnetiza- 
ble materal. 

Magnetic joints should be of such a nature as 
to permit the passage of the lines of magnetic 
force with the least increase in the resistance of 
the magnetic circuit. 

Magnetic joints in the field magnets of a dynamo- 
electric machine should be as few as possible, since 
the resistance of the best magnetic joint to the 
passage of the lines of force is necessarily greater 
than that of the same material without such 
joints. 

Joint, Metallic Conducting A joint 

in a conductor in which a continuity of con- 
ducting power is secured. 

Joint Resistance of Parallel Circuits. — ■ 

(See Resistance, Joint, of Parallel Circuits?) 

Joint, Sleeve ■ — A junction of the 

ends of conducting wires obtained by passing 
them through tubes and then twisting and 
soldering. 

All joints should be soldered, but in so doing 
care must be taken that the soldering liquid or 
solid employed is free from acids or other corro- 
sive materials, and that all traces of the soldering 
liquid or solid are removed from the wire before 
the joint is covered with insulating material. 
Kerite, okonite or other insulating tape, should 



preferably be wrapped around the joint after 
it is soldered. 

In making a joint in a gutta-percha covered 
wire, such as a submarine cable, the following 
method may be employed: The bared and 
cleansed wires are twisted together and soldered. 
The soldered joint is then covered with a layer 
of plastic insulating material made of a mixture 
of gutta-percha, tar and rosin. (See Chattertori 's 
Compound.) In order to insure a good junction 
between this and the gutta-percha covering on the 
rest of the wire, the outer surface of the gutta- 
percha is removed for about two inches from each 
side of the joint, so as to remove its oxidized sur- 
face. After the coating is put on, it is warmed 
gently by a warm joining tool, not by the fhme 
of a lamp. A sheet of warmed gutta-percha is 
then wrapped around the joint, and while it and 
the joint are still hot, another coating of the 
plastic insulating material is applied. Successive 
layers of gutta-percha and some other insulating 
material are generally applied in the case of sub- 
marine cables. — ( Culley . ) 

Joint, Telegraphic, Mclntire's Parallel 

Sleeve A joint for telegraphic or other 

wires, in which the ends to be joined are 
slipped into parallel sleeves or tubes, which 
are afterward twisted around each other. 

A general view of the parallel sleeve joint, both 
before and after twisting, is shown in Fig. 320. 




Fig. 320. Mclntire's Parallel Sleeve Joint. 

The twisting is done by means of the specially 
devised twisting clamp shown in Fig. 321. 




Fig. 321. Twisting Clamp for Mclntire's Parallel Joint, 

Joint, Telegraphic or Telephonic • 

A juncture of the ends of two electric con- 
ductors so as to insure a permanent junc- 
tion whose resistance shall not be appreci- 
ably greater per unit of length than that of 
the rest of the wire. 



Joie] 

In making a joint, care should always be taken 
to scrape the insulating material from the wires 
and clean their surfaces before twisting them to- 
gether. 

Telegraph wires were formerly joined by the 
ordinary bell-hangers' joint; that is, the wires were 
simply looped together. The constant vibrations 
to which the wires are subjected caused such a 
joint to be abandoned and an improvement intro- 
duced by bolting the ends together, as shown in 
Fig. 322. 



Fig. 322. Telegraphic Joint. 



Joint, Testing of 



-Ascertaining the 



resistance of the insulating material around 
a joint in a cable. 

The resistance of the insulating material of a 
cable at a joint is necessarily high, since the 
joint forms but a small part of length of the cable. 
It should not, however, be large as compared with 
an equal length of another part of the cable with 
a perfect core. 

Two methods for testing cable joints are gener- 
ally employed, viz. : 

(1.) A conductor is charged through the joints 
for a given time, and the deflection obtained by 
its discharge compared with the discharge of the 
same condenser charged for an equal length of 
time through a few feet of perfect cable. 

(2. ) A charged conductor is permitted to dis- 
charge itself through the joint, and the amount 
lost in a given time noted. 

For description of different methods, see 
Kempe's " Handbook of Electrical Testing." 

Joulad. — A term proposed for- the Joule. 



299 [Kao. 

This term is not generally adopted. (See 
Joule.) 

Joule. — The unit of electric energy or 
work. 

The volt-coulomb. 

The amount of electric work required to 
raise the potential of one coulomb of elec- 
tricity one volt. 

The joule may be regarded as a unit of energy 
or work in general, apart from electrical work or 
energy. 

1 joule , .... = 10,000,000 ergs. 

1 joule = .73732 foot-pounds. 

I joule = 1 volt-coulomb. 

1 joule = .24 calorie. 

4.2 joules = 1 small calorie. 

1 joule per second = 1 watt. 

The British Association proposed to call one 
joule the work done by one watt in one second. 

Joule, as a Heat Unit. — The quantity of 
heat developed by the passage of a current 
of one ampere through a resistance of one 
ohm. (See Joule?) 

Joule Effect.— (See Effect, Joule) 

Joule's Cylindrical Electro-Magnet. — 

(See Magnet, Electro, Joule's Cylindrical?) 

Joule's Law. — (See Laws oj Joule) 
Junction Box. — (See Box, Junction) 
Jump-Spark Burner. — (See Burner r 

fump-Spark) 
Junction, Thermo-Electric. — A junction 

between any thermo-electric couple. (See 

Cell, Thermo-Electric) 



K. — A contraction for electrostatic capa- 
city. (See Capacity, Electrostatic) 

K. C. C. — In electro-therapeutics, a brief 
method of writing kathodic closure contrac- 
tion, or the effects of muscular contraction 
observed at the kathode on the closure of a 
circuit. 

K. J). C. — In electro-therapeutics, a brief 
method of writing kathodic duration con- 



traction, or the effects of muscular contrac- 
tion observed at the kathode after the current 
has been passing for some time. 

K. W. — A contraction for kilo-watt. (See 
Watt, Kilo) 

Kaolin. — A variety of white clay some- 
times employed for insulating purposes. 

Jablochkoff sometimes employed kaolin be- 
tween the parallel carbons of his electric candle 



Kap.] 



300 



[Key. 



for the purpose of insulating them from each 
other. He also devised an electric lamp in which 
a spark of considerable difference of potential, 
obtained from an ordinary induction coil, was 
caused to raise a surface of kaolin to incan- 
descence by passage over it. 

Kapp Lines. — (See Lines, Kapp?) 

Kartayert. — A kind of insulating material. 

Katelectrotonus. — A word sometimes used 
instead of kathelectrotonus. (See Kathe- 
lectrotonus?) 

Kathelectrotonic State. — (See State, 
Kathelectrotonic?) 

Kathelectrotonic Zone. — (See Zone, 
Kathelectrotonic?) 

Kathelectrotonus. — In electro-therapeu- 
tics, the condition of increased functional ac- 
tivity that occurs in a nerve in the neighbor- 
hood of the kathode or negative electrode. 
(See Electroto?ius.) 

Kathion. — The electro-positive ion, atom 
or radical into which the molecule of an 
electrolyte is decomposed by electrolysis. 
(See Electrolysis. Ions.) 

Kathion is sometimes written cathion. 

In electrolysis the kathion, or the electro-posi- 
tive ion or radical, appears at the kathode or 
electro-negative electrode. Similarly, the anion, 
or the electro-negative ion or radical, appears at 
the anode or the electro-positive electrode. 

Kathodal. — Pertaining to the kathode. 
(See Kathode?) 

Kathode. — The conductor or plate of an 
electro-decomposition cell connected with the 
negative terminal or electrode of a battery or 
other source. 

The word kathode is sometimes applied to the 
negative terminal of a battery or source, whether 
connected with a decomposition cell or not. It 
is preferable, however, to restrict its use to de- 
composition cells. (See Anode.) 

The word kathode is sometimes written cathode. 

Kathodic. — Pertaining to the kathode. 
(See Kathode?) 
Kathodic Electro-Diagnostic Reactions. 

— (See Reactions, Electro-Diagnostic?) 

Keeper of Magnet. — (See Magnet, Keeper 
of.) 



Kerite. — An insulating material. 
Kerr Effect— (See Effect, Kerr.) 
Key Board. — (See Board, Key.) 

Key, Capillary Contact A form of 

fluid contact in which the circuit is closed or 
broken by means of a wire which is dipped 
into or removed from the surface of a mass 
of mercury. 

In order to avoid an increase in the resistance 
of the circuit, due to the formation of oxide of 
mercury, the contact surface of the mercury is 
kept covered with a layer of dilute alcohol. 

Key, Discharge A key employed to 

enable the discharge from a condenser or 
cable to be readily passed through a galva- 
nometer for purposes of measurement. 

Key, Discharge, Kempe's A dis- 
charge key constructed as shown in Fig. 323. 




Fig. 323. Kempe's Discharge Key. 

The solid lever, hinged at one extremity, plays 
between two contacts connected to two terminals, 
and has two finger triggers at its free end marked 
"Discharge" and "Insulate," connected respec- 
tively to two ebonite hooks. The hook attached 
to that marked " Discharge " is a little higher than 
the other, so that when the lever is caught against 
it, the key rests in an intermediate position be- 
tween the contacts, and, when caught against the 
lower trigger, it rests against the bottom contact. 
When in the last position, a depression of the 
" Insulate " trigger causes the lever to spring up 
against the second hook, thus insulating it from 
either contact, and on the depression of the "Dis- 
charge " trigger, the lever springs up against the 
top contact. 

Key, Discharge, Webb's A dis- 
charge key constructed as shown in Fig. 324. 

A horizontal lever L, Fig. 324, passing between 
two contacts and hinged at J, is pressed upward 
by a spring. The free end of this lever termi- 
nates in two steps, 1 and 2. A vertical lever, pro- 



Key.] 



301 



[Key. 



vided with an insulating handle, is jointed at J', 
and has at C, a projecting metallic tongue that 
engages in the upper step when the lever H, is 
vertical, and on the lower step when it is slightly 
moved from the free end. 

When the projection C, rests on the lower step 
2, the lever L, is intermediate between the top 
and bottom contacts, and is, therefore, discon- 




Fig. 324. Webb's Discharge Key. 



nected from either of them; but, when it rests on 
the upper step, it is in contact with the lower 
contact. 

When the lever H, is so moved as to have the 
projection C, away from both steps, the lever L, 
is pressed by its spring against the upper contact. 

The battery terminals are connected with the 
condenser terminals when the lever L, is touching 
the lower contact, but when the lever L, touches 
the top contact, the condenser is connected with 
the galvanometer terminals. 

Key, Double-Contact Form of Bridge, 

— A key designed to succes- 



Sprague's — 

sively close two separate circuits. 




12 3 4, 

Fig. 32 5. Spraguc's Double-Contact Key. 

Sprague's double-contact key is shown in Fig. 
325. On depressing K, the contacts c, c, are first 
closed and afterwards contacts at c', c'. Metallic 



pieces, I, 2, 3 and 4, serve to make contacts with 
apparatus used in connection with the key. 

The battery circuit is connected to I and 2, 
and the galvanometer to 3 and 4, so that the bat- 
tery circuit is closed first, and the galvanometer 
afterwards. This form of key is used in connec- 
tion with the Wheatstone Bridge. 

Key, Double-Contact, Lambert's 

A key used in cable-work, and constructed 
as shown in Fig. 326. 

qOffttS ^&wk 




glsb Fig. 326. Lambert's Double- Contact Key. 



In Thomson's method for the determination of 
electrostatic capacity, the capacity of the cable 
is compared with that of a condenser containing 
a known charge. These two charges are so con- 
nected electrically as to discharge into and 
neutralize each other if equal, but if not, to pro- 
duce a galvanometer deflection by a charge 
equal to their difference. 

A Lambert double contact key is shown in Fig. 
326. The connections are such that the pushing 
forward of K, depresses keys that permit a bat- 
tery to simultaneously charge the condenser and 
the cable. On drawing K, back, the two charges 
are allowed to mix. Then on depressing K, the 
difference of the charges, if any, is discharged 
through the galvanometer. 

Key, Double-Tapper The key used 



in a system of needle telegraphy to send 
electric impulses through the lines in alter- 
nately opposite directions. (See Telegraphy, 
Single-Needle?) 

Key, Increment A telegraphic key 

so connected that an increase or increment 
in the line current occurs whenever the key is 
depressed. 

The increment key is used in duplex and quad- 
ruplex systems of telegraphic transmission. 

Key, Increment, of Quadruplex Tele- 
graphic System A key employed to 

increase the strength of the current and so 
operate one of the distant instruments in a 



Key.] 



302 



[Key. 



quadruplex system by an increase in the 
strength of the current. (See Telegraphy, 
Quadruple*?) 

Key, Magneto-Electric A tele- 
graph key for sending an electric impulse 
into a line, so arranged that a coil of wire on 
an armature connected with the key lever is, 
by the movements of the key, moved toward 
or from the poles of a permanent magnet, the 
movements of the key thus producing the 
currents sent into the line. 

Key, Plug A simple torm of key in 

which a connection is readily made or broken 
by the insertion of a plug of metal between 
two metallic plates that are thus introduced 
into a circuit. 

A form of plug key is shown in Fig. 327. 




Key, Reversing A key inserted in 

the circuit of a galvanometer for obtaining 
deflections of the needle on either side of the 
galvanometer scale. 

A form of reversing key is shown in Fig. 328. 
The galvanometer terminals are connected to the 
binding posts 2 and 3, and the circuit terminals 
to the other two posts. On depressing K, the 




Fig: 328. Reversing Key. 

current flows m one direction and on depressing 
K', it flows in the opposite direction. Clamps, 
operated by handles, are provided so as to close 
either of the keys permanently, if so desired. 



Key, Reversing, of Quadruplex Tele- 
graphic System A key employed to 

reverse the direction of the current and so 
operate one of the distant instruments, in a 
quadruplex system, by a change in the 
direction of the current. (See Telegraphy, 
Quadruplex?) 

Key, Short-Circuit A key which 

in its normal condition short circuits the gal- 
vanometer. 




Fig. 329. Short- Circuit Key. 

Such a short-circuit key is provided for the 
purpose of protecting the galvanometer from in- 
jury by large currents being accidentally passed 
through its coils. In the form shown in Fig. 329, 
the spring S, rests against a platinum contact ;: 
but when depressed by the insulated head at K, 
it rests against an ebonite contact, and throws 
the galvanometer into the desired circuit. 

The key is provided with double binding posts 
at P and N, for convenience of attachment to re- 
sistance coils, batteries, etc. 

In the form of a short-circuit key shown in Fig. 
330, a catch is provided for the purpose of keep- 
ing the key down when once depressed. Its 
arrangement will be readily understood from an 
inspecdon of the figure. 




Fig. 330. Short- Circuit Key. 

Key, Sliding-Contact The key em- 
ployed in the slide form of Wheatstone 
bridge, to make contact with the wire over 
which the sliding contact passes. (See 
Bridge, Electric, Slide Form of.) 



Key.] 



303 



[Kit. 



Key, Stationary Floor 



-An electric 



key or push button placed on the floor so as 
to be readily closed by the foot. 

This form of key is especially suitable for use 
in connection with an electric bell and annuncia- 
tor for readily calling an attendant. (See Annun- 
ciator^ Electro-Magnetic.} 

Key, Telegraphic The key em- 
ployed for sending over the line the successive 
makes and breaks that produce the dots and 
dashes of the Morse alphabet, or the deflec- 
tions of the needle of the needle telegraph. 
(See Telegraphy ; America?i System of.) 

Kick. — A recoil. 

Kicking Coil. — (See Coil, Kicking) 

Kilo (as a prefix). — One thousand times. 

Kiloampere. — One thousand amperes. 

Kiloampere Balance. — (See Balance, 
Kiloanipere.) 

Kilodyne. — One thousand dynes. (See 
Dyne.) 

Kilogramme. — One thousand grammes, 
or 2.2046 pounds avoirdupois. (See Weights, 
French System of) 

Kilojonle. — One thousand joules. 

Kilometre. — One thousand metres. 

Kilowatt. — One thousand watts. 

Kilowatt Hour. — (See Hour, Kilowatt.) 

Kine. — A unit of velocity proposed by the 
British Association. 

A kine equals 1 centimetre per second. 

Kinetic Energy. — (See Energy, Kinetic.) 

Kinetic Theory of Matter.— (See Matter, 
Kinetic Theory of.) 

Kinetics, Electro A term some- 
times applied to the phenomena of electric 
currents, or electricity in motion, as distin- 
guished from electrostatics, or the phenom- 
ena of electric charges, or electricity at rest. 

Kinetograph. — A device for the simultane- 
ous reproduction of a distant stage and its 
actors under circumstances such that the 
actors can be heard at any distance from the 
theatre. 

The sounds heard by the distant audience are 
actual reproductions of those uttered during the 



performance, though not at the time of their 
utterance. The appearance of the stage and its 
actors represents the appearance of a previous 
reproduction of the play or opera or other per- 
formance, as taken by means of a Kodak camera 
with a film cylinder and drop shutter, operated 
by an electric motor, exposing, say, forty plates 
a second. By means of a projecting lantern these 
photographic pictures are thrown on a curtain on 
a stage at the distant theatre in regular order of 
sequence, while a loud- speaking phonograph 
puts song and speech into the mouths of the 
mimic actors and thus gives the phantom stage 
the semblance of life and reality. 



Kite, Franklin's 



-A kite raised in 



Philadelphia, Pa., in June, 1752, by means of 
which Franklin experimentally demonstrated 
the identity between lightning and electricity, 
and which, therefore, led to the invention of 
the lightning rod. 

It is true that Dalibard, on the 10th of May, 
1752, prior to Franklin's experiment, succeeded 
in drawing sparks from a tall iron pole he had 
erected in France. This experiment was, how- 
ever, tried at the suggestion of Franklin, to whom 
it must properly be ascribed. 

A description of this kite is given by Franklin 
in the following letter: 

Letter XI, from Benj. Franklin, Esq., of Phil- 
adelphia, to Peter Collinson, Esq., 
F. R. S., London. 

"Oct. 19, 1752. 

"As frequent mention is made in public papers, 
from Europe, of the success of the Philadelphia 
experiment for drawing the electric fire from 
clouds by means of pointed rods of iron erected 
on high buildings, etc., it may be agreeable to 
the curious to be informed that the same experi- 
ment has succeeded in Philadelphia, though 
made in a different and more easy manner, which 
is as follows: 

" Make a small cross of two light strips of cedar, 
the arms so long as to reach to the four corners of a 
large thin handkerchief when extended ; tie the 
corners of the handkerchief to the extremities of 
the cross, so you have the body of a kite, which, 
being properly accommodated with a tail, loop 
and string, will rise in the air like those made of 
paper, but this, being of silk, is fitter to bear the 
wet and wind of a thunder gust without tearing. 
To the top of the uptight stick of the cross is to 



KniJ 



30i 



[Lag. 



be fixed a very sharp pointed wire rising a foot 
or more above the wood. To the end of the 
twine, next the hand, is to be tied a silk ribbon, 
and where the silk and twine join, a key may be 
fastened. This kite is to be raised when a thun- 
der gust appears to be coming on, and the per- 
son who holds the string must stand within a 
door or window, or under some cover, so that 
the silk ribbon may not be wet, and care must be 
taken that the twine does not touch the frame of 
the door or window. As soon as any of the 
thunder clouds come over the kite the pointed 
wire will draw the electric fire from them, and 
the kite, with all the twine, will be electrified, 
and the loose filaments of the twine will stand 
out every way, and be attracted by an approach- 
ing finger. And when the rain has wet the kite 
and twine so that it can conduct the electric fire 
freely, you will find it stream out plentifully from 
the key on the approach of your knuckle. At 
this key the phial may be charged, and from 
electric fire thus obtained spirits may be kindled, 
and all the other electric experiments be per- 
formed, which are usually done by the help of a 



rubbed glass globe or tube, and thereby the 
sameness of the electric matter with that of light- 
ning completely demonstrated. 

"B. Franklin." 

Knife Break Switch.— (See Switch, Knife 
Break) 

Knot or Nautical Mile. — A length equal 
to 6,087 feet. 

The English statute mile is equal to 5,280 feet. 
The value of the nautical mile is therefore in excess 
of that of the statute mile. 

Kohlrausch's Law. — (See Law of Kohl- 
rausch.) 

Krizik's Bars. — (See Bars, Krizik's) 
Kyanized. — Subjected to the kyanizing- 
process. (See Kyanizingi) 

Kyanizing. — A process employed for the 
preservation of wooden telegraphic poles by 
injecting a solution of corrosive sublimate 
into the pores of the wood. (See Pole, Tele- 
graphic) 



L. — A contraction for co-efficient of in- 
ductance. (See Inductance, Co-efficient of.) 

L. — A contraction for length. 

Labile Galvanization. — (See Galvaniza- 
tion, Labile.) 

Lag", Angle of The angle through 

which the axis of magnetism of the armature 
of a dynamo-electric machine is shifted by 
reason of the resistance its core offers to sud- 
den reversals of magnetization. 

An armature of a bi polar dynamo electric ma- 
chine has its magnetism reversed twice in every 
rotation. The iron of the core resists these mag- 
netic reversals. The result of this resistance is to 
shift the axis of magnetism in the direction of ro- 
tation. The angle through which the axis has 
thereby been shifted is called the angle of lag. 

The term, angle of lag, is sometimes incorrectly 
applied so as to include a similar result produced 
by the magnetization due to the armature current 
itself. It is this latter action which, in armatures 
With soft iron cores, is the main cause of the angle 



of lead. (See Brushes, Lead of. Lead^ Angle 
of-) 
Lag, Angle of, of Current An 

angle whose tangent is equal to the ratio of 
the inductive to the ohmic resistance. 

An angle, the tangent of which is equal to 
the inductive resistance of the circuit, divided 
by the ohmic resistance of the circuit. 

An angle, the co-sine of which is equal to 
the ohmic resistance of the circuit, divided 
by the impedance of the circuit. 

Lag", Magnetic A magnetic viscos- 
ity as manifested by the sluggishness with 
which a magnetizing force produces its mag- 
netizing effects in iron. 

The tendency of the iron core of a magnet, 
or of the armature of a dynamo-electric ma- 
chine, to resist, and, therefore, retard mag- 
netization. 

This retardation, or lag, is called the magnetic 
lag. 

The lead necessary to give the brushes of a dy- 
namo-electric machine to insure quiet action has by 



Lam.] 



305 



[Lam. 



gome been erroneously ascribed to the magnetic 
lag. The lead, though due to lag in part, in reality 
is mainly due to the resultant magnetization of 
the armature both by the field magnets and by its 
own current. (See Lead, Angle of.) This dis- 
placement of the brushes is measured by an angle 
sometimes, though erroneously, called the angle 
of lag. (See Lag, Angle of.) 

Lamellar Distri- 
bution of Magnet- 
ism. — (See Magnet- 
ism, Lainellar Lis- 
tributiofi of.) 

Laminated Core. 
— (See Core, Latni- 
naied.) 

Laminating' Core. 
— (See Core, Lami- 
nation of.) 

Lamination of 
Armature Core. — 
(See Core, Armature, 
Lamination of) 

Lamination of 
Cores. — (See Core, 
Lamination of.) 
Lamp, All-Night 

A term some- 
times applied to a 
double - carbon arc 
lamp. (See La7np, 
Electric Arc, Double** 
Carbon?) 

A form of all-night 
arc lamp is shown in 
Fig. 331. When the 
consumption of the first 
pair of carbons has Fig. 331. All-Night Arc 
reached a certain limit Lamp. 

the current is automatically switched over to the 
other pair. 

Lamp, All-Night Electric A lamp 

provided with carbon electrodes so as to burn 
all night without recarboning. 

A double-carbon electric lamp. (See 
Lamp, All-Night) 

Lamp, Arc An electric lamp, the 

source of whose light is a voltaic arc. 




Lamp, Arc, Electric An electric 

lamp in which the light is produced by a vol- 
taic arc formed between two or more carbon 
electrodes. 

The carbon electrodes are placed in various 
positions, either parallel, horizontal, inclined 
to one another or vertically one above the other. 
The latter is the form most generally adopted, 
since it permits the ready feeding of the upper 
carbon. 

The carbons are maintained during their con- 
sumption at a constant distance apart, by the aid 
of various feeding devices. Such devices are op- 
erated generally by trains of wheel-work, by me- 
chanical or electrical motors, or by the simple 
action of a spring, by gravity or by the attraction 
of a solenoid. 

The carbon pencils or electrodes are held in 
carbon holders, consisting of clutches or clamps, 
attached to the end of the lamp rods. 

When the lamp is not ia operation the carbons 
are usually in contact with one another ; but, on 
the passage of the current, they are separated 
the required distance by the action 
of an electro-magnet whose coils 
are traversed by the direct or main 
current. 

In order to maintain the elec- 
trodes a constant distance apart, 
the upper carbon in some lamps is 
held in position by the operation of 
a clutch, or, in others, by a detent, 
that engages in a toothed wheel. 
The position of this clutch or de- 
tent is controlled by the action of 
an electro-magnet whose coils are 
usually situated in a shunt or de- 
rived circuit, of high resistance, 
around the electrodes. When the 
carbons are at their normal dis- 
tance apart, the shunt current is 
not of sufficient strength to move 
the clutch or detent from the position in which 
it prevents the downward motion of the upper 
carbon rod. When, however, by the burning 
or consumption of the carbons, the resistance 
of the arc has increased to an extent which can 
be predetermined, the increased current that is 
thereby passed through the shunt circuit is now 
sufficiently strong to release the clutch or de- 
tent, thus permitting the fall or feed of the upper 
carbon. In a well designed lamp this occurs 




Fig. 332. 
Arc Lamp. 



Lam.] 



3C6 



[Lam, 



so gradually as to produce no perceptible effect 
on the steadiness of the light. 

Arc lamps are generally placed in series circuits, 
that is, in circuits in which the current passes suc- 
cessively through all the lamps in the circuit, and 
returns to the source. In order to avoid the break- 
ing of the entire circuit through the extinguish- 
ing of a single arc, on the breaking of its cir- 
cuit, an automatic safety device is provided for 
each lamp. This safety device consists essentially 
of an electro-magnet so placed in a shunt circuit, 
that, as the resistance of the arc becomes too 
great, the increased current, which will then flow 
through the coils of the electro-magnet, at last 
produces a movement of its armature which closes 
a short circuit around the lamp, and thus cuts it 
out of the circuit. 

Arc lamps assume a great variety of forms. A 
well known form is shown in Fig. 332. 

Lamp, Arc, Triple Carbon An arc 

lamp in which three carbon electrodes are 
used. 

The positive carbons consist of two ordinary 
cylindrical carbons, placed parallel to each other. 
The negative carbon is shaped like the figure 8. 
The arc is established between one of the positive 
carbons and the corresponding side of the nega- 
tive carbon. The feeding of the lamp is attended 
by a shifting back and forth of the arc between 
the positive carbons and from side to side of the 
negative carbons. 

The design of the triple carbon arc lamp is to 
produce a lamp of long life. 

Lamp Bracket, Electric 

— (See Bracket, Lamp, 

Electric?) 

Lamp Bulb. — (See Bulb, 
Lamp?) 

Lamp, Carcel — An 

oil lamp employed in France 
as a photometric standard. 

Fig. 333 shows a form of car- 
cel lamp. Like the standard 
candle, the carcel is a standard 
only when it consumes a given 
weight of the light-producing 
substance in a given time. 

Lamp, Chamber of 




placed, and in which is maintained a high 
vacuum. 

The transparency of the lamp chamber and 
consequently the efficiency of the lamp may de- 
crease — 

( 1 . ) From the settling of dust or dirt on its outer 
walls. 

(2.) From the deposit of carbon or metal on its 
inner walls. 

To obviate the first cause of diminished trans- 
parency the outside of the lamp chamber should 
be frequently cleansed. The diminished trans- 
parency, due to the second cause, cannot be 
removed. When it has reached a certain point, it 
is more economical to replace the old lamp by a 
new lamp. 

In a properly made lamp the dimming of the 
lamp chamber is not apt to occur unless a stronger 
current than the normal current is passed through 
the lamp. 

Lamp Clamp. — (See Clamp for Arc 
Lamps.) 

Lamp, Contact A form of semi- 
incandescent electric lamp in which a carbon 
pencil is pressed against a slab of carbon or 
other refractory material. 

The source of light in an electric contact lamp 
is twofold, viz. : 

(1.) A minute arc formed at the points of im- 
perfect contact. 

(2.) The incandescence of the carbon pencil, 
and the points of the slab of carbon against which 
it is pressed. 

Lamp Contacts. — (See Contacts, Lamp?) 
Lamp, Electric, Arc, Carbon Elec- 
trodes for (See Electrodes, Carbon, 

for Arc Lamps.) 

Lamp, Electric, Arc, Differential ■ 



The glass bulb or chamber of 
an incandescing electric lamp 
in which the incandescing 



Fig. 333- 
Carcel La7n£, 

conductor is 



An arc lamp in which the movements of 
the carbons are controlled by the differential 
action of two magnets opposed to each other, 
one of whose coils is in the direct and the 
other in a shunt circuit around the carbons. 

Sometimes the differential coils are placed on 
the same magnet core. 

Lamp, Electric, Arc, Donble Carbon — - 
• — An electric arc lamp provided with two 
pairs of carbon electrodes, so arranged that 
when one pair is consumed, the circuit is auto- 
matically completed through the other pair. 



Lam. J 



307 



[Lam. 



Lamp, Electric Glow 



-A term em- 



ployed mainly in Europe for an incandescent 
electric lamp. (See La?np, Electric, Incan- 
descent*) 

Lamp, Electric, Incandescent An 

electric lamp in which the light is produced 
by the electric incandescence of a strip or 
filament of some refractory substance, gener- 
ally carbon. 

The carbon strip or filament is usually bent into 
the form of a horseshoe or loop, and placed inside 
a glass vessel called the lamp chamber. The 
lamp chamber is exhausted by means of a mercury 
pump, generally to a fairly high vacuum. 

In order to insure the complete removal from 
the lamp chamber of all the air it originally con- 
tained, the carbon strips that are placed within it 
are maintained at a high temperature during the 
process of exhaustion. This temperature, in 
practice, is obtained by sending the current 
through the carbon strip as soon as nearly all 
the air is removed. Towards the end of the 
pumping operation the current is increased so 
as to raise the carbons to their full bril- 
liancy. 

The lamp chamber is also maintained at a 
fairly high temperature. 

To insure this heating of the walls of the lamp 
chamber by the incandescent carbons during 
pumping, for the purpose of driving off all the 
air adhering to the walls of the chamber, they are 
sometimes covered with some readily removable 
preparation of lamp black. 

The operation of driving off the gases absorbed 
by the carbons is termed the occluded gas process, 
and is essential to the successful sealing of an 
incandescent lamp. By its means, a considerable 
quantity of air or other gaseous substances shut 
up or occluded by the carbon is driven out of the 
carbon, which it would be impossible to get rid of 
by the mere operation of pumping. In order to 
insure the success of the operation, it is necessary 
that the heating must take place while the lamp 
is being exhausted, since otherwise the expelled 
gases would be re-absorbed. (See Gas, Occlu- 
sion of. ) 

Both the exhaustion and the incandescence con- 
tinue up to the moment the lamp chamber is 
"hermetically sealed; otherwise, some of the air 
mieht remain in the lamp chamber. 

The lamp chamber is hermetically sealed, 
usually by the fusion of the glass in the manner 




adopted in the sealing of Geissler tubes or 
Crookes' radiometers. 

For the preparation of the carbon strip, its 
carbonization and the flashing of the strip, see 
Carbonization, Processes of. Carbons, Flashing 
Process for. 

The ends of the carbon strip, 
or filament, are attached to lead- 
ing-in wires of platinum that pass 
through the glass walls of the 
lamp chamber, and are fused 
therein by melting the glass 
around them in the same manner 
as are the leading-in wires of the 
Geissler tubes and other similar 
apparatus. 

Incandescent lamps are gener- 
ally connected to the leads or cir- Fig. 334. Incan- 
cuits in multiple-arc or in multi- descent Electric 
pie-series. They are, however, Lamp. 

sometimes connected to the line in series. (See 
Circuits, Varieties of.) 

In the case of multiple-arc or multiple-series 
connection, the resistance of the filament is com- 
paratively high. In the case of series-connec- 
tion the resistance is comparatively low. 

Incandescent electric lamps assume a variety of 
different forms. In all cases, however, the shape 
of the filament is such 
that the leading-in 
wires that carry the 
current to and from 
the filament shall en- 
ter and leave the lamp 
chamber at points that 
are comparatively 
near together. This 
is for the purpose of 
avoiding the unneces • 
sary production of 
shadows. 

Commercial incan- 
descent electric lamps 
are generally marked 
with the potential dif- 
ference in volts that 
must be applied at the 
terminals in order to 
furnish the current 
necessary to properly 
operate them. If this 

potential difference is _. 

, , ,, Fig, 333. Swan Incandescent 

made greater, the can- Lamp. 




Lam.] 



308 



[Lam. 



41e-power of the lamp is greatly increased, but its 
<ife greatly decreased. 

The lamp chamber is more liable in such cases 
!o become less transparent from the deposit of a 
fhin layer of carbon or metal on its inner surfaces. 

In the Swan lamp the filament is made of cot- 
ton thread. These threads are immersed in a 
mixture of two parts of sulphuric acid and one of 
water, which converts the cellulose of the thread 
into artificial parchment. The filaments are rap- 
idly washed as soon as they are removed from the 
sulphuric acid until all traces of the acid are re- 
moved. They are then passed through discs so 
as to insure a uniform area of cross-section, and 
are then wrapped on rods of carbon or earthen- 
ware of the required outline, packed in a crucible 
filled with powdered charcoal, and carbonized. 

The form generally given to the Swan filament 
is that shown in Fig. 335. 

Lamp, Electric, Incandescent Ball 

— An incandescent electric lamp in which 
the light is produced by a sphere or ball of 
carbon placed in an exhausted receiver of 
glass. 

When subjected to the effects of electrostatic 
waves of high frequency of alternation, such a 
lamp becomes luminous 
from the incandescence of 
the carbon ball or sphere. 
Tesla's incandescent ball 
electric lamp is a modifica- 
tion of his straight filament 
lamp. (See Lamp, Incan- 
descent, Straight Filament. ) 

The construction of Tes- 
la's ball incandescent elec- 
tric lamp will be readily 
understood from an inspec- 
tion of Fig. 336. 

Lamp, Electric, In- 
candescent, Half-Shades «*****' *«f ***** 

Lamp. 

(See Half- 




Fig. 336. Testa's In- 



for 



Shades for Incandesce?it Lamps.) 

" Lamp, Electric, Incandescent, Life of 

The number of hours that an incan- 
descent electric lamp, when traversed by the 
normal current, will continue to afford a good 
commercial light. 

The failure of an electric incandescent lamp 
results either irom the volatilization or rupture 
of the carbon conductor, or from the failure of the 



vacuum of the lamp chamber. Since the em- 
ployment of the flashing process, and the process 
for removing the occluded gases, it is not unusual 
for incandescent lamps to have a life of several 
thousand hours. (See Carbons^ Flashing Pro- 
cess for .) 

The life of an incandescent electric lamp should 
not be considered as continuing until the filament 
actually breaks. As soon as the lamp chamber 
has become covered with such a deposit of car- 
bon or coating of metal as to considerably de- 
crease the amount of light which passes through 
the chamber, the lamp should be considered as 
useless. 

Lamp, Electric, Incandescent, Three* 
Filament, for Multi-Phase Circuits 

— An incandescent lamp for use on multi- 
phase circuits, provided with three leading-in 
wires, connected to the free ends of three 
filaments, the other ends of which are con- 
nected in a common joint. 

When properly acting, the current passing 
through each filament should, at any instant, 
equal the sum of the currents in the other two 
filaments, which, as is well known, is the property 
of any three-phase circuit. 

Lamp, Electric, Outrigger for 

(See Outrigger for Electric Lamp^) 

Lamp, Electric, Pendant An in- 
candescent electric lamp suspended by flexible 
twin-wire. 

Lamp, Electric, Safety — An in- 
candescent electric lamp, with thoroughly 
insulated leads, employed in mines, or other 
similar places, where the explosive effects of 
readily ignitable substances are to be feared. 

Such lamps are often directly attached to a 
portable battery, in which case they can be read- 
ily carried about from place to place. 

Lamp, Electric, Semi-Incandescent 

— An electric lamp in which the light is due 
to the combined effects of a voltaic arc and 
electric incandescence. 

In the Reynier semi-incandescent lamp, shown 
in Fig. 337, a thin pencil of carbon C, is gently 
pressed against a block of graphite B. A lateral 
contact is provided at L, through a block of 
graphite I, by means of which the current is con- 



Lam.] 



309 



[Lam, 



veyed to the lower part only of the movable rod 
C, which part alone is rendered incandescent. 
In this lamp, the light is due both to the incan- 

i'C 




Fig. 337' Semi-Incandescent Lamp, 

descence of the rod C, and to the small arc formed 
at J, between its lower end and the contact block 
B, though mainly from the latter. The semi- 
incandescent electric lamp has not as yet been in- 
troduced to any considerable extent. 

Lamp, Electric, Series-Connected Incan- 
descent An incandescent electric lamp 

adapted for use in series circuits, 



m^ 





Fig. 338. Series Incandescent Electric Lamp. 

A form of series incandescent lamp, attached 
to pendant and shade, is shown in Fig. 338. 

In the series connected incandescent lamp, un- 
like the multiple-connected incandescent electric 
lamp, the resistance of the filament is low. This 
is done in order to prevent the total resistance of 



the circuit from requiring too high an electro- 
motive force for operation. In order to preserve 
the continuity of the circuit on the failure of any 
lamp to operate, some form of automatic cut-out 
is employed. This is generally some form of 
film cut-out. (See Cut-Out, Film.) 

Lamp Hour. — (See Hour, Lamp) 

Lamp, Incandescent, Electric Filament 

of A term now generally applied t to the 

incandescing conductor of an incandescent 
electric lamp, whether the same be of very 
small cross-section or of comparatively large 
cross-section. 

The term filament is properly applied to a con- 
ductor containing fibres or filaments extending in 
the general direction of the length of the incan- 
descing conductor. Such a conductor is made of 
carbonizable fibrous material, cut or shaped prior 
to carbonization so as to have its fibres extend- 
ing with their greatest length in the direction of 
length of the filament. 

Lamp, Incandescent, Straight Filament 

An incandescent electric lamp in 

which a straight filament, placed in an ex- 
hausted glass chamber, is rendered luminous 
by the effects of electro- 
static waves or thrusts of 
high frequency. 

The straight filament in ■ 
candescent lamp is the in- 
vention of Tesla. One 
form of such a lamp is 
shown in Fig. 339. 

The glass globe b, of the 
lamp is provided with a 
cylindrical neck, inside of 
which is placed a tube m, 
of conducting material, on 
the side and over the end 
of the insulating plug n. 

The light-giving fila- 
ment e, is a straight car- 
bon stem, connected to the 
plate by a conductor cov- 
ered with a refractory in- 
sulating material k. An 
insulated tube-socket p, 
provided with a metallic lining s, serves to sup- 
port the lamp and connect it with one pole of the 
s jurce of current. It will be noticed that the coat- 




Fig. 339- Testes 
Straight Filament In- 
candescent Lamp. 



lam.] 



310 



[Law. 



ings s and m, form the plates of a condenser. 
The other terminal of the machine may be con- 
nected to the metal coated walls of the room, 
or to metallic plates suspended from the ceiling. 
Lamp Indicator. — (See Indicator, Lamp?) 

Lamp, Pilot In systems for the 

operation of electric lamps, an incandescent 
lamp employed in a station to indicate the 
difference of potential at the dynamo ter- 
minals, by means of the intensity of its emitted 
light. 

Lamp Rod. — (See Rod, Lamp?) 

Lamp Socket Switch. — (See Switch, 
Lamp Socket?) 

Lamps, Bank of — A term applied 

to a number of lamps, equal to about half the 
load, that were formerly placed in view of the 
attendant in circuit with a dynamo that is to 
be placed in a parallel circuit with another 
dynamo, one of the lamps of which is also 
in view. 

When the lamps "in bank " were judged to be 
of the same brilliancy as the one fed by the other 
dynamo, the attendant switched the dynamo par- 
allel with the other, and at the same time cut off 
the bank of lamps from the switched in dynamo. 

The method is, however, wrong. The proper 
way is to make the voltage of the dynamo equal 
to that of the circuit. Then connect it and 
finally raise its electromotive force until it takes 
its share of the load. 

Lamps, Cartooning 1 Placing carbons 

in electric arc lamps. 

When the carbons are consumed, the lamp 
requires recarboning. The old carbon ends are 
replaced by new carbons, and the lamp rods 
cleansed. 

Large Calorie. — (See Calorie, Great?) 

Latent Electricity. — (See Electricity, 
Latent?) 

Lateral Discharge. — (See Discharge, 
Lateral?) 

Lateral Induction. — (See Induction, Lat- 
eral?) 

Lateral Leakage of Lines of Magnetic 
Force. — (See Leakage, Lateral, of Lines of 
Magnetic Force?) 



Lateral Magnetic Leakage.— (See Leak- 
age, Lateral, of Lines of Magnetic Force?) 

Latitude, Magnetic The distance 

a place is situated north or south of the mag- 
netic equator. 

All places that have the same magnetic latitude 
have the same value for the magnetic inclination 
and magnetic intensity, or are on the same isocli- 
nal and isodynamic lines. The magnetic latitude 
is the same at all points of a magnetic parallel. 

Launch, Electric A boat, the mo- 
tive power for which is electricity, suitable for 
launching from a ship. 

Up to the present time electric launches have 
been propelled by means of electric motors, driven 
by means of powerful storage batteries. 

A form of electric launch constructed for the 
English Government is shown in Fig. 340. It is 




Fig. 340. Electric Launch. 

48! feet in length over all, by 8 feet 9 inches 
beam, with an average draft of 2 feet 3 inches. 
Its speed is 8 knots per hour. It will carry forty 
fully equipped soldiers. 

Law, Jacobi's The maximum work 

done by a motor is reached when the counter- 
electromotive force is equal to one-half of the 
impressed electromotive force, or, 



Law, Joule's The heating power of 

a current is proportional to the product of 
the resistance and the square of the current 
strength. (See Heat, Electric?) 

Law, Natural A correct expression 

of the order in which the causes and effects 
of natural phenomena follow one another. 

The law of gravitation, for example, correctly 
expresses the order of sequence of the phenomena 
which result when unsupported bodies fall to the 
earth. It should be carefully borne in mind, how- 
ever, that natural laws cannot be regarded as 
explaining the ultimate causes of natural pheno- 



Law.] 



311 



[Law. 



mena, but merely express their order of occur- 
rence or sequence. 

We are ignorant, for example, of the true cause 
of gravitation and are only acquainted with its 
effects. This is true of all ultimate physical 
causes, save for our belief in their origin in a 
Divine will. 

Law of Electrochemical Equivalence. 

— (See Equivalence, Electro-Chemical, Law 
of.) 

Law of Kolilrausch. — In electrolytic con- 
duction, each atom has a rate of motion for 
a given liquid, which is independent of the 
element with which it may have been com- 
bined. 

In the following table, the rate of motion of 
various kinds of atoms through nearly pure water 
for a difference of potential of one volt per linear 
centimetre, is given: 

H I.08 centimetres per hour. 

K 0.205 centimetre " 

Na 0.126 

Li 0.094 

Ag 0.166 

C 0.213 

1 0.216 

*0 3 0.174 

Law of Ohm, or Law of Current 
Strength. — The strength of a continuous 
current is directly proportional to the differ- 
ence of potential or electromotive force in the 
circuit, and inversely proportional to the re- 
sistance of the circuit, i. e., is equal to the 
quotient arising from dividing the electromo- 
tive force by the resistance. 



^TssrascrasTT- 



- ' I [ r \~ > V 

Fig. 341. Current Strength in Circuit. 
Ohm's law is expressed algebraically thus: 

C = 5; or, E = CR. 
R 

If the electromotive force is given in volts, and 

the resistance in ohms, the formula will give the 

current strength directly in amperes. 



The resistance of any electric circuit, as, for 
example, that shown in Fig. 341, consists of three 
parts, viz.: 

(1.) The internal resistance of the source, r. 

(2.) That of the conducting wires or leads, r'; 
and 

(3.) That of the electro-receptive, r", energized 
by the current. Ohm's law applied to this case 
would be: 

E 
C= r + r'+r". 

That is, the resistance of the entire circuit is 
equal to the sum of the separate resistances of its 
different parts. 

Since C= —, (1); then E=CR, (2); 
R 

andR=£ (3). 

But, since a current of one ampere is equal to 
one coulomb per second, then, in order to deter- 
mine in coulombs the quantity of electricity pass- 
ing in a given number of seconds, it is only neces- 
sary to multiply the current by the time in seconds, 
orQ = CT( 4 ). 

Hence, referring to the above equations (1), 
(2), (3) and (4); according to Ohm's law: 

(1.) The current in amperes is equal to the 
electromotive force in volts divided by the resist- 
ance inohms. 

(2.) The electromotive force in volts is equal to 
the product of the current in amperes and the 
resistance in ohms. 

(3.) The resistance in ohms is equal to the elec- 
tromotive force in volts divided by the current in 
amperes. 

(4.) The quantity of electricity in coulombs is 
equal to the current in amperes multiplied by the 
time in seconds. 

Law of Volta, or Law for Contact-Series. 

— A law for the differences of electric potential 
produced by the contact of dissimilar metals 
or other substances. 

" The difference of potential between any two 
metals is equal to the sum of the differences of 
potential between the intervening substances in 
the contact series.'''' (See Electricity, Contact. 
Series, Contact.) 

Law, Pfluger's A given tract of 

nerve is stimulated by the appearance of 
kathelectrotonusandthe disappearance of an- 
electrotonus ; not, however, by the disap- 



Law. J 



312 



Law, 



pearance of kathelectrotorms nor by (he ap- 
pearance of anelectrotonus. — (Landois and 
Stirling?) 



-At any point in 



Law, Pointing's — 

a magnetic field, or a conductor conveying 
current, the energy moves perpendicularly to 
the plane containing the lines of electric force 
or the lines of magnetic force, and the amount 
of energy crossing the unit of area of this 
plane per second is equal to the product of 
the intensities of the two forces multiplied by 
the sine of the angle between them, divided 
by 47zr. 

If E, represents the electric force of a small body- 
charged with positive electricity, and H, the 
magnetic force or forces of a smaller free unit 
north pole, and, if these forces at any point in 
the magnetic field are inclined at an angle, Q, 
then e, the flow of energy per second at this point, 
in a direction nerpendicular to the planes of E and 
His, 

E H sin. 9 
e = . 

There is, therefore, a difference in the direction 
of the flow of electricity and the flow of electric 
energy. Electricity may be conceived as passing 
through the conductor something like water 
through a pipe, but electrical energy does not 
travel in this way. Electrical energy travels 
through, the surrounding dielectric, which is 
thereby strained, and it propagates this strain 
from point to point until it reaches the conductor 
and is there dissipated. 



-The chemical 



Law, Yoltainetric — 

action produced by electrolysis in any elec- 
trolyte is proportional to the amount of elec- 
tricity which passes through the electrolyte. 

This is called the Voltametric law, because any 
vessel containing an electrolyte, and furnished 
with electrodes, so that electrolysis may take place 
on the passage of the current, and is provided 
with means for measuring the- amount of the 
electrolysis which occurs, is called a Voltameter. 
(See Voltameter. Electrolysis.) 

Laws, Ampere's, or Laws of Electro- 
Dynamic Attraction and Repulsion ■ 

Laws expressing the attractions and repul- 
sions of electric circuits on one another or 
on magnets. 



Laws, Dub's '• The magnetism ex- 
cited at any transverse section of a magnet is 
proportional to the square root of the distance 
between the given section and the near end 
of the magnet." 

" The free magnetism at any given trans- 
verse section of a magnet is proportional to 
the difference between the square root of half 
the length of the magnet and the square root 
of the distance between the given section and 
the nearest end." 

Laws, Kirclilioff's —The laws for 

branched or shunted circuits. 

These laws may be expressed as follows: 

(i.) In any number of conductors meeting at a 
point, if currents flowing to the point be considered 
as -J-, and those flowing away from it as — , the 
algebraic sum of the meeting currents will be 
zero. 

This is the same thing as saying as much elec- 
tricity must flow away from the point as flows to- 
ward it. 

(2.) In any system of closed circuits the alge- 
braic sum of the products of the currents into the 
resistances is equal to the electromotive force in 
the circuit. 

In this case all currents flowing in a certain 
direction are taken as positive, and those flowing 
in the opposite direction as negative. All elec- 
tromotive forces tending to produce currents in 
the direction of the positive current are taken as 
positive, and those tending to produce currents in 
the opposite direction, as negative. 

E 
This follows from Ohm's law; for, since C = — , 

R 
the electromotive force E = CR, and this is true, 
no matter how often the circuit is branched. 



-Laws for determining 



Laws, Lenz's — 

the directions of currents produced by electro- 
dynamic induction. 

The direction of the currents set up by electro- 
dynamic induction is always such as to oppose 
the notions by which such currents were pro- 
duced. 

Laws of Becquerel, or Laws of Mag- 
neto-Optic Rotation. — Laws for the mag- 
neto-optic rotation of the plane of polarization 
of light. (See Rotation, Magneto-Optic) 

Laws of Coulomb, or Laws of Electro- 



Law. J 



313 



[Lea, 



static and Magnetic Attractions and Re- 
pulsions. — Laws for the force of attraction 
and repulsion between charged bodies or be- 
tween magnet poles. 

The fact that the force of electrostatic attrac- 
tion or repulsion between two charges, is directly 
proportional to the product of the quantities of 
electricity of the two charges and inversely propor- 
tional to the square of the distance between them, 
is known as Cou/om^s Law. Coulomb also as- 
certained that the attractions and repulsions be- 
tween magnet poles are directly proportional to the 
product of the strength of the two poles, and in- 
versely proportional to the square of the distance 
between them. This is also called Coulomb's 
Law. 

Coulomb's law, in order to be accurate, must 
take into account the specific inductive capacity 
of the intervening medium. The correct expres- 
sion for the force between two quantities q and q', 
of electricity would be, therefore, 



F = 



q_q_ 

r*K' 



where K, is equal to the specific inductive capacity 
of the medium separating the two charges. 

In a similar manner when the force is exerted 
between two magnet poles, to be accurate, we must 
take into account the magnetic permeability of 
the medium between the two magnets. The cor- 
rect expression for the force between two magnet 
poles is, therefore, 

m m' 



F = 



r~ M 



when ju, is the magnetic permeability. 
Laws of Faraday, or Laws of Electrolysis 

Laws for the effects of electrolytic 

decomposition. (See Electrolysis) 

These laws are as follows: 

(I.) The amount of an electrolyte decomposed 
is directly proportional to the quantity of elec- 
tricity which passes through it ; or, the rate at 
which a body is electrolyzed is proportional to 
the current strength producing such electrolysis. 

(2.) If the same current be passed through dif- 
ferent electrolytes, the quantity of each ion 
evolved is proportional to its chemical equivalent. 

Laws of Joule. — Laws expressing the de- 
velopment of heat produced in a circuit by an 
electric current. 

These laws may be expressed as follows : 

(i.) The amount of heat developed in any cir- 



cuit is proportional to its resistance, providing 
the current strength is constant. 

(2. ) The amount of heat developed in any cir- 
cuit is proportional to the square of the current 
passing, providing the resistance is constant. 

(3.) The amount of heat developed in any cir- 
cuit is proportional to the time the current con- 
tinues. 

Or,H=C2Rt XO.24. 

Where H, equals the heat in small calories, C, 
equals the current in amperes, R equals the re- 
sistance in ohms, t, equals the time in seconds, 
and 0.24, the heat-units per second developed in 
a resistance of. I ohm by the passage of 1 am- 
pere. 

Lay Torpedo.— (See Torpedo, Lay) 

Layer, Crookes' —A layer, or 

stratum, of the residual atmosphere of a 
vacuous space, in which the molecules, recoil- 
ing from a heated or electrified surface, do 
not meet other molecules, but impinge on the 
walls of the vessel directly opposite such 
heated or electrified surface. 

A Crookes layer may result as the effect of 
two different causes, viz. : 

(1.) The rarefaction of the gas is such that the 
distance between the walls of the vessel and the 
heated surface is less than the mean-free-path of 
the molecules. 

(2.) The wall is so near the heated surface that 
the distance between the two is less than the ac- 
tual mean-free-path of the molecules. Under 
these last-named circumstances Crookes' layers 
may result, whatever be the density of the gas. 

Laying--Up CaMes. — (See Cables, Lay- 
ing- Up) 

Lead, Angle of The angular devia- 
tion from the normal position, which must be 
given to the collecting brushes on the com- 
mutator cylinder of a dynamo-electric ma- 
chine, in order to avoid destructive burning. 
(See Commutator, Burjiing at) 

The necessity for giving the collecting brushes 
a lead, arises both from the magnetic lag and from 
the distortion of the field of the machine by the 
magnetization of the armature current. The 
angle of leal is, therefore, equal to the sum of the 
angle of lag, and the angular distortion due to the 
magnetization produced by the armature current. 



L a.J 



314 



[Lea* 



Lead, Cable A lead containing a 

conductor formed of several stranded con- 
ductors, as distinguished from a wire lead or 
a lead containing a single conductor. 

Lead, Flexible A conductor formed 

of a number of small stranded conductors for 
the purpose of obtaining flexibility. 

Lead, Flexible Twin — A flexible 

conductor in which two parallel and sepa- 
rately insulated wires are placed. 

Lead of Brushes of Dynamo-Electric 
Machine. — The angular deviation from the 
normal position, which it is necessary to give 
the brushes on the commutator of a dynamo- 
electric machine, in order to obtain efficient 
action. (See Lead, Angle of) 

Lead Scoring Tool. — (See Tool, Scoring, 
Lead?) 

Lead Sleeve. — (See Sleeve, Lead) 

Lead, Tee. — (See Tee, Lead) 

Lead, Wire A lead consisting of a 

single conductor, as distinguished from a 
cable lead, or a lead containing a number of 
stranded conductors. 

Lead Wire.— (See Wire, Lead) 

Leading Horn of Pole Pieces of Dynamo- 
Electric Machine. — (See Horns, Leading, of 
Pole Pieces of a Dyna7no-Electric Machine) 

Leading-In Wires. — (See Wires, Lead- 
ing-In) 

Leading-Up Wires. — (See Wires, Lead- 
ing-Up) 

Leads. — The conductors in any system of 
electric distribution. 

In distribution by parallel, the conductors 
through which the current flows from the source 
are sometimes called the leads in contradis- 
tinction to those through which it returns to 
the source. 

The leads, or main conductors, in a multiple 
system of electric lighting, must maintain a con- 
stant potential at the lamp terminals. The dimen- 
sions of the leads are, therefore, so proportioned as 
to absorb as small an amount of potential as pos- 
sible. Since, in incandescent lighting, where the 
lamps are connected to the leads in multiple-arc, 
the total resistance of the lamps is comparatively 



small, the resistance of the leads must be quite 
small in order to avoid a marked drop of poten- 
tial. Comparatively large conductors must, 
therefore, be used. 

The main conductor for series circuits, such as 
for arc-lights, has in all parts the same current 
strength. Since the sum of the resistances of the 
lamps in such a circuit is quite high, a compara- 
tively high resistance in the conductor may be 
employed without a proportionally large absorp- 
tion of potential. Comparatively small conduc- 
tors can therefore be used. (See Electricity, Dis- 
tribution of, by Constant Currents. Electricity, 
Distribution of, by Alternating Currents) 

Leads, Armature, Twist in A dis- 
placement of the ends of the wires connected 
to the commutator segment, with respect to 
the position of the coils on the armature, for 
the purpose of obtaining a more convenient 
position for the diameter of commutation, 
that is, for the collecting brushes. 

Leak, Oscillatory A leak or grad- 
ual loss of electricity which takes place in 
alternately opposite directions. 

Leak, Unidirectional A gradual 

loss or leakage of electricity which takes place 
in one and the same direction. 

The term has been employed to distinguish 
such a leak from an oscillatory leak. 

Leakage Conductor. — (See Conductor, 
Leakage) 

Leakage, Electric — The gradual 

dissipation of a current due to insufficient in- 
sulation. 

Some leakage occurs under nearly all circum- 
stances. On telegraphic lines, during wet 
weather, the leakage is often so great as to inter- 
fere with the proper working of the lines. 

Leakage, Electrostatic The grad- 
ual dissipation of a charge due to insufficient 
insulation. 

The leakage of a well insulated conductor, 
placed in a high vacuum, is almost inappreciable. 
Crookes has maintained electric charges in high 
vacua for years without appreciable loss. 

Leakage, Lateral, of Lines of Magnetic 
Force The failure of lines of magnetic 



Lea.] 



315 



[Leu. 



force to pass approximately parallel to one 
another through a bar of iron or other mag- 
netizable material, when it has come to rest 
in a magnetic field in which it is free to 
move. 

The escape of the lines of magnetic force 
from the sides of a bar or other similar 
magnet, instead of from the poles at the 
end. 

When a bar of magnetizable material, sus- 
pended so as to be free to move, comes to rest in 
a magnetic field in which it is undergoing mag- 
netization, it has its greatest length parallel to 
the direction of the lines of force. If the bar is a 
long, thin, straight bar, the lines of force do not 
all pass in or come out at its ends. On the con- 
trary, many of these lines of force or induction 
pass in or come out at other points. The mag- 
netic induction is, therefore, unequal at different 
sections of the bar. In other words, the mag- 
netic flux or intensity is not constant per unit of 
all cross-sections of such bar. 

A useless dis- 



sipation of the lines of magnetic force of a 
dynamo-electric machine, or other similar 
device, by their failure to pass through the 
armature where they are needed. 

Useless dissipation of lines of magnetic 
force outside that portion of the field of a 
dynamo-electric machine through which the 
armature moves. 

Such a leakage can be detected by an instru- 
ment called a magnetophone. (See Magneto- 
phone. ) 

Magnetic leakage results in lowering the effi- 
ciency of the dynamo. (See Co-efficient, Econo- 
mic, of a Dynamo-Electric Machine. ) 

Leclanche^s Yoltaic Cell.— (See Cell, 
Voltaic, Lcclanche.) 

Leg:. — In a system of telephonic exchange, 
where a ground return is used, a single wire, 
or, where a metallic circuit is employed, two 
wires, for connecting a subscriber with the 
main switchboard, by means of which any 
subscriber may be legged or placed directly 
in circuit with two or more other parties. 

Leg of Circuit. — (See Circuit, Leg of) 

Legal Earth Quadrant.— (See Quadrant, 
Legal Earth) 



Legal Ohm. — (See Ohm, Legal) 

Legging-Key Board.— (See Board, Leg- 
ging-Key) 

Length of Spark. — (See Spark, Length 
of.) 

Lens, Achromatic A lens the 

images formed by which are free from the 
false coloration produced in other lenses by 
dispersion. 

An ordinary lens can be rendered approxi- 
mately achromatic by the use of a diaphragm. 
Achromatic lenses generally consist of the com 




C 
Fig. 342. Equal and Opposite Refracting Angles. 

bination of a double convex lens of flint glass and 
a concave lens of crown glass. 

The ray of light entering the prism ABC, 
Fig. 342, suffers dispersion (separation into pris- 
matic colors). This dispersion in the samf 
B D 




A C 

Fig. 343. Principle of Achromatism, 

medium is proportional to the angle g, between 
the incident and emergent faces, called the re- 
fracting angle. 

If, now, another prism B C D, of the same ma- 
terial, with a refracting angle g', equal to g, is 
combined with the first prism in the manner 
shown in Fig. 342, it will produce an equal but 
opposite dispersion, so that the ray of light will 
emerge at R', free from rainbow tints, but par- 
allel to its original direction. 

The variety of glass called crown glass pro- 
duces only half as great dispersion of light as the 
variety called flint glass, under the same refract- 



Len.] 



316 



[Lig. 



ing angle g. If the prism A B C, of crown glass, 
Fig. 343, whose angle g, is twice as great as the 
refracting angle g, of the prism B C D, of flint 
glass, be placed together in the manner shown, 
then the ray R, will be transmitted at R', free from 
color, but will not emerge par ailed to its original 
direction ; in other words, it suffers refraction or 
bending. Consequently such a combination can 
be used to free a pencil of light from false colora- 
tion and yet permit it to undergo refraction, 
and thus act as a lens. (See Refraction.) 

The construction of achromatic lenses is based 
on this principle. 

The crown glass is generally made with two 





Fig. 344. Piano-Convex 
Achromatic Lens. 



Fig- S4S- Achromatic 
Lens. 



convex surfaces ; the flint glass, with one con- 
cave and one plane surface, as shown in Fig. 

344. 

Sometimes both surfaces of the flint glass are 
made curved, as in Fig. 345. 

Lenz's Law. — (See Law, Lcnz's) 

Letter Box, Electric A device 

that announces the deposit of a letter in a 
box by the ringing of a bell, or by the move- 
ment of a needle or index. 

These devices generally act by the closing or 
opening of an electric circuit on the fall of the 
letter into the box. 



Leyden Jar. — (See Jar, Ley den) 
Leyden Jar Fattery. — (See Battery, Ley- 
den Jar) 

Lichtenberg's Dust Figures, — (See Fig- 
ures, Lichtenberg's Dust) 

Life Curve of Incandescent Electric 
Lamp. — (See Curve, Life, of Incandescent 
Electric Lamp) 

Life of Electric Incandescent Lamp. — 
(See Lamp, Incandescent, Life of) 

Light, Auroral The light given off 

during the prevalence of an aurora. (See 
Aurora Borealis) 

Light, Electric Light produced by 

the action of electric energy. 

Electric light is produced by electric energy in 
various ways, the most important of which are as 
follows, viz.: 

(1.) By the passage of an electric discharge 
through a gas or vapor, either in a rarefied condi- 
tion, at ordinary atmospheric pressure, or at pres- 
sures higher than that of the ordinary pressure. 
In any of these cases the gas or vapor is heated to 
incandescence by the passage of the discharge. 

(2.) By the incandescence of a solid by the 
heating power of the current, as in the incandes- 
cent lamp. 

(3.) By the incandescence of a solid by the ac- 
tion of a rapidly alternating electrostatic field, as 
in Tesla's incandescent lamp. 

(4. ) By the volatilization of a solid and the form- 
ation thereby of a voltaic arc. 

(5.) By the combination of the effects of incan- 
descence and the voltaic arc. 

The amount of light produced in proportion to 
the amount of energy expended to produce it 
is probably least in the case of light produced 
by the sparks of a Wimshurst or Holtz machine, 
or as in ( 1 ), than in any other case in which electric 
energy acts to produce luminous energy. 

Light, Electric, Pumping of (See 

Pumping of Electric Light) 

Light, Intensity of -The brilliancy 

or illuminating power of a light as measured 
by a photometer in standard candles or other 
standard units. (See Photometer. Candle, 
Standard.) 

Light, Maxwell's Electro - Magnetic 
Theory of — A hypothesis for the 



Lig.] 



317 



[Lig. 



cause of light proposed by Maxwell, based 
on the relations existing between the phe- 
nomena of light and those of electro-magnet- 
ism. 

Maxwell's electro-magnetic theory of light as- 
sumes that the phenomena of light and magnet- 
ism are each due to certain motions of the ether, 
electricity and magnetism being due to its rota- 
tions, and light to oscillations, or its to-and-fro 
motions. 

Maxwell proposed this theory to show that the 
phenomena of light, heat, electricity and magnet- 
ism could all be explained by one and the same 
cause, viz., a vibratory or oscillatory motion of 
the particles of the hypothetical ether. Maxwell 
died before completing his hypothesis, and it has 
never since been sufficiently developed to thor- 
oughly entitle it to the name of a theory. This 
theory has more recently been elaborated by 
Hertz. (See Electricity, Hertz 's Theory of Elec- 
tro-Magnetic Radiations or Waves .) 

There are, however, numerous considerations 
which render it probable that electric and mag- 
netic phonomena, like those of light and heat, 
have their origin in a vibratory or oscillatory mo- 
tion of the luminiferous ether. A few of these, 
as pointed out by Maxwell, S. P. Thompson, 
Lodge, Larden and others, are as follows: 

(i.) It is possible that the thing called elec- 
tricity is the ether itself, negative electrification 
consisting in an excess of the ether, and positive 
electrification in a deficit. (See Electricity, Sin- 
gle-Fluid Hypothesis of. ) 

(2.) It is possible that electrostatic phenomena 
consist in a strain or deformation of the ether. 
A dielectric may differ from a conductor in that 
the former may have such an attraction for the 
ether as to give it the properties of an elastic 
solid, while in the latter the ether is so free to 
move that no strain can possibly be retained by 
it. (See Dielectric. Conductor.) 

(3.) Dielectrics are transparent and conductors 
are opaque. 

There are exceptions to this in the case of vul- 
canite and many other excellent dielectrics. Nor 
should this similarity be expected to be general in 
view of the well known differences that exist be- 
tween diathermancy and transparency. 

(4.) It is possible that an electric current con- 
sists of a real motion ot translation of the ether 
through a conductor. 

(5.) It is possible that electromotive force re- 



sults from differences of ether pressures. This 
would of course follow from (4). 

(6.) The vibrations of light are propagated in 
a direction at right angles to the direction in 
which the light is moving. The magnetic field 
of a current is propagated in planes at right 
angles to the direction in which the current is 
flowing. 

(7.) It is possible that lines of electrostatic and 
magnetic force consist of chains of polarized ether 
particles. 

(8.) The velocity of propagation of light agrees 
very nearly with the velocity of propagation of 
electro-magnetic induction. (See Ratio Velocity.) 

(9. ) In certain axial crystals the difference of 
transparency in the direction of certain axes, 
corresponds with the direction in which such 
crystals conduct electricity. 

Recent investigations render it almost certain 
that light and electro-magnetic waves or radia- 
tions are one and the same, and, therefore, have 
the same velocity of propagation through free 
ether. Through fixed ether, that is, through the 
ether that exists between the molecules of differ- 
ent kinds of matter, as is well known, the velocity 
of propagation differs with different substances. 
(See Electricity, Hertz's Theory of Electro -Mag- 
netic Radiations or Waves. ) 

Light, Northern (See Aurora 

Borealis.) 

Light, Platinum-Standard — The 

light emitted by a surface of platinum one 
square centimetre in area, at its temperature 
of fusion. 

This is called the Violle Standard and is ex- 
tensively used in France. 

Light, Search, Automatic A search 

light in which a parallel or slightly diverging 
beam of light is automatically caused to 
sweep the horizon, and thus disclose the ap- 
proach of a torpedo boat or other similar 
danger. 

This is called an automatic search light because 
it may be caused to automatically sweep the hori- 
zon, instead of being manipulated by hand, as 
usual. 



Light, Search, Electric 



-An electric 



arc li?"ht placed in a focusing lamp before a 

or mirror, so as to obtain either a parallel 

beam or a slightly divergent pencil of light 



Og.] 



318 



LLig. 



for lighting the surrounding space for pur- 
poses of exploration. 

Light, Southern — (See Aurora 

Australis) 

Light, Tail —A light displayed at the 

rear end of trains in order to avoid rear colli- 
sions. (See Railroads, Block System for) 

Lighter, Cigar, Electric An ap- 
paratus for electrically lighting a cigar. 

A cigar lighter consists essentially of a wire or 
rod of refractory substance, rendered incandes- 
cent by the passage of a current obtained from a 
voltaic battery, secondary generator, or other 
electric source. 

Lighter, Electric, Argand A name 

sometimes given to an argand electric plain- 
pendant burner. (See Burner, Argand- 
Electric, Plai?i-Pe7idant) 

Lighter, Electric, Argand Talve 

A name sometimes given to an argand elec- 
tric ratchet-pendant burner. (See Burner, 
Argand-Electric, Ratchet-Pendant) 

Lighthouse Illumination, Electric 

^-(See Illwnination, Lighthouse, Electric?) 

Lighting, Arc Artificial illumina- 
tion obtained by means of an arc light. 

The term arc lighting is used in contradistinc- 
tion to incandescent lighting. In the United 
States, and, indeed, generally, a number of arc 
lights are placed in series on the line circuit, con- 
nected generally with a series dynamo. Each 
of the lamps is provided with a safety cut-out, 
which cuts out or removes a defective lamp from 
the circuit by automatically turning or switching 
the current through a shunt of low resistance. 

Lighting, Electric, by High Frequency 

Currents A system of electric lighting, 

in which rods, bars or filaments of carbon or 
other refractory substances are raised to in- 
candescence when placed in a rapidly alternat- 
ing electrostatic field. 

This system of electric lighting was invented 
by Nikola Tesla. Its general principles will be 
understood from an inspection of Fig. 346. 

G, is a dynamo producing alternating .- i-r^nts 
of comparatively low potential. A portion of its 
current P, acting as the primary of an induction 
coil, induces alternating currents of high 



potential in the secondary circuit S, which, 
charging the condenser C, is disruptively dis- 
charged into the circuit A, provided with an air 
gap at A' through P'. The inductive action 
of P', on S', produces oscillatory currents o£ 

r ^y- 



MMMM 

WM/mvwmm 



s' 







Fig. 346. 



Testa's High Frequency Currents 
System of Lighting. 



enormous frequency and potential in the second- 
ary circuits connected therewith. In the ap- 
paratus shown in Fig. 346, two incandescent 
electric lamps are connected with the secondary- 
circuit, one with a single straight filament, and 
the other with a ball conductor. The other 
terminal of S', is connected to the walls of the 
room to be lighted. (See Lamp, Incandescent, 
Straight Filament. Lamp, Electric, Incandes- 
cent Ball.) 

Lighting, Electric, Central Station 

— The lighting of a number of houses or other 
buildings from a single station, centrally lo- 
cated. 

Central station lighting is distinguished from iso- 
lated lighting by the fact that a number of sepa- 
rate buildings, houses or areas, are lighted by the 
current produced at a single station, centrally 
located, instead of from a number of separate 
electric sources located in each of the houses, etc., 
to be lighted. (See Electricity, Distribution of.) 

Lighting, Electric Gas Igniting- 

gas jets by means of electric discharges. 

Electric sparks are caused to pass through a 
jet of escaping gas, and thus to light it. These 
sparks are obtained from a spark-coil, i. e., a 
coil of insulated wire connected in series with 
the circuit so as to produce an extra current on 
the sudden breaking of the circuit, the discharge 
of which produces a spark capable of igniting the 
gas. In cases where a number of burners are to 
be simultaneously lighted the sparks required for 



iteJ 



319 



[Lis 



lighting the gas are obtained from the secondary 
of an induction coil. (See Burner, Automatic 
Electric.) 

Lighting, Electric, Isolated ■ A 

system of electric lighting where a separate 
electric source is placed in each house or 
area to be lighted, as distinguished from the 
central station lighting, where electric sources 
are provided for the production of the current 
required for an entire neighborhood. 

Lighting, Electric, Long-Arc System of 

-A system of electric lighting in which 



long arcs are maintained between the carbon 
electrodes. 

Lighting, Electric, Short-Arc System 

-A system of electric lighting in which 



short voltaic arcs are maintained between the 
carbon electrodes. 

Systems of short arcs require an electromotive 
force of about 25 volts, which is about one-half 
that employed in long arcs. To develop an 
equal amount of heat energy in a short arc as in 
a long arc, therefore, requires that the current be 
of double strength. 

The greater part of the light of a voltaic arc 
is given off from a tiny crater, which is formed in 
the end of the positive carbon. In the short arc 
system the crater lies so near the negative carbon 
that much of its light is necessarily obscured, and 
troublesome shadows are sometimes produced. 
The long-arc system avoids these difficulties. 

Lightning. — The spark or bolt that results 
from the disruptive discharge of a cloud to 
the earth, or to a neighboring cloud. (See 
Electricity, Atmospheric. Kite, Franklin's?) 

Lightning Arrester.— (See Arrester, 
Lightning?) 

Lightning, Back-Stroke of An 

electric discharge, caused by an induced 
charge, which occurs after the direct dis- 
charge of a lightning flash. 

The shock is not caused by the lightning flash 
itself, but most probably by a charge which is in- 
duce 1 in neighboring conductors by the discharge. 
A similar effect may be noticed by standing near 
the conductor of a powerful electric machine, 
when shocks are felt at every di-chirge. 

The back-stroke has been ascribed by many to 



the oscillations by which a disruptive discharge 
is effected. (See Discharge, Oscillating.) 

The effects of the return shock are sometimes 
quite severe. They are often experienced by 
sensitive people, on the occurrence ot a lightning 
discharge, at a considerable distance from the 
place where the discharge occurred. 

In some instances, the return stroke has been 
sufficiently intense to cause death. In general, 
however, its effects are much less severe than 
those of the direct lightning discharge. 

Lightning, Ball - - A name 
times given to 



some- 
globular lightning. (See 



Lightning, Globular?) 

Lightning, Chain A variety of 

lightning flash in which the discharge takes 
a rippling path, somewhat resembling a 
chain. 

Lightning Conductor.— (See Rod, Light- 
ning?) 

Lightning, Forked A variety of 

lightning flash, in which the discharge, on 
nearing the earth or other object, divides into 
two or more branches. 

Lightning, Globular A rare form 

of lightning, in which a globe of fire appears, 
which quietly floats for a while in the air ; and 
then explodes with great violence. 

The exact cause of globular lightning is un- 
known. Phenomena allied to it, however, have 
been observed by Plante during the series dis- 
charge of his rheostatic machine. Similar pheno- 
mena are sometimes, though rarely, observed 
during the discharge of a powerful Leyden battery. 
Sir Wm. Thomson ascribes the effect to an optical 
illusion due to the persistence of the visual impres- 
sion of a bright flash. This, however, would rot 
account for the explosion which almost invariably 
attends globular lightning. 

Lightning Guard.— (See Guard, Light- 
ning?) 

Lightning, Heat A variety of 

lightning flash in which the discharge lights 
up the surfaces of the neighboring clouds. 

Sheet lightning is unaccompanied by thunder. 
It may be regarded as a brush discharge from one 
cloud to another. 

Heat lightning is a variety of sheet lightning. 
(See Lightning, Sheet.) 



Lg.J 



320 



[Lin* 



Lightning" Jar. — (See Jar, Lightning?) 
Lightning, Return-Stroke of A 

term sometimes applied to the back-stroke of 
lightning. (See Lightning, Back-Stroke of) 

Lightning Rod. — (See Rod, Lightning') 

Lightning Rod for Ships.— (See Rod, 
Lightning, for Ships.) 

Lightning, Sheet A variety of 

lightning flash unaccompanied by any thunder 
audible to the observer, in which the entire 
surfaces of the clouds are illumined. 

The cause of sheet lightning has been ascribed 
to reflection from clouds of lightning flashes 
that occur too far below the horizon either to 
permit them to be directly seen, or the thunder 
to be heard. 

If a Geissler tube, which contains several con- 
centric tubes, be charged by a Holtz machine, 
and then touched at different parts by the hands, 
a succession of luminous discharges will be seen 
in the dark, that bear a remarkable resemblance 
to the flashes of heat or sheet lightning. 

Lightning Stroke. — (See Stroke, Light- 
ning.) 
Lightning Stroke, Back or Return 

— (See Stroke, Lightning, Back or Return.) 

Lightning, Summer A name some- 
times given to heat lightning. (See Light- 
ning, Heat) 

Lightning, Volcanic The lightning 

discharges that attend most volcanic erup- 
tions. 

Volcanic lightning is possibly sometimes due to 
the friction of volcanic dust particles against one 
another, or against the air, but is more probably 
caused by the sudden condensation of the water 
vapor that is generally disengaged during volcanic 
eruptions. 

Lightning, Zigzag The common- 
est variety of lightning flashes, in which the 
discharge apparently assumes a forked zig- 
zag, or even a chain-shaped path. 

This form is seen in the discharge of a Holtz 
machine, or of a Ruhmkorff Induction Coil. 

Photographic pictures of such lightning dis- 
charges appear to show that these discharges are 
in reality zigzag curves, rather than sharp angu- 
lar zigzacs. 



Limiting Stop. — (See Stop, Limiting) 

Limb, Rheoscopic A term some- 
times applied to a sensitive nerve muscle prep- 
aration, employed to detect the presence of 
an electric current. (See Frog, Galvano- 
scope.) 

Line. — A wire or other conductor connect- 
ing any two points or stations. 

Line, Aclinic A line connecting 

places on the earth's surface which have no 
magnetic inclination. 

The magnetic equator of the earth. (See 
Equator, Magnetic) 

Line Adjuster. — An instrument invented 
by Delany for overcoming the effects of leak- 
age on the adjustment of the relays in a way 
line. 

When any key is opened, the line circuit is 
simultaneously broken at both ends so that there 
is a moment of no current, which causes all the 
relays to respond. 

Line, Aerial An air line as dis- 
tinguished from an underground conductor. 

Line, Agonic A line connecting 

places on the earth's surface where the mag- 
netic needle has no declination, or where it 
points to the true geographical north. (See 
Agonic) 

Line, Artificial A line so made up 

by condensers and resistance coils as to have 
the same inductive effects on charging or dis- 
charging as an actual telegraph line. 

In duplex telegraphy by the differential method, 
the artificial line used must have its capacity 
balanced against that of the line, so as to avoid 
the effects of self-induction, and other effects pro- 
duced by charging and discharging. 

Line, Capacity of ■ — The ability of a 

line or cable to act like a condenser, and 
therefore like it to possess a capacity. (See 
Cable, Capacity cf) 
Line Circuit. — (See Circuit, Line) 

Line Circuit, Telegraphic (See 

Circuit, Line, Telegraphic) 



Line, Neutral, of a Magnet 



-A line 



joining the neutral points of a magnet or 



Lin.] 



321 



[Lin. 



points approximately midway between the 
poles. 

This is sometimes called the equator of the 
magnet. 

The neutral point is the point where the lines 
of force outside the magnet extend parallel to the 
surface of the magnet. — {Her big.) 

Line, Neutral, of Commutator Cylinder 

A line on the commutator cylinder of 

a dynamo-electric machine connecting the 
neutral points, or the points of maximum 
positive and negative difference of potential. 
(See Machine, Dynamo-Electric) 

Line of Least Sparking.— (See Sparking ; 
Least Line of) 

Line, Single- Wire A term some- 
times used for a solid-wire conductor. (See 
Line, Solid.) 

Line, Solid — A line formed of a 

single conductor, as distinguished from a line 
formed of several conductors or by a stranded 
cable. 

Line, Stranded A line formed of 

several strands or separate conductors twisted 
into one. 

Line, Telegraphic, Telephonic, etc. 

— The conducting circuit provided for the 
transmission of the electric impulses or cur- 
rents employed in any system of electric 
transmission. 

Line, Telpher The conducting line 

used in a system of telpherage. (See Tel- 
pherage) 

Line, Through A line extending 

between two terminal points, as distinguished 
from a line containing way stations. 

Line, Trunk In a system of tele- 
phonic communication any line connecting 
distant stations and used by a number of 
subscribers at each end for purposes of inter- 
communication. 

Line, Way A line communicating 

with way stations. 

Line Wire. — (See Wire, Line) 

Lineman. — One who puts up and repairs 
line circuits and attends to the devices con- 
nected therewith. 



In a system of electric lighting the lineman 
attends to carboning the lamps, cleaning the 
lamp rods, and, generally, to the minor details of 
the lines, insulators and the electro-receptive de- 
vices placed on the line. 

Lines, Halleyan A term sometimes 

applied to the isogonal lines. 

The isogonal lines are sometimes called the 
Halleyan lines, from Halley, who published the 
first chart of such lines in the year 1701. 

Lines, Isobaric Lines connecting 

places on the earth's surface which simulta- 
neously have the same barometric pressure. 

The isobaric lines are sometimes called isobars. 

Lines, Isoclinic Lines connecting 

places that have the same angle of magnetic 
dip or inclination. (See Dip, Magnetic.) 

Lines, Isodynamic Lines connect- 
ing places which have the same total mag- 
netic intensity. 

The magnetic intensity of a place is determined 
by the number of oscillations that a small mag- 
netic needle, moved from its position of rest in 
the magnetic meridian of any place, makes in a 
given time. This method is similar to that em- 
ployed for determining the intensity of gravity at 
any place by observing the number of oscillations 
that a pendulum of a given length makes in a 
given time at that place. If, for example, a mag- 
netic needle at one place makes 211 oscillations in 
ten minutes, and 245 in the same time at another 
place, then the relative intensities of magnetism 
at these places are as the squares of those num- 
bers, or as 44,521 : 60,025, or as I •' I -348. 

Lines, Isogonal Lines connecting 

places that have the same magnetic declina- 
tion. (See Declination.) 

Lines, Isogonic A term sometimes 

used for isogonal lines. (See Lines, Isogonal) 

Lines, Isothermal Lines connect- 
ing points or places which have the same 
mean temperature. 

Lines, Kapp A term proposed by 

Mr. Gisbert Kapp for a unit of lines of mag- 
netic force. 

One Kapp line = 6,000 C. G. S. magnetic lines. 

Since there are 6.4514 square centimetres in a 

square inch, 1 Kapp line per square inch 

6,000 



M5H 



930 C. G. S. lines per square cm. 



Lin.J 



322 



[Loc. 



The total number of Kapp lines passing through 
a magnet and air space is equal to the ampere 
turns divided by the total magnetic reluctance in 
the magnetic circuit. — {Urquhart.) 

Lines of Electric Displacement. — (See 
Displacement, Electric, Lines of) 

Lines of Electrostatic Force.-- (See Force, 
Electrostatic, Lines of.) 

Lines of Force, Cutting (See Force, 

Lines of, Cutting) 

Lines of Force, Direction of (See 

Force, Lines of, Direction of) 

Lines of Inductive Action. — (See Action, 
Inductive, Lines of) 

Lines of Magnetic Force. — (See Force, 
Magnetic, Lines of) 

Lines of Magnetic Force, Conducting 

Power for — (See Force, Magnetic, 

Lines of. Conducting Power for) 

Lines of Magnetic Induction. — (See In- 
duction, Magnetic, Lines of.) 

Lines, Overhead A term applied 

to telegraph, telephone and electric light or 
power lines that run overhead, in contradis- 
tinction to similar lines placed underground. 

Lines, Vortex-Stream Lines ex- 
tending in the direction in which the particles 
of a fluid are moving. 

A vortex stream is supposed to be composed of 
a number of vortex -stream lines. 

Linked Magnetic and Electric Chain. — 

(See Chain, Linked Magnetic and Electric.) 

Links, Fuse — Strips or plates of 

fusible metal in the form of links, employed 
for safety fuses for incandescent or other 
circuits. 

Liquid, Bright Dipping A liquid 

used in electro-plating for dipping articles 
preparatory to electro-plating, so as to insure 
a bright plating deposit on them when after- 
wards subjected to the plating process. 

A bright dipping liquid is prepared by the ad- 
dition of I volume of common table salt to a 
mixture of loo volumes each of sulphuric and 
nitric acids. For small objects or articles of 
copper, or other readily corroded metals, the 



above solution is diluted by the addition of one. 
eighth its volume of water. 

Liquid, Electropoion A battery 

liquid consisting of i pound of bichromate 
of potash dissolved in 10 pounds of water, to 
which 7.\ pounds of commercial sulphuric 
acid has been gradually added. 

This liquid is employed with the carbon-zinc 
cell or the bichromate of potash cell. 

Liquid, Exciting, of Voltaic Cell 

The electrolyte or liquid in a voltaic cell, 
which acts on the positive plate. 



-{See Alarm, Water 
Load. — (See Load, 



Liquid Level Alarm.- 

or Liquid Level) 
Liquid Resistance 

Liquid Resistance) 

Liquid, Stripping A liquid em- 
ployed to remove a coating of one metal 
from the surface of another, without affecting 
the other metal. 

The character of the stripping liquid used will 
depend on the kind of metal to be removed, and 
whether the stripping is to be accomplished by 
solution effected by chemical action, or by electro- 
lytic action. 

Liquid, Specific Resistance of 

(See Resistance, Specific, of Liquid) 

Liquor, Spent Any liquor, such as 

that in the acid or other baths used in electro- 
plating, that has become weakened by use. 

Listening Cam. — (See Cam, Listening) 

Load, Liquid Resistance An artk 

ficial load for a dynamo-electric machine, 
consisting of a mass of liquid interposed be- 
tween electrodes. 

A liquid is generally rendered better conduct- 
ing by the addition of a small quantity of soluble 
salt, such, for example, as sulphate of soda. 

Local Action of Dynamo-Electric Ma- 
chine. — (See Action, Local, of Dynamo- 
Electric Mac hi tie) 

Local Action of Voltaic Cell.— (See Ac- 
tion, Local, of Voltaic Cell.) 

Local Battery. — (See Battery, Local) 

Local Battery Circuit. — (See Circuity 
Local-Battery) 



Xoc] 



323 



[Loo. 



Local Currents. — (See Currents, Local) 

Local Faradization. — (See Faradization, 
Local) 

Local Galvanization. — (See Galvaniza- 
tion, Local) 

Localization of Faults. — (See Faults, 
Localization of) 

— A lock that is au- 



Lodge's Standard Toltaic Cell. —(See 
Cell, Voltaic, Standard, Lodge s) 



Log", Electric 



-An electric device 



Lock, Electric — 

tomatically unlocked by the aid of electricity. 

The electric lock is so arranged that the action 
of a push button at a distance unlocks the door. 
A speaking tube communicates with the house, 
and the pressing of a push button on any floor of 
the house unlocks the door. The mere shutting 
of the door locks it. 

A form of electric lock is shown in Fig. 347. 




Fig. 347. Electric Lock. 

Locomotive, Electric 



— A railway 
engine whose motive power is electricity. 
(See Railroads, Electric) 

Locomotive Head Light, Electric 

(See Head Light, Locomotive) 

Lodestone. — A name formerly applied to 
an ore of iron (magnetic iron ore), that natu- 
rally possesses the power of attracting pieces 
of iron to it. 

Lodestone, or magnetic iron ore, must be re- 
garded as a magnetizable substance that has be- 
come permanently magnetic from its situation in 
the earth's magnetic field. Such beds of ore 
concentrate the lines of the earth's magnetic field 
on them, and thus become magnetic. 



for measuring the speed of a vessel. 

A log, operated by the rotation of a wheel, is 
caused to register the number of its rotations by a 
step-by-step recording apparatus operated by 
breaks in the circuit, made during the rotation 
of the wheel, at any given number of turns, say 
100, or some other convenient multiple. Such a 
log may be kept constantly in the water, and ob- 
served when required, or it can be caused to 
make a permanent record of its actual speed at 
any time during the entire run. 

Logarithm. — The exponent of the power 
to which it is necessary to raise a fixed num- 
ber, in order to produce a given number. 

A table of logarithms enables the operations of 
multiplication, division, the raising of powers, 
and the extraction of roots, to be readily per- 
formed by simple addition, subtraction, multi- 
plication or division, respectively. When thor- 
oughly understood, logarithms greatly reduce the 
labor of mathematical calculations. For the man- 
ner in which they are used, the student is referred 
to any standard work on mathematics. 

Logarithmic Curve. — (See Curve, Loga- 
rithmic) 

Long-Coil Magnet. — (See Magnet, Long- 
Coil) 

Long-Core Electro-Magnet. — (See Mag- 
net, Electro, Long-Core) 

Long-Shunt Compound-Wound Dynamo- 
Electric Machine. — (See Machine, Dy?ia- 
mo-Electric, Compound- Wound, L o ng- 
Shunt) 

Longitude, Electric Determination of 

The determination of the longitude of 

a place, by differences in time between it and 
a place on the prime meridian, as simultane- 
ously determined telegraphically. 

In determinations of this character allowance 
must be made for the retarding effects of long 
telegraphic lines, or cables. 

Loom, Electric A device by means 

of which Jacquard cards in the ordinary loom 
are replaced by a simple perforated metal 
plate, the perforations in which correspond 
to those in the Jacquard card. 



Loo.] 



zu 



[Lux,. 



The necessary movements are effected by 
means of electro-magnets. 

Loop Break. — A device for introducing a 
loop in a break made at any part of a circuit. 

The rigidity of the line wire, between the points 
of attachment of the loop introduced, is main- 
tained by means of some inflexible non-conducting 
material inserted in the break. 

Loop Circuit. — (See Circuit, Loop) 



An inclined loop placed 



Loop, Drip — 

where the outside conductors enter a build- 
ing. 

The inclination is upwards towards the point 
of entrance to the building. This device of 
a drip loop is adopted for the purpose of prevent- 
ing the rain water from flowing along the inclined 
wire into the building. This is effected by making 
the wire incline from the building, thus throwing 
the drainage from the building. 

Loop, Electric A portion of a main 

circuit consisting of a wire going out from 
one side of a break in the main circuit and 
returning to the other side of the break. 

Loops are employed for the purpose of con- 
necting a branch telegraph office with the main 
line; for placing one or more electric arc lamps 
on the main line circuit; for connecting a mes- 
senger call or telephone circuit with, a mainline; 
and for numerous similar purposes. 

Loops of Force. — (See Force, Loops of.) 

Loops of Mutual Induction. — (See Induc- 
tion, Mutual, Loops of.) 

Low-Resistance Mag-net. — (See Magnet, 
Low-Resistance) 

Low-Tension Electric Fuse. — (See Fuse, 
Electric, Low- Tension) 

Loxodrograph. — An apparatus for electri- 
cally recording on paper the actual course of 
a ship by the combined action of magnetism 
and photography. 

Luces. — Plural of lux. (See Lux) 

Luminescence. — A limited power of emit- 
ting light, possessed by certain bodies which 
have previously acquired potential energy by 
exposure to light or radiant energy. 

The term luminescence was proposed by E. 
Wiedemann to cover the case of the emission of 



light under circumstances differing from the emis- 
sion or radiation of light by incandescence. Lu- 
minescence applies to the case of a radiation, 
generally selective in character, that is apparently 
due to effects allied to, or the same as, those of 
fluorescence and phosphorescence. For example, 
magnesium oxide or zinc oxide, when heated 
above a certain critical temperature, radiates far 
more light than equally hot carbon. 

The spectrum of such luminescent light is espe- 
cially rich in certain wave lengths. The ability 
of the substance to continue to furnish this extra 
light is, however, limited. After a comparatively 
short time, the additional light, or selective radia- 
tion, disappears. The luminescent light is appa- 
rently due to molecular potential energy stored in 
the substance during its exposure to light. Lumi- 
nescence may be developed in bodies in the fol- 
lowing manner, viz. : 

(i.) By heat. 

(2.) By chemical action. 

(3.) By friction. 

(4.) By exposure to the sun, or by actual impact 
of light waves. 

(5.) By electricity. 

(6.) By vital forces, as in the fire fly, or the 
glow worm. 

Luminescence, Rejuvenation of 

Reimparting by exposure to light, or any other 
suitable means, the power of luminescence to 
a substance after it has lost this power. 

Luminous Absorption. — (See Absorption, 
Luminous) 

Lunar Inequality of Earth's Magnetic 
Variation or Inclination. — (See Inequality, 
Lunar, of Earth 's Magnetic Variation or 
Inclination) 

Lunar Inequality of Earth's Magnetism. 

— (See Inequality , Lunar , of Earth 's Mag- 
netism) 

Lux. — A name proposed by Preece for the 
unit of intensity of illumination. 

The illumination given by a standard 
candle at the distance of 12.7 inches. 

The illumination given by 1 carcel at the 
distance of 1 metre. 

The illumination given by a lamp of 10,000 
candles at 105.8 feet. (See Illumination, 
Unit of) 



MJ 



325 



[Mac* 



M 



M. — A contraction sometimes used to ex- 
press a gaseous pressure of the .000001 of 
an atmosphere. 

1,000,000 M. equals 760 mm. of mercury or I 
atmosphere of pressure. 

A vessel containing air, which has been ex- 
hausted to the .000001 of its pressure at 760 
mm., or one atmosphere, has a pressure or ten- 
sion of 1 M. 

This contraction is used by Crookes in his re- 
searches on the properties of radiant matter. (See 
Matter, Radiant, or Ultra Gaseous. ) 

ju. — A contraction used in mathematical 
writings for magnetic permeability, or the 
specific conductibility of any substance for 
lines of magnetic force. 

mm. — A contraction for millimetre. (See 
Weights, French System of.) 

M. P. H. — A contraction sometimes used in 
railroad work to indicate miles per hour. 

Machine, Armstrong's Hydro-Electric 

A machine for the development of 

electricity by the friction of a jet of steam 
passing over a water surface. 

Steam generated in a suitably insulated boiler, 




Fig. 348. Armstrong's Hydro-Electric Machine. 

Fig. 348, is allowed to escape through a tortuous 
nozzle, from a series of apertures opposite a 
pointed comb, attached to an insulated conductor. 



The cooling of the steam during its passage 
through a flat box, termed the coolin° box, con- 
nected with the nozzles, causes a partial condensa- 
tion, so that the box always contains a small 
quantity of water. 

The friction of the drops of water against the 
orifice, and, possibly, their friction against the 
water surface itself, are the cause of the electricity 
produced. 

A conductor connected with the pointed comb 
furnishes positive electricity. The boiler fur- 
nishes negative electricity. The hydro-electric 
machine is not a very economical source of elec- 
tricity, and is only employed for experimental 
purposes. It was discovered accidentally through 
a shock given to an engineer, who placed his 
hand in a jet of steam escaping from a leaking 
boiler he was endeavoring to mend. The causes 
were first studied by Sir Wm. Armstrong, who, 
in 1840, devised the apparatus just described. 

Machine, Dynamo-Electric — A 

machine for the conversion of mechanical 
energy into electrical energy, by means of 
magneto-electric induction. 

The term is also applied to a machine by 
means of which electrical energy is converted 
into mechanical energy by means of magneto- 
electric induction. Machines of the latter class are 
generally called motors, those of the former, 
generators. 

Prof. S. P. Thompson defines a dynamo-elec- 
tric machine as follows, viz.: "A machine for 
converting energy in the form of mechanical 
power into energy in the form of electric currents, 
or vice versa, by the operation of setting con- 
ductors (usually in the form of coils of copper 
wire) to rotate in a magnetic field, or by vary, 
ing a magnetic field in the presence of conduc- 
tors." 

The term dynamo was first applied to such 
machines, because in the form in which this 
machine first appeared, viz.: the series-wound 
machine, it was self- exciting, or required no ex- 
citement other than what it received by the rota- 
tion of its armature in the field of its magnets, 
or, indeed, in the field of the earth. (See Machine, 
Dynamo- Electric, Reaction Principle of. ) 

A dynamo- electric generator, or a dynamo-elec- 



Mac] 



32( 



[Mac. 



trie machine proper, consists of the following 
parts, viz.: 

(i.) The revolving portion, usually the arma- 
ture, in which the electromotive force is developed, 
which produces the current. 

It must be borne in mind that it is not current, 
but difference of electric potential, ox electromotive 
force, that is developed by any electric source 
from which a current is obtained. For ease of 
reference, however, we will speak of an electric 
current as being generated by the armature, or by 
the source. No ambiguity will be introduced if 
the student bears the above in mind. 

(2.) The field magnets, which produce the field 
in which the armature revolve?. 

(3.) hi pole pieces, or free terminals of the field 
magnets. 

(4.) The conwiutator, by which the currents de- 
veloped in the armature are caused to flow in 
one and the same direction. la alternating 
machines, and in some continuous current dynamos 
this part is called the collector, and does not rec- 
tify the currents. 

(5.) The collecting brushes, that rest on the 
commutator cylinder and take off the current 
generated in the armature. 

Machine, Dynamo-Electric, Alternating- 
Current A dynamo-electric machine 

in which alternating currents are produced. 

The field magnets may be either permanent 
magnets or electro-magneis. When electro-mag- 
nets are used, their coils may be separately ex- 
cited by another machine whose current is con- 
tinuous; or, they may be excited by the commuted 
current of a separate coil on the armature; or, they 
may be partly excited by commuted currents and 
partly by commuted currents from a transformer, 
placed in the main circuit of the dynamo. 

Machine, Dynamo-Electric, Armatnre of 

(See Armature, Dynamo-Electric 

Machine?) 

Machine, Dynamo-Electric, Bed-Piece of 

• The frame or base on which a dynamo 

is supported. 

The bed-piece is sometimes called the dynamo 
frame or base. 

Machine, Dynamo-Electric, Bi-Polar 

— A dynamo-electric machine, the armature 
of which rotates in a field formed by two 
magnet poles, as distinguished from a ma- 



chine the armature of which rotates in a field 
formed by more than two magnet poles. 

A dynamo-electric machine whose armature 
rotates in the field formed by more than two 
poles is called a multi-polar machine. (See Ma- 
chine, Dynamo -Electric, Multi-Polar.) 

Machine, Dynamo-Electric, Carcass of 

A term sometimes used in place of 

the field magnet frame of a dynamo-electric 
machine. (See Machine, Dynamo-Electric, 
Fra7iie of.) 

The term, field magnet frame, would appear 
to be the preferable term. The term, however, 
is used in France, and is derived from the 
French word for skeleton. 

Machine, Dynamo-Electric, Closed-Coil 

A dynamo-electric machine, the 

armature coils of which are grouped in sec- 
tions, communicating with successive bars of 
a collector, so as to be connected continu- 
ously together in a closed circuit. 

The Gramme dynamo and most continuous- 
current dynamos are closed-coil dynamos. 

Machine, Dynamo-Electric, Closed-Coil 

Disc A closed-coil dynamo-electric 

machine, the armature core of which is disc- 
shaped. 

Machine, Dynamo-Electric, Closed-Coil 

Drum A closed-coil dynamo-electric 

machine, the armature core of which is 
drum-shaped. 

Machine, Dynamo-Electric, Closed-Coil 

Ring* A closed-coil dynamo-electric 

machine, the armature core of which is ring- 
shaped. 

Machine, Dynamo-Electric, Collectors 

(See Collectors of Dynamo-Electric 

Machines.) 

Machine, Dynamo-Electric, Compound 
Winding of (See Winding, Corn- 
found, of Dynamo-Electric Machine?) 

Machine, Dynamo-Electric, Compound- 
Wound Machines whose field mag- 
nets are excited by more than one circuit of 
coils, or by more than a single electric 
source. 

The object of compound winding is to make 



Mac] 



327 



[Mac. 



the dynamo self-regulating under changes in its 
working load. A shunt-wound dynamo renders 
both series and multiple circuits approximately 
constant as regards their working. Multiple cir- 
cuits, however, require great constancy of poten- 
tial, and for this purpose the compounding of the 
dynamos is necessary. 

In the compound dynamo, the shunt coils are 
superposed on the series coils, or are used in con- 
nection with them. The'shunt coils consist of a 
much greater number of convolutions of fine wire 
than the series coils, which are of coarse wire. 

Separate excitation is sometimes compounded 
either with series or with shunt field magnet 
coils. 

Compound dynamos are of two classes, viz. : 

(i.) Those designed to produce a constant 
potential, and 

(2.) Those designed to produce a constant cur- 
rent. 

For Constant Potential : 

In the long-shunt compound-wound dynamo, 
the terminals of the shunt coil are connected with 
the binding posts of the machine. As the cur- 
rent leaves the armature it has two paths to take : 
one, the thick series coils, to the external circuit, 
and the other the finer and longer shunt coils. 
The resistance of the shunt coils is greater than 
that of the armature. Current variations in the 
armature will, therefore, produce no appreciable 
efLct on the magnetizing power of the shunt, 
which acts as a nearly uniform exciter of the field. 

In a shunt-wound dynamo connected to a 
multiple circuit, the introduction of an additional 
number of receptive devices into the circuit re- 
quires more current, and this would tend to cause 
a slight drop in the potential. The object of the 
series coils is to prevent this drop. The series 
coils, therefore, act as compensators. If the 
coils are too powerful the compensation will 
have the effect of increasing the potential. 

The combination of a series and separately ex- 
cited machine is shown in Fig. 351. The field is 
in series with the armature, but has also an ad- 
ditional and separate excitation. 

The combination of a series and shunt machine 
insures the excitation of the field both by the 
main and by the shunted current. Such a com- 
bination is shown in Fig. 353. 

For Constant Current : 

The combination of shunt and separately ex- 
cited machines is shown in Fig. 356. In this 
machine the field is excited by means of a shunt 



to the external circuit, and by a current produced 
by a separate source. 

The combination of a series and magneto ma- 
chine is shown in Fig. 352. This, also, is 
designed to give a constant current. 

Machine, Dynamo-Electric, Compound- 
Wound, Long-Shunt A compound- 
wound dynamo- electric machine, in which 
the shunt-field magnet coils form a shunt to 
the binding posts of the machine. 

In the short-shunt compound-wound dynamo - 
electric machine, the ends of the shunt coil are 
connected to the brushes of the machine. 

Machine, Dynamo-Electric, Compound- 
Wound, Short-Shunt A compound- 
wound dynamo-electric machine in which the 
shunt-field magnet coils form a shunt to the 
armature only, as distinguished from the 
armature and series coils combined. 

In the short-shunt dynamo-electric machine, 
the ends of the shunt coil are connected to the 
brushes of the machine, and not to the binding 
posts of the machine, or to the external circuit, as 
in the long-shunt machine. 

Machine, Dynamo-Electric, Continuous- 
Current A dynamo-electric machine, 

the current of which is commuted so as to 
flow in one and the same direction, as dis- 
tinguished from an alternating dynamo. 

Machine, Dynamo-Electric, Double-Mag- 
net A term sometimes applied to a 

dynamo-electric machine, the field magnets 
of which have two consequent poles. 

Machine, Dynamo-Electric, Economic 
Co-efficient of A name formerly ap- 
plied to the efficiency of a dynamo-electric 
machine. (See Machine, Dynamo-Electric, 
Efficiency of.) 

Machine, Dynamo-Electric, Efficiency 

of The ratio between the electric 

energy or the electrical horse-power produced 
by a dynamo, and the mechanical energy or 
horse-power expended in driving the dynamo. 

The Efficiency may be the Commercial Effi- 
ciency, which is the useful or available energy in 
the external circuit divided by the total mechan- 
ical energy ; or it may be the Electrical Efficiency, 
which is the available electric energy divided by 
the total electric energy. 



Mac. 



328 



[Mac. 



The Efficiency of Conversion is the total elec- 
trical energy developed, divided by the total 
mechanical energy applied. 

If M, equals the mechanical energy, 

W, the useful or available electrical energy, 

and 
w, the electrical energy absorbed by the ma- 
chine, and 
m, the Stray Power, or the power lost in 
friction, eddy currents, air friction, etc. 
Then, since 
M = W + w + m, 
Commercial Efficiency . 



W 



W 



M 



W + w + m 



Electrical Efficiency.. 
Efficiency of Conversion =. 



W 



w 

W4 



w 



M W-f w -j- m 
Machine, Dynamo-Electric, Flashing of 

A name given to long flashing sparks 

at the commutator, due to the short cir- 
cuiting of the external circuit at the com- 
mutator, by arcing over the successive com- 
mutator insulating strips. 

Machine, Dynamo-Electric, Frame of 
The bed-piece that supports a dyna- 
mo-electric machine. 

The frame is sometimes called the dynamo bed- 
piece. 

The word frame is sometimes applied to the 
field magnet cores and yokes. 

Machine, Dynamo-Electric, Local Action 

of ■ — (See Action, Local, of Dynamo- 
Electric Machine?) 

Machine, Dynamo-Electric, Mouse-Mill, 
Sir Win. Thomson's A dynamo- 
electric machine designed by Sir Wm. 
Thomson, named from the resemblance of 
its armature to a mouse mill. 

The armature conductor of this dynamo con- 
sists of parallel bars of copper, arranged on a 
hollow cylinder, like the bars on a mouse mill. 

Machine, Dynamo-Electric, Multipolar 

— A dynamo-electric machine, the 

armature of which revolves in a field formed 
by more than a single pair of poles. 

This form is usually adopted for large machines 
as being more economical. 

Fig. 349 shows a multipolar dynamo with four 
poles. 



Machine, Dynamo-Electric, Open-Coil 

A dynamo-electric machine, the 

armature coils of which, though connected to 




Fig. 34Q. Multipolar Dynamo with Four Poles. 

the successive bars of the commutator, are not 
connected continuously in a closed circuit. 

The Brush and the Thomson-Houston arc dy- 
namos are open-coil machines. 

Machine, Dynamo-Electric, Open- Coil 

Disc An open-coil dynamo-electric 

machine, the armature of which is disc- 
shaped. 

Machine, Dynamo-Electric, Open-Coil 

Drum An open-coil dynamo-electric 

machine, the armature core of which is drum- 
shaped. 

Machine, Dynamo-Electric, Open-Coil 

Ring* An open-coil dynamo-electric 

machine, the armature core of which is ring- 
shaped. 

Machine, Dynamo-Electric, Output of 

The electric power of the current gen- 
erated by a dynamo-electric machine ex- 
pressed in volt-amperes, watts or kilo-watts. 
S. P. Thompson suggests that dynamo- electric 
machines be rated as to their practical safe ca- 
pacity in units of output of 1,000 watts, or one 
kilo-watt. According to this, an 8-unit machine 
might give, say, ioo amperes at a difference of 
potential of 80 volts, or 2,000 amperes at a differ- 
ence of potential of 4 volts. Such a unit would be 
far more expressive than the usual method of rat- 
ing a machine as having a capacity of such and 
such a number of lights. 

Machine, Dynamo-Electric, Reaction 
Principle of The mutual interaction 



Mac] 



329 



[Mac. 



between the current generated in the armature 
coils of a dynamo-electric machine and the 
field of the machine, each strengthening the 
other until the full working current, which 
the machine is capable of developing, is 
produced. 

When the armature of a series or shunt dynamo 
commences to rotate, the differences of potential 
generated in its coils are very small, since the 
field of the magnet is weak, being merely the 
residual magnetism. The current so produced 
in the armature, circulating through the field 
magnet coils, increases the intensity of the mag- 
netic field of the machine, and this, reacting on 
the armature, results in a more powerful current 
through it. This current again increases the 
strength of the magnetic field of the machine, 
which again reacts to increase the current 
strength in the armature coils, and this continues 
until the machine is producing its full output. 

A dynamo-electric machine very rapidly 
"builds tip," or reaches its maximum current 
after starting. The reaction principle was dis- 
covered by Soren Hjorth, of Copenhagen. 

Machine, Dynamo-Electric, Reversibility 

of The ability of a dynamo to act as 




D D D D 

Fig. 350. Separately Excited Dynamo 

a motor when traversed by an electric cur- 
rent. (See Motor, Electric.) 

Machine, Dynamo-Electric, Separate 

Coil — A dynamo-electric machine in 

which the field magnets are excited by means 



of coils on the armature, separate and dis- 
tinct from those which furnish current to the 
external circuit. 

Machine, Dynamo-Electric, Separately 

Excited A dynamo-electric machine 

in which the field magnet coils have no' con- 
nection with the armature coils, but receive 
their current from a separate machine or 
source. 

A separately excited dynamo-electric machine 
is shown in Fig. 350. 

Separate excitation for constant current ma- 
chines has not come into any extended use in the 
United States. 

Machine, Dynamo-Electric, Series and 
Magneto — A compound-wound dy- 
namo-electric machine in which the arma- 
ture circuit of a magneto-electric machine is 
connected in series with the armature and 
field magnet circuits of a series dynamo. 

The circuit connections of a series and magneto 
dynamo are shown in Fig. 351. 







Fig 3 Si' Series and Magneto Dynamo. 

Machine, Dynamo-Electric, Series and 
Separately Excited A compound- 
wound dynamo-electric machine in which 
there are two separate circuits on the field 
magnet cores, one of which is connected in 
series with the field magnets and the exter- 
nal circuit, and the other with some source 
by which it is separately excited. 



Mac] 



330 



[Mac 



A series and separately excited compound- 
wound dynamo-electric machine is shown in 
Fig. 352. 




R R R 

.vV^Jfe 4"£- -S^ ^- C. 

Fig. 332. Series and Separately Excited Dynamo. 

This machine is employed for maintaining a 
constant potential at its terminals. 

Machine, Dynamo-Electric, Series and 
Shunt Wound A compound-wound 




R R R 

Fig. 3 S3- Series and Shunt- Wound Dynamo. 

dynamo-electric machine in which the field 
magnets are wound with two separate coils, 
one of which is in series with the armature 
and the external circuit, and the other in 
shunt with the armature. 



This is usually called a compound-wound ma- 
chine. (See Machine, Dynamo- Electric, Com- 
pound- Wound. ) 

A compound-wound series and shunt dynamo- 
electric machine is shown in Fig. 353. This ma- 
chine is designed to maintain constant potential 
at its terminals. 

There are two varieties of series and shunt- 
wound dynamos, viz.: 

(1.) Long-shunt compound- wound dynamo. 

(2.) Short-shunt compound-wound dynamo. 

(See Machine, Dynamo-Electric, Compound- 
Wound, Long- Shunt. Machine, Dynamo-Electric, 
Compound- Wound, Short -Shunt.) 

Machine, Dynamo-Electric, Series- Wound 

■ — A dynamo-electric machine, in which 

the field circuit and the external circuit are 




D D D D 

Fig. 334. Series Dynamo. 

connected in series with the armature circuity 
so that the entire armature current must pass 
through the field coils. 

A series dynamo -electric machine is shown in 
^ l %' 354* Here the armature circuit, the field 
circuit and the external circuit are all connected 
in series. 

Since in a series-wound dynamo the armature 
coils, the field and the external series circuit are in 
series, any increase in the resistance of the external 
circuit will decrease the electromotive force from 
the decrease in the magnetizing currents. A de- 
crease in the resistance of the external circuit will, 
in a like manner, increase the electromotive force 
from the increase in the magnetizing current. 



Mac! 



331 



[Mac, 



The use of a regulator avoids these changes in 
the electromotive force. 




Fig. 355- Series Dynamo. 

The dynamo shown in Fig. 355 is series con- 
nected. The armature is ring-shaped. The 
armature core consists of a ring made of so r t iron 
wire. The field is bi-polar, and is obtained by 
the use of four magnet coils and two consequent 
poles. 

Machine, Dynamo-Electric, Shunt and 
Separately Excited A compound- 
wound dynamo-electric machine, in which 




R R R R 

Fig. 356. Shunt and Separately Excited Dynamo. 

the field is excited both by means of a ihunt 
to the armature circuit, and by a current pro- 
duced by a separate source. 
A shunt and separately excited compound- 



wound dynamo-electric machine is shown in Fig. 
356. This machine maintains a constant current 
in its circuit, notwithstanding changes in its ex- 
ternal circuit. 

Machine, Dynamo-Electric, Shunt- Wound 

A dynamo-electric machine in which 

the field magnet coils are placed in a shunt- 
to the armature circuit, so that only a 
portion of the current generated passes 
through the field magnet coils, but all the 
difference of potential of the armature acts at 
the terminals of the field circuit. 

A shunt dynamo-electric machine is shown in 
Fig. 357- 




D D D D 
Fig. 357. Shunt Dynamo. 

In a shunt dynamo -electric machine, an in- 
crease in the resistance of the external circuit in- 
creases the electromotive force, and a decrease in 
the resistance of the external circuit decreases the 
electromotive force. This is just the reverse of 
the series-wound dynamo. 

In a shunt-wound dynamo a continuous balanc- 
ing of the current occurs. The current dividing 
at the brushes between the field and the external 
circuit in the inverse proportion to the resistance 
of these circuits, if the resistance of the external 
circuit becomes greater, a proportionately greater 
current passes through the field magnets, and so 
causes the electromotive force to become greater. 
If, on the contrary, the resistance cf the external 
circuit decreases, less current passes through the 
field, and the electromotive force is proportion- 
ately decreased. 



Mac] 



332 



[Mac. 



In a shunt-wound dynamo the resistance of the 
Shunt should be at least four hundred times that 
of the armature. It is sometimes as much as one 
thousand times as great. — {Urquhart.) 

To obtain complete regulation of the machine 
some form of compounding is necessary. (See 
Machine, Dynamo-Electric, Compound- Wound.) 

Machine, Dynamo-Electric, Single-Mag- 

net A dynamo-electric machine, in 

which the field magnet poles are obtained by 
means of a single coil of insulated wire, in- 
stead of by more than a single coil. 

Machine, Dynamo-Electric, Sparking of 

— An irregular and injurious operation 

of a dynamo-electric machine, attended with 
sparks at the collecting brushes. 

Sparking consists in the formation of small arcs 
under the collecting brushes. One cause of 
sparking is to be found in the brushes leaving one 
commutator strip before making connection with 
the next strip. 

Sparking from this cause may be avoided by so 
placing the brushes as to cause them to bridge 
over the space between two consecutive bars, thus 
permitting them to touch one bar before leaving 
the other. Two brushes, electrically connected, 
are sometimes employed for this purpose, or the 
slots between contiguous bars are slightly inclined 
to the axis of rotation. 

Sparking causes a burning of the commutator 
strips, and an irregular consumption of the 
brushes, both of which produce further irregularis 
ties by the wear of the brushes against the com- 
mutator bars. 

At the moment the brush touches two contigu- 
ous commutator bars, it short circuits the coil 
terminating at those bars. On the breaking of 
this closed circuit, a spark appears under the 
brushes. This spark is often considerable, since 
from the comparatively small resistance of the 
coil, it is apt, when short circuited, to produce a 
heavy current if not exactly at the neutral point. 

Another cause of sparking is to be found in the 
Seif-induction of the armature coils. The extra 
current on breaking forms an injurious spark un- 
der the brushes. This spark may be considerable, 
since the current produced in the coil on mo- 
mentarily short circuiting it by the brushes sim- 
ultaneously touching the adjoining commutator 
segments may be large. 

Sparking occurs when the brushes are not set 



close to the neutral line. Since the principal 
cause for the change in the lead of the brushes is 
the magnetizing effect of the armature coils, it is 
preferable to make the number of windings of 
these as few as possible, and to obtain the neces- 
sary differences of potential by increasing the 
speed of rotation and the strength of the magnetic 
field of the machine. Short armature coils also 
lessen the sparking due to self-induction. 

Sparking at the brushes is also caused by the 
jumping of improperly supported or constructed 
•brushes. 

When the brushes are not set close to the neu- 
tral point, long flashing sparks are apt to occur. 

A lack of symmetry of winding of the arma- 
ture coils will necessarily be attended by injurious 
flashing, from the impossibility of properly ad- 
justing the brushes. 

Machine, Dynamo-Electric, Synchroniz- 
ing Adjusting the phases of two alter- 
nating current dynamos so as to permit their 
being coupled or joined in parallel. 

Machine, Dynamo-Electric, to Short Cir- 
cuit a To put a dynamo-electric ma- 
chine on a circuit of comparatively small 
electric resistance. 

Machine, Dynamo-Electric, Unit of Out- 
put of A unit for the electric power 

furnished by the current of a dynamo-electric 
machine. 

A unit of output equal to 1,000 watts or 
i kilowatt. 

A machine furnishing a current of ioo amperes 
at a difference of potential of 80 volts, would 
have an output of 8,000 watts, and would, 
therefore, be rated as an 8-unit machine. 

Machine, Electric, Rubber of A 

cushion of leather covered with an electric 
amalgam, and employed to produce electricity 
by its friction against the plate or cylinder of 
a frictional electric machine. (See Ma- 
chine, Frict zonal Electric.) 

Machine, Electrostatic Induction 

A machine in which a small initial charge 
produces a greatly increased charge by its in- 
ductive action on a rapidly rotated disc of 
glass or other dielectric. 

An excellent type and example of such a ma- 
chine ij found in the Holtz machine, which con- 



Mac, 



333 



[Mac, 



sists of the following parts, as shown in Fig. 358, 
viz.: 

(1.) A stationary glass plate A, fixed at its 
edges to insulated supports. 

(2.) A movable plate B, capable of rapid rota- 
tion on a horizontal axis, by a driving pulley. 

A 




Fig. 358. Holtz Electric Machine. 

(3.) Armatures of varnished paper f, f ', placed 
•on opposite sides of the fixed plate at holes or 
windows P, P ', cut in the plate. The armatures 
are placed on the side of the fixed plate away from 
the moving plate, or on the back of the plate, so 
that the plate, on its rotation, moves towards 
tongues of paper attached to the middle of the 
armature. 

(4.) Metal combs placed in front of the movable 
disc opposite the armatures, and connected with 
the brass balls m, n, one of which is movable 
towards and from the other by means of a suitably 
supported insulating handle connected with it. 

A small initial charge is given to one of the 
armatures by holding a plate of electrified vul- 
canite against it, and rotating the machine while 
the balls m, n, are in contact. As soon as the ma- 
chine is charged the balls are gradually separated^ 
when a torrent of sparks will pass between them 
so long as the plate is rotated. 

When the balls are separated too far the sparks 
cease to pass. The balls must then be again 
"brought into contact and gradually separated as 
before. 

The Holtz machine can be regarded as a re- 
volving electrophorus provided with means for 
constantly discharging and recharging the upper 
metallic plate. (See Electrophorus.) 

The action of the machine is well described by 
S. P. Thompson in his "Elementary Lessons on 
Electricity and Magnetism,' 1 as follows: 

"Suppose a small -j- charge to be imparted at 
the outset to the right armature f ; this charge acts 



inductively across the discs upon the metallic 
comb, repels electricity through it, and leaves the 
points negatively electrified. They discharge 
negatively electrified air upon the front surface of 
the movable disc; the repelled charge passes 
through the brass rods and balls, and is discharged 
through the left comb upon the front side of the 
movable disc. Here it acts inductively upon the 
paper armature, causing that part of it which is 
opposite itself to be negatively charged and re- 
pelling a -j- charge into its farthest part, viz., into 
the tongue, which being bluntly pointed, slowly 
discharges a -j- charge upon the back of the mov- 
able disc. If now the disc be turned round, 
this -f- charge on the back comes over from the left 
to the right side, in the direction indicated by the 
arrow, and, when it gets opposite the comb, in- 
creases the inductive effect of the already existing 
-f- charge on the armature, and therefore repels 
more electricity through the brass rods and knob 
into the left comb. Meantime the — charge, which 
we saw had been induced in the left armature, has 
in turn acted on the left comb, causing a -j- charge 
to be discharged by the points upon the front of 
the disc; and drawing electricity through the 
brass rods and knobs, has made the right comb 
still more highly — , increasing the discharge of 
— ly electrified air upon the front of the disc, neu- 
tralizing the -J- charge which is being conveyed 
over from the left. These actions result in causing 
the top half of the moving disc to be — ly electri- 
fied. The charges on the front serve, as they are 
carried round, to neutralize the electricities let off 
by the poincsof the combs, while the charges on 
the back, induced respectively in the neighbor- 
hood of each of the armatures, serve, when the 
rotation of the disc conveys them round , to increase 
the inductive influence of the charge on the 
other armature." 

The student will be aided in following Prof. 
Thompson's explanation by the diagrammatic 
sketch, shown in Fig. 359. Here the rotating plate 
is shown for convenience in the form of a cylinder. 
The armatures are shown on the back of the plate 
at f and f, opposite the brass collecting combs P' 
and P, with their discharging rods and balls a, a. 

The effect of the positive charge given to the 
right hand armature f, directly through the 
comb P , rods a, a, comb P, to left hand arma- 
ture f, is readily seen. The rotation ot the plate 
being m the direction of the curved arrows, the 
charging of the front of the plate by convection 
streams from the combs, and the back ot the plate 



Mac] 



334 



[Mac. 



from the points of the paper armatures, as well as 
the character of tho charge, will be understood. 
There thus results, as is shown, a positive charge 
on both the front and back of the upper half of 

+. + 

■K 




Fig. 359. Plate of Holt z Machine. 
the rotating plate, and a negative charge on both 
sides of its lower half. A reversal of polarity of 
the plate occurs at the line P a a P'. Sometimes 
the reversal does not occur, and the machine either 
loses its charge entirely, or in part. A conductor 
S S, furnished with points, is sometimes provided 
to lessen the chances of lack of reversal. 

Machine, Faradic A machine for 

producing faradic currents. 

There are two varieties of faradic machines, 
viz.: magneto faradic apparatus and simple in- 
duction apparatus. 

Machine, Frictional Electric A 

machine for the development of electricity by 
friction. 

A frictional electric machine consists of a plate 
or cylinder of glass A, Fig. 360, capable of rota- 
tion on a horizontal axis. 

A rubber formed of a chamois skin, covered 
with an amalgam of tin and mercury, is 
placed at B. By the rotation of the plate the 




Fig. 360. Frictional Electric Machine. 

rubber becomes negatively and the glass posi- 
tively excited. An insulated conductor D, called 
the prime or positive conductor, provided with a 



comb of points, becomes positively charged by in- 
duction. The machine will develop electricity 
best if a conductor attached to the rubber is con- 
nected with the ground, as by a chain. 

Machine, Holtz A particular form 

of electrostatic induction machine. (See 
Machine, Electrostatic Induction^) 

Machine, Influence An electrical 

machine depending for its action on electro- 
static induction. 

The Wimshurst and Holtz machines are influ- 
ence machines. (See Machine, Electrostatic In- 
duction. Machine, Winishurst Electrical. Ma- 
chine, Holtz.) 

Machine, Influence, Wimshurst's Alter- 
nating" An electrostatic induction ma- 
chine by means of which a series of rapidly- 
alternating charges are produced. 

Although such a machine furnishes a torrent of 
sparks between its terminals, yet it is unable to 
furnish a permanent charge to a Ley den jar 
or condenser, since its 
oscillatory discharges, 
continually undo at any 
small interval of time, 
what was done at the 
preceding interval, and 
thus leave the jar un- 
charged. 

Machine, Magneto 
Blasting — A 

magneto-electric ma- 
chine employed for 
generating the cur- 
rent used in electric^; 
blasting. 




361. Magneto- Electric 
Machine. 



Machine, Magneto-Electric A ma- 
chine in which there are no field magnet coils, 
the magnetic field of the machine being due 
to the action of permanent steel magnets. 

A dynamo in which currents are produced by 
the motion of armature coils past permanent mag- 
nets. (See Machine, Dynamo-Electric.) 

A magneto-electric machine is shown in Fig- 
361. 

Another form of magneto-electric machine is 
shown in Fig. 362. 

This latter form of machine is known as a hand 
generator, in contradistinction to one driven by 
power and called a power generator. 



Mac] 



335 



[Mac. 



The field is obtained by means of a number of 
.separate permanent magnets so combined as to 




Fig. 362. Magneto- Electric Machine. 

act as a single magnet. The armature is rotated 
by hand. 

Machine, Mouse-Mill A form of 

convection induction machine, invented by 
Sir William Thomson to act as the replen- 
isher of his electrometer. (See Machine, 
Electrostatic Induction?) 

Machine, Rheostatic A machine 

devised by Plante in which continuous static 
effects of considerable intensity are obtained 
"by charging a number of condensers in mul- 
tiple-arc and discharging them in series. 

The condensers are charged by connecting 
them with a number of secondary or storage bat- 
teries. 

Machine Telegraphy. — (See Telegraphy, 
Machine?) 

Machine, Toppler-Holtz A modi- 
fied form of Holtz machine in which the 
initial charge of the armatures is obtained by 
the friction of metallic brushes against the 
armatures. 

Machine, Wimshurst Electrical 

A form of convection electric machine in- 
vented by Wimshurst. 

Like the Holtz machine, the Wimshurst ma- 
chine is a convection induction machine. It is, 
"however, more efficient in action, and will prob- 
ably soon supersede the former machine. The 
Wimshurst machine consists of two shellac-var- 
nished glass plates that are rapidly rotated in op- 
posite directions. Thin metallic strips are placed 
on the outside of each of the plates, in the radial 
positions shown in Fig. 363. These strips act 



both as inductors and carriers ; the carriers of 
one plate acting as inductors to the other plate. 

Two curved brass rods, terminating in fine wire 
brushes that touch the plates, are placed as shown, 
one at the front of the plate, and one at the back, 
at right angles to each other. Pairs of conduct- 




Fig. 363. The Wimshurst Electrical Machine. 

ors, connected together, provided with collecting 
points, are placed diametrically opposite each 
other, as shown. Sliding conductors, terminated 
with metallic balls, are provided for discharging 
the conductors. Ley den jars, the inner coatings 
of which are connected with two discharging 
rods, and the outer coatings together, may be em- 
ployed in this as in the Holtz machine. 

The exact action of this machine is not thor- 
oughly understood. 

Machines, Dynamo-Electric, Varieties of 

Dynamo-electric machines may be 

divided into classes according to — 

(1.) The manner in which the magnetism of 
the field magnets is obtained. 

(2.) The character of their armatures. 

(3.) The nature of the current obtained, whether 
continuous or alternating. 

(4.) The form of their field magnets. 

(5.) The nature of their magnetic fields. 

(6.) The manner in which the current of the 
field magnets, the armature and the external 
circuits are connected. 

Mack A term proposed by Mr. 

Oliver Heaviside for a unit of self-induction. 

The term Mack is derived from Maxwell. The 
unit of self-induction has also been a secohm and 
a quadrant. 



Mad.] 



The term Max would seem to be indicated. 
In the United States the unit of self-induction is 
called a Henry, after Prof. Joseph Henry. (See 
Henry, A. ) 

Made Circuit. — (See Circuit, Made) 

Magazine Fuse. — (See Fuse, Magazine.) 

Magne-Crystallic Action. — (See Action, 
Magne-Cryst allied) 

Magnet. — A body possessing the power 
of attracting the unlike pole of another mag- 
net or of repelling the like pole ; or of at- 
tracting readily magnetizable bodies like iron 
filings to either pole. 

A body possessing a magnetic field. (See 
Field, Magnetic) 

The lines of force are assumed in passing 
through the magnetic field to come out at the north 
pole of the magnet and to go in at the south pole. 
All lines of force form closed magnetic circuits. If 
a magnetizable body is brought into a magnetic 
field, the lines of magnetic force are concentrated 
on it and pass through it. The body therefore be- 
comes magnetic. The intensity of the resulting 
magnetism depends on the number of lines of force 
that pass through the body, and the polarity on 
the direction in which they pass through it. 

A magnetized bar cannot be regarded as a 
source of energy in itself. Energy must be ex- 
pended to magnetize the iron, and must also be 
expended to demagnetize it. 

Magnet, Anomalous — A magnet 

possessing more than two free poles. 

There is no such thing as a unipolar magnet. 



Fig. 364. Anomalous Magnet. 

All magnets have two poles. Sometimes, how- 
ever, several magnets are so grouped that there 
appear to be more than two poles in the same 
magnet. 



336 [Mag. 

It is clear, however, that the central pole is in 
reality formed of two juxtaposed negative poles, 
and that ABC, actually consists of two magnets 
with two poles to each. 

The magnet A B C D, Fig. 365, which in like 
manner appears to possess four separate poles, in 
reality is formed of three magnets with two poles 
to each. 

Since unlike magnetic poles neutralize each 
other, it is clear that only similar poles can thus be 
placed together in order to produce additional 
magnet poles. 

S S 






*H 



gpi5|p|| ss/MMm 




Fig. 365. Anomalous Magnet. 



Thus, in Fig. 364, the magnet ABC, appears 
to possess three poles, two positive poles at A 
and C, and a central negative pole at B. 




Anomalous Magnet. 



The six-pointed star shown in Fig. 366, is art 
anomalous magnet with apparently seven poles. 
The formation of the central N-pole, as is evident 
from an inspection of the drawing, is due to the 
six separate north poles, n, n, n, n, n, n, of the 
six separate magnets Sn, Sn, etc. Such a magnet 
would be formed by touching the star at the point 
N, with the S-pole of a sufficiently powerful 
magnet. 

The extra poles are sometimes called consequent 
foles. Their presence may ba shown by means of 
a compass needle, or by rolling the magnet in iron 
filings, which collect on the poles. 

Magnet, Artificial A magnet pro- 
duced by induction from another magnet, or 
from an electric current. 

Any magnet not found in nature is called an 
artificial magnet. 

Magnet, Axial A name sometimes 

given to a solenoid with an axial or straight 
core. 

Magnet, Bell-Shaped A modifica- 
tion of a horseshoe magnet in which the ap- 
proached poles are semi-annular in shape, and 
form a split tube. 

Bell-shaped magnets are used in many galva- 



Mag.] 



337 



[Hag. 



nometers, because they can be readily dampened 
by surrounding them by a mass of copper. The 
needle in its motion produces currents that tend 
to oppose, and, therefore, to stop its motion. (See 
Laws, Lenz's.) 

Magnet, Club-Footed An electro- 
magnet whose core is in the form of a horse- 
shoe and is provided with a magnetizing coil 
on one pole only. 

Magnet Coil.— (See Coil, Magnet.) 

Magnet, Compensating A magnet 

placed over a magnetic needle, generally over 
the magnetic needle of a galvanometer, for 
the purpose of varying the direction and in- 
tensity of the magnetic force of the earth on 
such needle. (See Galvanometer, Reflecting?) 

A magnet, called a compensating magnet, is 
sometimes placed on a ship, near the compass 
needle, for the purpose of neutralizing the local 
variations produced on the compass needle by the 
magnetism of the ship. 

Magnet, Compound A number of 

single magnets, placed par- 
allel and with their similar 
poles facing one another, 
as shown in Fig. 367. 

Compoimd magnets are 
stronger in proportion to their 
weight than single magnets. 

Magnet, Compound 
Horseshoe A horse- 
shoe magnet composed of 
several separate horseshoe 
magnets placed with their 
similar poles together. 

A compound horseshoe Fig. 3 6 7. Compound 
magnet is shown in Fig. 368. Magnet. 

A -horseshoe magnet possesses greater portative 
power than a straight bar magnet of the same 
weight. (See Power, Portative.) 

(1.) Because its opposite poles are nearer to- 
gether; and 

(2.) Because the magnetic resistance of its 
circuit is less, the lines of magnetic force closing 
through the armature, and thus concentrating 
the magnetic attraction on the armature. 

Electro-magnets are generally made of the 
horseshoe shape. 

Magnet, Controlling —A name 





sometimes applied to the controller in the 
Thomson-Houston automatic system of cur- 
rent regulation. (See Controller?) 

Generally any mag- 
net which controls 
some particular ac- 
tion, ri^w 

Magnet, Cylindri- 
cal A magnet 

in the shape of a cyl- 
inder. 

A helix or solenoid 
through which a cur- 
rent of electricity is 
passing is, so far as ex- 
ternal space is con- 
cerned, the exact mag- 
netic equivalent of a 
cylindrical magnet. 

Magnet, Damping 

— Any magnet 

employed for the pur- Fig. 368. Compound Horse- 

pose of checking the shoe M a s™t- 

velocity of motion of a moving body or mag- 
net. 

Damping magnets generally act by the resist- 
ance which they offer to the passage of a 
metallic disc, so moved as to cut the lines of force 
of their field. 

Magnet, Electro A magnet pro- 
duced by the passage of an electric current 
through a coil of insulated wire surrounding 
a core of magnetizable material. 

The magnetizing coil is called a helix or sole- 
noid. (See Magnetism, Ampere's Theory of.) 

Strictly speaking, the term electro-magnet is 
limited to the case of a magnet provided with a 
soft iron core, which enables it to rapidly acquire 
its magnetism on the passage of the magnetizing 
current, and as rapidly to lose its magnetism on 
the cessation of such current. 

An electric current passed around a bar of 
magnetizable material, in the manner and direc- 
tion shown in Fig. 369, will produce the polarity 
N and S, at its ends or extremities as marked. 

The directions of the currents required to pro- 
duce N and S, poles respectively are shown in 
Fig. 370. 

The cause of this difference of polarity will be 
readily understood from a study of the direction 



Mag.] 



338 



[Mag. 



of lines of magnetic force in the field produced 
by an electric current. 




Fig. j6g. Polarity of Current. 

The direction of this polarity may be predicted 
by the following modification of a rule by Ampere: 

Imagine yourself swimming in the wire in the 
direction of the current; if, then, your face is 




Fig. 370, North and South Magnet Poles. 

turned toward the bar that is being magnetized, 
its North seeking pole will be on your left. 





Fig. 37 1 Deflection of 
Magnetic Needle. 



Fig' 372. Deflection of 

Magnetic Needle. 



If, for example, the conductor A B, be traversed 
by a current in the direction from B, to A, as 
shown in Fig. 371, the north pole N, of the 
needle N S, placed under the conductor, is de- 
flected, as shown, to the left of the observer, who 
is supposed to be swimming in the current, facing 
the needle. If the current flow in the opposite 



direction, as from A, to B, as shown in Fig. 372, 
the N, pole of the needle is deflected as shown, 
but still to the left of the observer supposed to be 
swimming as before. 

In any electric circuit, the lines of magnetic 
force, produced by the passage of the current, form 
circles around the circuit in planes atright angles 
to the direction of the current, as shown in Fig. 
373. The direction of these lines of force is the 
same as that of the hands of a watch, if the cur- 
rent be supposed to flow away from the observer. 
(See Field, Magnetic, of an Electric Current.) 




Fig. 373. Direction of Lines of Force. 

Remembering now that the lines of force are 
supposed to come out at the north pole of a magnet, 
and to pass in at the south pole, it is evident that 
if the current flows in the direction shown in Fig. 




Fig. 374. Direction of Lines of Force. 

374, the lines of force will come out at the north 
pole and pass in at the south pole. 

Since in a right-handed helix the wire passes 
around the axis in the opposite direction to that 
in which it passes in a left-handed helix, it is 
evident that the helices shown in Fig. 375 at I, 
and 2, will produce opposite polarities at the 
points of entrance and exit by a current flowing 
in the direction of the arrows, 

If the current be sent through the right handed 
helix, shown at I, from b, to a, that is, from the 
left to the right in the figure, a south pole will be 
produced at b, and a north pole at a. If, how- 
ever, it be sent from a, to b, the polarity will be 
reversed. 

If the current be sent through the left-handed 



JUag.J 



339 



[Mag. 



helix, shown at 2, from a, to b, that is, from the left 
to the right in the figure, a north pole will be pro- 
duced at a, and a south pole at b. If, however, it 
be sent in the opposite direction, the polarity will 
be reversed. 

Therefore, in an electro-magnet, on the core 
of which several layers or thicknesses of wire are 
wound, in which the current flows through one 
layer, in, say a direction from right to left, the cur- 
rent must return through the next layer in the 
opposite direction, or from left to right. The 
polarities of the same extremities of the helices 
are, however, the same in all cases, since the 
layers are successively right and left handed 
to the current. The winding shown at 3, pro- 
duces consequent poles. 

The following laws express the more important 
principles concerning electro-magnets: 

(i.) The magnetic intensity (strength) of an 
electro-magnet is nearly proportional to the 
strength of the magnetizing current, provided the 
core is not saturated. 

(2.) The magnetic strength is proportional to 
the number of turns of wire in the magnetizing 
coil; that is, to the number of ampere turns. (See 
Turns, Ampere.) 

(3.) The magnetic strength is independent of 
the thickness or material of the conducting wires. 

These laws may be embraced in the more gen- 
eral statement that the strength of an electro- 




■Fig. 37 J. Right- Handed, Left- Handed and Anomalous 
Helices. 

magnet, the size of the magnet being the same, 
is proportional to the number of its ampere turns. 
i(See Turns, Ampere. ) 

A short interval of time is required for a cur- 
rent to thoroughly magnetize a powerful electro- 
magnet. 

A few moments are also required for a power- 
ful magnet to thoroughly lose its magnetism. At 
the same time electro magnets are capable of 
acquiring or losing their magnetism with very 
great rapidity. It is, in fact, on this ability pos- 
sessed to so remarkable a degree by soft iron, that 



the value of an electro-magnet for many purposes 
depends . (See Lag, Magnetic. ) 

A difference exists between the action of a mag- 
netized disc and a hollow coil of wire through 
which a current of electricity is passing. So 
far as the space outside either is concerned, the 
action is the same, but the coil is penetrable on 
the inside and the disc is not, and for the inside of 
the space, therefore, there is a difference in the ac- 
tion. 

Magnet, Electro, Bar An electro- 
magnet, the core of which is in the form of a 
straight bar or rod. 

Magnet, Electro, Cylindrical An 

electro-magnet, the core of which consists of 
a hollow cylinder provided with a slot extend- 
ing parallel to its axis. 

The gap in the cylinder suffices for the placing 
of the magnetizing coils, and forms the poles. 
This form of electro-magnet was devised by 
Joule. Its construction will be understood from 
an inspection of Fig. 376. 




Fig. 37 b. Cylindrical Electro-Magnet. 

Mag-net, Electro, Horseshoe • — An 

electro-magnet, the core of which is in the 
shape of a horseshoe or U. 

Magnet, Electro, Hughes' — An 

electro-magnet in which a U-shaped per- 
manent magnet is provided with pole pieces 
of soft iron, on which only are placed the 
magnetizing coils. 

A quick acting electro-magnet, in which 
the magnetizing coils are placed on soft iron 
pole pieces that are connected with and form 
the prolongations of the poles of a permanent 
horseshoe magnet. 

Hughes devised this form of electro-magnet in 
order to obtain the best effects from currents of 
but short duration. , 

He thus obtained a quick acting magnet, neces- 
sary to insure the success of his system of printing 
telegraph, where the magnetizing currents at 
times have a duration of but the .20 of a second. 



Mag.] 



340 



[Mag. 



Magnet, Electro, Joule's Cylindrical 

— An electro-magnet provided with a 

hollow cylindrical core. (See Magnet, Elec- 
tro, Cylindrical) 

Magnet, Electro, Iron-Clad —An 

electro-magnet whose magnetizing coil is 
almost entirely surrounded by iron. 

The effect of the iron casing is to greatly re- 
duce the magnetic re- 
sistance of the circuit. 
A form of iron clad elec- 
tro-magnet is shown in 
Fig« 377- Here one of 
the poles is connected 
with a casing of iron, 
external to the coils, and 
is thus brought nearer to 
the other pole. 

Magnet, Electro, 

Long-Core An electro-magnet with 

a long core of iron. 

A long-core electro-magnet magnetizes and 
demagnetizes much more slowly than a short- 
core electro-magnet. 

-—An 




Fig 377- Iron- Clad 
Electro- Magnet . 



Magnet, Electro, Short-Core — 

electro-magnet with a short core of iron. 

A short-core electro-magnet possesses the power 
of being magnetized and demagnetized much more 
rapidly than a long-core magnet. 

Magnet, Electro, Yoked-Horseshoe 

— A horseshoe electro-magnet, in which the 
two straight limbs are formed of two straight 
rods or bars, yoked together at one pair of 
ends by a yoke or bar of iron. 

In some cases the magnetizing coils are placed 
on each of the limbs. Sometimes, however, a 
single coil is placed at the middle of the yoke 
and the limbs are left bare. 

Even with the closest possible fitting the re- 
sistance of the magnetic circuit is much greater 
in this form of electro-magnet, owing to the 
smaller permeability of the air gap at the joints, 
than it would be if the entire core were made or a 
single piece of iron. A yoked electro-magnet is, 
however, more convenient to make and use. 

Magnet, Electro, Zigzag A multi- 
polar electro-magnet, the magnetizing coils 
ot which aie separately wound in grooves 
cut in the face of straight or curved bars. 




A form of zigzag electro- magnet devised by 
Joule is shown in Fig. 378. The spiral char- 
acter of the winding 
produces the alternate 
North and South polari- 
ties shown in the figure. 

Magnet, Equator of 

— A point ap- 
proximately midway 
between the poles of a 
straight bar magnet, or Fig 3?8 zigzag Electro- 
nearly midway from Magnet. 
the poles of a horseshoe magnet if meas- 
ured along the bar from each pole. 

This term was proposed by Dr. Gilbert. It is 
now almost entirely displaced by the term neutral 
point. 

Magnet, High-Resistance A term 

sometimes used in place of long-coil magnet 
whose coils have a high electric resistance. 
(See Magnet, Long-Coil) 

The term long-coil magnet is, perhaps, the pre- 
ferable one, because the resistance of a coil, per 
se, has nothing to do with its magnetizing power, 
which is determined by its ampere turns. (See 
Turns, Ampere. Magnet, Long Coil.) 

Magnet, Horseshoe A magnetized 

bar of steel or iron bent in the form of a 
horseshoe or letter U. 

Magnet, Iron-Clad A magnet whose 

magnetic resistance is lowered by a casing of 
iron connected with the core and provided for 
the passage of the lines of magnetic force, 
(See Magnet, Tubular) 

Magnet, Jacketed A term some- 
times applied to a form of iron-clad magnet. 
(See Magnet, Lron-Clad.) 

Magnet, Keeper of A mass of soft 

iron applied to the poles of a magnet through 
which its lines of magnetic force pass. (See 
Field, Magnetic) 

The keeper of a magnet differs from its arma- 
ture in that the keeper while acting as such is 
always kept on the poles to prevent loss of mag- 
netization, while the armature, besides acting as 
a keeper, may be attracted towards, or, if an 
electro-magnet, be repelled from the magnet 
poles. While performing its functions the keeper 
is always fixed, the armature generally, though 



Mag.] 



341 



(Mag. 



not always, is in motion. A keeper is, of course, 
only used with permanent magnets. 

Opinion is divided as to the efficacy of the 
keeper in preventing loss of magnetization in 
certain cases. 

Magnet, Long-Coil —An electro- 
magnet whose magnetizing coil consists of 
many turns of thin wire. 

Magnet, Low-Resistance —A term 

sometimes used in place of short-coil mag- 
net. (See Magnet, Short-Coil.) 

This term, short-coil magnet, is the preferable 
one. 

Magnet, Marked Pole of A name for- 
merly applied to that pole of a magnet which 
points approximately to the geographical 
north. 

If the pole of the magnet that points to the 
geographical north be in reality the north pole 
of the magnet, then the earth's magnetic pole in 
the Northern Hemisphere is of south magnetic 
polarity. In the United States, and Europe 
generally, this is regarded as the fact. 

The French, however, formerly called the 
pole of the needle that points to the earth's 
geographical north the south or austral pole. 
In America and England it is called the north pole, 
the marked pole, or the north-seeking pole, and 
the Northern Hemisphere is assumed to possess 
south magnetic polarity. (See Pole, Magnetic, 
Austral. Pole, Magnetic, Boreal.) 

Magnet, Moment of The effective 

force of a magnetic couple as obtained by 
multiplying one of the forces of the couple 
by the perpendicular distance between the 
directions of the forces. 

The moment of a magnet is equal to the prod- 
uct of the volume of the magnet and the in- 
tensity of magnetization, or simply its magnetiza- 
tion. 

Magnet, Natural A name some- 
times given to a lodestone. (See Lodestone?) 

Magnet, Neutral Line of (See 

Line, Neutral, of a Magnet?) 

Magnet, Permanent A magnet of 

hardened steel or other paramagnetic sub- 
stance which retains its magnetism for a long 
time after being magnetized. 



A permanent magnet is distinguished, in this 
respect, from a temporary magnet of soft iron, 
which loses its magnetization very shortly after 
being taken from the magnetizing field. 

Magnet, Portative Power of The 

lifting power ot a magnet. 

The portative or lifting power of a magnet, 
depends on the form ot the magnet, as well as on 
its strength. A horseshoe magnet, for example, 
will lift a much greater weight than the same 
magnet if in the torm ot a straight bar. 

This is due not only to the mutual action of the 
approached poles, but also to the decreased re- 
sistance of the magnetic circuit, and to the 
greater number of lines ot magnetic force that 
pass through the armature. The portative power 
is proportional to the area of contact and the 
square of the magnetic intensity, the formula 
being 

""8^X981"; 
in which P, is the lifting power in grammes, A, 
the area of contact in square centimetres, and B, 
is the number of lines of force per square centi- 
metre. 

Magnet Operation. — (See Operation, 
Magnet?) 

Magnet, Receiving A name some- 
times given to the relay of a telegraphic sys- 
tem. (See Relay.) 

In general, any magnet, used directly in the 
receiving apparatus, at the receiving end of a 
line connecting a system of electric communi- 
cation between transmitting and receiving 
instruments. 

Magnet, Regulator —A magnet, the 

operation of which is to automatically effect 
any desired regulation. 

The magnet in the Thomson-Houston sys-» 
tern of automatic regulation, by means of 
which the commutator collecting brushes are 
automatically shifted to such positions on the 
commutator as will maintain the current 
practically constant, despite the changes in. 
the resistance of the circuit external to the 
machine. (See Regulation Automatic?) 

Magnet, Relay An electro -magnet, 

whose coils are connected to the main line of 
a telegraphic circuit, and the movements of 



Mag.] 



342 



[Mag. 



whose armature is employed to bring a local 
battery into action at the receiving station, 
the current of which operates the register or 
sounder. 

Magnet, Short-Coil An electro- 
magnet whose magnetizing coil consists of a 
few turns of short, thick wire. 

simple 



mag- 



Magnet, Simple A 

netized bar. 

The term simple magnet is used in contradis- 
tinction to compound magnet. (See Magnet, 
Compotind. ) 

Magnet, Sluggish A magnet that 

magnetizes or demagnetizes sluggishly. 

An electro-magnet becomes sluggish when sur- 
rounded by a sheathing of copper, on account of 
the currents induced in the sheathing in a direction 
opposite to those passing through the magnetizing 
coil. 

Magnet, Solenoidal A thin, uni- 
formly magnetized straight bar of steel, of 
such a length that its poles, situated at ex- 
tremities or ends of its longer axis, act on 
external objects as if equal and opposite quan- 
tities of magnetism were concentrated at such 
extremities. 

It derives its name solenoidal from the simi- 
laiity between its action and that of a solenoid. 
Unless very carefully magnetized, a magnet will 
not act as a solenoidal magnet. (See Magnet, 
Electro. Magnetism, Solenoidal Distribution of.) 

Magnet, Tubular A form of horse- 
shoe magnet, in which one pole is brought 
near the opposite pole by a hollow cylinder 
or tube of iron, which is placed in contact 
with one of the magnetic poles, so as to com- 
pletely surround the other, except in the plane 
of cross-section of that pole. 

A form of iron-clad magnet. (See Mag- 
net, Iron-Clad?) 

There is thus obtained a magnet, with two 
•concentric poles, one solid and the other annular, 
the portative power of which is much greater than 
that of a horseshoe magnet of equal dimensions. 

Magnet, Field, of Dynamo-Electric Ma- 
chine One of the electro-magnets em- 
ployed to produce the magnetic field of a dy- 
namo-electric machine. 



The field magnets consist of a suitable frame, 
or we, on which the field magnet coils are 
wound. 

The field magnet cores are made of thick and 
solid iron, as soft as possible. They should con- 
tain plenty of iron in order to avoid too ready 
magnetic saturation. 

All edges and corners are to be avoided, since 
they tend to cause an irregular distribution of the 
field. 

The field magnets should in general have suffi- 
cient magnetic strength to prevent the magnet- 
izing effect of the armature from unduly influ- 
encing the field, and thus, by causing too great a 
lead, produce injurious sparking. 

Magnetic or Magnetical. — Pertaining to 
magnetism. 

Magnetic Adherence.— (See Adherence, 
Magnetic.) 

Magnetic Air Circuit. — (See Circuit, Air, 
Magnetic?) 

Magnetic Air Gap.— (See Gap, Air, Mag- 
netic?) 

Magnetic Attraction. — (See Attraction, 
Magnetic?) 

Magnetic Axis.— (See Axis, Magnetic?) 

Magnetic Axis of a Straight Needle. — 

(See Axis, Magnetic, of a Straight Needle?) 

Magnetic Azimuth. — (See Azimuth, Mag- 
netic?) 

Magnetic Battery.— (See Battery, Mag- 
netic?) 

Magnetic Bridge.— (See Bridge, Mag- 
netic?) 

Magnetic Circuit.— (See Circuit, Mag- 
netic?) 

Magnetic Closed-Circuit.— (See Circuit, 
Closed Magnetic?) 

Magnetic Conductance.— (See Conduct- 
ance, Magnetic?) 

Magnetic Core, Closed (See Core, 

Closed-Magnetic?) 

Magnetic Core, Open (See Core, 

Open-Magnetic?) 

Magnetic Couple.— (See Couple, Mag- 
netic?) 



Mag. 



343 



[Mag. 



Magnetic Curyes.— (See Curves, Mag- 
netic.) 

Magnetic Day of Disturbance. — (See Day 
of Disturbance, Magnetic?) 

Magnetic Declination.— (See Declina- 
tion.) 

Magnetic. Density. — (See Density, Mag- 
netic.) 

Magnetic Dip. — (See Dip, Magnetic.) 

Magnetic Elements of a Place. — (See 
Elements, Magnetic, of a Place?) 

Magnetic Equalizer. — (See Equalizer, 
Magnetic.) 

Magnetic Explorer. — (See Explorer, 
Magnetic.) 

Magnetic, Ferro Magnetic after 

the manner of iron or other paramagnetic 
body. (See Paramagnetic.) 

Magnetic Field. — (See Field, Magnetic?) 

Magnetic Field, Reversing (See 

Field, Magnetic, Reversing?) 

Magnetic Field, Shifting (See 

Field, Magnetic, Shifting) 

Magnetic Figures. — (See Figures, Mag- 
netic. Field. Magnetic.) 

Magnetic Filament. — (See Fila?nent, 
Magnetic.) 

Magnetic Flow. — (See Flow, Magnetic) 

Magnetic Flux. — (See Flux, Magnetic) 

Magnetic Force. — (See Force, Magnetic) 

3Iagnetic Inclination. — (See Inclination, 
Magnetic) 

Magnetic Induction. — (See Induction, 
Magnetic) 

Magnetic Induction, Dynamic 

(See Inductio7i, Magnetic, Dynamic) 

Magnetic Induction, Static (See 

Induction, Magnetic, Static) 

Magnetic Inertia. — (See Inertia, Mag- 
netic) 

Magnetic Intensity. — (See Intensity, 
Magnetic) 

Magnetic Joint. — (See Joint, Magnetic) 



Magnetic Lag. — (See Lag, Magnetic) 

Magnetic Latitude. — (See Latitude, Mag- 
netic) 

Magnetic Leakage. — (See Leakage, Mag- 
netic) 

Magnetic Lines of Force. — (See Force, 
Magnetic, Lines of) 

Magnetic Mass. — (See Mass, Magnetic) 

Magnetic Memory.— (See Memory, Mag- 
netic) 

Magnetic Meridian. — (See Meridian, 
Magnetic) 

Magnetic Moment. — (See Moment, Mag- 
netic) 

Magnetic Normal Day.— (See Day, Nor- 
mal, Magnetic) 

Magnetic Observatory.— (See Observa- 
tory, Magnetic) 

Magnetic Output. — (See Output, Mag- 
netic) 

Magnetic Parallel. — (See Parallels, Mag- 
netic) 

Magnetic Permeability. — (See Permea- 
bility, Magnetic) 

Magnetic Permeance. — (See Permeance, 
Magnetic) 

Magnetic Permeation. — (See Permeation, 
Magnetic) 

Magnetic Poles. — (See Poles, Magnetic) 

Magnetic Poles, False (See Pole, 

Magnetic, False) 

Magnetic Proof Piece. — (See Piece, Mag- 
netic Proof) 

Magnetic Proof Plane. — (See Plane, 
Proof, Magnetic) 

Magnetic Reluctance. — (See Reluctance, 
Magnetic) 

Magnetic Repulsion. — (See Repulsion, 
Magnetic) 

Magnetic Resistance. — (See Resistance, 
Magnetic) 

Magnetic Retardation. — (See Retarda- 
tion, Magnetic.) 



Mag.] 344 

Magnetic Retentivity — (See Retentivity, 
Magnetic) 

Magnetic Saturation. — (See Saturation, 
Magnetic.) 

Magnetic Screen or Shield. — (See 

Screen or Shield, Magnetic) 

Magnetic Screening. — (See Screening, 
Magnetic.) 

Magnetic Self-Induction. — (See Induc- 
tion, Self, Magnetic) 

Magnetic Shells. — (See Shells, Magnetic) 

Magnetic Shunt. — (See Shunt, Magfietic) 

Magnetic, Sidero A term proposed 

by S. P. Thompson to replace the term ferro- 
magnetic. (See Magnetic, Ferro) 

Magnetic Solenoid.— (See Solenoid, Mag- 
netic) 

Magnetic Sounds. — (See Sounds, Mag- 
netic) 

Magnetic Spin. — (See Spin, Magnetic) 

Magnetic Storm. — (See Storm, Mag- 
netic) 

Magnetic Strain. — (See Strain, Mag- 
netic) 

Magnetic Stress. — (See Stress, Magnetic) 

Magnetic Susceptibility. — (See Suscepti- 
bility, Mag?ietic) 

Magnetic Theodolite. — (See Theodolite, 
Magnetic) 

Magnetic Unit Pole. — (See Pole, Unit, 
Magnetic.) 

Magnetic Units. — (See Units, Magnetic) 

Magnetic-Vane Ammeter. — (See Amme- 
ter, Magnetic- Vane) 

Magnetic-Vane Voltmeter. — (See Volt- 
meter, Magnetic- Vane) 

Magnetic Variations. — (See Variation, 
Magnetic) 

Magnetic Variation Transit.— (See Tran- 
sit, Magnetic Variation) 

Magnetic Variometer. — (See Variometer, 
Magnetic) 



[Mag. 

Viscosity.— (See Viscosity, 



Mag- 



Magnetic 

Magnetic) 

Magnetic Whirl.— (See Whirls, 
netic.) 

Magnetic Whirl, Expanding (See 

Whirl, Magnetic, Expanding) 

Magnetics, Electro That branch 

of electric science which treats of the rela- 
tions that exist between electric circuits and 
magnets. 

Magnetism. — That branch of science which 
treats of the nature and properties of mag- 
nets and the magnetic field. (See Field, 
Magnetic) 

A property or condition of matter attended 
by the existence of a magnetic field. 

Magnetism, Ampere's Theory of A 

theory or hypothesis proposed by Ampere, to 
account for the cause of magnetism, by the 
presence of electric currents in the ultimate 
particles of matter. 



(0)(O)iP^ O o r, O 




° O O^O o O 




Fig- 379- Unmagnetized 
Bar {after Ampere). 



Fig. 380. Magnetized 
Bar {after Ampere). 



This theory assumes: 

(1.) That the ultimate particles of all magneti- 
zable bodies have closed electric circuits in which 
electric currents are continually flowing. 

(2.) That in an unmagnetized body these cir- 
cuits neutralize one another because they have 
different directions. 

(3.) That the act of magnetization consists in 
such a polarization of the particles as will cause 
these currents to flow in one and the same direc- 
tion, magnetic saturation being reached when all 
the separate circuits are parallel to one another. 

(4.) That coercive force is due to the resistance 
these circuits offer to a change in the direction 
of their planes. 

Fig s - 379 an d 380 show the circ^ar paths of 
some of these circuits. Fig. 379 shows the as- 



Mag.] 



345 



[Mag. 



sumed condition of an unmagnetized bar. Fig. 
380 the assumed condition of a magnetized 
bar. 

A careful inspection of the figures will show that 
in a magnetized bar all the separate currents flow 
in the same direction. All the circuits except 
those on the extreme edge of the bar will, there- 
fore, have the currents flowing in them in opposite 
directions to that in their neighboring circuits, 
and, therefore, will neutralize one another . There 
will remain, however, a current in a circuit on the 
outside of the bar, which must therefore be re- 
garded as the magnetizing current. 

Guided by these considerations, Ampere pro- 
duced a coil of wire, called a solenoid, which is 
the equivalent of the magnetizing circuit assumed 
by his theory. 

It therefore follows that an electric current sent 
through a coil of insulated wire surrounding a 
rod or bar of soft iron, or o'her readily magnet- 
izable material, will make the same a magnet. A 
"magnet so produced is called an electro-magnet. 
(See Magnet, Electro.} 

The magnetizing coil is called a helix or sole- 
noid. {See Solenoid, Electro-Magnetic.) 

The polarity of the magnet depends on the 
direction of the current, or on the direction of 
winding of the helix or solenoid. (See Solenoid, 
Sinistrorsal. Solenoid, Dextrorsal.) 

The improbability of an electric current con- 
tinually flowing in a circuit without the expendi- 
ture of energy, has led, perhaps, the majority of 
scientific men to reject Ampere's theory of mag- 
netism. 

Lodge, however, does not agree with the ma- 
jority of physicists in regarding a constant flow 
of electricity through the molecules of magnetiza- 
ble substances as an impossibility. On the sup- 
position that the atoms or molecules possess 
no resistance, the current would flow through 
them forever. He says: " To all intents and pur- 
poses certainly atoms are infinitely elastic, and 
why should they not also be infinitely conducting ? 
Why should the dissipation of energy occur, in 
respect to an electric current circulating wholly 
inside an atom ? There is no reason why it 
should." 

Magnetism, Animal A term some- 
times applied to hypnotism or artificial som- 
nambulism. 

Magnetism, Earth's, Theories as to Cause 
Of The various theories or hypotheses 



respecting the cause of the earth's magnet- 
ism. 

Any theory or hypothesis which shall satisfac- 
torily explain the cause of the earth's magnetism 
must account for the following phenomena, viz.: 

(1.) Variations in the intensity of the earth's 
magnetic field. 

(2.) Variations in the earth's magnetic inclina- 
tion, declination and intensity. 

The following hypotheses have been proposed: 

1st. That the earth's magnetism is due to the 
circulation round the earth of electric currents 
produced by differences of temperature which the 
earth's surface acquires from exposure to the sun 
during its rotation. 

As the earth rotates from west to east, the area 
of greatest heat would move round the earth in 
the opposite direction, or from east to west. If 
now those differences of temperature could pro- 
duce, in a manner not as yet explained, thermo- 
electric currents circulating round the earth from 
east to west, such currents would produce, in the 
Northern Hemisphere of the earth, south mag- 
netic polarity, and in the Southern Hemisphere 
north magnetic polarity, which would account for 
the magnetic polarity of the earth. 

Differences in the intensity of the earth's mag- 
netic field, and in the inclination and direction of 
its lines of magnetic force, would 1 e explained, 
according to this hypothesis, by the differences in 
the amount of the solar radiation at different 
times. 

The objection to this theory is to be found in 
the fact that by far the larger part of the earth's 
surface at the Equator is composed of water, so 
that the differences of potential at such parts, 
produced by the differences of temperature, are 
not readily set up in the earth's crust, if, indeed, 
they are set up at all. 

2d. That the earth's magnetism is due to in- 
duction from an already magnetized sun. This 
theory was brought forward by Secci and others. 
It is not generally credited. 

3d. A theory proposed by Biglow, which ac- 
counts for the earth's magnetism by rotation in 
the magnetic field of the sun's light and radia- 
tion. 

Biglow believes that the earth's magnetism is 
due to its rotation in the magnetic field of the 
sun's light. As the sun's light illumines one-half 
of the earth's surface, the earth's rotation causing 
different portions of the surface to pass through 



Mag.] 



346 



[Mag* 



this illumined area, produces, in Prof. Biglow's 
opinion, those differences in the direction and in- 
tensity of the magnetic lines of the earth's field 
that correspond to differences in the earth's mag- 
netic intensity, declination and inclination. 

It will be observed that in all these theories the 
sun is the prime factor in the production of the 
earth's magnetism. 

The evident connection between the earth's 
magnetism and the solar radiation is established 
from the well known connection between the so- 
called magnetic storms and variations in the in- 
tensity of the earth's magnetism. 

Magnetic storms are always attended by out- 
bursts of solar energy, known technically as 
sun-spots. A series of observations on the num- 
bers and frequency of sun-spots, plotted in the 
form of a curve, the ordinates of which represent 
the times of occurrence of the spots and the 
abscissas, the number of such spots, prove that 
such curve agrees, in a remarkable manner, with 
a similar curve representing the variations of the 
earth's magnetic field. 

An evident connection, too, exists between the 
earth's magnetism and the prevalence of the 
aurora borealis. 

Magnetism, Electro — Magnetism 

produced by means of electric currents. 

The discovery by Oersted, in 1820, of the ac- 
tion of an electric current on a magnetic needle, 
was almost immediately followed by the simul- 
taneous and independent discoveries by Arago 
and Davy, of the method of magnetizing iron 
by the passage of an electric current around it. 

These observations were first reduced to a 
theory by Ampere. (See Magnetism, Ampere' 's 
Theory of. Magnet, Electro.) 

Magnetism, Ewing's Theory of A 

theory of magnetism oroposed by Prof. 
Ewing, based on the assumption of originally 
magnetized particles. 

Ewing's theory of magnetism assumes that the 
ultimate particles of matter are naturally mag- 
netic and possess polarity. In this respect Ewing's 
theory agrees with the theories of Hughes and 
Weber. Ewing does not believe, however, in the 
necessity for the assumption of any arbitrary re- 
straining or constraining force to the movements 
of these ultimate magnetic particles other than 
those due to their own mutual magnetic attractions 
and repulsions. He assumes that in a magnet, 



the centres about which the molecular magnets 
rotate are maintained at constant distances from 
one another, save only as they are affected by the 
action of strain. 

He has experimentally demonstrated the prin- 
ciples of his theory by means of a model in which 
a number of small magnetic needles are so sup- 
ported as to be capable of free motion in a hori- 
zontal plane, when under varying magnetic 
forces. 

According to Ewing, "magnetic hysteresis" 
is not the result of any quasi-fnctional resistance 
to molecular rotation, but arises from a molecule 
moving from one position of stable equilibrium to 
another position of stable equilibrium through a 
position of unstable equilibrium. "This pro- 
cess," says Ewing, " considered mechanically, is. 
not reversible. The forces are different for the 
same displacement, going and coming, and there- 
is dissipation of energy. In the model, the energy 
thus expended sets the little bars swinging, and 
their swings take some time to suboide. In the 
actual solid, the energy which the molecular 
magnet loses as it swings through unstable posi- 
tions, generates eddy currents in surrounding 
matter. Let the magnets of the model be 
furnished with air vanes to damp their swings 
and the correspondence is complete." 

In Hughes' modification of Weber's theory of 
magnetism, it was held, that when magnetized 
iron was suddenly demagnetized by torsion or 
flexure, it lost its magnetization because the mo- 
lecular magnets came to rest in closed chainr. wmch 
produced no external effects. Experimentation 
with Ewing's model of a magnet shows that when 
the separate magnets after having been placed in 
any particular grouping are permitted to come to 
rest free from any external magnetic force, they do 
not arrange themselves in closed chains, but in 
general the tendency appears to be the formation 
of lines consisting of two, three or more magnets 
each member of a line being strongly controlled 
by its next member in that line, tut influenced 
by the neighbors which lie off the line on either 
side. 

The fact that a given force, suddenly applied, 
produces more magnetic induction than when 
gradually applied, and leaves less residual mag- 
netism when suddenly than when gradually re- 
moved, is presumably due to the inertia of the 
molecules. 

The influence of mechanical vibration in in- 
creasing the magnetic susceptibility and decreas- 



Mag.] 



347 



[Mag. 



ing the magnetic retentiveness, is ascribed by 
Ewing to the fact that the vibrations cause 
periodic variations in the distances between the 
centres of rotation of the magnetic molecules; 
thus making the molecular magnets respond more 
readily to changes of magnetic force during the 
time they are moving away from one another, 
when their magnetic stability is less, but also in- 
creasing the ease with which they respond to 
changes of magnetic force, by causing them to 
swing. 

Ewing discusses the theoretical effects of tem- 
perature on magnetism as follows, viz.: Suppose 
a moderate magnetizing force to be applied so 
that nothing like saturation is obtained, if now 
the temperature be raised; then 

(i.) The magnetic permeability increases until 
the temperature reaches a certain (high) critical 
value. 

(2.) At this temperature there is suddenly an 
almost complete disappearance of magnetic 
quality. 

He explains these facts as follows, viz.: An 
increase of temperature by increasing the distance 
between the molecular centres causes a decrease 
in their stability. 

The loss of magnetic qualities, when a certain 
temperature is reached, is, he believes, due to the 
fact that at such temperatures the magnetic 
molecules are set into actual rotation, when, 
naturally, all traces of polarity would disappear. 

Ewing's theory of magnetism also accounts to 
a considerable extxnt for the effects of stress and 
consequent elastic strain on the magnetic qualities 
of iron, nickel and cobalt. 

The following general summary of his theory 
is taken mainly from Prof. Ewing's original 
articles as published in the Journal of the Society 
of Arts: 

(i.) That in considering the magnetization of 
iron and other magnetic metals to be caused by 
the turning of permanent molecular magnets, we 
may look simply to the magnetic forces which 
the molecular magnets exert upon one another as 
the cause of their directional stability. There is 
no need to suppose the existence of any quasi- 
elastic directing force, or any quasi-frictional re- 
sistance to rotation. 

(2. ) That the intermolecular magnetic forces are 
sufficient to account for all the general character- 
istics of the process of magnetization, including 
the variations of susceptibility which occur as 
the magnetizing force is increased. 



(3.) That the intermolecular magnetic forces 
are equally competent to account for the known 
facts of retentiveness and coercive force, and the 
characteristics of cyclic magnetic processes. 

(4. ) The magnetic hysteresis and the dissipation 
of energy which hysteresis involves are due to 
molecular instability, resulting from intermolec- 
ular magnetic actions, and are not due to any- 
thing in the nature of frictional resistance to the 
rotation of the molecular magnets. 

(5 . ) That this theory is wide enough to admit an 
explanation of the differences in magnetic quality 
which are shown by different substances, or by 
the same substance in different states. 

(6.) That it accounts in a general way for the 
known effects of vibration, of temperature, and 
of stress, upon magnetic quality. 

(7 ) That, in particular, it accounts for the 
known fact that there is hysteresis in the relation 
of magnetism to stress. 

(8.) That it further explains why there is in 
magnetic metals hysteresis in physical quality- 
generally with respect to stress. 

(9.) That, in consequence, any (not very small)) 
cycle of stress occurring in a magnetic metal in- 
volves dissipation of energy. 

It can be demonstrated by means of experi- 
ments with a model constructed according to.f 
Ewing's hypothesis, that this hypothesis comes/ 
nearer than any which had been proposed before 
in explaining the following effects: 

(1.) The behavior of a piece of iron when, 
placed in a magnetic field whose strength is made: 
to pass through a cycle of changes. 

(2.) That nearly all reversals of sign on the- 
change of the magnetizing force are accompanied, 
by small changes in. the magnetization. 

(3.) That apiece of iron submitted to vibra- 
tions or mechanical shocks, is magnetized and ; 
demagnetized more readily and with a smaller, 
hysteresial area than if it had remained undis- 
turbed by vibrations. 

(4.) The phenomenon of "time lag " in mag- 
netization. 

(5.) The phenomena of stress, both those which, 
occur when a body has first been placed in a- 
magnetic field and the stress made to vary, and: 
those which occur when a body is first placed in 
a constant stress and the magnetizing force is 
made to vary. 

(6.) The effects of heat on magnetization, both 
as regards the effect of comparatively low heatine 
on increase of magnetic susceptibility, and the. 



Mag.l 



348 



[Mag. 



effect of excessive heating to decrease the sus- 
ceptibility. 

The author is indebted for the above summary 
of demonstrable facts to a paper recently read be- 
fore the Electrical Section of the Franklin Insti- 
tute, by Prof. Henry Crew. 

Magnetism, Flux or Flow of The 

quantity of magnetism, or the number of 
lines of force which pass in any magnetic 
circuit under a given magneto-motive force, 
against a given magnetic reluctance. 

Magnetism, Galvano A term some- 
times used for electro-magnetism. 

Electro-magnetism is by far the preferable 
term, and is almost universally used in the United 
States. 

Magnetism, Horizontal Component of 

Earth's (See Component, Horizontal, 

of Earth's Magnetisin) 

Magnetism, Hughes' Theory of A 

theory propounded by Hughes to account for 
the phenomena of magnetism apart from the 
presence of electric currents. 

Hughes' theory, or, more strictly speaking, 
hypothesis of magnetism, though very similar to 
that of Ampere, does not assume the improbable 
condition of a constantly flowing electric current. 

Hughes 1 hypothesis assumes: 

(i.) That the molecules of matter, and, per- 
haps, more probably, the atoms, possess naturally 
opposite magnetic polarities, which are respect- 
ively -f- and — , or N and S. 

(2.) That these molecules, when arranged in 
closed chains or circuits, are capable of neutral- 
izing one another so far as external action is con- 
cerned. 



n s n 



7 

nf 



n s " » '"^j 



n\ 






I 

y s 



n s 



Fig. 381. Closed Molecular Chain. 

Two such arrangements or groupings are 
shown in Figs. 381 and 382. It will be observed 
that the magnetic chain or circuit is complete, 



and that, therefore, the substance can possess no 
magnetic properties so far as external action is 
concerned. 

«« n s n 8 n s n a n s n s n s n s n s 

-HI4I4H4H;^{HH+- 

■ ra an 8 n an an a n a n s n an s n 

Pig- 382. Closed Groupings. 

(3.) That the act of magnetization consists in 
such a rotation of the molecules that a polariza- 
tion of the substance is effected — that is, the 
molecules are rotated on their axes so that one set 
of poles tend to point in one direction and the 
other set of poles in the opposite direction. 

Partial magnetization consists in partial polari- 
zation. Magnetic saturation is reached when the 
polarization is complete. (See Saturation, Mag- 
netic.) 

Coercive force is the resistance the body offers 
to the polarization or rotation of its molecules. 
(See Force, Coercive.) 

Hughes' hypothesis of magnetism would ap- 
pear to be strengthened by the following facts: 

(1.) A bar of steel or iron is sensibly elongated 
on being magnetized. This would naturally re- 
sult if the molecules be supposed to be longer in 
one direction than in any other. 

(2.) A tube, furnished at its ends with plates of 
flat glass and filled with water containing finely 
divided magnetic oxide of iron, is nearly opaque 
to light when unmagnetized, but will permit some 
light to pass through it when magnetized. 

(3.) A magnet, if cut at its neutral point, will 
possess opposite polarities at the cut ends; and, 
no matter to what extent this subdivision is car- 
ried, the particles will still possess opposite polar- 
ities. 

These facts are, however, also explained by 
Ampere's hypothesis of magnetism, with, how- 
ever, the improbable assumption of a constantly 
flowing current in each molecule. 

The following experiment by Von Betz tends 
somewhat to confirm Hughes' hypothesis: 

He placed a powerful horseshoe magnet in a 
solution of iron and deposited a bar or plate of 
metallic iron between the poles by electrolysis. 
Here the molecules, at the time of their deposi - 
tion, were subjected to a polarizing force which 
tended to place them all in the same direction, 
and, as the solution from which they were ob- 
tained permitted great freedom of motion, they 
were all presumably deposited in lines parallel to 
one another. When this bar of iron was subse 



Mag.] 



349 



[Mag. 



quently magnetized it was found to be much more 
powerful in comparison to its size than any other 
magnet. 

Mr. Shelford Bidwell has shown that the act of 
magnetization produces a shortening rather than 
a lengthening of the magnetizable material. 
When the magnetization is moderate there is a 
true lengthening of the material, but when a 
more powerful magnetizing force is exerted a 
true contraction or shortening is observed. 



% 




Fig. 383. Bidwell Apparatus. 

The Bidwell apparatus is shown in Fig. 383. 
The bar of iron to be magnetized is shown at 
R R. The magnetization is obtained by means of 
the coil of wire C. The upper end of the bar 
presses against the rod L, fulcrumed at F. The 
other end of the bar bears against a pivoted 
mirror M, from which a spot of light is reflected. 

In the case of the magnetization of nickel, the 
experiments of Bidwell showed the existence of 
contraction for both weak and strong currents. 
This contraction is much greater than in the case 
of iron. 

Magnetism, Lamellar Distribution of 

— The distribution of magnetism in 

magnetic shells. 

A term sometimes applied to such a dis- 
tribution of magnetism in a plate, that the 
magnetized particles are arranged with their 
greatest length in the direction of the thick- 
ness of the plate, so that the poles are situ- 
ated at the faces of the plate, and conse- 
quently the extent of such polar surfaces is 
great when compared with the thickness of 
the plate. 

The term lamellar distribution of magnetism is 
used in contradistinction to solenoidal distribution. 
(See Magnetism, Solenoidal Distribution of .) 

A thin sheet or disc of magnetized material 
whose opposed extended faces are of opposite 



magnetic polarities, and the extent of whose sur- 
face is very great as compared with its thickness, 
is sometimes called a tnagnetic shell. 

The field produced by a magnetic shell is ex- 
actly similar to that produced by a closed voltaic 
circuit, the edges of the space inclosed by which 
correspond to the edges of the magnetic shell. 

The magnetic intensity, or the number of lines 
of force per unit area of cross-section, is equal 
over all parts of the surface of a simple magnetic 
shell. 

A magnetic shell may be conceived as consist- 
ing of a very great number of short, straight 
magnetic needles, placed side by side, with their 
north poles terminating at one of the faces of the 
sheet and their south poles at the opposite face, 
the breadth of the sheet being very great as com- 
pared with its thickness. Such a distribution of 
magnetism is known as a lamellar distribution. 

Magnetism, Residual The magnet- 
ism remaining in the core of an electro-mag- 
net on the opening of the magnetizing cir- 
cuit. 

The small amount of magnetism retained 
by soft iron when removed from any mag- 
netizing field. 

When hard iron or steel is removed from a mag- 
netizing field it retains nearly all its magnetism. 
Such magnetism is also, in reality, residual mag- 
netism, but the term is generally limited to the 
case of soft iron. 

Magnetism, Solenoidal Distribution of 

— A term sometimes applied to such 

a distribution of magnetism in a bar that 
the magnetized particles are arranged with 
their poles in the direction of the length of the 
bar, the ends of which are of opposite mag- 
netic polarities, and the extent of whose sur- 
faces is small as compared with the length 
of the bar. 

The term solenoidal distribution is used in con- 
tradistinction to lamellar distribution. (See Mag- 
netism, Lamellar Distribution of. ) 

Magnetism, Strength of A term 

sometimes used in the sense of intensity of 
magnetization. (See Magnelizatio?i, Diten- 
sity of) 

The term, strength of magnetism, is sometimes 
u-ed for flux or quantity of magnetism. 

Intensity of magnetization, is the preferable 
term. 



Mag.] 



350 



[Mag. 



Magnetism, Terrestrial A name 

applied to the magnetism of the earth. 

Terrestrial magnetism has been ascribed to a 
variety of causes. (See Magnetism, Earth's, 
Theories as to Cause of. ) 

Magnetism, Vertical Component of 

Earth's (See Component, Vertical, 

of Earth's Magnetism?) 

Magnetite. — Magnetic oxide of iron, or 
Fe 3 4 , found in nature, as an ore or mineral. 

Lo^e-stone consists of pieces of magnetized 
magnetite. 

Magnetizable. — Capable of being magnet- 
ized after the manner of a paramagnetic sub- 
stance like iron. 

The most magnetizable metals are iron, nickel, 
cobalt and manganese. (See Paramagnetism.) 

Magnetization. — The act of calling out or 
of endowing with magnetic properties. 

Magnetizable substances are magnetized by 
being placed in magnetic fields. (See Field, Mag- 
netic. Magnetization, Methods of. ) 

The act of initial magnetization is not exactly 
the same as the act of subsequent magnetization. 

A piece of steel, which has once been magnet- 
ized and subsequently demagnetized, is a thing en- 
tirely distinct, as regards its magnetization, from 
a piece of steel which has never before been mag- 
netized, and such a piece can never be placed ex- 
actly in the same position as regards a magnet- 
izing force, unless it is actually melted and recast, 
or, perhaps, maintained for a comparatively long 
time at a white heat. 

Magnetization, Anomalous The 

magnetization obtained from an oscillatory 
discharge, such as that of a Leyden jar. 

In 1842, Henry described the real character of 
anomalous magnetization, and showed that there 
was nothing anomalous in such magnetization, but 
rather in the fact that the magnetizing currents 
possessed no simple direction. He remarks on 
this subject as follows: 

"This anomaly, which has remained so long 
unexplained, and which, at first sight, appears at 
variance with all our theoretical ideas of the con- 
nection of electricity and magnetism, was, after 
considerable study, satisfactordy referred to an 
action ot the di?charge of a Leyden jar which had 
never before been recognized. The discharge, 



whatever may be its nature, is not correctly rep- 
resented (employing the simplicity of Franklin) 
by the single transfer of an imponderable fluid 
from one side of the jar to the other ; the phe- 
nomena require us to admit the existence of a 
principal discharge in one direction and then 
several reflex actions backward and forward, each 
more feeble than the preceding, until the equi- 
librium is obtained. All the facts are shown to 
be in accordance with the hypothesis, and a ready- 
explanation is afforded by it of a number of phe- 
nomena which are to be found in the older works 
on electricity, but which have until this time re- 
mained unexplained. ' ' 

Magnetization by Touch. — The produc- 
tion of magnetism in a magnetizable sub- 
stance by touching it with a magnet. 

There are three methods of magnetization by 
touch, viz.: 

(1.) Single touch. 

(2.) Separate touch. 

(3.) Double touch. 

In single touch, the magnetization of a bar of 
iron or other magnetizable material is effected by 
the touch of a single magnet. 

In Single Touch, the magnetizing magnet is 
drawn over the bar to be magnetized from end to 
end and returned through air, the stroke being 
repeated a number of times. The end of the 
bar the magnet leaves is magnetized oppositely 
to the magnetizing pole. 

By some writers the method of single touch is 
described as that effected 
by placing the magnet- 
izing magnet N S (Fig. 
384) on the middle of 
the bar to be magnetized, 
and drawing it to the 
end and returning 
through the air as be- 
fore, and then reversing 

the pole, placing it on Fi S- 384. Magnetization 
the middle of the bar by Single Touch. 

and drawing it towards the other end. The 



+ N 



S — 



3EJ HZ 




Fig. 38 5. Magnetization by Separate Touch. 

former would, however, appear to be the better 
use of the term single touch. 

In Separate Touch, two magnetizing bars- are 
placed with their opposite poles at the middle 



Mag.] 



351 



LMai 



of the bar to be magnetized and drawn away from 
each other towards its ends, as shown in Fig. 
385. This motion is repeated a number of times, 
the poles being each time returned through the 
air. 

In the above, as in all cases of magnetization 
by touch, better effects are produced, if the bar 




Fig. 386. Magnetization by Double Touch. 

to be magnetized is rested on the opposite poles 
of another magnet, or, as shown in Fig. 386, 
placed near them. 

In Double Touch the two magnets are placed 
with their opposite poles together on the middle 
of the bar to be magnetized, as shown in Fig. 
386. They are then moved to one end of the bar, 
-when, instead of re??ioving them and passing them 
back through the air to the other end, they are 
moved over the surface of the. bar to be magnet- 
ized to the other end, and these to-and-fro mo- 
tions are repeated a number of times. The mo- 
tion is stopped at the middle of the bar, when the 
magnetizing magnets are moving in the opposite 
direction to that at which they began to move. 
This insures an equal number of strokes to the 
two halves of the bar. The method of double 
touch produces stronger magnetization than 
either of the other methods, but does not effect 
such an even distribution of the magnetism, and 
therefore is not applicable to the magnetization 
of needles. 

A variety of double touch is shown in Fig. 387, 
where four bars, to be magnetized, are placed in 
the form of a hollow rectangle, with only their 
ends touching at their edges, the angular spaces 




Fig. 387. Magnetization by Double Touch. 

at the corners being filled with pieces of soft iron. 
The horseshoe magnet N S, is then moved around 
the circuit several times in the same direction. 
This is believed t > produce a more uniform mag- 



netization than the ordinary method of double 
touch. 

Magnetization, Co-efficient of A 



number representing the intensity of magnet- 
ization produced in a magnetizable body, 
divided by the magnetizing force H. 

Calling k, the co-efficient of magnetization ; I, 
the intensity of the resulting magnetization, and 
H, the magnetizing force producing it, then 



k = 



The co-efficient of magnetization is sometimes 
called the magnetic susceptibility. 

A paramagnetic body when placed in a mag- 
netic field concentrates the lines of magnetic force 
on it, or causes them to pass through it. The 
intensity of the magnetization so produced de- 
pend?, therefore, 

(1.) On the intensity of the magnetizing field. 

(2.) On the ability of the metal to concentrate 
the lines of force on it; that is, on the nature of 
the metal, or on its magnetic permeability. (See 
Permeability, Magnetic. Paramagnetism. Dia- 
magnelism. ) 

The intensity of magnetization will, therefore, 
be equal to the product of the co- efficient of mag- 
netization and the intensity of the magnetizing 
field. It will, also, of course, depend on the area 
of cross-section of the magnetized body. 

The co-efficient of magnetization of paramag- 
netic bodies is said to be positive, and that of dia- 
magnetic bodies to be negative, because paramag- 
netic bodies concentrate the lines of magnetic 
force on them, while diamagnetic bodies appear 
to repel the lines of force. (See Para??iagnetic. 
Piamagnetic.) 

Magnetization, Critical Current of 

■ — The current at which any certain or definite 
effect of magnetization is produced. 

Magnetization, Intensity of — A 

quantity showing the intensity of the magnet- 
ization produced in a substance. 

A quantity showing the intensity with 
which a magnetizable substance is mag- 
netized. 

The intensity of magnetization depends: 

(1.) On the intensity of the magnetizing field. 

(2.) On the magnetic permeability, or on the 
conducting power of the substance for lines of 
magnetic force. 



Mag.] 



352 



[Mag. 



The greater the strength of the magnetizing 
field, and the greater the magnetic permeability, 
the greater is the intensity of the magnetization 
produced. 

When, therefore, a magnetizable substance is 
placed in a magnetizing field, the intensity of the 
magnetization will depend on the magnetic sus- 
ceptibility of the substance; that is, on the ratio of 
the induced magnetization to the magnetizing force 
producing it. 

Soft iron has a high co-efficient of magnetization, 
or its magnetic susceptibility is high. (See Sus- 
ceptibility, Magnetic. Magnetization, Co-efficient 
of.) 

The intensity of magnetization through a sub- 
stance is measured by dividing the magnetic 
moment by the magnetic volume. 

If a bar of soft iron is placed with its greatest 

length extending in the direction of the lines of 

force in a magnetic field, it will have induced in 

it a certain intensity of magnetization which may 

be expressed as follows: 

m . 1 
Intensity of Magnetization = y Q | u , = k H, 

where m, equals the strength of the magnet ; I, its 
length ; k, the co-efficient of magnetization, and 
H, the intensity of the magnetizing field. — (S. P. 
Thompson.) 

" The moment of a magnet, or of any element 
of a magnet, may be considered numerically to be 
made up of two factors, one, its volume, and the 
other its intensity of magnetization, or simply 
its magnetization, and hence, for a uniformly mag- 
netized small linear needle, we may define the 
intensity of its magnetization by saying that it has 
magnetic moment of unit volume." — {Fleming.) 

Magnetization, Maximum A term 

sometimes used for magnetic saturation. 

Urquhart states, as the result of numerous ex- 
periments, that the number of lines of magnetic 
force that usually pass through a bar of soft iron 
I square centimetre in area of cross-section, when 
magnetized to a maximum, is equal to 32,000. 
Ewing gives the number in the particular case of 
a very extraordinary magnetization as being equal 
to 45,350 per square centimetre area of cross- 
section. 

Magnetization, Methods of Mag- 
netization effected either by induction from 
another magnet, or by means of induction by 
an electric current. 



The substance to be magnetized is brought into 
a magnetic field, so that the lines of magnetic 
force pass through it. All methods of magnet- 
ization may be divided into methods of magnetiza- 
tion by touch and magnetization by the electric 
current. (See Magnetization by Touch.) 

Magnetization, Permanent, Intensity of 

A term employed for the intensity of 

a permanent magnetization produced in hard 
steel, as distinguished from the magnetization 
temporarily produced in soft iron. (See Mag- 
netization, Intensity of.) 

Magnetization, Temporary, Intensity of 

■ The intensity of the magnetization 

temporarily induced in a bar of soft iron, as 
distinguished from permanent magnetization 
induced in hard steel. (See Magnetization y 
Intensity of.) 

Magnetization, Time-Lag of A lag 

which appears to exist between the time of 
action of the magnetizing force and the ap- 
pearance of the magnetism. 

The time which must elapse in the case of 
a given paramagnetic substance before a mag- 
netizing force can produce magnetization. 

In the opinion of some physicists there is no 
such thing as a true magnetic time-lag, the ap- 
parent time-lag being due entirely either to hys- 
teresis or to eddy currents. According to them, 
.while the magnetizing force is increasing, it pro- 
duces, in the iron, reversely-directed surface- 
eddy-currents, which produce a reversed or 
opposed magnetizing force in the more deeply 
seated layers of the iron, the time-lag being due 
to the interval which is required for these eddy 
currents to die away and thus permit the mag- 
netizing force to produce its full magnetization. 

According to others, however, a true time- 
lag does exist entirely apart from the existence of 
surface-eddy-currents. 

Magnetize. — To endow with magnetic 
properties. 

Magnetized. — Endowed or impressed with 
magnetic properties. 

Magnetizing. — Causing or producing mag- 
netism. 

Magneto-Blasting Machine. — (See Ma- 
chine, Magneto-Blasting.) 



Mag.] 



353 



[Mag. 



Magneto-Electric Bell.— (See Bell, Mag- 
neto-Electric^) 

Magneto-Electric Brake.— (See Brake, 
Magneto-Electric.) 

Magneto-Electric Call-Bell.— (See Call- 
Bell, Magneto- Electric?) 

Magneto-Electric Faradic Apparatus.— 

(See Apparatus, Faradic, Magneto-Elec- 
tric) 

Magneto-Electric Induction.— (See In- 
duction, Magneto-Electric.) 

Magneto-Electric Machine.— (See Ma- 
chine, Magneto-Electric) 

Magneto-Electric Medical Apparatus.— 
(See Apparatus, Magneto-Electric Medi- 
cal) 

Magneto-Electricity,— (See Electricity, 
Magneto.) 

Magnetograph.— The permanent record 
obtained from the action of a self-recording 
magnetometer. (See Magneto7neter % Self- 
Recorditig.) 

Magnetometer.— An apparatus for the 
measurement of magnetic force. 




The magnetometer shown in Fig. 388, consists 
of a magnetized bar suspended by two wires pass- 
ing over a pulley, as shown. The magnet is held 
by the frame S S, provided with a graduated scale 
K. The mirror S, is supported by a vertical post 
attached to the frame, and serves to reflect a scale 
placed below a distant reading telescope. This 
form of magnetometer, is called the bifilar mag- 
netometer, and was the one used by Gauss in his 
study of the earth's magnetism. 

A variety of forms have been given to delicate 
magnetometers. Some are self-recording. (See 
Magnetometer, Self- Recording.') 

Magnetometer, Differential A form 

of magnetometer in which the principles of the 
differential galvanometer, as applied to the 
electric circuit, are applied to the magnetic 
circuit. 

The differential magnetometer of Eickemey er is 
shown in Figs. 389 and 390. Its principles of 
operation will be understood from the following 
considerations. 

Referring to Fig. 389. Suppose Fj and F 2 are 
two electromotive forces connected in series, and 
x and y, two resistances to be compared. Each of 
the resistances x and y, is shunted respectively by 
two conductors a and b, whose resistance we 
wish to compare. Since the action of each of 
them on the galvanometer G, is opposite, its nee- 
dle remains at zero, when the current in a, is 
equal to the current in b. 

If, instead of electric circuit, we take the idea 
of magnetic circuit or the number of lines of 
magnetic force, and instead of potential difference, 




Fig 388, Magneto7neter, 

In some magnetometers the magnetic force is 
measured by the torsion of a wire, as in the tor- 
sion balance. (See Balance, Coidomb's Torsion.) 



Fig. 38 Q. Eickemeyer's Differential Magnetometer. 

magneto-motive force, and instead of electric re- 
sistance, magnetic resistance, we have the princi- 
ples on which the Eickemeyer differential magnet- 
ometer is founded. 

The magnetic circuit of the differential magnet- 
ometer consists of two pieces of soft iron, shaped 



Mag.] 



354 



Mag. 



as shown at F ± and F g , Fig. 390. A magnetic 
coil C, surrounds the middle portion of each cir- 
cuit as shown. The operation as described by 
Mr. Chas. Steinmetz, from whom the above de- 
scription is mainly taken, is as follows, viz.: "The 
front part s ± of the left iron piece becomes south, 
and the back part ^ north polarity; the front 
part of the right iron piece n 2 becomes north, and 
the back part south; and the lines of magnetic 
force travel in the front from the right to the left, 
from n g to Sj ; in the back the opposhe way, from 
the left to the right, or from n x to s 2 , either 
through the air, or, when n 2 and s 1 , or n t and s 2 , 
are connected by a piece of magnetizable metal, 
through this and through the air. 

In the middle of the coil C, stands a small soft 
iron needle with an aluminum indicator, which 
plays over a scale K, and is held in a vertical 
position by the lines of magnetic force of the coil 
C, itself, deflected to the left by the lines of mag- 
netic force traversing the front part of the instru- 
ment from n 3 to s l5 deflected to the right by the 
lines traversing the back from nj to s 2 . This 
needle shows by its zero position that the mag- 
netic flow through the air in front from n a to s x 
has the same strength as the magnetic flow in the 
back from n 1 to s 2 through the air. 

Now we put a piece of soft iron x on the front 
of the instrument. A large number of lines go 
through x, less through the air from n 3 to Sj ; but 
all these lines go from n, to s 3 through the air 
at the back part of the magnetometer, the front 
part and back part of the instrument being con- 
nected in series in the magnetic circuit. There- 
fore the needle is deflected to the right by the 
magnetic flow in the back of the instrument. 

Now, we put another piece of iron, y, on the 
Iback part of the instrument, then equilibrium 
would be restored as soon as the same number of 
lines of magnetic force go through x, as through 
y, because then also the same number of lines go 
through air in the front as in the back. As will 
be noted, the air here takes the place of the resist- 
ances a and b, influencing the galvanometer 
needle G, as in the diagram Fig. 389. 

The operation of the instrument is exceedingly 
simple and is as follows : Into the coil C, an elec- 
;tric current is sent which is measured by the am- 
meter A, and regulated by the resistance-switch 
H. Then the needle, which before had no fixed 
position, points to zero. 

Now, we lay the piece of iron, the magnetic 
properties of which we want to determine, on the 



back part of the instrument. The needle is de- 
flected to the left. On the front of the instrument 
we put Norway iron rods of known cross-section 
and known conductivity, until equilibrium is 
again restored. Then the iron in the front has 
the same magnetic resistance as the iron in the 
back, and the ratio of the cross- sections gives 
directly the ratio of the conductivities ; so that 
by a single reading the magnetic conductivity of 
any piece of iron can be compared with that of 
the Norway iron standard. 

For absolute determinations, the iron is turned 
off into pieces of exactly 4 square centimetres 
cross-section and 20 centimetres in length, both 
ends fitting into holes in large blocks of Norway 
iron, which are laid against the pole pieces of the 
magnetometer, so that the transient resistance 
from pole face to iron is eliminated. 




Fig. 3 QO. Eickemeyer's Differential Magnetometer. 

Magnetometer, Self-Recording* 



self-recording apparatus, by means of which 
the daily and hourly variations of magnetic 
needles in the earth's field, at any locality., are 
continuously registered. 

The self-recording magnetometer employed in 
the observatory at Kew, consists essentially of 
means of obtaining a photographic record of a 
spot of light reflected from a mirror, attached to 
the needle whose variations are to be recorded. 
The photographic record is received on a strip of 
sensitized paper, maintained in uniform and con- 
tinuous motion by means of suitable clock-work. 
The record so obtained is called a magneto- 
graph. 

Magneto-Motive Force. — (See Force > 
Magneto-Motive.) 



Mag.] 



355 



[Mak. 



Magneto-Motive Force, Absolute Unit of 

-(See Force, Magneto-Motive, Abso- 



lute Unit of.) 
Magneto-Motive Force, Practical Unit of 

(See Force, Magneto-Motive, Prac- 
tical Unit of.) 

Magneto-Optic Rotation.— (See Rotation, 
Magneto-Optic) 

Magnetophone. — A species of magnetic 
siren in which sounds are produced in an 
electro-magnetic telephone by the periodic 
currents produced in its coils by the rotation 
of a perforated metallic disc in a magnetic 
field. 

As the speed of the disc increases, the pitch of 
the note increases. The apparatus was invented 
by Prof. Carhart, in 1883. A similar apparatus 
is useful in studying the distribution of the mag- 
netic field of a dynamo-electric machine. In this 
-case, a small, thin coil of insulated wire is held in 
the different regions around the machine, while 
the telephone is held to the ear of the observer. 
Magnetic leakage, or useless dissipation of lines 
of magnetic force outside the field proper of the 
machine, is at once rendered manifest by the 
musical note caused by variations in the intensity 
of the field. 

Since the intensity of the note heard will vary 
according to the intensity of the field, and also 
according to the position in which the coil is held, 
such a coil becomes a magnetic explorer, and by 
its use the distribution and varying intensity of an 
irregular field can be ascertained. Its use is 
especially advantageous in proportioning dynamo- 
electric machines and electric motors. (See Ex- 
plorer, Magnetic. ) 

Magneto-Receptive Device.— (See Device, 
Magneto-Receptive.) 

Magneto-Static Current Meter. — (See 
Meter, Current, Magneto-Static) 

Magneto-Static Screening.— (See Screen- 
ing, Magneto-Static) 

Magneto-Statics.— (See Statics, Magneto) 

Magneto-Therapy.— (See Therapy, Mag- 
neto) 
Main Battery. — (See Battery, Main.) 
Main-Battery Circuit. — (See Circuit, 
Main-Battery) 



Main, Electric The principal con^ 

ductor in any system of electric distribution. 

Main Feeder. — (See Feeder, Standard or 
Main) 

Main Fuse. — (See Fuse, Main) 

Main, House A term employed in 

a system of multiple incandescent lamp dis- 
tribution for the conductor connecting the 
house service conductors with a centre of 
distribution, or with a street main. 

Main-Line Cut-Out. — (See Cut-Out, Main- 
Line) 

Main, Street In a system of incan- 
descent lamp distribution the conductors ex- 
tending in a system of networks through the 
streets from junction box to junction box, 
through which the current is distributed 
from the feeder ends, through cut-outs, to 
the district to be lighted, and from which 
service wires are taken. 

Main, Sub A name sometimes 

given to the distributing conductor that is 
connected directly to a main. 

The branch nearest the main. (See 
Branch.) 

Main Wire. — (See Wire, Main) 

Mains of Electric Railroads.— The wires 
or conductors used for carrying the current 
from the feeders through the tap wires to the 
trolley wires. 

Make. — A completion of a circuit. 

Make-and-Break. — The periodic alternate 
completion and opening of a circuit. 

Make-and-Break, Automatic A 

term sometimes employed for such a combi- 
nation of contact points with the armature of 
any electro-magnet, that the circuit is auto- 
matically made and broken with great rapidity. 

An automatic make-and-break is used in most 
forms of electric alarms in connection with some 
form of electric bell. (See Alarm, Electric.) 

It is also used in the Ruhmkorff induction coil 
in order to produce the variations in the primary 
circuit. (See Coil, Induction.) 

Make-Induced Current. — (See Current, 
Make-Induced) 



Mak.] 



356 



[Mar. 



Making the Primary. — (See Primary, 
Making the.) 
Mallet, Electro-Magnetic Dental 

— (See Dental-Mallet, Electro-Magnetic.) 
Mangin Projector. — (See Projector, Man- 

gin.) 

Man-Hole, Compartment, of Conduit 

— A man-hole provided with suitably sup- 
ported shelves or compartments, guarded by- 
locked doors that protect different cable sec- 
tions. 

Man-Hole of Conduit. — An opening of 
sufficient size to admit a man, communi- 
cating from the surface of the roadbed with 
an underground conduit. 

Manipulator, Breguet's The send- 
ing instrument employed by Breguet in his 
system of step-by-step or dial telegraphy. 
(See Telegraphy, Step-by-Step.) 

Manometei .-— An apparatus for measuring 
the tension or pressure of gases. 

Manometers are either mercurial or metallic. 
Mercurial manometers are of two classes, viz., 
manometers with free air and manometers with 
compressed air. 

Manometers measure the pressure of gases 
either in atmospheres, i. e., in multiples or deci- 
mals of 15 pounds to the square inch, or in inches 
of mercury. 

Map or Chart, Inclination A chart 

or map on which lines are drawn, showing 
the lines of equal dip or inclination, or the 
isoclinic lines. 

An inclination chart is shown in Fig. 391. 

It will be seen that the magnetic equator, or 
line of no dip, does not correspond with the geo- 
graphical equator, being generally north of the 
equator in the Eastern Hemisphere, and south of 
it in the Western. The figures attached to the 
lines indicate the value of the angle of dip. 

Map or Chart, Isodynamic A map 

of the earth on a mercator's projection, on 
which isodynamic lines are drawn. 

An isodynamic chart is shown in Fig. 392. It 
will be observed that the isodynamic lines do not 
exactly coincide with the isoclinic lines, since the 
line of least magnetic intensity does not correspond 
with the line of the magnetic equator. 

The point of least magnetic intensity is found at 



about lat. 20 degrees S., and Ion. 35 degrees W. 
The point of greatest magnetic intensity is found 
at about lat. 52 degrees N. and Ion. 92 degrees 
W. 

Another, though weaker point of magnetic in- 
tensity, is found in Siberia. These are distin- 
guished from the true magnetic poles by the term 
Poles of Intensity. 

The Poles of Verttcity, as determined by the 
dipping needle, and the Poles of Intensity, as de- 
termined by the needle of oscillation, therefore do 
not coincide in the Northern Hemisphere. 

Map or Chart, lsogonal A term 

sometimes used for an isogonic map or chart. 

Map or Chart, Isogonic A chart 

on which the isogonal lines are marked. 

An isogonic map or chart is sometimes called 
a declination map or chart . 

In the declination or variation chart, shown in 
Fig. 393, the region of western declination is in- 
dicated by the shading. There is a remarkable 
oval patch in the northeastern part of Asia, in 
which the declination is west. A similar oval of 
decreased inclination is seen in the Southern 
Pacific. 

The entire earth acts like a huge magnet with 
south magnetic polarity in the Northern Hemi- 
sphere. 

It is not known whether the earth possesses 
but a single pair of magnetic poles or more 
than a single pair. The variations in the dec- 
lination, and in the intensity of its magnetism, 
due to the position of the sun, as well as the 
marked magnetic disturbances that accompany 
the occurrence of sun spots, would appear to con- 
nect the earth's magnetism in some manner with 
the solar radiation. (See Magnetism, Earth's, 
Theories as to Cause of.) 

Marine Galvanometer. — (See Galvanom- 
eter, Marine.) 

Mariner's Compass. — (See Compass, Azi- 
muth.) 

Marked Pole of Magnet.— (See Magnet, 
Marked Pole of.) 

Markers. — Colored flags, or signal lights, 
generally green, displayed in systems of 
block railway signaling at the ends of 
trains, in order to avoid accidents from trains 
breaking in two. (See Railroads, Block 
System for.) 



Mar.] 



357 



[Mar. 




Mar.] 



353 



[Mar. 




Mar.] 



359 



[Mar. 




Mas.] 



3C0 



[Mat. 



Mass. — The quantity of matter contained 
in a body. 

Mass must be carefully distinguished from 
weight. The weight of a given quantity of 
matter depends on the attraction which the earth 
possesses for it, and this, on the earth's surface, 
varies with the latitude, being greatest at the 
poles and least at the equator. It also varies 
with different elevations above the level of the sea. 
The mass, however, is the same under all circum- 
stances, whether for different latitudes or alti- 
tudes, on the earth's surface. 

Mass Attraction. — (See Attraction, Mass.) 

Mass, Magnetic A quantity of mag- 
netism which at unit distance produces an 
action equal to unit force. 

Mass, Unit of The quantity of mat- 
ter which under certain conditions will balance 
the weight of a standard gramme or pound. 

The gramme is equal to the one-thousandth 
part of a piece of platinum called the kilogramme, 
deposited as a standard in the archives of the 
French Government, and intended to be equal to 
the mass of I cubic centimetre of water at the tem- 
perature of its maximum density. 

Massage. — A treatment for the purpose 
of effecting changes in general nutrition or 
action of particular parts of the body, by 
kneading, rubbing, friction, etc. 

Massage, Electro The application 

of electricity to the body during its massage. 

Connections are established between the patient 
and a battery by connecting one electrode of a 
source to the kneading instrument, and the other 
electrode to the body of the patient. 

Masses, Electric — A mathematical 

conception for such quantities of electricity 
as at unit distance will produce an attrac- 
tion or repulsion equal to unit force. 

Electrical masses are assumed to be equal when 
they produce on two identical bodies of small 
dimensions charges of the same electric force. 

Master Clock.— (See Clock, Master.) 
Materials, Insulating Non-con- 
ducting substances which are placed around a 
conductor, in order that it may either retain 
an electric charge, or permit the passage of 



an electric current through the conductor 
without sensible leakage. 

Various gases, liquids or solids may be em- 
ployed as insulators. A very high vacuum affords 
the best known insulation. 

Matter. — Anything which occupies space in 
three directions and prevents other matter from 
simultaneously occupying the same space. 

Matter is composed of atoms, which unite to 
form molecules. (See Atom. Molecule. ) 

Matter, Elementary Matter which 

cannot be decomposed into simpler matter. 

Varieties of elementary matter are called 
elements. (See Element.) 

Matter, Kinetic Theory of A 

theory which assumes that the molecules of 
matter are in a constant state of motion or 
vibration towards or from one another in 
paths that lie within the spheres of their 
mutual attractions or repulsions. 

The molecules of gases have great freedom 
of motion, and are so far removed from one 
another as to be but little, if any, influenced by 
their mutual attractions. They are therefore 
assumed to move in straight lines with very great 
velocity until they collide against one another, or 
against the sides of the containing vessel, when 
they are reflected and again move in straight lines 
in a new path. 

Matter, Radiant, or Ultra-Gaseous 

— A term proposed by Crookes for the 
peculiar condition of the gaseous matter which 
constitutes the residual atmospheres of high 
vacua. 

This is now generally recognized as a fourth 
state of matter, these four states being: 

(i.) Solid. 

(2.) Liquid. 

(3.) Gaseous. 

(4. ) Ultra-gaseous or radiant. 

The peculiar properties of radiant matter are 
seen in the mechanical effects of the localized 
pressures produced when such residual atmos- 
pheres are locally heated or electrified. 

In Crookes'' radio??ieter, vanes of mica, silvered 
on one face and covered with lampblack on the 
opposite face, are supported on a vertical axis so 
as to be capable of rotation and placed in a glass 
vessel in which a high vacuum is maintained. On 



Mat.] 



361 



[Mat. 



exposing the instrument to the radiation from a 
candle or gas flame, a rapid rotation takes place. 
(See Radiometer, Crookes\) 

The explanation is as follows : The lampblack 
covered surfaces absorb the radiant heat, and be- 
coming heated, the molecules of gas in the residual 
atmosphere are shot violently from them, and by 
their reaction drive the vanes around in the 
opposite direction to that from which they are 
thrown off. The molecules are also shot off from 
the silvered surfaces, but, as these are cooler, the 
effect is not as great as at the blackened surfaces. 

In a gas, at ordinary pressure, the heated sur- 
faces are also bombarded by other molecules of 
the gas, but in high vacua the mean free path of 
the molecules is so great that there is no interfer- 
ence, a Croohes' layer existing between the vanes 
and the walls of the glass vessel. (See Zayer t 
Crookes\) 

When a Crookes' tube is furnished with suit- 
able electrodes, and electric discharges are sent 
through it between these electrodes, a stream of 
molecules is thrown off in straight lines from the 
surface of the negative electrode. 

Some of the effects of this molecular bombard- 
ment are seen by the use of the apparatus shown 
in Fig. 394. When the positive and negative 




Fig. 3Q4> Effects of Molecular Bombardment. 

terminals are arranged as shown, the paths of the 
molecular streams are seen as luminous streams 
whose directions are those shown in the figures. 

The figure on the left shows the path taken in 
a low vacuum. Streams pass from the negative 
electrode to each cf the positive electrodes. 

The figure on the right shows the discharge in 
a hi^h vacuum. Here the streams pass off at 
right angles to the lace of the negative electrode, 



and proceed therefrom in straight lines, inde- 
pendently of the position of the positive electrode. 
Since, therefore, the negative electrode at a, is in 
the shape of a concave mirror, the luminous 
particles converge to a focus near the centre of 
the glass vessel, and then diverge to the opposite 
wall. 

Refractory substances placed at such a focus of 
molecular bombardment, as shown in Fig. 395, are 
rendered incandescent. 

In a similar manner, phosphorescent substances 
exposed to such molecular streams emit a beauti- 




Fig. sgj. Forces of Molecular Bombardment. 

ful phosphorescent light. (See Phosphorescence, 
Electric.) 

Matter, Thomson's Hypothesis of 



A hypothesis as to the structure of matter 
suggested by Sir William Thomson, in order 
to show how the extremely tenuous ether 
might possess rigidity. 

The fact that the ether, although a fluid sub- 
s'ance, possesses the properties of a rigid solid, 
has given no little trouble to physicists. Thomson 
explains this rigidity of the ether as being due to 
a rapid motion in its fluid particles. 

A perfectly flexible rubber tube filled with 
water or other fluid, possesses, when at rest, a 
very great degree of flexibility. When in mo- 
tion, however, the tube becomes more and more 
rigid, as the flow increases in rapidity. Thorn- 



Mat.] 



362 



[MLed. 



son imagines the ether to be set in motion in 
minute vortex rings, and shows that a readily 
movable fluid body, like ether, once set in such 
motion should possess the properties of a solid. 
In a perfect fluid, such as ether, these vortex 
rings once formed, would be practically imperish- 
able or indestructible. 

Thomson regards the atoms of matter as con- 
sisting of such vortex rings. Vortex rings can be 
formed in the air by cutting a circular aperture 
in the end of a pasteboard box, and tapping 
sharply against the end of the box. In order to 
render the rings visible, the box may be previously 
filled with smoke. 

Vortex rings formed in smoky air differ from 
vortex rings in the ether, in the fact that air is 
not a perfect fluid, while ether is. Air vortex 
rings increase in size and decrease in energy. 
Vortex rings of the ether would not vary in size. 

According to Thomson's vortex theory of 
matter, the atoms of matter are the same as the 
ether which surrounds them. They cannot be 
produced in ether by any known way ; therefore, 
they cannot be manufactured, or, as it were, 
created. Nor, on the other hand, can they be 
destroyed; in other words, they are indestruct- 
ible. They are elastic, capable of definite vibra- 
tions, possess all the properties of matter save, in 
the opinion of some, the very important prop- 
erty of gravitation. As Prof. Lodge points out,, 
the fact that this property is not present should 
cause Sir William Thomson's theory of matter to 
be accepted with considerable hesitation. 

Matthiessen's Metre-Gramme Standard. 

— (See Metre-Gramme Standard, Matthies- 
sen's?) 

Matthiessen's Mile Standard. — (See Mile 
Standard, Matthiessen's?) 

Matting, Invisible Electric Floor 

— A matting or other floor covering, provided 
with a series of electric contacts, which are 
closed by the passage of a person walking 
over them. 

This matting is provided as an adjunct to a 
system of burglar alarms. The electric bell or 
annunciator, connected with the different con- 
tacts, is disconnected during the day-time, or while 
the rooms are occupied. (See Alarm, Burglar.) 

Maximum Magnetization. — (See Mag- 
netization, Maximum.) 



Mclntire's Parallel Sleeve Telegraphic 
Joint. — (See Joint, Telegraphic, Mclntire's 
Parallel Sleeved) 

Measurements, Electric — Deter- 
minations of the values of the electromotive 
force, resistance, current, capacity, energy, 
etc., in any electric circuit. 

Electric measurements may be either qualitative 
or quantitative. 

In qualitative electric measurements the rela- 
tive values only are obtained; in quantitative 
measurements the actual values are obtained. 

Mechanical Alarm, Electric (See 

Alarm, Electro-Mechanical.) 

Mechanical Electric Bell. — (See Bell, 
Electro-Mechanical?) 

Mechanical Equivalent of Heat. — (See 
Heat, Mechanical Equivalent of.) 

Mechanical Mine. — (See Mi?ie, Mechani- 
cal.) 

Mechanical Throwback Indicator. — 
(See Indicator, Mechanical Throwback?) 

Medical Induction Coil. — (See Coil, In- 
duction Medical?) 

Medical Magneto-Electric Apparatus. — 
(See Apparatus, Magneto-Electric Medi- 
cal.) 

Medium, Anisotropic A medium 

in which equal stresses do not produce equal 
strains when applied in different directions. 

A medium, homogeneous in structure like 
crystalline bodies, but possessing different 
powers of specific inductive capacity in differ- 
ent directions. 

An eolotropic medium. (See Medium, 
Eolotropic.) 

The latter term is used to distinguish it from 
an isotropic medium. (See Medium^ Isotropic.) 

Medium, Eolotropic A medium 

in which equal stresses do not produce the 
same strains when applied in different direc- 
tions. (See Medium, Isotropic?) 

Medium, Electro-Magnetic Any 

medium in which electro-magnetic phenom- 
ena occur. 

The medium through which electro-magnetic 
waves are propagated is now universally re- 



Med.] 



363 



[Met. 



garded as the luminiferous or universal ether. 
(See Electricity \ Hertz's Theory of Electro-Mag- 
netic Radiations or Waves.) 

Medium, Isotropic A medium in 

which equal stresses applied in any direction 
produce equal strains. 

A transparent medium which possesses the 
same optical or electric properties in all di- 
rections. 

An optically homogeneous, transparent 
medium. 

Such media are called isotropic to distinguish 
them from anisotropic or eolotropic, or those in 
which equal stresses produce unequal strains in 
different directions. (See Medium, Anisotropic. 
Medium, Eolotropic.) 

Meg or Mega (as a prefix).— 1,000,000 
times ; as, megohm, 1,000,000 ohms ; mega- 
volt, 1,000,000 volts. 



Megaloscope, Electric 



-An appara- 



tus for the medical exploration of the cavities 
of the body. 

The light necessary for exploration is obtained 
from a small incandescent lamp placed at the 
extremity of a tube, suitably shaped for introduc- 
tion into the special organ for which it is devised. 
The organ so illumined throws its light on a 
prism, by means of which the light is caused to 
pass through a series of lenses by which it is 
viewed. 

Megavolt. — 1,000,000 volts. 

Megohm. — i,ooo,oco ohms. 

Meidinger Yoltaic Cell.— (See Cell, Vol- 
taic, Meidinger) 

Memory, Magnetic A term pro- 
posed by J. A. Fleming for coercive force. 

Soft iron has but a feeble memory of its past 
magnetization. 

Mercurial Connection. — (See Connection, 
Mercurial.) 

Mercurial Contact. — (See Connection, 
Mercurial.) 

Mercurial Temperature Alarm. — (See 
Alarm, Mercurial Temperature) 

Mercury Break. — (See Break, Mercury) 

Mercury Cup. — (See Cup, Mercury) 



Meridian, Astronomical A great 

circle passing through any point in the 
heavens, and the North and South poles of: 
the heavens. 

The astronomical meridian corresponds to the 
geographical meridian. The former is considered 
as passing around the dome of the heavens; the 
latter, around the surface of the earth. In order- 
to locate any point in the heavens, a great circle 
of the heavens is caused to pass through that point 
and through the astronomical North and South- 
poles. 

Meridian, Geographical The geo- 
graphical meridian of a place is a great circle 
passing through that place and the North and 
South geographical poles of the earth. 

Meridian, Magnetic The magnetic 

meridian of any place is the meridian which 
passes through the poles of a magnetic needle 
at that place when in a position of rest under 
the free influence of the earth's magnetism. 

The plane of the magnetic meridian at any place 
is a vertical plane parsing through the poles of a 
magnetic needle in a position of rest under the 
free influence of the earth's magnetism at that 
place. 

The magnetic meridian may be regarded as the 
vertical plane in which a freely suspended mag- 
netic needle comes to rest in the earth's magnetic; 
field. 

Meridional.— Pertaining to the meridian.. 
Message Wire.— (See Wire, Message) 
Messenger Call.— (See Call, Messenger) 
Metallic Arc— (See Arc, Metallic) 
Metallic Circuit— (See Circuit, Metal- 
lic) 

Metallic Coating.— (See Coating, Metal- 
lie) 

Metallic Conducting Joint.— (See Joint,, 
Metallic Conducting) 

Metallic Contact.— (See Contact, Metal- 
lic) 

Metallic Electric Conduction. — (See 
Conduction, Electric, Metallic) 

Metallization. — The rendering of a non- 
conducting surface electrically conducting by 
covering it with a metallic coating, so as to 



Met.] 



364 



[Met. 



enable it to readily receive a metallic coating 
by electro-plating. (See Plating, Electro?) 

Metallochromes. — A name sometimes 
given to Nobili's rings. (See Rings, No- 
Dili's.) 

Metalloid. — A name formerly applied to a 
non-metallic body, or to a body having only 
some of the properties of a metal, as carbon, 
boron, oxygen, etc. 

The term is now but little used. 

Metallurgy, Electro That branch 

of applied science which relates to the elec- 
trical reduction or treatment of metals. 

Metallurgical processes effected by the 
agency of electricity. 

Electro-Metallurgy embraces : 

(i.) The reduction of metals from their ores, 
either directly during fusion by the heat of the 
voltaic arc, or the heat of incandescence, or by 
the electrolysis of solutions of their ores, or ores 
in the fused state. (See Electrolysis. Enrnace y 
Electric.) 

(2.) Electroplating. 

(3.) Electrotyping. 

The application of electricity to the reduction 
of metals is carried on in the electric furnace for 
the reduction of the aluminium ores, for example. 

Metals, Electric Deflagration of 

The volatilization of metals by electric in- 
candescence. 
Metals, Electric Kefining of — 

Purifying metals by means of electricity. 

Different methods are employed for the electric 
refining of metals. They are generally electro- 
lytic in character. 

Metals, Electrical Protection of 

The protection of a metal from corrosion by 
placing it in connection with another metal, 
which, when exposed to the corroding liquid, 
vapor or gas, will form with the metal to be 
protected the positive element of a voltaic 
couple. 

The negative element of a voltaic couple is 
protected by the presence of the positive element, 
which is alone corroded. This method has been 
adopted with considerable success to electrically 
protect metals from corrosion. 

The following are examples of this protection : 

(1.) Davy proposed to protect the copper 



sheathing of ships from corrosion by attaching 
pieces of zinc to the copper sheathing. This 
succeeded too well, since the copper salts which 
were formerly produced, and acted as a poison 
to the marine plants and animals, being now 
absent, permitted these organisms to thrive to 
such an extent as to seriously foul the ship's 
bottom. 

(2.) A ring of zinc attached to a lightning rod, 
near its points, has, it is claimed, the power of 
protecting the points from corrosion. 

(3.) Iron bars of railings, if sunk or embedded 
in zinc, are preserved from corrosion near the 
junction of the two metals, but if sunk in lead are 
rapidly corroded, because iron is electro-positive 
to lead, but electro-negative to zinc. 

(4.) Tinned iron rapidly corrodes or rusts 
when the iron is exposed to the atmosphere by a 
scratch or abrasion, because the iron is electro- 
positive to tin. Nickel-plated iron, for the same 
reason, rusts rapidly on the exposure of an 
abraded surface. 

(5.) Zinced or galvanized iron, or iron covered 
with a deposit of zinc, is protected from corro- 
sion because the zinc, being positive to iron, can 
alone be corroded, and the zinc is also protected 
in part by the coating of insoluble oxide that is 
formed. 

Meteorites. — Aerolites. (See Aerolites?) 



— (See Ampere- 



Meter, Ampere - 

Meter. Ammeter?) 

Meter, Current A term now ap- 
plied to an electric meter or galvanometer 
which measures the current in amperes, as 
distinguished from one which measures the 
energy in watts. 

This term is sometimes loosely applied to a 
galvanometer. 

The term galvanometer is preferable. (See 
Galvanometer.) 

Meter, Current, Magneto-Static A 

current meter in which a small steel magnet, 
or system of magnets, is suspended at the 
centre of the uniform magnetic field produced 
by the combined influence of two coils and 
two systems of powerful permanent magnets. 

Meter, Electric Any apparatus for 

measuring commercially the quantity of elec- 
tricity that passes in a given time through 
any consumption circuit. 



Mct.J 



365 



[Met. 



Electric meters are constructed in a great 
variety of forms; they may, however, be ar- 
ranged under the following heads : 

(i, ) Electro-Magnetic Meters, or those in which 
the current passing is measured by the electro- 
magnetic effects it produces. 

In such meters the entire current may pass 
through the meter. 

(2.) Electro-Chemical Meters, or those in which 
the current passing is measured by the electroly- 
tic decomposition it effects. 

In these meters, a shunted portion only of the 
current is usually passed through a solution of a 
metallic salt, and the current strength calculated 
from the amount of electrolytic decomposition 
thus effected. 

(3.) Electro- Thermal Meters, or those in which 
the current passing is measured by a movement 
effected by the increase in temperature of a resist- 
ance through which the current is passed, or by 
the amount of a liquid evaporated by the heat 
generated by the current. 

(4.) Electric- Ti??ie Meters, or those in which 
no attempt is made to measure the current that 
passes, but in which a record is kept of the num- 
ber of hours that an electric lamp, motor or 
other electro-receptive device is supplied with 
current. 

Edison's electric meter is of the second class. 
It consists of two voltameters, or electrolytic cells, 
containing zinc sulphate, in which two plates of 
chemically pure zinc are dipped. The current 
that passes is determined by the amount of the 
variation in weight of the zinc plates. To deter- 
mine this, the plates are weighed at stated in- 
tervals : one plate every month, the other plate, 
"which is intended to act as a check on the first, 
only once in three months. Some difficulty has 
been experienced in the employment of meters of 
this class, from the variations in the value of the 
shunt resistance, due to variations in the condi- 
tion and temperature of the electrolytic cell. 
The use of a compensating resistance, however, 
ba<=. it is claimed, removed this objection. (See 
Voltameter.} 

Meter, Electric-Time An electric 

meter in which the current passing is esti- 
mated by recording the number of hours that 
an electric lamp or other electro-receptive 
device is supplied with a known current. 
(See Meter, Electric) 



Meter, Electro-Chemical 



-An elec- 



tric meter in which the current passing is 
measured by the electrolytic decomposition it 
effects. (See Meter, Electric?) 

Meter, Electro-Magnetic An elec- 
tric meter in which the current passing is 
measured by the electro-magnetic effects it 
produces. (See Meter, Electric?) 

Meter, Electro-Thermal An elec- 
tric meter in which the current passing is 
measured by means of the heat generated by 
the passage of the current through a resist- 
ance. (See Meter, Electric) 

Meter, Energy A term sometimes 

applied to a watt meter. (See Meter, 
Watt) 



Meter, Milli-Ampere 



-An ampere 



meter graduated to read milli-amperes. 

Meter, Watt An instrument gener- 
ally consisting of a galvanometer constructed 
so as to measure directly the product of the 
current, and the difference of potential. 

Since the watt is equal to the product of the 




Fig. 396. Watt Meter. 

current by the electromotive force, if the current 
and electromotive force are simultaneously meas- 
ured, their product gives directly the watts. 
The scale reading of a watt meter may be grad- 
uated so as to give the watts directly. 

A watt meter consists essentially of a thick wire 
coil, placed in series in the circuit whose electric 
power is to be measured, and a thin wire coil 



Met.J 



366 



LMic. 



placed in a shunt around the circuit to be meas- 
ured. These two coils, instead of acting on a 
needle, act on each other, and the amount of this 
deflection will, therefore, be proportional to the 
watts present. 
A form of watt meter is shown in Fig. 396. 

Method, Deflection A method em- 
ployed in electrical measurements, as distin- 
guished from the zero method, in which a 
deflection, produced on any instrument by a 
given current, or by a given charge, is utilized 
for determining the value of that current or 
charge. 

The conditions remaining the same, the same 
Current or charge will produce the same deflection 
at any time. Different deflections produced by 
currents or charges, the values of which are un- 
known, are determined by certain ratios existing 
between the deflections and the currents or 
charges. These ratios are determined experi- 
mentally by the calibration of the instrument. 
(See Calibrate.) 

Deflection methods are opposed to zero or null 
methods, in which latter a balance of opposite 
electromotive forces, or a proportionally equal 
fall of electric potential, is ascertained by the 
failure of a delicately poised needle to be moved 
by a current or a charge. 

Method, Null or Zero Any method 

employed in electrical measurements, in which 
the values of the electromotive force in volts, 
the resistance in ohms, or the current in am- 
peres, or other similar units, are determined 
by balancing them against equal values of the 
same units, and ascertaining such equality, not 
by the deflections of the needle of a galvano- 
meter, or of an electrometer, but by the ab- 
sence of such deflections. 

The advantage of zero methods is iound in the 
fact that the galvanometer or electrometer may 
then be made as sensitive as possible, which is not 
otherwise the case, since great deflections are 
generally to be avoided, especially in tangent 
galvanometers. (See Galvanometer. Electrom- 
eter.) 

Method of Magnetization by Touch. — 

(See Magnetization by Touchy 

Methven's Screen.— (See Screen, Metk- 
veri's.) 



Metre Bridge.— (See Bridge, Metre.) 
Metre Candle. — (See Candle, Metre.) 
Metre-Gramme Standard, Matthiessen's 

A unit of resistance. 

The resistance of a wire one metre in 
length, and of such a diameter as would cause 
the wire to weigh one gramme. 

One metre-gramme of pure hard drawn copper 
has a resistance of .1469 B. A. units at zero de- 
grees C. as determined by Matthiessen (Phil. 
Mag., May, 1865). 

Metre-Millimetre A resistance unit 

of length of a wire or other conductor of the 
length of one metre and of the area of cross- 
section of one square millimetre. 

According to the report of the Committee of the 
American Institute of Electrical Engineers cf 1890, 
on a Standard Wiring Table, a metre-millimetre 
of pure soft copper wire has a resistance of .02057 
B. A. units at zero degrees C. From the corre- 
sponding term, milfoot, millimetre-metre would 
appear to be the preferable term. 

Metric Horse-Power.— (See Horse-Power, 

Metric.) 

Metric System of Weights and Meas- 
ures. — (See Weights and Measures, Metric 
System of.) 

Mho. — A term proposed by Sir Wm. 
Thomson for the practical unit of conductiv- 
ity. 

Such a unit of conductivity as is equal to 
the reciprocal of 1 ohm. 

The conducting power is equal to JL or the 

R. 
reciprocal of the resistance. 

The word mho, as is evident, is obtained by in- 
verting the order of sequence of the letters in the 
word ohm. 

Mica. — A mineral substance employed as 
an insulator. 

Mica is a silicious mineral. It occurs of vary- 
ing degrees of transparency, and splits or cleaves 
readily into transparent laminse. It is a good 
non-conductor, is fairly fire -proof, and is not 
hydroscopic. 

Mica is used extensively in insulating the me- 
tallic segment of commutators of motors and 
dynamo-electric machines and in various other 
electric work. 



Mic] 



36? 



[Mil. 



Mica, Moulded 



-An insulating sub- 



stance consisting of finely divided mica made 
into a paste, with some fused insulating 
substance, and moulded into any desired 
shape. 

Finely divided mica mixed with gum-shellac 
rendered plastic by means of heat, forms a good 
insulating substance. 

Micro (as a prefix). — The one-millionth; 
as, a microfarad, the millionth of a farad ; a 
microvolt, the one-millionth of a volt. 

Micro-Farad. — (See Farad, Micro.) 

Micro-Graphophone. — A modified form of 
phonograph in which several independent 
non-metallic diaphragms are used instead of 
the single diaphragm of the phonograph. (See 
Graphophone, Micro.) 

Micrometer, Arc An apparatus for 

the accurate measurement of the length of a 
voltaic arc by means of a micrometer. 

The distance between two carbon electrodes — 
•one movable and the other fixed — placed inside a 
glass vessel, is accurately determined by means of 
a micrometer placed on the movable electrode. 
The operation is similar to that of the vernier 
wire gauge. 

Micrometer, Spark A term some- 
times applied to Hertz's electric resonator. 
{See Resonator. Electric?) 

Micron. — A measure of length. 

The one-millionth part of a metre. 

The micron is equal to .00004 of an inch, very 
nearly. 

Microphone. — An apparatus invented by 
Prof. Hughes for rendering faint or distant 
sounds distinctly audible. 

The microphone depends for its operation on 
variations produced in the resistance of the circuit 
of a battery, or other electric source, by means of 
a loose contact. These variations in the resist- 
ance are caused to produce corresponding move- 
ments in the diaphragm of a receiving telephone. 

The loose contact may take a variety of forms. 
Originally it was made in the form shown in Fig. 
397, in which a small piece of carbon E, pointed 
at both ends, is inserted in holes near the ends of 
-cross-pieces of carbon B and C. The thin upright 
board A, on which these are supported, acts as a 



sounding board or diaphragm, and its movements 
by sound waves are at once audible to a person 
listening at the receiving telephone. The walk- 
ing of a fly over the sounding board is heard as a 
loud sound. 

The forms of transmitting telephones invented 
by Reis, Edison, Blake, Berliner and others, are 
in reality varieties of microphones. 




Fig. 3Q7- Microphone. 

Microphone Relay. — (See Relay, Micro- 
phone?) 

Micro-Seismograph. — (See Seismograph, 
Micro?) 

Microtasimeter. — An apparatus invented 
by Edison to measure minute differences of 
temperature, or of moisture, by the resulting 
differences of pressure. 

A change of temperature, or moisture, is caused 
to produce variations in the resistance of a button 
of compressed lampblack, placed in the circuit of 
a delicate galvanometer. The apparatus, though 
of surprising delicacy, is scarcely capable of prac- 
tical application, from the fact that the resistance 
of the carbon does not resume its normal value on 
the removal of the pressure. 

Micro-Tolt.— (See Volt, Micro?) 

Mil. — A unit of length equal to the toW of 
an inch, or .001 inch, used in measuring the 
diameter of wires. 

Mil, Circular A unit of area em- 
ployed in measuring the areas of cross-sec- 
tions of wires, equal to .78540 square mil. 

The area of a circle one mil in diameter. 



Mil.] 



368 



[Min. 



One circular mil equals .000000785 square inch. 

The area of cross-section of a circular wire in 
circular mils is equal to the square of its diameter 
expressed in mils. (See Units, Circular.) 

Mil-Foot. — A resistance unit of length of 
one foot of wire or other conductor of one 
mil diameter. 

The resistance of a mil-foot of soft copper wire 
or wire 1 foot long and .001 of an inch in diam- 
eter is equal to 9.720 B. A. units at O degrees C. 

Mil, Square A unit of area em- 
ployed in measuring the areas of cross-sec- 
tions of wires, equal to .000001 square inch. 

One square mil equals 1.2732 circular mil. 

Mile, Nautical A knot, or a dis- 
tance of 6,087 feet, or very nearly 1.15 statute 
miles. 

The ytfuit of the earth's equatorial cir- 
cumference, or the -gV of a degree of longi- 
tude at the equator, or about 2,029 yards. 

A nautical or geographical mile being the 
stIott of 24,899 miles, has a value somewhat 
greater than that of the statute mile. 

Mile Standard, Matthiessen's A 

standard of resistance equal to the resistance 
of one mile of pure copper wire -rV inch in 
diameter at 15.5 degrees C. 

Matthiessen's mile standard has a resistance of 
13.59 B. A. units at 15.5 degrees C. 

Mile, Statute The ordinary unit of 

distance on land, equal to 5,280 feet. 

Milli (as a prefix). — The one-thousandth 
part. 

Milli-Ampere. — The thousandth of an am- 
pere. 

Milli-Calorie. — The smaller calorie. (See 
Calorie, Small.) 

Milli-Oerstedi— The one-thousandth of 
an Oerstedt. 

Mimosa Sensitiva. — A sensitive plant 
whose leaves fold or shut up when touched. 

The fibres of all the sensitive plants, such, for 
example, as the above, the Venus' Fly-trap, etc., 
like all muscular fibre, and indeed all protoplasm, 
suffer contraction when traversed by electric cur- 
rents. 

Mine, Electro-Contact —A sub- 
marine mine that is fired automatically on 
the completion of the current of a battery 



placed on the shore through the closing of 
floating contact points by passing vessels.. 
(See Mine, Submarined) 

Mine Exploder, Electro-Magnetic 

A form of electro-magnetic exploder. (See 
Exploder, Electro-Magnetic^) 

Mine, Mechanical A submarine 

mine that is fired when struck by a passing 
ship by the action of some contrivance con- 
tained within the torpedo itself, and having 
no connection whatever with the shore. 

Mine, Observation A variety of 

submarine mine that is fired when the 
enemy's vessels are observed to be within the 
destructive area of the mine. (See Mine, 
Submarine.) 

Various means are adopted for obtaining the 
current required for firing such mines. A suffi- 
ciently powerful battery is generally used. An 
electro-magnetic mine exploder may, under cer- 
tain circumstances, be employed. (See Mine 
Exploder, Electro-Magnetic.) 

Mine, Submarine A mass of gun- 
cotton or other explosive contained in a 
water-tight vessel and placed under water so 
as to be exploded on the passage over it of 
an enemy's vessel. 

A submarine mine is a stationary torpedo ar- 
ranged for the defense of a harbor. A harbor 
is protected by a number of mines which are so- 
arranged as to be readily exploded by the passage 
of an enemy's ship, but safely crossed by other 
vessels. 

Submarine mines consist essentially of gun- 
cotton or other explosives contained in water-tight 
vessels anchored in very carefully located posi- 
tions, and connected with the shore by means of 
cables. 

An operating-room at the shore end of the 
cable is furnished with batteries, measuring in- 
struments, contact keys, etc., etc., by means of 
which the mines can be exploded by the trans- 
mission of an electric current through the cables; 
or, the mines are furnished with automatic cir- 
cuit closers in which two central points are closed 
by the passage of the vessel. In ordinary times 
this current is too weak to ignite the fuse, and 
merely closes a relay in the operating-room, 
which in turn directs a current through a bell or 
indicator, but, of course, too weak to fire the fuse~ 



Min.] 



3G9 



[Mom. 



In times of war, however, the relay sends a 
current through the cable sufficiently strong to 
heat a platinum iridium fuse, ignite a fulminate of 
mercury cap, and thus, by the detonation of the 
primer of dry gun-cotton, explode the full charge 
of damp gun-cotton in the torpedo or mine. 

Mine, Subterranean A mass of 

gun powder, gun-cotton or other explosive, 
placed under ground in vessels suitable for 
protection against moisture, and fitted with 
electrically connected electric fuses, which are 
either exploded automatically by the move- 
ment of an enemy over them, or by an oper- 
ator placed at a safe distanse within an en- 
trenchment. 

Minute, Ampere One ampere flow- 
ing for one minute. (See Hour, Ampere.) 

Minute, Watt A unit of electrical 

work. 

The expenditure of an electrical power of 
one watt for one minute. 

The watt-minute is equal to 60 joules. This 
unit of electrical work is seldom used. 

Miophone. — An apparatus invented by 
Boudet based on the use of the microphone, 
and designed for the medical examination of 
the muscles. 

Mirror Galvanometer. — (See Galvanom- 
eter, Mirror?) 

Moist Electrode.— (See Electrode, Moist.) 

Moisture, Effect of, on Electrical Phe- 
nomena — The influence of moisture 

on the surfaces of insulators in causing the 
loss or dissipation of an electric charge. 

This loss is more rapid with negatively charged 
bodies than with those positively charged. 

Molar Attraction. — (See Attraction, 
Molar?) 

Molecular. — Pertaining to the molecule. 
(See Molecule?) 

Molecular Attraction. — (See Attraction, 
Molecular) 

Molecular Bombardment.— (See Bom- 
bardment, Molecular?) 

Molecular Chain.— (See Chain, Molecu- 
lar?) 



Molecular Currents.— (See Currents, 
Molecular or Atomic?) 

Molecular Currents, Induced (See 

Currents, Induced Molecular or Atomic?) 

Molecular Range. — (See Range, Molecu- 
lar?) 

Molecular Repulsion.— (See Repulsion 
Molecular?) 

Molecular Rigidity. — (See Rigidity, 
Molecular?) 

Molecular Theory of Muscle and Nerve 
Currents. — (See Theory, Molecular, of Mus- 
cle and Nerve Currents?) 

Molecule. — A group of atoms whose 
chemical bonds or affinities are mutually 
satisfied. 

The smallest quantity of a compound sub- 
stance that can exist as such. 

Water is a compound substance formed of two 
atoms of hydrogen combined with one atom of 
oxygen. The molecule of water, therefore, or 
the smallest quantity of water that can exist, must 
contain two atoms of hydrogen and one of oxygen. 

The molecule of hydrogen consists of two atoms 
of hydrogen. Since hydrogen is a monad, or an 
element whose atomicity is one, it can combine 
with one atom of hydrogen and form a molecule, 
since then its bonds will be fully satisfied. (See 
Atomicity?) 

Molecule, Closed-Magnetic Circuit of 

— (See Circuit, Closed-Magnetic, of 

Molecule?) 

Molecule, Gramme The weight of 

any substance taken in grammes numerically 
equal to the molecular weight. 

Moment, Magnetic The sum of the 

two forces of the directive couple multiplied 
by half the perpendicular distance between the 
directions of these forces ; or, in other words, 
the moment of a magnet is equal to its length 
multiplied by the intensity of the magnetism 
of one of its poles. (See Couple, Magnetic.) 

Moment of Couples.— (See Couple, Mo- 
ment of.) 

Momentary Current. — (See Current, Mo- 
mentary.) 

Momentum, Electro-Magnetic, of Sec- 
ondary Circuit A quantity equal to 



Mon.] 



370 



[Mot. 



the co-efficient of mutual induction, multi- 
• plied by the current strength in the primary, 
when the primary current is fully established. 
When the primary current is fully established, 
the number of lines of force which pass through 
the secondary circuit is equal to the co-efficient of 
mutual induction, multiplied by the strength of 
the primary current. 

Monophotal Arc-Light Regulator. — (See 
Regulator, Monophotal Arc-Light?) 
Mordey Effect.— (See Effect, Mordey) 
Morse Alphabet. — (See Alphabet, Tele- 
graphic : Morse's?) 

Morse Inker. — (See Inker, Morsel 
Morse Recorder. — (See Recorder, Morse?) 
Morse Register. — (See Register, Morse) 
Morse System of Telegraphy. — (See 
Telegraphy, Morse System of.) 

Morse's Telegraphic Alphabet. — (See Al- 
phabet, Telegraphic : Morse's?) 

Morse's Telegraphic Sounder. — (See 
Sounder, Morses Telegraphic?) 

Motion, Energy of A term some- 
times applied to actual or kinetic energy in 
contradistinction to potential energy. (See 
Energy, Actual) 

Motion, Simple-Harmonic Motion 

which repeats itself at regular intervals, taking 
place backwards or forwards, and which may- 
be studied by comparison with uniform mo- 
tion round a circle of reference. — {Daniell) 





> < 




f 










\\ 


R f 


3 C 


C 


) < 


j 





Fig. 398. Simple-Harmonic Motion. 

Motion which is a simple periodic function 
of the time. 

Suppose a pendulum be set swinging in a cer- 
tain path. If the path of such a pendulum, or, 
as it is generally called, a conical pendulum, be 



looked at from above or from below, it will appear 
to be circular; if observed from one side it will 
appear elliptical, and this elliptical path will ap- 
pear longer and narrower as the eye of the ob- 
server approaches the level of the plane in which 
the bob moves, when the bob will appear to 
travel backwards and forwards in a straight line. 
The bob will appear to be moving faster, when it 
is moving right across the field of view. 

Let the circle QCR (Fig. 398) be the path in 
which the bob moves, and let Q A, A B, B C, C o, 
etc., be equal distances in such path. Let the 
lines A a, B b, C c, o O, etc., be drawn perpendicu- 
lar to the line Q R. Then when looked at, with 
the eye on the level of the plane in which the bob 
travels, the line Q R, will be the path in which 
the bob appears to move backwards and for- 
wards, and the lines, Q a, a b, b c, c O, etc., will 
represent the spaces apparently traversed in 
equal intervals of time. 

The circle Q o R, is called the circle of refer- 
ence. 

Motion, Simple-Harmonic, Amplitude of 

The length of the swing from the 

median position to its extreme position, in 
either direction. 

The line O Q, or O R, in the circle of reference 
Q O R (Fig. 398). 

Motion, Simple-Harmonic, Negative Di- 
rection of The motion which a body, 

with a simple-harmonic motion, has when it 
appears to move from left to right. 

Motion, Simple-Harmonic, Period of 

— The interval of time which elapses between 
two successive passages of a moving particle, 
over the same point, in the same direction. 

The period of simple-harmonic motion repre- 
sents the time of one complete motion around a 
circle called the circle of reference. (See Motion, 
Simple -Harmonic. ) 

Motion, Simple-Harmonic, Phase of 

— The position of a point executing a simple 
harmonic motion, expressed in terms of the 
interval of time which has elapsed since 
such point last passed through the middle 
of its path in the positive direction. — {An- 
thony <Sn» Brackett.) 

The exact position of a particle executing a 
simple-harmonic motion for any instant of time 
can be readily expressed in terms of the phase. 



Mot] 



371 



[Mot. 



Motion, Simple-Harmonic, Positive 

Direction of The motion which a 

body moving in simple-harmonic motion has, 
when it appears to move from right to left. 

Motion, Simple-Periodic A term 

sometimes employed in the sense of simple- 
harmonic motion. (See Motion, Simple- 
Harmonic.) 

Motion, Simple-Sine —A term some- 
times employed in the sense of simple-har- 
monic motion. (See Motion, Si7npie-Har- 
monic.) 

Motograpli, Electro An apparatus 

invented by Edison whereby the friction of a 
platinum point against a rotating cylinder of 
moist chalk, is reduced by the passage of 
an electric current. 

This result is due to electrolytic action at the 
points of contact, varying the friction. 

The electro-motograph, though less certain in 
its action than an electro-magnet, may replace it 
in certain electric apparatus. 

The detailed construction of the electro-moto- 
graph will be understood from an inspection of 

Fig- 399- 

The lever A, pivoted with a universal joint at 
C, has a metallic point at its free extremity F, 
resting on a strip of moistened paper N, and held 
against it with some pressure by the action of the 
spring S. The paper N, rests on the metallic 
drum G, over which it is moved on the rotation 
of the drum by clockwork. A spring R, acts to 
move the lever A, in a direction opposite to that 
in which it tends to move by the rotation of the 
drum G. 

The main battery L, is connected at its negative 
pole to the point F, and at its positive pole, through 
the key K, to the metallic drum G. The local bat- 
tery L B, is connected through the sounder X, to 
the contacts D and X. 

When the key K, is open, the friction of F, on 
the paper N, is sufficient to move the lever A, to 
the right so as to close the circuit of the local 
battery, but when the key K, is depressed, the 
current of L, passing through the paper, decom- 
poses the chemicals with which it is moistened, 
lessens the friction of the point F, and permits the 
spring B, to draw the lever A, to the left, thus 
opening the circuit of the local battery L B. 

The movements of the key are therefore repro- 
duced by the armature of the electro-magnet X. 



An excellent loud speaking telephone has been 
devised by Edison on the principle of the electro- 
motograph. 




Fig. 399. Electro-Motograph. 

Motor, Compound-Wound An elec- 
tric motor whose field magnets are excited by 
a series and a shunt wire. (See Machine, 
Dynamo-Electric, Compound- Wound.) 

Motor, Differentially Wound A 

compound-wound motor, in which the cur- 
rent in the shunt coils opposes in its magnet- 
izing effects the current in a series coil, so 
that the efficient magnetizing effect produced 
is the difference in the magnetizing effect of 
the two coils. 

Motor, Electric A device for trans- 
forming electric power into mechanical 
power. 

All practical electric motors depend for their 
operation on the tendency to motion in a mag- 
netic field of a conductor canning a current or 
on magnetic attraction or repulsion. The entire 
magnetism may be produced by the current, or 
part may be obtained from permanent magnets, 
and the rest from electro-magnets. 

A dynamo-electric machine will act as a motor 
if a current is sent through it. Such a motor is 
sometimes called an electro-motor. The term 
electric motor would, however, appear to be the 
preferable one. 

In all cases the rotation is in such a direction as 
to induce in the armature an electromotive force 
opposed to that of the driving current ; this is 
therefore called the counter electromotive force. 

A magneto -dynamo, or a dynamo the field of 
which is obtained from permanent magnets, or a 
separately excited dynamo, will operate as a 
motor when a current is sent through its arma- 
ture, and will turn it in the opposite direction to 
that required to drive it in order to produce a 
current in the same direction. 

A series dyna?7io will operate as a motor when 



Mot.] 



372 



[Mot. 



a current is sent through it. If the current is 
sent through it in the opposite direction to that 
which it produces when in operation as a gener- 
ator, the polarity of the field is reversed and the 
dynamo will turn as a motor in the opposite direc- 
tion to that required to produce the current. If 
the current is reversed, the polarity of both the 
field and the armature is again reversed, and the 
dynamo still rotates as a motor in the opposite 
direction to that in which it is rotated as a 
generator. 

A series dynamo, therefore, always rotates as a 
motor in a direction opposite to that of its rotation 
as a generator. 

When, however, the polarity of the field only 
is reversed by changing the connection between 
the armature and the field, the rotation is in the 
same direction. 

A shunt dynamo operated as a motor will also 
turn in but one direction, but this direction is the 
same as that in which it turns when operating 
as a generator; for if the direction of the current 
in the armature is the same as in a generator, 
that in the shunt is reversed. 

A compound wound dynamo will move in a 
direction opposite to that of its motion as a gene- 
rator if the series part is more powerful than the 
shunt, and in the same direction if the shunt part 
is more powerful than the series. To use a com- 
pound-wound dynamo as a differential motor the 
connections need not be changed. For a cumu- 
lative motor it is necessary to reverse the connec- 
tions of the series coils. 

Alternating-Current Dynamo. — The current 
from an alternating-current dynamo, if sent 
through another similar alternating-current dy- 
namo running at the same speed, will drive it as a 
motor. Such a machine possesses the disadvan- 
tage of requiring to be maintained at a speed de- 
pending on that of the driving dynamo, and also 
that it requires to be brought to nearly this speed 
before the driving current is supplied to it. As a 
result of this last requirement, variations in the 
load are apt to stop the motor. Considerable 
improvements, however, are being introduced 
into alternate-current motors, by which these 
difficulties are almost entirely removed. 

An alternating current sent through any self- 
exciting dynamo -electric machine, such as a 
shunt or series machine, will drive it continu- 
ously as a motor. The sudden reversals in the 
magnetization of its cores will, however, unless 
\he cores are thoroughly laminated, set up power- 



ful eddy currents that will injuriously heat the 
machine, and there is also excessive sparking at 
the brushes. 

The reversibility of any dynamo -electric ma- 
chine, or its ability to operate as a motor if sup- 
plied with a current, leads to a fact of great 
importance in the efficiency of electric motors, 
viz. : that during rotation there is induced in the 
armature during its passage through the field of 
the machine, an electromotive force opposed co 
that produced in the armature by the driving 
current, or a counter electromotive force. (See 
Resistance, Spurious. Force, Counter Electro- 
motive.) This counter electromotive force acts 
as a spurious resistance, and opposes the passage 
of the driving current, so that, as the speed of the 
electric motor increases, the strength of the driv- 
ing current becomes less, until, when a certain 
maximum speed is reached, very little current 
passes. In actual practice, this maximum speed 
is not attained, or is only momentarily attained, 
and a small, nearly constant, current is expended 
in overcoming friction at the bearings, air fric- 
tion, etc. 

When, however, the load is placed on the 
motor, that is, when it is caused to do work, the 
speed is reduced and the counter electromotive 
force is decreased, thus permitting a greater cur- 
rent to pass. The fact that the load thus auto- 
matically regulates the current required to drive 
the motor, renders electric motors very economi- 
cal in operation. 

The relations between the power required to 
drive the generating dynamo, and that produced 
by the electric motor, are such that the maximum 
work per second is done by the motor when it 
runs at such a rate that the counter electro- 
motive force it produces is half that of the current 
supplied to it. The maximum work or activity of 
an electric motor is therefore done when its theo- 
retical efficiency is only 50 per cent. This, 
however, must be carefully distinguished from 
the maximum efficiency of an electric motor. A 
maximum efficiency of 100 per cent, can be at- 
tained theoretically ; and, in actual practice, con- 
siderably over 90 per cent, is obtained. In such 
cases, however, the motor is doing work at less 
than its maximum pozver. 

This is Jacobi's law of maximum effect, but 
does not apply to actual motors on account of the 
limitations of current carrying capacity. F> r 
example, a motor of 9 horse power and 90 per 
cent, efficiency loses 1 horse-power in heat within 



Mot.] 



373 



[Hot. 



itself. Hence, if run according to Jacobi's law, 
it would only produce the same amount, i. e., I 
horse-power in useful work instead of 9. More 
than this would overheat it. 

An efficiency of 100 per cent, is reached when 
the counter electromotive force of the motor is 
equal to that of the source supplying the driving 
current. Supposing now the driving machine to 
be of the same type as the motor, and the two 
machines are running at the same speed. If 
now a load is put on the motor so as to reduce its 
speed, and thus permit it to produce a counter 
electromotive force of but 90 per cent., its 
efficiency will Le but 90 p^r cent. In such a 
case, therefore, the efficiency is represented by 
the relative speeds of the generator and the 
motor. 

Motor, Electric, Alternating-Current 

An electric motor driven or operated 

by means of alternating currents. (See 
Motor, Electric?) 

Dr. Louis Duncan divides alternating motors 
into two classes, viz. : 

(1.) Those in which there is but one trans- 
formation in the machine, viz., that of the electric 
energy of the armature current into the mechani- 
cal energy of the armature's rotation. 

(2.) Those in which there are two transforma- 
tions, viz.: 

(a.) The transformation of electrical energy 
from the main current to electrical energy in the 
armature current. 

(b.) The transformation of the electric energy 
of the armature current into mechanical energy. 

Alternating motors of the first type are found 
in the ordinary alternating-current dynamo re- 
versed. Those of the second type in Tesla's or 
Thomson's motors. 

Motor, Electric, Direct-Current 

An electric motor driven or operated by 
means of direct or continuous electric cur- 
rents, as distinguished from a motor driven 
or operated by alternating currents. (See 
Motor, Electric) 

Motor, Electric, High-Speed The 

ordinary electric motor. 

The term high-speed electric motor is used in 
contradistinction to low-speed electric motor. 
(See Motor, Electric, Low-Speed.) 

Motor, Electric, Low-Speed A 



slow-speed motor. (See Motor, Electric, 
Slow-Speed) 

Motor, Electric, Overload of —A 

load greater than that which an electric motor 
can carry while at its greatest efficiency of 
operation, or a load which causes injurious 
heating of a motor. 

Motor, Electric, Reversing Gear of 

— Apparatus for so reversing the direction of 
the current through an electric motor as to re- 
verse the direction of its rotation. (See Rail- 
road, Electric?) 

Motor, Electric, Slow-Speed An 

electric motor so constructed as to run with 
fair efficiency at slow speed. 

The electric motor develops a counter electro- 
motive force when in motion, which, of course,, 
increases with the increase of motion. The elec- 
tric motor has, as generally constructed, its great- 
est efficiency at high speed. When used on street 
railroads, the high speed requires to be decreased 
by various forms of reduction gear. The loss of 
power which all such gear involve, together with 
the noise attending their use, render any decrease 
in speed that can be obtained on the part of the 
motor, without serious loss of efficiency, desir- 
able. 

Motor-Electromotive Force. — (See Eorce y 
Motor Electromotive?) 

Motor, Pyromagnetic A motor 

driven by the attraction of magnet poles on 
a movable core of iron or nickel unequally 
heated. 

The intensity of magnetization of iron decreases 
with an increase of temperature, iron losing most 
of its magnetization at a red heat. A disc of iron 
placed between the poles of a magnet, so as to 
be capable of rotation, will rotate, if heated at a 
part nearer one pole than the other, since it be- 
comes less powerfully magnetized at the heated 
part. 

In the form of pyromagnetic motor devised by 
Edison, and shown in Fig. 400, in elevation, and 
in Fig. 401, in vertical section, the disc of iron is 
replaced by a series of small iron tubes, or di- 
vided annular spaces, heated by the products of 
combustion from a fire placed beneath them. In 
order to render this heating local, a flat screen is 
placed dissymmetrically across the top to prevent 



Mot.] 



374 



[Mot. 



the passage of air through the portion of the iron 
tubes so screened. The air is supplied to the 
furnace by passing down from above through the 




Fig. 4OO. Pyromagnetic Motor. 

tubes so screened. This is shown in the draw- 
ings, the direction of the heating and the cooling 
air currents being indicated by the arrows. The 




Fig. 40 1. Pyromagnetic Motor. 

supply of air from above thus insures the more 
rapid cooling of the screened portion of the 
tubes. 

Motor, Rotating*-Current An 

electric motor designed for use with a rotat- 
ing electric current. 



Unlike alternating current motors, rotary-cur- 
rent motors will, like continuous-current motors, 
readily start with a load. (See Current, Rotating. ) 

Motor, Series-Wound An electric 

motor in which the field and armature are 
connected in series with the external circuit as 
in a series dynamo. (See Machine, Dynamo- 
Electric, Series- Wound) 

Motor, Shunt-Wound An electric 

motor in which the field magnet coils are 
placed in a shunt to the armature circuit. 
(See Machine, Dynamo-Electric, Shunt- 
Wound) 

Motor Standards. — (See Standards, 
Motor.) 

Moulded Mica.— (See Mica, Moulded) 

Moulding-, Electric Wood Mould- 
ing of dried, non-conducting wood, provided 
with longitudinal grooves for the reception 
and support of electric wires or conductors. 

Wood mouldings are employed for the protec- 
tion and concealment of electric conductors. 

Moulding* Wiring*. — (See Wiring, 
Moulding.) 
Mouse-Mill 

Mouse-Mill) 
Mouse-Mill 

Mouse-Mill) 

Mouth Pieces. — (See Pieces, Mouth) 

Movable Secondary. — (See Secondary, 
Movable) 

Mover, Prime In a system of dis- 
tribution of power the motor by which sec- 
ondary motors or movers are driven. 

In a steam plant, the steam engine is the prime 
mover; the shafts or machines driven by the main 
shaft are sometimes called the secondary m -vers. 
The main shaft is called the driving shafi. Its 
motion is carried by means of belts to other 
shafts, called driven shafts. The pulleys on the 
driving or driven shafts are called respectively 
the driving and driven pulleys. 

Movers, Secondary The shafts or 

machines driven by the main shafts in order 
to distinguish them from the steam engine or 
other mover which drives it, (See Mover, 
Prime) 



Dynamo. — (See Dynamo, 
Machine. — (See Machine, 



Mul.] 



375 



[MuL 



Multi-Cellular Electrostatic Voltmeter. 

— (See Voltmeter, Multi-Cellular Electro- 
static^) 

Multiphase Current— (See Current, Mul- 
tiphase) 

Multiphase Dynamo. — (See Dynamo, 
Multiphase?) 

Multiphase System.— (See System, Multi- 
phase?) 

Multiple-Arc Circuit. — (See Circuit, 
Multiple- Arc?) 

Multiple- Arc-Connected Electro-Recep- 
tive Devices. — (See Devices, Electro-Recep- 
tive, Multiple-Arc-Connected) 

Multiple-Arc-Connected Sources. — (See 
Sources, Multiple- A re- Connected.) 

Multiple-Arc-Connected Translating- De- 
vices. — (See Devices, Translating, Mul- 
tiple-Arc-Connected.) 

Multiple-Brush Rocker. — (See Rocker, 
Multiple-Brush.) 

Multiple-Brush Yoke.— (See Yoke, Mul- 
tiple-Pair Brush.) 

Multiple Cable Core.— (See Cable, Mul- 
tiple-Core) 

Multiple Circuit.— (See Circuit, Mul- 
tiple) 

Multiple Conduit.— (See Conduit, Mul- 
tiple) 

Multiple-Connected Battery.— (See Bat- 
tery, Multiple-Connected) 

Multiple-Connected Electro-Receptive 
Devices. — (See Devices, Electro-Receptive, 
Multiple- Connected) 

Multiple-Connected Electro-Receptive 

Devices, Automatic Cut-Out for (See 

Cut-Out, Automatic, for Multiple-Connected 
Electro-Receptive Devices) 

Multiple-Connected Translating* Devices. 
— (See Devices, Translating, Multiple-Con- 
7iected) 

Multiple Connection. -(See Connection, 
Multiple) 



Multiple Distribution of Electricity hy 
Constant Potential Circuits. — (See Elec- 
tricity, Multiple Distribution of, by Constant 
Potential Circuits) 

Multiple Electric-Gaslighting. — (See 
Gaslighting, Multiple Electric) 

Multiple-Series.— A multiple connection 
of series groups. (See Connectio?i, Series 
Multiple) 

Usage in regard to this term is divided. By 
some the term multiple-series is applied to a series 
connection of parallel groups. This is done on 
account of the order of the words, multiple-series 
indicating, it is claimed, a series connection of 
multiple groups. 

Multiple-Series Circuit. — (See Circuity 
Multiple- Series) 

Multiple-Series-Connected Electro-Re- 
ceptive Devices. — (See Devices, Electro- 
Receptive, Multiple-Series-Connected) 

Multiple - Series Connected Sources. — 

(See Sources, Multiple- Series-Connected) 

Multiple-Series-Connected Translating" 
Devices. — (See Devices, Translating, Mul- 
tiple- Series- Connected) 

Multiple-Series Connection.— (See Con- 
nection, Multiple- Series.) 

Multiple-Switch Board. — (See Board, 
Multiple- Switch ) 

Multiple Transformer. — (See Trans- 
former, Multiple) 

Multiple Transmission. — (See Trans- 
mission, Multiple) 

Multiple Working of Dynamo-Electric 
Machines. — (See Working, Multiple, of 
Dynamo-Electric' Machines) 

Multiplex Telegraphy. — (See Teleg- 
raphy, Multiplex) 

Multiplicator. — A word sometimes used 
for multiplier. 

Multiplier, Galvanic A term for- 
merly aoplied to a galvanometer. (See Gal- 
vanometer) 

Multiplier, Schweigger's The 

name first given to a coil consisting of a 



Mul. 



376 



[Nee. 



number of turns of insulated wire, provided 
for the purpose of increasing the strength of 
the magnetic field produced by an electric 
current, and consequently the amount of its 
deflecting power on a magnetic needle. 

Schweigger's multiplier was in fact an early 
form of galvanometer. (See Galvanometer.) 

Multiplying" Power of Shunt. — (See 
Shunt, Multiplying Power of) 

Multipolar Armature. — (See Armature, 
Multipolar.) 

Multipolar Dynamo-Electric Machine. — 
(See Machi?ie, Dynamo-Electric, Multipo- 
lar^) 

Multipolar-Electric Bath. — (See Bath, 
Multipolar Electric?) 

Muscle Current— (See Current, Muscle) 

Muscles, Electrical Excitation of 

(See Excitation, Electro-Muscular) 



Muscular, Electro 



-Pertaining to 



the influence of electricity on the muscles. 

Muscular or Nerve Fibre, Excitability 

of (See Excitability, Electric, of 

Nerve or Muscular Fibre) 

Muscular Pile, Matteucci's (See 

Pile, Muscular, Matteucci's) 

Musket, Electric A gun in which 

the charge is ignited by a platinum wire ren- 
dered incandescent by the action of a bat- 
tery placed in the stock of the gun. 

Mutual Inductance. — (See Inductance) 

Mutual Induction. — (See Induction, 
Mutual) 

Mutual Induction, Co-efficient of 

— (See Induction, Mutual, Co-efficient of.) 

Myria (as a prefix). — A million times. 



N 



N. — A contraction employed in mathe- 
matical writings for the whole number of 
lines of magnetic force in any magnetic cir- 
cuit. 

N. — A contraction for North Pole. 

This N, may be distinguished from the N, used 
for expressing the whole number of lines of mag- 
netic force, by making the former light and the 
latter heavy. 

N. H. P. — A contraction for Nominal 
Horse-Power. 

Nominal horse-power is a somewhat indefi- 
nite term for a quantity dependent on the length 
of stroke and the dimensions of the cylin- 
der. This quantity is a dependent one, be- 
cause it varies necessarily with the type of en- 
gine. 

Nascent State. — (See State, Nascent) 

Natural Currents. — (See Currents, Nat- 
ural) 
Natural Law. — (See Law, Natural) 

Natural Magnet. — (See Magnet, Nat- 
tiral) 



Natural Unit of Electricity. — (See Elec- 
tricity, Natural Unit of) 
Natural Unit of Quantity of Electricity, 

— (See Electricity, Unit Quatitity of, Natu- 
ral) 

Nautical Mile.— (See Mile, Nautical) 

Needle Annunciator. — (See Annunciator, 
Needle) 

Needle, Astatic A compound mag- 
netic needle of great sensibility, possessing 
little or no directive power. 

An astatic needle consisting of two separate 
magnetic needles, rigidly connected together 
and placed parallel and directly over each 
other, with opposite poles opposed. 

An astatic needle is shown in Fig. 402. The 
two magnets N S, and S' N', are directly opposed 
in their polarities, and are rigidly connected to- 
gether by means of the axis a, a. So disposed, 
the two magnets act as a very weak single needle 
when placed in a magnetic field. 

Were the two magnets N S, and S' N', of ex- 
actly equal strength, with their poles placed in 
exactly the same vertical plane, they would com- 
pletely neutralize each other, and the needle 



Nee.] 



377 



[Xee. 



•would have no directive tendency. Such a sys- 
tem would form an Asiatic Pair or Couple. 

In practice it is impossible to do this, so that the 




'Si; 



m*< 



Fig. 402. Astat.c Needle. 

needle has a directive tendency, which is often 
east and west. 

The cause of the east and west directive ten- 
dency of an unequally bal- 
anced astatic system will 
be understood from an in- 
spection of Fig. 403. Un- 
less the two needles, N S, 
and S' N', are exactly op- 
posed, they will form a Fig- 403- Astatic Pair. 
single short magnet, N N NN, S S S S, the poles 
of which are on the sides of the needle. The 
system pointing with its sides due north and 
south will appear to have an east and west direc- 
tion. 

The principal use of the astatic needle is in the 
astatic galvanometer, in which the needle is de- 
flected by the passage of an electric current 
through a conductor placed near the needle. 
Therefore it is evident that one of the needles 
must be outside and the other inside the coil. In 
the most sensitive /"" S5? ^ 

form of galvanome- ^/ \ 

ter there is also a 
coil surrounding the 
upper needle, the 
two coils being op- 
positely connected, 
so that the deflection 
on both needles is in 
the same direction, 
and the deflecting Fi S- 404- Astatic System. 
power is equal to the sum of the two coils, while 
the directive power of the needles is the differ- 
ence of their magnetic intensities. 

In the astatic system, as shown in Fig. 404, the 
current, which flows above one needle, flows be- 
low the other, and therefore deflects both needles 




in the same direction, since their poles point in 
opposite directions. 

In some galvanometers a varying degree of 
sensitiveness is obtained by means of a magnet, 
called a compensating magnet, placed on an axis 
above the magnetic needle. As the compensat- 
ing magnet is moved towards or away from the 
needle the effect of the earth's field is varied, and 
with it the sensitiveness of the galvanometer. 
Such a magnet may form with the needle an 
astatic system. (See Magnet, Compensating. 
Galvanometer, Astatic. Galvanometer, Mirror. 
Multiplier, Sc/izaeigger y s). 

Needle Electrode. — (See Electrode, Nee- 
dle^ 

Needle, Elongation of A phrase 

sometimes used for the angular deflection of 
a needle. 

Needle, Magnetic A straight bar- 
shaped needle of magnetized steel, poised 
near or above its centre of gravity, and free 
to move either in a horizontal plane only, or 
in a vertical plane only, or in both. 

A magnetic needle free to move in a vertical 
plane only is called a dipping needle. A mag- 
netic needle free to move in a horizontal plane 
only, as shown in Fig. 405, is the form employed 

s N 




Fig. 40 j. Magnetic Needle. 

in the mariner's compass. This form of magnetic 
needle is the one most commonly employed. 

For use as a mariner's compass the needle is 
supported on gimbals and placed in a box pro- 
vided with a card on which are marked the 
points of the compass. (See Compass, Azimuth. 
Compass, Points of.) 

Needle, Magnetic, Annual Variations of 

Variations in the value of the mag- 



Nee.] 



378 



LNee. 



netic declination that take piace at regular 
periods of the year. 

The annual variations of the magnetic field were 
discovered by Cassini in 1786. 

Needle, Magnetic, Daily Yariation of 

Variations in the value of the magnetic 

declination that take place at different periods 
of the day. 

It was noticed, for example, in London that the 
north pole of the magnetic needle begins to move 
westward between 7 and 8 A. M. and continues 
this movement until I P. M., when it begins to 
move towards the east until near 10 p. M., when 
it again begins its westward course. 

Needle, Magnetic, Damped — A 

magnetic needle so placed as to quickly come 
to rest after it has been set in motion. (See 
Damping?) 

Magnetic damping is readily effected by caus- 
ing the needle to move near a metallic plate. On 
the motion of the needle the currents set up in the 
plate by dynamo-electric induction tend, accord- 
ing to Lenz's law, to oppose the motions pro- 
ducing them. (See Induction, Electro-Dyna?nic. 
Laws, Lenz's.') 

Needle, Magnetic, Declination of 

The angular deviation of the magnetic needle 
from the true geographical north. 

The variation of the magnetic needle. 

The declination of the magnetic needle is either 
E. or W. (See Declination, Angle of .) 

Declination, or variation, is different at dif- 
ferent parts of the earth's surface. 

Lines connecting places which have the same 
value and direction for the declination are called 
isogonal lines. A chart on which the isogonal 
lines are marked is called a variation chart. 

The value of the declination varies at dif- 
ferent times. These variations of the declination 
are: 

(1.) Secular, or those occurring during great 
intervals of time. Thus, in London, in 1580 the 
magnetic needle had a variation of about II 
degrees east. This eastern declination decreased 
in 1622 to 6 degrees E., and in 1680 the needle 
pointed to the true north. In 1692 the declina- 
tion was 6 degrees W. ; in 1730, 13 degrees W.; 
in 1765, 20 degrees W. ; and in 1818 the needle 
reached its greatest western declination and is 



now moving eastwards. The declination, how- 
ever, is still west. 

(2.) Annual, the needle varying slightly in its 
declination during different seasons of the year. 

(3. ) Diurnal, the needle varying slightly in its 
declination during different hours of the day. 

(4.) Irregular, or those which occur during 
the prevalence of a magnetic storm. 

It has been discovered that the occurrence of a 
magnetic storm is simultaneous with the occur- 
rence of an unusual number of sun spots. (See 
Spots, Sun.) 

Needle, Magnetic, Deflection of 

The movement of a needle out of a position of 
rest in the earth's magnetic field or in the 
field of another magnet, by the action of an 
electric current or another magnet. 

The deflection of the needle is sometimes called 
its elongation. This latter term is, however, but 
little used, and is unnecessary. 

Needle, Magnetic, Dipping — A 

magnetic needle suspended so as to be tree 
to move in a vertical plane, employed to de- 
termine the angle of dip or the magnetic in- 
clination. (See Dip, Magnetic. Inclination, 
Magnetic. Inclinojneter. Chart, Inclina- 
tion?) 

A dipping needle is shown in Fig. 406. The 




Fig. 406. Dipping Needle. 

angle B O C, which marks the deviation of the 
needle from the horizontal position, is called the 
angle ot dip. 



Nee.] 



379 



[Neg. 



Needle, Magnetic, Directive Tendency of 

-The tendency of a magnetic needle to 



move so as to come to rest in the direction of 
the lines of the earth's magnetic field. 

The directive power of the magnetic needle is 
due to the attraction of the earth's magnetic poles 
for the poles of the needle, or to the action of the 
earth's magnetic field. Since the force of the 
earth's magnetism forms a couple, there is no 
tendency for the needle to move bodily forward 
towards either of the earth's poles. Its tendency 
is merely to rotate until it comes to rest within 
the lines of the earth's magnetic field, entering at 
its south pole, passing through its mass and 
coming out at its north pole. 

Of course this would be true in the case of a 
directing magnet only when it is at a great dis- 
tance from the needle. Otherwise, there would 
be motion towards the poles as well as rotation. 

Needle, Magnetic, Inclination or Dip of 

The deviation of a mechanically bal- 
anced magnetic needle from a horizontal po- 
sition. 

The direction of a magnetic needle in all parts 
of the earth, except at the magnetic equator, 
differs from a level or horizontal position. One 
of its ends inclines or dips towards the ground. 
(See Dip, Magnetic. Needle, Magnetic, Dipping.) 

Needle, Magnetic, Orientation of 

The coming to rest of a magnetic needle in 
the earth's magnetic field. 

Needle, Magnetic, Variation of 

The angular deviation of a magnetic needle 
from the true geographic north. 

The declination of the magnetic needle. 
(See Declination?) 

Needle of Oscillation. — A small magnetic 
needle employed for measuring the intensity 
of a magnetic field by counting the number of 
oscillations the needle makes in a given time, 
when disturbed from its position of rest in 
such field. (See Magnetization, Intensity of. 
Lines, Isodynamic.) 

This use of a magnetic needle in determining 
the magnetic intensity of any place is analogous 
to the use of the pendulum in determining the in- 
tensity of gravity at any place. 

Suppose, for example, that at a certain place the 
needle made 245 oscillations in ten minutes, and 



that at another place it made 211 in the same 
time. Then the relative intensities at these two 
places would be as the square of these two num- 
bers, or as 1 : 1.3482. 

Needle, Telegraphic A needle em- 
ployed in telegraphy to represent by its move- 
ments to the left or right respectively the dots 
and dashes of the Morse alphabet. (See 
Telegraphy, Needle System of.) 

Needle, Throw of A phrase some- 
times used for the angular deflection of a 
needle, particularly when the needle is swing- 
ing. 

The displacement of the magnetic needle is 
called the deflection, the elongation, or the throw. 
The first will appear to be the preferable term 
when the needle comes to rest in a displaced posi- 
tion. 

Negative Charge. — (See Charge, Nega- 
tive?) 

Negative Direction of Electrical Con- 
vection of Heat. — (See Direction, Negative, 
of Electrical Convection of Heat?) 

Negative Direction of Simple-Harmonic 
Motion. — (See Motion, Simple-Harmonic, 
Negative Direction of.) 

Negative Electricity. — (See Electricity, 
Negative.) 

Negative Electrode.— (See Electrode, . 
Negative?) 

Negative Element of a Voltaic Cell.— 
(See Element, Negative, of a Voltaic Cell?) 

Negative Feeders.— (See Feeders, Nega- 
tive?) 

Negative Omnibus Bars. — (See Bars, 
Negative Omnibus?) 

Negative Phase of Electro tonus.— (See 
Electrotonus, Negative Phase of.) 

Negative Plate of Storage Battery. — 
(See Plate, Negative, of Storage Cell.) 

Negative Plate of Voltaic Cell.— (See 
Plate, Negative, of Voltaic Cell.) 

Negative Pole. — (See Pole, Negative?) 

Negative Potential. — (See Potential, Neg- 
ative?) 

Negative Side of Circuit. — (See Circuit* 
Negative Side of.) 



Neg.] 



380 



[Nig. 



Negative Wire.— (See Wire, Negative?) 

Negatively. — In a negative manner. 

Negatively Excited. — Charged with nega- 
tive electricity. (See Electricity, Negative?) 

Nerve or Muscular Fibre, Excitability 

of — (See Excitability, Electric, of 

Nerve or Muscular Fibre?) 

Nerves, Actio u of Electricity on 



Stimulating and other actions produced in 
nerves by the passage of electricity through 
them, dependent on the direction and char- 
acter of the current. (See Electroto?ius. 
Galvafiization. Faradization. Galvano- 
Faradizatio?i.) 

Net, Faraday's An insulated net 

of cotton gauze, or other similar material, 
capable of being turned inside out without 
being thereby discharged, employed for de- 
monstrating that in a charged, insulated con- 
ductor the entire charge is accumulated on 
the outer surface of the conductor. 




Fig. 407. Faraday's Net. 

Faraday's net, as shown in Fig. 407, consists 
of a bag N, of cotton gauze, or mosquito netting, 
supported on an insulating stand I. When tested 
by a proof plane, no free electric charge is found 
on the inside, though such a charge is readily 
detected by the same means on the outside. By 
the aid of the silk strings S, S, the bag can be 
turned inside out, when the charge will then all 
be found on the then inside, or the now outside. 
Faraday was in the habit of protecting his 
delicate electroscopes against outside electrifica- 
„tion by covering them with gauze. To properly 
act as an electric screen, the gauze should be con- 
nected with the earth. 

Faraday constructed a small insulated room, 



twelve feet in height, breadth and depth, covered 
on the inside with tin-foil, and, on charging this 
room from the outside, he was unable to detect 
the presence of any charge on the inside, even by 
the aid of his most delicate instruments. This 
room is often referred to as Faraday's Cube. 

Nets, Torpedo Steel wire netting 

suspended from or attached to a ship's side 
for the purpose of ensuring protection against 
moving torpedoes. 

Network of Currents. — (See Currents, 
Network of. Laws, Kirchhoff's?). 

Neutral Armature. — (See Armature, 
Neutral?) 

Neutral Feeder. — The feeder that is 
connected with the neutral or intermediate 
terminal of the dynamos in a three-wire sys- 
tem of distribution. (See Feeders?) 

Neutral Line of Commutator Cylinder. 

— (See Line, Neutral, of Conunutator 
Cylinder.) 

Neutral ■ Omnibus Bars. — (See Bars, 
Neutral-Omnibus.) 

Neutral Point. — (See Point, Neutral.) 

Neutral Points of a Dynamo- Electric 
Machine.— (See Points, Neutral, of Dy?ia7no- 
Electric Machine?) 

Neutral Points of Magnet.— (See Points, 
Neutral, of Magnet?) 

Neutral Points of Thermo-Electric Dia- 
gram. — (See Points, Neutral, of Thermo- 
Electric Diagram?) 

Neutral-Relay Armature.— (See Arma- 
ture, Neutral- Relay?) 

Neutral Section of Magnet. — (See Sec- 
tion, Neutral, of Magnet?) 

Neutral Wire. — (See Wire, Neutral?) 
Neutral Wire Ampere-Meter. — (See Am- 
pere-Meter, Balance or Neutral Wire?) 
New Ohm. — (See Ohm, New.) 
Nickel Bath.— (See Bath, Nickel?) 

Nickeling, Electro Electroplating 

with nickel. (See Plating, Electro?) 

Nickel-Plating.— (See Plating, Nickel?) 
Night Bell.- (See Bell, Night?) 



]*od.] 



381 



[Noi. 



Nodal Point.— (See Point, Nodal) 

Nodes, Electrical Points in an open 

circuited conductor, through which electrical 
oscillations are passing, which possess a con- 
stant mean value of potential, while the poten- 
tial at its ends alternates between two fixed 
limits. 

Points on a conductor where the strength 
of the induced oscillatory current is equal to 
zero. 

The nodal points on a conductor through which 
electrical oscillations are passing therefore cor- 
respond closely to the nodes on a vibrating wire 
or cord. 

Dr. Hertz employed the following appara- 
tus in order to show the position of two nodes 
in a conductor: An induction coil, A, had its sec- 
ondary terminals connected as shown in Fig. 408, 



-©■ 




-©- 



Fig. 408 
to two metallic spheres, C and C 



Nodes in Conductor. 

The spark mi- 



crometer circuit, a c d b, was placed near it, as 
shown, and the sparking distance of the secondary 
circuit of the induction eoil adjusted, so that the 
spark micrometer circuit was in unison with it. 
When sparks were passed between the terminals 
of the induction coil A, sparks passed between the 
terminals 1 and 2, at M, under the influence of 
resonant action. 

If, now, a second micrometer circuit, e g h f, 
exactly similar to a c d b, was added, as shown in 
the figure, and the two joined near the terminals 1 
2 3 4, by conducting wires, as shown, the entire 
system of the micrometer circuit formed a closed 
metallic circuit, the fundamental vibration of 
which would have two nodes, one at the middle 
point of c d, and the other at g h. The inter- 
nodes would be at the junctions 1 3, and 2 4, and 
under these circumstances a true resonant ac- 
tion existed between the secondary circuit and the 
micrometer circuit, as was shown by the fact that 
ajiy alteration in the circuit e g h f , whether by 



increasing or decreasing its length, diminished 
the sparking distance. Since the conductor con- 
necting points 2, and 4, was in the position of 
the node, where the strength of the excited oscil- 
latory current was zero, its removal from between 
these points should have no influence on the 
intensity of the vibration. This was found on 
trial to be the case. Electrical vibrations may 
therefore be excited by electrical resonance in 
conductors corresponding not only to the simple 
fundamental note or vibration, but also to the 
higher electrical overtones. 

The apparatus shown in Fig. 409, from Tesla, 
illustrates the phenomena of alternative path, as 
well as electric nodes. The terminals of an in- 
duction coil are connected, as shown, to a con- 
denser and to a thick copper conductor. Though 
the two incandescent lamps are placed as shown, 
yet they are raised to luminosity by a species of 
brush discharge that passes through them, al- 
though they would be short circuited to any cur- 
rent but an oscillatory discharge. 




Fig. 40 Q. Nodes in a Conductor. 

Nodular Deposit, Electro-Metallurg-ical 

(See Deposit, Electro-Metallurgical 

Nodular) 
Noisy Arc— (See Arc, Noisy) 



Nom.J 



382 



[Num. 



Nominal Candle-Power. — (See Power, 
Candle, Nominal.) 
Non-Automatic Variable Resistance. — 

(See Resistance, Variable, Non-Automatic.) 

Non-Conductors. — Substances that offer 
so great resistance to the passage of an elec- 
tric current through their mass as to practi- 
cally exclude a discharge passing through 
them. 

Non conductors are called insulators, because 
they electrically insulate substances placed on or 
surrounded by them. 

The terms non-conductors or insulators are 
ordinarily used in a relative sense to mean bodies 
which allow no practical or appreciable current 
to pass through them, since there are no sub- 
stances known, apart, perhaps, from the universal 
ether, that absolutely prevent the flow of an elec- 
tric current, the difference of potential of which 
is sufficiently great. 

The entire absence of ordinary matter, as in the 
case of a high vacuum, appears to render a high 
vacuum very nearly, if not entirely, an absolute 
insulator. 

Non-Electrics. — A term formerly applied 
to substances like metals or other conductors 
which appeared not to become electiified by 
friction. 

The term non-electric, was used in contradis- 
tinction to electrics, or substances readily elec- 
trified by friction. The distinction no longer 
holds, since non -electrics, if insulated, are readily 
electrified by friction. 

Non-Homogeneous Current-Distribu- 
tion. — (See Current, Non-Homogeneous, 
Distribution of.) 

Non-Illumined Electrode. — (See Elec- 
trode, Non-Illutnined^) 

Non-inductive Resistance. — (See Resist- 
ance, Non-inductive.) 

Non-Oscillatory Discharge.— (See Dis- 
charge, Non-Oscillatory.) 

Non-Polarized Armature.— (See Arma- 
ture, Non-Polarized^ 

Non-Polarizable Electrodes. — (See Elec- 
trodes, Non-Polarizable.) 

Non-Wasting Electrode. — (See Electrode, 
Non- Wasting.) 



Normal Day, Magnetic (See Day, 

Normal Magnetic.) 

Northern Light. — The Aurora Borealis. 
(See Aurora Borealis.) 

Notation, Algebraic A system of 

arbitrary symbols employed in algebra. 

The following brief description of the notation 
employed in algebra is for the use of the non- 
mathematical reader. 

Quantities are represented in algebra by let- 
ters, such as a, and b, x, and y, etc. 

Addition is represented thus: a + b. 

Subtraction is represented thus: a — b. 

Multiplication is represented thus: a X b, or 
simply by writing the letters next to each other ab. 

Division is represented thus: a -=- b, or — 

An Exponent, or figure placed to the right of a 
letter, above it as a 3 , indicates that the quantity 
represented by a, is to be multiplied by itself three 
times, as a X a X a, or a a a. 

A Co-efficient, or figure placed to the left of a 
quantity, indicates the number of times that quan- 
tity is to be taken; thus, 3 a, indicates that a is to 
be added three times, thus: a-j-a-j-a, or 3 X a. 

A Radical Sign or Root, thus \/ a, or 2 v/a, 
indicates that the square root of the quantity a. t 
is to be taken. In the same manner 3 V a, indi- 
cates that the cube root of a is to be taken. 

These expressions are sometimes written aJ, or 



Equality is indicated thus: a 3 =a XaXa, or 

A negative exponent a -2 indicates _, or is the 

a 2 
exponent of the reciprocal of the quantity indi- 
cated. 

Null or Zero Method.— (See Method^ 
Null or Zero.) 

Null Point.— (See Point, Null.) 



Number, Diacritical 



-Such a num- 



ber of ampere-turns at which a given core 
would receive a magnetization equal to half 
saturation. 



Obs.] 



383 



[Ohm. 



£1. — A contraction for megohm. (See 
Okm, Meg.) 

oo. — A contraction for ohm. (See Ohm.) 

Obscure Heat.— (See Heat, Obscure). 

Observation Mine.— (See Mine, Observa- 
tion) 

Observatory, Magnetic An obser- 
vatory in which observations of the variations 
in the direction and intensity of the earth's 
magnetic field are made. 

Magnetic observatories are generally furnished 
with self-registering magnetic apparatus, such as 
magnet ographs, viagnetometers, inclinometers. 
(See Magnet o?neter. Magnet ograph. Inclinome- 
ter.) 

Magnetic observatories are generally con- 
structed entirely of non-magnetic materials; that 
is, of such materials as are destitute of paramag- 
netic properties. 

Obtuse Angle— (See Angle, Obtuse) 

Occlusion of Gas.— (See Gas, Occlusion 

' of) 

Odorscope. — An apparatus in which the 
determination of an odor was attempted by 
the measurement of the effect the odorous 
vapor, or effluvia, produced on a variable 
contact resistance. 

The microtasimeter was used in connection 
with the odorscope. (See Diagomeler, Rous- 
seaii's. Microtasimeter.) 

Oerstedt, An A proposed term for 

the unit of electric current, in place of an 
ampere. 

The term has not been adopted. 

Ohm. — The unit of electric resistance. 

Such a resistance as would limit the flow 
of electricity under an electromotive force of 
one volt to a current of one ampere, or to one 
coulomb per second. (See Unit, B. A. Ohm, 
JLegal. Ohm, Standard) 

A value equal to io 9 absolute electro-mag- 
netic units. 

A value which is represented by a velocity 
of i o°, or i ,000,000,000 centimetres per second. 



It may be difficult at first to see how resistance 
can be correctly represented by a velocity. The 
following consideration may render this clear : 
The formula for calculating the velocity is 

D 

V = vjr, or the velocity equals the distance passed 

through in unit time. Now, by examining the 
formula for the value of the resistance, expressed 
in terms of the electro-magnetic units (see 
Units, Electro-Magnetic, Dimensions of), it may 
be seen to be that resistance = 

Electromotive force L 

Cunent. T 

But this value is of the nature of a velocity, 
being equal to the length, divided by the time. 
Resistance, therefore, has the dimensions of a 
velocity. 

This is clearly expressed by Silvanus P. Thomp- 
son in his ' ' Elementary Lessons in Electricity 
and Magnetism," as follows, viz.: " Suppose we 
have a circuit composed of two horizontal coils, 
C S, and D T (Fig. 410), I centimetre apart, 
joined at C D, and completed by means of a 
sliding piece, A B. Let this variable circuit be 
placed in a uniform magnetic field of unit inten- 
sity, the lines of force being directed vertically 
downwards through the circuit. 

"If, now, the slider be moved along towards 
S T, with a velocity of n, centimetres per second, 
the number of additional lines of force embraced 
by the circuit will increase at the rate of n, per 
second ; or, in other words, there will be an in- 



z 




J 



wvy 



D ^A. T 

Fig. 410. Resistance as a Velocity. 

duced electromotive force impressed upon the cir- 
cuit, which will cause a current to flow through 
the slider from A to B. Let the rails have no 
resistance, then the strength of the current will 
depend on the resistance of A B. Now, let A B, 
move at such a rate that the current shall be of 
unit strength. If its resistance be one absolute 
(electro-magnetic) unit, it need only move at the 
rate of 1 centimetre per second. If its resistance 
be greater, it must move with a proportionately 



Oa in.] 



3S4 



LOknw 



greater velocity ; the velocity at which it must 
move to keep up a current of unit strength being 
numerically equal to its resistance. The resist- 
ance known as " i ohm " is intended to be io 9 ab- 
solute electro-magnetic units, and, therefore, is 
represented by a velocity of io 9 centimetres, or 
10,000,000 metres (/ earth-quadrant) per 
second. ' ' 

Ohm, B. A. A contraction for 

British Association ohm. 

Ohm, Board of Trade — A unit of re- 
sistance as determined by a committee of the 
English Board of Trade. 

A committee consisting of Sir W. Thomson, 
Lord Rayleigh, Dr. J. Hopkinson and other 
authorities appointed by the Board of Trade 
(England) has recently recommended that the 
ohm be taken as the resistance of a column of 
mercury 106.3 centimetres in length and one 
square millimetre area of cross-section at o de- 
grees C. and since this value agrees with the best 
experimental results, it will probably be generally 
and finally adopted. 

Ohm, British Association The 

British Association unit of resistance, 
adopted prior to 1884. 

The value of the unit of electric resistance, or 
the ohm, was determined by a Committee of the 
British Association as being equal to the resistance 
at o degree C. of a column of mercury 1 square 
millimetre in area of cross-section and 104.9 
centimetres in length. This length was taken as 
coming nearest the value of the true ohm de- 
duced experimentally from certain theoretical 
considerations. Subsequent re-determinations 
showed the value so obtained to be erroneous. 

The value of the ohm is now taken internation- 
ally, as adopted by the International Electric 
Congress in 1884, as the resistance of a column 
of mercury 106 centimetres in length, and I 
square millimetre in area of cross-section. This 
last value is called the legal ohm, to distinguish it 
from the B. A. ohm, which, as above stated, is 
equal to a mercury column 104.9 centimetres in 
length. Usage now sanctions the use of the 
word ohm to mean the legal ohm. 

This value of the legal ohm is provisional until 
the exact length of the mercury column can be 
finally determined. (See Ohm, Board of Trade. ) 

The following are the relative values of these 
units, viz.: 



1 legal ohm = 1.0112 B. A. ohm. 

" " = 1.0600 Siemens unit. 

1 B. A. ohm == .9889 legal ohm. 

1 " " = 1 .0483 Siemens unit. 

1 Siemens unit , = .9540 B. A. ohm. 

" " = .9434 legal ohm. 

Ohm, Legal The resistance of a 

column of mercury 1 square millimetre in 
area of cross-section, and 106 centimetres in 
length, at the temperature of o degree C. or 
32 degrees F. (See Unit,B. A.) 

1 ohm = 1. 001 12 B. A. units. This va'ue of 
the ohm was adopted by the International Elec- 
tric Congress, in 1884, as a value that should be 
accepted internationally as the true value of the 
ohm. This value, however, was provisional, and 
was never actually legalized. It will probably be 
replaced by the new (106.3 cm -) onm ' (See 
Ohm, Board of Trade. ) 

Ohm, Meg One million ohms. 

Ohm, New A term sometimes used 

for t'he Board of Trade ohm. (See Ohm,. 
Board of Trade?) 

Ohm, Standard — 



-A length of wire 



having a resistance of the value of the true 
or legal ohm, employed in standardizing re- 
sistance coils. 

The standard ohm, as issued by the Electric 
Standards Committee of England, has the form 




Fig. 411. Standard Ohm. 
shown in Fig. 411. The coil of wire is formed' 
of an alloy of platinum and silver, insulated by 
silk covering and melted paraffine. Its ends are 
soldered to thick copper rods r, r', for ready- 
connection with mercury cups. The coil is at 
B. The space above it at A, is filled with paraffine,, 
except at the opening t, which is provided for 
the insertion of a thermomeier. 



Oam. J 



335 



[Ope. 



Ohm, True An ohm having the 

true theoretical value of the ohm. (See Ohm.) 

Ohmage. — The value of the resistance of 
a circuit expressed in ohms. 

Ohmic Resistance. — (See Resistance, 
Ohmic or True.) 

Ohmmeter. — A commercial galvanometer, 
devised by Ayrton, for directly measuring by 
the deflection of a magnetic needle, the re- 
sistance of any part of a circuit through 
which a strong current of electricity is 
flowing. 

Ayrton's ohmmeter is represented diagram- 
matically in Fig. 412. Two coils C C, and c c, 




/ 
J 4 

Fig. 412. Ayrton's Ohmmeter. 

consisting of a short thick wire, and a long thin 
wire, respectively, are placed at right angles to 
each other, and act on a soft iron needle situated 
as shown. The short, thick wire coil C C, is con- 
nected in series with the resistance O, to be 
measured. The long, fine wire coil, of known 
high resistance, is placed as a shunt to the un- 
known resistance. 

Under these circumstances, it can be shown 
that the action on the needle is that due to the ratio 
of the difference of potential at the terminals of 
the unknown resistance and the current strength 

E 

C' 

deduced from Ohm's law. 

• The coils are so proportioned that the current 
when flowing through the short thick wire moves 
the needle to the zero of the scale, while the long 
thin wire produces a deflection directly propor- 
tional to the resistance. 

Ohm's Law. — (See Law of O/im.) 

Oil, Colza An oil obtained from the 

seed of the Brassica oleracea, a species of 
cabbage. 

Colza oil is extensively used for purposes of il- 
lumination and in the carcel standard lamp. (See 
Lamp, Carcel.) 



in the thick wire coil, or R = _, as may be 



Oil Cup. — A cup containing oil for lubri 
eating machinery. 

Oil Insulator. — (See Lnsulator, Oil.) 

Oil Transformer. — (See Transformer, 
Oil) 

Oiler, Automatic An oil cup or res- 
ervoir that automatically spreads oil over the 
bearings of machinery in motion. 

Okonite. — A variety of insulating material. 

Omnibus Bars. — (See Bars, Omnibus) 

Omnibus Wires. — (See Wires, Omnibus.) 

Opacity, Selective Opaque in a cer- 
tain direction or directions only. 

Certain substances are opaque to polarized light 
in certain planes only. Thus, a plate of tourma- 
line permits light polarized in. a certain plane 
freely to pass through it, but is entirely opaque 
in a plane at right angles thereto. 

S. P. Thompson and Lodge have shown that 
such crystals of tourmaline possess curious prop- 
erties in regard to the conduction of heat. While 
warming, the crystal conducts heat better in a cer- 
tain direction than in the opposite direction. While 
cooling, exactly the opposite effects are observed. 
In the same manner, while the crystal is rising in 
temperature, there is an accumulation of positive 
electricity at one end, an I negative at the other. 
While the crystal is cooling, the reverse is true. 

Open-Box Conduit— (See Conduit, Open- 
Box) 

Open Circuit. — (See Circuit, Open) 
Open-Circuit Electric Oscillations. — 

(See Oscillations, Open-Circuit, Electric) 
Open-Circuit Induction. — (See Induction, 

Open-Circuit.) 
Open-Circuit Oscillation, Period of 

— The time in which the oscillations set up in 
a circuit by electrical resonance require to 
make a complete one to-and-fro motion. 

The period of an open-circuit electric oscillation 
is determined by the product of the co-efficients 
of self-induction of the conductor, and does not 
depend on the composition of the terminals. It is 
practically independent of their resistances. 

Open-Circuit Single-Current Signaling. — 

(See Signaling, Single-Current, Open- 
Circuit.) 



Ope.] 



386 



[Ore, 



Open-Circuit Yoltaic Cell. — (See Cell, 
Voltaic, Opoi-Circuit) 

Open-Circuit Voltmeter. — (See Volt- 
meter, Open-Circuit.} 

Open-Circuited. — Put on an open circuit. 

Open-Circuited Conductor. — (See Con- 
ductor, Open-Circuited.) 

Open-Circuited Thermostat. — (See Ther- 
mostat, Open-Circuit.) 

Open-Coil Drum Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric , 
Open-Coil Drum.) 

Open-Coil Dynamo-Electric Machine. — 

(See Machine, Dynamo-Electric, Open-Ceil.) 

Open-Coil Ring" Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Open-Coil Ring) 

Open-Iron-Circuit Transformer. — (See 
Transformer, Open-Iron-Circuit.) 

Open-Iron Magnetic Circuit. — (See Cir- 
cuit, Open-Iron Magnetic.) 

Open Magnetic Core. — (See Core, Open- 
Magnetic.) 

Opening" Shock. — (See Shock, Opening) 

Operation, Magnet The use of a 

magnet for the purpose of removing particles 
of iron from the human eye. 

Optical Strain. — (See Strain, Optical.) 

Optical Strain, Electro-Magnetic 

(See Strain, Optical Electro-Magnetic.) 

Optical Strain, Electrostatic (See 

Strain, Electrostatic, Optical.) 

Optics, Electro —That branch of 

electricity which treats of the general relations 
that exist between light and electricity. 

The phenomena of electro-optics may be ar- 
ranged under the following heads, viz.: 

(i.) Electrostatic stress, produced by an 
•electrostatic field causing an optical strain in a 
transparent medium, whereby such medium 
acquires the property of either rotating the plane 
of polarization of a beam of plane polarized light, 
£>r of doubly refracting light. 

(2.) Electro magnetic stress produced by a 



magnetic field causing an optical strain in a trans- 
parent medium, whereby such medium acquires 
the property of either rotating the plane of polar- 
ization, or of doubly refracting light. (See He- 
fraction, Double, Electric.) 

(3.) Changes in the electric resistance of bodies 
caused by the action of light. (See Cell, Sele- 
nium. ) 

(4.) The relation existing between the values of 
the index of refraction of a transparent medium 
and its specific inductive capacity. (See Refrac- 
tion. Capacity \ Specific Inductive.) 

This relation has been shown to be as follows : 

The specific inductive capacity is approxi- 
mately equal to the square of the index of re- 
fraction. 

(5.) The relation existing between the velocity 
of light and the value of the ratio of electrostatic 
and the electro-magnetic units, thus giving a 
basis for an electro-magnetic theory of light. 
(See Light, Maxwell's Electro -Magnetic Theory 
of.) 

Polarized light reflected from the surface of a 
magnet, although it penetrates the substance to 
but a trifling extent, yet has its plane of polariza- 
tion distinctly rotated by the magnetic whirls in 
the iron. 

Oral or Speaking-Tube Annunciator.— 

(See Annunciator, Oral or Speaking- Tube.) 
Ordinate. — A distance taken on a per- 
pendicular line called the axis of ordinates, in 
contradistinction to the axis of abscissas. 
(See Ordinates, Axis of) 

Thus in Fig. 413, D 1, is the ordinate of the 
point D, in the curve O D R. 

Ordinates, Axis of One of the axes 

of co-ordinates used 



for determining the 
position of the points 
in a curved line. 

Thus in Fig. 413 the 
line A B, is called the axis 
of ordinates because it is 
the line on which the or- 
dinate 2 D, is measured. 




A 2 C 

Fig. 413. Axis of Ordi- 



Ores, Electric 
Treatment of Processes for the ex- 
traction of metals from their ores. 

These processes are referable to three dis- 
tinct classes, viz. : 



Org. 



387 



[Osm« 



(i.) Those in which the reduction is effected by 
means of heat of electric origin. 

(2.) Those in which the reduction is effected by 
the combined action of heat and electrolysis. 

(3.) Those in which the reduction is effected by 
means of electrolysis only. 

Organ, Electric A wind organ, in 

which the escape of air into the different 
pipes is electrically controlled. 

In an electric organ, the keys, instead of oper- 
ating levers, as usual, to admit the passage of air 
into the pipes, merely complete the circuit of a 
"battery through a series of controlling electro-mag- 
nets. With such an arrangement, the keyboard 
can be placed at any desired distance. 

Electric organs have been constructed, in which 
a chemical or mechanical record is made of the 
notes struck by the performer, as well as the 
musical value of such notes. By such a device 
the musical creations of a composer are perma- 
nently recorded in characters that are capable of 
interpretation by a compositor skilled in musical 
notation, 

Orientation of Magnetic Needle. — (See 
Needle, Magnetic, Orientation of.) 

Origin, Point of The point where 

the axes of co-ordinates start or originate. 
(See Co-ordinates, Axes of.) 

Orthogonal. — Rectangular, or right-an- 
gled. 

Oscillating Discharge. — (See DisoJiarge, 
Oscillating.) 

Oscillating Needle. — (See Needle of Oscil- 
lation.) 

Oscillation, Centre of A point in 

a body swinging like a pendulum, which is 
neither accelerated nor retarded, during its 
oscillations, by the portions of the pendulum 
that are situated respectively above or below it. 

If all the mass were concentrated at the centre 
of oscillation the time of oscillation would be the 
same. 

The centre of oscillation is always below the 
centre of gravity. The vertical distance between 
the centre of oscillation and the point of support 
of a pendulum, determines the virtual length of 
the pendulum, and hence its number of vibra- 
tions per second. (See Pendulum, Laws of .) 



Oscillations, Electric 



-The series 



of partial, intermittent discharges of which 
the apparent instantaneous discharge of a 
Leyden jar through a small resistance actu- 
ally consists. 

These partial discharges produce a series of 
electric oscillations of the current in the circuit of 
the discharge, which consist of true to-and-fro 
or backward-and-forward motions of the elec- 
tricity. This phenomenon was discovered by 
Joseph Henry. 

Oscillations, Open-Circuit, Electric 

— Electric oscillations produced in open cir- 
cuits by the presence of electric pulses in 
neighboring circuits. 

Oscillatory Discharge. — (See Discharge, 
Oscillatory^) 

Oscillatory Electric Displacement. — (See 
Displacement, Electric, Oscillatory?) 

Oscillatory Electromotive Force. — An 

electromotive force which is rapidly periodic. 

Oscillatory Inductance. — (See Induc- 
tance, Oscillatory, Electric.) 

Oscillatory Induction. — (See Induction, 
Oscillatory?) 

Osmose. — The unequal mixing of liquids of 
different densities through the pores of a 
separating medium. 

If a solution of sugar and water be placed in a 
bladder, the neck of which is tied to a straight 
glass tube, and the bladder is then immersed in a 
vessel of pure water with the tube in a vertical 
position, the two liquids will begin to mix, the 
sugar and the water passing through the bladder 
into the pure water, and the pure water passing 
into the sugar and water in the bladder. This 
latter current is the stronger of the two, as will be 
shown by the water rising in the vertical glass 
tube. 

The stronger of the two currents, that is, the 
one directed towards the higher level, or the one 
which produces the higher level, is called the en- 
dosmotic current, and the weaker current the 
exos?notic current. 

Osmose, Electric A difference of 

liquid level between two liquids placed on 
opposite sides of a diaphragm produced by 
the passage of a strong electric current 



Osm.J 



388 



[Ozo. 



through the liquids between two electrodes 
placed therein. 

The higher level is on the side towards which the 
current flows through the diaphragm, thus appa- 
rently indicating an onward motion of the liquid 
with the current, or, in other words, the liquid is 
higher around the kathode than around the anode. 
The difference of level is most marked when 
poorly conducting liquids are employed. 

As a converse of this, Quincke has shown that 
electric currents are set up when a liquid is forced 
by pressure through a porous diaphragm. The 
term diaphragm currents has been proposed for 
these currents. Their electromotive force depends 
on the nature of the liquid, on the material of the 
diaphragm, and on the pressure that forces the 
liquid through the diaphragm. (See Phenomena, 
Electro-Capillary . Currents, Diaphragm.) 

Osmotic— Of or pertaining to osmose. 
(See Osmose?) 

Osteotome, Electric A revolving 

electrically propelled saw, employed in the 
surgical cutting of bones. 

An electric osteotome consists essentially of a 
form of revolving engine known as a dental en- 
gine, furnished with a circular saw, or other ro- 
tary cutter, driven or propelled by electricity. 

Outgoing Current.— (See Current, Out- 
going^ 

Outlet. — In a system of incandescent lamp 
distribution the places in a building where 
the fixtures or lamps are attached. 

The outlets are left in a building by the wire- 
man for the electric fixtureman to attach the de- 
vice intended to be used on the circuits so pro- 
vided. 



Output, Magnetic 



-The product of 



the magnetic flux by the magneto-motive 
force. 

Output of Dynamo-Electric Machine. — 

(See Machine, Dynamo-Electric, Output of.) 

Outrigger for Electric Lamp.— A device 
for suspending an electric arc lamp so as to 
cause it to stand out from the wall of a 
building. 

An outrigger and hood with lamp attached are 
shown in Fig. 414. 



Outrigger Torpedo. -(See Torpedo, Out- 
rigger.) 

Over-Compounded.— The compounding of 
a dynamo-electric madhine so as to produce 




Outrigger and Hood. 



an increase of voltage under increase of load. 
Over-compounding is generally employed for 
compensating for drop or loss of potential in the 
line or conductor, and is adjusted to a definite 
percentage of increase from light to full load in 
accordance with the amount of drop, or loss, for 
which such compensation was designed. 

Overhead Lines.— (See Lines, Overhead.) 

Overhead System, Continuous, of Motive 

Power for Electric Railroads (See 

Railroads, Electric, Continuous Overhead 
System of Motive Power for) 

Overload of Electric Motor.— (See Motor,. 
Electric, Overload oj '.) 

Overtones.— Additional, faint tones, ac- 
companying nearly every distinct musical 
tone, by the presence of which the peculiarity 
or quality of such tone is produced. (See 
Sound, Characteristics of) 

Overtones, Electric Electric vibra- 
tions produced in open-circuited conductors 
by electric resonance, of higher rates than the 
fundamental vibrations. 

The existence of electrical overtones necessitates 
the existence of electric nodes. (See Nodes, Elec- 
trical. ) 

Overtype Dynamo.— (See Dyna?no, Over- 
type.) 

Ozite. — An insulating substance. 
Ozokerite. — An insulating substance. 



Ozo.J 



389 



[Par. 



Ozone. — A peculiar modification of oxygen 
which possesses more powerful oxidizing 
properties than ordinary oxygen. 

Ozone is now generally believed to be tri- 
atomic oxygen, or oxygen in which the bonds are 
closed, thus: 



O- 



The peculiar smell observed when a torrent of 
electric sparks passes between the terminals of 
a Holtz machine, or a Ruhmkorff coil, is caused 
by the ozone thus formed. 

In a similar manner ozone is formed in the at- 



mosphere during the passage through the air of a. 
flash of lightning. 

During the so-called electrolysis of water, a com- 
pound formed by the union of two volumes of 
hydrogen with one volume of oxygen, some of the 
oxygen is given off in the form of ozone. Since 
ozone has a somewhat smaller volume than that 
of the oxygen forming it, the volume of the 
oxygen liberated is somewhat less than half the 
volume of the hydrogen. 

There are a number of different forms of ap- 
paratus designed for the production of ozone. 
They consist essentially either of means for pass- 
ing a torrent of electric sparks through air or for 
producing a species of polarization in the air. 



P. I), or p. (1. — A contraction frequently em- 
ployed for difference of potential. (See Poten- 
tial, Difference of.) 

Pacinotti Projections.— (See Projections, 
Pacinotti) 

Pacinotti Ring.— (See Ring, Pacinotti.) 

Pair, Astatic A term sometimes 

applied to an astatic couple. (See Couple, 
Astatic.) 

Palladium.— A metal of the platinum 
group. 

Metallic palladium has a tin-white color, and, 
when polished, a high metallic lustre. It is 
tenacious and ductile, and, like iron, can be 
welded at a white heat. It is very refractory and 
possesses in a marked degree the power of ab- 
sorbing or occluding hydrogen and other gases. 
It is not affected by oxygen at any temperature, 
nor readily affected by ordinary corrosive agents. 

Palladium Alloy.— (See Ally, Pal- 
ladium.) 

Pane, Magic A condenser formed 

of a sheet of glass covered on one side with 
pieces of tin-foil with small spaces between 
them pasted in some design on the glass. 

On the discharge of a Leyden jar through these 
metallic pieces, the design is seen as a series of 
minute sparks, which bridge the spaces between 
the adjacent pieces of foil. 



Pantelegraphy. — A system for the tele- 
graphic transmission of charts, diagrams, 
sketches or written characters. 

Pan telegraphy is more frequently called fac- 
simile telegraphy. (See Telegraphy, Fac-Simile.) 

Paper Carbons. — (See Carbons, Paper.) 

Paper Cut-Out,— (See Cut-Out, Paper :) 

Paper Perforator. — (See Perforator, 
Paper) 

Paper Winder, Automatic A de- 
vice, driven by clockwork, for automatically 
delivering the paper fillet on which a tele- 
graphic message is received. 

Parabolic Reflector.— (See Reflector, 
Parabolic) 

Parafflne. — A name given to various- 
solid hydrocarbons of the marsh gas series, 
that are derived from coal oil or petroleum by 
the action of nitric acid. 

Parafflne possesses excellent powers of insula- 
tion, and forms a good dielectric medium. Dried 
wood, boiled in melted parafflne, forms a fair in- 
sulating material. 

Parafflne Wire. — (See Wire, Paraffne) 

Paraffining. — Covering or coating with. 
paraffine. 

The parafflne is applied, while melted by heat, 
either by means of a brush, or by dipping the 
article in the fused mass. 



Par.] 



390 



[Par. 



Care must be taken in paraffining wooden or 
other absorbent articles, to dry them before im- 
mersing in the melted paraffine, since, if water be 
present, steam is formed explosively, and the 
melted paraffine scattered in all directions. 

Paragreles. — Lightning rods, intended to 
protect fields against the destructive action of 
hail. (See Hail, Assumed Electrical Ori- 
gin of.) 

It was formerly believed that hail is caused by 
electricity. It is now generally believed that the 
electricity in hail storms is caused by the hail. 
It will, therefore, readily be understood that para- 
greles can afford no real protection. 

Parallax. — The apparent angular displace- 
ment of an object when seen from two dif- 
ferent points of view. 

In reading the exact division on a scale to which 
a needle points, care must be taken to look di- 
rectly down on the needle, and not sideways, so 
as to avoid the error of displacement due to 
parallax. 

Parallel Circuit. — (See Circuit, Par all el.) 

Parallel Series. — (See Series, Parallel?) 

Parallelogram of Forces. — (See Forces, 
Parallelogram of.) 

Parallels, Magnetic Lines connect- 
ing places on the earth's surface at right 
angles to the isogonal lines, or lines of equal 
declination or variation. 

The magnetic parallels are at right angles to 
the magnetic meridians. The magnetic parallels 
lie in planes parallel to the magnetic equator. 
(See Needle, Magnetic, Declination of. Meridian, 
Magnetic.) 

Paramagnetic. — Possessing properties or- 
dinarily recognized as magnetic. 

Possessing the power of concentrating the 
lines of magnetic force. 

Paramagnetic is a term employed in contra- 
distinction to diamagnetic. (See Diamagnetic.) 
A paramagnetic substance, cut in the form of a 
bar whose length is much greater than its breadth 
and thickness, will, when suspended in a magnetic 
field in the manner shown in Fig. 415, take up a 
position of rest with its greatest length in the direc- 
tion of the lines of force, i. e., will point axial ly. 




Fig. 413. Diamagnetic 
Polarity 



In other words, the lines of force will so pass 
through the paramagnetic substance as to reduce 
the magnetic resistance of the circuit as much as 
possible. 

Paramagnetic sub-tances, therefore, concen- 
trate the linei of force on them. (See Resistance, 
Magnetic.} 

Diamagnetic substances, on the contrary, when 
placed as shown in Fig. 415, assume a position of 
rest with their least dimensions in the direction of 
the lines of force, i. e. 
they point eqtiatorially. 
This is the position in 
which they are placed 
by the lines of force, in 
order to insure the least 
magnetic resistance in 
the circuit of these lines. 
The magnetic resistance 
of diamagnetic sub- 
stances is great as com- 
pared with that of par- 
amagnetic substances. 

The term J err -mag- 
netic has been proposed 
for paramagnetic. If 
another term be required, which is doubtful, 
sidero-magnetic, proposed by S. P. Thompson, 
would appear to be preferable. (See Magnetic, 
Ferro. Magnetic, Sidero.) 

Tyndall believes that the magnetic polarity 
possessed by diamagnetic substances is the result 
of a distinct polar force, different in its nature 
from ordinary magnetism. His views, in this re- 
spect, are not generally accepted. (See Polarity, 
Diamagnetic.) 

Paramagnetically. — In a paramagnetic 
manner. {Set Paramagnetism.) 

Paramagnetism. — The magnetism of a 
paramagnetic substance. 

Parasitical Currents.— (See Currents, 
Parasitical.) 

Paratonnere. — A French term for light- 
ning rod, sometimes employed in English 
technical works. 

Lightning rod would appear to be the prefer- 
able term. 

Partial Contact. — (See Contact, Partial.) 
Partial Disconnection. — (See Disconnec- 
tion, Partial.) 



Par.] 



391 



[Pen, 



Partial Earth.— (See Earth, Partial^ 

Partial Reaction of Degeneration. — (See 
Degeneration, Partial Reaction of.) 

Passive State.— (See State, Passive.) 

Path, Alternative — The path or 

circuit taken by an impulsive discharge, in 
preference to another path or circuit, open to 
the discharge, although of enormously smaller 
ohmic resistance. 

The alternative path is the path taken by the 
discharge produced by what was formerly called 
lateral induction. 

The explanation of the reason the discharge 
takes the alternative path is that the counter-elec- 
tromotive force of self-induction of the circuit, 
produced by the impulsive discharge, is so great 
as to make the path of the circuit itself, although 
formed of conducting materials, practically non- 
conducting. 

If a Leyden jar is provided with discharge wires 
or conductors, as shown is Fig. 416, a discharge 



would pass across an air space in preference to- 
a metallic circuit, was greater for a thick copper 



t 




Fig. 416. Phenomena of Alternative Path. 

taking place at A, is accompanied simultaneously 
by an even longer spark at B, between the ends 
of two long open-circuit leads. 

To explain in a general manner the phenomena 
of the alternative path, we may say that the dis- 
charge at A, gives rise to electric oscillations in the 
leads connected with B, and that there are sent out 
into the surrounding medium radiations of pre- 
cisely the same nature as those which produce 
light, only of a wave length so long as to be un- 
able to produce on the eye the effects of light. 

If the space between the balls at B, is too great 
for the discharge to take place, the wires glow 
and throw out minute sparks or brushes of light. 

The action of the ordinary lightning arrester 
depends on the principle of the alternative path. 
The resistance of the metallic circuit, composed 
of the line and the instruments, is so great in the 
case of the impulsive discharge of a lightning 
flash, that the discharge takes place between a 
series of points connected with the line plate and 
another series of points connected with the ground 
plate. (See Arrester, Lightning. ) 

Dr. Lodge, who has studied the principle of 
alternative path in the case of lightning rods, 
finds that the distance at which the discharge 




Fig. 417. Edison Electric Pen. 

rod, 40 feet long, than for an iron rod of No. 27 
B. W. G. of 33.03 ohmic resistance. 

Patrol Alarm Box. 

—(See Box, Patrol 
Alarm?) 

Peltier Effect.— 

(See Effect, Peltier.) 

Pen Carriage. — 

(See Carriage, Pen.) 

Pen, Electric 

— A device for mani- 
fold copying, in which 
a sheet of paper is 
made into a stencil by 
minute perforations 
obtained by a needle 
driven by a small 
electric motor and the 
stencil afterwards em- 
ployed in connection 
with an inked roller 
for the production of 
any required number 
of copies. 

Mechanical pens are 
constructed on the same 
principle, the perfora- 
tions being obtained by 
mecnanical instead of 
by electric power. 

In the Edison electric 
pen, Fig. 417, the ^OX-Fig- 4l8. Electric Pendant. 
forations are made by an electric motor driven 
by a voltaic battery. The manifold press with 
its inked pad is shown to the left of the figure. 

Pendant Cord. — (See Cord, Pe7idant) 

Pendant, Electric A hanging fix- 




Pen.] 



392 



[Per. 



ture provided with a socket for the support of 
an incandescent lamp. 

A form of electric pendant is shown in Fig. 
418. 

Pendant, Flexible Electric Light 

— A pendant for an incandescent lamp formed 
i by the flexible conductors which support the 
lamp. 

The advantages procured by a flexible pendant 
are evident in that both the length of the flexible 
conductor from which the lamp is hanging and 
position of the lamp can be changed considerably. 

Pendulum Annunciator. — (See Annun- 
ciator, Pendulum or Swinging?) 

Pendulum, Electric A pendulum 

so arranged that its to-and-fro motions send 
electric impulses over a line, either by making 
or breaking contacts. 

An electrical tuning fork whose to-and-fro 
movements are maintained by electric im- 
pulses. 

Electric pendulums are employed in systems 
for the electrical distribution of time. 

Sometimes instead of using true pendulums for 
such purposes, coils, mounted on tuning forks, or 
on the ends of flexible bars of steel, called reeds, 
are used for the purpose of establishing cur- 
rents, or modifying the currents that are already 
passing in a circuit. The movement of a mag- 
netic diaphragm, as in the case of a telephone 
diaphragm, towards and from a coil of wire, is 
another illustration of an electric pendulum. 

Electric tuning-fork pendulums are employed 
in Delany's system of synchronous-multiplex teleg- 
raphy, and in Gray's harmonic-multiple teleg- 
raphy. (See Telegraphy, Synchronous-Multi- 
plex, Delany's System. Telegraphy, Gray's Har- 
monic-Multiple. ) 

Pendulum, Laws of — The laws 

which express the peculiarities of the motion 
of a simple pendulum. 

A simple pendulum is one in which the entire 
weight is considered as concentrated at a single 
point, suspended at the end of a weightless, in- 
flexible and inextensible line. 

The following are the laws of the simple pen- 
dulum : 

(1.) Oscillations of small amplitude are approx- 
imately isochronous ; that is, are made in times 
that are sensibly equal. (See Vibration or Wave, 
Amplitude of. Isochronism.) 



(2.) In pendulums of different lengths, the 
duration of the oscillations is proportional to the 
square root of the length of the pendulum. 

(3.) In the same pendulum, the length being 
preserved invariable, the duration of the oscilla- 
tion is inversely proportional to the square root 
of the intensity of gravity. 

The intensity of gravity, at any latitude, may 
be determined by the number of oscillations of a 
pendulum of a given length. In the same man- 
ner the intensity of a magnetic field, or the in- 
tensity of magnetization of a magnet, may be de- 
termined by the needle of oscillation, by observing 
the number of oscillations a needle makes in a 
given time when disturbed from its position of 
re>t. (See Needle of Oscillation.) 

Since a simple physical pendulum is a physical 
impossibility, the virtual length of a pendulum, 
that is, the vertical distance between its point of 
support and the centre of oscillation, is taken as 
the true length of the pendulum. 

If the irregularly shaped body, shown in Fig. 
419, whose centre of gravity is at G, is made to 
swing like a pendulum, either on 
S, or O, its oscillations will be 
performed in equal times, and 
the body will act as a simple 
pendulum, whose virtual length 
isS O. 

If, while suspended at S, it be 
struck at O, it will oscillate 
around S, without producing^. . 4T q 
any pressure on the supportin 
axis at S, on which it turns. If floating entirely 
submerged in a liquid, a blow at O, would cause 
it to move in a straight line in the direction of 
the blow, without rotation. 

The point O, is called the centre of percussion, 
or the centre of oscillation. The centre of oscil- 
lation is always below the centre of gravity. 

Pentane Standard. — (See Standard, Pen- 
iane.) 

Percussion, Centre of That point in 

a body suspended so as to move as a pendu- 
lum at which a blow would produce rotation, 
but no forward motion, or motion of transla- 
tion. 

Perforator, Paper An apparatus 

employed in systems of automatic telegraphy 
for punching in a fillet of paper the circular or 
elongated spaces that produce the dots and 




Centre 
of Oscillation. 



Per. 



393 



[Per, 



dashes of the Morse alphabet, when the fillet is 
drawn between metal terminals that form the 
electrodes of a battery. (See Telegraphy, 
Automatic) 

Perforator, Pneumatic A paper 

perforator operated by means of compressed 
air. (See Perforator, Paper) 

Period of Open-Circuit Oscillation. — (See 
Open-Circuit Oscillation, Period of.) 

Period of Simple-Harmonic Motion. — 
(See Motion, Si?nple-Har?nonic, Period of) 

Period of Titration. — (See Vibration, 
Period of) 

Period, Tibration The period of a 

single or a whole vibration in a conductor, in 
which an oscillatory vibration is being pro- 
duced by electrical resonance when respond- 
ing to its fundamental vibration. 

Hertz gives the following value for the vibration 
period: Calling T, the single or half vibration 
period ; L, the co-efficient of self-induction in abso- 
lute magnetic measure, and therefore expressed in 
centimetres; C, the capacity of the terminals, in 
electrostatic measure, and therefore also expressed 
in centimetres; v, the velocity of light in centi- 
metre-seconds, then, when the resistance of the con- 
ductor is small, T = it 

v 

Periodic and Alternate Discharge. — (See 
Discharge, Periodic. Discharge, Alternat- 
ing) 

Periodic Current, Power of The 

rate of transformation of the energy of a cir- 
cuit traversed by a simple periodic current. 




Fig. 420. Power of Periodic Current. — {Fleming.) 

If the thin line in the curve, Fig. 420, repre- 
sents the impressed electromotive force in an in- 
ductive circuit, and the thick line the correspond- 
ing current, then, at any instant, say at the point 
M, the rate at which energy is being expended on 
the circuit, is equal to the ordinate P M, multi- 
plied by the ordinate Q M. The mean power is 



the mean of all such products taken at points of 
time very near together. 

The power of a periodic current, or the work 
expended per second on such a circuit, is equal 
to half the product of the maximum values of the 
current, at any instant, and the maximum value 
of the impressed electromotive force, multiplied 
by the cosine of the angle of lag. 

Periodic Governor. — (See Governor, 
Periodic) 

Periodically Decreasing" Discharge. — 

(See Discharge, Periodically Decreasing) 

Periodicity. — The rate of change in the 
alternations or pulsations of an electric cur- 
rent. 

Periodicity of Auroras and Magnetic 
Storms. — (See Auroras and Magiietic 
Storms, Periodicity of) 

Permanency, Electric The prop- 
erty possessed by most metallic substances, 
while in the solid state, of retaining a constant 
electric conducting power at the same tem- 
perature. 

The electric permanency of hard drawn wire is 
small, since such wire becomes gradually an- 
nealed, and thus changed in its electric resist- 
ance. 

Matthiessen showed that some specimens of 
annealed German silver wire increased in their 
conducting power at the rate of about .02 per 
cent, yearly. 

Permanent Intensity of Magnetization. 

— (See Magnetization, Permanent, Intensity 
of) 

Permanent Magnet Toltmeter. — (See 
Voltmeter, Permatient Magnet) 

Permanent State of Charge on Telegraph 
Line. — (See State, Permanent, of Charge on 
Telegraph Line) 

Permeability Curve. — (See Curve, Per- 
meability) 

Permeability, Magnetic Conducti- 

bility for lines of magnetic forces. 

The ratio existing between the magnetiza- 
tion produced, and the magnetizing force pro- 
ducing such magnetization. 

If fx equals the permeability, B, the magnetiza- 



Per.] 



394 



[Phe. 



tion produced, or the intensity of magnetic induc- 
tion, and H, the magnetizing force; then, 



M = 



The permeability of non-magnetic materials, 
such as insulators, or non-magnetic metals, such as 
copper, etc., is assumed to be practically equal to 
that of air, or to unity. 

The magnetic permeability decreases as the 
magnetization increases. When a piece of iron 
has been magnetized up to a certain intensity, its 
permeability becomes less for any further magnet- 
ization; or, the substance shows a tendency to 
reach magnetic saturation. In good iron, this 
limit is reached at about 125,000 lines of force to 
the square inch of irea of cross section. 

The magnetic permeability varies greatly, not 
only with different specimens of iron, but also with 
the previous history of the iron, as to whether or 
not it has before been subjected to magnetization or 
demagnetization, and also as to whether the value 
of the permeability *is taken while the magnetiza- 
tion is increasing or decreasing. 

Permeameter. — An apparatus devised by 
S. P. Thompson, for roughly measuring the 
magnetic permeability. 

Thompson's permeameter consists essentially of 
a rectangular piece of soft iron, provided with a 
slot, for the reception of the magnetizing coil. A 
hole bored in one end of the block serves to receive 
the bar or rod of iron whose permeability is to be 
determined. On the magnetization of the bar to 
be tested, the square root of the force required to 
detach the rod from the lower surface of the iron 
block, is a measure of the permeation of the lines 
of magnetic forces through its end faces. 

Permeance, Magnetic — Magnetic 

permeability. (See Permeability, Magnetic.) 

Permeating", as of Lines of Force.— 

The passing of lines of force through a mag- 
netic substance. (See Permeability, Mag- 
netic^ 

Permeation, Magnetic ■ — The pass- 
age of lines of magnetic force through any 
permeable substance. 

Permissive Block System for Railroads. 

— (See Railroads, Permissive Block Sy 'stem 
for.) 



Pfluger's Law. — (See Law, PJll'cgers.) 

Phantom Wires. — (See Wires, Phantom.) 

Phase, Angle of Difference of, between 
Alternating Currents of Same Period 

The angle which measures the shift- 
ing of phase of a simple periodic current with 
respect to another due to lag or other cause. 

Phase, Shifting of, of Alternating Cur- 
rent A change in phase of current 

due to magnetic lag or other causes. 

Phase of Yibration.— (See Vibration r 
Phase of.) 

Phelps' Stock Printer. — (See Printer^ 
Stock, Phelps .) 

Phenomena, Electro-Capillary — 

Phenomena observed in capillary tubes at 
the contact surfaces of two liquids. 

Where acidulated water is in contact with 
mercury, each liquid possesses a definite sur- 
face tension, and each a definite shape of sur- 
face. The two liquids, however, do not actually 
touch, there being a small interval or space be- 
tween them. This space acts as a minute accu- 
mulator. But the liquid and water, being different 
substances in contact, possess different potentials. 
Any cause which alters the shape of these con- 
tact surfaces, and consequently the extent of the 
spaces between them, necessarily alters the capa- 
city of the condenser, and consequently the dif- 
ference of potential. Therefore the mere shaking 
of the tube, or heating it, will produce electric 
currents from the resulting differences of po- 
tential. Conversely, an electric current sent 
across the contact-surfaces will produce motion as 
a result of a change in the value of the surface 
tension. An electro-capillary telephone has been 
constructed on the former principle, and an 
electrometer on the latter. (See Electrometer, 
Capillary.) 

Phenomena, Porret An increase 

in the diameter of a nerve fibre in the neigh- 
borhood of the positive pole when traversed 
by a voltaic current. 

When a voltaic current passes through fresh 
living substance the contents of the muscular fibre 
exhibit a streaming movement in the direction the 
current is flowing, viz., from the positive to the 



I he.] 



395 



[Pho. 



negative. This causes the fibre to swell up or 
increase in diameter at the negative electrode. 

Pherope. — A name sometimes applied to 
a telephote. (See Telephote) 

Phial, "Leyden A name sometimes 

applied to a Leyden jar. {See Jar, Leyden?) 

Philosopher's Egg.— (See Egg, Philoso- 
phers?) 

Phonautograph.— An apparatus for the 
automatic production of a visible tracing of 
the vibrations produced by any sound. 

Phonautographic apparatus consists essentially 
of devices by which the sound waves are caused 
to impart their to-and-fro movements to a dia- 
phragm, at the centre of which a pencil or tracing 
point is attached. The record is received on a 
sheet of paper, or wax, or on a smoked glass or 
other suitable surface. 

Leon Scott's Phonautograph, which is among 
the forms best known, consists of a hollow conkal 




Fig. 421. Scott 's Phonautograph. 

vessel A, Fig. 421, with a diaphragm of parch- 
ment stretched tightly like a drumhead over its 
smaller aperture B. A tracing point attached to 
the centre of the diaphragm, traces a sinuous 
line on the surface of a soot-covered cylinder C, 
that is uniformly rotated under the tracing point. 
As the cylinder is advanced a short distance with 
every rotation, a sinuous spiral line is traced on 
the surface. 

Phone. — A term frequently used for tele- 
phone. 

Phonic Wheel.— (See Wheel, Phonic) 

Phonogram.— A record produced by the 
phonograph. (See Phonograph) 

Phonograph.— An apparatus for the re- 
production of articulate speech, or of sounds 



of any character, at any indefinite time after 
their occurrence, and for any number of times. 
In Edison's phonograph the voice of the- 
speaker, received by an elastic diaphragm of thin 
sheet iron or other similar material, is caused to 
indent a sheet of tin-foil placed on the surface of 
a cylinder C, Fig. 422, that is maintained at a 
uniform rate of rotation by the crank at W.. In. 




Fig. 422. 

the form shown in Fig. 422, the motion is by hand. 
In a later improved form the cylinder is driven by 
means of an electric motor or by clockwork. 

In order to reproduce the speech or other 
sounds the phonogram record is placed on the 
surface of a cylinder similar to that on which it 
was received (or is kept on the same surface), 
and the tracing point, placed at the beginning of 
the record and being maintained against it by 
gentle pressure, is caused, by the rotation of ? 
cylinder, to follow the indentations of the phono- 
gram record. As the point is thus moved up and- 
down the hills and hollows of the record surface,, 




Fig. 423. Edison's Improved Phonograph. 

the diaphragm, to which it is attached, is given to- 
and-fro motions that exactly correspond to the 
to-and-fro motions it had when impressed origin- 
ally by the sounds it recorded on the phono- 
gram record. A person listening at this dia.~ 



Pho.] 



396 



[Pho. 



phragm will therefore hear an exact reproduction 
of the sounds originally uttered. 

In this manner the voices of relatives, dis- 
tinguished singers or statesmen can be preserved 
for future generations. 

In Edison's improved phonograph the record 
surface consists of a cylinder of hardened wax. The 
rotary motion of the cylinder is obtained by means 
of an electric motor. Two diaphragms are used, 
one for recording, and one for reproducing the 
sound waves. As shown in Fig. 423, the record- 
ing diaphragm is in position against the cylinder. 
The recording diaphragm is made of malleable 
glass. The reproducing diaphragm is formed of 
bolting silk covered with a thin layer of shellac. 

In the Graphophone of Bell and Tainter the 
point attached to the diaphragm is caused to cut 




Fig. 424. Bell and Tainter 's Graphophone. 
or engrave a cylinder of hardened wax. Two 
separate diaphragms are employed, one for speak- 
ing, and the other for hearing. 

The recording surface is made of a mixture of 
beeswax and paraffine. A uniformity of rotation of 
the cylinder is obtained by means of a motor pro- 
vided with a suitable governor. An ordinary con- 
versa' ion of some five minutes, it is claimed, can 
, be recorded on the surface of a cylinder 6 inches 
Ion or and 1^ inch in diameter. 

In the Gramophone of Berliner, a circular plate 
of metal, covered with a film of finely divided oil 



or grease, receives the record in a sinuous, spiral 
line. This record is subsequently etched into the 
metal by any suitable means, or is photographic- 
ally reproduced on another sheet of metal. 

Glass covered with a deposit of soot is some- 
times employed for the latter process. The ap- 
paratus is shown in Fig. 425, as arranged for the 
reproduction of speech. 

In Mr. Berliner's apparatus, the record surface 
is impressed by a point attached to the trans- 
mitting diaphragm, in a direction parallel to the 
record surface, and not, as in the instrument of 
Mr. Edison, in a direction at right angles to the 
same. This method would appear to be the best 
calculated for a more exact reproduction of ar- 
ticulate speech, since it permits comparatively 
loud speaking or singing, without interfering 




Fig. 423. Berliner's Gramophone. 



with the quality of the reproduced sounds. Since 
the resistance to indentation, or vertical cutting, 
increases more rapidly than the increase in the 
amplitude of vibration of the cutting point, it 
follows that the louder the sounds recorded by the 
phonograph or graphophone, the less complete 
would be the quality of the reproduced sounds, 
or the less the probability of the peculiarities of 
the speaker's voice being recognized. In order 
to avoid this, the speaker in the phonograph and 
the graphophone speaks in an ordinary conversa- 
tional tone only. (See Vibration or Wave, Am- 
plitude of ) 

For purposes of dictation, and, indeed, most 
commercial purposes, this is rather an advantage 
than otherwise. 

Phonograph Eecord. — (See Record, 
Phonograph.) 

Phonoplex. — Literally sound folds. 

A system of telegraphy. (See Telegraphy, 
Phonoplex?) 



Pho.] 



397 



[Pho. 



Phonoplex Telegraphy. — (See Telegra- 
phy, Phonoplex?) 

Phonopore. — A modified form of har- 
monic telegraph. 

Phonozenograph. — An instrument devised 
by De Feltre to indicate the direction of a 
distant sound. 

A Deprez-D'Arsonval galvanometer, a Wheat- 
stone's bridge, and a microphone of peculiar con- 
struction, are placed in the circuit of a voltaic 
battery and a receiving telephone. The observer 
determines the direction of the distant sound by 
means of the sounds heard under different condi- 
tions in the telephone. 

Phosphoresce. — To emit phosphorescent 
light. 

Phosphorescence. — The power of emitting 
light, or becoming luminous by simple ex- 
posure to light. 

Bodies that possess the property of phosphor- 
escence, when exposed to a bright light acquire 
the power, when subsequently carried into the 
dark, of continuing to emit light, for periods 
varying from a few seconds to several hours. 
The diamond, barium and calcium sulphides, 
dry paper, silk, sugar, and compounds of ura- 
nium, are examples of phosphorescent substances. 

The effects of phosphorescence appear to be 
due, in some cases, to sympathetic vibrations set 
up in the molecules of the phosphorescent body 
by the exciting light. (See Vibrations, Sympa- 
thetic.) 

In other cases, however, that are not exactly 
understood, the wave length of the emitted light 
is more rapid than that of the exciting light. 

The fire-fly, the glow-worm, and decaying 
animal or vegetable matter, exhibit a species of 
phosphorescence that appears to be due to the ac- 
tual oxidation or gradual burning of a peculiar, 
specific, chemical substance. 

Phosphorescence may therefore be divided into 
two classes, viz.: 

(i.) Physical phosphorescence, or that produced 
by the actual impact of light, and, 

(2.) Chemical phosphorescence, or that caused 
by actual chemical combination or combustion of 
a specific substance. This is sometimes called 
spontaneous phosphorescence. 

Physical phosphorescence may be produced in 
a variety of ways, viz.: 



(i.) By an Elevation of Temperature: 
A variety of fluorspar, called chlorophane, 
shines with a beautiful greenish blue light when 
heated to less than a red heat. Here the non- 
luminous rays are apparently transformed into 
luminous rays. 

A phosphorescent substance like fluorspar 
eventually loses its ability to phosphoresce. ' It 
regains it, however, on exposure to the light, i. e., 
if such an exhausted body be exposed to sunlight it 
again phosphoresces on exposure to non-luminous 
heat. The light emitted, during phosphorescence 
by heat, is, probably, wholly due to potential 
energy acquired during exposure to the light. 
(See Luminescence.) The phosphorescence by 
heat exhibited by fluorspar is sometimes called 
fluorescence. It is preferable, however, to call 
the phenomena phosphorescence. (See Fluores- 
cence. ) 

(2.) By Mechanical Effects: 

The flashes of light emitted during the attri- 
tion or friction of some bodies, when not traceable 
directly to electricity, are, most probably, to be 
ascribed to phosphorescence. 

(3.) By Molecular Bombardment. 

The molecular bombardment due to the mole- 
cules of residual gas shot off from the negative 
electrode of an exhausted receiver through which 
an electric discharge is passing, produces many 
brilliant effects of phosphorescence. 

(4.) By Electricity. 

An electric spark produces phosphorescence in 
such substances as canary glass, solution of sul- 
phate of quinine, etc., etc. 

(5.) Exposure to Sunlight, or, in fact, to any 
light. 

The different rays of the sun are not equally 
able to excite phosphorescence. As a rule the 
violet or ultra violet rays excite the greatest phos- 
phorescence. The light excited is often, though 
not always, of a greater wave length than the 
exciting light. 

Phosphorescent paints for rendering the posi- 
tion of a push button, electric call, match safe, 
gas pendant or some other similar object visible 
at night, consist essentially of sulphides of cal- 
cium or barium, or of mixtures of the same. 

Phosphorescence, Chemical A 

variety of phosphorescence, in which the emit- 
ted light is produced by the actual combustion 



398 



[Pho. 



of a specific chemical substance by the oxygen 
of the air. 

Chemical phosphorescence is seen in the fire- 
fly and the glow-worm. (See Phosphorescence.) 

Phosphorescence, Electric Phos- 
phorescence caused in a substance by the 
passage of an electric discharge. 

The phosphorescent material is placed in an 
exhausted glass tube, as shown in Fig. 426, and 
submitted to the action of a series of discharges, 
as from a Ruhmkorff coil, or Holtz machine. 
The violet-blue light of such discharge is very 
efficient in producing phosphorescence. Phosphor- 
escence is thus effected by subjecting the phos- 
phorescent material to the molecular bombard- 
ment which is produced by such discharges in a 
high vacuum. (See Bombardment, Molecular .) 




Fig. 42 b. Electric Phosphorescence. 

Phosphorescence, Physical Phos- 
phorescence produced in matter by the actual 
impact of light waves resulting in a vibratory 
4 motion of the molecules of sufficient rapidity 
to cause them to emit light. 

Physical phosphorescence is distinguished from 
chemical phosphorescence in that in the former 
the energy required to produce molecular vibra- 
tions is imparted by the light to which the phos- 
phorescent body is exposed, while in chemical 
phosphorescence the energy producing the light 
is derived from the chemical potential energy 
of the specific substance burned. (See Phosphor- 
escence. ) 

Phosphorescent — Possessing the proper- 
ties or qualities of phosphorescence. 

Phosphorescing. — Emitting phosphores- 
cent light. (See Phosphorescence) 

Phosphorescope. — An apparatus for meas- 
uring the phosphorescent power of any sub- 
stance. (See Phosphorescence) 



Phosphorus. Electric Smelting of 

— An electric process for the direct production 
of phosphorus. 

In the electric smelting of phosphorus, the 
crude material, consisting of a mixture of bones or 
animal phosphates and carbon, is fed into a space 
between two electrodes connected to the poles of 
a source of powerful alternating currents. The 
apparatus is similar in general to the Cowles fur- 
nace for the reduction of aluminium. The heat 
produced by the alternating currents decomposes 
the phosphates, and the volatilized phosphorus 
is condensed in suitable chambers. 

Photochronograph. — An electric instru- 
ment for automatically recording the transit 
of a star across the meridian. 

In a small camera connected with the eye-piece 
of the transit instrument is placed a sensitized 
plate. 

A sidereal clock has an electric attachment to 
its pendulum, so made that a shutter alternately 
exposes and conceals the photographic plate, and 
thus permits the image of a star to be formed on 
the plate at intervals during its passage across 
the field of the telescope. An image of the spider 
lines is afterwards fixed on the plate by the light 
of a lamp, held for a few moments before the ob- 
ject glass of a telescope. A shutter is provided, 
by means of which this light is prevented from 
falling on the trail of the star across the fie'd of 
the glass. In this manner the time of passage of 
the star across the meridian is automatically re- 
corded on the photographic plate. 

The photochronograph is also adapted for 
similarly automatically recording the transit or 
passage of any heavenly body across any imagin- 
ary line in the heavens. 

Photo-Electric Cell.— (See Cell, Photo- 
Electric) 

Phot o-Electricity. — ( See Electricity \ 
Photo) 

Photo-Electromotive Force. — (See Force, 
Electromotive, Photo) 

Photometer. — An apparatus for measuring 
the intensity of the light emitted by any 
luminous source. 

There are various methods for measuring the 
intensity of a beam of light passing through any 
given space, or emitted from any luminous 



Fho. 



399 



[Pho. 



source; these methods are embraced in the use 
of the following apparatus: 

(i.) Calorimetric Photometer, in which the light 
to be measured is absorbed by the face of a 
thermo-electric pile, and the electric current 
thereby produced is carefully measured. Since 
■obscure radiation or heat will also thus produce 
an electric current, it is necessary first to absorb 
all the heat by passing the beam of light through 
an alum cell. 

(2.) Actinic, or Chemical Photometers, in which 
the intensity of the light is estimated by a com- 
parison of the depth of coloration produced on a 
fillet of photographic paper under similar con- 
ditions of exposure to a standard light, and the 
light to be measured. 

The combination of pure hydrogen and chlorine, 
or the decomposition of pure mercurous chloride, 
have been employed for the purpose of determin- 
ing the intensities of two lights by measuring the 
amount of chemical action effected. 

(3.) Shadow Photometers, in which a shadow 
produced by the light to be measured is compared 
with a shadow produced by a standard candle, 
(See Candle , Standard.) 





Fig. 427. The Shadow Photometer. 

Rumford's photometer, shown in Fig. 427, is 
an example of this form of instrument. The 
standard candle, shown at L, casts a shadow C", 
of an opaque rod C, on the screen at B. 

The light to be measured L', is moved away 
from the screen until its shadow C, on the screen 
at A, is judged by the eye to be of the same 
depth. The distance between the screen and the 
lights is then measured in straight lines. The 
relative intensities of the two lights are then pro- 
portional to the squares of their distances. If, for 
example, the candle be at 10 inches from the 
screen, and the lamp at 40 inches, then the 
intensities are as io 2 : 40 - or as 100 : 1,600, or the 
lamp is a 16 candle-power lamp. 



This photometer is based on the fact that the 
shadow of each source is illumined by the light 
of the other source. 

These results are more accurate if the two 
shadows are adjoining or nearly adjoining. 

(4.) Translucent -Disc Photometers. — The light 
to be measured and a standard candle are placed 
on opposite sides of a sheet of paper the centre of 
which contains a grease spot. The standard 
candle is kept at a fixed distance from the paper 
and both it and the paper are moved towards or 
from the light to be measured until both sides of 
the paper are adjudged to be equally illumined. 

In Bunsen's photometer a vertical sheet of 
paper with a grease spot at its centre, is exposed 
to the illumination of a standard candle on one 
side, and the light to be measured on the other. 

The sheet of paper is placed inside a dark box 
provided with two plane mirrors placed at such 
an angle to the paper that an observer can readily 
see both sides of the paper at the same time. 

This box can be slid along a graduated, hori- 
zontal scale towards, or from, the light to be 
measured, and carries with it the standard candle 
mounted on it at a constant distance of 10 inches. 
If the box is too near the light to be measured, 
the grease spot appears brighter on the side of the 
sheet of paper nearest the candle. If too near 
the candle, it appears brighter on the side of the 
sheet of paper nearest the light to be measured. 
The position in which the spot appears equally 
bright on both sides, is the position in which both 
sides of the paper are equally illumined, and the 
relative intensities of the two lights are then 
directly as the squares of their distances from the 
sheet of paper. 

Shadow, and translucent-disc photometers 
being dependent on equal illumination, are re- 
liable only when the color of the lights compared 
is the same. For the determination of the photo- 
metric intensity of very bright lights, the standard 
candle is replaced by a carcel lamp, a standard 
gas jet, or by the light emitted by a given mass 
of platinum, heated to incandescence by a given 
current of electricity. (See Lamp, Carcel. Gas- 
jet, Carcel Standard. Light, Platinum Stand- 
ard.) 

Preece's photometer belongs to the class of 
translucent-disc photometers. A tiny incandes- 
cent lamp is placed in a box, the top of which has 
a white paper screen on which is a grease spot. 
The box is placed in the street where the intensity 
of illumination is to be measured, and the inten- 



riio.] 



400 



[Pho. 



sity of the light of the incandescent lamp is 
varied until the grease spot disappears. The 
current of electricity then passing through the 
incandescent lamp acts as the measure of the 
illumination. 

In the case of the shadow photometer, or of 
Bunsen's photometer, if the intensity of illumina- 
tion is the same, the relative intensities of the two 
lights may be determined as follows: 

Calling I, and i, respectively the relative inten- 
sities of the standard light, and the light to be 
measured, and D, and d, their respective dis- 
tances from the screen, then 

I : i : : D 2 : d 2 , or I X d* = i X D 2 ; 



that is, i 



-(ft) 



Or, the intensity of the light to be measured is 

/d 2 \ 

I =— 1 times the intensity of the standard light. 

If, for example, D and d, represent io and ioo 
inches, respectively, the intensity of i, is ioo times 
the intensity I, the standard l'ght. 

(5.) Dispersion Photometers. A class of pho- 
tometers in which, in order to more readily com- 
pare or measure a very bright or intense light, 
like that of an arc lamp, the intensity of the light 
is decreased by dispersion a readily measurable 
amount. 

Ayrton &* Perry' 1 s Dispersion Photometer. — A 
photometer in which, in order to bring an in- 
tensely bright light, like an electric arc light, to 




Fig. 428. Ayrton & Perry' 's Dispersion Photometer. 

such an intensity as will permit it to be readily 
compared with a standard candle, its intensity is 
weakened by its passage through a diverging 
(concave) lens. 

Ayrton & Perry's dispersion photometer is 
shown in two different positions, Figs. 428 and 
429. The apparatus is supported on a tripod 
stand E, arranged so as to obtain exact leveling. 



A plane mirror H, movable around a pin placed 
directly under its centre, can be rotated and thus 
reflect the light after its passage through the 
diverging lens, while still maintaining its distance 
from the electric light. 

The horizontal axis of this mirror is inclined 
45 degrees to its reflecting surface in order to 
avoid errors arising from varying absorption at 
different angles of reflection. 

The inclination of the beam to the horizontal 
is indicated by means of an index attached to the 
mirror and moving over the graduated circle G. 

A black rod A, casts its shadow on a screen of 
white blotting paper B. A standard candle, 
placed in the holder D, casts its shadow alongside 
the shadow cast by the electric light. The lens 
is now displaced until the shadow of the electric 
light is of the same intensity as that of the candle, 
when viewed successively through sheets of red 
and green glass. 

A graduated scale serves to mark the distances 
of the candle and the lens, respectively, from the 
screen, from which data the intensity ot the 
electric light may be calculated. 




Fig. 42 q. Ayrton and Perry's Dispersion Photometer* 

(6.) Selenium Photometers. — Instruments ina 
which the relative intensities of two lights are de- 
termined by the variations produced in a selenium 
resistance. 

In Siemens' Selenium photometer a selenium 
cell is employed in connection with an electric 
circuit for determining the intensity of light. 

The tube A B, Fig. 430, is furnished at A, with 
a diaphragm, and at B, with a selenium plate, 
connected by wires G G, with the circuit of a. 
battery and a galvanometer. 

A graduated scale L M, bears the standard 
candle N. The tube A B, is capable of rotation 
on the vertical axis F. A reflecting mirror gal- 
vanometer is used in connection with the selenium- 
photometer. The light to be measured is placed. 



PIioJ 



401 



[Pho. 



at right angles to the scale L M, and the tube A 
B, directed towards it, and the galvanometer de- 
flection compared with the deflection obtained 
when turned towards the standard candle. 

(7.) Gas-jet Photometers. — Instruments in 
which the candle-power of a gas-jet is determined 
by measuring the height at which the jet burns 
when under unit conditions of volume and press- 
ure of gas consumed. 




Fig. 4 JO. Siemens' Selenium Photometer. 

In determining the candle-power of an intense 
light like the electric arc light, a large gaslight 
is used instead of a standard candle, and the 
photometric power of this gaslight is carefully 
determined by comparison with a gas-jet photom- 
eter. (See Jet, Gas, Car eel Standard.) 

Photometer, Actinic A photom- 
eter in which the intensity of any light is meas- 
ured by the amount of chemical decomposi- 
tion it effects. (See Photometer.) 

In some actinic photometers the intensity of the 
light to be measured is determined by the com- 
parison of the depth of coloration of a sensi- 
tized film under similar conditions of exposure 
to a standard light and the light to be measured. 

Photometer, Calorimetric A pho- 
tometer in which the light to be measured is 
absorbed by the face of a thermo-electric pile, 
and the intensity of the light estimated from 
the strength of the electric current thereby 
produced. 

In order to avoid the error arising from the 
current produced from the absorption of the ob- 
scure radiation from the light, all the heat is first 
absorbed by passing the light through an alum 
cell. (See Photometer.) 

Photometer, Chemical A photom- 
eter in which the intensity of the light to be 



measured is determined from the amount of 
chemical action effected in a given time. 

Photometer, Dispersion A photom- 
eter in which the light to be measured is de- 
creased in intensity a known amount so as to 
more readily permit it to be compared with a 
standard light of much smaller intensity. 
(See Photometer.) 

Photometer, Electric An electrical 

instrument for measuring the intensity of 
illumination. 

A form of electric photometer invented by C. 
R. Richards depends for its indications on the 
variations that occur in the resistance of a wire on 
change of temperature. An iron wire, whose 
change of temperature is utilized for measuring 
the intensity of any light to whose radiations it is 
opposed, is covered by a deposit of lampblack. 
On exposure to the light whose intensity is to 
be measured, the light is absorbed by the lamp- 
black and an increase in temperature occurs. 

In order to get rid of the heat rays that are 
associated with the light rays, the rays before 
falling on the soot-covered wire are caused to pass 
through a solution of alum ; the intensity of the 
light is then calculated by reference to the change 
in the resistance of the soot-covered wire, which 
is made one of the arms of a Wheatstone bridge. 

Photometer, Gas-Jet — A photom- 
eter in which the candle-power of a gas-jet is 
estimated from a measurement of the height 
at which the jet burns under unit conditions 
of volume and pressure. (See Photo7?zeter.) 

Photometer, Jet An apparatus for 

determining the candle power of a luminous 
source by means of the height of a jet of the 
gas, whose candle-power is being determined, 
when burning under constant conditions as 
to pressure, etc. (See Jet, Gas, Carcel 
Standard,) 

Photometer, Selenium A photom- 
eter in which the intensity of a light is esti- 
mated by the comparison of the changes in 
the resistance of a selenium resistance suc- 
cessively exposed under similar conditions to 
this light and to a standard light. (See 
Photometer^ 

Photometer, Shadow A photom- 
eter in which the intensity of the light to be 



Pho.] 



402 



[Pko. 



measured is estimated by a comparison of 
the distances at which it and a standard light 
produce a shadow of the same intensity. 
(See Photometer?) 

Photometer, Translucent Disc A 

photometer in which the light to be measured 
is placed on one side of a partly translucent 
and partly opaque disc, and a standard can- 
dle is placed on the opposite side, and the in- 
tensity of the light estimated by the distances 
of the light from the disc when an equal illu- 
mination of all parts of the disc is obtained. 
(See Photometer?) 

When the illumination of the opposite sides of 
such a disc is equal, the relative positions of the 
transparent and opaque portions of the disc are 
indistinguishable. 

Photometer, Varley's A form of 

photometer in which the intensity of the light 
to be measured is determined from the rel- 
ative openings of two concentric circular 
diaphragms placed in two rotating discs, and 
through which the standard light and the 
light to be measured respectively pass. 

The general arrangement of Varley's photo- 
meter is shown in Fig. 431. The concentric cir- 




Fig. 43 T. Varley*s Photometer. 

cular apertures extend circumferentially 180 de- 
grees, and are reversed so that when one half 



ring is fully open, the other is completely closed ; 
or, if one ring, say the outer, is opened 160 de- 
grees, the inner is opened 20 degrees. The 
quantity of light then which passes through the 
outer ring from the light to be measured is eight 
times that passed through the inner ring. The 
circle is divided into 2,000 parts, instead of into 
360 degrees, and, by means of a vernier, these 
parts are further divided into 10 parts, permitting 
a reading of the 20,000 divisions. 

Two collimeters placed in front of the disc, 
project a disc with a black centre, and a luminous 
spot respectively. The discs are regulated until 
the light projected on the screen produces a uni- 
form disc. This is readily ascertained, since if 
one or the other predominate, a disc with gray 
spot, or a gray marginal ring with a bright spot, 
will appear. 

The general appearance of the circular dia- 
phragm, corresponding to different relative posi- 
tions of the two discs, is shown in Fig. 432. 

Fig: 432. Circular Diaphragm of Varley's Photometer. 

Photometric— Of or pertaining to the 
photometer. (See Photometer?) 

Photometrically. — In a photometric man- 
ner. *? 

Photophone. — An instrument invented by 
Bell for the telephonic transmission of artic- 
ulate speech along a ray of light instead of 
along a conducting wire. 

A beam of light, reflected from a diaphragm 
against which the speaker's voice is directed, is 
caused to fall on a selenium resistance inserted in 
the circuit of a voltaic battery, and a telephone. 
The changes thus effected in the resistance of the 
circuit by the varying amounts of light reflected on 
the selenium resistance from the diaphragm, while 
moving to-and-fro under the influence of the speak- 
er's voice, produce in the receiving telephone a 
series of to-and-fro movements similar to those im- 
pressed on the transmitting diaphragm. One lis- 
tening at the telephone can hear whatever has been 
spoken in the neighborhood of the transmitting 
diaphragm. Telephonic communication can, 
therefore, by such means be carried on along a 



Xho.] 



403 



[Pie, 



ray or beam of light, theoretically through any 
distance. (See Resistance, Selenium.) 

A block of vulcanite or of certain oth f r sub- 
stances may be used as the receiver, since it has 
been discovered that a rapid succession of flashes 
of light produces an audible sound in small masses 
of these substances. 

The term sonorescence has been proposed for 
the property possessed by such substances of 
emitting sounds when subjected to such inter- 
mittent flashes of light. (See Sonorescence.) 

Photophore, Trouve's — An appa- 
ratus in which the light of a small incandescent 
electric lamp is employed for purposes of 
medical exploration. 

A small incandescent lamp is placed in a tube 
containing a concave mirror and a converging 
lens. 

Photo-Telegraphy. — The electric produc- 
tion of pictures, writing, charts or diagrams 
at a distance. 

Photo-Telegraphy is sometimes called telepho- 
tography; it is a species of fac-simile telegraphy. 
{See Telegraphy ', Pac-Simile. Telephotography .) 

Photo- Voltaic Effect.— (See Effect, Photo- 

Voltaic?) 

Physical Change. — (See Change, Phy- 
sical) 

Physical Phosphorescence. — (See Phos- 
phorescence, Physical.) 

Physiological. — Pertaining to physiology. 

Physiological Rheoscope. — (See Rheo- 
scope, Physiological. ) 

Physiologically. — In a physiological man- 
ner. 

Physiology, Electro The study of 

electric phenomena of living animals and 
plants. 

Living animals and plants present electric 
phenomena, due to the electricity naturally pro- 
duced by them. It is the province of electro- 
physiology to ascertain the causes and effects of 
these phenomena. 

Piano,- Electric A piano in which 

the strings are struck by hammers actuated 
by means of electro-magnets, instead of by 
the usual mechanical action of levers. 



An electric piano-action is mainly useful in per- 
mitting the instrument to be played at any dis- 
tance from the key-board, it is also of value 
from the ease it affords in recording the pieces 
played. 

It fails, however, to properly preserve the vari- 
ous modulations of force so requisite for brilliant 
instrumentation. 

Pickle. — An acid solution in which me- 
tallic objects are dipped before being gal- 
vanized, or electroplated, in order to 
thoroughly cleanse their surfaces. 

The pickle used for the preparation of iron for 
galvanization is a weak solution of sulphuric acid 
in water. Various acids, or acid liquids, are em- 
ployed for insuring the thorough cleansing of 
metallic surfaces so necessary in order to ensure 
an even, uniform, adherent coating of metal by 
the process of electroplating. (See Plating, 
Electro. ) 

Piece, Magnetic Proof A para- 
magnetic rod, ellipsoid or sphere employed 
for ascertaining the distribution of magnetism 
over a magnet by the force required to de- 
tach the same. (See Paramagnetic) 

Prof. S. P. Thompson points out the fact 
that the presence of the proof-piece so alters the 
distribution of magnetism on the magnet to be 
measured as to render this method unreliable. 
He also shows that the force required for detach- ' 
ment depends on the magnetic permeability of 
the proof-piece, as well as on its shape and its 
position in the magnetic circuit. 

Pieces, Month Openings into air 

chambers, generally circular in shape, placed 
over the diaphragms of telephones, phono- 
graphs, gramophones or graphophones to 
permit the ready application of the mouth in 
speaking, so as to set the diaphragm into 
vibration. 

The mouth-piece may be also utilized by the 
ear of an observer listening so as to be affected 
by its vibrations. 

Pieces, Pole, of Dynamo-Electric Ma- 
chine Masses of iron connected with 

the poles of the field magnet frames of 
dynamo-electric machines, and shaped to 
conform to the outline or contour of the 
armature. 



Pil. 



404 



[PiL 



The pole pieces are made in a variety of forms, 
but in all cases are so shaped as to conform to the 
outline of the space in which the armature rotates. 

The pole pieces are brought as near as possible 
to the armature, so as to increase the intensity of 
the magnetic induction. The intervening air 
space should be as thin as possible, but of as large 
an area as convenient. 

The opposite pole pieces should not have their 
extensions brought too near together, as this will 
permit of serious loss through magnetic leakage. 
The distance between them should be as many 
times the depth of the armature windings as 
possible. (See Leakage, Magnetic.) 

Rounded edges are preferable to sharp edges 
for the same reason. 

Pile, Dry A voltaic pile or battery 

consisting of numerous cells, the voltaic 
couple in each of which consists of sheets of 
paper covered with zinc-foil on one side and 
black oxide of manganese on the other. 

Various modifications of the above form have 
been made. 

The term dry-pile is a misnomer, since all such 
piles contain substances moistened by liquid 
electrolytes. 

Pile, Muscular, Matteucci's A vol- 
taic battery or pile, the elements of which are 
formed of longitudinal and transverse sections 
of muscle alternately connected. 

Matteucci's experiments appear to show that 
the lower the animal is in the scale of creation, 
the stronger is the current produced, and the 
longer its duration. Du Bois-Reymond has 
shown that the muscular current is not due to 
contact, but to the differences of electric poten- 
tial naturally possessed by the muscles them- 
selves. 

The nerves also possess the power of producing 
differences of electromotive force, and hence cur- 
rents. (See Electrotonus. ) 

Pile, Thermo, Differential A ther- 
mopile in which the two opposite faces are 
exposed to the action of two nearly equal 
sources of heat in order to determine accu- 
rately the differences in the thermal intensities 
of such sources of heat. 

Pile, Thermo-Electric A number 

of separate thermo-electric couples, united in 



series, so as to form a single thermo-electric 
source. (See Couple, Thermo-Electric?) 

A thermo- electric pile is sometimes called a 
thermo-electric battery. 

Fig. 433 shows Nobili's thermopile, in which 
a number of bismuth- 
antimony thermo-elec- 
tric couples connected 
in a continuous se- 
ries, as shown partly 
in Fig. 434, are insu- 
lated from one another, 
except at their junc- 
tions, and packed in a 
metallic box, supported 
as shown in Fig 433. 

The free terminals of Fig. 433. Thermo-Electric 
the series are con- Pile- 

nected to binding posts. Differences of tem- 
perature between the two faces of the pile, where 
the junctions are exposed, result in a difference 
of potential equal to the sum of the differences of 
potential of all the thermo-electric couples. 




a-f 



A careful inspec- 
tion will show that 
the junctions are 
formed successively 
at opposite faces of 
the pile, so that if 
the junctions be 
numbered succes- 
sively, the even junc- 
tions will come at Fig. 434» Series- Connected 
one face, and the Thermo-Electric Couples, 
odd junctions at the other. This is necessary 
in order to permit all the thermo-electric couples 
to add their differences of potential ; for, if, as 
in Fig. 435, a thermo-electric chain be formed, 





Fig. 435. Thermo-Electric Circuit. 



no currents will result from equally heating any 
two consecutive junctions J, J, of the metals A 
and B, since the electromotive forces so produced 
oppose each other. 

Thermopiles have been constructed by 
Clamond, of couples of iron and an alloy of zinc 
and antimony, of sufficient power to produce a 
voltaic arc whose illuminating power equaled 40 



PH.] 



405 



[Pla. 



carcel burners. Many practical difficulties exist 
which will have to be surmounted, however, before 
such piles can be employed as commercial electric 
sources. 



Pill, Insulator 



-A bolt by means 



Pile, Toltaic 



-A battery consisting 



of a number of voltaic couples connected so 
as to form a single electric source. 

A form similar to Volta's original pile, consist- 
ing of alternate discs of copper and zinc, separated 
from each other by discs of wet cloth, and piled 
on one another, so as to form a number of separate 
voltaic couples connected in series, is shown in 
Fig. 436. The thick plates marked Zn, are of 
zinc ; the copper plates, marked Cu, are much 




Fig. 436. Voltaic Pile. 

thinner. The discs of moistened cloth are shown 
at d d. One end of such a pile would then be 
terminated by a plate of copper, and the other 
by a plate of zinc. The copper end forms the 
positive electrode, and the zinc end the negative 
electrode. (See Cell, Voltaic ) 

Pilot Lamp. — (See Lamp, Pilot.) 

Pilot Transformer. — (See Transformer, 

Pilot.) 

Pilot Wires.— (See Wires, Pilot) 




Fig' 437- Insulator 
Pin. 



of which an insulator is attached to the tele- 
graphic support or arm. 

The insulator pins or bolts are generally fixed to< 
the insulator by means of 
screw threads turned on 
their ends. They are then 
cemented to the insulators by 
any suitable moisture-proof 
cement. 

The pin and insulator con- 
nected to one another by 
means of a screw thread are 
shown in Fig. 437. 

Pin, Switch A 

metallic pin or plug pro- 
vided for insertion in a 
telegraphic switch board. 
A form of switch pin is 
shown in Fig. 438. The 
metallic end is conical in 
form, and is provided with 
two longitudinal slots at 
right angles to each other in 
order to insure a light spring connection with 
the metallic contact plate in which the pin is in- 
serted. 

Pith. — A light, cellular material, forming the 
central portions of most exogenous plants. 

An excellent pith, suitable for 
electrical purposes, is furnished by 
the dried interior of the elder-berry 
stick. 

Pith Ball.— (See Balls, Pith) 

Pith - Ball Electroscope. — 

(See Electroscope, Pith-Ball) 

Pivot Suspension. — (See Sus- 
pension, Pivot) 

Plain-Pendant Argand Elec- 
tric Burner. — (See Burner, 
Plain-Pendant Electric) 

Plain-Pendant Electric Burner. 

Burner, Plain-Pendant Electric) 

Plane Angle. — (See Angle, Plane) 

Plane, Proof A small insulated 

conductor employed to take test charges from 
the surfaces of insulated, charged conductors* 




Fig. 438. 

Switch Pin* 



(See 



Pla*] 



406 



[Pla. 



The proof-plane is used in connection with 
some form of electrometer. (See Balance, Cou- 
lomb'' s Torsion.) 



Plane, Proof, Magnetic 



-A small 



coil of wire placed in the circuit of a delicate 
galvanometer, and used for the purpose of 
exploring a magnetic field. 

When the coil is suddenly inverted in a mag- 
netic field, if a long-coil galvanometer provided 
with a heavy needle is used, the number of lines 
•of force which pass through the area of cross-sec- 
'tion of the coil will be proportional to the sine of 
half the angle of the first swing of the needle. 

Plant. — A word sometimes used for in- 
stallation, or for the apparatus required to 
carry on any manufacturing operation. 

An electric plant includes the steam engines 
or other prime motors, the generating dynamo or 
•dvnamos, the lamps and other electro-receptive 
devices, and the circuits connected therewith. 

Plant Electricity. — (See Electricity, 
Plant. Plants, Electricity of) 

Plants, Electricity of Electricity 

produced naturally by plants during their vig- 
orous growth. 

DuBois-Reymond and others have shown that 
plants while in a vigorous vital state are active 
sources of electricity. 

If one of the terminals of a galvanometer be 
inserted into a fruit near its stem, and the other 
terminal into the opposite part of the fruit, the 
galvanometer at once shows the presence of an 
electric current. 

Buff has shown that the roots and interior por- 
tions of plants are always negatively charged, 
while the flowers, fruits and green twigs are posi- 
tively charged. 

Plant tissue or fibre, like the muscular fibre of 
animals, exhibits in many cases a true contraction 
on the passage through it of an electric current. 
This is seen in the Mimosa sensitiva, or Sensitive 
Fern, in the Venus' Fly-Trap, and in several other 
species of plants. 

Pouillet concludes from numerous observations 
that the free positive electricity of the atmosphere 
is partly due to the vapors disengaged by grow- 
ing plants. 

The peculiar geographical distribution of thun- 
der storms, however, does not favor this assump- 



tion. (See Storm, Thunder, Geographical Dis- 
tribution of.) 

Plastics, Galvano A term some- 
times employed for electrotyping, that is 
where the deposits are sufficiently thick to 
permit of ready separation from the object 
which forms the mould. 

Literally, the cold moulding or shaping of 
metals by electrotyping. (See Plating, Elec- 
tro. Metallurgy, Electro?) 

The word galvano-plastics is sometimes used 
as synonymous with electrotyping, electro-plat- 
ing, or electro-metallurgy generally. 



Plastics, Hydro 



-The art of elec- 



trically shaping or depositing metals in the 
wet by electrotyping. (See Plastics, Gal- 
vano) 

Plate, Arrester, of Lightning* Protector 

That plate of a lightning protector 

which is directly connected with the circuit 
to be protected, as distinguished from the plate 
that is connected with the ground. (See 
Arrester, Lightning) 

Plate Condenser. — (See Condenser, Plate) 
Plate, Ground, of Lightning Arrester 

— That plate of a comb lightning arrester 
which is connected to the earth or ground. 
(See Arrester, Lightning, Cojnb.) 

Plate, Negative, of Storage Cell 

That plate of a storage cell which, by the 
action of the charging current, is converted 
into or partly covered with a coating of spongy 
lead. 

That plate of a storage battery which is 
connected with the negative terminal of the 
charging source, and which is therefore the 
negative pole of the battery on discharging. 

The usage is the reverse of that in the case of 
the primary battery. 

Plate, Negative, of Toltaic Cell 

The electro-negative element of a voltaic 
couple. (See Couple, Voltaic) 

That element of a voltaic couple which is 
negative in the electrolyte of the cell. (See 
Electrolyte) 

The negative plate of a voltaic cell is the plate 
not acted on by the electrolyte. In a zinc carbon 



Pla.] 



407 



[Pla. 



couple in dilute sulphuric acid, the carbon plate 
is the negative plate. (See Cell, Voltaic.) 

The negative plate is to be carefully distin- 
guished from the negative pole, which is the ter- 
minal connected to the positive plate. The 
terminal connected to the negative plate is the 
positive pole. (See Cell, Voltaic.) 

Plate, Positive, of Storage Battery 

— That plate of a storage battery which is 
converted into, or covered by, a layer of lead 
peroxide, by the action of the charging current. 

That plate of a storage battery which is 
connected with the positive terminal of the 
charging source and which is, therefore, the 
positive pole of the battery on discharging. 

It will be noticed that the usage in this respect 
is the reverse of that in the case of primary bat- 
teries, in which the positive plate is positive in 
the liquid only; the end which projects from the 
liquid, or the terminal connected with it being 
negative. 

In storage batteries, the positive plate is con- 
nected with the positive pole. (See Battery, 
Storage. Cell, Voltaic.) 

Plate, Positive, of Yoltaic Cell 

The electro-positive element of a voltaic 
couple. (See Couple, Voltaic) 

That element of a voltaic couple which is 
positive in the electrolyte of the cell. (See 
Electrolysis?) 

The positive plate of a voltaic cell is the plate 
out from which the current flows through the 
electrolyte. 

The zinc plate of a zinc-carbon couple is the 
positive plate. {See Cell, Voltaic.) 

The current leaves the cell, however, to flow or 
pass through the external circuit at the wire or 
terminal connected with the negative plate. (See 
Cell, Voltaic.) 

Plate, Primary, of Condenser 

That plate of a condensing transformer in 
which the inducing charge is placed in order 
to induce a charge of different potential in the 
secondary plate. 

Plate, Secondary, of Condenser 

That plate of a condensing transformer in 
which the induced charge is produced by the 
induction of a charge on the primary plate. 
Plate, Zinc, of Voltaic Cell, Amalgama- 



tion of Covering the surface of the 

zinc plate of a voltaic cell with a thin layer of 
amalgam in order to avoid local action. (See 
Action, Local, of Voltaic Cell. Zinc, A?nal- 
gamation of.) 

Plates, Arrester A term sometimes 

applied to the two plates of an ordinary comb 
lightning arrester. (See Arrester, Lightning, 
Como.) 

The plate that is connected to the line to be 
protected, is more correctly called the arrester 
plate, and that connected to the ground the ground 
plate. 

Plates of Secondary or Storage Cell, 

Forming' of Obtaining a thick coating 

of lead peroxide on the lead plates of a storage 
battery, by repeatedly sending the charging 
current through the cell alternately in opposite 
directions. 

The effect of sending a current between two 
lead plates immersed in dilute sulphuric acid, is to 
coat one of the plates with lead peroxide. On the 
sending of the current in the opposite direction, 
the other plate is coated with lead peroxide. If 
now the current is sent in the opposite direction, 
more peroxide is deposited on one of the plates, 
and the peroxide at the other plate is converted 
into spongy lead. 

At the end of charging, the battery will form 
an independent source of current. (See Cell, 
Storage. ) 

Platform, Pole A platform, capable 

of supporting several men, placed on a termi- 
nal pole provided with a cable box, for the 
purpose of affording a ready means of inspect- 
ing and arranging the conductors in the box. 

Plating" Balance. — (See Balance, Plating.) 

Plating Bath, Electro (See Bath, 

Electro-Plating) 

Plating, Copper — Electro-plating 

with copper. (See Plating, Electro. Bath, 
Copper.) 

Plating", Electro — The process of 

covering any electrically conducting surface 
with a metal by the aid of the electric 
current. 

By the aid of electro-plating, the baser metals 
are covered with silver, gold or platinum, or with 
any other metal, such as nickel or copper.* 



Flu.] 



408 



[Pla. 



The process of electro-plating is carried on as 
follows: 

The object to be plated is connected with the 
negative terminal of a battery and placed in a so- 
lution of the metal with which it is to be plated, 
opposite a plate of that metal connected to the 
positive terminal of the battery. If, for example, 
the object is to be plated with copper, it is placed 
in a solution of copper sulphate or blue vitriol, 
opposite a plate of copper. By this arrangement 
the object to be plated forms the kathode of the 
plating bath, and the plate of copper forms the 
anode. 

On the passage of the current the copper sul- 
phate (Cu S0 4 ) is decomposed, metallic copper 
being deposited in an adherent layer on the arti- 
cles attached to the kathode, and the acid radical 
(S0 4 ) appearing at the anode, where it combines 
with one of the atoms of the copper plate. Since 
for every molecule of copper sulphate decomposed 
in the electrolyte, a new moleculeof copper sulphate 
is thus formed, by the gradual solution of the copper 
anode, the strength of the solution in the bath is 
maintained as long as any of the copper plate re- 
mains at the anode, and the ordinary activity of 
the cell is not otherwise interfered with. 

When any other metals, such as gold, silver or 
nickel, for example, are to be deposited, suitable 
solutions of their salts are placed in the bath, and 
plates of the same metal hung at the anode. 

The character and coherence of the metallic 
coatings thus obtained depend on the nature and 
strength of the plating bath, and on the density 
of the current employed. The size and position 
of the anode, as compared with the size and posi- 
tion of the objects to be plated, must therefore be 
carefully attended to, as well as the strength of 




Fig, 43 q. Electro-Plating 

the metallic solution and the current strength 
passing. (See Current Density .) 

Fig. 439, shows a bath arranged for silver- 
plating. 

The anode consists of a plate of silver. The 



spoons, forks, etc., to be plated are immersed in 
a suitable silver solution and connected with the 
kathode. 

The electro-plating process when employed for 
the production of electrotype plates is called 
electrotyping. Here the object is to obtain a re- 
production in metal of any particular form, such 
as of type or of some natural object. It was 
called by Jacobi the galvanoplastic process. The 
term electrotyping is, however, more generally 
adopted. (See Electrotyping, or the Electrotype 
Process.) 

Plating, Gold Electro-plating with 

gold. (See Plating, Electro. Bath, Gold.) 

Plating", Nickel Electro - plating 

with nickel. (See Plating, Electro. Bath, 
Nickel.) 

Plating, Sectional Plating an article 

with a greater thickness of metal at certain 
points than at the rest of the surface. 

Sectional plating is employed for such objects 
as spoons, etc., which are, by this method, given 
a greater thickness of deposit at the under portions 
of the bowl and handle, where the spoon usually 
rests, and is, therefore, exposed to the greatest 
wear. 

Sectional plating is effected by means of sec- 
tional plating frames. (See Plating, Electro. 
Frames, Sectional Plating. ) 

Plating, Silver — Electro-plating 

with silver. (See Plating, Electro. Bath, 
.Silver?) 

Platinoid. — An alloy consisting of German 
silver containing i or 2 per cent, of metallic 
tungsten. 

Platinoid is suitable for use in resistance coils on 
account of the comparatively small influence pro- 
duced on its electric resistance by changes of 
temperature. 

Its resistance is 6o per cent, higher than that 
of German silver. 

Platinum. — A refractory and not readily 
oxidizable metal, of a tin-white color. 

The co-efficient of expansion of platinum by 
heat is very nearly that of ordinary glass. Pla- 
tinum is, therefore, generally employed for the 
leading-in conductors of an incandescent lamp. 
These conductors are fused into the glass of the 
lamp chamber. On the heating of the wires by 



Pla.] 



409 



[Plu. 



the current, the glass expands equally with the 
wires, and the vacuum in the lamp chamber is 
not, therefore, injured. 

Platinum Alloy.— (See Alloy, Platinum- 
Silver) 

Platinum Black. — Finely divided platinum 
that possesses, in a marked degree, the power 
of absorbing or occluding gases. 

Platinum black is obtained by the action of 
potassium hydrate on platinum chloride. Unlike 
metallic platinum it is of a black color. 

Platinum Fuse. — (See Fuse, Plati?ium) 

Platinum-Silver Alloy. — (See Alloy, Plat- 
inum-Silver^) 

Platinum Standard Light— (See Light, 
Platinwn Standard.) 

Platymeter. — An instrument invented by 
Sir William Thomson for comparing the 
capacities of two condensers. 

Plow. — The sliding contacts connected to 
the motor of an electric street car, and placed 
within the slotted underground conduit, and 
provided for the purpose of taking off the 
current from the electric mains placed therein, 
as the contacts are pushed forward over them 
by the motion of the car. 

Similar contacts, placed in the rear of the motor 
car and drawn after the train, form what is techni- 
cally known as the sled, or when rolling on over- 
head wires as trolleys. (See Railroad, Electric.) 

Plow, Electric A plow driven by 

an electric motor placed either on a wagon to 
which the plow is attached, or by a stationary 
electro-motor, by the aid of cords or other 
flexible belts. 

One of the first practical applications of the elec- 
tric transmission of energy was for the operation 
of a plow, driven electrically, by an electric current 
generated at some distance, and transmitted to 
the electric motor by suitable conductors. 

Pliicker Tube.— (See Tube, Pliicker.) 

Plug. — A piece of metal in the shape of a 
plug, provided for making or breaking a cir- 
cuit by placing in, or removing from, a con- 
ical opening formed in the ends of two 
closely approached pieces of metal which are 



connected with the circuits to be made or 
broken. 

As the plug is inserted in the opening it bridges 
over the opening and thus closes the circuit con- 
nected with the separate pieces of metals. On 
removing the plug the circuit is opened or broken. 

Plug. — In telegraphy, an inexpert operator. 

Plug, Double A plug so constructed 

that when inserted in a spring-jack it makes 
two connections, one at its point and one at 
its shank. (See Spring-Jack.) 

Plug, Fusible A term sometimes 

applied to a safety fuse. (See Plug, Safety.) 

Plug, Infinity • — A plug hole in a box 

of resistance coils, in which the two pieces of 
brass it connects are not connected by any 
resistance coil, and which, therefore, leaves, 
when withdrawn, an open circuit of an in- 
finite resistance. 



Plug, Safety 



-A wire, bar, plate or 



strip of readily fusible metal, capable of con- 
ducting, without fusing, the current ordinarily 
employed on the circuit, but which fuses, and 
thus breaks the circuit, on the passage of an 
abnormal current. (See Fuse, Safety.) 

A safety plug is only used on circuits in which 
the electro-receptive devices are connected with 
the leads in multiple. In this case the fusing of 
the safety plug, and the consequent opening of the 
circuit with which it is connected, does not affect 
the rest of the circuit. On series-connected circuits 
a different form of safety device is used. (See 
Cut -Out, Automatic, for Series -Connected Elec- 
tro-Receptive Devices. ) 

Plug, Short-Circuiting A plug by 

means of which one part of a circuit is cut 
out by being short-circuited. 

Plug Switch.— (See Switch, Plug) 

Plug, Wall A plug provided for 

the insertion of a lamp or other electro-re- 
ceptive device in a wall socket, and thus con- 
necting it with a lead. 

Plugging. — Completing a circuit by means 
of plugs. 

Plugs, Grid Plugs of active ma- 
terial that fill the spaces or apertures in the 
lead grid or plate of a storage battery. 



Plu.] 



410 



[Poi. 



The active material forming the plugs is placed 
in the spaces in the grid while in the plastic con- 
dition. On the subsequent hardening of this ma- 
terial, these grid plugs cannot readily fall out, 
since the spaces are so shaped that their interior 
portions are of greater diameter than at the sur- 
face of the plates. 

Plumbago. — An allotropic modification of 
carbon. 

Plumbago, the material commonly known as 
black lead, is the same as graphite. Powdered 
plumbago is employed in electrotyping processes 
for rendering non-conducting surfaces electrically 
conducting. For this purpose powdered plum- 
bago is dusted on the surfaces, which thus acquire 
the power of receiving a metallic lustre by fric- 
tion. Stove polishes are formed of mixtures of 
plumbago and other cheap materials. (See 
Graphite. - ) 

Strictly speaking, the term graphite is properly 
applied to such varieties of plumbago as are suit- 
able for direct use for writing purposes, as in lead 
pencils. 

Plumbago, Coppered Powdered 

plumbago coated with copper, for use in the 
metallization of objects to be electro-plated. 
(See Metallization?) 

Plumbago, Gilt Powdered plum- 
bago whose conducting power for electricity 
has been increased by coating it with metallic 
gold. 

Gilt plumbago is used for rendering non-con- 
ducting surfaces electrically conducting and thus 
preparing them for electro-plating. 

To prepare gilt plumbago, dissolve in ioo parts 
of sulphuric ether I part of chloride of gold, mix 
in this 60 parts of powdered plumbago, and ex- 
pose to air and light until all ether has volatilized. 
Then dry in an oven. 

Plumbago, Silyered Powdered 

plumbago coated with metallic silver for use. 
in the metallization of objects to be electro- 
plated. 

Plunge Battery. — (See Battery, Plunge?) 

Pneumatic Perforator. — (See Perforator, 
Pneumatic?) 

Pneumatic Signals, Electro (See 

Signals, Electro-Pneumatic?) 

Pockets, Armature Spaces pro- 
vided in an armature for the reception of the 



armature coils. (See Coils, Armature, of 
Dynamo-Electric Machine?) 

Poggendorff's Voltaic Cell.— (See Cell,. 
Voltaic, Poggendorff's?) 

Point, Carbon A term formerly 

applied to the carbon electrodes used in the 
production of the voltaic arc. 

Point, Indifferent A point in the 

intra-polar regions of a nerve where the ane- 
lectrotonic and kathelectrotonic regions meet, 
and where the excitability is therefore un- 
changed. 

This is sometimes called the neutral point. 

Point of Lightning Rod. — (See Rod, 
Lightning, Points on.) 

Point of Origin. — (See Origin, Poznl of.) 

Point, Neutral In electro-thera- 
peutics, a term sometimes used instead of in- 
different point. (See Point, Indifferent?) 

Point, Nodal The null point in a 

circuit traversed by electric oscillations. (See 
Point, Null) 

Point, Null Such a point on a 

micrometer circuit, that when joined or con- 
nected with the second- 
ary circuit of an in- 
duction coil, the sparks 
in the micrometer cir- 
cuit are either very 
greatly decreased or 
are entirely absent. 

The null point on the 
micrometer circuit is situ- 
ated symmetrically with 
respect to the micrometer 
knobs. 

If the induction coil A, 
Fig. 440, has its second- 
ary circuit connected as 
shown with the microm- Fig. 440. Null Point. 
eter circuit at the point e, situated at the centre 
of the micrometer circuit, the point will be a null 
point, and the effects of sparks at the micrometer 
knobs, at M, will be greatly decreased. Under 
the conditions shown in the figure, the electrical 
oscillations in the micrometer circuit must be re- 
garded as in the condition of stationary waves or 
vibrations. It would seem, therefore, that defi- 
nite waves or vibrations are set up in the microm- 




Poi.] 



411 



Pol. 



eter circuit, in the same way as are the vibra- 
tions produced in an elastic bar set in vibration 
by a violin bow, or by a blow from a hammer. 

Points, Consequent The points or 

places in an anomalous magnet where the 
consequent poles are situated. (See Magnet, 
Anomalous. Pole, Anomalous?) 

Points, Corresponding- — Points 

where the lines of electrostatic force sur- 
rounding- an insulated charged conductor 
enter the surfaces of neighboring conductors. 

Points on the surface of a body placed in 
an electrostatic field where the lines of elec- 
trostatic force enter its surface, and thus pro- 
duce a charge equal and opposite to that 
of the surface of the body at the points from 
which they came. 

Corresponding points receive, in accordance 
with the laws of electrostatic induction, charges 
equal and opposite to those of the surfaces from 
which the lines of electrostatic force originate. 

—The 



Points, Electric Action of — 

effect of points placed on an insulated, 
charged conductor, in slowly discharging the 
conductor by electric convection. (See Con- 
vection, Electric) 

The cause of this action of points is to be at- 
tributed to the increased density of a charge on 
the surface of a conductor at the points and the 
consequent production of convection streams of 
air, which thus gradually carry off the charge. 
(See Charge, Distribution of.) 

Points, Iso-Electric A term some- 
times used in electro-therapeutics for points 
of equal potential. 

Points, Neutral, of Dynamo-Electric Ma- 
chine Two points of greatest differ- 
ence of potential, situated on the commutator 
cylinder, at the opposite ends of a diameter 
thereof, at which the collecting brushes must 
rest in order to carry off the current quietly. 

These are called the neutral points because the 
coils that are short-circuited by the brushes lie in 
the magnetically neutral points of the armature. 
(See Line, Neutral, of Commutator Cylinder.) 

— Points 



Points, Neutral, of Mag-net — 

approximately midway between the poles of 



a magnet. (See Line, Neutral, of a Magnet. 
Magnet, Equator of) 

Points, Neutral, of Thermo-Electric Dia- 
gram ■ — The points on a thermo-electric 

diagram where the lines representing the 
thermo-electric powers of any two metals 
cross one another. 

A mean temperature for any two metals in 
a thermo-electric series, at which, if their two. 
junctions are slightly over and slightly under 
the mean temperature (the one as much 
above as the other is below), no effective 
electromotive force is developed. (See Dia- 
gram, Thermo-Electric \ Couple, Thermo- 
Electric) 

Points or Rhumbs of Compass.— (See 
Compass, Points of) 

Polar Region. — (See Region, Polar) 

Polar Tips.— (See Tips, Polar) 

Polarity, Diamagnetic A polar- 
ity the reverse of ordinary magnetic polarity, 
the existence of which was assumed by Fara- 
day to explain the phenomena of diamag- 
netism. (See Diamagnetis?n) 

Faraday assumed that diamagnetic substances, 
when brought into a magnetic field, acquired 
north magnetis?n in those parts that were nearest 
the north pole, instead of south magnetism, as. 
with ordinary magnetic substances. The north 
pole thus obtained would, he thought, explain, 
the apparent repulsion of a slender rod of any di- 
amagnetic material delicately suspended in a. 
strong magnetic field, and cause it to point equa- 
torially, or with the lines of force passing through 
its least dimensions. This supposition was subse- 
quently abandoned by Faraday. It has recently- 
been revived by Tyndall. (See Diaviagnetism.\ 

The action of a diamagnetic body, when placed 
in a magnetic field, is now generally ascribed \.o- 
the fact that the atmosphere, by which such body- 
is surrounded, is more powerfully paramagnetic, 
than the diamagnetic substance. The diamag- 
netic substance comes to rest in an equatorial posi- 
tion, because in that position there is the greatest 
length of air in the path of the magnetic lines, 
which has a smaller magnetic resistance than the 
diamagnetic substance. 

Polarity, 3Iagnetic The polarity 

acquired by a magnetizable substance when 
brought into a magnetic field. 



Pol.] 



412 



[Pol. 



The direction of magnetic polarity, acquired by 
a substance when brought into a magnetic field, 
depends on the direction in which the lines of 
magnetic force pass through it. Where these 
lines enter the substance a souh pole is pro- 
duced, and where they pass out, a north pole is 
produced. The axis of magnetization lies in the 
direction of the lines of force as they pass 
through the body, and the intensity of magnetiza- 
tion depends on the number of these lines of 
force which pass through the body. 

The cause 0/" magnetic polarity is not definitely 
known. Hughes' hypothesis attributes it to a 
property inherent in all matter. Ampere at- 
tributes it to closed electric circuits in the ultimate 
particles. Whatever its cause, it is invariably 
manifested by a magnetic field, the lines of force of 
which are assumed to have the direction already 
mentioned. (See Magnetism, Hughes' Theory 
of. Magnetism, Ainpere' 's Theory of Magnet- 
ism, Ewing's Theory of.) 

Polarization, Galvanic A term 

sometimes applied to the polarization of a 
voltaic cell. (See Cell, Voltaic, Polariza- 
tion of.) 

Polarization, Internal, of Moist Bodies 

A polarization exhibited by such 

moist bodies as the nerves, muscular fibres, 
the juicy parts of vegetables and animals, or 
in general by all bodies possessing a firm struc- 
ture filled with a liquid, on the passage 
through them of a strong electric current. 

Polarization, Magnetic Rotary 

The rotation of the plane of polarization of a 
beam of plane-polarized light consequent on 
its passage through a plate of glass subjected 
to the stress of a magnetic field. (See Rota- 
tion, Magneto-Optic) 

Polarization of Dielectric. — (See Dielec- 
tric, Polarization of.) 

Polarization of Electrolyte. — (See Elec- 
trolyte, Polarization of) 

Polarization of Yoltaic Cell. — (See Cell, 
Voltaic, Polarization of) 

Polarized Armature. — (See Armature, 
Polarized) 

Polarized Relay. — (See Relay, Polarized) 

Polarizing" Current. — (See Current, 
Polarization.) 



Polarizing Electro-Therapeutic Current. 

— (See Current, Electro- Therapeutic Polar- 
izing) 

Pole, Analogous That pole of a 

pyro-electric substance, like tourmaline, which 
acquires a positive electrification while the 
temperature of the crystal is rising. (See 
Electricity, Pyro) 

Pole, Anomalous A name some- 
times given to those parts or poles in an 
anomalous magnet which consist of two simi- 
lar free poles placed together. (See Magnet, 
Anomalous) 

Pole, Antilogous That pole of a 

pyro-electric substance, like tourmaline, which 
acquires a negative electrification when the 
temperature of the crystal is rising, and a 
positive electrification when it is falling. (See 
Electricity, Pyro) 

Pole, Armature (See Armature, 

Pole) 

Pole Changer. — A switch or key for chang- 
ing or reversing the direction of current pro- 
duced by any electric source, such as a bat- 
tery, 

The commutator of a Ruhmkorff coil is a sim- 
ple form of pole changer. It is, however, usu- 
ally called a commutator. (See Coil, Induction. ) 

Pole-Changing and Interrupting Elec- 
trode Handle. — (See Electrode-Handle, 
Pole-Changing and Interrupting) 

Pole-Changing Switch. — (See Switch, 
Pole-Changing) 

Pole Climbers. — (See Climbers, Pole) 

Pole, Consequent A magnet pole 

formed by two free north or two free south 
poles placed together. (See Magnet, Ano?n- 
alous.) 

Pole, Magnetic, Austral A name 

formerly employed in France for the north- 
seeking pole of a magnet. 

That pole of a magnet which points to the 
earth's geographical north. 

It will be observed that the French regarded the 
magnetism of the earth's Northern Hemisphere 



Pol.] 



413 



[Pol. 



as north, and so named the north-seeking pole of 
the needle the austral or s outh pole. 

The north-seeking pole of the magnet is some- 
times called the boreal or north pole. (See Pole, 
Magnetic, Boreal.) 



Pole, Magnetic, Boreal 



-A name 



formerly employed in France for the south- 
seeking pole of a magnet, as distinguished 
from the austral or north-seeking pole. 

That pole of a magnet which points to- 
ward the geographical south. 

If the earth's magnetic pole in the Northern 
Hemisphere be of north magnetism, then the pole 
of a needle that points to it must be of the oppo- 
site polarity, or of south magnetism. In this 
country we call the end which points to the north, 
the north-seeking pole or marked pole. In 
France the end which points to the north was 
formerly called the austral pole. Austral means 
south pole. (See Pole, Magnetic, Austral.) 

Pole, Magnetic, False A term pro- 
posed by Mascart and Joubert to designate 
the place or places on the earth which appar- 
ently act as magnetic poles, in addition to 
the two true magnetic poles, near the earth's 
geographical poles. 

According to these authorities, the earth pos- 
sesses two magnetic poles only, viz., a negative 
pole in the Northern Hemisphere and a positive 
pole in the Southern Hemisphere. The addi- 
tional poles are called by them the false magnetic 
poles. 

Pole, Magnetic, Free A pole in a 

piece of iron, or other paramagnetic sub- 
stance, which acts as if it existed as one mag- 
netic pole only. 

A free magnetic pole has in reality no physical 
existence. The conception, however, is of use in 
describing certain magnetic phenomena. If the 
bar of iron be so long as to practically place one 
pole beyond the sensible action of the other, either 
pole may be regarded as a free pole. 

Pole, Magnetic, Marked That pole 

of a magnetic needle which points approxi- 
mately to the earth's geographical north. 
(Obsolete.) 

The north-seeking pole of a magnetic needle. 

Pole, Magnetic, North That pole 

of a magnetic needle which points approxi- 
mately to the earth's geographical north. 



The north-seeking pole of a magnetic 
needle. 
Pole, Magnetic, North-Seeking 

That pole of a magnetic needle which points 
approximately towards the earth's geographi- 
cal north. 

Pole, Magnetic, Salient A term 

sometimes applied to the single poles at the ex- 
tremities of an anomalous magnet, in order to 
distinguish them from the double or consequent 
pole formed by the juxtaposition of two simi- 
lar magnetic poles. (See Magnet, Anoma- 
lous?) 

Pole, Magnetic, South That pole 

of a magnetic needle which points approxi- 
mately towards the earth's geographical south. 

The south-seeking pole of a magnetic 
needle. 

Pole, Magnetic, South-Seeking 

That pole of a magnetic needle which points 
approximately toward the geographical south. 

Pole, Negative That pole of an 

electric source through which the current is 
assumed to enter or flow back into the source 
after having passed through the circuit ex- 
ternal to the source. 

Pole-Pieces of Dynamo-Electric Machine. 

— (See Pieces, Pole, of Dynamo-Electric 
Machine?) 

Pole Platform.— (See Platform, Pole?) 

Pole, Positive That pole of an 

electric source out of which the electric cur- 
rent is assumed to flow. 

Pole Steps. — Short rods or bars shaped so 
as to be readily inserted in holes near the 
base of telegraph or electric light poles, so as 
to serve as steps to enable a lineman to reach 
the permanently placed steps. 

Permanent steps are placed only at some dis- 
tance from the ground, in order to prevent the 
ready climbing of the poles by unauthorized 
persons. 

Pole, Telegraphic A wooden or iron 

upright on which telegraphic or other wires 
are hung. 

Wooden poles are generally round. 



Pol.] 



414 



[Pol, 



The terminal pole, or the last pole at each end 
of the line, or where the wires bend at an angle 
of nearly 90 degrees, is made larger than usual 
and is often cut square. 

The holes for the poles must be dug in the true 
line of the wires, and not at an angle to such line. 
As little ground should be disturbed in the dig- 
ging as possible. Earth borers, or modifications 
of the ordinary ship auger, are generally em- 
ployed for this purpose. When the pole is placed 
in position the ground should be rammed or 
punned around the pole. 

In setting the pole, it is generally buried at least 
5 feet in the ground. In England the poles are 
planted to a depth of about one-fifth of their 
length. In embankments and loose ground, they 
are planted deeper than in more solid earth. On 
curves, the poles should be inclined a little so as 
to lean back against the lateral strain of the wire, 
since by the time the ground has completely set, 
the strain of the wire will have pulled them into 
an erect position. 

Care must be taken to so plant the poles on 
that side of a road or railway that the prevailing 
winds will blow them off the roadbed, should it 
overturn them. As to location, the top of steep 
cuttings is preferable to the slope. In all exposed 
positions, it is preferable to strengthen the poles 
by stays attached to both sides. 

Where the number of wires is unusually large, 
heavy timber, or in case of its absence, double 





Fig. 44 t. Telegraphic 
Brackets. 



Fig. 442. Telegraphic 
Arms. 



poles suitably braced together, must be employed. 
In long lines the poles should all be numbered in 
order to afford ease of reference in case of repair. 

When, even with the best punning, and other 
precautions, the pole is judged to be unable to 
resist the strain on it, stays and struts are em- 
ployed. A stay is used when it is desired to re- 
move the pull or tension from the pole ; a strut, 
when it is desired to remove the thrust ox pressure. 

The arms or brackets, or the cross-pieces that 



support the insulators, should all be placed on 
the same side of the poles. Some common forms 
of brackets are shown in Fig. 441, and of tele- 
graphic arms in Fig. 442. 

Saddle brackets should be placed on alternate 
sides of the poles. When the strain on an insula- 
tor is too great, on account of the wire going off 
at a sharp angle, a shackle is used. This is a 
special form of insulator which confines the strain 
to one spot. 



_£■& 




Fig. 443. Double Shackles. 

A form of double shackle is shown in Fig- 
443. The wire passes around the recess at B> 
between the two insulators. 

On curves, or in any situation where there is a 
probability, in case of the breaking of an insula- 




Fig. 444. Hook Guard. 

tor, of a wire getting into a dangerous position r 
guards should be employed. 

Guards are of two kinds, viz.: hoop guards 
and hook guards. A form of hook guard is 
shown in Fig. 444. 

When wooden poles are employed various pre- 
servative methods are adopted to protect the 
wood from decay, which is very apt to occur, 
especially where the pole enters the ground. 
Some of these forms are as follows, viz. : 

(1.) Charring and tarring the butt end of the 
pole where it enters the ground, so as to expel 
the sap and destroy injurious plant or animal 
germs. 



Pol. 



415 



[Por. 



The charred end is then cleansed and dipped 
in a mixture of tar and slaked lime. 

(2.) Burnetizing, or the introduction of 
•chloride of zinc into the pores of the wood, by 
placing the poles in an open tank filled with a 
solution of this salt. 

(3.) Kyanizing, or the similar introduction of 
corrosive sublimate, or mercuric chloride. 

(4.) Boucherizing, or the injection of a solution 
of copper sulphate into the pores of the wood. 

(5.) Creosoting, or the application of creosote 
to well seasoned poles. 

Pole, Telegraphic, Punning of 

Ramming or packing the earth around the 
base of a telegraph pole for the purpose of 
more securely fixing it in the ground. 

Pole, Telegraphic, Terminal The 

pole at either end of a telegraphic line. 

As the first or last pole in a telegraphic line is 
not supported on opposite sides by the line wires, 
it is generally made stouter than the intermediate 
poles, and greater care is taken to fix it securely 
in the ground. 

Pole, Testing A term sometimes 

employed in electro-therapeutics for the in- 
different pole or electrode. (See Electrode, 
Indifferent?) 

Pole, Trolley The pole which sup- 
ports the trolley bearing and rests on the 
socket in the trolley base frame in an over- 
head wire electric railway system. 

Pole, Unit, Magnetic A magnetic 

pole of such a strength that it would act with 
a unit or dyne of force on another unit pole at 
a distance of one centimetre. 

Poles, Consequent The name given 

to single magnetic poles formed by two free 
N. poles or two free S. poles placed together. 
(See Magnet, Anomalous?) 

Poles, Idle Poles or electrodes in 

Crookes' tubes, between which discharges are 
not taking place. 

The idle poles have no connection with the in- 
duction coils or other sources from which the elec- 
tric discharges are obtained. These poles are pro- 
vided for attaching galvanometer wires, etc., in the 
study of the Edison effect, or for the study of the 



electrical condition of the dark space and other 
regions of the atmosphere of the tube. 

Poles, Magnetic The two points 

where the lines of magnetic force pass from 
the iron into the air, and from the air into 
the iron. 

The two points in a magnet where the 
magnetic force appears to be concentrated. 

In reality the magnetic force is most concen- 
trated at the neutral points of a m agnet, through 
which all the lines of force pass. 

All magnets possess at least two poles, one 
positive or north, and the other negative or south. 

The lines of magnetic force are assumed to 
come out of a magnet at its north pole, and to 
enter it at its south pole. 

Poles, Magnetic, of Yertieity (See 

Verticity, Poles of, Magnetic?) 

Poles of Condenser. — The terminals of a 
condenser. (See Condenser.) 

Poles of Magnetic Intensity. — (See In- 
tensity, Magnetic, Pole of.) 

Polyphase Current. — (See Current, 
Multi-Phase?) 

Polyphotal Arc Light Regulators. — (See 
Regulator, Polyphotal Arc-Light?) 

Popgun, Electro-Magnetic A mag- 
netizing coil, provided with a tubular space 
for the insertion of a core, much shorter than 
the length of the coil, which, when the ener- 
gizing current is passed through the coil, 
is thrown violently out from the coil. 

The movement and consequent expulsion of the 
core is due to the action of the lines of magnetic 
force which complete their circuit through the 
core. 

Porcelain. — A variety of insulating ma- 
terial. 

A translucent variety of earthenware. 
Porous Cell. — (See Cell, Porous?) 
Porous Cup. — (See Cup, Porous?) 
Porous Insulation. — (See Insulation, 
Porous?) 

Porous Jar.— (See /^r, Porous?) 
Porret's Phenomena. — (See Phenomena, 
Porret.) 



Por.] 



416 



tpos. 



Portative Power. — (See Power, Porta- 
tive^) 

Portelectric. — An electric carrier. 

A system of electric transportation by 
means of the successive attractions of a num- 
ber of hollow helices of insulated wire on a 
hollow solenoidal iron car. 

The solenoidal car forms the movable core of the 
helical coils. As it moves through these coils it 
automatically closes the circuit of an electric cur- 
rent through the coils in advance of it and opens 
the circuit of the coils in its rear. In this way the 
solenoidal car advances in a line coincident with 
the axis of the helical coils, being virtually sucked 
through them by their magnetic attractions. This 
system of electric propulsion is unique in systems 
of electric traction. The motor becomes a mere 
mass of iron or other paramagnetic material. 
The system is suitable for the carriage of mail or 
other comparatively light articles at a high speed. 

In an experimental plant at Dorchester, Mass., 
a track of 2,784 feet in length was laid in the ap- 
proximate form of an oval. The track was 
formed by an upper and lower rail of steel, suit- 
ably supported by stringers. 

The car, which forms the movable core of the 
solenoidal coils, was of wrought iron, and was 
cylindrical in shape, with conical ends. It was 



placed on the top of the carrier and connected the 
several helices successively with the electric 




Fig. 4*5. Portelectric Track. 

12 feet in length and 10 inches in diameter, and 
weighed about 500 pounds. It would carry about 
10,000 letters. It had two flanged wheels above 
and two below. 

The solenoidal coils, by the attractive power of 
which the core was moved, embraced the track 
and the movable core or carrier. They were 
fixed along the track at intervals of 6 feet from 
centre to centre. Each coil was formed of 630 
turns of No. 14 copper wire. The upper track 
rail is divided into sections which form conductors 
for the driving current. A central wheel was 




Fig. 446. Portelectric Car. 

source as the carrier was drawn forward. A. 
speed of about 34 miles an hour was reached. 

A section of the track is shown in Fig. 445, and 
the shape and general structure of the carrier in 
Fig. 446. 

Portrait, Electric A portrait 

formed on paper by the electric volatilization 
of gold or other metal. 

An electric portrait is obtained by cutting on 
a thin card a portrait in the form of a stencil. A 
sheet of gold leaf is then placed on one side of the 




Fig. 447. Electric Portrait. 

paper stencil, and a sheet of paper on the other 
side ; sheets of tin-foil are then placed on the out- 
side, as shown in Fig. 447, and the whole firmly 
pressed together. If, now, a disruptive discharge 
is passed through from one sheet of tin-foil to the 
other, the gold leaf is volatilized, and a purplish 
stain is left on the paper of the outlines of the 
stenciled card, thus forming an electric portrait. 

Position, Energy of A term used 

for stored energy, or potential energy. (See 
Energy, Potential?) 

Positive Direction of a Simple-Harmonic 
Motion. — (See Motion, Simple-Harmonic, 
Positive Direction of.) 



Pos.] 



417 



[Pot. 



Positive Direction of Lines of Magnetic 
Force. — (See Force, yiagnetic, Lines of, 
Positive Direction of.) 

Positive Direction of the Electrical Con- 
vection of Heat.— (See Direction, Positive, 
of Electrical Co7ivection of Heat.) 

Positive Direction Round a Circuit. 
— (See Direction, Positive, Round a Cir- 
cuit^) 

Positive Direction Through a Circuit. 
— (See Direction, Positive, Through a Cir- 
cuity 

Positive Electricity. — (See Electricity, 
Positive?) 

Positive Electrode. — (See Electrode, 
Positive?) 

Positive Feeders. — (See Feeders, Posi- 
tive.) 

Positive-Oinnihus Bars. — (See Bars, Posi- 
tive Omnibus?) 

Positive Phase of Electrotonus. — (See 
Electroto7ius, Positive Phase of.) 

Positive Plate of Storage Battery. — (See 
Plate, Positive, of Storage Battery.) 

Positive Plate of Voltaic Cell.— (See 
Plate, Positive, of Voltaic Cell?) 

Positive Pole. — (See Pole, Positive?) 

Positive Potential. — (See Potential, Posi- 
tive?) 

Positive Side of Circuit.— (See Circuit, 
Positive Side of.) 

Positively.— In a positive manner. 

Positively Excited. — Excited or charged 
with positive electricity. (See Electricity, 
Positive.) 

Post, Binding A device for con- 
necting the terminal of an electric source 
with the terminal of an electro-receptive de- 
vice, or for connecting different parts of an 
electric apparatus with one another. 

The conducting or circuit wire is either intro- 
duced in the opening a, or c', Fig. 448, and 
clamped by the screw b, or b', or is placed in 
the space d, d, and kept in place by means of a 
thumbscrew. Sometimes two openings are 
provided at c, and c', for the purpose of connect- 
ing two wires together. 



A device for coupling or connecting the ends 
of two wires to each other. It is then called a 
coupler. (See Couple, Voltaic.) 

_ V 




Fig. 448. Binding- Posts. 

Pot, Porous The porous jar or cell 

of a voltaic cell. (See Cell, Porous?) 

Potential, Alternating A poten- 
tial, the sign or direction of which is alter- 
nately changing from positive to negative. 

An alternating potential may be obtained either 
in the case of an electrostatic field, or in that 
of a magnetic field. 

Potential, Alternating Electrostatic 

■ — The potential of a charge that is under- 
going rapid alternations. 
Potential, Alternating, Magnetic 

The difference of magnetic potential pro- 
duced by alternating electric currents. 

Potential, Constant A potential 

which remains constant under all conditions. 

A machine or other electric source is said to 
have a constant potential when it is capable, 
while in operation, of maintaining a constant 
difference of electric pressure between its two 
terminals on changes of load. (See Circuit, 
Constant-Potential. ) 

Potential, Diiference of A term 

employed to denote that portion of the 
electromotive force which exists between 
any two points in a circuit. 

The difference of potential at the poles of any 
electric source, such as a battery or dynamo, is 
that portion of the total electromotive force 
which is available, and is equal to the total 
electromotive force, less what is lost in the 
source. 

Some difference of opinion exists as to the exact 
meaning that is attached to the phrase difference 
of potential. 

A positively electrified body is said to have a 
higher electric potential than the earth, whose 
potenUai is taken as zero. 



Pot. 



418 



rpot 



Potential, Difference of, Methods of 
Measuring" Methods employed for de- 
termining differences of potential. 

These methods are as follows: 

(i.) By the Method of Weighing, that is, by 
obtaining the weight required to overcome the 
attraction between two oppositely charged plates, 
or oppositely energized coils; or by measuring 
the repulsion between similarly charged surfaces, 
or similarly energized coils. 

(2.) By the Use of Electrometers, or apparatus 
designed for measuring differences of potential. 
(See Electro?neters. ) 

(3.) By the Use of Galvanometers. 

Differences of potential, in the case of currents, 
may be determined from the quantity of electri- 
city which flows per second through a given 
circuit, that is, by the number of amperes, just 
as the pressure of water at any point in the side 
of a containing vessel can be determined by the 
quantity of water that flows per second. Differ- 
ence of potential in the case of currents, there- 
fore, may be measured by any galvanometer 
which measures the current directly in amperes, 
provided the resistance of the circuit is known. 

Potential, Drop of A term some- 
times used instead of fall of potential. (See 
Potential, Fall of) 

Potential, Electric The power of 

doing electric work. 

Electric level. 

Electric potential can be best understood by 
comparison with the case of a liquid such as 
water. 

The ability of a water supply or source to do 
work depends: 

(1.) On the quantity of water. 

(2. ) On the level of the water, as compared with 
some other level; or, in other words, on the dif- 
ference between the two levels. 

In a like manner the ability of electricity to do 
work depends: 

(I.) On the quantity of electricity. 

(2.) On the electric potential at the place where 
the electricity is produced, as compared with that 
at some other place; or, in other words, on the 
difference of potential. 

In the case of water flowing through a pipe, 
when its flow has been fully established, the quan- 
tity which passes in a given time is the same at 
any cross-section of the pipe. 



In the case of electricity, the quantity of elec- 
tricity flowing through any conductor, or part of 
a circuit, is the same at any cross section. A gal- 
vanometer introduced into a break in any part of 
the conductor would show the same strength of 
current. 

But, though the quantity of water which passes 
is the same at any cross-section of a pipe, the 
pressure per square inch is not the same, even in 
the case of a horizontal pipe of the same diameter 
throughout, but becomes less, or suffers a loss of 
head, or difference of pressure, at any two points 
along the pipe. This difference of pressure causes 
the flow of water between these two points against 
the resistance of the pipe. 

So, too, in the case of a conductor carrying an 
electric current, when the full current strength 
has been established, the quantity of electricity 
that passes is the same at all cross-sections. 



■f. '-— .. c' 
a pjfi V ' \e V\d W e pi/ \': : a" 



Fig. 44Q. Hydraulic Gradient. 

The electric pressure or potential, however, 
is by no means the same at all points in the 
conductor, but suffers a loss of electric head or 
level, in the direction in which the electricity is 
flowing. It is this electric head or level, or dif- 
ference of electric potential, that causes the elec- 
tricity to flow against the resistance of the con- 
ductor. 

These analogies can be best shown by the fol- 
lowing illustration: 

In Fig. 449, a reservoir, or source of water, at 
C, communicates with the horizontal pipe A B, 
furnished with open vertical tubes at a, b, c, d, e, 
f, g, and B. If the outlet at B, is closed, the level 
of the water in the communicating vessels is the 
same as at the source; but if the liquid escape 
freely from B, the level of the water in the branch 
pipes will be found on the inclined dotted line, or 
at a', b', c', d', e', f, g', which may be called 
the hydraulic gradient. 

The pressure per square inch, at any cross sec- 
tion of the horizontal pipe, which is measured by 
the height of the liquid in the vertical pipe at that 
point, decreases in the direction in which the liquid 
is flowing. The force that urges the -liquid 



Pot.] 



419 



rpot 



through the pipe between any two points, may 
be called the liquid-motive force {Fleming) and is 
measured by the difference of pressure between 
these points. 

In Fig. 450, the dynamo-electric machine at D, 
has its negative pole grounded, and its positive 
pole connected to a long lead, A B, the positive 
pole of which is also grounded. A fall of poten- 
tial, represented by the inclined dotted line, 
occurs between A and B, in the direction in which 
the electricity is flowing. 



*«to) 






f-«c 



rf-r^ 



g)' 



m 



Fig. 450. Fall of Electric Potential. 



The dynamo-electric machine may be regarded 
as a pump that is raising the electricity from a 
lower to a higher level, and passing it through 
the lead A B. The electric pressure or potential 
producing the flow is greatest near the dynamo and 
least at the further end, the differences at the 
points a, b, c, d, e, f, and g, being represented by 
the vertical lines a a', bb', c c', d d', e e', if. and 

gg' 

The electricity flows between any two points as 
a and b, in the conductor A B, in virtue of the 
difference of electric pressure or potential be- 
tween these two parts, or the difference between 
a a' and b b'. 

Differences of potential must be distinguished 
from differences in electric charge, or electrostatic 
density. It two conductors at different potentials 
are connected by a conductor, a current will flow 
through this conductor. When their potential is 
the same, no current flows. The density of a 
charge is the quantity of electricity per unit of 
area. 

The electric potential is the same at all points 
of an insulated charged conductor; the density is 
different at different points, except in the case of 
a sphere. The potential, however, is the same, 
since no current flows, or the charge does not re- 
distribute itself. The density on an insulated, 
isolated sphere, is uniform over all parts of the 
surface, and its potential is the same at all points. 
If now the sphere be approached to another body, 
its density will vary at different parts of its sur- 



face, and while the charge is redistributing itself 
so as to produce these differences in density the 
potential will vary. As soon, however, as this 
redistribution is effected and no further current 
exists, the potential is the same over all points, 
though the density differs at different points. 

An electric source not only produces but also 
maintains a difference of potential. In the case 
of the flow of liquid in a pipe, if a continuous 
current of the liquid be maintained from the 
higher level in the reservoir to a lower level, as, 
for example, by means of a pump, it must flow 
through the pump to the reservoir, from the lower 
level towards the higher level. In case of an 
electric source, since the thing called electricity 
flows through a closed circuit, if its direction of 
flow in that part of the circuit external to the 
source — i. e., in the external or useful current — 
be from a higher to a lower level, then its flow 
through the remainder of the circuit — i. e., 
through the source — must be from the lower to the 
higher level. Since, however, the electrical po- 
tential of a body represents the work the elec- 
tricity is capable of doing, the work done by the 
e'ectricity may be regarded as being that done 
when it passes from the higher to the lower level. 

Potential, Electrostatic — The 

power of doing work possessed by a unit 
quantity of positive electricity charged or re- 
siding on an insulated body. 

Potential, Electrostatic, Difference of 

Difference of potential of an electric 

charge. (See Potential, Difference of. 
Electrostatics?) 

Potential Energy.— (See Energy, Poten- 
tial?) 

Potential, Fall of A decrease of 

potential in the direction in which an elec- 
tric current is flowing, proportional to the re- 
sistance when the current is constant. (See 
Potential, Electric?) 

Potential Galvanometer. — (See Galva- 
nometer, Potential?) 

Potential Indicator. — (See I?idicator, 
Potential) 

Potential, Magnetic The amount 

of work required to bring up a unit north- 
seeking magnetic pole from an infinite dis- 
tance to a given point in a magnetic field. 



Pot.] 



420 



[Pow. 



Potential of Conductor, Methods of 

Varying (See Conductor, Potential 

of, Methods of Varying?) 

Potential of Conductors. — (See Conduc- 
tor, Potential of.) 

Potential, Negative That potential 

in the circuit external to the source towards 
which the electric current flows. 

Generally the lower potential, or lower 
level. 

Potential, Positive That potential 

in the circuit external to the source, from 
which the electric current flows. 

The higher potential or higher level. 

Potential, Uniform — A potential 

that does not vary. 

A constant potential. (See Potential, Con- 
stant.) 

An electric source is said to generate a uniform 
potential when it maintains a constant difference 
of potential at its terminals. 

Potential, Unit Difference of 

Such a difference of potential between two 
points that requires the expenditure of one 
erg of work to bring a unit of positive elec- 
tricity from one of these points to the other, 
against the electric force. (See Erg?) 

The practical unit of difference of potential is 
the volt. (See Volt.) 

Potential, Zero An arbitrary level 

from which electric potentials are measured. 

As we measure the heights of mountains from 
the arbitrary mean level of the sea, so we measure 
electric levels from the arbitrary level of the po- 
tential of the earth. 

Potentiometer. — An apparatus for the 
galvanometric measurement of electromotive 
forces, or differences of potential, by a zero 
method. (See Method, Null or Zero.) 

In the potentiometer the difference of potential 
to be measured is balanced or opposed by a 
known difference of potential, and the equality 
of the balance is determined by the failure of one 
or more galvanometers, placed in shunt circuits, 
to show any movement of their needles. 

The principle of operation of the potentiometer 
will be understood from an inspection of Fig. 451. 
A secondary battery S, has its terminals con- 



nected to the ends of a uniform wire A B, of high 
resistance called the potentiometer wire. There 
will, therefore, occur a regular drop or fall of po- 
tential along this wire, which, since the wire is 
uniform, will be equal per unit of length. This 
drop of potential can be shown by connecting the 
terminals of a delicate galvanometer, generally of 
high resistance, to different parts of the wire, 
when the deflection of the needle will be pi opor- 

S 




Fig. 431. Potentiometer. 

tional to the drop of potential between the two 
points of the wire touched. If, now, the terminals 
of a standard cell be inserted in the circuit o£ 
the galvanometer, so as to oppose the current 
taken from the potentiometer wire, and the con- 
tacts of the potentiometer wire be slid along the 
wire until no deflection of the galvanometer needle 
is produced, the drop of potential between these 
two points on the wire will be equal to the differ- 
ence of potential of the standard cell. (See Cell, 
Voltaic, Standard.) 

Suppose, now, it be desired to measure the dif- 
ference of potential between two points a and b, 
on the wire C, through which a current is flow- 
ing. Connect the points b and d, and a and c, 
as shown, with the delicate high resistance gal- 
vanometer G, in either of them. Now slide c, 
towards d, until the needle of G, shows no deflec- 
tion. The potential between a and b, is then 
equal to that between c and d. 

Potentiometer Wire. — (See Wire, Po- 
tentiometer?) 

Power. — Rate of doing work. 

Mechanical power is generally measured in 
horse- power, which is equal to work done at the 
rate of 550 foot-pounds per second. 

The C. G. S. unit of power is one erg per 
second. 

The practical unit of power is the watt, or 
10,000,000 ergs per second. The kilowatt is 
even more frequently used as the unit of power 
than the watt. (See Power, Unit of. ) 

Power, Absorptive The property 



Pow.] 42L [Pow. 

possessed by many solid bodies of taking in cross-section of a substance to conduct elec- 

and condensing gases within their pores. tricity, as compared with an equal length and 

Carbon possesses marked absorptive powers. area of cross-section of some other substance, 

The absorption of gases in this manner by solid such as pure silver or copper, 

bodies is known technically as the occlusion of Nq substance is known that does not offer gome 

gases. (See Gas, Occlusion of.) resistance to the passage of an electric current. 

One volume of charcoal, at ordinary tempera- The following table is taken from Sylvaiius p. 

tures and pressures, absorbs of Thompson's " Elementary Lessons in Electricity 

Ammonia 90 volumes and Magnetism' ' : 

Hydrochloric acid 85 " ~ ~ 

„,,,.., r Good Conductors. 

Sulphur dioxide 65 " 

Hydrogen sulphide 55 " Silver, Other metals, 

Nitrogen monoxide 40 " Copper, Charcoal. 

Carbonic acid gas 35 " -n ^ 

^ , , & JJ Partial Conductors. 

Ethylene 35 " 

Carbon monoxide 9.42 " Water, Wood, 

Oxygen. 9.25 " T lie human bo ly, Marble, 

Nitrogen 6.50 " Cotton, Paper. 

Hydrogen 1.25 " „ 

, J _ Non-conductors. 
— [Saussure.) 

-n n n r 0ils ' Gutta-percha, 

Power, Candle An intensity of Porce]ain g^ 

light emitted from a luminous body equal to Dry wood ^ Ebonite, 

the light produced by a standard candle. gillc, Paraffine 

(See Candle, Standard.) Resins, Glass, 

The light-giving power of one standard Dry air. 

candle 

Heat decreases the conducting power of ele- 

Power, Candle, Nominal A term mentary substances. This decrease in the con- 
sometimes applied to the candle-power taken ducting power is approximately proportional to 
in a certain favorable direction. the increase of temperature. Carbon is an ex- 

This term is generally used in arc lighting. ception to the law, being a better conductor at a 

In the ordinary arc lamp the greatest amount of red or white heat than when cold ' 

light is emitted at a particular point, viz., from The resistance of some alloys, such as German 

the crater in the upper or positive carbon. (See silver and P Iatinoid > is bu * little effected by mod- 

Arc Voltaic.) erate changes of temperature. These alloys are, 

^ _, ,, „ J , therefore, employed in the construction of resist- 

Power, Candle, Rated A term ance coiJs 

sometimes used for nominal candle-power. At a r ' ed heat insulators become fairly good 

Power, Candle, Spherical The conductors of electricity. 

average or mean value of candle power At ver y low temperatures the conducting 

taken at a number of points around the source P owers of the metals increase - 

r y 1 . Wroblewski has shown that at extremely low 

" temperatures copper increases in its conducting 

Power, Conducting The ability of power for electricity. He cooled copper to —200 

a given length and area of cross-section of a degrees C, the temperature of the solidification 

substance for conducting light, heat, elec- of nitrogen, and found that at this temperature 

tricity or magnetism, as compared with an its conducting power increased to about nine times 

equal length and area of cross-section of its conducting power at O degrees C. 

some other substance taken as a standard. lt ™? be remarked ^re that at exceedingly 

low temperatures a metal would take in or absorb 

Power, Conducting, for Electricity heat from the surrounding medium with very 

— The ability of a given length and area of great rapidity. In this sense it might be said that 



POW.J 422 [Pow. 

its conducting power for heat was greatly in- layer of the conductor, so that the composition of 

creased. the substance is practically of no effect. 

Kohlrausch estimates the conducting power of Hughes has shown that the resistance of an iron 

distilled water at .000000CO0025, that of mer- telephone line of the usual diameter, to periodic 

cury being taken as unity. currents of about 100 per second, is somewhat 

The best conductors of electricity are the best more than three times its resistance for steady 

conductors of heat. currents. 

This fact is well illustrated by the following There is no such thing as conduction of elec- 
table from Ayrton : tricity in gases. Electricity makes its way through 

a gas by a sudden piercing of the dielectric, or, in 

Relative Conductivities per Cubic Unit. ot her words, by a disruptive discharge. (See 

Name of Metal. Electricity. Heat. Discharge, Disruptive.) In such a disruptive 

Silver, annealed 100 100 discharge it may be assumed that the gas be- 

Copper " 94.1 74.8 comes a conductor of electricity while the dis- 

Gold (< y-y r 4 3 charge is passing. It would then partake of the 

Platinum. . 16.6 9.4 nature of an electrolytic conductor, since the dis- 

j ron ^ .15.5 10. 1 charge takes place by means of a true locomotion 

»pj n j j . j- . of atoms. (See Conduction, Electrolytic.) 

^ ead ■ • • 76 7 '9 Power, Conducting for Heat The 

ability of a substance to transmit heat through 

The electric conductivity of porous conductors its mass. 

ductivT 3 mUCh m0rG raPldly than thG h6at C ° n " ThC mGtalS arC g °° d conductors of heat The ? 

y* ■ are also good conductors of electricity. The 

Practically perfect insulators for electricity can , , . c t. * j 1 ± • « A 

, conducting powers for heat and electricity are 
be obtained, but are unknown for heat. . ., .. , . ,, . c , , 

_ ' . nearly identical. As the temperature of a body 

Edlund believes the universal ether to be al- .. j ,. r , , . , 

increases, its conducting power for heat is de- 
most a perfect conductor. He bases this belief , ^ , r , . ,, . 

r creased. Carbon forms an exception to this 
on the phenomena of sun spots, the occurrence of 

-which is almost immediately followed by the ~,, „ r 7 . ?T r , r 

.... The /tow of heat across a wall formed of a 

occurrence of magnetic disturbances on the 7 . 7 ,, , r r , • , 

homogeneous material, the exposed faces of which 

ea ^ ' , , ' . ._ , are of equal extent and are maintained at a con- 

Lodge regards the lummiferous ether as being , ,.t. c , , . ., , 

& & r & stant difference of temperature, takes place in 

almost a perfect non-conductor, because he thinks accordance with the following laws . 
that conductors must be opaque. It may be sug- 

gested in this connection that Edlund's hypothesis < J /) The rate of flow across a11 Perpendicular 

as to the conductibility of magnetic effects through sectlons 1S the same - 

the ether is also capable of an explanation by the ( 2 -) A uniform drop of temperature occurs 

-effects of magnetic induction. from one side of the wall to the other in the direc- 

The conducting power for alternating currents tion in which the flow is taking place. 
is not the same as for steady currents. When (3.) The rate of flow is proportional to the dif- 

the alternations become very high, the difference ference in temperature. 

between these conducting powers of the metals The similarity between the laws of the flow of 
becomes almost inappreciable. heat under the circumstances just named and the 
Iron is an enormously worse conductor of flow of electricity through a conductor is evident; 
electricity than copper for rapidly alternating t he electrical current being the same in all parts 
currents, at least when the alternations are not f the circuit, a drop of potential occurring in 
too great. When, however, the alternations are the direction in which the current is moving, 
extremely high, such as those which are produced an d the flow being proportional to the difference 
by the discharge of a Leyden jar or lightning f potential, 
flash, the iron is as good a conductor as the cop- 
per. The reason for this is evident. The dis- Power, Conducting", Tables of 

charge in such cases keeps to the extreme outer Tables in which the relative conducting 



Pow.] 



423 



[Pow. 



powers of different substances are given. (See 
Resistance, Tables of) 

Power, Electric Power developed 

by means of electricity. 

Power, Electric, Distribution of 

The distribution of electric power by means 
of any suitable system of generators, connect- 
ing circuits and electric motors. 

Power, Electric Transmission of 

The transmission of mechanical energy by 
converting it into electric energy at one point 
or end of a line, and reconverting it into 
mechanical energy at some other point on the 
line. (See Energy, Electric, Transmission 
of.) 

Power, Horse A rate of doing work 

equal to 550 foot-pounds per second, or 33,- 
000 foot-pounds per minute. 

1 horse- power=745. 94 X 10 7 ergs per second. 
(See Erg.) 
" =745.941 watts. (See Watt.) 

" =42.746 lb. Fahr. heat units 

per min. (See Units, 
Heat.) 
" =23.748 lb. Cent, heat units per 

min. (See Units, Heat.) 

Power, Horse, Electric — Such a 

rate of doing electric work as is equal to 
746 watts or 746 volt-coulombs per second. 

This rate is equivalent to 33,000 foot-pounds 
per minute, or 550 foot-pounds per second. 

Just as 1 pound of water raised through the 
vertical distance of I foot requires the expendi- 
ture of a foot-pound of energy, so I coulomb of 
electricity acting through the difference of poten- 
tial of I volt requires a certain amount of work 
to be done on it. (See Coulomb. Volt. Po- 
tential, Electric.) 

This amount is called a volt-coulomb or joule, 
and measured in foot-pounds is equal to .737324 
foot-pounds. The volt coulomb, or joule, is there- 
fore the unit of electric work, just as the foot- 
pound is the unit of mechanical work. 

The electric work of any circuit in joules is 
equal to the product of the volts by the coulombs. 

If we determine the rate per second at which 
the coulombs pass, and multiply this product by 
the volts, we have a quantity which represents the 
electrical power, or rate of doing electrical work. 



But 1 ampere is equal to 1 coulomb per second; 
therefore, if we multiply the current in am- 
peres by the difference of potential in volts, the 
product is equal to the electrical power or rate of 
doing electrical work. 

The product of an ampere by a volt is called 
a volt-ampere, or a watt. 

One watt = .0013406 horse-power, or 

One horse-power =745.941 watts. 

CE 



Therefore the electrical horse-power = 



746 



where C = the current in amperes and E = the 
difference of potential in volts. 

Power, Multiplying, of Shunt 

(See Shunt, Multiplying Power of) 

Power of Periodic Current. — (See Cur- 
rent, Periodic, Power of.) 

Power, Portative — The carrying 

power of a magnet. (See Magtiet, Porta- 
tive Power of.) 

Power, Projecting, of Magnet The 

power a magnet possesses of throwing or pro- 
jecting its lines of magnetic force across an 
intervening air space or gap. 

The greater the air space the greater the mag- 
netic reluctance, and consequently the greater the 
magnetizing force required to overcome it. Mag- 
nets of great projecting power are generally of 
great length, to accommodate the long coils of 
wire required. 

Power, Kesuscitating, of Secondary Bat- 
tery Cell ■ — The power possessed by an 

apparently completely discharged secondary 
or storage cell of furnishing additional current 
after a protracted rest. 

This resuscitating power is probably due to 
depolarization. It is therefore present in primary 
as well as in secondary batteries. 

Power, Stray That part of the 

power employed in driving a dynamo, which 
is lost through friction, air churning or air 
currents, eddy currents, hysteresis, etc. 

Power, Thermo-Electric A num- 
ber which, when multiplied by the difference 
of temperature of a thermo-electric couple, 
will give the difference of potential thereby 
generated in micro-volts. (See Diagra?n, 
Thermo-Electric.) 



Pow.] 424 [Pri. 

Power, Units of Various units em- i metric h.-p., etc. = 42.162 Ib.-Fah., heat units 

ployed in the measurement of power. P er min * 

• The following table of units of power is taken " = 2 3-423 lb. -Cent., heat units 

from Hering's work on dynamo-electric machines. P er mm - 

TT ., r „ " ' = 10.621; klg.-Cent., heat 

Unit of Power. ,f & . 

units per mm. 

I erg per second. . = .0000001 watt. or ■, v *. 

& v " = .98634 horse-power heat 

1 watt, or 1 volt- y .7 f 

units per mm. 

ampere, or I , 

. ; n 1 horse-power =745.94 x io 7 ergs per 

joule per second, r ■. 

J , . second, 
or 1 volt- coulomb 

j " = 745.041 watts. 

per second = 10000000 ergs per second. '^° y \ 

x : ° , " .... = 33000 foot-pounds per mm. 

" = 44.2304 foot-pounds per JJ \ r 

. " =4562.33 kiogram - metres 

min. ^ "" . 5 

, ,-., per min. 

" =6.11622 kilogram - metres r . 

& " =42.746 Ib.-Fah., heat units 

per mm. 

" =.0573048 Ib.-Fah., heat unit per ™ 1T J" 

■ 3/J ^. " =23.748 lb. -Cent., heat units 

per mm. 

« = .318360 lb.-Cent., heatunit per mm. 

. " =10.772 klg.-Cent., heat 

per mm. ". 5 . 

r . . ~ , , units per min. 

" = .0144402 klgr.-Cent. heat . r , . , 

. " ==1.01385 metric horse- 

unit per min. 

, . , power. 

= .0013592 metric horse- t lb ._ F , h ., heat 

P ower - unit per min = 17.45 X io 7 ergs per sec. 

= .0013406 horse-power. u = 17.4505 watts. 

I foot-pound per Q ... 

. r j = -23718 metric norse-power. 

mm = 226043 ergs per second. 

7 fl " = .023394 horse-power. 

= .0226043 watt. , lb> Cent| heat 

= .13825 kilogram-metre per unit per min . _ = 3MI x io t er gs per sec. 

mm ' " =31.4109 watts. 

= .00003072 metric horse- „ = .04269 metric horse-power. 

P ower - " = .042109 horse-power. 

« = .000030303 horse-power. 1 klgr.-Cent., heat 

I kilogram - metre unit p er min 69.25 x io 7 ergs per sec. 

per min = 1635000 ergs per second. ti _ 6g24g watts> 

= .163500 watt. << = .09412 metric horse-power. 

= 7.23314 foot-pounds per „ = .092835 horse-power, 
min. 

« = .0002222 metric horse- Poynting's Law.— (See Law, Poyntzngs.) 

P ower - Practical Unit of Inductance, or Self- 
metric horse- = - 0002192 horse -P° wer ' Induction.— (See Inductance, or Self-Induc- 
tion. Practical Un it of.) 
power, or 1 ' J J 

French horse- Practical Unit of Magneto-Motive Force. 

power, or 1 che- ^(See Force, Magneto-Motive, Practical 

val-vapeur, or I Un i t j-j 

° rC -or 1 ^ W c! „„..,..■ v t~t ~ Practical Units.— (See Units, Practical.) 

or 1 Pferdekraft. = 735 75 X io 7 ergs per v ; 

second. Pressel. — A press switch or push connected 

= 735-75° watts. to the end of a flexible, pendant conductor. 

= 32549.0 foot-pounds per Pressure Wires.-(See Wires, Pressure.) 
min. 

«« = 4500 kilogram-metres per Primary Battery.— (See Battery, Pri?n- 

min. ary.) 



Pri.] 



425 



[Pro. 



Primary, Breaking- the 



-Breaking 



or opening the circuit of the primary of an 
induction coil. (See Primary, The.) 

Primary Coil. — (See Coil, Primary.) 

Primary, Making- the Closing or 

completing the circuit of the primary of an 
induction coil. (See Primary, The.) 

Primary Plate Condenser.— (See Plate, 
Primary, of Condenser.) 

Primary Spiral. — (See Spiral, Primary) 

Primary, The That conductor in 

an induction coil, or transformer, which re- 
ceives the impressed electromotive force, or 
which carries the inducing current. 

On changes in the current intensity in the 
primary, currents are induced in the secondary. 
(See Induction, Electro-Dynamic. Coil, Induc- 
tion. Transforiner.) 

Prime Conductor. — (See Conductor, 
Prime) 
Prime Motor.— (See Mover, Prime) 
Prime Mover.— (See Mover, Pri?ne.) 

Printer, Stock, Callahan's A form 

of printing telegraph used in sending stock 
quotations telegraphically. (See Telegraphy, 
Printing. Ticker, Stock) 

Printer, Stock, Phelps' A form of 

printing telegraph used in sending stock quo- 
tations telegraphically. (See Ticker, Stock. 
Telegraphy, Printing.) 

Probe, Electric A metallic con- 
ductor inserted in the body of a patient in 
order to ascertain the exact position of a 
bullet, or other foreign metallic substance. 

Two conductors are placed parallel to each 
other, and are separated at the extremity of the 
probe by any suitable insulating material. On 
contact with the metallic substance, an electric 
bell is rung by the closing of the circuit, or the 
same thing is more readily detected by the de- 
fection of the needle of a galvanometer, or by a 
telephone placed in the circuit. 

Process, Electrotyping- (See Elec- 
tro typing, or the Electrotype Process) 

Processes of Carbonization.— (See Car- 
bonization, Processes of) 



Production of Electricity by Lig-ht. — 

(See Electricity, Production of, by Light) 

Prog-nosis, Electric In electro- 
therapeutics, a prognosis, or prediction of the 
fatal or non-fatal termination of a disease, 
from an electro-diagnosis based on the exag- 
gerated or diminished reactions of the excit- 
able tissues of the body when subjected to 
the varying influences of electric currents. 
(See Diagnosis, Electro) 

Projections, Pacinotti —Radial 

projections or teeth in an armature core ex- 
tending from the central shaft, so as to form 
slots, pockets, or armature chambers, for the 
reception of the armature coils. 

The term Pacinotti projections was given to 
these teeth because they were first introduced by 
Pacinotti in his dynamo-electric machine. 

Projector, Mangin — A special form 

of search light. 

The Mangin reflector consists of a concavo- 
convex mirror, the convex surface of which is 
silvered and acts as a reflector. The radii of 
curvature of the two surfaces are such that the 
light undergoes the two refractions, i. e., on en- 
tering and on passing out of the mirror, in such a 
manner as to pass out of the mirror in absolute 
parallelism, and thus destroy all aberration. 






iMiMi'iiiiiir-^ 


It 


-/]/•;: r 




z^-^Wf^. j 


r S| " B ^f r i. F V "p 


jmJ 







Fig. 432. Mangin Projector. 

The Mangin projector is shown in longitudinal 
and in cross-section in Fig. 452, and the projector 
B, is placed in one end of the cylinder A, furnished 
with the openings for the ventilation of the cham- 
ber. 

The cylinder is supported on trunnions, and by 
means of screws can be given any desired inclina- 
tion, in a manner which will be readily under- 
stood from an inspection of the drawing. 

The source of light is an arc lamp of the focus- 
ing type. A small disc is placed in front of the 



Pro.] 



426 



[PuL 



arc in order to stop the direct light from the arc 
which would have divergent rays. The door C, 
is formed of a number of cylindrical lenses, placed 
parallel to one another, which cause the rays to 
diverge horizontally, when so desired. 

Prony Brake. — (See Brake, Prony.) 

Proportional Coils.— (See Coils, Propor- 
tional?) 

Proportionate Arms.— (See Arms, Pro- 
portionate) 

Proportionate Arms of Electric Bridge. 

— (See Arms, Proportionate) 

Prostration, Electric Physiological 

exhaustion or prostration, resembling that 
produced by sunstroke, resulting from pro- 
longed exposure to the radiation of an unusu- 
ally large voltaic arc. (See Sunstroke, 
Electric) 

Protection, Electric, of Houses, Ships 

and Building's Generally Means for 

protection against the destructive effects of a 
lightning discharge, consisting essentially in 
the use of lightning rods. (See Rod, Light- 
ning) 

Protection, Electric, of Metals 

(See Metals, Electrical Protection of) 

Protective Sheath. — (See Sheath, Pro- 
tective) 

Protector, Cable A device for the 

safe discharge of the static charge produced 
on the metallic sheathing of a cable, or on 
conductors surrounding or adjacent to the 
cable, consequent on changes in the electro- 
motive force applied to the conducting core of 
such cable. 

The cable protector is provided for the purpose 
of preventing the discharge of the charge from 
piercing and thus injuring the insulation of the 
cable itself. 

Protector, Comb A term some- 
times applied to a lightning protector or ar- 
rester, in which both the line and ground 
plates are furnished with a series of teeth, 
like those on a comb. (See Arrester, Light- 
ning) 



Protector, Yoltaic Battery 



-A de- 



vice for automatically disconnecting a voltaic 
battery, whenever the circuit in which it is 
placed becomes grounded. 

The battery protector is used in systems of elec- 
tric gaslighting, where, unless great care is exer- 
cised in insulating the circuits, considerable annoy- 
ance is often experienced from the readiness with 
which grounds are established. This arises from 
the high electromotive force of the spark ob- 
tained from the spark coil, piercing the insula- 
tion and establishing a ground through the gas 
pipes. 

Protoplasm, Effects of Electric Currents 

on Contractions observed in all pro- 
toplasm on the passage of an electric current 
through it. 

Protoplasm, the basis of plant and animal life, 
or the jelly-like matter that fills all organic cells, 
whatever may be the origin of such cells, suffers 
contraction when traversed by an electric cur- 
rent. 

An increased activity in the movements of a 
form of microscopic life called the a7)iceba is occa- 
sioned by slight shocks from an induction coil ; 
stronger discharges produce tetanic contractions, 
with, in some cases, expulsion of food or even of 
the nucleus. A uniform strength of current pro- 
duces contraction and imperfect tetanus. 

Pull. — A contact maker, similar in general 
construction to a push button, but operated 
by means of a pulling rather than a pushing 
force. 

The pull is preferable to the push in exposed 
positions, such as outer doors, where moisture is 
apt to injure pushes. 

Pull, Chain A chain pendant at- 
tached to a pendant burner for the move- 
ment of the wipe-spark spring and the 
ratchet in an electrically lighted gas burner. 

Pull, Door Bell, Electric A cir- 
cuit-closing device attached to a bell pull and 
operated by the ordinary motion of the pull. 

Pull, Electric Bell A circuit-clos- 
ing device operated by a pull. 

Fig- 453 shows a form of electric bell pull. On 
pulling the bell handle, contact springs, that 
rest on a ring of insulating material when the 



PuL] 



427 



[Pum, 



pull is in its normal position, are "brought into con- 
tact with a metal ring, thus completing the cir- 




Fig- 453' Electric Bell Pull. 

cuit. The bell pull is often used to replace the 
ordinary push button. 

Pulley, Driven A pulley attached 

to the driven shaft. (See Mover, Pri?ne.) 



Pulley, Driving 



A pulley attached 



to the driving shaft. (See Mover, Prime?) 

Pulsating Current. — (See Current, Pul- 
sating) 

Pulsation. — A quantity of the nature of 
an angular velocity, equal to 2 ^ multiplied 
by the frequency of the oscillation, or, equal 
to 2 it divided by the duration of a single 
period. 

Pulsatory Current. — [See Current, Pul- 
satory) 

Pulsatory Magnetic Field. — (See Field, 
Magnetic, Pulsatory.) 

Pulse, Electrical An electric oscil- 
lation. 

A momentary flow of electricity from a 
conductor, which gradually varies from the 
zero value to the maximum, and then to the 
zero value again, like a pulse or vibration in 
an elastic medium. 

Electric pulses are set up in conductors con- 
nected with the coatings of a Leyden jar, on the 
discharge of the same. Such pulses produce a 
series of electrical oscillations, which move alter- 
nately backwards and forwards, until the dis- 
charge is gradually dissipated. (See Oscillations ', 
Electric. ) 

The circumstances influencing the rate of 
propagation of an electric pulse through different 
parts of a closed circuit, according to Lodge, are — 



(1.) The extra inertia, or the so-called magnetic 
susceptibility in the conducting substance, es- 
pecially at its outer parts. 

(2. ) An undue constriction or throttling of the 
medium through which the disturbance is pass- 
ing. 

(3.) The nature of the insulating medium. 

Pump, Air, Geissler Mercurial 

A mercurial air pump, in which the vacuum 
is attained by the aid of a Torricellian vacuum.. 

In the Geissler Mercury Pump, Fig. 454, ai 
vacuum is obtained by means of the Torricellian 
vacuum produced in 
a large glass bulb that 
forms the upper ex- 
tremity of a barome- 
tric column. The 
lower end of this tube 
or column is con- 
nected with a reser- 
voir of mercury by 
means of a flexible 
rubber tube. To fill 
the bulb with mer- 
cury the reservoir is 
raised above its level, 
i. «?., above thirty 
inches, the air it con- 
tains being allowed to 
escape through an 
opening governed by 
a stopcock. The ves- 
sel to be exhausted is 
connected with the 
bulb, and by means 
of a two-way exhaus- 
tion COCk, COmmuni- Fig. 454. Geissler' 's Mer- 
cation can be made curial Air Pump. 

with the bulb, when it contains a Torricellian 
vacuum, and shut off from it while its air is being 
expelled. 

In actual practice the mercury is mechanically 
pumped into the barometric column, and the 
valves are opened either by hand, or automati- 
cally by electrical means. 




Pump, Air, Mechanical 



•A mechan- 



ical device for exhausting or removing the air 
from any vessel. 

An excellent form of air pump is shown in Fig. 
455, which is a drawing of Bianchi's pump. 

Three valves, all opening upwards, are placed- 



Pum.] 



428 



[Pjr. 




Fig. 455. Barrel of 
BianchVs Air Pump. 



at the top and bottom of the cylinder, and in the 
piston, respectively. These valves are mechan- 
ically opened and closed at the proper moment 
by the movements of the piston, i. e., their action 
is automatic. This enables a much higher vacuum 
to be obtained than when the valves open and 
close by the tension of the air. 

Mechanical pumps are unable to readily pro- 
duce the high vacua employed in most electric 
lamps. Mercury pumps 
are employed for this 
purpose. (See Pwrnp^ 
Air, Mercurial.) 

Pump, Air, Mer- 
curial A de- 
vice for obtaining a 
high vacuum by the 
use of mercury. 

Mercury pumps are 
in general of two types 
of construction, viz. : 

(i.) The Geissler 
pump. 

(2.) The Sprengel pump. (See Pump, Air, 
Geissler Mercurial. Pump, Air, SprengeVs 
Mercurial.) 

Puinp, Air, Sprengel's Mercurial 

A mercurial air pump in which the vacuum 
is obtained by 
means of the fall 
of a stream of mer- 
cury. 

In the Sprengel 
mercury pump, Fig. 
456, the fall of a mer- 
cury stream causes 
the exhaustion of a 
reservoir connected 
with the vertical 
tube, by the mechan- 
ical action of the 
mercury in entang- 
ling bubbles of air. 
These bubbles are 
largest at the begin- 
ning of the exhaus- 
tion, but become 
-smaller and smaller 
near the end, until, 
at last, the characteristic metallic click of mer- 
cury or other liquid falling in a good vacuum 




Fig. 456. Sprengel 's Mer- 
curial Air Pump. 



is heard. The exhaustion may be considered as 
completed when the bubbles entirely disappear 
from the column. 

The Sprengel pump produces a better vacuum 
than the Geissler pump, but is slower in its 
action. 

In actual practice, the mercury that has fallen 
through the tube is again raised to the reservoir 
connected to the drop tube by the action of a 
mechanical pump. 

Pumping- of Electric Lights. — A term 
sometimes applied to a pulsating or period- 
ical increase and decrease in the brilliancy of 
the light. 

This action is generally due to the periodic slip- 
ping of the belt or other driving mechanism. In 
the case of arc lamps it may also be caused by the 
improper action of the feeding device of the 
lamp. 

Puncture, Electro The application 

of electrolysis to the treatment of aneurisms 
or diseased growths. 

The blood is decomposed by the introduction 
of a fine platinum needle connected with the 
anode of a battery, and insulated, except near its 
point, by a covering of vulcanite. 

The kathode is a sponge-covered metallic plate. 

Puncture, Galvano A term some- 
times applied to electro-puncture. (See 
Puncture, Electro?) 

Punning of Telegraph Pole.— (See Pole, 
Telegraphic, Punning of) 

Push. — A name sometimes applied to a 
push button, or to a floor push. (See Push, 
Floor. Button, Push.) 

Push Button. — (See Button, Push.) 

Push-Button Rattler, — (See Rattler, 
Push-Button) 

Push, Floor A push button placed 

on the floor of a room so as to be readily 
operated by means of the foot. (See But- 
ton, Push) 

Pyknometer. — A term sometimes used 
for the specific gravity bottle employed in 
determining the specific gravity of a liquid. 

Pyrheliometer. — An apparatus for mea- 
suring the energy of the solar radiation. 



Tjr.] 



429 



[Qua. 



The pyrheliometer consists essentially of a 
short cylinder, the area of whose base is accu- 
rately determined. The cylinder being filled with 
a known weight of water, the water surface is ex- 
posed for a definite time to the sun's radiation, 
and the increase in temperature carefully deter- 
mined. The product of the weight of the water 
thus heated by the increase in degrees, gives 
the number of heat units, from which the total 
energy absorbed is readily calculable. In order 
to avoid loss by reflection or diffusion from the 
water surface, it is covered by a layer of lamp- 
black. (See Units, Heat. Calorimeter.) 

Pyro - Electricity. — (See Electricity, 
Pyro) 
Pyro-Magnetic Generator or Dynamo.— 

(See Generator, Pyro-Mag?ietic.) 

Pyro-Magnetic Motor. — (See Motor, Pyro- 
Magnetic?) 

Pyrometer. — An instrument for deter- 
mining temperatures higher than those that 
can be readily measured by thermometers. 

Pyrometers are operated in a variety of ways. 
A common method is by the expansion of a metal 
rod. 

Pyrometer, Siemens' Electric —An 

apparatus for the determination of tempera- 



ture by the measurement of the electric resist- 
ance of a platinum wire exposed to the heat 
whose temperature is to be measured, 

The platinum wire is coiled on a cylinder of 
fire-clay, so that its separate convolutions do not 
touch one another. It is protected by a platinum 
shield, and is exposed to the temperature to be 
measured while inside a platinum tube. 

The resistance of the platinum coil at O degree 
C. having been accurately ascertained, the temper- 
ature to which it has been exposed can be calcu- 
lated from the change in its resistance when ex- 
posed to the unknown temperature. 

Pyrometer, Siemens' Water A 

pyrometer employed for determining the tem- 
perature of a furnace, or other intense source 
of heat, by calorimetric methods, i. e., by the 
increase in the temperature of a known 
weight of water, into which a metal cylinder 
of a given weight has been put, after being 
exposed for a given time to the source of 
heat to be measured. 

When copper cylinders are employed, the in- 
strument possesses a range of temperature of 
i, 800 degrees F.; when a platinum cylinder is 
used, it has a range of 2,700 degrees F. 



Q 



Q. — A contraction for electric quantity. 

Quad. — A contraction sometimes em- 
ployed in place of quadruplex telegraphy. 
(See Telegraphy, Quadruplex) 

Quadrant. — A term proposed for the unit 
of self-induction. 

An earth quadrant is equal to io 9 centi- 
metres. 

In the United States the word henry is used 
for the unit of self-induction. (See Henry, A.) 

Quadrant Electrometer.— (See Electro- 
meter, Quadrant?) 

Quadrant Electroscope, Henley's.— (See 
Electroscope, Quadrant, Henley 's.) 

Quadrant, Legal A length equal to 

9,978 kilometres, instead of the assumed 
10,000 kilometres. 



Quadrant, Standard A length equal 

to 10,000 kilometres. 

Quadrature, In A term employed 

to express the fact that one simple periodic 
quantity lags 90 degrees behind another. 

The electromotive force of self-induction is said 
to be in quadrature with the effective electro- 
motive force or current. 

Quadruplex Telegraphy, Bridge Method 

of — (See Telegraphy, Quadruplex, 

Bridge Method of.) 

Qualitatire Analysis. — (See Analysis, 
Qualitative.) 

Quality or Timbre of Sound. — (See Sound, 
Quality or Tii7ibre of) 

Quantitative Analysis. — (See Analysis, 
Quantitative.) 



Qua,] 



430 



[Had. 



Quantity Armature. — (See Armature, 

Quantity?) 
Quantity, Connection of Battery for 

(See Battery, Connection of, for 

Quantity?) 
Quantity Efficiency of Storage Battery. 

— (See Efficiency, Quantity, of Storage Bat- 
tery?) 
Quantity, Unit of Electric A 

definite amount or quantity of electricity 
called the coulomb. (See Coulomb?) 

Although the exact nature of electricity is un- 
known, yet, like a fluid (a liquid, or gas), electricity 
can be accurately measured as to quantity. 



A current of I ampere, for example, is a 
current in which one coulomb of electricity passes 
in every second. 

A condenser of the capacity of I farad, is 
large enough to hold I coulomb of electricity 
if forced into the condenser under an electro- 
motive force of I volt. (See Capacity, Electro- 
static. Farad. Volt. Ampere.) 

Quiet Arc. — (See Arc, Quiet?) 

Quiet Discharge.— (See Discharge, Si- 
lent?) 

Quicking Solution. — (See Solution, 
Quieting.) 



R 



R. — A contraction used for ohmic resist- 
ance. 

p. — A contraction used for specific resist- 
ance. 

Radial Armature. — (See Armature, 
Radial?) 

Radially Laminated Armature Core. — 
(See Core, Armature, Radially-Laminated?) 

Radiant Energy. — (See Energy, Radiant.) 

Radiant Matter. — (See Matter, Radiant, 
or Ultra-Gaseous?) 

Radiate. — To transfer energy by means of 
waves. 

Radiating. — Transferring energy by means 
of waves. 

Radiation. — Transference of energy by 
means of waves. 

When an elastic body is set into vibration, 
whether it be the vibrations that produce light, 
heat or electricity, energy is charged on the 
body, and the body will then continue to vibrate 
until it imparts to some medium surrounding it 
an amount of energy exactly equal to that orig- 
inally imparted to itself. 

In the case of a sonorous body the energy is 
transferred from the vibrating body to the air 
around it. For example, in the case of an elastic 
metallic wire set into vibration, the wire will con- 
tinue to vibrate until it does as much work on 
the surrounding air as was originally done on it, 
in order to set it into vibration. 



In the case of a heated body the energy is 
transferred from the body to the luminiferous 
ether around it. For example, in the case of the 
same wire heated above the temperature of the 
air, the energy imparted to the molecules of the 
metal by the source of heat causes them to 
move towards and from one another. These 
to-and-fro motions of the molecules cause the 
surrounding ether to be set into waves, and as 
much energy is imparted to the ether, as was 
originally imparted to the wire in order to heat it. 

In the case of a luminous body the energy is 
transferred from the body to the luminiferous; 
ether. For example, if the wire is heated to 
luminosity by a certain amount of energy im- 
parted to it, the surrounding ether is now set 
into waves of both light and heat, which differ 
from one another only in their wave length, and 
the luminous body will continue to radiate light 
and heat until it imparts to the surrounding 
ether an amount of energy exactly equal to that 
originally imparted to it. 

So, too, in the case of a body charged with 
electricity. If disruptively discharged, the im- 
pulsive rush of electricity, so produced, causes the 
energy charged on it to be radiated as electro- 
magnetic waves into the surrounding ether. The 
discharging body is, to all intents and purposes, in 
the same condition as the vibrating elastic wire, 
and dissipates or radiates its energy in much the 
same manner. 

Radiation, Electro-Magnetic — 

The sending out in all directions from a con- 



Rad. 



431 



[Rad. 



ductor, through which an oscillating discharge 
is passing, of electro-magnetic waves in all 
respects similar to those of light except that 
they are of much greater length. (See Elec- 
tricity, Herts s Theory of Electro-Magnetic 
.Radiations or Waves.) 

Radiation of Electricity. — (See Electri- 
city, Radiation of.) 

Radiation of Lines of Force. — (See Force, 
Li?ies of, Radiation of.) 

Radical, Compound — A group of 

unsaturated atoms. 

A group of elementary atoms, some of the 
bonds of which are open, or not connected 
or joined with the bonds of other atoms. 
(See Atomicity?) 

For example, hydroxyl, HO, is a compound 
radical, with one of the two bonds of the diad 
oxygen atom, open or unsaturated. 

Radical, Simple ■ ■ — An unsaturated 

atom with its bond or bonds free. 

A single unsaturated atom as distinguished 
from an unsaturated group of atoms. 

Radicals. — Unsaturated atoms or groups of 
atoms, in which one or more of the bonds are 
left open or free. 

Radicals are either Simple or Compound. 

The radical may be regarded as the basis to 
which other elements may be added, or as the 
nucleus around which they may be grouped. 

Thus H a O, forms a complete chemical molecule, 
because the bonds of all its constituent atoms are 
saturated, thus H — O — H. But H — O — , or 
hydroxyl, is a radical, because its oxygen atom 
possesses one unsaturated or free bond. By 
combining with the radical (N0 2 ), it forms nitric 
acid, thus H — O — (N0 2 ) or H N0 3 . 

During electrolysis, the molecules of the elec- 
trolyte are decomposed into two groups of simple 
or compound radicals, called ions. These ions are 
respectively electro-positive and electro-negative, 
and are called kathions and anions. (See dons. 
Electrolysis. \ 

Radiometer, Crookes' An appara- 
tus for showing the action of radiant matter 
in producing motion from the effects of the 
reaction of a stream of molecules escaping 
from a number of easily moved heated sur- 
faces. (See Matter, Radiant, or C/llra- 
Gaseous) 



Radiometer, Electric, Crookes 



A radiometer in which the repulsion of the 
molecules of the residual atmosphere takes 
place from electrified instead of from heated 
surfaces. (See Radiometer, Crookes '.) 

Radio-Micrometer, Boys' An elec- 
trical apparatus for measuring the intensity 
of radiant heat. 

The action of the radio-micrometer depends on 
the deflection, by a magnetic field, of a suspended 
thermo-electric circuit composed of three metals, 
viz.: two bars of antimony and bismuth, or of 
their alloys, which are soldered side by side to 
the end of a minute disc or strip of copper foil, as 
shown in Fig. 457. This disc or foil of copper is 




Fig. 457. Boys' Radio-Micrometer. 

provided for the purpose of receiving the radia- 
tion that is to be measured. The upper ends of 
the thermo-couple are soldered to the ends of a 
long, narrow, inverted U-shaped piece of copper 
wire, which completes the thermo-electric circuit. 

The absorption of radiant energy by the cop- 
per disc connected to the thermo-electric couple 
produces an electric current, and the circuit, 
being suspended in a magnetic field, is at once 
deflected to a degree dependent on the intensity 
of the radiation, or of the current generated at 
the thermo-electric junction. 

The means adopted for the suspension of the 
system are shown in Figs. 457 and 458. A 
small piece of straight wire is soldered to the up- 



Rad.] 



432 



[RaL 



\m 



QUARTZ 
FIBRE 



GLASS 
TUBE 



X 



COPPER; 
WIRE 



per end of the copper stirrup, which completes 
the thermo-electric circuit. This wire is cemented 
to the lower end of a glass tube, the upper end 
of which is provided with a mirror, and the whole 
suspended, as shown, by a 
quartz fibre in the field of a 
powerful magnet. 

In a radio-micrometer made 
by Prof. Boys, the minuteness of 
the suspended circuit may be 
judged from the following ac- 
tual dimensions, viz.: Thermo- 
electric bars, ix^Xj^ inch ; 
copper circuit of number 36 
copper wire, 1 inch long and 
about fa inch wide ; copper 
heat-receiving surface, black- 
ened on the face exposed to the 
radiation, fa inch in diameter, 
or 4 x Ffr i nc h; receiver, fa inch 
square, ^^ inch thick ; quartz 
fibre 4 inches long, -^fa^ inch in 
diameter. 

This instrument, when pro- 
perly adjusted for extreme sen- 
sitiveness, should give clear in- o% /ju- 
dications when the blackened OCu ' 
surface is warmed but the Fig. 438. Boys' 
"STTUih) degree Centigrade. It Radio- Micrometer. 
will respond to the heat radiated on the surface 
of a half penny from a candle flame at a dis- 
tance of 1,530 feet. 

In order to avoid the disturbance due to the 
magnetic qualities of the antimony and bismuth 
bars, the central portions of the metallic block, 
inside which the system is suspended, is made 
of iron, as shown by the heavier shading in 
Fig. 457- 

This mass of iron serves as a magnetic screen 
to the thermo-electric bars, but permits the action 
of the field on the circuit. 

Radiophone. — A name sometimes given to 
the photophone. (See Photophone.) 

Radiophony. — The production of sound by 
a body capable of absorbing radiant energy 
when an intermittent beam of light or heat 
falls on it. 

The action of radiant energy, when absorbed 
by matter, is to cause its expansion by the conse- 
quent increase of temperature. This occurs even 
when the body is but momentarily exposed to a 



flash of light, but the instantaneous expansion 
thus produced immediately dies away, and by 
itself is indistinguishable. If, however, a suffi- 
ciently rapid succession of such flashes fall on the 
body, the instantaneous expansions and contrac- 
tions produce an appreciable musical note. 

The sounds so produced have been utilized hj 
Bell and Tainter in the construction of the Photo- 
phone. (See Photophone.) 

Railroad, Electric A railroad, or 

railway, the cars on which are driven or pro- 
pelled by means of electric motors connected 
with the cars. 

The electric current that drives the motor is 
derived either from storage batteries placed on 
the cars, or from a dynamo-electric machine, or 
battery of dynamo-electric machines, conveniently 
situated at some point on the road. The current 
from the dynamo is led along the line by suitable 
electric conductors and is passed into the electric 
motor as the car runs along the tracks in various 
ways, viz. : 

Systems for the electric propulsion of cars may, 
therefore, be divided into the dependent system, in 
which the driving current is obtained from conduc- 
tors placed somewhere outside the cars, and the 
independent system, where the current is derived 
from primary or secondary batteries placed on 
the cars. (See Railroads, Electric, Dependent 
System of Motive Power for. Railroads, Electric, 
Independent System of Motive Power for .) 

In the dependent system, the conductors which 
supply the car with current are placed either 
overhead, on the surface of the road-bed or un- 
derground. Thus arise three divisions of the 
dependent system: 

(1.) The Surface System. 

(2.) The Underground System. 

(3.) The Overhead System. 

(1.) The Surface System. — By placing one or 
both rails in the circuit of the dynamo and taking 
the current from the tracks by means of sliding 
or rolling contacts connected with the motor. 

(2. ) The Underground System. — By placing the 
conducting wires parallel to each other in a longi- 
tudinally slotted underground conduit in the road- 
bed, and provided with two central plates, insu- 
lated from one another and connected respectively 
to the motor terminals, and taking the current 
by means of a traveling brush or roller, called a 
plow, sled or shoe. On the movement of the car 
over the track, these traveling contacts touch the 



Kai.] 



433 



[Rai. 



two parallel line conductors in the conduit and 
fake the electric current therefrom. (See Plow. 
Sled.) 

(3.) The Overhead System. — By placing the 
fine conductors on poles along the road, and 
taking the current therefrom by means of suitable 
traveling contacts called trolleys, or by sliders. 

Where a single conductor is employed, the re- 
turn conductor generally consists of the track 
itself, or of the track and ground. (See Trolley.') 

The first method, viz., that of using the tracks 
alone as conductors, is not much employed. 

The use of the track and ground as a return for 
the current is now very generally employed. 

In some systems the track is divided into sec- 
tions which are successively brought into connec- 
tion with the main conductors by contacts effected 
by the attraction between magnets carried on the 
car and contact pieces of magnetic material placed 
below the surface. The rail section thus tempo- 
rarily energized is placed in connection with the 
motor. 

In order to regulate the speed, various devices 
are employed to vary the current strength in the 
motor circuit. These devices consist essentially 
of rheostats or resistances introduced into, or re- 
moved from, the motor circuit on the movement 
by hand of a lever that forms part of the circuit, 
over contact plates connected to the resistance 
coils. 

In order to change the direction of the car, the 
direction of rotation of the electric motor is 
changed. This is effected by some form of re- 
versing gear or mechanism that changes the di- 
rection of rotation of the motor, either by shifting 
the brushes, by changing the field, or by any 
other means. (See Telpherage. Motor, Elec- 
tric. Rheostat.) 

Railroads, Absolute Block System for 

A block system in which one train 

only is permitted to occupy a given block at 
any time. (See Railroads, Block System for .) 

Railroads, Automatic Electric Safety Sys- 
tem for A system for automatically 

preventing the approach of two trains at any 
speed beyond a predetermined distance of 
each other. 

The system consists essentially in the automatic 
closing of the circuit of an electric motor placed 
on the locomotive between the steam dome and 
the sand box. This motor is in circuit with a 
local battery placed on the cow-catcher, and in- 



troduced in the circuit of the motor by a magnet 
placed on the cow-catcher, as shown in Fig. 459, 




Fig. 459. Locomotive with Safety System. 

which represents a locomotive provided with this 
system. 

The magnet is on open circuit with generators 
placed on the rear car of a second train, or with 
generators at a bridge or crossing. 

By means of double sectional-conductors placed 
along the track, the generators are automatically 
closed through the magnet, one conductor being 
in permanent connection with the magnet, while 
the other is connected to the generator in the rear 
car of a second train, at a switch or crossing. The 
other terminals of the magnet and generators are in 
permanent electricial connection with the rails, 
which are employed as return ground conductors. 

Fig. 460 shows the application of the safety 
electric system to a bridge. 




Fig. 460. Safety System for Bridge. 

Fig. 461 shows the application of the safety 
system at grade crossing 




Fig. 461. Safety System for Grade Crossing. 

The author is indebted to Mr. E. P. Thompson 
for cuts and general description. 

Railroads, Block System for A sys- 
tem for securing safety from collisions of mov- 
ing railroad trains by dividing the road into a 
number of blocks or sections of a given 
length, and so maintaining telegraphic com- 
munication between towers located at the 
ends of each of such blocks as to prevent, 



EaL] 



434 



[Bui, 



by the display of suitable signals, more than 
one train or engine from being on the same 
block at the same time. 

There are two kinds of railway block systems 
in common use, viz.: 

(I.) The Absolute Block System. 

(2.) The Permissive Block System. 

In the absolute system, which is the safer, one 
tram only is permitted on any particular block at 
a given time. 

In the permissive block system more than one 
train is permitted, under certain circumstances 
and conditions, to occupy the same block simul- 
taneously, each train then being notified of the 
fact that it is not alone on the block. 

The absolute block system, though expensive 
to construct and maintain, is the only one that 
should be permitted by law to exist on roads whose 
traffic exceeds a certain amount. 

An absolute block system is employed on the 
London Underground Railroad, and on the Penn- 
sylvania Railroad Systems. 

The system in use on the New York Division 
of the Pennsylvania Railroad is as follows : 

The road between Philadelphia and Jersey City 
is divided into some seventy sections, the length 
of each section being dependent on the amount of 




Fig. 462. Block Tower. 

■daily traffic , thus, between Jersey City and New- 
ark, where the traffic is great, there are some 
fifteen sections, although the distance is only 7.9 
miles. 

In each block-tower there are connections with 
three separate and distinct telegraph lines or cir- 
-cuits, viz. : 

(1.) A line or wire called the train wire, con- 
necting the block-tower with the General Dis- 
patcher's office at Jersey City. This line is used 
for sending train orders only. 

(2. ) A line or wire called the block wire, con- 



necting each block-tower with the next tower on 
each side of it. 

(3.) A line or wire called the message wire, and 
used for local traffic or business. 

The general arrangement of the block-tower is 
shown in Fig. 462. 

Each of the block-towers is sufficiently elevated 
above the road-bed to afford the operator an un- 
obstructed view of the tracks. 

The operator, having ascertained the actual 
condition of the track, either by observation or by 
telegraphic communication with the stations on 
either side of him, gives notice of this condition to 
all trains passing his station by the display of 
certain semaphore signals. 

The semaphore signals as used on the Penn- 
sylvania Railroad are shown in Figs. 463 and 464. 

The form shown in Fig. 463 is used in the abso- 




Fig. 463. Semaphore Signal — Absolute System, 

lute system, and that shown in Fig. 464 in the per- 
missive system. These signals consist essentially 
of an upright support provided with a movable 
arm A B, called the semaphore arm, capable of 
being set in any of two or three positions. The 
semaphore signal is placed outside the signal 
tower, often several hundred feet away, but is 
readily set from the tower in any of the desired 
positions by the operator, by the movement of 
rods connected with levers. 

In the permissive system, the semaphore arm 
can be set in three positions, viz.: 

(1.) In a horizontal position, or where the 
semaphore arm makes an angle of 90 degrees with 
the upright. 

(2.) Or it may be dropped down from the 
horizontal position through an angle of 75 
degrees, as shown in Fig. 463. 

(3.) Or it may occupy a position exactly inter- 



Eai.] 



435 



[Riii. 



mediate between the first and second, or 37 30' 
below the horizontal, as shown in Fig. 464. 

Position No. I is the danger signal, and when 
it is displayed the train may not enter the block 
it governs. 

Position No. 2 shows that the track is clear, 
and that the train may safely enter the block it 
governs. 

Position No. 3, which is used in the permissive 
block system, only signifies caution, and permits 
the train to cautiously enter the block and look 
out for further signals. 

The semaphore arm consists of a light wooden 
arm, 11 inches wide by 5 J feet in length, painted 
red or other suitable color that can be easily dis- 
tinguished by daylight. 

By night the positions of the semaphore arm 
are indicated by colored lights. These lights are 




Fig. 4b 4- 



pi 
Semaphore Signal — Permissive System. 



operated as follows, viz. : in the absolute system, 
the semaphore arm A B, pivoted at A, bears at 
its shorter end a disc or lens of red glass R, and, 
in the permissive system, below this another disc 
or lens of green glass G. An oil lantern, pro- 
vided with an uncolored glass lens, is so sup- 
ported on a bracket fastened to the upright that 
when the semaphore arm points to danger the 
red glass is immediately in front of the lantern ; 
when it points to caution, the green glass is in 
front of the lantern; but when it points to safety, 
the lantern is left uncovered save by its uncolored 
glass. 

At night, therefore, when the semaphore arm 
is set to danger, a red light is displayed; when it 
points to caution, a green light is displayed; and 
when it points to safety, a white light is displayed. 

In some systems the position of the semaphore 



arm is shown at night by means of light reflected 
from a parabolic mirror, at the focus of which the 
signal lantern is placed. This method possesses 
the advantage over other systems of rendering it 
very improbable that the engineer would mistake 
an ordinary light for a signal light. 

The green light is only used in the permissive 
block system. In the absolute block system, the 
semaphore arm has two positions only ; viz., dan- 
ger, or horizontal, and safety, or 75 degrees below 
the horizontal. 

A single arm is used when it is intended to 
govern a single track only. Where the cundition 
of a number of tracks is to be indicated, several 
arms are employed, one above the other. 

When semap ^.ore signals are placed on each side 
of a double-track road, the semaphore arm point- 
ing to the right of the vertical support governs 
the line running to the right. 

When the semaphore signals are placed at 
junctions or switch-crossings, the operator in the 
signal-tower opens or closes the switches from 
the tower by the movements of levers that set the 
switches, and then displays the proper semaphore 
signal for that crossing or route ; red, or danger, 
if the route is blocked, and white, or safety, if it 
is clear. Here the interlocking apparatus is em- 
ployed, which consists in devices by means of 
which, when a route has once been set up and a 
signal given for that route, the switches and sig- 
nals are so interlocked that no signal can pos- 
sibly be given for a conflicting route. 

The signals or switches are operated by means 
of iron rods passing over rollers or pulleys. 
These rods are attached by suitable connections 
to the switch or semaphore signals, and are 
operated by means of levers from the signal- 
tower. Switches can be operated as far as 1,000 
feet from the tower; signals as far as 2,500 feet. 

Colored switch-signals are placed opposite the 
end of the switches to indicate the positions of 
the switch. These signals consist of red and 
white discs for day, and a lantern provided with 
red and white glasses for night. When the 
switch on any line is open, the switch-signal shows 
red; when shut, it shows white. These switch- 
signals are only used in the yards. 

No passenger train is permitted on a block, 
after another train has passed the signal station, 
until a dispatch has been received from the 
station ahead that the train has passed and the 
block is thus cleared. 

As an additional precaution against rear col- 



KaL] 



436 



[Rai, 



lisions, tail-lights are displayed at the ends of the 
trains. These consist ofl an terns placed on each 
side of the rear end of the last car. These 
lanterns are furnished with three glass slides. 
The side of the lantern towards the rear of the 
car shows a red light; that to the front and side 
of the car shows a green light. The engineer, 
looking out of the cab, can thus see a green light, 
which serves as a "marker" and indicates to 
him that his train is intact. By day a green flag, 
placed in the same position as the lantern, serves 
the same purpose as a marker. An observer on 
the track, or in the tower, sees the red lights on 
the rear of the train when it has passed. 

Freight trains are now run on separate tracks, 
except in places where the extra tracks are not 
yet completed. Here they do not run on schedule 
time, but are permitted to follow one another at 
intervals that depend on the condition of the 
tracks as shown by the signals displayed. 

Railroads, Electric, Continuous Over- 
head System of Motive Power for 

A variety of the dependent system of motive 
power for electric railroads in which a con- 
tinuous bare conductor is connected with the 
terminals of a generating dynamo, and sup- 
ported overhead by suitable means, and a 
traveling wheel or trolley is moved over the 
same by the motion of the car, in order to 
carry off the current from the line to the car 
motor. (See Railroads, Electric, Depend 
ent System of Motive Power for '.) 

Railroads, Electric, Continuous Surface 

System of Motive Power for — A 

variety of the dependent system of motive 
power for electric railroads, in which the ter- 
minals of the generating dynamo are con- 
nected to the continuous bare metallic con- 
ductor that extends along the entire track on 
the surface of the roadway or street, and from 
which the current is taken off by means of a 
traveling conductor connected with the mov- 
ing car. (See Railroads, Electric, Continu- 
ous Underground System of Motive Power 
for.) 

Railroads, Electric, Continuous Under- 
ground System of Motive Power for 

A variety of the dependent system of motive 
power for electric railways, in which a con- 
tinuous bare conductor is placed under- 



ground in an open slotted conduit, and the 
current taken off from the same by means of 
sliding or rolling contacts carried on the mov- 
ing car. (See Railroads, Electric, Depend- 
ent System of Motive Power for) 

Railroads, Electric, Dependent System 

of Motive Power for A term now 

generally used for a system of motive power 
for the propulsion of electric railway cars, in 
which the electric current is taken from wires 
or conductors connected with electric sources 
external to the cars. 

A dependent system of motive power for elec- 
tric railways includes three distinct varieties^ 
namely : 

(i.) The Underground System. 

(2.) The Surface System. 

(3.) The Overhead System. 

In all of these systems the bare conductor con- 
nected with the terminals of a generating dynamo 
may form either one continuous wire or it can 
be divided into separate portions or sections. 

The underground system embraces two distinct 
varieties : 

1 st. A continuous bare conductor placed in an 
open slotted conduit. 

2d. A sectional bare conductor placed in an 
open slotted conduit. 

In the first variety of the underground system, 
bare conductors are placed in an open slotted 
conduit, and connected with the terminals of a. 
dynamo-electric machine which generates the 
current that is to be employed for the propulsion 
of the cars. Traveling contacts placed on the 
car and connected with an electric motor, carry 
off the current from the bare conductor by rolling 
or sliding over it. 

In the second variety of the underground sys- 
tem, a section of a bare conductor, or bare metal- 
lic points that, on the passage of the car over 
them are automatically connected with the gen- 
erating dynamo, replace the continuous metallic 
conductors of the first system. 

In the surface system, the wires or conductors 
that are connected with the generating dynamo, 
instead of being placed in the underground open 
slotted conduit, are placed directly on the surface 
of the street or roadbed and the current carried 
off from the same by suitable contacts placed on 
the car. 

In most cases, however, in which the surface 
system is adopted, the conductors that are con- 



IliiL] 



437 



[RaL 



nected with the generating dynamo do not ex- 
tend throughout the entire length of the track, 
but are limited to sections of the track that are 
suitably connected with the generating dynamo. 
In some of these systems arrangements are 
devised, by which the car, as it passes over the 
track, automatically connects these sections with 
the generating dynamo while passing over the 
same, and disconnects them after such sections 
have been passed. 

The overhead system embraces two varieties: 

(i.) A continuous trolley wire. 

(2.) A divided or sectional trolley wire. 

In the continuous trolley wire system, the cur- 
rent is taken off from the continuous wire by 
means of a trolley wheel that moves over the 
trolley wire. 

Such a system is especially suitable for suburban 
districts or small towns. In such a system the 
trolley wire is connected with a number of feeder 
wires that either extend from the generating sta- 
tion the entire length of the line, and are con- 
nected with such line at suitable points; or, sepa- 
rate feeders extend from the station to points on 
the line where they are tapped into the trolley 
wire. 

In the divided or sectional trolley wire system 
the wire is divided into suitable sections, and 
feeders extend the entire length of the line and 
are connected to the central points of each section; 
or, the feeders extend the entire length of the 
line and tap into both ends of the section. 

The author is indebted to G. W. Mansfield for 
the principal facts contained in the above descrip- 
tive matter. 

Railroads, Electric, Divided Overhead 
System of Motive Power for A sec- 
tional overhead system of motive power for 
electric railroads. (See Railroads, Electric, 
Sectional Overhead System of Motive Power 
for) 

Railroads, Electric, Divided Surface 
System of Motive Power for A sec- 
tional system of motive power for electric 
railroads. (See Railroads, Electric, Sec- 
tional Surface System of Motive Power 
for) 

Railroads, Electric, Divided Under- 
ground System of Motive Power for ■ 

— A sectional system of motive power for 
electric railroads. (See Railroads, Electric, 



Sectional Underground System of Motive 
Power for) 

Railroads, Electric, Double-Trolley Sys- 
tem for A system of electric railroad 

propulsion, in which a double trolley is em- 
ployed to take the driving current from two 
overhead trolley wires. 

The double-trolley system differs from the 
single- trolley system in that it employs no earth 
return. The parallel wires also avoid the effects 
of injurious induction in neighboring telegraph 
or telephone wires. (See Railroads, Electric, 
Dependent System of Motive Power for.) 

Railroads, Electric, Independent System 

of Motive Power for A term for the 

electric propulsion of railway cars by means 
of primary or storage batteries placed on the 
car and directly connected with the motor. 

This is called the independent system, because r 
unlike the dependent system, the energy required 
for the propulsion of the car is obtained directly 
from the energy of the electric source placed on 
the car, instead of, as in the dependent system, 
outside of the car. 

Railroads, Electric, Sectional Overhead 

System of Motive Power for A variety 

of the dependent system of motive power for 
electric railroads, in which sections of bare 
conductors are supported overhead on poles 
placed along the railroad track, and the cur- 
rent taken off from the same by means of 
traveling conductors such as the trolley 
wheel, which is moved over the trolley wire 
by the motion of the car. 

Various systems are employed for connecting 
the different sections of the trolley wire by means 
of feeder wires with the generating dynamo. 
(See Railroads, Electric, Dependent System of 
Motive Power for.} 

Railroads, Electric, Sectional Surface- 
System of Motive Power for A 

variety of the dependent system of motive 
power for electric railroads in which conduc- 
tors are placed on the roadbed or along the 
track, and the current taken off from the same 
by means of contacts connected with the mov- 
ing car, and so arranged as to automatically 
switch in such bare sections on the passage 



EaL] 



438 



[Ray. 



of the car over them, and to switch them out 
as the car leaves them. (See Railroads, 
Electric \ Dependent System of Motive Power 
for.) 

Railroads, Electric, Sectional Under- 
ground System of Motive Power for 

— A variety of the dependent system of 
motive power for electric railroads in which a 
sectional conductor is placed underground in 
a slotted conduit, and the current taken from 
the same by means of sliding or rolling con- 
tacts connected with the moving car. (See 
Railroads, Electric, Dependent System of 
Motive Power for) 

Railroads, Electric, Section Line of 

— Any part of the overhead electric conduc- 
tors insulated from other parts so as to permit 
its supply of electric power to be separately 
controlled. 

Railroads, Electric, Signal Service Sys- 
tem for The system of electric signals 

used on railways for ascertaining the condition 
of the roads, sending instructions to engineers, 
and conveying intelligence generally from 
stations along the road to the running trains. 

Railroads, Electric, Single-Trolley Sys- 
tem A system of electric railroad 

propulsion in which a single trolley is em- 
ployed to take the driving current from a 
single overhead trolley wire. 

The earth, or a conductor placed along the 
track on the roadbed, acts as the return. (See 
Railroads, Electric, Dependent System of Mo- 
tive Rower for.) 

Railroads, Permissive Block System for 

A block system in which more than 

one train is permitted under given conditions 
to occupy the same block simultaneously. 
(See Railroads, Block System for.) 

Railway, Electric An electric rail- 
road. (See Railroad, Electric) 

Range, Molecular The distance at 

which the molecules of matter exert a sensi- 
ble attraction for one another. 

This distance has been estimated in the case of 
zinc and oxygen as equal to about the ten-mil- 
lionth of a millimetre. 



Ratchet-Pendant Argand-Electric Burner. 

— (See Burner, Argand-Electric, Ratchet- 
Pendant) 

Ratchet-Pendant Electric Burner. — (See 
Burner, Ratchet-Petidant, Electric) 

Ratchet-Pendant Electric Candle Burner. 

— (See Burner, Ratchet-Pendant Candle 
Electric) 

Ratio, Velocity A ratio, in the 

nature of a velocity, that exists between the 
dimensions of the electrostatic and the elec- 
tro-magnetic units. 

This ratio will be understood from the com- 
parison of the following units. In each case the 
numerator gives the dimensions in the electro- 
static and the denominator the dimensions in the 
electro-magnetic system : 



Quantity, 



u i L f T _ t 



M^L 






Here the value of the ratio, viz., the length 
divided by the time, is clearly in the nature of a 

velocity, for V = — . 



Potential, 



Capacity, 



M i l} T-i 



Resistance, 



M* 


3 

L"* 


T 


-2 


L 


T 2 


= 


L2 

T* 


L-i 


T 




T'2 



V* 



1_ 

L T-i L* V* ' 

A remarkable similarity exists between the 
value of the velocity expressed in C. G. S. units, 
and the velocity of light, which is of great signifi- 
cance in the electro-magnetic theory of light. (See 
Light, MaxwelP s Electro-Magnetic Theory of.) 

The velocity of light is 2.9992 X io 10 cen- 
timetres per second. 

The velocity ratio, v, is 2.9800 X io 10 centi- 
metres per second. 

Rattler, Push-Button A device 

connected with a push button to show that 
the bell connected at a distant point, in. the 
circuit of a push button, rings when the button 
is pressed. 

Ray, Actinic A ray of light or other 

form of radiant energy that possesses the 



Ray.] 



439 



[Rec. 



power of effecting chemical action. (See 
Decojnposition .) 

All rays of light, and even some of those in- 
visible to the human eye, are actinic to some 
particular chemical substance or another. 
"Whether the ether waves produce the effects of 
heat, of light or of chemical decomposition de- 
pends on the nature of the material on which 
they fall, as well as on the character of the waves 
themselves. 

Ray, Electric (Raia torpedo) A 

species of fish named the ray, which, like the 
electric eel, pos- 
sesses the power 
of producing elec- 
tricity. 

The electric or- 
gan is situated at 
the back of the 
head, and consists 
of hundreds of poly- 
gonal, cellular 
laminae, supplied 
with numerous 
nerve fibres, as 
shown in Fig. 465. 
(See Fishes. Elec- 
tric.) 

Rayleigh's 
Form of Clark's 
Standard Toltaic 

Cell.— (See Cell, 
Voltaic, Stand- 
ard, Rayleigtis 

Form of Clark's.) Fig- 4& 5- TJie Raia Torpedo. 

Reaction. — In electro-therapeutics mus- 
cular contractions following the closing or 
opening of an electric circuit. 

Reaction Coil. — (See Coil, Reaction.) 

Reaction of Defeneration. — (See Degen- 
eration, Reaction of.) 

Reaction of Exhaustion. — (See Exhaus- 
tion, Reaction of.) 

Reaction Principle of Dynamo-Electric 
Machines. — (See Machine, E>ynamo-Elec- 
tric, Reaction Prmciple of.) 

Reaction Telephone.— (See Telephone, 
Reaction.) 




Reaction Time.— (See Time, Reaction.) 

Reaction Wheel, Electric (See 

Wheel, Reaction, Electric.) 

Reactions, Kathodic and Anodic Electro- 
Diag-nostic The reactions which oc- 
cur at the kathode or anode of an electric 
source placed on or over any part of a living 
body. 




Fig. 466. Kathodic and Anodic Reactions. 

Fig. 466, from De Watteville's " Medical Elec- 
tricity" represents what he assumes takes place at 
the points of entrance and exit of the current in a 
nerve submitted to the action of the anode of an 
electric source. Two zones are formed, an anodic 
and a kathodic zone; the virtual anode is formed 
by the portion of the skin nearer the nerve, and 
the virtual kathode by the adjoining muscles. 
There are thus formed two zones of influence- 
one immediately around the anode, called the. 
polar or anodic electrotonic zone, and one sur- 
rounding this and including the virtual kathode, 
and called the peripolar, or kathelectrotonic zone. 

Reading- Telescope. — (See Telescope* 
Reading?) 
Real Efficiency of Storage Battery. — 

(See Efficiency, Real, of Storage Battery?) 

Real Hall Effect.— (See Effect, Hall, 
Real.) 

Recalescence. — The property, possessed 
by incandescent steel when cooling, of 
again becoming incandescent after a certain 
degree of cooling has been reached. 

The property of recalescence was first pointed 
out by Barrett. 

A steel wire heated at the middle or near one 
end to a bright red, and allowed to cool in 
a dim light, will cool until a low red heat is 
reached, when it will be observed to reheat at 
some point in the originally heated portion. This 
reheating is manifested by a brighter red spot 



Rec. 



440 



[Rec. 



which moves along the portion originally heated. 
This reheating is called recalescence, and is due 
to latent heat (potential energy), which, disap- 
pearing when the bar was heated, again becomes 
sensible (kinetic energy) on cooling. 

The temperature at which recalescence takes 
place is sensibly the temperature at which heated 
steel regains its magnetizability. 

Keceived Current. — (See Current, Re- 
ceived^) 

Receiver, Gramophone The re- 
ceiver employed in the gramophone. (See 
Gramophone) 

Receiver, Graphophone The re- 
ceiver employed in the graphophone. (See 
Phonograph) 



Receiver, Harmonic 



-A receiver, 



employed in systems of harmonic telegraphy, 
consisting of an electro-magnetic reed, tuned 
to vibrate to one note or rate only. (See Te- 
legraphy, Grays Harmonic Multiple) 

Receiver Magnet. — (See Magnet, Receiv- 
ing) 

Receiver, Phonographic The ap- 
paratus employed in a telephone, phono- 
graph, graphophone or gramophone for the 
reproduction of articulate speech. (See 
Phonograph) 

Receiver, Telephonic The receiver 

employed in the telephone. (See Tele- 
phone) 

Receptive Device, Electro (See 

Device, Electro-Receptive) 

Receptive Device, Magneto — 

Device, Magneto-Receptive) 



(See 



Reciprocal 



-The reciprocal of any 



number is the quotient arising from dividing 
unity by that number. 

Thus, for example, the reciprocal of 4, is \ or 
.250. 

The conducting power of any circuit is equal 
to the reciprocal of its resistance ; or, in other 
words, the conducting power is inversely propor- 
tional to the resistance. 



The following table contains the reciprocals 
of the numerals up to 1 00 : 

TABLE OF RECIPROCALS. 





Re- 




Re- 




Re- 




Re- 




Re- 





cipro- 
cal. 


No. 


cipro- 
cal. 


No. 


cipro- 
cal. 


No. 


cipro- 
cal. 


No. 


cipro- 
cal. 


2 


0.5000 


22 


o-0455 


42 


0.0338 


62 


0.0161 


82 


0.0122 


3 


o.3333 


23 


0.0435 


43 


0.0233 


b.3 


0.0159 


«3 





0120 


4 


0.2500 


24 


0.0417 


44 


0.0227 


04 


0.0156 


84 





0119 


5 
6 


0.2000 
0. 1667 


25 

26 


0.0400 
0.0385 


45 

46 


0.0222 
0.0217 


05 
66 


0154 
0.0152 


»5 

86 






0118 
0116 


7 


0.1429 


27 


0.0370 


47 


0.0213 


67 


0.0149 


»7 





01 15 


8 


0.1250 


28 


0.0357 


4 8 


0.0208 


68 


0.0147 


88 





0114 


9 


O.IIII 


29 


0.0345 


49 


0.0204 


09 


0.0145 


89 





0112 


JO 


0. 1000 


30 


0-0333 


50 


0.0200 


70 


0.0143 


90 





OIII 


11 


. 0909 


31 


0.0323 


5i 


0.0196 


7i 


0.0141 


9i 





OIIO 


12 


0.0833 


32 


0.0313 


52 


0.0192 


72 


0.0139 


92 





0109 


13 


0.0769 


33 


• 0303 


53 


0.0189 


73 


0.0137 


93 





oic8 


M 


0.0714 


34 


0.0294 


54 


0.0185 


74 


0.0135 


Q4 





0106 


15 
16 


0.0667 
0.062s 


35 
36 


0.0286 
0.0278 


55 

56 


0.0182 
0.0179 


75 

76 


0.0133 
0.0132 


95 

96 







0105 
0104 


i7 


0.0588 


37 


0.0270 


57 


0.0175 


77 


0.0130 


97 





0103 


it) 


0.0556 


3« 


0.0263 


5« 


0.0172 


78 


0.0128 


9« 





0102 


19 


0.0526 


39 


0.0256 


59 


0.0169 


79 


0.0127 


W 





OIOI 


20 


0.0500 


40 


0.0250 


60 


0.0167 


80 


0.0125 


100 





OIOO 


21 


0.0476 


41 


0.0244 


61 


0.0164 


81 


0.0123 







— [Clark 6° Sabine.) 
Recoil Circuit. — (See Circuit, Recoil) 

Record, Chronograph A record 

made by means of a chronograph for the pur- 
pose of measuring and recording small "inter- 
vals of time. (See Chronograph, Electric) 

— The irregular 



Record, Gramophone — 

indentations, cuttings or tracings made by a 
point attached to the diaphragm spoken 
against, and employed in connection with the 
receiving diaphragm for the reproduction of 
articulate speech. 

Record, Graphophone — The record 

made by the movement of the diaphragm of 
the graphophone. (See Phonograph) 

Record, Phonographic The record 

produced in a phonograph, for the subse- 
quent reproduction of audible articulate 
speech. 

Record, Telephonic The record 

produced by the diaphragm of a receiving 
telephone. 

Various methods have been proposed for ob- 
taining telephonic records, but none of them 
have yet been introduced into actual commercial 
use. 



Recorder, Chemical, Bain's 



-An ap- 



paratus for recording the dots and dashes of 



Rec] 



441 



[Rec. 



a Morse telegraphic dispatch, on a sheet of 
chemically prepared paper. 

A fillet of paper soaked in some chemical sub- 
stance, such as ferro-cyanide of potassium, is 
moved at a uniform rate between the two ter- 
minals of the line, one of which is iron tipped, so 
that on the passage of the current, a blue dot, or a 
dash, will be made on the paper according to the 
length of time the current is passing. 

In order to insure a moist condition of the paper 
fillet, some deliquescent salt, like ammonium 
nitrate, is generally mixed with the ferro-cyanide 
of potassium. 




Fig. 467 . Bain Recorder. 

A Bain recorder is shown in Fig. 467. A, is 
a drum of brass, tinned on the outside. The 
paper fillet is drawn from the roll and kept 
pressed against the cylinder A, by a small wooden 
roller B. The needle, which is a metallic point, 
is placed in connection with one end of the line 
wire, and the brass drum is connected with the 
other end through the earth. Care must be ob- 
served to connect the needle point with the posi- 
tive electrode, as otherwise the paper will not be 
marked. (See Electrolysis.) 

The Bain recorder is now almost entirely re- 
placed by the Morse sounder. (See Sounder, 
Morse Telegraphic.) 

Recorder,' Morse An apparatus for 

automatically recording the dots and dashes 
of a Morse telegraphic dispatch, on a fillet of 
paper drawn under an indenting or marking 
point on a striking lever, connected with the 
armature of an electro-magnet. 

This apparatus is sometimes called a Morse 
register. 

The Morse recording or registering apparatus 
is shown in Fig. 468. 

The paper fillet passes between a pair of rollers 
r, driven by the clockwork W. The upper roller 
is provided with a groove, so that the movement 
of the stylus at the bent end of the lever L, by the 



electro-magnet M, moving its armature attached 
to the lever L, may indent or emboss the paper 
fillet. When no current is passing, the armature 
of the magnet and the lever L, are drawn back by 
the action of an adjustable spring at n. 
9 




Fig. 468. Morse Recorder. 

In the drawing, the ordinary Morse sounder is 
shown on the right. The sounder has almost 
entirely replaced the recording apparatus. 

Recorder, Siphon An apparatus 

for recording in ink on a sheet of paper, by 
means of a fine glass siphon supported on a 
fine wire, the message received over a cable. 

One end of the siphon dips in a vessel of ink. 
The record is received on a fillet of paper moved 
mechanically under the siphon. The ink is dis- 
charged from the siphon by electric charges im- 
parted to the ink by a static electric machine. 




Fig. 46 Q. The Siphon Recorder. 

In the annexed sketch of the siphon recorder, 
Fig. 469, a light rectangular coil b b, of very fine 
wire, is suspended by a thin wire f f, between the 
poles N, S, of a powerful compound permanent 
magnet, and moving on the vertical axis of the 
supporting wire f f, and adjustable as to tension, 
at h. A stationary soft iron core a, is magnetized 




SIPHON RECORDER 

Fig. 470. Record of Siphon Recorder. 

by induction and strengthens the magnetic field 
of N, S. The cable current is received by the 



Rec] 



442 



[Re?. 



coil b b, through the suspending wire f f, and is 
moved by it to the right or the left, according to 
its direction, to an extent that depends on the 
current strength. 

The fine glass siphon n, which dips into a 
reservoir of ink at m, is capable of movement on 
a vertical axis 1, and is moved backwards or for- 
wards, in one direction by a thread k, attached 

S E T T L ED' 
Fig. 4J i. Record of Siphon Recorder. 
to b, and in the opposite direction by a retractile 
spring attached to an arm of the axis 1. 

As the paper is moved under the point of the 
siphon, an irregular curved line is marked thereon. 

Two records as actually received by a siphon 
recorder are shown in the Figs. 470 and 471. 
Movements upwards correspond to the dots, and 
downwards to dashes. 

Rectification of Alcohol, Electric 

— (See Alcohol, Electric Rectification of.) 
Rectified.— Turned in one and the same 

direction. 
The " alternate currents in a dynamo-electric 

machine are rectified or caused to flow in one and 

the same direction by means of a commutator. 
The word commuted, generally used in this 

connection, would appear to be preferable to the 

word rectified. (See Commutator.) 

Rectilinear Co-ordinates, Abscissa of — — 

— (See Abscissa of Rectilinear Co-ordinates) 

Rectilinear Current.— (See Current, Rec- 
tilinear) 

Red Heat— (See Heat, Red) 

Red Hot— (See Hot, Red) 

Reducteur or Resistance for Yoltmeter. 
— A coil of known resistance as compared 
with the resistance of the coils of a voltmeter, 
and connected with them in series for the 
purpose of increasing the range of the instru- 
ment. (See Voltmeter) 

Reducteur or Shunt for Ammeter. — A 
shunt coil connected in multiple with the coils 
of an ammeter for the purpose of changing 
the value of the readings. 

The ratio of the resistance of the reducteur and 
the ammeter coils is known. A reducteur in- 
creases the range of current measured by the am- 
meter. 



Refining of Metals, Electric 



-The 



refining of metals by the application of elec- 
trolysis. 

When certain precautions are taken, metals 
thrown down from their solutions, are obtained in 
a chemically pure condition. This fact is utilized 
in the electrical refining of metals. If, for exam- 
ple, a plate of impure copper is to be refined 
electrolytically, it is used as the anode of a copper 
bath, and placed opposite a thin plate of pure cop- 
per forming the kathode. The passage of the 
current gradually dissolves the copper from the 
plate at the anode, and deposits it in a chemically 
pure condition on the plate at the kathode. 

Somewhat similar principles are employed for 
electrically refining other metals. 

Reflect — To throw off from a surface, ac- 
cording to the laws of reflection, as of waves 
in an elastic medium. (See Reflection, Laws 
of) 

Reflecting". — Throwing off from a surface,, 
according to the laws of reflection. (See 
Reflection, Laws of) 

Reflecting Galvanometer. — (See Gal- 
vanometer, Reflecting) 

Reflection. — The throwing back of a body 
or wave from a surface at an angle equal to- 
that at which it strikes such surface. (See 
Reflection, Laws of) 

Reflection, Laws of The laws gov- 
erning the reflection of light 

(1.) The angle of reflection, or the angle in- 
cluded between the reflected ray and the perpen- 
dicular to the reflecting surface at the point of 
incidence, is equal to the angle of incidence, or 
the angle included between the striking ray and 
the perpendicular to the reflecting surface at the 
point of incidence. 

(2.) The plane of the angle of incidence co- 
incides with the plane of the angle of reflection. 

Reflection of Electro-Magnetic Wares. 

— (See Waves, Electro-Magnetic, Reflection- 
of) 

Reflection of Induction. — (See Induc- 
tion, Reflection of) 

Reflector. — A plane or curved surface, 
capable of regularly reflecting light. 

Reflector, Parabolic A reflector, 



Ref.] 



443 



[Reg. 



or mirror, the reflecting surface of which is 
a paraboloid, or such a surface as would be 
obtained by the revolution of a parabola 
about its axis. 

A parabolic curve, which may be regarded as 
a section of a parabola, is shown in Fig. 472. 
A parabola has the following properties: If lines 
F P, F P, etc., be drawn from the point F, 
called the focus, to any point, P, P, etc., in the 
curve, and the lines Pp, Pp, Pp, etc., be then 
drawn severally parallel to the axis, V M, then 
1 all such angles, F P p, F P p, will be bisected by 
verticals to tangents at the point P, P, and P. 

Therefore, if a light be placed at the focus of a 
parabolic reflector, all the light reflected from the 
surface of the parabola will pass off sensibly par- 
allel to the axis V M. 

In Locomotive Head 'lights , a 
lamp is placed at the focus of 
a parabolic reflector, and the 
parallel beam so obtained is jp 
utilized for the illumination of 
the track. In a search light an v 
electric arc lamp is placed at 
the focus of a parabolic reflec- 
tor, or at the focus of a lens. 

A parabolic reflector is 
used for search lights, some- Fig. 472. Parabolic 
times in connection with an Reflector. 

arc lamp. A focusing arc lamp must be used for 
this purpose, so as to maintain the voltaic arc at 
the focus of the parabolic reflector, notwithstand- 
ing the unequal consumption of the positive and 
negative carbons. (See Arc, Voltaic.) 

Refract. — To change the direction of waves 
in any elastic medium in accordance with 
the laws of refraction. (See Refraction?) 

Refracting. — Changing the direction of 
waves in an elastic medium in accordance 
with the laws of refraction. 

Refraction. — The bending of a ray of 
sound, light, heat, or electro-magnetism at 
the surface of any medium whose density 
differs from that through which such ray 
was previously passing. 

Rays of sound, light, heat or electro-mag- 
netism are transmitted or propagated in straight 
lines as long as the density of the homogeneous 
medium through which they are passing under- 
goes no change. That is, as long as the medium 





P • 




V 


W 




V 


V 




K\\ P 


V 




(if p 


V 


M 




F 


P. 


n 




r 


\ P 


V 




M P 


V 




r ' 




w 





is homogeneous or isotropic. (See Medium, Iso- 
tropic.) As the rays enter the surface of a 
medium which differs in density from that through 
which they have been passing, they are bent or 
refracted at the surface of such a medium. 

This bending takes place towards a perpen- 
dicular to the refracting surface at the point of in- 
cidence, when the medium into which the rays are 
entering is of greater density than that they are 
leaving, and from the perpendicular when the 
medium they are entering is of less density than 
that they are leaving. 

The refraction or bending of the ray is caused 
by the difference in the velocity with which the 
waves are propagated through the two media. 

There is no refraction or deviation when the 
two rays enter the new medium at right angles 
to its surface, or when there is no angle of inci- 
dence. 

Refraction, Double • — The property 

possessed by certain substances of splitting 
up a ray of light passed through them into 
two separate rays, and thus doubly refracting 
the ray. 

Certain specimens of calc spar possess the prop- 
erty of double refraction. Each of the two rays 
into which the original ray is separated is polar- 
ized. Such calc spar is called doubly refracting 
calc spar. 

Refraction, Double, Electric The 

property of doubly refracting light acquired 
by some transparent substances while in an 
electrostatic or electro-magnetic field. 

Transient or momentary powers of double 
refraction, acquired by a transparent sub- 
stance while placed in an electric field. 

The intensity of double refraction is propor- 
tioned to the square of the electric force. 

The action of an electric field in endowing a 
substance with the power of double refraction 
while kept in such field, is due to the strain pro- 
duced by the electrostatic stress of the field. 

A similar transient power of double refraction 
is acquired by many bodies when subjected to 
the strain produced by a simple mechanical 
stress. 

Refreshing- Action of Current. — (See Ac- 
tion, Refreshing, of Current) 

Region, Extra-Polar A term ap- 
plied in electro-therapeutics to the region 



Beg.] 



444 



[Beg. 



which lies outside or beyond the therapeutic 
electrode. 

The term extra-polar region is used in contra- 
distinction to polar region. (See Region, Polar.') 

Region, Polar ■ —A term applied in 

electro-therapeutics to that region or part of 
the body which lies directly below the thera- 
peutic electrode. 

Register, Double-Pen Telegraphic 

— A telegraphic register provided with two 
separate styluses or pens for recording the 
telegraphic message on a fillet of paper. (See 
Register, Telegraphic?) 

Register, Morse A name sometimes 

given to a Morse recorder. (See Recorder, 
Morsel) 

Register, Telegraphic An appa- 
ratus employed at the receiving end of a tele- 
graphic line for the purpose of obtaining a 
permanent record of the telegraphic dispatch. 

The telegraphic register consists essentially of 
means whereby a fillet or tape of paper is drawn 
mechanically under a pen or stylus attached to 
the armature of an electro-magnet and moving 
therewith. 

The pen or stylus presses against the paper 
whenever the armature is attracted to the elec- 
tro-magnet, and is held there while the cur- 




Fig. 473 I nft ~ Writing Register. 
Tent is passing through the coils of the electro- 
magnet. By these means the dots and dashes of 
the telegraphic alphabet are recorded on the 
paper fillet as embossed or printed dots and 
dashes. The Morse register is an apparatus of 
this description. (See Recorder, Morse.} 

A form of ink-writing telegraphic register is 
shown in Fig. 473. It is self -starting. 



Register, Time, for Railroads A 

telegraphic recording apparatus or register 
designed to record all telegraphic messages 
transmitted over a line. 

The record is received on an endless band or 
fillet of paper. It is useful in case of disputes as 
to the time certain messages were sent over the 
line. 

Register, Watchman's Electric 

A device for permanently recording the time 
of a watchman's visit to each of the dif- 
ferent localities he is required to visit at stated 
intervals. 

These registers are of a variety of forms. They 
consist, however, in general, of a drum or disc of 
paper driven by clockwork, on which a mark is 
made by a stylus or pencil, operated on the clos- 
ing of a circuit by the pressing of a push button 
or the pressing of a key by the watchman at each 
station. 

Registering Apparatus, Electric 

(See Apparatus, Registering, Electric?) 

Registering Electrometer. — (See Elec- 
trometer, Registering?) 

Regulable, Automatically — Capa- 
ble of being automatically regulated. (See 
Regulation, Automatic?) 

Regulate, Automatically To regu- 
late in an automatic manner. (See Regula- 
tion, Automatic.) 

Regulation, Automatic Regulation 

automatically effected. 

Regulation, Automatic, of Dynamo-Elec- 
tric Machine Such a regulation of a 

dynamo-electric machine as will automati- 
cally preserve constant either the current or 
the potential difference. 

The automatic regulation of dynamo-electric 
machines may be accomplished in the following 
ways, viz.: 

(1.) By a Compound Winding of the Machine. 

This method is particularly applicable to con- 
stant-potential machines. By this winding, the 
magnetizing effect of the shunt coils is maintained 
approximately constant, while that of the series 
coils varies proportionally to the load on the ma- 
chine. 

The series coils are sometimes wound close to 



Reg.] 



445 



[Reg. 



the poles of the machine, and the shunt coils 
nearer the yoke of the magnets. Custom, how- 
ever, varies in this respect, and very generally 
the shunt coils are placed nearer the poles than 
the series coils. (See Machine, Dynamo- Electric , 
Compound- Wound.) 

(2,) By Shifting the Position of the Collecting 
Brushes. 

In the Thomson-Houston system of current 
regulation, the current is kept practically con- 
stant by the following devices: The collecting 
brushes are fixed to levers moved by the regula- 
tor magnet R, as shown in Fig. 474, the arma- 
ture of which is provided with an opening for the 
entrance of the paraboloidal pole piece A. A 
dash-pot is provided to prevent too sudden move- 
ment. 

When the current is normal, the coil of the 
regulator magnet is short-circuited by contact 
points at S T, which act as a shunt of very low re- 
sistance. These contact points are operated by 
the solenoid coils of the controller, traversed by 
the main current. The cores of this solenoid are 
suspended by a spring. When the current be- 
comes too strong, the contact point is opened, 
and the current, traversing the coil of the regu- 
lar magnet A, attracts its armature, which shifts 
the collecting brushes into a position in which a 
smaller current is taken off. 

A carbon shunt, r, of high resistance, is pro- 
vided to lessen the spark at the contact points S 
T, which occurs on opening the circuit. 






Fig. 47 4- Thomson-Houston Regulator. 

In operation the contact points are continually 
opening and closing, thus maintaining a practi- 
cally constant current in the external circuit. 

(3.) By the Aictomatic Variation of a Resist- 
ance shunting the field magnets of the machine, 
as in the Brush system. 

In Fig. 475 the variable resistance C, forms a 
part of the shunt circuit around the field mag- 
nets F M. This resistance is formed of a pile of 
carbon plates. On an increase of the current, 
such, for example, as would result from turning 
out some of the lamps, the electro-magnet B, 



placed in the main circuit, attracts its armature 
A, and, compressing the pile of carbon plates C, 
lowers their resistance, thus diverting a propor- 
tionally larger portion of the current from the 
field magnet coils F M, and maintaining the cur- 
rent practically constant. 

In some machines the same thing is done by 
hand, but this is objectionable, since it requires 
the presence of an attendant. 

(4.) By the Introduction of a Variable Resist- 
ance into the shunt circuit of the machine, as in 
the Edison and other systems. 




Fig. 475. The Brush Regulator. 

This resistance may be adjusted either auto- 
matically by an electro-magnet whose coils are 
in an independent shunt across the mains, or may 
be operated by hand. 

In Fig. 476, the variable resistance is shown 
at R, the lever switch being in this case operated 
by hand whenever the potential rises or falls be- 
low the proper value. 




Fig. 476. The Edison Regulator. 

The machine shown is thus enabled to main- 
tain a constant potential on the leads to which the 
lamps L, L, L, etc., are connected in multiple arc. 

(5.) Dynamometric Governing, in which a 
series dynamo is made to yield a constant cur- 
rent by governing the steam engine that drives 
it, by means of a dynamometric governor. This 
governor operates by maintaining a constant 
torque or turning moment, instead of by means of 



Reg.] 



446 



[Rel. 



the usual centrifugal governor which maintains a 
constant speed. 

(6.) Electric Governing of the Driving Engine, 
in which the governor is regulated by the cur- 
rent itself instead of by the speed of rotation, as 
usual. 

Regulation, Hand Such a regula- 
tion of a dynamo-electric machine as will pre- 
serve constant, either the current or the 
potential, said regulation being effected by 
hand as distinguished from automatic regu- 
lation. 

Regulator, Automatic — A device 

for securing automatic regulation as dis- 
tinguished from hand regulation. (See 
Regulation, Hand. Regulation, Automatic?) 

Regulator, Hand — — — A resistance 
box, the separate coils or resistances of which 
can be readily placed in or removed from a 
circuit by means of a hand-moved switch. 

The term hand regulator is used as distin- 
guished from automatic regulator. (See Regu- 
latory Automatic. Regulation, Automatic.) 

Regulator Magnet.— (See Magnet, Regu- 
lator.) 

Regulator, Monophotal Arc-Light 

— A term sometimes employed for an electric 
arc lamp in which the whole current passes 
through the arc-regulating mechanism, and 
which is usually operated singly in circuit 
with a dynamo. 

Regulator, Polyphotal Arc-Lamp 

A regulator for an arc lamp suitable for 
maintaining a number of lamps in series cir- 
cuit with the dynamo. 

Polyphotal regulators differ from monophotal 
regulators in that their regulating electro-mag- 
nets are energized by a shunt circuit around the 
electrodes of the lamp, while in monophotal regu- 
lators such electro -magnets are placed in the di- 
rect circuit. The terms monophotal and poly- 
photal are not generally used in America. 

Reguline Electro-Metallurgical Deposit. 

— (See Deposit, Electro-Metallurgical, Reg- 
uline?) 

Rejuvenation of Luminescence.— (See 

Luminescence, Rejuvenation of.) 



Relative Calibration. — (See Calibration^ 
Relative.) 

Relay. — An electro-magnet, employed in 
systems of telegraphy, provided with contact 
points placed on a delicately supported arma- 
ture, the movements of which throw a battery, 
called the local battery, into or out of the 
circuit of the receiving apparatus. 

A relay is sometimes called a receiving magnet* 




Fig- 477 ■ Telegraphic Relay. 

The use of a relay permits much smaller cur- 
rents to be used than could otherwise be done, 
since the electric impulses, on reaching a distant 
station, are required to do no other work than 
attracting a delicately poised movable contact, 
and thus, by throwing a local battery into the 
circuit of the receiving apparatus, to cause such 
local battery to perform the work of register- 
ing. Its use is especially required in the Morse 
system of telegraphy in order to cause the sounder 
to be distinctly heard. 

A form of relay that is much used is shown in 

Tig. 477- 

The electro-magnet M, is wound with many 
turns of very fine wire. In the form used by the 
Western Union Telegraph Company, there are 
about 8, 500 turns, having resistance of 150 ohms. 
A screw m, is provided for moving the electro- 
magnet M, a slight distance in or out, for the pur- 
poses of adjustment. A semi-cylindrical arma- 
ture A, of soft iron, is attached to the insulated 
armature lever a, the lower end of which is sup- 
ported by a steel arbor, which is pivoted between 
two set screws. 

A retractile spring S', regulable at S, is pro- 
vided for moving the armature away from the 
electro-magnet. There are four binding posts, 
two of which are placed in the circuit of the 
electro-magnet, and two in that of the local bat- 
tery. The ends of the line wire are connected 
with the former, and the receiving instrument 
placed in the circuit of the latter. A platinum 



Rel.] 



contact is placed on the end of a screw supported 
at F, opposite a similar contact, near the end a, 
of the armature iever, The contact is regulable 
by means of a screw c. 

On the energizing of the electro-magnet, the 
attraction of its armature closes the platinum 
contact, and, by thus completing the circuit of the 
local battery, causes an attraction of the armature 
of the receiving apparatus. On the cessation of 
the current in the main line, the spring S', pulls 
the armature away from the magnet, breaks the 
circuit of the local battery, and thus permits a 
similar spring on the receiving instrument to pull 
its armature away. Thus all the movements of 
the armature of the relay are reproduced with in- 
creased intensity by the armature of the receiving 
instrument. 

The connections of the relay to the local bat- 
tery and the registering apparatus, will be better 
understood from an inspection of Fig. 478, which 
represents a form of relay much used in Germany. 



447 [Rel. 

Relay, Differential A telegraphic 




Fig. 478. Telegraphic Relay, German Pattern. 

The retractile spring f, is regulated by the up- 
and-down movements of its lower support, which 
slides in the vertical pillar S. The line wire is 
shown at m m, connected at one end to earth by 
a ground wire. 

The registering apparatus R, is connected in 
the circuit of the local battery L, as shown. 
The contacts are made by the end B, of the lever 
B B' 5 attached to the armature A, of the electro- 
magnet M M. 

Relay Bell.— (See Bell, Relay, Electric^ 

Relay, Box-Sounding Telegraphic 

— A relay the magnet of which is surrounded 
by a resonant case of wood for the purpose 
of increasing the intensity of the sound made 
by the armature of the magnet. 

A form of box -sounding relay is shown m Fig. 
479- 




Fig. 479. Box-Sounding Relay 

relay containing two differentially wound coils 
of wire on its magnet cores. 

When the currents which pass through these 
two coils are of the same strength, there is no 
movement of the armature, since the fields of the 
two coils neutralize each other. 

The differential relay is used in the differential 
method of duplex and quadruplex telegraphy. 
(See Telegraphy, Duplex Differential Method of. 
Telegraphy, Quadruplex Differential Method of .) 

Relay Magnet. — A name sometimes given 
to a relay. (See Relay.) 

Relay, Microphone A device for 

automatically repeating a telephonic message 
over another wire. 




<./«<■ 




Fig. 480. Microphone Relay. 

A form of microphone relay is shown in Figs. 
480 and 481. 

Several minute microphones mounted on the 



ROM "-saisUMiTTER 




Fig. 481. Microphone Relay. 

diaphragm of the telephone whose message is to 
be repeated, so vary the resistance of a local bat- 
tery included in their circuit as to automatically 
repeat the articulate speech received. 

The microphones may De connected either in 



Rel.] 



448 



[ReL 



multiple arc or in series, as shown respectively to 
the left and right in Fig. 480. 

Relay, Pocket Telegraphic A form 

of telegraphic relay of such small dimensions 
as to permit it to be readily carried in the 
pocket. 

Relay, Polarized A telegraphic re- 
lay provided with a permanently magnetized 
armature in place of the soft iron armature of 
the ordinary instrument. 

In the form of polarized relay shown in Fig. 
482, N S, is a steel magnet, whose magnetism is 
consequently permanent, with its north and south 
poles at N, and S, respectively. The cores of 
the electro -magnet m, m', are of soft iron, and, 
since they rest on the north pole of the permanent 
steel magnet, the poles, brought very near to- 
gether by the armatures at n, n', will be of the 
same polarity as N, when no current is passing 
through the coils m, m' ; but when such current 
does pass, one of these poles becomes of stronger 
north polarity, while the other changes its polar- 
ity to south. 

By these means to-and fro movements of the 
armature lever, with its contact point, are effected 
without the use of a retractile spring ; movement 
in one direction occurring on the closing of the 
circuit due to the electro-magnetism developed 




Fig. 482. Polarized Relay. 

by the coils m, m', and movement in the opposite 
direction, on the losing of this magnetism on 
breaking the circuit, by the permanent magnet- 
ism of the steel magnet N S. 

These movements are imparted to the soft iron 
lever c, c', pivoted at B, and passing between the 
closely approached soft iron poles at n, n'. This 
lever rests at the end c', against a contact point 



when moved in one direction, and against an in- 
sulated point when moved in the opposite direc- 
tion. It rests against the insulated point when 
no current is passing through the coils m, m'. 

If the armature lever were placed in a position 
exactly midway between the poles n, and n', it 
would not move at all, being equally attracted by 
each; but if moved a little nearer one pole than 
the other, it would be attracted to, and rest 
against, the nearer pole. 

When alternating currents are employed on 
the line, the lever c, c', must be adjusted as nearly 
as possible in the middle of the space between n 
and n', in which case it will remain on the side to 
which it was last attracted, until a current in the 
opposite direction moves it to the other side. 

LB 




Fig. 483. A Detail of the Polarized Relay. 

The space between the magnet poles n, n',. 
and the contacts of the armature lever at D, and 
D', are shown in detail in Fig. 483, which is a 
plan of Fig. 482. The binding posts for the line 
battery are shown at L B, 1, and 2, and those 
for the local battery at A and B. The dotted 
lines show the connections. 

Since the polarized relay dispenses with the re- 
tractile spring, it is far more sensitive than the 
ordinary instrument. Once adjusted, no further 
regulation is required, in which respect it differs 
very decidedly from non-polarized relays. 

There are other forms of polarized relays, but 
the above will suffice to illustrate the general 
principle of their operation. 

Relay Shunt, Steam's (See Shunt,. 

Relay, Stearns?} 

Reluctance, Magnetic A term re- 
cently proposed in place of magnetic resist- 
ance to express the resistance offered by a 



RelJ 



449 



[Rep. 



medium to the passage through its mass of 
lines of magnetic force. 

The term reluctance, in the sense of resistance 
to passage of lines of magnetic force, has been 
proposed in place of resistance, for the purpose 
of carrying out the conception of regarding the 
flow of lines of force in a magnetic circuit as 
being due to a magneto-motive force, and being 
opposed by a reluctance of the substances form- 
ing such circuit to the passage of such lines. 

According to this conception, 

The magnetic flux = 

The magneto-motive force 
The reluctance. 

Reluctance, Magnetic, Unit of 

Such a magnetic reluctance in a closed cir- 
cuit that permits unit magnetic flux to 
traverse it under the action of unit magneto- 
motive force. 

In present practical work reluctances vary 
from 100,000 to 100,000,000 of the practical 
units. 

Reluctivity. — A term proposed for mag- 
netic reluctance. (See Reluctance, Mag- 
netic) 

This term is not generally adopted. 

Removable Key Switch. — (See Switch, 
Removable Key) 

Renovation of Secondary Cell. — (See 
Cell, Secondary or Storage, Renovatio7i of.) 

Renovation of Secondary or Storage 
Cell. — (See Cell, Secondary or Storage, 
Renovation of.) 

Reofore. — A rheophore. (See Rkeopkore.) 

Repeaters, Telegraphic Tele- 
graphic devices, whereby the relay, sounder 
or registering apparatus, on the opening and 
closing of another circuit, with which it is 
suitably connected, is caused to repeat the 
signals received. 

Repeaters are employed to establish direct 
communication between very distant stations, or 
to connect branch lines to the main line. 

Fig. 484, shows Wood's Button Repeater. This 
repeater consists simply of a three-point switch 
L, capable of being placed on the points 1, 2 and 
3 ; and a ground switch at 4. The circuits are 
arranged between the sounders S, S', relays 



M, M", main batteries B, B', and the two main 
lines E, and W, in the manner shown. 




Fig. 484. Wood's Button Repeater. 

If the lever L, is in the position shown in the 
drawing, the lines E and W, form independent 
circuits. 

If the ground switch 4 is closed, and the lever 
L, is placed on 2, 2, the eastern line repeats into 
the western. If the lever L, is placed on the 
plates 3, 3, the western line repeats into the 
eastern. 

This repeater is non-automatic and can be 
worked in but one direction at a time ; moreover, 
it requires the services of an attendant. 

The automatic repeater can be operated in both 
directions, and dispenses with the constant ser- 
vices of an attendant at the repeating station. 

In sending a dispatch through a repeater, the 
dots and dashes are prolonged so as to give the 
lever of the repeating instrument time in which 
to move backwards and forwards. 



,b „ c 



C K 




Fig. 485. Hick's Automatic Button Repeater. 

In Hick' 's Automatic Repeater, shown in Fig. 
485, the switch or circuit- changer is automatic in 
its action. 

The relay magnets are shown at M, M', the 
sounders at R and R' ; f, f, are platinum con- 
tacts operated by levers 1 and 1', and L and L', 
are extra local magnets, that act on armatures 



Rep.] 



450 



[Rep, 



placed directly opposite the armatures of the relay 
magnets. 

The extra local magnet L, is cut out of the 
circuit of B', the extra local battery, when the 
main circuit is broken, and the armature is in 
contact with c. As soon as this happens, how- 
ever, the spring s, drawing away the armature, 
and thus opening the short-circuit of no resist- 
ance between c and a, establishes a circuit 
through L. On a, coming in contact with c, the 
circuit is again broken. 

The tension of the spring s, is so regulated that 
a very rapid vibration of a, is maintained so con- 
stantly, that it is impossible to close the main cir- 
cuit when L, is not cut out. The armature a, 
will therefore respond to very weak impulses of 
the relay magnet. 

On breaking the western main circuit N, the 
lever a, vibrates very rapidly. The lever 1, of the 
sounder R, first breaks the circuit of L, and after- 
wards that of the eastern main circuit E, which 
passes through M. Both L' and M', being 
broken, a slight tension of s', will hold a, in 
place, thus avoiding the breaking of the western 
main circuit through the closing of the local cir- 
cuit through R. On the closing of the western 
circuit, the reverse of these operations occurs. 

The author has taken the above explanation 
mainly from Pope's work on " Modern Practice 
of the Electric Telegraph." 

Repeating Sounder.— (See Sounder, Re- 
peating?) 

Replenisher. — A static 
devised by Sir William 
Thomson for charging 
the quadrants of his 
quadrant electrometer. 

Two brass carriers C 
and D, shown in Fig. 486, 
are electrically fixed to the 
end of the vulcanite rod 
E, which is capable of ro- 
tation by the thumb screw 
at M, in the direction 
shown by the arrow. Hol- 
low metal half-cylinders, 
A and B, act as inductors, 
a strip of brass fixed around Fi S- 486.^ The Refilen- 
the edges of a piece of vul- 
canite P, connecting the metallic springs S, and 
S', as shown. 

The action of the replenisher is readily under- 



influence machine 




stood from the following considerations, as sug- 
gested by Ayrton in his "Practical Electricity " : 

A and B, Fig. 487, are two insulated hollow 
metallic vessels having a small difference of po- 
tential between them, A, being the higher. C, 
and D, are two small uncharged conductors held 
by insulating strings. If C and D, be held near 
A and B, as shown, the potential of C, will, by 
induction, be raised somewhat above that of D, 
so that when connected by a conductor, such as 
the metallic wire W, a small quantity of positive 
electricity will flow from C, to D, thus leaving D, 
positively, and C, negatively charged. 

If, now, C and D, are removed from W, and 
placed in the bottom of B and A, as shown in 
Fig. 488, the difference of potential between A, 
and B, will be thereby increased, and if they are 
then withdrawn, and totally discharged, and 




Fig. 487. Action of Replenisher. 

again placed in the first position shown, an ad- 
ditional charge can be given to A and B, and this 
can be repeated as often as desired. 

In the replenisher, A and B, correspond to the 
vessels A and B ; the brass carriers C and D, 
to the balls C and D, and the spring S S, and M, 




Fig. 488. Action 0/ Replenisher. 

to the wire W. No initial charge need be given 
to A and B, since they are invariably found to 



Rep.] 



451 



[Res. 



"be at a sufficient difference of potential to build 
up the charge. 
Replenisher, Carriers of The 

moving conductors of a replenisher which 
carry the charges and thus permit of an ac- 
cumulation of such charges. (See Re- 
plenisher.) 

Repulsion, Electric The mutual 

driving apart or tendency to mutually drive 
apart existing between two similarly charged 
bodies, or the mutual driving apart of similar 
electric charges. 

Repulsion, Electro-Dynamic The 

mutual repulsion between two electric circuits 
-whose currents are flowing in opposite direc- 
tions. 

Parallel currents flowing in opposite directions 
repel one another, because their lines of magnetic 
force have the same direction in adjoining parts of 
the circuit. (See Dynamics, Electro.') 

Repulsion, Electro-Magnetic The 

mutual repulsion produced by two similar 
electro-magnetic poles. 

Repulsion, Electrostatic —The 

mutual repulsion produced by two similar 
electric charges. 

Repulsion, Magnetic The mutual 

repulsion exerted between two similar mag- 
netic poles. 

Repulsion, Molecular The mutual 

repulsion existing between molecules arising 
from their kinetic energy. (See Matter, Ki- 
netic Theory of.) 

Residual Atmosphere — (See Atmosphere, 
Residual.) 

Residual Charge. — (See Charge, Resid- 
ual.) 

Residual Magnetism.— (See Magnetism, 
Residual) 

Resin. — A general term applied to a variety 
of dried juices of vegetable origin. 

Resins are, in general, transparent, inflamma- 
ble solids, soluble in alcohol, and, in general, 
excellent non-conductors of electricity. Rosin is 
one of the varieties of resin. 

Resinous Electricity.— (See Electricity, 
Resinous) 

Resistance. — Something placed in a circuit 
for the purpose of opposing the passage or 



flow of the current in the circuit or branches 
of the circuit in which it is placed. 

The electrical resistance of a conductor is 
that quality of the conductor in virtue of 
which there is a fixed numerical ratio be- 
tween the potential difference of the two 
opposing faces of a cubic unit of such con- 
ductor, and the quantity of electricity which 
traverses either face per second, assuming a 
steady flow to take place normal to these 
faces, and to be uniformly distributed over 
them, such flow taking place solely by an elec- 
tromotive force outside the volume considered. 

The term is used in the first definition in the 
concrete sense of something intended for or used 
as a resistance. For the physical definitions and 
facts see Resistance, Electric. 

Gases offer very high resistance to the flow of 
an electric current. Their non-conducting power 
causes the increase of resistance which attends 
the polarization of a voltaic cell. (See Cell, 
Voltaic, Polarization of.) 

Resistances consist of coils, strips, bars or 
spirals of metal, or plates of carbon, or metallic 
powders, powdered or granulated carbon, or 
liquids. 

Resistance, Absolute Unit of The 

one thousand millionth of an ohm. (See 
Ohm. Units, Practical) 

Resistance, Assymmetrical Con- 
ductors or parts of conductors, which offer a 
greater resistance to the flow of an electric 
current m one direction than in another. 

Assymmetrical conductors are unknown, so far 
as structural peculiarities are concerned, but can 
be obtained by the use of counter electromotive 
forces, acting as resistance. This term was pro- 
posed by Wilke in discussing the obtaining of 
continuous currents by commutatorless dynamo- 
electric machines. 

The resistance of the human body is possibly an 
assymmetrical resistance. 

An evident application of an assymmetrical re- 
sistance is to direct alternating currents so as to 
cause the current that passes to flow in and to the 
same direction. 

Resistance, Balanced A resistance 

so placed in a circuit as to be balanced or 
made equal to another resistance connected 
therewith. 



Ees.] 



452 



[Res. 



Resistance, Balanced, for Dynamos 

— A resistance that possesses a range suf- 
ficient to balance one dynamo against another 
with which it is desired to run in parallel. 
— ( Urqukart.) 

Resistance Box. — (See Box. Resistance^) 

Resistance Bridge — (See Bridge, Resist- 
ance.) 

Resistance Coil. — (See Coil. Resistance.) 

Resistance Coil, Standard — (See 

Coil, Resistance, Standard.) 

Resistance, Conductivity The re- 
sistance offered by a substance to electric 
conduction, or to the passage of electricity 
through its mass. 

Resistance, Dielectric — A term 

sometimes employed for the resistance of a 
dielectric to mechanical strains produced by 
electrification. 

The dielectric resistance of the glass, or other 
dielectric of a Leyden jar or condenser, is fre- 
quently overcome by the passage of the charges 
on the conducting surfaces, and the glass is thus 
pierced. 

The term dielectric resistance would appear 
to be badly chosen; for, like all substances, dielec- 
trics possess a true ohmic resistance, which in- 
creases with the increase of length, and decreases 
with the increase of area of cross-section. 

The resistance of the dielectric, however, differs 
from the ordinary ohmic resistance of conductors, 
in that the resistance of the dielectric is suddenly 
overcome, and the discharge passes disruptively 
as a spark. 

Resistance, Effect of Heat on Electric 

Nearly all metallic conductors have 

their electric resistance increased by an in- 
crease of temperature. 

The carbon conductor of an incandescent elec- 
tric lamp, on the contrary, has its resistance 
decreased when raised to electric incandescence. 
The decrease amounts to about three-eighths of its 
resistance when cold. 

The effects ol heat on electric resistance may be 
summarized as follows: 

(i.) The electric resistance ot metallic conduc- 
tors increases as the temperature rises. In some 
alloys this increase is smalL 

(2.) The electric resistance of electrolytes de- 
creases as the temperature rises. 



(3.) The electric resistance of dielectrics and 
non-conductors decreases as the temperature rises. 

RESISTANCE AND CONDUCTIVITY OF PURE 
COPPER AT DIFFERENT TEMPERATURES. 



11 
0[S 






§ 


3" 

•v 3 

2 % 

c 9* 




i 

0) 


1 

§ 


o° 


1. 00000 1 


OOOOO 


16 


1. 06168 


.94190 


I 


1. 0038 1 


99624 


17 


1.06563 


.93841 


2 


1.00756 


99250 


18 


1.06959 


■93494 


3 


1. 01 135 


98878 


19 


1-07356 


•93148 


4 


1. 01515 


98508 


20 


1.07742 


.92814 


5 


1. 01 896 


98139 


21 


1. 08164 


■62452 


6 


1 . 02280 


97771 


22 


1-08553 


.92121 


7 


1.02663 


97406 


23 


1.08954 


.91782 


8 


1 . 03048 


97042 


24 


1.09365 


•9 I 445 


9 


1-03435 


96679 


25 


1.09763 


.91110 


10 


1.03822 


96319 


26 


1.10161 


.90776 


11 


1. 04199 


9597° 


27 


1. 10567 


• 90443 


12 


1.04599 


950O3 


28 


1.11972 


.90113 


*3 


1.04990 


95247 


29 


1.11382 


.89784 


*4 


1.05406 


94 8 93 


30 


1.11782 


•89457 


15 


1-05774 


94541 









— {Latimer Clark.) 
Resistance, Electric — The ratio be- 
tween the electromotive force of a circuit 
and the current that passes therein. 

The reciprocal of electrical conductivity. 
Resistance can be defined as the reciprocal of 
electrical conductivity because even the best 
electrical conductors possess appreciable resist- 
ance. 

Ordinarily the resistance of a circuit may be 
conveniently regarded as that which opposes or 
resists the passage of the current. Strictly speak- 
ing, however, this is not true, since from Ohm'' s 
law (See Law of Ohm, or Law of Current 
Strength) 

E 
C = — , from which we obtain 
R 
E 
R = — , which shows that resistance is a 
C 
ratio between the electromotive force that causes 
the current and the current so produced. 

Resistance may be expressed as a velocity. 
The dimensions of resistance in terms of the 
electro-magnetic units are 



(See Units, Electro- Magnetic.) But these are the 
dimensions of a velocity, which is the ratio of the 
distance passed over in unit time. Resistance may 
therefore be expressed as a velocity. 



Res.] 



453 



[Res. 



"The resistance known as 'one ohm' is in- 
tended to be io 9 absolute electro-magnetic units, 
and, therefore, is represented by a velocity of io 9 
centimetres or 10,000,000 metres (one earth quad- 
rant) per second." — {Sylvanus Thompson.) 

Resistance may be represented by a velocity, 
one ohm being the resistance of a wire, which, 
if moved through a unit field of force at the rate 
of 1,000,000,000 (io9) centimetres per second will 
have a current of one ampere generated in it. 
(See Resistance, Ohmic. Resistance ', Spurious.) 

The true value of the ohm is exactly io 9 centi- 
metres. The material standards employed, i. e., 
the B. A. and "legal " ohms, are not absolutely 
of this value. 

One mil-foot of soft copper at 10.22 degrees C. 
or 50.4 degrees F. has the standard resistance of 
exactly 10 legal ohms ; at 15.56 or 59.9 degrees 
F., it has a resistance of 10.20 legal ohms, and 
at 23.9 degrees C. or 75 degrees F., 10.53 legal 
ohms. 

RESISTANCE. 

Resistance of Wires of Pure Annealed Copper at o" C. 

(Density = 8.9.) 



n 



5 

4<4 

3-9 

3-4 

3 

2.7 

2.4 



1.6 

1.5 

1.4 

i-3 



fee* 

D.— " 

« 2> 2 

Z a g 


gth in 
es per 
ramme. 
Wire.) 


M4> i 


CiMU 


| s o 


Le 

Me 
Kilo 
(Bar 


175 


5-7 


135.28 


7-4 


106.35 


9-5 


80.8 


12.5 


62.93 


16 


51 


19.8 


40.23 


25 


33-82 


29 


27-95 


36 


22.7 


44 


17.89 


56 


15.75 


63 


13-7 


73 


11. 8 4 


85 


10.06 


100 


8-47 


119 


6.99 


144 


5-66 


178 


4-47 


225 


2.83 


294 


2.52 


400 


1.74 


576 


1. 175 


902 


.808 


1251 


.7181 


1607 


.4026 


2508 


•2797 


3614 


.179 


559° 


.1007 


9929 


.0699 


H3 6 9 


.0447 


24570 


.0252 


39824 


• OII2 


88878 



Resistance of Wire of Pure An- 
nealed Copper at O degree C. 



Ohms 
per 

Kilogramme. 

.00456 
.00784 
.0128 
.0222 
•036S 
■0557 
.088 
.123 
.185 
.278 
.448 
•574 
•7 6 3 
1.03 
1.42 
2.02 
*-95 
4.19 
7.21 
12.3 
22.78 
46.81 
110.41 
222.55 
367.2 
895.36 
1.857.6 
4,489 
i4,i79 
29.549 
78,943 
227,515 
[142,405 



Ohms 


Metres 


per 


per 


Kilometre. 


Ohm. 


.8 


1230. s 


1.06 


944.38 


i-35 


722 


i.$o 


563.92 


2.3 


439 -°7 


2.8 


355-65 


3-6 


281 


4.2 


236.08 


5-i 


i95-'5 


6-3 


15-4.08 


8 


124.9 


9.1 


iog-75 


10.5 


95-65I 


12 


82.42 


14 


70.247 


17 


59.024 


20 


48.782 


25 


39-515 


32 


31-225 


42 , 


23-9 


57 


I7-56 


81 


12.305 


122.4 


8-173 


177.9 


5.622 


228.5 


4-377 


357 


2.801 


5'4 


1.945 


803.1 


1.245 


1428 


•7 


2056 


.486 


3213 


•3ii 


571.3 


•173 


12848 


.078 



The following table, based on Matthiessen's 
measurements, gives the relative resistances of 
equal lengths and cross-sections of a number of 
different substances used in electricity as com- 
pared with silver. 

LEGAL MICROHMS. 





Resistance in Microhms 






at degree C. 




Names of Metal. 






Relative 






Resistance. 




Cubic 
Centimetre. 


Cubic Inch. 




Silver, annealed... 


1.504 


0.5921 


1. 


Copper, annealed. 


1.598 


0.6292 


1.063 


Silver, hard drawn 


1.634 


0-6433 


1.0S6 


Copper, h'rd dr'wn 


1.634 


0.6433 


1.086 


Gold, annealed 


2.058 


0.8102 


1.369 


Gold, hard drawn. 


2.094 


0.8247 


1-393 


Aluminium, ann'ld 


2.912 


1. 147 


J-935 


Zinc, pressed 


5.626 


2.215 


3-741 


Platinum, annealed 


9.057 


3-565 


6.022 


Iron, annealed.. .. 


9.716 


3825 


6.460 


Nickel, annealed. . 


12.47 


4.907 


8.285 


Tin, pressed 


13.21 


5.202 


8.784 


Lead, pressed 


19.63 


7.728 


13-05 


German silver 


20.93 


8.240 


J 3-9 2 


Antimony, pressed 


35-50 


13.98 


23.60 


Mercury 


94-32 
131-2 


37-!5 
5i-65 


62.73 
87.23 


Bismuth, pressed. . 



— {Ayr ton.) 

The above resistances are for chemically pure 
substances only. Slight impurities produce a very 
considerable increase in the resistance. 

Resistance, Electric, of Liquids 



\Hospitalier.) 



The resistance offered by a liquid mass to 
the passage of an elec- + 
trie current. 

As a rule the electric re- 
sistances of liquids, with 
the single exception of mer- 
cury, are enormously high- 
er than those of metallic 
bodies. 

To roughly determine 
the resistance of a liquid, 
a section is taken between 
two parallel metallic plates 
A and B, Fig. 489, placed 
as shown in the figure, and 
an electric current is pass- 
ed between them. 

In order to accurately 
vary the size of the plates Fi £> 489. Resistance of 
immersed in the liquid, and Liquid. 

hence the area of cross-section of the liquid con- 
ductor, as well as the distance between the plates, 
the apparatus shown in Fig. 490 may be used, in 




Res.] 454 [Res. 

TABLE OF CONDUCTING POWERS AND RESISTANCES IN OHMS— B. A. UNITS. 



Names of Metals. 



Silver, annealed 

Silver, hard drawn 

Copper, annealed 

Copper, hard drawn 

Gold, annealed 

Gold, hard drawn 

Aluminium, annealed.... 

Zinc, pressed 

Platinum, annealed 

Iron, annealed 

Nickel, annealed 

Tin, pressed 

Lead, pressed 

Antimony, pressed 

Bismuth, pressed 

Mercury, liquid , 

Platinum - silver, alloy 

hard or annealed 

German silver, hard or 

annealed 

Gold, silver, alloy, hard 

or annealed 



Conducting 



Resistance of a 
r wire one foot 

P ° W g e reeC , lon » wei S hin S 



one grain. 



99-55 
77.96 



29.02 



16.81 
13. n 
12.36 
8.32 
4.62 
1.24 



0.2214 
0.2421 
0.2064 
0.2106 
0.5849 
0-5950 
0.06822 
0.5710 
3-536 
1.2425 
1.0785 
I-3I7 
3-236 
3-324 
•054 



18.740 
4- 2 43 
2.652 
2.391 



Resistance of a 
wire one metre- 
long weighing 
one gramme. 



0.1544 
0.1689 
0.1440 
0.1469 
o . 4080 
0.4150 
0.05759 

o-39 8 3 
2.464 
0.7522 
0.8666 
0.9184 
2.257 
2-3295 
3-525 
13-071 

2-959 

1.850 

1.668 



Resistance of a 

wire one foot 

long -n&o inch 

in diameter. 



9-936 
9-!5i 
9.718 
9.940 
12.52 
12.74 
17.72 
32.22 
55-09 
59-40 
75-78 
80.36 

"9-39 
216.0 
798.0 
600.0 

143-35 
127.32 

66.10 



Resistance of a 
wire one metre 
long, one milli- 
irietre in diam- 
eter. 



0.01937 

0.02103 

0.02057 

0.02104 

0.02650 

0.02697 

0.03751 

0.07244 

0.1166 

0.1251 

0.1604 

0.1701 

0.2527 

0-4571 

1.689 

1.270 

0.3140 

0.2695 

0.1399 



Approximate 
percentage of 
variation in re- 
sistance for 1 de- 
gree of tempera- 
ture dt 20 deg. 



0-377 

0.388 



o-355 
0.365 



0.365 
0.387 
0.389 

0-354 
0.072 

0.031 

0.044 
0.065 



which these distances are readily adjustable, as 
shown. 

Eesistance, Equivalent A single 

resistance which may replace a number of 
separate resistances in a circuit without alter- 
ing the value of the current traversing it. 

Resistance, Essential — A term 

sometimes used instead of internal resist- 
ance. 




Fig. 4Q0. 



Apparatus for Measuring Resistance of 
Liquid. 



Resistance, External Secondary 



term proposed by Du Bois Reymond for the 
change in the resistance of a circuit external to 
the electric source when cataphoric action 
takes place. (See Action, Cataphoric^ 

" If the copper electrodes of a constant battery 
be placed in a vessel filled with a solution of 
cupric sulphate and from each electrode there 
projects a cushion saturated with this fluid, then, 



— (Jenkin.) 
on placing a piece of muscle, cartilage, vegetable 
tissue, or even a prismatic strip of coagulated 
albumen across these cushions, we observe, that 
very soon after the circuit is closed, there is a 
considerable variation of the current. * * * 
This phenomenon is called ' external secondary 
resistance.' " — (Landois and Sterling.) 

Resistance, Extraordinary A term 

sometimes employed instead of external re- 
sistance. (See Resistance, External Secon- 
dary.) 

Resistance, False A resistance aris- 
ing from a counter electromotive force and 
not directly from the dimensions of the circuit, 
or from its specific resistance. 

The false resistance of any circuit is sometimes 
called its spurious resistance. (See Force, Electro- 
motive, Cottnter. Resistance, Spurious.) 

Resistance, Indue tionless A term 

sometimes used instead of non-inductive re- 
sistance. (See Resistance, No7i-Inductive?) 

Resistance, Inductive -A resistance 

which possesses self-induction. 

Resistance, Insulation — 



—The re- 
sistance of a line or conductor existing be- 
tween the line or conductor and the earth 
through the insulators, or between the two 



Res.] 



455 



[Bes. 



wires of a cable through the insulating 
material separating them. 

The insulation resistance of a telegraph line is 
the resistance that exists between the line and the 
earth, through its insulators. The insulation re- 
sistance will decrease as the length of line in- 
creases, since for any increase in the number of 
poles and insulators there is a proportional in- 
crease in the area of cross-section of the insula- 
ting supports. 

If the insulation resistance is 1,000,000 ohms 
per mile, in a line 200 miles in length, the insula- 
tion resistance is only 5,000 ohms, that is, 

1,000,000 

<* = t;,ooo ohms. 

200 J 

Resistance, Joint, of Parallel Circuits 

The joint resistance of two parallel 



circuits is determined by means of the follow- 
ing formula 



R = 



Where R = the joint resistance of any two cir- 
cuits whose separate resistances are respectively 
r and r'. 

When there are three resistances r, r' and r% 
in parallel, the joint resistance, 

r= ."';'. .. . 

rr -f rr -j-rr 
(See Circuits, Varieties of. ) 

Resistance, Magnetic The recipro- 
cal of magnetic permeability or conducti- 
bility for lines of magnetic force. 

Resistance offered by a medium to the 
passage of the lines of magnetic force through 
it. 

The magnetic resistance of the circuit of the 
lines of force is reduced by forming the circuit of 
a medium having a high magnetic permeability, 
such as soft iron. This is accomplished by the 
armature or keeper of a magnet, or by the iron in 
an iron-clad magnet. (See Magnet, Iron-Clad.) 

Resistance, Measurement of - 

Methods employed for determining the re- 
sistance of any circuit or part of a circuit. 

Numerous methods are employed for this pur- 
pose. Among these are : 

(1.) The use of a resistance box with a Wheat - 
stone bridge, by opposing or balancing the un- 
known resistance against a known resistance. 
(See Balance, Wheat st one' s Electric.) 



(2.) The differential galvanometer. (See Gal- 
vanometer, Differential.) 

(3.) The method of substitution. 

(4.) Comparison of the defections of a gal- 
vanometer. 

Method of Substitution. — A resistance-box R, 
Fig. 491, galvanometer G, and the resistance x, 
that is to be measured, are placed in the direct 
circuit of the battery B, by means of conductors 
of such thick wire that their resistance can be 
neglected. 

The deflection of the galvanometer is first 
measured with x, in circuit, and no resistance in 
the box R. The resistance x, is then cut out of 
the circuit by placing a thick copper wire across 
the terminals of the mercury cups at mm', and 
resistances unplugged in R, until the same deflec- 
tion is obtained. Then, if the electromotive force 
of the battery has remained constant, the resist- 
ances unplugged equal the unknown resistance. 

For full description of the various methods of 
determining resistance the reader is referred to 
'• ' Ayr ton's Practical Electricity , * ' " Kempe's 
Handbook of Testing," or other standard books 
on electrical measurements. 



ft 



"m m J 



U o o o 
o o o o 



T> 



L-j.Jt 

B 

Fig. 4QT. Substitution Method. 

When several resistances are placed in series in, 
any circuit, by measuring the difference of poten- 
tial at their terminals, their values can be deter- 
mined by simple calculation, being directly pro- 
portional to these differences of potential. 

This method is especially applicable to the 
measurement of such low resistances as the arma- 
tures of dynamo-electric machines. 



— Resistance, Non-inductive 



-A re- 



sistance in which self-induction is practically 
absent. 

An incandescent lamp filament is practically a 
non-inductive resistance when compared with a 
coil on the helix of an electro-magnet. 

Resistance of Human Body. — (See Body, 
Human, Resistance of.) 



Res.] 



456 



Eesistance of Toltaic Arc— (See Arc, 
Voltaic, Resistance of.) 

Resistance, Ohmic The true resist- 
ance of a conductor due to its dimensions 
and specific conducting power, as distin- 
guished from the spurious resistance produced 
by a counter electromotive force. (See Force, 
Electromotive, Counter. Resistance, Spuri- 
ous^) 

The term ohmic resistance must be regarded as 
a pleonasm. Its use can only be permitted in 
contradistinction to counter electromotive force 
resistance. True and spurious resistance would 
seem preferable. 

Resistance or Cell, Selenium A 

mass of crystalline selenium, the resistance of 
which is reduced by placing it in the form of 
narrow strips between the edges of broad 
conducting plates of brass. 

The selenium employed for this purpose is the 
vitreous variety which has been fused and main- 
tained for several hours at about 220 degrees C, 
by means of which its resistance is reduced. 

By exposure to sunlight, the resistance of a 
selenium cell is decreased fully one-half its re- 
sistance in the dark. The selenium cell is used 
in the photophone. (See Photophone.) 

Resistance or Reducteur for Yoltmeter. 

— (See Reducteur or Resistance for Volt- 
meter^ 

Resistance, Secondary —A term 

sometimes used in place of external secon- 
dary resistance. (See Resistance, External 
Secondary?) 

Resistance Slide. — (See Slide, Resist- 
ance) 

Resistance, Specific The particular 

resistance which a substance offers to the 
passage of electricity through it. 

In absolute measure, the resistance in ab- 
solute units between the opposite faces of a 
centimetre cube of the given substance. 

In the practical system the resistance given 
in ohms. 

Resistance, Specific Conduction 

A term sometimes used instead of specific 
resistance. (See Resistance, Specific) 



[Res. 

Resistance, Specific, of Liquids 

The resistance of a given length (one centi- 
metre) and area of cross-section (one square 
centimetre) of any liquid as compared with 
the resistance of an equal length and cross- 
section of pure silver. 

The resistance of a few common liquids and so- 
lutions is here given from Lupton: 

Water, pure, at 75 degrees C. . 1.188 X io 8 ohms, 
i. e., 118,800,000. 

Water at 4 degrees C .... 9. 100 X io 6 " 

Water at 11 degrees C 3.400 X io 5 " 

Dilute hydrogen sulphate (sul- 
phuric acid) at 18 degrees 
C, 5 per cent, acid 4.88 

Dilute hydrogen sulphate at 
18 degrees C, 3 per cent, 
acid 1.38 ohms. 

Nitric acid at 18 degrees C, 

density 1.32 1.61 " 

Saturated solution of copper 
sulphate (blue vitriol) at 10 
degrees C 29.30 " 

Saturated solution of zinc sul- 
phate at 14 degrees C 21.50 " 

Hydrochloric acid, 20 per cent. 

acid, at 18 degrees C 1.34 " 

Sal ammoniac, 25 percent, salt 2.53 " 

Common salt, saturated, at 13 

degrees C 5.30 " 

It will be observed that the resistance varies 
considerably with differences of temperature. 

Resistance, Spurious A false re- 
sistance arising from the development of a 
counter electromotive force. (See Resist- 
ance, False. Force, Electromotive, Cowi- 
ter.) 

The spurious resistance is also called the false 
resistance, in order to distinguish it from the true 
or ohmic resistance. (See Resistance, Electric.) 

Resistance, Standard A resistance 

used for comparison with or the determina- 
tion of unknown resistances. 

A committee appointed by the American Insti- 
tute of Electrical Engineers in 1890 reported the 
following values for the standard resistance of 
copper wire; at O degree C. in B. A. U. and legal 
ohms, viz.: 



Res.] 



457 



[Res. 



Standard Resistance at o° C. 

B. A. U. Legal Ohms. 



• ■ Meter-millimetre, ' : 
"soft copper "... 
Cubic centimetre. . . 
" Mil-foot " 9.720 

Resistance, Tables of 



.02057 .02034 

.000001616 .000001598 
9.612 

- — Tables in 



which the resistance of equal lengths and 
cross-sections of different substances is 
given in ohms, or other units of resistance. 

Resistance Thermometer. — (See Ther- 
mometer, Electric Resista?ice.) 

Resistance, Transition — A term 

sometimes used in electro-therapeutics for a 
change in the value of the resistance caused 
by polarization. 

Whenever an electric current passes through 
a fluid substance and decomposes the fluid, the 
decomposition products collect on the electrodes 
and produce an increase in the resistance of the 
circuit. 

Resistance, Trne The resistance 

which a conductor offers to the passage of a 
current by reason of its dimensions and spe- 
cific conducting power, as distinguished from 
a spurious resistance produced by a counter 
electromotive force. 

The true resistance is sometimes called the 
ohmic resistance. — (See Resistance, Spurious. 
Resistance, Ohmic.) 

Resistance, Unit of Such a resist- 
ance that unit difference of potential is re- 
quired to cause a current of unit strength 
to pass. (See Ohm. Potential, Electric. 
Potential, Difference of.) 

Resistance, Unit of, Absolute The 

one thousand millionth of an ohm. (See 
Oh?n. Units, Practical) 

Resistance, Unit of, Jacobi's The 

electric resistance of 25 feet of a certain 
copper wire weighing 345 grains. 

Another unit of electric resistance proposed 
by Jacobi was the resistance of a copper wire 
one metre in length and one millimetre in diame- 
ter. 

Resistance, Unit of, Mattliiessen's 

— The resistance of one statute mile of pure 
annealed copper wire tV m ch in diameter at 



15.5 degrees C, and determined by him to be 
13.59 B. A. ohms. 
Resistance, Unit of, Varley's The 

resistance of one statute mile of a special 
copper wire ^ inch in diameter. 

Varley's unit was afterwards adjusted by him 
to equal 25 Siemens Mercury Units. 

Resistance, Variable A resistance 

the value of which can be readily varied, 
Variable resistances are either : 
(1.) Automatically variable resistances; or 
(2.) Non-automatically variable resistances. 

Resistance, Variable, Automatic 

A resistance the value of which can be auto- 
matically varied. 

A pile of carbon plates resting on one another, 
in loose contact, offers a high resistance, but when 
compressed as by an electro-magnet their resist- 
ance is lowered. Brush employs such an auto- 
matic resistance in the regulation of his dynamo- 
electric machine. (See Regulation, Automatic.) 

Resistance, Variable Non-Automatic 

— A resistance the value of which is regulated 
by hand. (See Rheostat.) 

Resistance, Virtual A term some- 
times employed instead of impedance. (See 
Impedance) 

Resonance, Electric The setting 

up of electric pulses in open-circuited con- 
ductors, by the action of pulses in neighboring 
conductors. 

Electric resonance, like acoustic resonance, 
takes place when a correspondence exists between 
the time-rate of vibration of the body producing 
the resonance, and the body in which the reso- 
nance is produced. In other words, when the 
wave lengths are the same in the two bodies, or 
when the wave length in one is equal to a half 
wave length, or some definite multiple of a half 
wave length of the other. 

Partial resonance may occur, when there is a 
small difference between the wave lengths of the 
two bodies. Beyond certain limits, however, this 
is so small as to be practically absent. 

When an electrical pulse is started in a con- 
ductor by the discharge of a Ley den jar, a side flash 
spark is obtained in the alternative path, between 
the discharge points. The length of this spark has 
its greatest value, when the time required for the 



Res.] 



458 



[Kes, 



pulse to travel backwards and forwards along the 
conducting wires, is exactly equal to the time of 
a complete oscillation in the circuit, or when the 
length of the open-circuit wires is equal to half a 
wave length, or some multiple of half a wave 
length. 

The fact that the length of the spark is greatest 
when certain relations exist between the dimen- 
sions of the two circuits, shows that the time-rate 
of an electrical pulse in any circuit depends on 
the dimensions of that circuit. 

In the case of acoustic resonance, in order that 
one tuning fork may be able to excite vibrations in 
another, the fork producing or exciting the vibra- 
tion must be strictly in unison with the fork in 
which the vibrations are excited, and any varia- 
tions produced in the rate of vibration of the 
sounding fork, by overloading it, or, in other 
words, by altering its dimensions, checks the 
effects of its resonance. 

In a similar manner, any alterations in the di- 
mensions of the circuit, checks or diminishes the 
effects of electric reson- 
ance in a neighboring cir- 
cuit, which was previously 
in unison with it. This 
has been experimentally 
shown by Hertz as fol- 
lows: 

An induction coil A, 
Fig. 492, has the terminals 
of its secondary connected 
to an open rectangular cir- 
cuit provided with spark- 
ing terminals, I, and 2, 
called a spark micrometer. 
Under certain conditions, 
when the discharge oc- 
curs at the terminals B, 
of the ordinary discharger, sparks are produced 
by electric resonance in the electric resonator 
formed by the spark micrometer at M. 

Supposing, now, that a certain character of spark 
is obtained at the terminals B, that is, a cei_ 
tain velocity of electrical pulsations is obtained 
which depends on the nature of the spark; sup- 
pose, moreover, that the dimensions of the spark 
micrometer or electric resonator are such that the 
greatest length of spark is obtained. Then, any 
alteration in the character of these sparks, be- 
tween the terminals at B, varies the intensity of 
the sparks in the spark micrometer. 

If, for example, the apparatus be arranged 




Fig. 4Q2. Electrical 
Resonance. 



as shown in Fig. 493, in which one of the sec- 
ondary terminals of the induction coil has con- 
nected with it a copper wire i g h. The sparks at 
M, decrease considerably. When, however, the 
conductor C, is connected with the free end H, 
of this additional conductor, then this effect is 
not observed, as is shown by the fafct that when 
the conductor C, is attached at the point G, it 
produces no effect on it. 



oczizzx) 



■cc 



X> 



M 

£< " • ' 6> 

Fig. 493- Electric Resonance. 



In another experiment with the same apparatus, 
matters may be arranged that the sparks in the 
micrometer circuit pass singly. When, now, an- 
other conductor C, is attached to K, a stream of 
sparks immediately passes. 

It would appear, therefore, from the above ex- 
periments, that when two circuits are taken, 
having as nearly as possible the same vibration 
periods, any alteration in the dimensions of either 
will prevent one from producing electrical reso- 
nance in the other. 

In the above experiments Hertz demonstrated 
the following facts, viz., 

(1.) The sparks in the micrometer circuit are 
smaller when the discharges take place between 
points, or a point and a plate, instead of between 
knobs. 

(2.) The micrometer sparks are feebler in rare- 
fied gas than in air at ordinary pressures. 

(3.) Extremely slight differences in the nature 
of secondary sparks produce considerable differ- 
ence in the length of the micrometer sparks. 

Hertz found the above results were obtained 
when the secondary sparks were of a brilliant 
color, and were attended by a sharp crack. 

(4.) The length of the spark in the micrometer 



Res.] 



459 



[Ret. 



circuit varies with the length of the micrometer 
circuit. 

This, of course, follows from the fact that any 
alteration of the length in the micrometer circuit, 
produces, by electrical retardation, a correspond- 
ing alteration in the time of the electrical pulses. 

(5.) No effect is produced in the length of the 
micrometer spark by variations in the material, 
the resistance, or the diameter of the wire forming 
the micrometer circuit. 

This is probably because the rate of propaga- 
tion of electrical pulses along a conductor, de- 
pends mainly on the capacity of the conductor, 
and on its co-efficient of self-induction, and only 
to a slight extent on its resistance. 

(6.) The length of wire connecting the microm- 
eter circuit with the secondary circuit has but 
little effect, provided such length does not exceed 
a few metres. 

Local disturbances, therefore, must traverse 
conductors without undergoing any appreciable 
change. 

(7.) The position of the point on the micrometer 
circuit connected with the secondary circuit, is of 
the greatest importance. 

When the point on the micrometer circuit is 
situated symmetrically with respect to the two mi- 
crometer knobs, variations of potential will reach 
the terminals in the same phase, and there will be 
but little effect, as seen by the sparks between the 
micrometer knobs. Such a point on the microm j 
eter knobs is called the null point, or it is called as 
in a corresponding case in acoustics, a nodal point. 
(See Point, Null. Point, Nodal, ) 

(8.) When the conductors r.'e of sufficient 
length, their approach produces disturbances in 
a previously adjusted and quiet spark microm- 
eter, just as the approach of a conductor would. 

Probably one of the most curious effects con- 
nected with the phenomena of electrical resonance 
is that pointed out by Lodge, viz. : that when the 
spark from a secondary circuit is so placed that 
the light is visible from a micrometer circuit, the 
effects of the discharge are greatly increased. 
Lodge also found that the light from burning 
magnesium wire, or, in general, light rich in the 
ultra-violet rays, produces the same effect. 

Resonator, Electric An apparatus 

employed by Hertz in his investigations on 
electric resonance. (See Resonance, Elec- 
tric.) 

An electric resonator consists essentially of an 



open- circuited conductor, or circuit of such dimen- 
sions that electro-magnetic waves or pulses are 
propagated through it at the same rate as those 
which are occurring in a neighboring circuit 
from which electro-magnetic radiation is tak- 
ing place. Under these circumstances electro- 
magnetic pulses are set up sympathetically by 
resonance in the open circuit of the resonator, like 
the sympathetic vibrations in a tuning fork, when, 
placed near another vibrating tuning fork, which 
is giving off sound waves of exactly the same- 
period of vibration as its own. 

Resonator, Electro-Magnetic — A 

term applied to the Hertz spark micrometer, 
in which electro-magnetic waves are produced 
by electric resonance. (See Resonance, Elec- 
tric?) 

Resultant. — In mechanics, a single force 
that represents in direction and intensity the 
effects of two or more separate forces. 

The separate forces are called the components. 
(See Components.} 

Retardation.— A decrease in the speed of 
telegraphic signaling caused either by the 
induction of the line conductor on itself, or 
by mutual induction between it and neighbor- 
ing conductors, or by condenser action, or by 
all. 

The line must receive a certain charge before- 
a current sent into it at one end can produce a 
signal at the other end. This charge will de- 
pend on the length and surface of the wire, on the 
neighborhood of the wire to the earth or other- 
wires, and on the nature of the insulating mate- 
rial between the wire and neighboring conductors.. 
This results in a charge given to the wire which 
is lost as a current for signaling. The greater the 
electrostatic capacity of the line wire, the greater 
will be the retardation in signaling. (See Capa- 
city ^ Specific Inductive. Dielectric. Capacity, 
Electrostatic. Induction, Electro-Dynamic.) 

Retardation in signaling is produced by the 
following causes : 

' (1.) Self-induction which produces extra cur- 
rents. (See Induction, Self. Currents, Extra.)- 

The extra current on making, retards the be- 
ginning of the signal ; the extra current on break- 
ing, retards its stopping. 

(2.) Mutual Induction between the line con- 
ductor and neighboring conductors. 



Ret] 



460 



[Rhe, 



(3.) The Magnetic Inertia or Lag, or the time 
required to magnetize or demagnetize the core of 
the electro-magnetic receptive devices used on 
the line. 

(4.) By Condenser Action, the cable acting as a 
condenser. 

Retardation, Electric A retarda- 
tion in the starting or stopping of an electric 
current, arising from self-induction. (See In- 
duction, Self. Retardation) 

Retardation, Inductive A retarda- 
tion in the appearance of a signal at the dis- 
tant end of a cable, produced by the action of 
induction. (See Retardation.) 

Retardation, Magnetic A retarda- 
tion in the magnetization or demagnetization 
of a substance due to magnetic lag. (See 
Retardatio?i. Lag, Magnetic?) 

Retarding, Electrically Decreas- 
ing the speed of telegraphic signaling, by 
means of induction. (See Retardation) 



-A term pro- 



Retentivity, Magnetic — 

posed by Lamont in place of coercive force, 
or the power possessed by a magnetizable 
substance of resisting magnetization or de- 
magnetization. (See Force, Coercive) 

Return Circuit. — (See Circuit, Return) 

Return, Earth (See Earth Re- 
turn) 

Return Ground. — (See Ground-Return) 

Return Wire or Conductor. — (See Wire, 
Return) 

Returns. — In a system of distribution, those 
conductors through which the current flows 
back from the electro-receptive devices to 
the source. (See Leads) 

The word returns is sometimes used in a sys- 
tem of distribution by parallel circuits, to distin- 
guish between the conductor by which the cur- 
rent goes back or returns from the receptive de- 
vices to the dynamo, and the conductor that leads 
it to the receptive devices. The term leads is, 
however, often applied to both conductors. 

Reverse-Induced Current. — (See Current, 

Reverse-Induced) 



Reversed Currents. — (See Currents, Re- 
versed) 

Reverser, Current A switch, or 

other apparatus, designed to reverse the di- 
rection of a current. 

Reversible Bridge. — (See Bridge, Rever- 
sible) 

Reversible Heat— (See Heat, Reversible) 

Reversibility of Dynamo.— The ability 
of a dynamo to operate as a motor when tra- 
versed by an electric current. (See Motor, 
Electric) 

Reversing Gear of Electric Motor.— (See 
Motor, Electric, Reversing Gear of) 

Reversing Key. — (See Key, Reversing) 

Reversing Key of Quadruplex Tele- 
graphic System. — (See Key, Reversing, of 
Quadruplex Telegraphic System) 

Reversing Magnetic Field. — (See Field, 
Mag7ietic, Reversing) 

Rheochord. — A word formerly employed 
instead of rheostat. (See Rheostat) 

Rheometer. — A word formerly employed 
for any device for measuring the strength of 
a current. 

This word is now obsolete and is replaced by 
the word galvanometer. (See Galvanometer.) 

Rheomotor. — A word formerly employed 
to designate any electric source. 

This word is now obsolete, and replaced by 
the various names of the different electric sources. 
(See Source, Electric.) 

Rheophore. — A word formerly employed to 
indicate a portion of a circuit conveying a cur- 
rent and capable of deflecting a magnetic 
needle placed near it. (Obsolete.) 

Rheoscope. — A word formerly employed in 
place of the present word galvanoscope, for 
an instrument intended to show the presence 
of a current, or its direction, but not to 
measure its strength. (Obsolete.) 

Rheoscope, Physiological A sensi- 
tive nerve-muscle preparation employed to 
determine the presence of an electric current. 
(See Frog, Galvanoscope) 



Ehe.] 



461 



[Rill, 



A term sometimes applied m electro-thera- 
peutics to the frog's legs preparation adapted 
to show the presence of any electric current. 

The physiological rheoscope is adapted to 
show the presence of an electric current without 
the use of a galvanometer. On the passage of 
the electric current the frog's legs twitch con- 
vulsively. 

Rheostat. — An adjustable resistance. 

A rheostat enables the current to be brought 
to a standard, i. e., to a fixed value, by adjusting 
the resistance; hence the name. 

The term rheostat is applied generally to a 
readily variable resistance, the varying values of 
which are known. 

Rheostat, Dynamo-Balancing — 



—An 

adjustable resistance whose range is sufficient 
to balance the current of one dynamo against 
another with which it is required to run in 
parallel. 

Rheostat, Water A rheostat the 

resistance of which is obtained by means of a 
mass of water of fixed dimensions. (See 
Rheostat^ 

Rheostat, Wheatstone's A form of 

apparatus sometimes employed for an adjust- 
able resistance. 

This apparatus is very seldom employed in 
accurate work. 

The parallel cylinders A and B, Fig. 494, are 
formed respectively of conducting and non-con- 
ducting materials, the bare wire on which can be 
wound from either 
cylinder to the other. 
When introduced into 
a circuit, only the re- 
sistance of that part 
of the wire that is on 
B, is introduced into 
the circuit, since the 
bare wire on A, is 
short-circuited by the 
metallic cylinder. 
This rheostat is not 




Fig. 4Q4. Wheatstone's 
Rheostat. 



very suitable for accurate measurements, owing 
to the difficulty of invariably obtaining reliable 
contacts. 

Rheostatic Machine. — (See Machine, 
Rheostatic.) 



Rheotome. — A word formerly employed 
for any device by means of which a circuit 
could be periodically interrupted. 

This word is now obsolete, and is replaced by 
interrupter. (See Interrupter.) 

Rheotrope. — A word formerly employed 
for any device by which the current could 
be reversed. 

This word is now obsolete and replaced by 
commutator or current reverser. (See Reverser, 
Current.) 

Rhigolene. — A highly volatile hydro-car- 
bon obtained during the distillation of coal 
oil, and employed in the flashing treatment of 
carbons for incandescent lamps. (See Car- 
bons, Flashing Process for.) 

Rhumbs of Compass. — (See Compass, 
Rhumbs of.) 

Ribbed Armature Core. — (See Core, 
Armature, Ribbed.) 

Ribbon Copper. — (See Copper, Ribbon) 

Right-Handed Solenoid. — (See Solenoid, 
Right -Handed.) 

Right-Hand Trolley Frog.— (See Frog, 
Trolley, Right- Hand) 

Rigidity, Molecular — Resistance 

offered by the molecules of a substance to 
rotation or displacement. 

The molecular rigidity of a magnetizable sub- 
stance was until recently considered to be the 
cause of the differences of coercive force or mag- 
netic retentivity possessed by different substances. 
The general acceptance of Ewing's theory of 
magnetism has, of course, caused the above view 
to be considerably modified. (See Magnetism, 
Ewing's Theory of. Force, Coercive. Retentiv- 
ity, Magnetic.) 

Ring, Ampere The turn or turns 

of wire used in electric balances for the meas- 
urement of electric current. 

Ring Armature. — (See Armature, Ring) 

Ring Armature Core.— (See Core, Ar?na- 
ture, of Dynamo-Electric Machine) 

Rings, Electric A term sometimes 

used instead of Nobili's rings. (See Metal- 
lochromes) 



Rin.] 



462 



[Rod. 



Rings, Electro-Chromic A term 

sometimes applied to metallochromes. (See 
Metallochromes) 

Rings, Nobili's A term sometimes 

used for metallochromes. (See Metallo- 
chromes?) 

Roaring of Arc, — (See Arc, Roaring of.) 

Rocker Arm. — (See Arm, Rocker) 

Rocker, Brush In a dynamo-elec- 
tric machine or electric motor, any device for 
shifting the position of the brushes on the 
cummutator cylinder. 

Rocker, Multiple-Pair Brush A 

term sometimes used for multiple-pair brush 
yoke. (See Yoke, Multiple-Pair Brush) 

Rocker, Single-Brush A device 

by means of which a single pair of brushes 
are so supported on a dynamo-electric ma- 
chine or electric motor, as to be capable 
of being readily shifted into the desired 
position on the commutator cylinder. 

Rocker, Single-Pair Brush — A 

term sometimes used for single-pair brush 
yoke. (See Yoke, Single-Pair Brush) 

Rod Clamp. — (See Clamp, Rod) 

Rod, Clutch A clutch or clamp pro- 
vided in an arc lamp to seize the lamp rod and 
thus arrest its fall, during feeding, beyond a 
certain predetermined point. 

The clutch or clamp is caused to release or hold 
the lamp rod by the action of an electro-magnet 
placed in a shunt circuit around the electrodes. 
(See Lamp, Arc, Electric.) 

Rod, Discharging A jointed rod 

provided at both ends 
with balls and con- 
nected at the middle by 
a swinging joint which 
permits the balls to 
move towards or from 
one another, employed 
for the disruptive dis- 
charge of Leyden bat- 
teries or condensers. 

/c n- 7 r> • Ft S'495> Discharging 

(See Discharge, Dzs- Rod ^ 

ruptive. Jar, Leyden) 
The insulated handles H, H, Fig. 495, permit 




the balls at M, M, to be readily applied to the 
opposite coatings of the jar or condenser. 

The name discharging tongs is sometimes ap- 
plied to this apparatus. 

Rod, Lamp A metallic rod pro- 
vided in electric arc lamps for holding the 
carbon electrodes. 

When the upper carbon only is fed, as is the 
case in most arc lamps, there is usually but one 
lamp rod provided. The clutch or clamp of the 
feeding device acts against this rod, which must 
of necessity be at least as long as the upper carbon. 
(See Lamp, Arc, Electric.) 

Rod, Lightning — A rod, or wire 

cable of good conducting material, placed on 
the outside of a house or other structure, in 
order to protect it from the effects of a light- 
ning discharge. 

Lightning rods were invented by Franklin. 
The results of a very extended inquiry on the 
subject, leave no room for doubt that a lightning 
rod, properly placed and constructed, affords an 
efficient protection to the buildings on which 
it is placed. 

To insure this protection, however, the fol- 
lowing conditions were, until very recently, gen- 
erally insisted on in order to permit the rod to 
properly act, viz. : 

(1.) The rod, generally of iron or copper, 
should have such an area of cross- section as to 
enable it to carry without fusion the heaviest bolt 
it is liable to receive in the latitude in which it is 
located. 

When of iron, the area of cross-section should 
be about seven times greater than when of 
copper. 

(2.) The rod should be continuous throughout, 
all joints being carefully avoided. 

When joints are used, they should be made of as 
low resistance as possible, and should be pro- 
tected against corrosion. 

(3.) The upper extremity of the rod should 
terminate in one or more points formed of some 
metal that is not readily corroded, such as pla- 
tinum or nickel. 

(4.) The lower end of the rod should be car- 
ried down into the earth until it meets perma- 
nently damp or moist ground, where it should 
be attached to a fairly extended metallic surface 
buried in the ground. 

Metallic plates will answer for grounding the 



Rod.] 



463 



[Rod. 



rod, but, if gas or water pipes are available, the 
rod should be placed in good electrical connec- 
tion therewith, by wrapping it around and 
soldering \t to such pipes. 

This fourth requirement is of great importance 
to the proper action of a lightning rod, and un- 
less thoroughly fulfilled, may render the rod 
worthless, no matter how carefully the other re- 
quirements are attended to. When a bolt strikes 
a lightning rod which is not properly grounded, 
the discharge is almost certain to destroy the 
building to which the rod is connected. 

(5.) The rod should not be insulated from the 
building, unless to prevent stains from the oxi- 
dation of the metal. On the contrary, the rod 
should be directly connected with all masses of 
metal in its path, such as tin roofs, gutter spouts, 
metallic cornices, etc. In this way only can dan- 
gerous disruptive lateral discharges from the rod 
to such masses of metal be avoided. 

(6.) The rod should project above the roof or 
highest part of the building, or, in other words, 
the height of the rod should bear a certain pro- 
portion to the size of the building to be pro- 
tected. 

A rod will protect a conical space around it, 
the radius of whose base is equal to the vertical 
height of the rod above the ground, but whose 
sides are curved inwards instead of being straight. 
Where the building is very high, a number of 
separate rods all connected to one another should 
be employed. 

A lightning rod sometimes fails to protect a 
house or barn, from the fact that a heated, ascend- 
ing current of air from a fire in the house, or 
from the gradual heating of green hay or grain in 
the barn, acting as a conductor, increases the vir- 
tual height of the house beyond the ability of its 
rods to protect it. 

(7.) A stranded conductor is much better than 
an equal cross-section of a solid rod of the same 
metal. 

A copper tape is better than a copper rod for 
lightning rods, because a rapidly periodic current, 
whose periodicity is sufficiently great, passes 
practically over the surface of the conductor only. 
Considering an electric current as taking its 
energy from the surrounding dielectric, a tape is 
better, because the surface which absorbs the 
energy is greater in the case of a tape than of a 
solid rod. (See Law, Pointing's.) 

A lightning rod more frequently acts to quietly 
discharge an impending cloud by convective dis- 



charge than by an actual disruptive discharge of 
the same. (See Discharge, Convective. Dis- 
charge, Disruptive.) 

Lightning rods should be frequently tested to 
see that no breaks or oxidation of their joints 
have occurred. 

Professor Lodge takes exception to some of the 
heretofore generally received notions concerning 
the action of lightning rods. He distinguishes 
between two distinct kinds of discharge that may 
occur between a charged cloud and the earth, 
viz. : 

( 1 . ) A steady strain or current. 

(2.) An impulsive rush or oscillatory discharge. 

A discharge by a steady strain or current oc- 
curs when the cloud gradually approaches a point 
on the earth; or, in the case of the cloud being 
stationary, when it receives its charge gradually 
by the approach of another cloud. 

In steady discharge, the lightning rod, with its 
pointed end, either quietly discharges the cloud 
by a convective discharge, or by a harmless con- 
ductive discharge through the rod, after a spark 
has passed disruptively between the cloud and 
the rod. (See Discharge, Convective. Dis- 
charge, Conductive. Discharge, Disruptive.) 

The impulsive discharge or rush occurs when- 
ever the cloud that discharges to the earth re- 
ceives its charge suddenly, as by the discharge 
into it of a neighboring cloud, or when a bound 
charge, produced by the presence of a neighbor- 
ing charged cloud, is suddenly liberated by dis- 
harge, and, thus becoming free, impulsively dis- 
charges to the earth. 

In all cases of an impulsive discharge or rush, a 
counter electromotive force is set up in the rod, 
which resists the discharge through the rod and 
causes the electricity to rush back and spit off in 
lateral discharges. In this case the conducting 
power of the rod has no effect in facilitating the 
discharge. Indeed, the smaller its resistance, and 
the longer the oscillations last, the greater the 
danger from lateral discharges. (See Discharge, 
Lateral. Path, Alternative.) 

The following principles advanced by Lodge 
differ from the views heretofore generally re- 
ceived, viz.: 

(1.) Iron is a better substance for a lightning 
rod than copper, because it is equally as good a 
conductor as copper for very rapidly alternating 
currents, and is more difficult to fuse. 

(2.) All neighboring metallic conductors should 
be connected to earth. These connections should 



Rod.] 



461 



[Rot. 



preferably be by separate conductors rather than 
by the rod itself. 

(3.) The lightning conductors should have a 
good separate earth, but should be connected to 
water pipes, gas pipes, etc., if near them, by an 
underground connection. 

(4.) The lightning conductor should be de- 
tached from the building and not close against it. 

(5.) The rod should be of flat section, or a 
stranded conductor. 

Rod, Lightning-, for Ships A 

system of rods designed to afford electric 
protection for vessels at sea. 

Since the lightning discharge takes place be- 
tween the points of greatest difference of poten- 
tial, and these points are generally the cloud 
and the nearest point of the earth, tall objects are 
especially liable to be struck. 

Ships at sea should, therefore, be thoroughly 
protected from lightning. 

In Harris' system of lightning protection for 
ships, the rods are connected with a series of 
copper plates and rods so placed on the masts as 
to readily yield to strains. These plates or rods 
are electrically connected with the copper sheath- 
ing of the vessel and with all large masses of 
metal in the vessel. This latter precaution is 
especially necessary in the case of men-of-war, 
in order to protect the powder magazine. 

Harris' method for the lightning protection of 
ships was adopted only after very considerable 
opposition. It proved, however, so efficacious in 
practice that serious effects of lightning on vessels 
so protected are now almost unknown. In 1845, 
Harris received the honor of knighthood from 
the English Government for his services in this 
respect. 

Rod, Lightning, Points on Points 

of inoxidizable material, placed on lightning 
rods, to effect the quiet discharge of a cloud by 
convection streams. (See Rod, Lightning, 
Convection, Electric?) 

Rod, Thunder A term formerly 

used for lightning rod. (See Rod, Light- 
ning?) 

Rods, Bus Heavy copper rods em- 
ployed in a central or distributing station, to 
which all the terminals of the generating dy- 
namos are connected, and from which the cur- 
rent passes to the different points of the dis- 
tribution system over the feeders. 



Bus rods are often called bus bars or bus wires. 
(See Wires, Bus.) 

Rodding a Conduit.— (See Conduit, Rod- 
ding a) 

Rolling Contact.— (See Contact, Rolling) 

Rose, Ceiling An ornamental ceil- 
ing plate through which an electric conductor 
passes. 

Rosette. — An ornamental plate provided 
with contacts connected to the terminals of 
the service wires, and placed in a wall for the 
ready attachment of the incandescent lamp. 

A word sometimes used in place of rose. 

Rosette Cut-Out.— (See Cut-Out, Rosette) 
Rotary Magnetic Polarization.— (See 

Polarization, Magnetic Rotary) 

Rotary-Phase Current. — (See Current, 
Rotating) 

Rotary-Phase Dynamo. — (See Dynamo, 
Rotary-Phase) 

Rotary-Phase Motor.— (See Motor, Ro- 
tating Current) 

Rotary-Phase Transformer. — (See Trans- 
former, Rotary-Phase) 

Rotating Brushes of Dynamo-Electric 
Machine. — (See Brushes, Rotating, of 
Dynamo-Electric Machines) 

Rotating Current. — (See Curre?it, Rota- 
ting) 

Rotating Current Field. — (See Field, 
Rotating Current) 

Rotating Current Motor. — (See Motor, 
Rotating Current) 

Rotating Current Transformer. — (See 
Transformer, Rotatory Current) 

Rotation, Electro-Magnetic ■ — — — A 
rotation obtained by electro-magnetic attrac- 
tions and repulsions. (See Disc, Aragds. 
Disc, Faraday s. Motor, Electric) 

Rotation, Magneto-Optic A rota- 
tion of the plane of polarization of a beam 
of polarized light on its passage through a 
transparent medium when placed in a strong 
magnetic field. 

The medium only possesses such properties 
while in the field. 



Rub.] 



465 



[Saic 



In a ray of ordinary light the vibrations of the 
ether particles are at right angles to the direction 
of the ray, or to the direction in which the light 
is moving. But the vibrations occur indiscrimi- 
nately in all planes passing through the line of 
direction. Under certain circumstances, all the 
ether particles may be caused to move in planes 
that are parallel to one another. Such a beam of 
light is called a plane polarized beam. 

A plane polarized beam of light, when passed 
through many transparent substances, will have 
its ether particles vibrating in the same plane 
when it emerges from the medium, as it had before 
it entered. Some transparent substances, how- 
ever, possess the property of rotating or turning 
the plane of polarization of the light to the right 




Fig. 496. Magneto- Optic Rotation. 

or to the left. This property is called respec- 
tively right-handed rotary polarization, and left- 
handed rotary polarization. 

Many substances that ordinarily possess no 
power of rotary polarization acquire this power 
when placed in a magnetic field. This property 
of a magnetic field was discovered by Faraday . 



The effect is to be ascribed to the strain produced 
in the transparent medium by the stress of the 
magnetic field. It may be caused in solid bodies 
by mechanical force. 

The apparatus for demonstrating the rotation 
of the plane of polarization by a magnetic field is 
shown in Fig. 496. 

A powerful electro-magnet, M, M, is provided 
with a hollow core. The substance c, is placed 
in the field produced by the approached poles, 
and its action on the light of a lamp, placed at 
the end 1, is observed by suitable apparatus at a. 

Rubber of Electrical Machine. — A 

cushion of leather, covered with an electric 
amalgam, and employed to produce electricity 
by its friction against the plate or cylinder of 
a frictional electric machine. (See Macht7ie t 
Frictional Electric!) 

Rubbing 1 Contact— (See Contact, Rub- 
bing!) 

Ruhmkorff Coil.— (See Coil, Ruhmkorff!) 
Rnhmkorff's Commutator. — (See Com- 
mutator, Ruhmkorff "s!) 
Rule, Ampere's, for Effect of Current on 

Needle — A magnetic needle, when 

placed near a conductor through which a 
current is flowing, has its north pole deflected 
to the left of the observer, who is supposed 
to be swimming with the current and facing 
the needle. 



s 



S. — A contraction employed for second. 

S. H. 31. — A contraction employed for 
simple harmonic motion. 

S. N. Code. — A contraction for single needle 
code. 

S. W. G. — A contraction for Standard Wire 
Gauge. 

Saddles, Telegraphic B rackets 

placed on the top of telegraphic poles for 
the support of the insulators. 

Saddle brackets are usually employed for the 
wire attached to the top of a telegraph pole. (See 
Role, Telegraphic.) 



Safe Carrying- Capacity of a Conductor. 

— (See Capacity, Safe Carrying, of a Con- 
ductor!) 
Safety Catch.— (See Catch, Safety!) 
Safety Device for Multiple Circuits.— (See 

Device, Safety, for Multiple Circuits!) 
Safety Fuse. — (See Fuse, Safety!) 

Safety Lamp, Electric (See Lamp, 

Electric Safety!) 

Safety Plug.— (See Plug, Safety!) 
Safety Strip.— (See Strip, Safety!) 
Saint Elmo's Fire.— (See Fire, St. El- 
mo's!) 



Sal.] 



466 



[Sch. 



Salient Magnetic Pole.— (See Pole, Mag- 
netic, Salient?) 

Saline Creeping". — (See Creeping, Saline.) 

Salts, Electrolysis of The decom- 
position of a salt into its electro-positive and 
negative radicals or ions. (See Electrolysis.) 

Sandy Deposit, Electro-Metallurgical 

(See Deposit, Electro-Metallurgical, 

Sandy?) 

Saturated Solution. — (See Solution, Sat- 
urated.) 

Saturation, Magnetic The max- 
imum magnetization which can be imparted 
to a magnetic substance. 

The condition of iron, or other paramag- 
netic substance, when its intensity of mag- 
netization is so great that it fails to be further 
sensibly magnetized by any magnetic force, 
however great. 

When the core of an electro-magnet is saturated 
by the passage of an electric current, the only 
further increase of its magnetization that is possi- 
ble, is that due to the magnetic field of the in- 
creased current which may be sent through its 
coils. This is comparatively insignificant. 

A permanent magnet is sometimes said to be 
super-saturated, that is, to have received more 
magnetism than it can retain for any considerable 
time after its magnetization. 

In the saturated field magnets of a dynamo-elec- 
tric machine the magnetic density is seldom taken 
at a larger value than 16,000 lines per square cen- 
timetre of area of cross- section. But this is only 
practical saturation, since Ewing has forced 
45,300 lines per square centimetre by using an 
enormously high magnetizing force (H = 24,500). 

Saturation, Magnetic, Diacritical Point 

of A term proposed by S. P. Thomp- 
son for such a value of the co-efficient of 
magnetic saturation, that the core is mag- 
netized to exactly one-half its possible max- 
imum of magnetization. 

Saw, Electric A platinized steel 

wire, employed while incandescent for cut- 
ting hard substance. 

Scale, Tangent A scale designed 

for use with a galvanometer, on which the 
values of the tangents are marked, instead of 



equal degrees as ordinarily, thus avoiding the 
necessity of finding from tables the tangents 
corresponding to the degrees. 

Such a scale may be constructed as follows: 
Draw the tangent B T, to the circle, Fig. 497, 
and lay off on it any number of equal divisions 
or parts, as, for example, the thirty shown in the 
annexed figure. Connect these parts with the 
centre C, of the circle. The arc of the circle will 




C 
Fig-. 4Q7. Tangent Scale. 

thus be divided into parts proportional to the 
value of the tangents of the angles. 

These parts are more nearly equal the nearer 
they are to B, and grow smaller and smaller the 
further they are from B. In tangent galva- 
nometers it is therefore very difficult to accurately 
determine the current strength when the deflec- 
tions of the needle are very large. 

Scale, Thermometer, Centigrade A 

thermometer scale, in which the length of the 
thermometric tube between the melting point 
of ice and the boiling point of water is divided 
into one hundred equal parts or degrees. 

Centigrade degrees are indicated by a C, thus 
O degree C, or 100 degrees C, to distinguish them 
from Fahrenheit degrees that are marked F. 
In the Fahrenheit scale the freezing point of 
water is taken at 32 degrees, and the boiling point 
at 212 degrees. 

Scale, Thermometer, Fahrenheit's 

— A thermometer scale in which the length 
of the thermometer tube between the melting 
point of ice and the boiling point of water is 
divided into 180 equal parts called degrees. 

Fahrenheit degrees are indicated by an F., 
thus, 32 degrees F. 

The freezing point of water in Fahrenheit's 
scale is marked 32 degrees F., and the boiling 
point of water is marked 212 degrees F. 

Schiseophone.— An electro-mechanical ap- 
pliance for detecting flaws and internal de- 
fects in rails or other metallic masses. 

The schiseophone consists essentially in the 
combination of a microphone and telephone with 
a mechanical hammer and induction balance. 



Sch. 



467 



[Scr. 



Schweigger's Multiplier.— (See Multi- 
plier, Schweigger's.) 

Scintillating Jar. — (See Jar, Scintillat- 
ing.) 

Scratch Brush.— (See Brush, Scratch.) 

Scratch Brush, Circular — (See 

Brush, Scratch, Circular?) 

Scratch Brush, Hand (See Brush, 

Scratch, Hand.) 

Scratch Brushing'. — (See Brushing, 
Scratch) 

Screen, Electric A closed conduc- 
tor placed over a body to screen or protect it 
from the effects of external electrostatic fields. 

An electric screen is sometimes called an elec- 
tric shield. 

The ability of a closed, hollow conductor to act 
as a screen, arises from the fact that all points on 
its inner surface are at the same potential, and 
therefore are not affected by an increase or de- 
crease in the potential of the outside of the con- 
ductor as compared with that of the earth. (See 
Net, Faraday's.) 

No considerable thickness is required for the 
efficient operation of an electric screen. 

Screen, Magnetic — A hollow box 

whose sides are made of thick iron, placed 
around a magnet or other body so as to cut 
it off or screen it from any magnetic field ex- 
ternal to the box. 

Magnetic screens are placed around delicate 
galvanometers to avoid any variations in their 
field due to extraneous masses of iron or neigh- 
boring magnets. They are also sometimes placed 
around watches to shield or screen the works 
from the effects of magnetism. 

To act effectively, when the external fields are 
at all powerful, magnetic screens must be made 
of thick iron. They differ in this respect from 
electrostatic shields, which will afford protection 
against electrostatic charges although they may 
be but mere films. 

Screen, Methven's A vertical rec- 
tangular metallic screen used in connection 
with a standard argand burner, for furnish- 
ing a standard amount of light for photo- 
metric purposes. 

In a rectangular screen a small vertical slot is 
made of such dimensions as to permit an amount 



of light to pass just equal to two standard candles. 
The proper burning of the argand lamp is de- 
termined by supplying sufficient gas to produce 
a flame exactly 3 inches high. The glass 
chimney used in the burner is 6 inches high, 
and is provided with two horizontal wires placed 
on each side of the burner at the required height. 

Methven's screen possesses the advantage of 
being easily used and of furnishing a reliable 
standard of light. Extended experiments made 
with it appear to show that the amount of light 
produced depends rather on the height of the 
gas flame than on the quality of the gas itself. 
In using Methven's screen care should be taken 

(1.) To see that the gas flame is of exactly the 
required height. 

(2.) That the chimney on the lamp is quite 
clean. 

(3.) That the top of the flame is as regular as 
possible. 

As this last point is almost impossible to obtain in 
actual practice, the flame is 
adjusted so that the highest 
point extends about one- 
eighth of an inch above the 
height of the horizontal 
wires. 

(4.) That the lamp and 
apparatus be permitted to 
acquire its normal temper- 
ature before the readings 
are taken. 

Fig. 498 shows the con- 
struction of the ordinary 
Methven standard screen. 
The vertical slot in the 
screen is placed as shown 
before the standard argand 
burner. Horizontal wires 
for the adjustment of the height of the flame are 
placed one on each side of the gas chimney. 

Screening, Electrostatic Screening 

or shielding from the inductive effects of a 
charge. 

A continuous metallic surface surrounding an 
air space to be shielded, completely protects any 
body placed within such air space from electro- 
static influence. (See Cube, Faraday' s .) 

Screening, Magnetic Preventing 

magnetic induction from taking place by in- 
terposing a metallic plate, or a closed circuit 
of insulated wire, between the body producing 




Fig. 4Q8. Methven's 
Standard Screen. 



Scr.] 



468 



[Scr. 



the magnetic field and the body to be mag- 
netically screened. 

A magnetic needle is screened from the action 
of the earth's field by placing it inside a hollow 
iron box, which prevents the lines of force of the 
earth's field from passing through it by concen- 
trating them on itself. This action is dependent 
on the fact that iron is paramagnetic and there- 
fore offers the lines of force less resistance 
through its mass than elsewhere. A plate of 
copper would not effect any such magnetic 
shielding or screening. 

In any magnetic field, however, in which the 
strength of the field is undergoing rapid, periodic 
variations, a plate of copper or other electric 
conductor may act as a screen to protect neigh- 
boring conductors from the effects of magnetic 
induction, and its ability to thoroughly effect 
such a screening will depend directly on its 
conducting power. 

If, for example, the copper plate c (Fig. 499)> 
be interposed between a coil of copper ribbon a, 
and the fine wire coil b, it will greatly reduce the 
intensity of the induced currents, produced when 
rapidly alternating currents are sent through a. 
If, however, the copper plate be slit, as shown to 
the right at a, the screening effect is lost, but is 
regained if the slit be connected by a conductor. 
Similarly a flat coil of insulated wire effects no 
screening action when open, but when closed acts 
as the uncut copper plate. 

Here the screening action is due to thp fact 
that the energy of the field is spent in producing 
eddy currents in the interposed metal screen or 
coils. If the metal screen is discontinuous in the 
direction in which the eddy currents tend to flow, 
the inability of the screen to absorb the energy as 
eddy currents prevents its action as a screen. 




induction from occurring in a neighboring con- 
ductor, by interposing some conducting substance 
in which eddy currents can be freely established. 

As to the efficiency of the screening action, if the 
makes-and -breaks do not follow one another very 
rapidly, the following principles can be proved : 

(i.) If the screening material have absolutely 
no electrical resistance it will effect a perfect mag- 
netic screening when placed between the primary 
and secondary, no matter what its thickness 
may be. 

(2.) If the screen have a finite conductivity, 
the screening will be imperfect, unless the thick- 
ness of the material employed is considerable. 

If, however, the makes-and-breaks follow one 
another very rapidly, then 

The screening effect of even imperfect conduc- 
tors will become manifest with comparatively 
thin screens of metal. 

As to magnetic screening, therefore, it follows 
that the less the conductivity, the greater must 
be the speed of reversal, in order that the screen- 
ing action may be effective. 

Where a screen of iron is employed, an ad- 
ditional effect is produced by the fact that the 
small magnetic resistance of the metal, or its con- 
ductivity for lines of magnetic force, causes the 
lines of induction to pass through its mass, and 
thus effect a screening action for the space on the 
other side. This action is, by some, called mag- 
netic screening. 

In the case of iron screens, considerable thick- 
ness is required in the metal plate, in order to 
obtain efficient screening action of this latter 
character. On account of this action of iron, in 
conducting away lines of force, a much smaller 
speed of reversal is required, in order to obtain 
effective screening action, where plates of iron 
are used, than in the case of plates of other 
metal. 

The apparatus shown in Fig. 500 was employed 




Fig. 4Q9. 

The word magnetic screening is generally em- 
ployed in the latter sense of preventing magnetic 



m. 

Fig. 500, Willoughby Smith 's Apparatus. 

by Mr. Willoughby Smith, in studying the effects 
of magnetic screening. 

The flat coils A, and B, were employed for the 
primary and secondary coils respectively, and 
were connected to the battery C, and the galva- 



ScrJ 



469 



[Sec. 



nometer F, as shown. Current reversers, D and 
E, were so arranged as to reverse galvanometer 
and battery alternately, and so cause the oppo- 
site induced currents to affect the galvanometer in 
the same direction. If the commutators were 
caused to reverse the current slowly, a plate of 
copper interposed between A and B, produced 
but little effect on the galvanometer, but if the re- 
versers were driven at a very rapid rate, a marked 
decrease of deflection occurred. 

The screening action of the metals, or their 
ability to diminish the galvanometer deflection, 
is in the order of their electrical conductivity, ex- 
cept in the case of iron, which, as we have seen 
already, has an additional screening power, due 
to its conducting away the lines of magnetic force. 

It follows from the preceding principles that 
the use of lead covered cables, for the conveyance 
of periodic currents, of the frequency of, say, sixty 
to one hundred alternations per second, is of but 
little or no advantage for protecting neighboring 
telephones from inductive action, because 

(i.) Lead is a poor conductor. 

(2.) The rapidity of alternation is too slow. 

J. J. Thomson made some experiments with 
electrical oscillations produced by resonance, of 
about io* in frequency. He obtained this fre- 
quency of oscillation from oscillations set up in 
the primary of an induction coil, in a secondary 
circuit of suitable dimensions. The presence of 
these secondary vibrations or waves was shown 
by means of the sparks seen at the terminals of a 
spark-micrometer circuit. Under these circum- 
stances he found that the interposition of a thin 
sheet of tin foil or gold leaf at once completely 
stopped the secondary sparks by the shielding 
action it exerted. 

— Screen- 



Screening 1 , Magnetostatic — 

ing from the inductive effect of a stationary 
magnetic field. 

Magnetostatic screening differs from electrostatic 
screening in that the plate of iron or other para- 
magnetic material surrounding the space to be 
screened must have a fairly considerable thick- 
ness. This arises from the fact that the magnetic 
susceptibility of the substance is not infinitely 
great. 

Screw, Binding 1 A name some- 
times applied to a binding post. (See Post, 
Binding.) 

Seal, Hermetical Such a sealing of 



a vessel, designed to hold a vacuum, or gas- 
eous atmosphere under pressures greater or 
less than that of the atmosphere, as will pre- 
vent either the entrance of the external at- 
mosphere into the vessel, or the escape of the 
contained gas into the atmosphere. 

Hermetical sealing may be accomplished either 
by the use of suitable cements, or by the direct 
fusion of the walls of the containing vessel. The 
latter method is generally employed. 

Search Light, Automatic —(See 

Light, Search, Automatic.) 

Search Light, Electric (See Light, 

Search, Electric.) 

Secohm. — The practical unit of self-induc- 
tion, or the practical unit of inductance. 

The secohm is equivalent to a length equal to 
that of an earth quadrant, or 10'* centimetres. 

The word secohm is a contraction for second, 
ohm, and implies the fact that the product of the 
ohm and the second are taken. 

The word henry is now generally used in the 
United States for secohm. (See Henry.) 

Secohmmeter. — An apparatus for measur- 
ing the co-efficient of self-induction, mutual 
induction and capacity of conductors. (See 
Secohm. Induction, Mutual. Induction, 
Self.) 

The principle of the secohmmeter depends 
upon successively performing the cycle of magnetic 
operations, by making and breaking the circuit 
of a galvanometer by means of a commutator 
capable of working at a definite speed. 

Second, Ampere One ampere flow- 
ing for one second. (See Hour, Ampere) 

Second, Watt A unit of electrical 

work. 

A watt -second equals the work due to the ex- 
penditure of an electrical power of one watt for 
one second. It is the same as a volt-coulomb. 

The watt-second and the H. P. hour, etc., 

Work 
Time 
therefore, power X time = work. 

Secondary Battery. — (See Battery, Sec- 
ondary.) 

Secondary Battery, Cell of —(See 

Cell, Secondary.) 



are units of work, since Power 



Sec] 



470 



[Sec. 



Secondary Cell. — (See Cell, Secondary) 

Secondary Cell, Jar of (See far of 

Secondary Cell) 

Secondary Clock. — (See Clock, Second- 
ary) 

Secondary Coil. — (See Coil, Secondary) 

Secondary Currents. — (See Currents, 
Secondary) 

Secondary, Fixed The secondary 

of an induction coil, that, as is common in 
such coils, is fixed, as contradistinguished 
from a movable secondary. (See Secondary, 
Movable) 

Secondary Generator. — (See Generator, 
Secondary) 

Secondary Impressed Electromotive 
Force. — (See Force, Electromotive, Second- 
ary Impressed) 

Secondary, Movable The second- 
ary conductor of an induction coil, which, in- 
stead of being fixed as in most coils, is mova- 
ble. 

The peculiar movements observed in the 
secondary of an induction coil when the second- 
ary is free to move, have been carefully studied 
by Prof. Elihu Thomson. The secondaries 
employed for this purpose are in the shape of 
rings, discs, spheres, wedges, bars, wheels, etc., 
etc. 

The primary is in the form of a straight cylin- 
drical coil surrounding a straight core. The coils 
are traversed by rapidly alternating currents and 
possess considerable impedance. 

Among the many phenomena concerning the 
behavior of movable secondaries in such a rapidly 
alternating field are the following, viz.: 

(I.) A metallic ring, resting on lugs attached 
to the coils of the primary, is thrown violently off 
the magnet on the passage of alternating currents 
through the primary. 

(2.) Two metallic rings of the same diameter 
brought into the field are mutually attracted to 
each other, with sufficient force to sustain the 
weight of one of the rings when the other ring is 
held in the field. 

(3.) Metallic spheres are set into rotation when 
so held near the primary pole as to be shielded 



from the action of part of the rapidly alternating 
field. When held on one side of the pole, this 
rotation occurs in the opposite direction to that 
when held on the opposite side. 

(4.) Metallic discs similarly placed are simi- 
larly set into rotation. 

(5.) The speed ot rotation of spheres or discs 
varies in different positions. 

(6.) Spheres or discs of diamagnetic substances 
attain their maximum rotation when held in posi- 
tion at right angles to those of paramagnetic sub- 
stances. 

(7.) Bars of steel or substances possessing high 
coercive power, placed dissymmetrically on the 
primary as regards their centres of gravity, ex- 
hibit the phenomena of a shifting magnetic field. 
(See Field, Magnetic, Shifting) 

(8.) A wedge-shaped piece of steel placed with 
a flat face on the primary, exhibits a shifting 
magnetic field, and acts on movable metallic 
masses near it, just as though a fluid substance 
was escaping with great velocity from its edges. 

Secondary Movers. — (See Movers, Second- 
ary) 

Secondary Plate of Condenser. — (See 
Plate, Secondary, of Cojidenser) 

Secondary Spiral. — (See Spiral, Second- 
ary) 

Secretion Current. — (See Current, Secre- 
tion) 

Section Line of Electric Railway. — (See 
Railroads, Electric, Section Line of) 

Section, Neutral, of Magnet — A 

section passing through the neutral line or 
equator of a magnet. (See Line, Neutral, 
of a Magnet. Magnet, Equator of) 

Section, Trolley A single contin- 
uous length of trolley wire, with or without 
its branches. 

Sectional or Divided Overhead System 
of Motive Power for Electric Railroads. — 

(See Railroads, Electric, Sectioiial Over- 
head System of Motive Power for) 

Sectional or Divided Surface System of 
Motive Power for Electric Railroads. — 

(See Railroads, Electric, Sectional Surf ace 
System of Motive Power for) 



Sec] 



471 



[Sep. 



Sectional or Divided Underground 
System of Motive Power for Electric Kail- 
roads. — (See Railroads, Electric, Sectional 
Underground System of Motive Power for) 

Sectional Plating. — (See Plating, Sec- 
tional.) 

Sectional Plating Frame. — (See Frames, 
Sectional Plating.) 

Seebeck Effect— (See Effect, Seebeck) 

Seismograph, Electric An appa- 
ratus for electrically recording the direction 
and intensity of earthquake shocks. 

Seismograph, Micro An electric 

apparatus for photographically registering 
the vibrations of the earth produced by earth- 
quakes or other causes. 

The micro-seismograph consists essentially of a 
microphone placed on the ground and connected 
with a telephone. A small concave mirror mova- 
ble about a horizontal axis is supported on a 
plate of aluminium supported on a platinum wire 
connected with the diaphragm of the telephone. 
The movements of the diaphragm of the telephone 
are permanently recorded on a strip of sensitized 
paper that is moved before the mirror. 

Selective Absorption. — (See Absorption, 
Selective.) 

Selenium. — A comparatively rare element 
generally found associated with sulphur. 

Selenium Battery.— (See Battery, Selen- 
ium.) 

Selenium Cell. — (See Cell, Selenium) 

Selenium Eye. — (See Eye, Selenium) 

Selenium Photometer. — (See Photometer, 
Selenium.) 

Self-Induced Current.— (See Currents, 
Self-Induced) 

Self-induction. — (See Induction, Self) 

Self-induction, Co-efficient of (See 

Induction, Self Co-efficient of) 

Self-Kecording Magnetometer.— (S e e 
Mag net om eter, Self -Recording) 

Self-Registering Wire Gauge. — (See 
Gauge, Wire, Self -Registering) 

Self-Winding Clock.— (See Clock, Self- 
winding) 



Semaphore. — A variety of signal apparatus 
employed in railroad block systems. 

The semaphore used on the Pennsylvania Rail- 
road consists of a wooden post, in the neighbor- 
hood of twenty feet in height, on which a wooden 
arm or blade, six feet in length and a foot in 
width, is displayed. 

When the block is clear, during the day the 
arm is placed pointing downwards at an angle of 
75 degrees with the horizontal ; during night 
semaphore displays a white light. When the 
block is not clear, the arm or blade is placed in a 
horizontal position by day, or displays a red light 
at night. (See Railroads, Block System for.) 

Semaphore Arm. — (See Arm, Semaphore) 

Semaphore Indicator. — (See Indicator, 
Semaphore) 

Sender, Zinc A device employed 

in telegraphic circuits, by means of which, in 
order to counteract the retardation produced 
by the charge given to the line, a momen- 
tary reverse current is sent into the line after 
each signal. 

A zinc sender generally consists of a low resist- 
ance Siemens relay introduced between the line 
and the front contact of the signaling key. 

Sensibility, Electro An effect pro- 
duced on a sensory nerve by its electrization. 

Sensibility of Galvanometer. — (See Gal- 
vanometer, Sensibility of) 

Sensitive Thread Discharge.— (See Dis- 
charge, Sensitive Thread) 

Separate Coil Dynamo-Electro Machine. 
— (See Machine, Dynamo-Electric, Separate 
Coil) 

Separate Touch, Magnetization by 

— (See Touch, Separate) 

Separately Excited Dynamo.— (See Dy- 
namo, Separately Excited) 

Separately Excited Dynamo-Electric 
Machine. — (See Machine, Dynamo-Electric, 
Separately Excited) 

Separator. — An insulating sheet of ebonite, 
or other similar substance, corrugated and 
perforated so as to conform to the outline of 
the plates of a storage battery, and placed 
between them at suitable intervals, in such a 



Ser.] 472 [Ser. 

manner as to avoid short-circuiting, without The difference in potential between zinc and 

impeding the free circulation, of the liquid. carbon is equal to 1.089, and is obtained by add- 

Series and Magneto Dynamo-Electric ing the successive differences of potential between 

_, , . ,_ ., -, . -~ 7-7 . • the intermediate couples, thus: 
Machine.— (See Machine, Dynamo-Electric, 

Series and Magneto) .210+ .069 +.313 + .146+ .238 +.113 =1.089. 

Series and Separately Excited Dynamo- This fact is known technically as Voltes Law, 

Electric Macliine.-(See Machine, Dynamo- which ma ? be formulated as follows: 

^ 7J . ~ . 7 <-, , ^77- ., 7n The difference of potential, produced by the con- 

Electric, Series and Separately Excited) . •" , . . . , c , 

tact of any two metals, is equal to the sunt of the 

Series and Shunt-Wound DynaniO-Elec- differences of potentials between the intervening 

trie Machine.— (See Machine, Dynamo- metals in the contact series. 

Electric, Series and Shunt-Wound) gerieg Distributi(m of Electricity by 

Series Circuit.-(SeeaV^//,5^^.) Constant Currents.-(See Electricity, Se- 

Series-€onnectedBattery.-(See^//^, ^ Distribution o/> by constant Current 

Series-Connected) Circuit ) 

Series-Connected Electro-Keceptive De- Series-Multiple.-A series of multiple 

vices.-(See Devices, Electro-Receptive, Se- connections> (See Circuit> Series-Multiple) 

ries—Co7inected. \ 

Series-Connected Electro-Keceptive De- Series-Multiple Circuit.-(See Circuit, 

yices, Automatic Cut-out for (See Series-Multiple) 

Cut-out, Automatic, for Series-Connected Series -Multiple-Connected Electro-Ee- 

Electro-Receptive Devices) ce l )tive Devices.- (See Devices, Electro-Re- 

Series-Connected Sources.-(See Sources, ce £ tive > Series-Multiple-Connected) 

Series-Connected) Series-Multiple-Connected Sources. — 

Series-Connected Translating Devices. ( See Sources, Series-Multiple-Comtected) 

— (See Devices, Translating, Series-Con- Series-Multiple-Connected Translating" 

nected) Devices. — (See Devices, Translati?ig, Series- 

Series-Connected Voltaic Cells. — (See Multiple-Connected) 

Cells, Voltaic, Series-Connected) Series-Multiple Connection.— (See Con- 
Series Connection.— (See Connection, nection, Series-Multiple) 

Series) Series, Parallel A term some- 
Series, Contact A series of metals times applied to a multiple-series connection. 

arranged in such an order that each becomes (See Connection, Multiple-Series) 

positively electrified by contact with the one j^^ Tlierill0 _Electric A list of 

that follows it. metals so arranged according to their ther- 

The contact values of some metals, according , ^ . , , . , ,. -\ • ±\ 

, _ ... & mo-electric powers, that each metal m the 

to Ayrton and Perry, are as follows: . . , ■ 

series is electro-positive to any metal lower in 

CONTACT SERIES. t h e list. 

Difference of Potential in Volts. Series-Transformer. — (See Transformer, 

Zinc ) Series) 

Lead f Series Turns of Dynamo-Electric Ma- 

TrH I 069 chine. — (See Turns, Series, of Dynamo- 

Tin ' ' J Electric Maclmie) 

Iron! .. J 3 X 3 Series Winding". — (See Winding, Series) 

Iron I IA 6 Series-Wound Dynamo.— (See Dynamo, 

^l" Series) 

Platmum \ 2 3 8 Series-Wound Dynamo-Electric Machine. 

Platinum j — (See Machine, Dynamo-Electric, Series* 

Carbon.!.':!.': \ n 3 Wound) 



Ser.] 



473 



[She. 



Series-Wound Motor.— (See Motor, Se- 
ries- Wound.) 

Service Conductors. — (See Conductors, 
Service) 

Service, Street In a system of in- 
candescent lamp distribution that portion of 
the circuit which' is included between the 
main and the service cut-out. 



-The covering of 



Serving, Cable — 

hemp or jute spun around the insulated core 
of a cable to act as a protection against the 
pressure of the iron wire which forms the 
armor of the cable. 

Shackling* a Wire. — Inserting an insula- 
tion between the two ends of a cut wire, 

Shaded or Screened. — Cut off or screened 
from the effects of an electrostatic or mag- 
netic field. (See Screening, Mag?ietic. Screen, 
Magnetic. Screen, Electric) 

Shadow, Electric A term some- 
times used for molecular shadow. (See 
Shadow, Molecular) 

Shadow, Molecular The compara- 
tively dark space on those parts of the walls 
of Crookes' tubes, which have been protected 
from molecular bombardment by suitably 
placed screens. 




Fig. 501. Molecular Shadow. 

If a, in the Crookes tube, shown in Fig. 501, 
be connected with the negative pole of an elec- 
tric source, and the cross-shaped mass of alu- 
minium at b, be connected with the positive elec- 
trode, on the passage of a series of rapid 
discharges, phosphorescence is produced by the 
molecular bombardment from a, in all parts of 
the vessel opposite a, except those lying in the 



projection of its geometrical shadow. (See Phos- 
phorescence, Electric. ) 

Shadow Photometer.— (See Photometer, 
Shadow) 

Shaft, Driven A shaft which re- 
ceives its power from the driving shaft. (See 
Mover, Prime) 

Shaft, Driving The main line of 

shafting which takes its power directly from 
the prime mover. 

Shallow-Water Submarine Cable.— (See 

Cable, Submarine, Shallow- Water) 

Sheath, Protective A device at- 
tached to a transformer or converter, to pre- 
vent any connection from taking place between 
the high-potential primary circuit and the 
low-potential secondary circuit. 

The protective sheath devised by Prof. Ehhu 
Thomson consists essentially in an earth -con- 
nected copper strip or divided plate interposed 
between the windings for the secondary and pri- 
mary circuit. Should the primary circuit lose its 
high insulation it becomes grounded. 

Sheet, Current — The sheet into 

which a current spreads when the wires of 
any source are connected at any two points 
near the middle of a very large and thin con- 
ductor. 

A continuous electric current does not flow 
through the entire mass of a conductor in any 
single line of direction. If the terminals of any 
source are connected to neighboring parts of a 
greatly extended thin conductor, the current 
spreads out in a thin sheet known as a cur- 
rent sheet, and instead of flowing in a straight 
line between the points, spreads over the plate 
in curved lines of flow, which, so far as shape is 
concerned, are not unlike the lines of magnetic 
force. 

Sheet Lightning'. — (See Lightning, 
Sheet) 

Shellac. — A resinous substance possessing 
valuable insulating properties, which is ex- 
uded from the roots and branches of certain 
tropical plants. 

The specific inductive capacity of shellac as 
compared with air is 2.74. 



She.] 



474 



[Shu. 



Shell, Magnetic 



-A sheet or layer 



consisting of magnetic particles, all of whose 
north poles are situated in one of the flat 
surfaces of the layer, and the south poles in 
the opposite surface. (See Magnetism, La- 
mellar Distribution of) 

Shell Transformer. — (See Transformer, 
Shell) 

Shield, Magnetic, for Watches A 

hollow case of iron, in which a watch is per- 
manently kept, in order to shield it from the 
influence of external magnetic fields. (See 
Scree?i, Magnetic) 

Shifting Magnetic Field.— (See Field, 
Magnetic, Shifting) 

Shifting Zero. — (See Zero, Shifting) 

Ships, Lightning Rods for (See 

Rod, Lightning, for Ships) 

Ship's Sheathing, Electric Protection of 

■Attaching pieces of zinc to the copper 



sheathing of a ship for the purpose of prevent- 
ing the corrosion of the copper by the water. 
(See Metals, Electrical Protectio7i of) 

Shock, Break A term sometimes 

employed in electro-therapeutics for the 
physiological shock produced on the opening 
or breaking of an electric circuit. 

Shock, Electric The physiological 

shock produced in an animal by an electric 
discharge. 

Shock, Opening The physiological 

shock produced on the opening or breaking 
of an electric circuit. 

Shock, Static A term employed in 

electro-therapeutics for a mode of applying 
Franklinic currents or discharges, by placing 
the patient on an insulating stool and apply- 
ing one pole of a static machine provided 
with small condensers or Leyden jars, to an 
insulated platform on which the patient is 
placed, while the other pole is applied to the 
body of the patient by the operator. 

The electrode applied to the body of the pa- 
tient is provided with a ball electrode. Shocks 
are given to the patient on the approach of 
this electrode by the discharge of the Leyden 
jars. 



Short- Arc System of Electric Lighting. 

— (See Lighting, Electric, Short-Arc Sys- 
tem) 

Short-Circuit. — To establish a short cir- 
cuit. (See Circuit, Short) 

Short-Circuit Key.— (See Key, Short- 
Circuit) 

Short-Circuiting. — Establishing a short 
circuit. (See Circuit, Short) 

Short- Circuiting Plug. — (See Plug, 
Short-Circuiting) 

Short-Coil Magnet. — (See Magnet, Short- 
Coil) 

Short-Core Electro-Magnet. — (See Mag- 
net, Electro, Short-Core) 

Short-Shunt Compound-Wound Dyna- 
mo-Electric Machine. — (See Machine, Dy- 
namo-Electric, Compound- Wound, Short- 
Shunt) 

Shunt. — An additional path established 
for the passage of an electric current or dis- 
charge. 

Shunt. — To establish an additional path 
for the passage of an electric current or dis- 
charge. 

Shunt and Separately Excited Dynamo- 
Electric Machine. — (See Machine, Dynamo- 
Electric, Shunt and Separately Excited) 

Shunt Circuit. — (See Circuit, Shunt) 

Shunt Dynamo-Electric Machine.— (See 

Machine, Dyna?no-Electric, Shunt- Wound) 

Shunt, Electric Bell (See BelL 

Shunt, Electric) 

Shunt, Electro-Magnetic In a sys- 
tem of telegraphic communication an electro- 
magnet whose coils are placed in a shunt 
circuit around the terminals of the receiving 
relay. 

The electro-magnetic shunt operates by its 
self-induction. Its poles are permanently closed 
by a soft iron armature so as to reduce the resist- 
ance of the magnetic circuit. (See Induction, 
Self) 



Shu.] 475 



[Sin. 



On making the circuit in the coils of a receiv- 
ing relay, a current is produced in the coils of the 
electro- magnetic shunt in the opposite direction 
to the relay current; and, on breaking the circuit 
in the relay, a current is produced in the coils of 
the electro-magnetic shunt in the same direction 
as the current in the relay. 

The connection of the coils of the electro-mag- 
netic shunt with those of the receiving relay, how- 
ever, is such that on making the circuit in the 
relay the current in the shunt coils flows through 
the relay in the same direction, and on breaking 
the circuit it flows in the opposite direction. 
Therefore this shunt produces the following effects : 

(i.) At the commencement of each signal in 
the receiving relay, it produees an induced cur- 
rent in the same direction which strengthens the 
current in the relay. 

(2.) At the ending of each signal in the receiv- 
ing relay, it produces a current in the opposite 
direction, which hastens the motion of the tongue 
of the polarized relay. (See Relay, Polarized.') 

Shunt, Galvanometer A shunt 

placed around a sensitive galvanometer for 
the purpose of protecting it from the effects 
of a strong current, or for altering its sensi- 
bility. (See Shunt?) 

The current which will flow through the shunt 
wire depends on the relative resistance of the gal- 
vanometer and of the shunt. In order that only 

TO' T¥o> or xoVo' of the 
total current shall pass 
through the galvanome- 
ter, it is necessary that 
the resistances of the 
shunt shall be the \, g 1 ^, 
or -g-i-^, of the galvanom- 
eter resistance. 

Fig. 502 shows a 
shunt, in which the re- 
sistances, as compared 
with that of the galva- 
nometer, are those above 
referred to. The galva- 
nometer terminals are 
connected at N, N. Plug 
keys are used to connect one or another of the 
shunts with the circuit. (See Shunt, Multiplying 
Power of.) 

Shunt, Magnetic An additional 

path of magnetic material provided in a mag- 




Fig. so 2. Galvanometer 
Shunt. 



netic circuit for the passage of the lines o£ 
force. 
Shunt, Multiplying Power of — a. 

quantity, by which the current flowing through 
a galvanometer provided with a shunt, must 
be multiplied, in order to give the total cur- 
rent. 

The multiplying power of a shunt may be de- 
termined from the following formula, viz.: 

s + 



m 



X C, in which 



= the mul- 



tiplying power of a shunt whose resistance is s; 
g, is the galvanometer resistance; C, the current 
through the galvanometer, and A, the total cur- 
rent passing; s and g, are taken in ohms, and C 
and A, in amperes. 

Suppose, for example, that but ^ the entire 
current is to flow through the galvanometer; then 
the resistance of the shunt must evidently be \ g, 
for, 

s 1 _ 1 < 

s-f g — 1 + 9 _ 10' 
or, ios = s-fg. 10 s — s=g .-. 9 s=g; or, 

s = (i)g- 

Shunt or Reducteur for Ammeter. — (See 
Reducteur or Shunt for Ammeter?) 

Shunt Ratio.— The ratio existing between 
the shunt and the circuit which it shunts, 
(See Shunt, Multiplying Power of.) 

Shunt, Relay, Stearns' — A shunt 

employed in the differential method of duplex 
telegraphy to short-circuit the relay and then 
permit the line current to be cut off directly 
after it has completed its work in closing the 
local circuit. 

The use of the relay shunt permits the slacken- 
ing of the armature spring of the relay, because 
the decreased duration of the line current does 
not produce so strong a magnetization of the 
iron. 

Shunt-Turns of Dynamo-Electric Ma- 
chine. — (See Turns, Shunt, of Dynamo- 
Electric Machine?) 

Shunt-Wound Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric, 
Shunt- Wound?) 

Shunt- Wound Motor. — (See Motor,. 
Shunt- Wound.) 



Shu.] 



476 



[Sig. 



Shunting. — Establishing a shunt circuit. 

Shuttle Armature. — (See Armature, 
Shuttle?) 

Side A, of Quadruplex Table. — (See Table, 
Quadruplex, A, Side of.) 

Side B, of Quadruplex Table.— (See Table, 
Quadruplex, B, Side of) 

Side Flash.— (See Flash, Side.) 

Sidero-Magnetic. — (See Magnetic, Side- 
ro.) 

Siemens' - Armature Electro-Magnetic 
Bell. — (See Bell, Electro-Magnetic, Siemens 
Armature Form?) 

Siemens' Differential Voltameter, — (See 
Voltameter Siemens' Differ -ential.) 

Siemens' Electric Pyrometer,— (See Py- 
rometer, Siemens' Electric?) 

Siemens-Halske Voltaic Cell.— (See Cell, 
Voltaic, Siemens-Halske?) 

Siemens' Water Pyrometer.— (See Py- 
rometer, Siemens' Water?) 

Signal Arm. — (See Arm, Signal?) 



Signal, Electric Tell-Tale 



-An 



electrically operated signal, generally silent, 
whereby the appearance of a white or colored 
disc, on a black or otherwise uniformly 
colored surface, indicates the occurrence of 
a certain predetermined event. 

Signal Service for Electric Railways. — 
(See Railroads, Electric, Signal Service 
Sy stein for?) 

Signals, Electro-Pneumatic Sig- 
nals operated by the movements of dia- 
phragms or pistons moved by compressed 
air, the escape of which is controlled electri- 
cally. 

Signaling, Balloon, for Military Pur- 
poses ■ Transmitting intelligence of the 

movements of an enemy's army obtained from 
observations made in balloons by means of tel- 
ephone circuits connected with the balloon. 



Signaling, Curb 



— In cable teleg- 



raphy a system for avoiding the effects of 
retardation by rapidly discharging the cable 
before another electric impulse is sent into 



it, by reversing the battery, before connecting 
it to earth, and then connecting to earth be- 
fore beginning the next signal. 

Signaling, Double-Curb In curb 

signaling, a method by which the cable, after 
being connected with the battery for sending 
a signal, is subjected to a reverse battery, but 
instead of being put to earth after this con- 
nection, as in single-curb signaling, the bat- 
tery is again reversed and connected to earth. 

The time during which the cable is connected 
to the reversed battery before being put to earth, 
that is, the time during which it receives the 
positive and negative currents, may be made of 
any suitable duration. 

Signaling, Double-Current Signal- 
ing by means of currents that alternately 
change their direction. 

Double-current signaling was devised by Var- 
ley in order to avoid the effects of the induction 
of underground conductors on Morse tele- 
graphic apparatus. The idea of reversing the 
direction of the current was to hasten the dis- 
charge of the wire, which was prolonged by in- 
duction. Double- current working, however, 
possesses other advantages, and is used in duplex 
and quadruplex transmission. 

Signaling, Single-Curb — In curb 

signaling, a method by which the cable, after 
connection with the battery for sending a 
signal, is subjected to a reverse battery cur- 
rent, and then put to earth before again being 
connected to the battery for sending the next 
signal. 

Signaling, Single-Current Signal- 
ing by making or breaking the circuit of a 
single current. 

Single-current signaling is of two kinds, viz. : 
, (i.) Open-Circuit Signaling, in which the bat- 
teries are fixed at each station, and are in circuit 
only when signaling. 

(2.) Closed-Circuit Signaling, where the bat- 
teries are divided, one half generally being at each 
end of the line, and so connected that both sets 
flow in the same direction. 

Signaling, Single-Current, Closed-Circuit 

A system of single-circuit signaling in 

which the sending batteries are placed at 
each end of the line and are so connected as 



Sig. 



477 



[Sill. 



to remain always in circuit. (See Signaling, 
Single- Current?) 
Signaling, Single-Current, Open-Circuit 

A system of single-current signaling 

in which the sending batteries, fixed at each 
station, are in circuit during signaling only. 
(See Signaling, Single-Current.) 

Signaling, Telocity of Transmission of 

The speed or rate at which successive 

signals can be sent on any line without the 
retardation producing serious interference. 
(See Retardation?) 

Silent Discharge. — (See Discharge, Si- 
lent.) 
Silver Bath.— (See Bath, Silver.) 

Silver Chloride Toltaic Cell.— (See Cell, 
Voltaic, Silver Chloride?) 

Silver Plating.— (See Plating, Silver?) 

Silver Toltameter. — (See Voltameter, 
Silver?) 

Silvered Plumbago. — (See Plumbago, Sil- 
vered?) 

Silvering, Electro Covering a sur- 
face with a coating of silver by electro-plat- 
ing. (See Plating, Electro?) 

Electro-plating with silver. 

Silurus Electricus. — The electric eel. 
(See Eel, Electric?) 

Simple Arc. — (See Arc, Simple?) 
Simple Circuit. — (See Circuit, Simple?) 
Simple Electric Candle-Bnrner.— (See 
Burner, Simple Candle Electric?) 

Simple-Harmonic Current. — (See Cur- 
rent, Simple-Har7nonic?) 

Simple-Harmonic Curve. — (See Curve, 
Si77iple-Harmonic?) 

Simple-Harmonic Motion. — (See Motion, 
Simple-Ha mi on ic.) 

Simple Magnet— (See Mag7iet, Simple?) 

Simple-Periodic Current. — (See Cur- 
rents, Sii7iple-Per iodic?) 

Simple-Periodic Electromotive Force. 
—(See Force, Electro77iotive, Simple- 
Periodic.) 



Simple-Periodic Motion.— (See Motion, 
Simple-Periodic.) 

Simple Radical. — (See Radical, Simple.) 

Simple-Sine Motion. — (See Motion, 
Simple- Sine.) 

Simple Toltaic Cell.— (See Cell, Voltaic, 
Simple.) 

Simplex Telegraphy. — (See Telegraphy, 
Simplex.) 

Sims-Edison Torpedo. — (See Torpedo, 
Sims-Ediso7i.) 

Sine Galvanometer. — (See Galva7io77ieter, 
Sine?) 

Single-Brush Rocker. — (See Rocker, 
Single-Brush.) 

Single-Cup Insulator. — (See Bisulator, 
Si7igle-Shed.) 
Single Curb. — (See Curb, Single?) 

Single-Current Signaling. — (See Sig7ial- 
ing, Single-Current.) 

Single-Curve Trolley Hanger. — (See 
Hanger, Single-Curve Trolley?) 

Single-Fluid Hypothesis of Electricity. 

— (See Electricity, Si7igle-Fluid Hypothesis 
of.) 

Single-Fluid Toltaic Cell.— (See Cell, 
Voltaic, Si7igle-Fluid.) 

Single-Loop Armature. — (See Ar7nature, 
Single-Loop.) 

Single-Magnet Dynamo-Electric Ma- 
chine.— (See Machi7ie, Dynia77io-Electric, 
Si7igle-Magnet.) 

Single-Pair Toke. — (See Yoke, Single- 
Pair.) 

Single-Shackle Insulator. — (See bisula- 
tor, Si7igle-Shackle.) 

Single-Shed Insulator. — (See Insulator, 
Si7igle-Shed.) 

Single-Stroke Electric Bell.— (See Bell, 
Single- Stroke Electric.) 

Single Touch. — (See Touch, Single.) 

Single-Wire Cable.— (See Cable, Single- 
IVire.) 



Sin.] 



478 



[Sine. 



Single-Wire Circuit. — (See Circuit, 
Single- Wire.) 

Siiiistrorsal Solenoid or Helix. — (See So- 
le?ioid, Sinistrorsal.) 

Sinuous Currents. — (See Current, Sinu- 
ous^) 

Siphon, Electric — A siphon in 

which the stoppage of flow, due to the 
gradual accumulation of air, is prevented by 
electrical means. 

In the electric siphon, an opening is provided 
at the highest part of the bend of the siphon tube, 
and a chamber is attached thereto, provided with 
a float. Contact points are so connected with the 
float that when it falls, contact is made, and when 
it rises, contact is broken. 

The closing of the circuit, on the fall of the 
float, operates an electric motor which drives an 
air pump which exhausts the air from the siphon. 
Or the float being raised in the siphon, the con- 
tact is broken and the operation of the pump is 
stopped. 

Siphon Recorder. — (See Recorder, Si- 
phon.) 

Sir William Thomson's Standard Cell. — 

(See Cell, Voltaic, Standard, Sir William 
Thomson's?) 

Skin Effect— (See Effect, Skin.) 

Skin, Faradization of The thera- 
peutic treatment of the skin by a faradic cur- 
rent. 

For efficient faradization the skin should be 
thoroughly dried and a metallic brush or elec- 
trode employed. For very sensitive parts, as, 
for example, the face, the hand of the operator, 
first thoroughly dried, is to be preferred as an 
electrode.. 

Skin, Human, Electric Resistance of 

— The electric resistance offered by the 
skin of the human body. 

The electric resistance of the skin is subject to 
marked differences in different parts of the body, 
where its thickness or continuity varies. It 
varies still more with variations in its condition of 
moisture. Even in the same individual the re- 
sistance varies materially under apparently 
similar conditions. 

Sleeve, Insulating A tube of treated 

paper or other insulating material, provided 



for covering a splice in an insulated con- 
ductor. 

Sleeve Joint. — (See Joint, Sleeve.) 

Sleeve, Lead A lead tube provided 

for making a joint in a lead-covered cable. 

Sled. — The sliding contacts drawn after a 
moving electric railway car through the slotted 
underground conduit containing the wires or 
conductors from which the driving current is 
taken. 

Slide Bridge.— (See Bridge, Electric, 
Slide Form of.) 

Slide, Resistance A rheostat, in 

which the separate resistances or coils are 
placed in or removed from a circuit by means 
of a sliding contact or key. 

Apparatus employed in telegraphy for 
charging a conductor to a given fraction of 
the maximum potential of the battery so as 
to adjust its charge in order to balance the 
varying charge of a cable. 

The resistance slide consists essentially of a set 
of resistance coils of high insulation and of equal 
resistance. Suppose, for example, ten such equal 
coils to be connected in series, then if connected 
to the charging battery the potential will vary by 
one-tenth at the junction between each pair. A 
condenser, therefore, will be charged to any 
number of tenths of the potential of the charging 
battery by connecting it at suitable points. 

A second set of coils of equal resistance is ar- 
ranged so as to subdivide any of the lower coils, 
thus permitting an adjustment to within a hun- 
dredth of the potential of the battery. 

Slide Wire.— (See Wire, Slide.) 

Sliding Contact. — (See Contact, Sliding.) 

Slow-Speed Electric Motor. — (See Motor, 
Electric, Slow-Speed?) 

Sluggish Magnet— (See Magnet, Slug- 
gish^ 

Small Calorie. — (See Calorie, Small?) 

. Smee Voltaic Cell. — (See Cell, Voltaic^ 
S?nee.) 

Smelting, Electro The separation 

or reduction of metallic substances from their 
ores by means of electric currents. 



Sna.] 



479 



[Sol. 



Snap Switch. — (See Switch, Snap.) 
Soaking-In. — A term sometimes employed 
by telegraphers to represent the gradual 
penetration of an electric charge by a neigh- 
boring dielectric. 

An electric displacement occurs in the neigh- 
boring dielectric, and produces thereby what is 
generally called the residual charge. 

Soaking-Ont. — A term sometimes em- 
ployed by telegraphers to represent a gradual 
discharge which occurs in the case of a 
charged conductor in a neighboring dielec- 
tric. 

When a condenser, or other similar conductor, 
is discharged, the discharge is not instantaneous. 
The charge which soaked in, gradually recovers, 
or soaks- out. 

Socket, Electric Lamp A support 




Fig. 503. Lamp Socket. 

for the reception of an incandescent electric 
lamp. 

Incandescent lamp sockets are generally made 
so that the mere insertion of the base of the lamp 




Fig. J04. Lamp Socket. 

in the socket completes the connection of the lamp 
terminals with the terminals of the socket. The 



socket terminals are connected with the leads that 
supply current to the lamp; the removal of the 
lamp from the socket automatically breaks its cir- 
cuit. The socket is generally provided with a key 
for turning the lamp on or off without removing 
it from the socket. 

Figs. 503 and 504 show forms of lamp sockets 
for incandescent lamps and the details of the key 
for connecting or disconnecting the lamp with the 
leads. 

Socket, Wall A socket placed in a 

wall and provided with openings for the inser- 
tion of a wall plug with which the ends of a 
flexible twin-lead are connected. 

A wall-socket permits the temporary connec- 
tion of a portable electric lamp, a push button or 
other device with the conductor or lead. 

Soft-Drawn Copper Wire. — (See Wire, 
Copper, Soft-Drawn) 

Soldering, Electric A process for 

obtaining metallic joints, in which heat gen- 
erated by the electric current is used to melt 
the solder in the place of ordinary heat. 

Solenoid. — A cylindrical coil of wire the 
convolutions of which are circular. 

An electro-magnetic helix. (See Solenoid, 
Electro-Magnetic, or Electro-Magnetic 
Helix.) 

A solenoid is termed dextrorsal or sinistrorsal 
according to the direction in which its wire is 
wound. (See Solenoid, Dextrorsal. Solenoid, 
Sinistrorsal.) 

Solenoid Core. — The core, usually of soft 
iron, placed within a solenoid and magnetized 
by the magnetic field of the current passing 
through the solenoid. 

The soft iron core of a solenoid differs from 
that of an electro-magnet in the fact that the core 
of the solenoid is movable, while that of the elec- 
tro-magnet is fixed. (See Magnet, Electro.) 

In order to obtain a nearly uniform pull in its 
various positions in the solenoid, the soft iron cores 
are made of a shape which insures a greater mass 
of metal towards the middle of the core. (See 
Ears, Krizik's.) 

Solenoid, Dextrorsal A solenoid 

in which the winding is right-handed. (See 
Solenoid, Practical.) 

Solenoid, Electro-Magnetic, or Electro- 
Magnetic Helix The name given to 



Sol. 



480 



[Sol, 



a cylindrical coil of wire, each of the convo- 
lutions of which is circular. 

A circuit bent in the form of a helix, supported 
at its two extremities, as shown in Fig. 505, and 
traversed by an electric current, will move into 
the magnetic meridian of the place, and, if free to 
move in a vertical plane, will come to rest in the 
line of the magnetic inclination or dip of the place. 

A solenoid traversed by an electric current ac- 
quires thereby all the properties of a magnet, and 
is attracted and repelled by other magnets. Its 
poles are situated at the ends of the cylinder on 
which the solenoid may be supposed to be wound. 

Solenoid, Ideal A solenoid con- 
sisting of a cylinder built up of a number of 
true circular currents, with all faces of like 
polarity turned in the same direction and 
entirely independent of one another. 

The practical solenoid differs from the ideal 
solenoid in that the successive circular circuits or 
currents are all connected with one another in 
series. 

The polarity of a solenoid depends on the direc- 
tion of the current as regards the direction in 
which the solenoid is wound. 

This solenoid is sometimes called an electro- 
magnetic solenoid or helix, in order to distinguish 




Fig, 505. Practical Solenoid. 

it from a solenoidal magnet. (See Magnet, Sole- 
noidal. ) 
A solenoid, if suspended so as to be free to 



move, will come to rest in the plane of the mag- 
netic meridian when traversed by an electric 
current. 

It will also be attracted or repelled by the ap. 
proach of a dissimilar or similar magnet pole 
respectively, as shown in Fig. 505. 

Solenoid, Left-Handed A sinistror- 

sal solenoid or one in which the winding is 
left-handed. (See Solenoid, Practical.) 

Solenoid, Magnetic A spiral coil 

of wire which acts like a magnet when an 
electric current passes through it. 

The magnetic solenoid must be distinguished 
from a solenoidal magnet. (See Magnet, Sole- 
noidal. Solenoid, Electro-Magnetic, or Electro- 
Magnetic Helix.') 

Solenoid, Practical The name ap- 
plied to the ordinary solenoid in order to dis- 
tinguish it from the ideal solenoid. (See 
Solenoid, Ideal) 

A Practical Solenoid consists, as shown in Figs. 




'Fig. JO 6. Practical Solenoid. 
505 and 506, of a spiral coil of wire in which the 
successive circular circuits are connected to one 
another in series. 




Fi g>5<>7. Rig ht- Handed HeUx. Fig. so 8. Left-Handed 
Helix. Fig. joo. Helix, with Consequent Poles. 

The polarity of the solenoid depends on the 
direction of the current, and therefore on the 
direction of winding. In any solenoid, however, 
the polarity may be reversed by reversing the 
direction of the current. (See Magnet, Electro.) 

A Right -Handed, or Dextrorsal Solenoid, is one 
wound in the direction shown in Fig. 507 at I. 



Sol.] 



481 



[Sou. 



A Left-Handed, or Sinistrorsal Solenoid, is one 
wound in the direction shown in Fig. 508 at 2. 

The solenoid shown in Fig. 509 at 3, is wound 
so as to produce consequent poles. (See Poles, 
Consequent. ) 

Solenoid, Right-Handed A dex- 

trorsal solenoid, the winding in which is right- 
handed. (See Solenoid, Practical?) 

Solenoid, Sinistrorsal A solenoid 

in which the winding is left-handed. (See 
Solenoid, Practical.) 

Solenoidal. — Pertaining to a solenoid. 

Solid Angle. — (See Angle, Solid.) 

Solid Line.— (See Line, Solid.) 

Solution. — A liquid in which another sub- 
stance, generally a solid, is dissolved. 

The liquid may contain either a solid, another 
liquid, or a gas. 

Solution, Bain's Printing" — The 

solution used in Bain's chemical telegraph. 

Bain's solution is made by mixing together one 
part of a saturated solution of potassium ferro- 
cyanide, with two parts of water. 

Solution, Battery The exciting 

liquid for voltaic cells. (See Cell, Voltaic.) 

Solution, Chemical, Bain's A solu- 
tion employed in connection with Bain's re- 
cording telegraph. (SeePecorder, Chemical, 
Bain's?) 

Solution, Quicking A solution of 

a salt of mercury, in which objects to be elec- 
tro-plated are dipped after cleansing, just 
before being placed in the plating bath. 

If the articles have been properly cleansed, im- 
mersion in the quicking solution will cover them 
with a uniform, silver-like coating, which will in- 
sure an adherent, uniform coating in the plating 
bath. 

Solution, Saturated A solution in 

which as much of the solid or other substance 
has been dissolved in the liquid as it will take 
at a given temperature. 

Solution, Super-Saturation of 

The condition assumed by a warmed satu- 
rated solution of a salt, when placed in a 
closed vessel out of contact with the air, and 
allowed to cool without being shaken. 

Under the above circumstances the solution 
may be cooled without depositing any crystals. 



Such a solution is said to be super-saturated. It 
will immediately deposit crystals if a crystal of the 
salt dissolved or a crystal of an isomorphous salt 
be dropped in the solution, or often if merely 
shaken. 

It is important in standard voltaic cells in 
which zinc sulphate is used, that the solution be 
saturated but not super- saturated. 

Sonometer, Hughes' An apparatus 

for determining the amount of inductive dis- 
turbance in an induction balance, by compar- 
ing the sounds heard in a telephone, as 
a result of such induction, with the sounds 
heard in the same telephone under circum- 
stances in which the amount of disturbance 
is directly measurable. 

An apparatus devised by Professor Hughes to 
be used in connection with the induction balance, 
in order to measure the amount of disturbance of 
balance produced therein in any particular case. 

Sonorescence. — A term proposed for the 
sounds produced when a piece of vulcanite or 
any other solid substance is exposed to a 
rapid succession of flashes of light. (See 
Photophone?) 

Sound. — The sensation produced on the 
brain, through the ear, by the vibrations of a 
sonorous body. 

The sound waves that are capable of pro- 
ducing the sensation of sound on the brain 
through the ear. 

The word sound is therefore used in science in 
two distinct senses, viz.: 

( 1 . ) Subjectively, as the sensation produced by 
the vibrations of a sonorous body. 

(2.) Objectively, as the waves or vibrations that 
are capable of producing the sensation of sound. 

Sound is transmitted from the vibrating body 
to the ear of the hearer by means of alternate to- 
and-fro motions in the air, occurring in every 
direction around the vibrating body and forming 
spherical waves called waves of condensation and 
rarefaction. Unlike light and heat, these waves 
require a tangible medium such as air to trans- 
mit them. 

Sound, therefore, is not propagated in a 
vacuum. The vibrations of sound are longi- 
tudinal, that is, the to-and-fro motions occur in 
the same direction as that in which the sound is 
traveling. The vibrations of light are transverse, 



Sou.] 



482 



[Sou. 



that is, the to- and -fro motions are at right angles 
to the direction in which the light is traveling, 

Sound. — (Objectively.) The waves in the 
air or other medium which produce the sen- 
sation of sound. 

Sound.— (Subjectively.) The effect pro- 
duced on the ear by a vibrating body. 

Sound, Absorption of Acoustic ab- 
sorption. (See Absorption, Acoustic) 

Sound, Characteristics of The 

peculiarities that enable different musical 
sounds to be distinguished from one another. 

The characteristics of musical sounds are: 

(i.) The Tone or Pitch, according to which a 
sound is either grave or shrill. 

(2.) The Intensity or Loudness, according to 
which a sound is either loud or feeble. 

(3.) The Quality or Timbre, the peculiarity 
which enables us to distinguish between two 
sounds of the same pitch and intensity, but 
sounded on different instruments, as for example, 
on a flute and on a piano. 

Sound, Quality or Timbre of That 

peculiarity of a musical note which enables 
us to distinguish it from another musical note 
of the same tone or pitch, and of the same 
intensity or loudness, but sounded on another 
instrument. 

The middle C, for example, of a pianoforte, is 
readily distinguishable from the same note on a 
flute, or on a violin ; that is to say, its quality is 
different. The differences in the quality of musi- 
cal sounds are caused by the admixture of addi- 
tional sounds called overtones which are always 
associated with any musical sound. 
', Briefly, nearly all so-called simple musical 
sounds are in reality chords or assemblages of a 
number of different musical sounds. 

In the case of the many different notes that are 
present in an apparently simple note or tone, one 
of the notes is far louder than all the others and is 
called the fundamental tone or note, and is what 
is recognized by the ear as the note proper. The 
others are called the overtones. The overtones 
are too feeble to be heard very distinctly, but 
their presence gives to the fundamental note its 
own peculiar quality. In the case of a note 
sounded on the flute, these overtones are dif- 
ferent either in number or in their relative intensi- 
ties from the same note sounded on another instru- 



ment. Their fundamental tones, however, are 
the same. 

The peculiarities which enable us to distinguish 
the voice of one speaker or singer from another 
are due to the presence of these overtones. The 
overtones must be correctly reproduced by the 
diaphragm of the telephone, or phonograph, 
graphophone, or gramophone, if the articu'iate 
speech is to be correctly reproduced witn all its 
characteristic peculiarities. 

Sounder, Morse Telegraphic An 

electro-magnet which produces audible 
sounds by the movements of a lever attached 
to the armature of the magnet. 

The Morse sounder has now almost entirely 
supplanted the paper recorder or register. On 
short lines it is placed directly in the telegraphic 
circuit. On long lines it is operated by a local 
battery, thrown into or out of the action by the 
relay. (See Relay.) 




Fig. 5 to. Morse Sounder. 

The Morse sounder, shown in Fig. 510, con- 
sists of an upright electro-magnet M, whose soft 
iron armature A, is rigidly attached to the striking 
lever B, working in adjustable screw pivots as 
shown. The free end of the lever is limited in its 
strokes by two set screws N, N. The lower of 
these screws is set so as to limit the approach of 
the armature A, to the poles of the electro-magnet; 
the upper screw is set so as to give the end B, 
sufficient play to produce a loud sound. A re- 
tractile spring, attached to the striking lever near 
its pivoted end, and provided with regulating 
screw S S, pulls the lever back when the current 
ceases to flow through M. 

The dots and dashes of the Morse alphabet are 
reproduced by the sounder, as audible signals, 
that are distinguished by the operator by means 
of the different sounds produced by the up and 
down stroke of the lever as well as by the differ 



Sou.] 



483 [Sou. 



ence in the intervals of time between the succes- 
sive signals. 

Another form of telegraphic sounder, similar 
in its general construction to that already de- 
scribed, is shown in Fig. 511. 




Fig. 511. Telegraphic Sounder. 

Sounder, Repeating A telegraphic 

sounder which repeats the telegraphic dis- 
patch into another circuit. 

Sounds, Magnetic Faint clicks 

heard on the magnetization of a readily mag- 
netizable substance. 

One of the earlier forms of Reis' telephone, 
operated by means of a rapid succession of these 
faint magnetic sounds. 

Source, Electric Any arrangement 

capable of maintaining a difference of poten- 
tial or an electromotive force. 

The following are the more important electric 
sources, arranged according to the character of 
the energy which is converted into electric 
energy. 



Electric Sources. 



1. Voltaic Cell or Primary 

Battery. 

2. Charged Storage Cell or 

Secondary Battery. 

3. Thermo Cell or Thermo 

Battery. 

4. Selenium Cell or Sele- 

nium Battery. 

5. Magneto - Electric 

chine. 

6. Dynamo-Electric 

chine. 

Frictional Electric 
chine. 

Electrostatic Induction 
Machine. 

Magneto-Electric Tele- 
phone Transmitter. 

Heat and Mechan- 
ical Energy. 

Animal or Plant Vital Energy. 



7- 



Ma- 
Ma- 
Ma- 



Chemical Poten- 
tial Energy. 



Radiant Energy. 



Mechanical 
Energy. 



10. Pyromagnetic Generator. 



Sources, Multiple-Arc-Connected 

A term sometimes applied to sources connect- 
ed in multiple. (See Sources, Multiple-Con- 
nected) 
Sources, Multiple-Connected The 

connection of a number of separate sources 
so as to form a single source by joining the 
positive poles of all the separate sources to a 
single positive lead or conductor, and all the 
negative poles to a single negative lead or 
conductor. 

The multiple connection of sources results in 
each of the sources discharging its current into 
the main conductor in a direction parallel to 
that of the other sources. 

The electromotive force in the same is that of 
any single source, but the resistance of the com- 
bined source decreases with each source added. 
Supposing the resistance of each source be the 
same, then if ten such sources are connected in 
multiple-arc, the resistance of the combined source 
is but one-tenth the resistance of a single source. 
(See Circuit, Multiple.) 

Sources are combined in multiple-arc whenever 
the current furnished by the separate sources is 
insufficient to properly operate the electro-recep- 
tive or translating device with which it is con- 
nected. 

Sources, Multiple-Series-Connected 

— The conection of a number of separate 
sources so as to form a single source by con- 
necting a number of the sources in groups 
in series, and joining these groups together 
in multiple-arc. 

The battery of sources obtained by connecting 
a number of separate sources in multiple-series 
will have an electromotive force equal to the 
sum of the separate electromotive forces of the 
sources connected in any of the separate series- 
connected groups. 

The current produced will be greater in propor- 
tion to the number of separate groups in parallel. 
The internal resistance will be increased in pro- 
portion to the number of coils in series, and de- 
creased in proportion to the number of groups in 
multiple-arc or parallel. 

Sources are connected in multiple-series when 
both the electromotive force and the current of 
any single source are insufficient to operate the 
electro-receptive or translating device. (See 
Circuit, Multiple- Series . ) 



Sou.] 



484 



[Spa. 



Sources, Parallel ■ Connected A 

term sometimes applied to multiple-connected 

sources. (See Sources, Multiple-Connected) 

Sources, Series-Connected The 

connection of a number of separate electric 
sources so as to form a single source, in 
which the separate sources are placed in a 
single line or circuit by so connecting their op- 
posite poles that the current produced in each 
passes successively through each of the 
sources. 

The series-connection of sources results in an 
electromotive force equal to the sum of the sepa- 
rate electromotive forces produced by each 
source— that is, a rise of potential occurs with each 
source added. This connection increases the re- 
sistance of the circuit by the amount of the resist- 
ance of each source introduced into the circuit. 
The value of the resulting current depends on the 
total electromotive force and resistance of the 
series- connected sources. 

Sources are connected in series when the 
electromotive force furnished by a single source 
is insufficient for the character of work required 
to be done. (See Circuit, Series.) 

Sources, Series-Multiple-Connected 

— The connection of a number of separate 
electric sources, so as to form a single source, 
in which the separate sources are connected 
in a number of separate multiple groups or 
circuits, and these groups or circuits separ- 
ately connected together in series. (See Cir- 
cuit, Series-Multiple) 

Southern Light. — A name sometimes given 
to the Aurora Australis. (See Aurora Aus- 
tralis.) 

Space, Clearance The space be- 
tween the revolving armature of a dynamo- 
electric machine, or electric motor, and the 
polar faces of the pole pieces, 

Space, Dark, Crookes' A dark 

space surrounding the negative electrode in a 
rarefied space through which electric dis- 
charges are passing. 

Crookes' dark space lies immediately between 
the negative electrode and its glow or luminous 
discharge. It differs, therefore, from Faraday's 
dark space, which lies between the luminous dis- 
charges of the negative and positive electrodes. 



The radius of Crookes' dark space increases 
with the degree of exhaustion. It varies also 
with the character of the residual gas, with the 
temperature of the negative electrode, and some- 
what with the intensity of the spark. When the 
vacuum becomes sufficiently high, the dark space 
fills the entire tube through which the discharges 
are passing. 

Crookes has found that in the case of substances 
that become phosphorescent under the electric 
discharge, phosphorescence best takes place when 
the body is placed on the boundary of the dark 
space. 

Space, Dark, Faraday's — The gap 

in the continuity of the luminous discharges 
that occurs between the glow of the positive 
and negative electrodes. 

Faraday's dark space is seen in a partially ex- 
hausted tube through which the discharges of 
an induction coil are passing. It occurs in as 
low a vacuum as 6 millimetres of mercury. 
As the vacuum becomes higher, the length of the 
dark space increases. 

Space, Inter-Air A term some- 
times employed for the air space between the 
outer surface of the revolving armature of a 
dynamo-electric machine and the adjacent 
faces of the pole pieces. (See Space, Clear- 
ance.) 

Space, Interferric A term some- 
times used for air gap. (See Gap, Air.) 

Span Wire. — (See Wire. Span) 

Spark Coil. — (See Coil, Spark) 

Spark Gap. — (See Gap, Spark) 

Spark, Length of The length of 

spark that passes between two charged con- 
ductors depends : 

(i.) On the difference of potential between 
them. 

(2.) On the character of the gaseous medium 
that separates the two conductors. 

(3.) On the density or pressure of the gaseous 
medium between the conductors. 

Up to a certain pressure, a decrease in the 
density causes an increase in the length of the 
distance the spark will pass, When this limit is 
reached, a further decrease of density decreases 
the length of spark. A high vacuum prevents 
the passage of a spark even under great differ- 
ences of potential. 



Spa.] 



485 



[Spa. 



(4.) On the kind of material that forms the 
electrodes between which the charges pass. 

(5.) On the shape of the charged conductor. 

(6. ) On the direction of the current. 

Sparks from the prime conductor are denser 
and more powerful than those from the negative 
conductor. 

It will be observed that the length of the spark 
practically depends mainly on two circumstances, 
viz., on the differences of potential of the oppo- 
site charges, and the conducting power of the 
medium that separates the two bodies. 

Spark, T-Shaped — A variety of 

three-branched spark obtained by the dis- 
charge of a Leyden jar through a peculiar 
form of induction coil. (See Spark, Three- 
Branched) 

Spark, Three-Branched A pecu- 
liar form of branched spark obtained by the 
discharge of a Leyden jar through a peculiar 
form of induction coil. 

The three-branched spark was obtained by 
Elihu Thomson by the use of the following appa- 
ratus: The discharges of a Leyden jar, charged by 
a Topler-Holtz machine, were sent through an in- 
duction coil, the primary and secondary of which 
L 




OP.O 




Fig, 512. Apparatus for Three-Branched Sparks. 
were of few turns. The circuit connections were 
as shown in Figs. 512 and 513, and the apparatus 
is described by Thomson as follows: 

"A double coil was made, Fig. 512, in which 
the inner turns were about twelve and the outer 
turns twenty. These were kept separate from each 
other and a branch wire taken from the line and 
slid from point to point on the outer wire enabled 
the effective length of the same to be adjusted. 
The inner coil was connected through a small 
spark gap, as at A, to the outer coating of a Ley- 
den jar, while the wire L, was brought near the 
pole of the jar, which was continually being 



charged from a Ttfpler-Holtz machine. The 
discharge, in passing from the knob of the jar to 
the wire L, representing the line, passed by the 



OPQ 




Fig. 313. Apparatus/or T and Y Shaped Sparks. 

inner coil. When a certain length of the outer 
coil was employed, only a very short, almost im- 
perceptible spark was obtainable at a. If the 
balance of the turns were disturbed by including 
more or less than the proper number of the outer 
turns, not only did a vigorous spark occur, but 
the gap at a, could be quite considerably extended, 
in accordance with the amount of departure taken 
from the proper number of turns required to pro- 
duce the balance. This ex- 
periment indicates that it is 
possible to make a selective 
path for the Leyden jar dis- 
charge, and to have a struc- 
ture so proportioned that 
the discharges reaching line 
will pass to earth without Fi £- 
tending to go through the cir- 
cuit of the dynamo. The action is apparently 
due to a balance of electromotive forces such 
that the discharge which tends to pass from the 
line in going to earth induces in the coil con- 
nected to the dynamo a counter electromotive 
force which nearly wipes out the potential of the 
discharge before it reaches the dynamo. This 
balance of inductive effects is certainly very strik- 
ing, and once obtained, it is disturbed, as, in the 
experiments, by changing the relative lengths of 
the coils in inductive relation through so small 
an amount as an inch or two. 

" It may be mentioned here that some curious 




St 4. Three- 
Branched Sparks. 



Spa.] 



486 



[Spe. 



effects of spark were obtained in these experi- 
ments. When a disturbance of the balance ex- 
ists and a spark is obtained at a, the character of 
the spark is different from that of the Ley den jar 
discharge. It appears to be less luminous, the 
noise less sharp, and its color would indicate a 
greater power of volatilizing metal and perhaps a 
greater duration. It is in part, no doubt, due to 
a current local to the coils in series with one an- 
other. 

' ' Another curious effect was the production of 
T-shaped and Y" sna P e d sparks, or three- 
branched sparks (such as are shown in Figs. 513 
and 514.)" 

" These were obtained by separating the elec- 
trodes at A, an inch and a half or thereabouts, 
and bringing the third electrode from the outer 
coiLto the position shown in Fig. 513. The dis- 
charges were now obtained as before from the 
charged jar. In this case the discharge appears 
to split and unite in air, producing the curious 
shaped sparks shown. It would seem that to ob- 
tain these effects — particularly the sparks which 
were three- branched from a common point in the 
centre between the discharge electrodes— the 
dielectric air must break down simultaneously be- 
tween the three electrodes. It would easily ex- 
plain the "|"- s ^ a P es to assume the straight part 
above to form first, and the cross or transverse 
spark to strike from the side of this spark to the 
third electrode." 

Spark Tube.— (See Tube, Spark) 

Spark, Wipe In an electric gas- 
lighting pendant burner, a spark obtained 
from a spark coil by the wiping contact of a 
spring, moved by the pulling of the pendant. 
(See Burner, Ratchet-Pe?idant, Electric) 

Spark, Y-Shaped— A variety of three- 
branched spark obtained by the discharge of 
a Leyden jar through a peculiar form of induc- 
tion coil. (See Spark, Three-Branched) 

Sparking Discharge. — (See Discharge, 
Disruptive) 

Sparking Distance.— (See Distance, 
Sparking) 

Sparking, Line of Least The line 

on a commutator cylinder of a dynamo con- 
necting the points of contact of the collecting 
brushes where the sparking is a minimum. 

In some forms of dynamos the line of least 



sparking lies parallel to the lines of magnetic 
force of the field. 

In most forms, however, it is at right angles to 
such lines. The exact position of all these lines 
is changed by the angular lead of the brushes. 
(See Lead, Angle of.) 

Sparking of Dynamo-Electric Machine.— 

(See Machine, Dynamo-Electric, Sparking 
of) 

Spar Torpedo.— (See Torpedo, Spar) 

Spasmodic Governor. — (See Governor, 
Spasmodic) 

Speaking-Tube Annunciator. — (See An- 
nunciator, Oral or Speaking- Tube) 

Speaking-Tube Mouth Piece, Electric 

Alarm A mouth piece for a speaking 

tube, so arranged, that the movement of a 
pivoted plate covering the mouth piece au- 
tomatically rings a bell at the other end of 
the tube. 

Specific Conduction Resistance. — (See 
Resistance, Specific Conduction) 

Specific Conductivity. (See Conduc- 
tivity, Specific) 

Specific Heat. — (See Heat, Specific) 

Specific Heat of Electricity.— (See Elec- 
tricity, Specific Heat of) 

Specific Hysteresial Dissipation. — (See 
Dissipation, Specific Hysteresial) 

Specific Inductive Capacity. — (See Ca- 
pacity, Specific Inductive?) 

Specific Magnetic Capacity. — (See Ca- 
pacity, Specific Magnetic) 

Specific Magnetic Conductivity.— (See 
Conductivity, Specific Magnetic) 

Specific Magnetic Inductivity.— (See In- 
ductivity, Specific Magnetic) 

Specific Resistance. — (See Resistance, 
Specific) 
Specific Resistance of Liquids.— (See 

Resistance, Specific, of Liquids) 

Speech, Articulate The successive 

tones of the human voice that are necessary 
to produce intelligible words. 

The phrase articulate speech refers to the join- 
ing or articulation of the successive sounds in- 
volved in speech. The receiving diaphragm of a 



Spe.] 



487 



[Spo. 



telephone is caused to reproduce the articulate 
speech uttered near the transmitting diaphragm. 

Speed, Critical, of Compound-Wound 

Dynamo The speed at which both the 

series and shunt coils of the machine give the 
same difference of potential when the full load 
is on the machine, as the shunt coil would if 
used alone on open-circuit. 

Speed Indicator. — (See Indicator, Speedy 

Speeding. — Varying the number of revolu- 
tions per minute. 

The speeding of a dynamo is for the purpose 
of obtaining the current requisite to properly 
operate the electro-receptive device placed in its 
circuit. 

Spent Acid. — (See Acid, Spent?) 

Spent Liquor. — (See Liquor, Spent) 

Spherical Armature. — (See Armature, 
Spherical) 

Sphygmogram. — A record made by a 
sphygmograph. (See Sphygmograph) 

Sphygmograph. — An instrument for re- 
cording the peculiarities of the normal or 
abnormal pulse. 

Sphygmograph, Electrical An in- 
strument for electrically recording the peculi- 
arities of the pulse. 

Sphygmophone. — An apparatus in which 
a microphone is employed for the medical 
examination of the pulse. (See Microphone) 

Spider, Armature A light frame- 
work or skeleton consisting of a central sleeve 
or hub keyed to the armature shaft, and pro- 
vided with a number of radial spokes or arms 
for fixing or holding the armature core to 
the dynamo-electric machine. 

Spider, Driving Radial arms or 

spokes connected to the armature of a dynamo- 
electric machine and keyed to the shaft so as 
to act as a driving wheel for the armature. 

Spin, Magnetic A term sometimes 

employed instead of magnetic field. 

The term magnetic spin is sometimes used in- 
stead of magnetic field because the magnetism is 
now generally believed to be due to the effects of 
a rotary motion or spin in the surrounding uni- 
versal ether. 



Spiral, Primary The primary of an 

induction coil or transformer. (See Trans- 
former, Coil, Induction) 

Spiral, Koget's A suspended wire 

spiral conveying a strong electric current and 
devised to show the attractions produced by 
parallel currents flowing in the same direc- 
tion. 

The lower end of the wire spiral dips into a 
mercury cup. On the passage of the current, the 
attraction of the neighboring turns of the spiral 
for each other shortens the length of the spiral 
sufficiently to draw it out of the mercury and thus 
break the circuit. When this occurs the weight 
of the spiral causes it to fall and again re-estab- 
lish the circuit. A rapid automatic-make-and- 
break is thus established, accompanied by a brill- 
iant spark at the mercury surface due to the ex- 
tra spark on breaking. 

Spiral, Secondary The secondary 

coil of an induction coil or transformer. (See 
Transformer. Coil, Induction) 

Splice Box.— (See Box, Splice) 
Split Battery.— (See Battery, Split) 
Split Lead Tee.— (See Tee, Split Lead?) 
Spluttering of Arc. — (See Arc, Splutter- 
ing of) 

Spots, Sun Dark spots., varying in 

number and position, which appear on the 
face of the sun and are believed by some to be 
caused by huge vortex motions in the masses 
of glowing gas that surround the sun's body. 
Sun spots occur in greater number at intervals 
of about every eleven years. 

Their occurrence is generally attended with 
unusual terrestrial magnetic variations. (See 
Storm, Magnetic) 

In the opinion of most astronomers the sun 
spots mark depressions in the atmosphere of the 
sun. Their exact causes are unknown, though 
they appear to be dependent on a local cooling 
or condensation of the sun's atmosphere. 

When observed through a telescope the sun 
spot appears as a dark region surrounded by a 
less dark region. Though darker by contrast 
with tht rest of the sun's face, yet such spots are 
in reality much brighter than the most brilliant 
arc light. The outline of the sun spot is quite 
irregular. 



Spr.] 



488 



[Sta. 



Spreading-Out Magnetic Field. — (See 
Field, Magnetic, Spreading-Out?) 

Sprengel Mercury Pump. — (See Pump, 
Air, SprengeVs Mercurial?) 

Spring" Ammeter. — ( See Ammeter, 
Spring^ 

Spring* Contact. — (See Contact, Spring?) 

Spring, Hold-Off A spring which 

acts to keep one thing away from another in 
opposition to some force tending to keep it in 
contact with such a thing. 

Spring, Hold-On A spring which 

acts to keep one thing against another in op- 
position to some force tending to pull it 
away. 

A hold-on spring is sometimes employed in a 
dynamo-electric machine for the purpose of keep- 
ing the collecting brushes in proper pressure 
against the segments of the commutator. 

Spring-Jack. — A device for readily insert- 
ing a loop in a main electric circuit. The 
spring-jack is generally used in connection 
with a multiple switch board. (See Board, 
Multiple Switch?) 

Spring-Jack Gut-Out. — (See Cut-Out, 
Spring-Jack?) 

Spurious Hall Effect,— (See Effect, Hall, 
Spurious?) 

Spurious Resistance. — (See Resistance, 
Spurious?) 

Stabile Galvanization.— (See Galvaniza- 
tion, Stabile?) 

Staggering. — A term sometimes applied to 
the position of the brushes on a commutator 
cylinder, in which one brush is placed slightly 
in advance of the other brush so as to bridge 
over a break. 

When a break occurs in the circuit ot the arma- 
ture wires, the device of staggering the brushes is 
adopted for temporarily bridging over the break. 
When a break occurs, the rewinding of the arma- 
ture is the only radical cure. 

Standard Candle.— (See Candle, Stand- 
ard?) 



Standard Carcel Gas Jet. 

Carcel Standard?) 
Standard, Dynamo 



■(See Jet, Gas, 
-The supports 



for the bearings of a dynamo-electric ma- 
chine. 

Standard Earth Quadrant. — (See Quad- 
rant, Standard?) 

Standard of Self-induction, Ayrton & 

Perry's (See Induction, Self, Ayrtoii 

&* Perry s Sta?idard of.) 

Standard Ohm. — (See Ohm, Standard?) 

Standard, Pentane A standard 

source of light used in photometric measure- 
ments, in place of a Methven screen. 

The pentane standard is constructed in general 
in the same manner as the Methven standard. 
In place, however, of ordinary coal gas, a mixture 
of pentane and air is used. Pentane is a variety 
of coal oil left after several distillations of ordinary 
crude oil. It distills at a temperature not greater 
than 50 degrees centigrade. 

The mixture for burning consists of about 
twenty volumes of air to seven volumes of pen- 
tane. A burner of the pentane standard is some- 
what similar to the Methven standard, but differs 
in a number of minor details. 

Standard Resistance Coil. — (See Coil, 
Resistance, Standard?) 

Standard Size of Electrodes, Erh's 

— (See Electrodes, Erb's Standard Size of.) 

Standard Yoltaic Cell.— (See Cell, Voltaic, 
Standard?) 
Standard Yoltaic Cell, Clark's 

(See Cell, Voltaic, Standard, Clark's?) 

Standard Yoltaic Cell, Clark's, Rayleigh's 
Form of (See Cell, Voltaic. Stand- 
ard, Rayleigh's Form of Clark's?) 

Standard Yoltaic Cell, Fleming's 

(See Cell, Voltaic, Standard, Flemings.) 

Standard Yoltaic Cell, Lodge's 

(See Cell, Voltaic, Standard, Lodge s.) 

Standard Yoltaic Cell, Sir William 
Thomson's (See Cell, Voltaic, Stand- 
ard, Sir William Thomso?i's.) 

Standard Wire Gauge. — (See Gauge, 
Wire, Standard?) 



Sta.] 



489 



[Sta. 



Standardizing a Voltaic Cell. — (See Cell, 
Voltaic, Standardzzi7ig a.) 

Standards, Motor A name applied 

to the supports for the bearings of an electric 
motor. 

State, Allotropic A modification 

of a substance, in which, without changing 
its chemical composition, it assumes a condi- 
tion in which many of its physical and chem- 
ical properties are different from those it or- 
dinarily possesses. 

Thus the element carbon occurs in three widely 
different allotropic states, viz.: 

(i.) As charcoal, or ordinary carbon; 

(2.) As graphite, or plumbago; and 

(3.) As the diamond. 

State, Anelectrotonic The condi- 
tion of decreased functional activity which 
occurs in a nerve in the neighborhood of the 
anode or positive terminal of a source to 
whose influence it is subjected. (See Anelec- 
trotonusi) 

State, Electrotonic —A peculiar 

state supposed by Faraday to exist in a wire or 
other conductor, whereby differences of po- 
tential are produced by means of its move- 
ment through a magnetic field. 

In his early researches Faraday regarded this 
state as a necessary condition in which a wire or 
conductor must exist, prior to its movement 
through a magnetic field, in order to have a dif- 
ference of potential produced; but at a later day 
he abandoned this idea, and explained the true 
causes of electrodynamic induction. (See In- 
duction, Electro-Dynamic.) 

The term electrotonic state is to be carefully dis- 
tinguished from electrotonus, or the change pro- 
duced in the functional activity of a nerve by an 
electric current. (See Electrotonus.) 

State, Kathelectrotonic The con- 
dition of increased functional activity of a 
nerve in the neighborhood of the kathode or 
negative terminal of a source to whose in- 
fluence it is subjected. (See Kathelectro- 
tonus.) 

The kathelectrotonic state is one of the states 
or conditions of electrotonus or altered functional 
activity produced in a nerve by an electric cur- 
rent. (See Electrotonus.) 



State, Nascent —A term used in 

chemistry to express the state or condition of 
an elementary atom or radical just liberated 
from chemical combination, when it possesses 
chemical affinities or attractions more ener- 
getic than afterwards. 

According to Grothuss' hypothesis, during the 
decomposition of a chain of polarized molecules, 
such for example as in the case of hydrogen sul- 
phate, H 2 S0 4 , in a zinc-copper voltaic cell, the 
two atoms of hydrogen H s , liberated by the com- 
bination of the S0 4 , with an atom of zinc, Zn, pos- 
sess a stronger affinity for the S0 4 of the molecule 
next to it, than does its own H 2 , and thus liber- 
ates its two atoms of hydrogen, which in turn 
unite with the S0 4 , of the next molecule in the 
polarized chain, and this continues until the two 
atoms of hydrogen liberated from the last mole- 
cule in the chain are given off at the copper plate. 
(See Hypothesis, Grothuss'.) 

The peculiar properties characteristic of the 
nascent state of elements is doubtless due to 
the fact that the elements are then in a. free 
state, with their bonds open or unsatisfied, and 
therefore possess greater affinities than when they 
are united in molecules. Thus H — , H — , or 
atomic hydrogen, should possess different affinities 
than H — H, or molecular hydrogen. 

State, Passive The condition of a 

metallic substance in which it may be placed 
in liquids that would ordinarily chemically 
combine with it, without being attacked or 
corroded. 

It is very doubtful whether metallic bodies can 
be properly regarded as possessing an actual 
passive state. Iron, for example, which is one of 
the metals that is said to be capable of assuming 
this so-called passive state, can be placed in this 
condition by immersing it for a few moments in 
concentrated nitric acid, and subsequently wash- 
ing it. It will then, unlike ordinary iron, neither 
be attacked by concentrated nitric acid, nor will 
it precipitate copper from its solutions. This 
condition is now generally believed to be due to 
the formation of a thin coating of magnetic oxide 
on its surface. 

Many of the instances of the so-called passive 
state are simply cases of the well known electrical 
preservation of metals that form the negative 
element of a voltaic combination, under which 
circumstances the positive element only of the 



Sta.J 



490 



LSte 



voltaic couple is chemically attacked by the elec- 
trolyte. (See Cell, Voltaic. Metals, Electrical 
Protection of. ) 

State, Permanent, of Charge on Tele- 
graph Line The condition of the 

charge on a telegraph wire when the current 
reaching the distant end has the same 
strength as at the sending end. 

State, Variable, of Charge of Telegraph 

Line — The condition of the charge on 

a telegraph wire while the strength of the 
current is increasing up to the full strength 
in all parts. 

The duration of the variable state is directly as 
the length of the line, the electrostatic capacity 
and the total resistance. It is increased by leak- 
age, by static capacity and by the effects of the 
extra current. (See Currents, Extra.) 

Static Breeze. — (See Breeze, Static?) 

Static Electricity. — (See Electricity, 
Static?) 

Static Energy. — (See Energy, Static?) 

Static Hysteresis. — (See Hysteresis, 
Static?) 

Static Insulation. — (See Insulation, 
Static?) 

Static Magnetic Induction. — (See Induc- 
tion, Magnetic, Static?) 

Static Shock. — (See Shock, Static?) 

Statics. — The science which treats of the 
relations that must exist between the points 
of application of forces and their direction 
and intensity, in order that equilibrium may 
result. 

Statics, Electro That branch of 

electric science which treats of the phenome- 
na and measurement of electric charges. 

Some of the more important principles ot elec- 
trostatics are embraced in the following laws: 

(I.) Charges of like name, i. e., either positive 
or negative, repel each other. Charges ot unlike 
name attract each other. 

(2.) The forces of attraction or repulsion be- 
tween two charged bodies are directly propor- 
tional to the product ot the quantities of electricity 
possessed by the bodies and inversely proportional 
to the square of the distance between them. 



These laws can be demonstrated by the use of 
Coulomb's torsion balance. (See Balance, Cou- 
lo?nd 7 s Torsion.) 

Statics, Magneto That branch of 

magnetism which treats of magnetic attrac- 
tions and repulsions, the distribution of lines 
of magnetic force and other facts regarding 
fixed magnets. 

Station, Central A station, cen- 
trally located, from which electricity for light 
or power is distributed by a series of con- 
ductors radiating therefrom. 

Station, Distant A term applied by 

an operator to the distant end of the line in 
order to distinguish it from his own end. 

Station, Distributing A station 

from which electricity is distributed. 
A central station. 

Station, Home A term applied by 

an operator to his end of the line, in order to 
distinguish it from the other or distant sta^ 
tion. 

Station, Transforming In a system 

of distribution by transformers or converters 
a station where a number of transformers are 
placed, in order to supply a group of houses 
in the neighborhood. (See Transformer. 
Electricity, Distribution of, by Alternating 
Currents?) 

Stationary Floor Key. — (See Key, Sta- 
tionary Floor?) 

Stationary Torpedo. — (See Torpedo, Sta- 
tionary.) 

Stay Rods, Telegraphic Metal rods 

attached to a telegraph pole, and securely 
fastened in the ground in order to counteract 
the effects of a pull or tension on the poles. 
(See Pole, Telegraphic?) 

Stay rods should be used in all exposed situa- 
tions, or where the poles are exposed to severe 
strains. 

Steady Current. — (See Current, Steady?) 

Stearns* Relay Shunt.— (See Shunt, Re- 
lay, Stearns .) 

Steel, Qualities of, Requisite for Mag- 
netization — Qualities which must be. 



SteJ 



491 



[Sto- 



possessed by steel in order to permit it to per- 
manently retain a considerable magnetization. 

For the purposes of permanent magnetization 
steel should possess the following qualities: 

It should be hard and fine grained. Hard cast 
steel answers the purpose very well. Scoresby 
showed that an intimate relation exists between 
the quality of the iron from which the steel is 
made, and the ability of the steel to take and re- 
tain considerable magnetism. 

The steel should be hardened as high as possi- 
ble and the temper afterwards drawn by heat to 
a violet-straw color. Practice is not uniform in 
this respect, the exact color varying with the 
quality of the steel. 

An admixture with the steel of about y^ of one 
per cent, of tungsten is said to increase its mag- 
netic powers. 

Cast steel is not generally employed for mag- 
nets, wrought steel being generally preferred. 

Step-by-Step, or Dial Telegraphy.— (See 

Telegraphy, Step-by-Step?) 

Step-Down Transformer. — (See Trans- 
former, Step-Down?) 

Step-Up Transformer. — (See Transform- 
er, Step- Up?) 

Sterilization, Electric Sterilizing 

a solution by depriving it of whatever germs 
it may contain by means of electrical cur- 
rents. 

The following experiments were recently made 
on sterilization by means of electric currents: 
The fluid, with the culture, was placed in a glass 
test tube, wound about with a wire coil connected 
either with a dynamo or accumulator or other 
electric source. Some increase in temperature 
Fas made, but never over 98 Fahr. When a 
current 1. 25 volts, 2.5 amperes passed, a com- 
plete sterilization of Micrococus Prodigiosus oc- 
curred at the end of twenty-four hours. 

Blood and water containing pathogenic germs 
was sterilized in five to thirty minutes. The 
above described effects would appear to be mag- 
netic rather than electric. 

Sticking. — A word applied by telegraphers 
to the failure of the positive pole relay arma- 
ture to leave the magnet pole on the cessation 
of the current. 

In telegraphy., when from any cause a circuit 
is imperfectly broken by an operators key, or at 



the points of contact of a relay or other instru- 
ment, such failure is called sticking. When an arc 
is formed at the points of a relay where the local' 
circuit is made and broken, the relay ' ' sticks. ' ' 
The arc is caused by burning of the platinum 
points. Sticking may be a result of a too weak 
retractile spring. 

Stone, Hercules ■ — A name given by 

the ancients to the lodestone. (See Lode- 
stone?) 

Stool, Insulating A stool provided 

with insulating supports of vulcanite or other 
insulator, employed to afford a ready insulat- 
ing stand or support. 

Stop, Limiting A stop set so as to 

limit the motion of an electrically vibrating or 
oscillating bar to any predetermined extent. 

Such limiting stops are common on telegraphic 
and various other electrical apparatus. 

Stopping-Off. — A process employed in 
electro-plating, in which a metallic article, al- 
ready electro-plated over its entire surface, is 
electro-plated with another metal over certain 
parts only. 

The process of stopping-off consists of covering 
the parts which are to receive the metallic coat- 
ing, with various stopping-off varnishes. By this; 
means articles can be electro-plated on parts of 
their surfaces with gold and on the remainder 
with silver. The whole surface is first silvered 
and the portions intended to be afterwards gilded 
are then stopped- off and the object placed in the 
gilding bath. 

Stopping-Off Varnish. — (See Vamish y 
Stopping -Off.) 
Storage Battery.— (See Battery, Storage^ 
Storage Capacity of Secondary Cell. — 

(See Cell, Secondary or Storage, Capacity 
of-) 

Storage Cell.— (See Cell, Storage.) 

Storage of Electricity. — (See Electricity, 
Storage of.) 

Storm, Auroral A term sometimes 

employed to express an unusual prevalence 
of auroras. 

Storm, Electric An unusual con- 
dition of the atmosphere as regards the quan- 
tity of its free electricity. 



Sto.J 



492 



[Str. 



A thunder storm is a variety of electric storm. 
(See Storm, Thunder.) 

Storm, Magnetic Irregularities oc- 
curring in the distribution of the earth's 
magnetism, affecting the magnetic declina- 
tion, dip, and intensity. 

Magnetic storms have been observed to accom- 
pany auroral displays, and to be coincident with 
the occurrence of sun spots, or unusual outbursts 
of solar activity. 

The coincidence of magnetic storms and out- 
bursts of solar activity is unquestioned. Wolf, 
of Zurich, has shown by a comparison of nu- 
merous observations of sun spots, the unques- 
tioned correspondence, in the times of their 
greatest activity, which occur every n.i years, 
with the time of occurrence of an unusual number 
of sun spots. He has placed these results in the 
form of curves. Those shown in Fig. 515 are 
taken from observations at Paris and Prague. 
The full lines represent the periods of sun spots. 
The dotted lines the periods of magnetic storms. 




Fig. 515- Wolfs Sun Spot Numbers. 

Storm, Thunder A storm during 

which electrical discharges accompanied by 
thunder take place between two clouds or be- 
tween a cloud and the earth. (See Elec- 
tricity, Atmospheric. Storms, Thunder, 
Geographical Distribution of) 

Storms, Thunder, Geographical Dis- 
tribution of — The following general 

facts as to the geographical distribution of 
thunder storms, show the intimate relation 
between the frequency of thunder storms and 
the time and place of the condensation of 
• vapor. 

(1.) Thunder storms seldom, if ever, occur in 
the polar regions. 

This is probably because the rainfall in the 



polar regions results from the condensation of the 
vapor that was formed, in the equatorial or tem- 
perate regions, so that a considerable time 
elapses between the evaporation and condensa- 
tion. 

(2.) Thunder storms seldom, if ever, occur in 
rainless districts, owing probably to the absence 
of the condensation of vapor. 

(3.) Thunder storms are most frequent and 
violent in the equatorial regions, where the rain- 
fall results from the condensation of the vapor by 
the action of ascending currents, conveying the 
vapor almost immediately after its formation into 
the upper and colder regions of the atmosphere. 

(4.) Thunderstorms occur in regions beyond 
the tropics, at those seasons of the year when the 
rainfall results from the condensation of the vapor 
shortly after the time of its formation, viz., in the 
temperate zones in the hotter parts of the year. 

Straight-Line Trolley Hanger. — (See 
Ha7iger, Straight-Line Trolley.) 

Straightaway Bunched Cable. — (See 
Cable, Bunched, Straightaway) 

Strain, Dielectric The strained 

condition in which the glass, or other dielec- 
tric of a condenser, is placed by the charging 
of the condenser. 

The deformation of a body under the in- 
fluence of a stress. (See Stress.) 

The stress in this case, i. <?., the force produc- 
ing the deformation or strain, is the attraction of 
the opposite charges. This stress, in the case of 
a Leyden jar, is often sufficiently great to cause 
a rupture of the glass. 

Strain, Electro-Magnetic The de- 
formation produced by an electro-magnetic 
stress. (See Stress, Electro-Magnetic) 

Strain, Electrostatic, Optical A 

strain or deformation produced in a plate of 
glass, or other transparent solid, by subject- 
ing it to the stress of an electrostatic field. 
(See Stress, Electrostatic) 

To obtain the electrostatic stress, holes are 
drilled in the plate of glass, and wires from a 
Holtz machine or induction coil placed therein, 
the wires being separated by a thin layer of glass. 

The glass, on being traversed by a beam of 
plane polarized light, rotates the plane of polar- 
ization of the light in the same direction as the 
glass would if subjected to a strain in the direc- 



Str.] 



493 



[Str. 



Hon of the lines of electric force. (See Rotation, 
Magneto-Optic.) 

Strain, Magnetic The deformation 

produced in the air-gap between two dissimi- 
lar magnetic poles, or in any substance placed 
therein, by the stress of the lines of magnetic 
force bridging such gap. 

Strain, Optical A deformation or 

alteration of volume produced in a plate of 
glass, or other transparent medium, by the 
action of any stress. (See Strain, Electro- 
Magnetic. Strain, Electrostatic, Optical) 

Strain, Optical Electro-Magnetic 

A strain produced in a plate of glass or other 
transparent medium by placing it in a mag- 
netic field. (See Stress, Electro-Magnetic. 
Rotation, Magneto-Optic.) 

Optical strain, whether electrostatic or mag- 
netic, or even mechanical, often causes a medium 
to acquire the power of double refraction or ro- 
tary polarization. (See Refraction, Double, 
Electric. Rotation, Magneto-Optic.) 

Stranded Core of Cable.— (See Core, 
Stranded, of Cable) 

Stranded Line. — (See Line, Stranded) 

Strap Copper. — (See Copper, Strap) 

Straps and Climbers. — Devices employed 
by linemen for climbing wooden telegraph 
poles. 

Stratham's Electric Fuse. — (See Fuse, 
Electric, Strathain's) 

Stratification Tube. — (See Tube, Stratifi- 
cation) 

Stratified Discharge. — (See Discharge, 
Stratified) 

Stray Field. — (See Field, Magnetic, 
Stray.) 

Stray Power. — (See Power, Stray) 

Stream-Lines of an Escaping Fluid. — 
Lines which show the actual path of the 
particles of an escaping fluid. 

When the escape has reached a steady condi- 
tion, the stream-lines correspond to the flow lines. 

Streamers. — Pillars or parallel flashing 
columns of light frequently seen during the 
prevalence of an aurora. (See Aurora Bo- 
realist) 



Streamers, Auroral A term some- 
times applied to the flashing columns or pillars 
of light that are thrown out in the shape of 
streams, from portions of the sky during the 
prevalence of an aurora. (See Aurora Bo- 
realis) 

Streaming Discharge. — (See Discharge, 
Streaming) 

Streamlets, Current A theoretical 

conception of a series of parallel current 
streams or current filaments, flowing through 
a solid conductor. 

In the case of uniform distribution of an elec- 
tric current where the current density is the same 
for all areas of cross-section, these current stream- 
lets are all of the same strength. 

In the case of rapidly alternating currents, 
however, the current streamlets are of greater 
strength near the surface. When the rate of al- 
ternation is sufficiently great, they are almost 
entirely absent at the central parts. 

The conception of current streamlets is made 
in order to account for the increase in the resist- 
ance of a solid conductor through which rapidly 
alternating currents of electricity are passing. 
(See Currents, Simple-Periodic.) 

Streams, Convection Streams of 

electrified air or other gaseous or vaporous 
particles given off from the pointed ends of 
charged, insulated conductors. (See Con- 
vection, Electric.) 

Street Mains.— (See Main, Street) 

Street Service. — (See Service, Street) 

Strength, Field The intensity or 

total flux of magnetism of a dynamo. 

This term is also sometimes roughly used for 
the current strength in the field magnet circuit of 
a dynamo-electric machine. 

Strength of Current.— (See Ctirrent 
Strength) 

Strength of Magnetic Field. — (See Field, 
Magnetic, Strength of) 

Strength of Magnetism. — (See Mag7ietism, 
Strength of) 

Stress.— The pressure, pull, or other force 
producing a deformation or strain. 



Str. 



494 



[Sub. 



Stress, Dielectric The force pro- 
ducing the deformation or strain in a dielec- 
tric. 

A dielectric strain, in the case of a Ley den jar 
or condenser, is sometimes sufficiently great to 
pierce the dielectric. 

Stress, Electro-Magnetic The force 

or pressure in a magnetic field, which produces 
a strain or deformation in a piece of glass or 
other similar substance placed therein. (See 
Strain, Optical Electro-Magnetic?) 

Stress, Electrostatic The force or 

pressure in an electrostatic field, which pro- 
duces strain or deformation in a piece of glass 
or other substance placed therein. (See 
Strain, Electrostatic, Optical?) 

Stress, Energy of A term some- 
times used in place of potential energy. (See 
Energy, Potential?) 

Stress, Magnetic The force acting 

to produce a strain in the air-gap between 
two dissimilar magnet poles by the action of 
the lines of magnetic force, bridging such air 

gap. 

Striae, Electric Parallel streaked 

bands, consisting of alternate light and dark 
spaces, produced in tubes containing low 
vacua, by the passage of rapidly alternating 
currents through them. (See Tube, Strati- 
fication?) 

Strip, Safety A strip or bar used as 

a safety fuse. (See Fuse, Safety?) 

Stripping. — Dissolving the metal coating 
from a silver-plated or other metal-plated ar- 
ticle. 

The object of the "stripping " process is tore- 
cover silver from imperfectly plated ware, or 
from old ware which is to be replated. 

Stripping of silver is accomplished either in the 
cold or by aid of heat, by the use of the following 
solutions, viz.: 
Concentrated sulphuric acid, 

(Baume, 66 degrees). ioo parts. 

Concentrated nitric acid, 

(Baume, 40 degrees) 10 " 

The objects are suspended in this liquid, which, 
provided it be not diluted with water, possesses 
the property of dissolving the silver without 
touching the metal underneath. 



Baths.— (See Bath, Strip- 
(See Liquid, Strip- 



Strippin 

ping?) 

Stripping Liquid 

ping?) 

Stroke, Lightning — A disruptive 

discharge between two oppositely charged 
clouds, or between a cloud and the earth. 
(See Discharge, Disruptive?) 

Stroke, Lightning, Back or Return 

— An electric shock, caused by an induced 
charge, produced by the discharge of a light- 
ning flash. 

The shock is not caused by the lightning flash 
itself, but by a charge which is induced in neigh- 
boring conductors by the discharge. These in- 
duced effects are, in fact, effects of electro-dy- 
namic induction. (See Induction, Electro-Dy- 
namic?) A similar effect may be noticed by 
standing near the conductor of a powerful electric 
machine, when shocks are felt at every discharge. 

The effects of the return shock are sometimes 
quite severe. These effects are often experienced 
by sensitive people on the occurrence of a light- 
ning discharge at a considerable distance. 

In some instances the return stroke has been 
sufficiently intense to cause death. In general, 
however, the effects are much less severe than 
those of the direct lightning discharge. 

Struts for Telegraphic Poles.— Inclined 
wooden or iron poles, applied to telegraph 
poles in order to support the thrust or press- 
ure acting on them. (See Pole, Tele- 
graphic?) 

Sturgeon's or Barlow's Wheel. — A wheel 
capable of rotation on a horizontal axis, which, 
when placed between the poles of a magnet, 
rotates when a current is passed through it 
between the axis and the circumference. 

Sub-Aqueous Cable. — (See Cable, Sub- 
Aqueous?) 

Sub-Branch.— (See Branch, Sub.) 

Sub-Main.— (See Main, Sub?) 

Submarine Boat. — (See Boat, 
marine, Electric?) 

Submarine Cable. — (See Cable, 
marine?) 

Submarine Mine. — (See Mine, 
marine?) 



Sub- 



Sub- 



Sub- 



Sub. 



495 



[Sur. 



Submarine Telegraphy.— (See Teleg- 
raphy, Submarine) 

Substance, Ferro-Magnetic — A 

term proposed in place of paramagnetic, for 
substances that are magnetic after the man- 
ner of iron. (See Paramagnetic) 

Subterranean Mine. (See Mine, Sub- 
terranean) 

Subway, Electric An accessible 

underground way or passage provided for the 
reception of electric wires or cables. 

Underground electric conductors, like all elec- 
tric conductors, are liable to faults, crosses, etc. 
Unless they are readily accessible, very serious 
loss and damage may occur before the fault is 
located and corrected. 

Sulphating. — A name applied to one of the 
sources of loss in the operation of a storage 
battery, by means of the formation of a coating 
of inert sulphate of lead on the battery plates. 

The addition of a solution of sulphate of soda 
to the sulphuric acid liquid is claimed to have the 
effect of decreasing the extent of the sulphating. 

Summer Lightning. — (See Light?iing, 

Summer) 

Sun Spots. — (See Spots, Sim) 

Sunstroke, Electric, or Electric Prostra- 
tion or Insolation Physiological 

effects, similar to those produced by exposure 
to the sun, experienced by those exposed for 
a long while to the intense light and heat of 
the voltaic arc. 

Electric sunstroke is sometimes called electric 
insolation, or electric prostration. 

The effects of electric sunstroke were first 
noticed by Desprez in his classic experiments on 
the fusion or volatilization of carbon. 

On undue exposure to an intense electric ught 
the eyes are irritated and the skin burned as 
by the sun. In some cases it is claimed that the 
effects of sunstroke, or excessive production of 
heat, as in true insolation, are produced. In the 
applications of electricity to electric furnaces, 
these same effects have been noticed in an inten- 
sified degree. 

From some recent investigations it would ap- 
pear that these effects are to be ascribed to the 
light rather than to the heat. 



The symptoms are as follows: Pain in the 
throat, face and temples, followed by a coppery 
red color of the skin, irritation and watering of 
the eyes, when the symptoms disappear. The 
skin peels off in about five days. 

Superficial Eddy Currents. — (See Cur- 
rents, Eddy, Superficial) 

Super-Saturation of Solution. — (See 
Solution, Super-Saturation of) 

Supplement of Angle. — (See Angle, Sup- 
pleme?it of) 

Supply, Unit of, Electrical A unit, 

provisionally adopted in England by the 
Board of Trade, equal to 1,000 amperes flow- 
ing for one hour under an electromotive force 
of one volt. 

This would, of course, equal 1,000 watt-hours, 
and would be the same as ioo amperes flowing 
for ten hours under one volt. 

One unit of electrical supply is equal to 1.34 
actual horse-power expended for one hour, and 
will feed 13.4 Swan lamps of 21 candle-power for 
one hour. It is equal in illuminating power in 
Swan lamps to the light produced by 100 cubic 
feet of gas consumed in twenty 14-candle burners 
in one hour. 

The unit of electrical supply is called a "Board 
of Trade unit," a B. O. T. unit, or simply a bot. 
It is equal to one kilo-watt hour. 

Support, Tripod Roof A support 

for a housetop telegraphic line. 

The tripod roof support, as its name indicates, 
consists of a three-legged support for any suitable 
insulator. 

A common form is shown in Fig. 516. 

Support, Underground Cable A 

support provided for holding a cable where 
it passes around the side of a man-hole, un- 
derground conduit, or other similar location. 

Surface, Demarcation — The surface 

at which a demarcation current is generated. 

The surface which marks the point of in- 
jury in a muscle or nerve. 

Demarcation currents in electro- therapeutics, 
are currents produced in injured nerves or 
muscles. They are probably due to the chemical 
changes that take place between the injured and 
the uninjured tissues. The demarcation surface is 



Sur.] 



496 



[Sur. 



the surface separating parts in a normal condi- 
tion from those in an abnormal condition. 

An injury to a muscle or nerve causes or pro- 
duces at such surface a dying substance which is 




Fig. Si 6. Tripod Roof Support. 

negative to the uninjured, normal or positive sub- 
stance. Such a surface results in a demarcation 
current. 

Surface Density. — (See Density, Surface?) 

Surface, Equipotential, of a Conductor 
Through Which a Current is Flowing 1 

— A surface described within the mass of a 
conductor, conveying an electric current, at 
points perpendicular to the direction of the 
flow, all possessing the same potential. 

Surface, Equipotential, or Level Surface 
of Escaping Fluid A surface de- 
scribed within the mass of a fluid in motion 
at all places perpendicular to the stream lines 
passing such surface. 

Surface Integral of Magnetic Induction. 
— (See Induction, Magnetic, Surface-Inte- 
gral of) 

Surfaces, Equipotential, Electrostatic 

Surfaces, all the points of which are 

at the same electric potential. (See Poten- 
tial, Electric) 



Electric surfaces perpendicular to the lines 
of electric force over which a quantity of 
electricity, considered as being concentrated 
at a point, may be moved without doing 
work. (See Field, Electrostatic.) 

Equipotential surfaces correspond with a water 
level, over which a body may be moved horizon- 
tally without doing any work against the force of 
gravity. 

In the case of the charged insulated sphere, 
shown in Fig. 517, the equipotential surfaces, 
represented by the circles, are concentric. 




Fig. J 17. Equipotential Surfaces. 

Surfaces, Equipotential, Magnetic 

— Surfaces surrounding the poles of a mag- 
net, or system of magnets, where the mag- 
netic potential is the same. (See Potential, 
Magnetic) 

Magnetic equipotential surfaces extend in a 
direction perpendicular to the lines of magnetic 
force. (See Field, Magnetic.) 

No work is required in order to move a unit 
pole over equipotential magnetic surfaces, be- 
cause in so doing it cuts no lines of magnetic 
force. Work, however, is done when the motion 
is from one equal potential surface to another. 

Equipotential surfaces, whether electric or mag- 
netic, cannot intersect one another, since their 
potential is the same at all points. 

Surfaces, Isothermal Surfaces con- 
necting points in a body which have the same 
temperature, 

Surging Discharge. — (See Discharge, 
Surging.) 

Surgings, Electric Electric oscilla- 
tions set up in a charged conductor that is 
undergoing rapid discharge. 

. These surgings produce waves in the surround- 
ing ether that travel outwards with the velocity of 



Sus.] 



497 



[Sus. 



light. (See Electricity, Hertz's Theory of Elec- 
tro-Magnetic Radiations or Waves.) 

Susceptibility, Magnetic The ratio 

existing between the induced magnetization 
and the magnetic force producing such mag- 
netism, or the intensity of magnetism divided 
by the magnetic force. 

Susceptibility relates to the poles produced in a 
body by a magnetizing force, whereas permea- 
bility refers its power to conduct lines of force. 
When the inducing field has unit strength of 
magnetization, the magnetic susceptibility will 
measure directly the strength of the magnetiza- 
tion. 

When a bar of iron is placed in a magnetic 
field, it is threaded by the lines of magnetic force, 
and thus becomes magnetized by induction. This 
induction will necessarily depend both on the 
number of lines of force in the magnetizing field 
and on the magnetic permeability of the magnet- 
ized body ; or, in other words, the induction is 
equal to the product of the intensity of the mag- 
netizing field and the magnetic permeability of 
the body in which the induction occurs. 

The magnetic susceptibility is sometimes called 
the Co-efficient of Magnetization; calling K, the 
susceptibility, H, the magnetizing force, and I, the 
intensity of the resulting magnetization; then 

K=I. 
H 

The magnetic permeability is sometimes called 

the Co-efficient of Magnetic Induction, calling yw, 

the permeability, B, the magnetic induction and 

H, the magnetic force producing the induction ; 

then 

B 

Suspending Wire of Aerial Cable. — (See 
Wire, Snspendi7ig, of Aerial Cable) 

Suspension, Bifllar The suspen- 
sion of a needle by two c 
parallel wires or fibres, 
as distinguished from 
a suspension by a sin- 
gle wire or fibre. 

M 

A bifilar suspension is * ■ - - 

shown in Fig. 518. The 
two threads, a b and a' 
b', are connected to the Fig-S 1 
needle M X, so as to per- 
mit it to hang in a true horizontal position. Any 



2Li 



Bifilar Suspen- 
sion. 



twisting, around the imaginary axis c c', causes 
the lines of suspension, a b and a' b', to tend to 
cross one another and so shorten the axis c c' . 

Harris, who was the first to employ the bifilar 
suspension, showed that the reactive force im- 
parted to the suspension threads by turning the 
needle, was: 

(1.) Directly proportional to the distance be- 
tween the threads. 

(2.) Inversely as their lengths. 

(3.) Directly proportional to the weight of the 
suspended body. 

(4. ) Proportional to the angle of twist or torsion 
of the threads on each other. 

Any deflection of the needle shortens the verti- 
cal distance between the points of support and 
the needle, and so tends to lift the needle. The 
motions are therefore balanced against the force 
of gravity instead of against the torsion of the 
fibre. 

Suspension, Combined Fibre and Spring 

— The suspension of a needle by the 

combined use of a spiral spring and a single 
fibre. 

In this form of suspension the spring is intro- 
duced between the fibre and the needle. It is 
valuable for marine galvanometers and other ap- 
paratus exposed to tilting or rolling motions, be- 
cause it permits the instrument to be tilted 
through several degrees without causing any con- 
siderable variation in the deflections produced by 
the current or the charge. 

Suspension, Fibre Suspension of a 

needle by means of a fibre of unspun silk or 
other material. 

A fibre suspension generally means a single 
fibre or thread. It may, however, be applied to 
a bifilar suspension. (See Suspension, Bifilar. ,) 

A fibre suspension is to be preferred to a pivot 
suspension, since it eliminates all friction. It has, 
however, the disadvantage of necessitating level- 
ing screws. 

Suspension, Knife-Edge The sus- 
pension of a needle on knife edges that are 
supported on steel or agate planes. 

A suspension of this kind is used in the dip- 
ping needle, since it permits of freedom of mo- 
tion in a single vertical plane only. 

Suspension, Pivot Suspension of a 

needle by means of a jeweled cup and a me- 
tallic pivot. 



Swa.J 



498 



[Swi. 



The jeweled cup is placed above the centre of 
gravity of the needle, and is supported on a steel 
point. As a rule, compass needles have this 
variety of support. 

Swage. — A particular form of anvil on 
which highly heated metallic plates are shaped 
by hammering them into forms the same as 
that of the anvil on which they are placed. 

Swage. — To fashion heated metallic plates 
by hammering them into the form of an anvil 
on which they are supported. 

Swaging'. — Fashioning highly heated me- 
tallic plates into any desired form by ham- 
mering while on suitable dies. 

Swaging", Electric The forming or 

shaping of metallic plates by hammering 
them against suitable anvils or dies while 
softened by electrical heating. 

The electro-swaging apparatus consists of a 
welding transformer provided with a movable 
clamp. The pressure required for the swaging 
is attained by the use of steam admitted into a 
cylinder by a lever which operates a four-way 
valve. 

The rod, bar, or plate of metal to be shaped or 
swaged, is first heated by the passage of a pow- 
erful heating current, obtained preferably from a 
welding transformer, one of the clamps of which 
is movable. When the metal is suitably softened 
by the passage of the current, it is then subjected 
to swaging. 

Swelling" Current. — (See Currents, Swell- 
ing^ 

Swelling Faradic Current. — (See Cur- 
rents, Swelling Faradic?) 

Swinging Annunciator. — (See Annuncia- 
tor, Pendulum or Swinging?) 

Swinging Cross. — (See Cross, Swinging 
or Intermittent?) 

Switch, Automatic, for Incandescent 

Electric Lamps A device by which 

incandescent electric lamps can be lighted or 
extinguished at a distance by means of push 
buttons. 

The automatic switch for incandescent lamps 
corresponds in electric lighting to the automatic 
gaslighting device in systems of electric gaslight- 
ing. It consists essentially of two electro- 
magnets, one for turning the switch which lights 



the lamp by cutting them into the circuit of the 
lighting mains or conductors, and the other for 
extinguishing them, by cutting tnem out. These 
electro-magnets are operated by two push buttons, 
a black one to extinguish the lamp and a white 
button to light it. 

The details of the automatic switch are shown in 
Fig. 520. The mains M 1 andM 2 , are connected to 
one set of contacts, and the branches containing 




Fig. 519. Automatic Switch. 

the lamps to be lighted, to the contacts between 
them. The push buttons, P 1 and P 2 , are con- 
nected by their wires to the main M 1 and the 
branch B 1 . 

These buttons are made respectively positive 
and negative, and are marked -j- and — . The 
third wire of the push button is connected as 
shown to the lamp L, and the switch magnet, 
SM. 

When the contact is closed atP 1 , the arma- 
ture of S M, closes the contact through C. 
When the button is released, connection is estab- 




Fig. J 20. Automatic Switch.. 

lished between the magnet and the lamp L, in 
series. This is for the purpose of cutting down 
the circuit to the ^ of an ampere, and thus per- 
mitting a thin wire to serve between the button 
and the switch magnet. 

When the button, P 2 , is closed the lamps are 
turned out. 

Switch Board. — (See Board, Switch?) 

Switch Board, Multiple — (See 

Board, Multiple Switch?) 



Swi.] 



499 



[Swi. 



—(See 



—(See 



Switch Board, Telegraphic 

Board, Switch, Telegraphic?) 

Switch Board, Trunking - 

Board, Switch, Trunking.) 

Switch, Break-Down A special 

switch, employed in small three-wire systems, 
for connecting the positive and negative bus- 
wires in such a manner as to practically 
convert it into a two-wire system and permit 
the system to be supplied with current from 
a single dynamo. (See Wires, Bus.) 

Switch, Changing A switch de- 
signed to throw a circuit from one electric 
source to another. 

A changing switch, for example, is of use in 
disconnecting a circuit from one dynamo and 
connecting it to another; or, in other words, to 
suddenly transfer the load from one dynamo to 
another. 

Switch, Changing-Over — A term 

sometimes applied to a changing switch. 
(See Switch, Changing.) 

Switch, Distributing A multiple 

switch board. (See Board, Multiple Switch?) 

Switch, Distributing, for Electric 

Lights A switch employed in a 

system of arc lighting by series-distribu- 
tion, by means of which any particular 
dynamo-electric machine or a number of 




Fig. 5 ST. Double- Break Knife Switch. 

separate dynamo-electric machines can 
be connected with the same circuit without 
interfering with the lights. (See Board, Mul- 
tiple Switch?) 

Switch, Double-Break — A term 

sometimes used for double-pole switch. (See 
Switch, Double-Pole?) 



Switch, Double-Break Knife A 

knife switch provided with double-break con- 
tacts. 

A double-break knife switch is shown in Fig. 
521. 

Switch, Double-Pole — A switch 

that makes or breaks contact with both poles 
of the circuit in which it is placed. 

A switch consisting of a combination of 
two separate switches, one connected to the 
positive lead and the other to the negative 
lead. 

Double-pole switches are used in most systems 
of incandescent lighting in order to insure the 
thorough separation of the circuit from the main 
conductor or leads when cut out and to diminish 
the spark. 

Switch, Feeder The switch em- 
ployed for connecting or disconnecting each 
conductor of a feeder from the bus-bars in a 
central station. 

Switch, Four-Point A switch by 

which a circuit can be completed through 
four central points. 

Switch, Knife A switch which is 

opened or closed by the motion of a knife 




Fig. 522. Lamp- Socket Switch. 

contact which moves between parallel contact 
plates. 

A knife-edge switch. (See Switch, Knife- 
Edge.) 

Switch, Knife-Break — A knife 

switch. (See Switch, Knife.) 

Switch, Knife-Edge A term some- 
times used in place of knife switch. (See 
Switch, Knife?) 



Swi.] 



500 



[SwL 



Switch, Lamp-Socket — A switch 

placed in the socket of an incandescent lamp 
and provided for throwing the lamp in and 
out of the circuit. 

A form of lamp socket switch is shown in Fig. 
522. Its operation will be understood from an 
inspection of the drawing. 

Switch Pin.— (See Pin, Switch) 

Switch, Plug A switch in which a 

metal plug is withdrawn to throw into a cir- 
cuit a coil or other device, the ends of which 
are connected to metallic blocks that are suf- 
ficiently near together to be joined and short- 
circuited by the insertion of the plug. 

Switch, Pole-Changing —A switch 

employed for changing the direction of the 
current in any circuit. 

A form of pole-changing switch is shown in Fig. 
523- 




Fig. S 2 S- Pole-Changing Switch. 

If the two outer contacts are connected to the 
same pole as the source, as, for example, the 
positive, and the two intermediate contacts are 
connected to the other pole, or to the negative, 
then in the position shown in the cut, the current 
will flow through any receptive device connected 
with the switch, in one direction, but if the 
switch is moved to the left, it will flow in the op- 
posite direction. 

Switch, Removable Key A plug 

switch. (See Switch, Plug) 

Switch, Reversing A switch for 

reversing the direction of the battery current 
through a galvanometer. 

A simple reversing switch consists of four in- 
sulated brass segments mounted on a plate of 
ebonite and furnished with openings between 
them for plug connections. 

The battery terminals are connected to two di- 
agonally opposite segments, as B, and D, Fig. 
524, and the leading wires of the galvanometer, 



or other instrument, to the other segments, as C 
and A. If, now, the plugs are placed between B 
and C, and A and D, the battery current flows 
in one direction. If, however, the plugs are 




Fig. 524. Reversing Switch. 

placed between A and B, and C and D, the bat- 
tery current will flow in the opposite direction. 

The battery current is cut off if one plug is re- 
moved. In practice, however, it is preferable to 
remove both plugs, so as to avoid any current 
from want of sufficient insulation. 

Switch, Snap A switch in which 

the transfer of the contact points from one 
position to another is accomplished by means 
of a quick motion obtained by the operation 
of a spring. 

The object of the snap switch is to prevent the 
switch resting in any half way position, and thus 
preventing the establishing of an arc. 

Switch, Telephone, Automatic A 

device for automatically transferring the con- 
nection of the main line from the call bell to 
the telephone circuit. 

In most telephone circuits, as now arranged, 
the automatic switch, besides transferring the main 
line from the call bell to the telephone circuit, 




4a 

Fig. 523. Automatic Telephone Switch. 
closes the local battery circuit of the transmitter 
on the removal of the telephone from its support- 
ing hook. 



Swi.] 



501 



[Synn 



The means whereby this is accomplished are 
shown in Fig. 525. On the removal of the tele- 
phone from the hook L, the lever is pulled up- 
wards by the spring Z, thus closing the contacts I, 
2 and 3, by which the local battery S, is closed 
through the circuit of the transmitter, the tele- 
phone disconnected from the circuit of the call bell 
M, B, and connected with the circuit of the trans- 
mitter. On replacing the telephone on the hook 
L, its weight depresses the lever, breaking con- 
nection with 1, 2 and 3, and establishing connec- 
tion with the call circuit. 

Switch, Three-Point A switch by 

means of which a circuit can be completed 
through three different contact points. 

Switch, Time An automatic switch 

in which a predetermined time is required 
either to insert a resistance in or remove it 
from a circuit. 

Switch, Two-Point A switch by 



means of which a circuit can be completed 
through two different contact points, 

Switch, Two- Way A switch pro- 
vided with two contacts connected with two 
separate and distinct circuits. 

Switch, Yale-Lock, for Burglar Alarm 

(See Alarm, Yale-Lock Switch 

Burglar^) 

Switched-Iu. — Placed in a circuit by means 
of a switch. (See Closed-Circuited.) 

Switehed-Out. — Cut out of a circuit by 
means of a switch. (See Open-Circuited^) 

Symbols and Diagrams, Standard Elec- 
tric Standard symbols and diagrams 

used in electro-technics. 

The standard electric diagrams and symbols 
shown on pages 501, and 502, were arranged by 
Prof. F. B. Crocker, and are reproduced from 
the Electrical Engineer. 



SYMBOLS COMMONLY 
MECHANICAL. 



USED IN ELECTRICAL WORK. 

ELECTRICAL. 



Ju or 1. Length 
~3Lorm. Mass 
Tort. Time 
T. Velocity 
F orf. Force 
g. Acceleration 

due to gravity. 
Yforw. Work. 
P. Power. 
ft. lb. Footpound. 



D. Diameter 

r. Radius 

H.P. Horse power 

I.H.P. Indicated " 

B.H.P. Brake 

r.p.m. Revolutions 

per min. 
C.G.S. Centimetre 
gram vie second 
{System) 
JL.W.G. American 

Wire Gauge 
B.W .G. Birmingham 

Wire Gauge 



/-©•- 



E. orEJil.F. Electromotive 

force 
P.D. Potential difference 
C. Curre7it 
R. Resistance 
p. Specific resistance 
Q. Quatitity 

K. Electrostatic capacity. 
L. Inductance ( Coeffc. of) 
A.JI. Amperemeter. 
V.M. Voltmeter 
F.3I. Field Magnet 
-f- Positive pole or terminal 
— Negative " " 



v. Volt 

amp. Ampere 

w. Ohm 

£2. Megohm. 

B.A.U. Brit. Ass'n Unit 

Jllfd. Microfarad 

h. or hy. Henry 

z. Electrochemical 

equivalent 
J. Joule 
K.W. Kilowatt 
Complete period 
{Alt. cur-.) 
"Q. Dyna7iio 
Hill- Battery 

'Compound Wound Dynamo 

(BUB) 




MAGNETIC. 

North pole 

South pole 

Strength of pole 

Magnetizing for ce 
{C.G.S.) 

Magnetic induction 

{C.G.S. lines) 
Intensity of mag- 
neiization 

Magnetic per- 
meability 
Magnetic sus- 
ceptibility 

Horizontal 

intensity of Earth 's 

magnetism 



Siemens I .Armature 




Ammeter orXoUmcter 



£jb 



Telephone CiixttU 



Alternating Current 
Transformer Diagram 
| rnmary £ AZ f 
a Primary Current 
01 Secondary E M~F | 



incandescent LifftUituj . , , ■ ■-, , — _ 

<) § cj) §6 




Sym.] 



502 



[Sym. 



Mbr 


?e Telegraph System 


ij id 


,:i 






Fig. 32b. Crocker's Chart of Standard Electric Symbols and Diagrams. 



Sym.] 



503 



[Sys. 



Symmetrical Induction of Armature. — 

[See Induction, Symmetrical, of Arjnature.) 
Symmetrical Magnetic Field. — (See 
Field, Magnetic, Symmetrical?) 

Sympathetic Electrical Titrations. — - 
(See Vibrations, Sympathetic Electrical) 

Sympathetic Yibrations.— (See Vibra- 
tions, Sympathetic.) 

Synchronism. — The simultaneous occur- 
rence of any two events. 

V A rotating cylinder, or the movement of an 
index or trailing arm, is brought into synchronism 
with another rotating cylinder or another index 
or trailing arm, not only when the two are mov- 
ing with, exactly the same speed, but when in ad- 
dition they are simultaneously moving over simi- 
lar portions of their respective paths. 

In the Breguet Step-by-Step or Dial Telegraph 
(See Telegraphy, Step-by-Step), the movements of 
the needle on the indicator are synchronized with 
the movements of the needle on the manipulator. 
In systems oiFac- Simile Telegraphy the move- 
ments of the transmitting apparatus are syn- 
chronized with those of the receiving apparatus. 

In Delany's Synchronous Multiplex Telegraph 
System, the trailing arm that moves over a cir- 
cular table of contacts at the transmitting end, 
is accurately synchronized with a similar trailing 
arm moving over a similar table at the receiving 
end. 

Delany, who was the first to obtain rigorous 
synchronism at the two ends of a telegraphic 
line hundreds of miles in length, accomplishes 
this by the use of La Cour's phonic wheel, 
through the agency of correcting electric im- 
pulses, automatically sent in either direction over 
the main line, when one trailing arm gets a short 
distance in advance or back of the other. 

With alternating current dynamos, where one 
dynamo is feeding incandescent lamps connected 
to the leads in multiple, and it is desired to 
couple another alternating current dynamo in 
parallel with the first, it is necessary to obtain a 
complete synchronism of the two dynamos before 
coupling them, since otherwise the lamps will 
show variations in their light, and the machine 
may suffer. 

Synchronizable. — Capable of being syn- 
chronized. (See Synchronism.) 

Synchronize. — To cause to occur or act 
simultaneously. (See Synchronism.) 



Synchronized. — Caused to occur or act 
simultaneously. (See Synchronism.) 

Synchronizing- Dynamo-Electric Ma- 
chine. — (See Machine, Dynamo-Electric \ 
Synchronizing) 

Synchronous Multiplex Telegraphy. — 

(See Telegraphy, Synchronous Multiplex, 
Delany s System) 

System, Astatic An astatic com- 
bination of magnets. 

An astatic needle consists of an astatic system 
of two magnetic needles. The needles are 
rigidly fixed together with their opposite poles 
facing each other. The two needles form an as- 
tatic pair or couple. (See Needle, Astatic.) 

System, Block, for Railways (See 

Railroads, Block System for) 

System, Centimetre - Gramme - Second 

(See Units, Centimetre - Gramme - 

Second) 

System, Continuous Underground, of 

Motive Power for Electric Railroads 

— (See Railroads, Electric, Continuous Un- 
derground System of Motive Power for) 

System, Dependent, of Motive Power for 

Electric Railroads (See Railroads, 

Electric, Dependent System of Motive 
Power for) 

System, Independent, of Motive Power 
for Railroads (See Railroads, Elec- 
tric, Indepe7ident System of Motive Power 
for) 

System, Multiphase A term fre- 
quently applied to a system of rotating elec- 
tric currents. (See Current, Rotating) 

System of Distribution of Electricity by 
Commutating' Transformers. — (See Elec- 
tricity, Distribution of, by Commutating 
Transformers.) 

System of Distribution of Electricity by 
Condensers. — (See Electricity, Distribution 
of, by Alternating Currents by Means of 
Condensers. Electricity, Distribution of, by 
Continuous Current by Means of Condens- 
ers) 

System of Distribution of Electricity by 
Means of Alternating" Currents.— (See Elec- 



Sys.] 



504 



[Tai. 



tricity, Distribution of, by Alternating Cur- 
rents.) 

System of Distribution of Electricity toy 
Motor Generators. — (See Electricity, Dis- 
tribution of, by Motor Generators^) 

System, Three-Wire A system of 

electric distribution for lamps or other trans- 
lating devices connected in multiple, in which 
three wires are used instead of the two usually 
employed. 

In the three-wire system two dynamos are gen- 
erally employed, which are connected with one 
another in series. 

The three conductors are connected as shown 
in Fig. 527, the central conductor to the junction 
of the two dynamos and the two others to their 
free terminals, and the difference of potential be- 
tween the central and the two outer conductors 
is maintained the same. The lamps, or other 
electro-receptive devices, are placed in multiple- 
arc between either branch, and so distributed 
that the current in each branch is the same. 
When such balance is established no current 
flows through the central or neutral conductor. 
But when that balance is disturbed, the surplus 
current in one branch is taken up by the central 
conductor. 

The three-wire system effects considerable 



economy in the weight of wire required . Since in 
the multiple-series-connection of electro-receptive 
devices whatever difference of potential is im- 
pressed on the mains is fed to each device, no 
higher difference of potential can be employed on 
the mains than that which the devices are capa- 
ble of taking. In the case of an incandescent 
lamp, if such difference be exceeded, too strong 
a current is passed through the lamps with a 
consequent decrease in their life, 

In the three-wire system of distribution a higher 
difference of potential can be maintained on the 
mains than is required for any lamp placed in 

e 





Fig. J 27. Three-Wire System. 

connection therewith, and in this manner a con- 
siderable saving is effected in the cot of the leads. 



T. — A symbol used for time. 

T-shaped Spark. — (See Spark, T-Shaped.) 

Table, Quadruplex, A-Side of — 

That side of a quadruplex system which is 
worked by means of reverse currents. (See 
Telegraphy, Quadruplex}) 

Table, Quadruplex, B-Side of 

That side of a quadruplex system which is 
worked by means of strengthened currents. 
(See Telegraphy, Quadruplex?) 

Tables of Conducting Powers. — (See 
Powers, Conducting, for Electricity. Re- 
sistance, Electric.) 

Tachograph. — An apparatus for recording 
the number of revolutions per minute of a 
shaft or machine. 



Tachometer. — An apparatus for indicating 
at any moment on a revolving dial the exact 
number of revolutions per minute of a shaft 
or machine. 

A tachometer is sometimes called a speed in- 
dicator. 

Tachyphore. — A term proposed by Wurtz 
for a system of electric transportation, in 
which a carriage, formed of magnetic ma- 
terial, is propelled by the sucking action of 
solenoids placed along the track and ener- 
gized in succession during the passage of the 
car. 

This is generally called the portelectric sys- 
tem. (See Tort 'electric.) 

Tail Light— (See Light, Tail.) 



Tai. 



505 



[Tas, 



Tailing's. — False markings received in sys- 
tems of automatic telegraphy, due to retard- 
ation. (See Retardation) 

Tailings. — A term applied to the current 
that runs out of a line at the receiving end. 

The current that continues to run out at 
the receiving end of the circuit after the send- 
ing current is broken. 

The tailings in a telegraphic line are due to the 
effects of self-induction and static capacity follow- 
ing the breaking of the circuit which produce a 
current in the same direction as that sent into the 
line. Consequently, on the breaking of the cir- 
cuit, the current continues to flow out of the line at 
the distant or receiving end. This prolongation 
of the original current is known technically as 
the tailing or the tailing current. 

Talk, Cross In telephony an indis- 
tinctness in the speech transmitted over any 
circuit, due to this circuit receiving, either by 
accidental contacts or by induction, the speech 
transmitted over neighboring circuits. 

Tangent. — One of the trigonometrical 
functions. (See Function, Trigonometrical) 

Tangent and Sine Galvanometer, Com- 
bined (See Galvanometer, Combined 

Tangent and Sine) 

Tangent Galvanometer.— (See Galva- 
noineter, Tangent) 

Tangent Scale.— (See Scale, Tangent) 

Tangentially Laminated Armature Core. 

— (See Core, Armature, Tangentially Lam- 
inated) 

Tank, Cable A water-tight tank in 

which a section of a cable is placed for pur- 
poses of testing. 

The cable is tested either when merely covered 
by water, or when subjected to a pressure ap- 
proximately equal to or in excess of that to which 
it will be subjected when laid in the water. 

Reid has constructed cable tanks for testing 
under pressures as great as 4,500 pounds per 
square inch. The pressure is obtained by means 
of force pumps. 

When a cable section is subjected to these 
pressures any flaws or defects would be at once 
detected by the entrance of the water. 



Tanning, Electric An application 

of electric currents to tanning leather. 

The dressed hides are steeped in a solution of 
tannin through which an electric current is 
passed. 

It is claimed, that by this process, the hides 
are thoroughly tanned in from one to four days, 
in place of from four to twelve months, as re- 
quired by the. ordinary process. 

The tanning solution is placed in a vat fur- 
nished with suitable electrodes and filled with the 
tanning liquid, and the articles to be tanned are 
placed between the electrodes and a motion of 
revolution given to the vat. By these means 
the time required for the completion of the pro- 
cess is considerably shorter than that required by 
the ordinary process. 

Tap. — A conductor attached to a larger 
conductor in a shunted circuit. 

Tap, Ampere A tap provided for 

carrying off a current of one ampere. 

Tap Wires. — (See Wires, Tap) 

Tape, Insulating — A ribbon of 

flexible material impregnated with kerite, 
okonite, rubber or other suitable insulating 
material, employed for insulating wires or 
electric conductors at joints, or other exposed 
places. 

Sometimes the tape is formed entirely of some 
or another the above named insulating materials. 

Taped Wire.— (See Wire, Taped) 

Tapper, Double-Key (See Key, 

Double Tapper) 

Target, Electric A target in which 

the point struck by the ball is automatically 
registered by means of electric devices. 

A variety of targets have been devised. Gen- 
erally, however, the target is divided into a num- 
ber of separate sections provided with circuits of 
wires, on the making or breaking of any of which, 
by the impact of the ball, the section struck is au- 
tomatically indicated on an electric annunciator. 
(See Annunciator, Electro-Magnetic.) 

Taste, Galvanic A sensation of taste 

produced when a voltaic current is passed 
through the tongue or in the neighborhood of 
the gustatory nerves, or nerves of taste. 



Tea.] 



506 



[Tel, 



Teaser. — An electric current teaser. (See 
Teaser, Electric Current) 

Teaser, Electric Current A coil 

of fine wire placed on the field magnets of a 
dynamo-electric machine, underneath the se- 
ries coil wound thereon, and connected as a 
shunt across the main circuit. 

The name teaser was applied by Brush to the 
coil of fine wire used as above described to main- 
tain constant electromotive force under variations 
of load. 

Technics, Electro The science 

which treats of the physical applications of 
electricity and the general principles applying 
thereto. 

Tee, Lead A tee-shaped lead tube 

provided for the purpose of taking a branch 
joint from a main cable to a service line. 

Tee, Split-Lead A tee-shaped lead 

tube that is split for readily covering a joint 
at a loop in a cable. 

Tel-Autogram. — The recorded message 
obtained by means of a tel-autograph. (See 
Tel- A utograph ) 

Tel- Autograph. — A telegraphic system for 
the fac-simile reproduction of handwriting. 

Teleautograph. — An orthography some- 
times employed for tel-autograph. (See Tel- 
Autograph) 

Tele-Barometer, Electric An elec- 
tric recording barometer for indicating and 
recording barometric or other pressures at a 
distance. 

Telegrapher's Cramp. — (See Cramp, 
Telegrapher's) 

Telegraphic. — Pertaining to telegraphy. 

Telegraphic Alarm. — (See Alarm, Tele- 
graphic) 

Telegraphic Alphabet. — (See Alphabet, 
Telegraphic) 

Telegraphic Alphabet, Continental Code 
(See Alphabet, Telegraphic : Inter- 
national Code) 

Telegraphic Alphabet, Morse's 

(See Alphabet, Telegraphic : Morse's) 



Telegraphic Arm. — (See Arm, Tele- 
graphic) 

Telegraphic Bracket. — (See Bracket, 
Telegraph ic) 

Telegraphic Cable.— (See Cable, Tele- 
graphic) 

Telegraphic Code. — (See Code, Tele- 
graphic) 

Telegraphic Earth-Circuit. — (See Cir- 
cuit, Earth, Telegraphic) 

Telegraphic Embosser. — (See Embosser, 
Telegraphic) 

Telegraphic Fixtures. — (See Fixtures, 
Telegraphic) 

Telegraphic Fixtures, House-Top 

(See Fixtures, Telegraphic House-Top) 

Telegraphic Ground Circuit. — (See Cir- 
cuit, Ground, Telegraphic) 

Telegraphic Joints.— (See Joint, Tele- 
graphic or TelephoJiic) 

Telegraphic Key. — (See Key, Telegraph- 
ic) 

Telegraphic Line Circuit. — (See Circuit, 
Line, Telegraphic) 

Telegraphic Needle. — (See Needle, Tele- 
graphic) 

Telegraphic Paper Winder. — (See Wind- 
ers, Telegraphic Paper) 

Telegraphic Pocket Relay. — (See Relay, 
Pocket Telegraphic) 

Telegraphic Register. — (See Register, 
Telegraphic^) 

Telegraphic Switch Board. — (See Board, 
Switch, Telegraphic) 

Telegraphic Translates — (See Trans- 
later, Telegraphic) 

Telegraphically. — In a telegraphic 
manner. 

Telegraphing. — Sending a communication 
by means of telegraphy. 

Telegraphy, Acoustic A non-re- 
cording system of telegraphic communica- 
tion, in which the dots and dashes of the 
Morse system, or the deflections of the needle 
in the needle system, are replaced by sounds 



Tel. 



507 



[Tel. 



that follow one another at intervals, that 
represent the dots and dashes, or the de- 
flections of the needle, and thereby the letters 
of the alphabet. 

Morse invented a sounder, for this purpose, 
which is used very generally. (See Sounder, 
Morse Telegraphic. ) 

Steinheil and Bright each invented acoustic 
systems of telegraphy in which electro-magnetic 
bells are used. 

For details of the apparatus and system see 
Telegraphy, Morse System of. 

Telegraphy, American System of 

A term sometimes applied to the Morse sys- 
tem of telegraphy. (See Telegraphy, Morse 
System of.) 

Telegraphy and Telephony, Simultane- 
ous, Over a Single Wire Any system 

for simultaneous transmission of telegraphic 
and telephonic messages over a single wire. 

These systems are based, in general, on the 
fact that a gradual make-and-break in a tele- 
phone circuit fails to appreciably affect a tele- 
phone diaphragm. By the use of graduators the 
makes and breaks required for the transmission 
of the telegraphic dispatch are effected so grad- 
ually that they fail to appreciably influence the 
telephone diaphragm, and thus permit simultane- 
ous telegraphic and telephonic transmission over 
a single wire. (See Graduators.) 

Telegraphy, Autographic A name 

sometimes applied to fac-simile telegraphy. 
(See Telegraphy, Fac-Sz'mile.) 

Telegraphy, Automatic A system 

by means of which a telegraphic message is 
automatically transmitted by the motion of a 
previously perforated fillet of paper contain- 
ing perforations of the shape and order re- 
quired to form the message to be transmitted. 

The paper passes between two terminals of the 
main line, the circuit of which is completed when 
the terminals come into contact at the perforated 
parts, and is broken when separated by the 
un perforated parts of the paper. 

In the automatic telegraph some form of regis- 
tering apparatus is employed. 

In the Wheatstone system, the perforations 
me hanically control the movements of the levers 
which make contacts between the line and the 
battery. 



The advantage of automatic telegraphy arises 
from the fact that the rate of transmission or re- 
ception of signals does not depend on the expert- 
ness of the operators, and the messages may be- 
perforated on the slips preparatory to transmis- 
sion. 

Type- printing telegraphs are often used for 
registering apparatus, in which case the im- 
pulses required for the transmission of the dif- 
ferent letters are automatically sent into the line 
by the depression of corresponding keys on a. 
suitably arranged key -board. 

Telegraphy, Chemical A system 

by means of which the closings of the main- 
line-circuit, corresponding to the dots and 
dashes of the Morse alphabet, are recorded 
on a fillet of paper by the electrolytic action 
of the current on a chemical substance with 
which the paper fillet is impregnated. (See 
Recorder, Chemical, Bain's^) 

Telegraphy, Contraplex Duplex 

telegraphy in which transmissions are simul- 
taneously made from opposite ends of the 
line. 

When the transmissions are simultaneously 
made from the same end of the line, the system is & 
called diplex telegraphy. (See Telegraphy , Di- ! ~ 
plex. ) 

Telegraphy, Dial A system of 

telegraphy in which the messages are received 
by the motions of a needle over a dial plate.. 
(See Telegraphy, Step-by- St 'ep.) 

Telegraphy, Diplex A method of 

simultaneously sending two messages in the 
same direction over a single wire. 

Diplex telegraphy is to be distinguished from 
duplex telegraphy, where two messages are simul- 
taneously transmitted over a single wire in oppo- 
site directions. 

Telegraphy, Double-Needle — 



— A sys- 
tem of needle telegraphy in which two sepa- 
rate and independently operated needles are: 
employed. 

This system differs from the single-needle sys- 
tem only in the fact that two needles, entirely in- 
dependent of each other, are mounted side by side, 
on the same dial, so as to permit their simultane- 
ous operation by the right and left hand of the 



Tel.] 



508 



[Tel. 



operator. Each needle has therefore a separate 
wire. 

The increase in speed of signaling thus obtained 
is not, however, sufficiently great to balance the 
increased expense of construction. Single-needle 
instruments, therefore, are preferred to those 
with two needles. 

Telegraphy, Duplex, Bridge Method of 

■ — A system whereby two telegraphic 

messages can be simultaneously transmitted 
over a single wire in opposite directions. 

Various duplex telegraphs have been devised. 

The Bridge Duplex is shown in Fig. 528. The 
receiving relay is placed in the cross wire of a 
Wheat stone bridge. (See Bridge, Electric.) 




(US 0B [fj 

Fig. 528. Duplex Telegraphy, Bridge, Method. 

When the ends of this cross wire are at the 
same potential, whicn will occur when the resist- 
ances in the four arms are proportionately equal, 
no current passes. 

The battery is connected through the trans- 
mitter K, which is arranged so that the battery 
contact is made before the connection of the line 
to earth is broken, to H, where the circuits 
branch to form the arms of the bridge. Adjust- 
able resistances A, B, are placed in the two arms 
of the bridge. 

The line wire L, connected as shown, forms 
the third arm, and a rheostat or other adjustable 
resistance R, connected to a condenser C, as 
shown, forms the fourth arm. (See Rheostat.) 
The relay M, is placed in the cross wire of the 
bridge thus formed. Small resistances V, and 
W, are placed in the circuit of the battery to pre- 
vent injurious short circuiting. 

A similar disposition of apparatus is provided 
at the other end of the line. If, now, the four re- 
sistances at one end are suitably adjusted, the 
relay will not respond to the outgoing current ; 
but, since an earth circuit is employed, it will 



respond to the incoming current. The relay at 
either end, therefore, will only respond to signals 
from the other end. The operator may thus 
signal the distant station while, at the same time, 
his relay, not being affected by his sending, is in 
readiness to receive signals from the other end. 

Telegraphy, Duplex, Differential Method 

of A system of duplex telegraphy in 

which the coils of the receiving and transmit- 
ting instruments are differentially wound. 

A differential system of duplex telegraphy is 
shown in Fig. 529. The coils of the receiving 
and transmitting galvanometers at A and B, are 
differentially wound. One of the coils of A, is 
connected to that of B, through the line, as 
shown; and the other, in each to the rheostats 
at R, and R'. As these coils are differentially 
wound, when equal currents flow in opposite 
directions through either of the instruments at A 
B, no deflection of the galvanometer occurs. 

The battery at A, has its copper terminal, and 
that at B, its zinc terminal, connected to earth. 
When the keys at A and B, are depressed simul- 
taneously, the currents sent into the line flow in 
the same direction and strengthen each other. 

Suppose now that only the key at A, be de- 
pressed. The current divides equally between 
rheostat and line, the resistance eabb' a' e', r', 
being made equal to the resistance e c d R. 

This current passes through both coils of the 
instrument at A, and produces no deflection of 
the needle; but since it only passes through one 
coil at B, it deflects the galvanometer needle, and 
produces a signal. 




Fig.j2Q. Duplex Telegraphy, Differential Method. 

If the keys at A, and B, are simultaneously 
closed, the effect on the line is to add the current 
of the two batteries, but each rheostat circuit is 
traversed by its own battery current only. 

The line-connected coils of the galvanometer 
have, therefore, the stronger currents flowing 
through them, and the needles of both are moved, 
just as if, with a single battery discharging into 
the line, its resistance had been decreased. Each 



Tel J 



509 



[Tel. 



•sender's instrument is unaffected by the currents 
he sends into the line, and is, therefore, ready to 
be operated by the currents sent into the line by 
the sender at the other end of the line. 

The two currents in duplex telegraphy, there- 
fore, do not pass each other on the line; on the 
contrary, they are sent into the line in the same 
direction. 

Since, when either key is moving there is a 
small interval of time when the circuit is broken 
.for incoming currents, the keys are generally 
made so as to close the second contact before 
breaking the first. 

In order to avoid disturbing the balance on the 
introduction of the resistance of the batteries at A 
or B, on closing the circuits, an equal resistance 
is added at r and r', between the back stop and 
the earth. 

Since the proper operation of duplex telegraphy 
requires a balance in the resistance of the circuits 
of the differentially wound coils, a rheostat at R, 
and R', is necessary. 

Besides balancing the line for resistance, it is 
necessary to balance it for capacity. A condenser 
is, therefore, necessary when the circuit exceeds 
in length about ioo miles, or has much cable or 
underground wire. 

Telegraphy, Fac-Simile A system 

whereby a fac-simile or copy of a chart, 
diagram, picture or signature is telegraphically 
transmitted from one station to another. 

Fac-simile telegraphy is sometimes called auto- 
graphic telegraphy, or pantelegraphy. 

Bakewell's fac-simile telegraph, which was one 
of the first devised, consists of two similar metal 
cylinders c, c', arranged at the two ends of a 
telegraph line L, at M and M', as shown in Fig. 
530. These cylinders are synchronously rotated 







"R.-'.i."""'''' 



Fig. 530. Bakewell's Fac-Sz'mile Telegraphy. 

and provided with metallic arms or tracers r, r', 
placed on a horizontal screw in the line circuit 
and moved laterally over the surface of the 
cylinder on its rotation. 

At the transmitting station the chart, writing, 



or other design is traced with varnish, or other 
non-conducting liquid, on the surface of the 
metallic cylinder, as at M, and a sheet of chemi- 
cally prepared paper, similar to that employed in 
the Bain chemical system is placed on the surface 
of the receiving cylinder at M'. (See Recorder, 
Chemical, Bain s. ) 

The two cylinders being synchronously rotated, 
the metallic tracer breaks the circuit in which it 
is placed when it moves over the non-conducting 
lines on the cylinder, and thus causes correspond- 
ing breaks in the otherwise continuous blue spiral 
line traced on the paper-covered surface of M'. 

The telegraph keys at R, R', are used for the 
purposes of ordinary telegraphic communication 
before or after the record is transmitted. 

Caselli's Pan-Telegraph is an improvement on 
Bakewell's Copying Telegraph. Better methods 
are employed for maintaining the synchronism 
between the transmitting and receiving instru- 
ments, for which purpose a pendulum, vibrating 
between two electro-magnets, is employed. 

Telegraphy, Fire Alarm A system 

of telegraphy by means of which alarms can 
be sent to a central station, or to the fire 
engine houses in the district, from call boxes 
placed on the line. 

The alarms are generally sounded by an ap- 
paratus similar to a district call, so that the pull- 
ing back of a lever rotates a wheel, by means ot 
which successive makes and breaks are produced, 
the number and sequence of which enable the 
receiving stations to locate the particular box 
from which the signal is sent. 

In the case of some buildings, the alarms are 
automatic, and either call for help from the 
central office, or for the watchman in the build- 
ing, or else turn on a series of water faucets or 
jets, in order to extinguish the fire. In these 
cases thermostats are used. (See Thermostat. ) 

Telegraphy, Gray's Harmonic Multiple 

A system for the simultaneous trans- 



mission of a number of separate and distinct 
musical notes over a single wire, which 
separate tones are utilized for the simultane- 
ous transmission of an equal number of tele- 
graphic messages. 

The separate tones are thrown into the lines 
by means of tuning forks automatically vibrated 
by electro-magnets. These forks inierrupt the 



Tel.] 



510 



[TeL 



circuit of batteries connected with the main line 
at the sending end of the line. 

The composite tone thus formed, is separated 
into its component tones by receiving electro- 
magnets called harmonic receivers, the armature 
of each of which consists of a steel ribbon or 
plate tuned to one of the separate notes sent into 
the line. As the complex or undulatory current 
passes through the coils of each harmonic re- 
ceiver, that note only affects the particular arma- 
ture that vibrates in unison with its ribbon or 
reed. The operator, therefore, at this receiver 
is in communication only with the operator at 
the key of the circuit that is sending this par- 
ticular note into the line. The same is true of the 
other receivers. 

The Morse alphabet is used in this system, the 
dots and dashes being received as musical tones. 
In practice it was found that there was no diffi- 
culty in each operator recognizing the particular 
sound of his own instrument in receiving, although 
many instruments were in the same room. 

By a subsequent invention the signals received 
are converted into the regular Morse characters 
by means of an ingenious device. 

Telegraphy, Induction A system 

for telegraphing by induction between moving 
trains and fixed stations on a railroad, by 
means of impulses transmitted by induction 
between the car and a wire parallel with the 
track. 

Two systems of inductive telegraphy are in 
actual use, viz., 

(i.) The Static Induction system of W. W. 
Smith and Edison, and 

(2. ) The Current or Dynamic Induction system 
of Willoughby Smith and Lucius J. Phelps. 

In the System of Static Induction, one of the 
condensing surfaces which receives or produces 
the charge, consists of a wire placed on the road 
so as to come as near the top of the cars of the 
moving train as possible. The other condensing 
surface is composed of the metal roofs of the mov- 
ing cars. 

Each condensing surface is connected to suit- 
able instruments and batteries, and to the earth ; 
the line wire at the fixed station being connected 
to earth through a ground plate, and the metal 
roof of the cars to earth through the wheels and 
track. 

Under these circumstances variations in the 
charge of either of the condensing surfaces pro- 



duce inductive impulses that are received by the 
other surface as telegraphic signals. 

The Morse alphabet is employed, but in place 
of the ordinary receiver or sounder, a telephone 
is used. 

In the System of Current Induction, the line 
wire is placed near the track, so as to be parallel 
with a coil of insulated wire placed on the side of 
the car, and which receives the inductive impulses. 
The coil of wire on the train is connected with 
instruments and batteries, and forms a metallic 
circuit. The line wire is also connected with 
suitable batteries and receiving and transmitting 
instruments. 

An induction coil is generally employed, since 
the greater and more rapidly varying difference 
of potential of its secondary wire renders it better 
suited for producing effects of induction. A. tele- 
phone is employed as a receiver, as in the system 
of static induction. The metallic car roof and 
the lower truss rods have been successfully used as 
the secondary conductor of the induction coil. 

The automatic make-and-break used for operat- 
ing the induction ceil, causes the Morse characters 
employed in this system to be received in the 
receiving telephone as shrill buzzing sounds. 

The receiving telephones used on the trains 
have a resistance of about 1,000 ohms. 

Telegraphy, Induction, Current System 

of A system of induction telegraphy 

depending on current induction between a 
fixed circuit along the road, and a parallel 
circuit on the moving train. 

The circuit on the train generally consists of a 
coil of wire. (See Telegraphy, Induction.) 

Telegraphy, Induction, Dynamic System 

of A term sometimes used in place of 

a system of telegraphic current induction. 
(See Telegraphy, Induction.) 

Telegraphy, Induction, Static System of 

A system of inductive telegraphy de- 
pending on the static induction between the 
sending and receiving instrument. 

A fixed wire placed along the road so as to come 
near another wire or metallic surface on the mov- 
ing train, imparts to the latter a static charge, 
which is utilized for the transmission of dispatches. 
The metal roof of the car is generally used for the 
condensing surface receiving the charge. (See 
Telegraphy, Induction.) 



Tel.] 



511 



[Tel. 



Telegraphy, Machine A term some- 
times applied instead of automatic telegraphy. 
(See Telegraphy, Automatic?) 

A system of telegraphy is properly called ma- 
chine telegraphy when both the transmission and 
the receiving of the telegraphic messages are ac- 
complished by machine, instead of by the hand, as 
usual. 

Telegraphy, Morse System of A 

system of telegraphy in which makes and 
breaks occurring at intervals corresponding 
to the dots and dashes of the Morse alphabet 
are received by an electro-magnetic sounder 
or receiver. 

A metallic lever A, Fig. 531, is supported on a 
pivot at G, between two set screws D, D, so as to 
have a slight movement in a vertical plane. This 
motion is limited in one direction by a stop at C, 
called the anvil or front contact, and in the other 
direction by a set screw F, which constitutes its 
back stop. 

The front stop C, is provided with a platinum 
contact or stud, which may be brought into 
contact with, or separated from, a similar stud 
placed directly opposite it. These contacts are 
connected to the ends of the circuit so that on 




Fig. S3 1 - Telegraphic Key. 

the movements of the key, by the hand of the 
operator placed on the insulated head B, the line 
is closed and broken in accordance with the dots 
and dashes of the Morse alphabet. A spring, the 
pressure of which is regulated by the screw F', is 
provided for the upward movement of the key. 
A switch H, is provided for closing the line when 
the key is not in use. 

The system generally used in the United States 
is known as the ' ' Closed-Circuit System, ' ' the bat- 
tery being connected to line whether the line is in 
u^e or not. This battery is generally placed at 
both ends of the line. 

In Europe, the " Open-Circuit System " is gen- 



erally used. Alternating currents and polarized 
relays are employed. One pole is connected to 
the line at the front of the key, and the other 
pole to the back of the key. When the line is 
not in use, it is connected to earth at both ends 
by switches conveniently placed for the operators. 
With this system, intermediate stations must each 
have a main battery, while in the closed-circuit 
system, the terminal batteries answer for all inter- 
mediate offices, which in some cases amount to as 
many as fifty. 

In the Morse system, each station is provided 
with a key, relay, sounder or register, and local 
battery. The closed-circuit, connecting one 
station with another, being broken by the open- 
ing of the switch H, or the working of the key, 
so as to open and close its contacts, the armature 
of the relay opens or closes the circuit of the 
local battery and operates the sounder or register- 
ing apparatus connected therewith. (See Sounder, 
Morse Telegraphic. Apparatus, Registering, 
Telegraphic. ) 

Telegraphy, Multiplex A system 

of telegraphy for the simultaneous transmis- 
sion of more than four separate messages 
over a single wire. (See Telegraphy, Syn- 
chronous-Multiplex, Delany's System.) 

Telegraphy, Needle System of A 

system of telegraphy in which signals are 
transmitted by means of the movements of 
needles under the influence of the electric 
current. (See Telegraphy, Single-Needle) 

Telegraphy, Phonoplex A system 

of telegraphic transmission in which pulsatory 
currents, superposed on the ordinary Morse 
currents, actuate a modified telephonic re- 
ceiver, and thus permit the simultaneous 
transmission of several separate messages 
over a single wire without interference. 

Telegraphy, Printing A system of 

telegraphy in which the messages received 
are printed on a paper fillet. 

In Callahan's Printing Telegraph, two type 
wheels are employed, one of which carries letter 
type and the other numerals on its circumference. 
These printing wheels are placed alongside of 
each other, as shown in Fig. 532, but on separ- 
ate and independent axes. 

The type wheels are moved by a step -by -step 
device. The impulses necessary to bring the 



Tel.] 



512 



[Tel.. 



desired letters in position for printing are auto- 
matically sent by a circuit maker and breaker. 
These impulses are sent into the line by the de- 
pression of keys on a suitably arranged key- 
board. 

When the proper letter or v.v?z.era\ is reached 
at the receiving end, the printing wheel is 
stopped, and a paper fillet is pressed against its 
surface. The printing wheel is kept covered 
with ink by means of an inked roller. 

The transmitting instrument is similar in its 
operation to the Breguet manipulator. Separate 
transmitters are used for each of the wires. (See 
Telegraphy, Step -by - Step . ) 




Fig. S3 2. Callahan's Printing Telegraph. 



A system 



Telegraphy, Quadruplex — 

for the simultaneous transmission of four mes- 
sages over a single wire, two in one direction 
and the remaining two in the opposite direc- 
tion. 

Quadruplex telegraphy consists in fact of du- 
plex telegraphy duplexed. 

There are various systems of quadruplex teleg- 
raphy. The most important are the bridge 
method and the differential method. (See Teleg- 
raphy, Quadruplex, Bridge Method of. Telegra- 
phy, Quadruplex, Differential Method of.) 

Telegraphy, Quadruplex, Bridge Method 

of A system of quadruplex telegraphy 

by means of a double bridge duplex system. 
(See Telegraphy, Quadruplex?) 

In the bridge method of quadruplex telegraphy, 
as in the differential method, changes in the polar- 
ity and strength of the current are utilized to 
establish a double duplex system of transmission. 
Fig. 533 from Prescott's "Electricity and Electric 
Telegraphy, "from which the following description 



is taken, shows tit- method first employed by the 
Western Union Telegraph Company in 1874. 

A double current transmitter, or pole changer, 
is shown at T', with its operating key K' and 
local battery e'. This instrument interchanges 
the poles of the main battery E', wnen K, is de- 
pressed, and thus reverses the polarity of current 
on the line. 

The increment transmitter T 2 , is connected to 
the battery wire 12 of T', in such a way that 
when K', is depressed, the main battery E', is- 
placed in series with battery E, of say twice the 
strength of E', thus permitting a current of three- 
fold the original strength to be sent into the line. 



\cw root 




Fig. S3 J- Quadruplex Telegraphy, Bridge Method. 

Two receiving instruments R' and R 2 , ate 
placed at the distant end of the line. R', is a 
polarized relay whose armature is deflected in 
one direction by positive currents, and in the 
opposite direction by negative currents, independ- 
ently of their strength. That is to say, R', re- 
sponds to changes in the direction of the currents 
that pass through its coils, but not to changes in 
their strength. (See Relay, Polarized.) 

Relay R 2 , is non-polarized and the movements 
of its soft iron armature depend on a change in 
the strength of the current only. That is to say, 
R a , responds to changes in the strength of the 
current passing through its coils, but not to 
changes in their direction. 

These two relays R and R 2 , are placed in the 
bridge wire of a Wheatstone bridge. The entire 
apparatus of transmitting keys and relays is 
duplicated at each end of the line. Under these 
conditions, signals transmitted from either end of 
the line affect the instruments at the other end of 
the line, but not their own instruments, in the 
same manner as in the case of the bridge du- 
plex. (See Telegraphy, Duplex, Bridge Method 
of) 

Telegraphy, Quadruplex, Differential 



Tel.] 



513 



[Tel, 



-A system of quadruplex 



Method of — 

telegraphy by means of a double differential 
duplex system. 

Quadruplex telegraphy depends for its opera- 
tion on the use of two differentially wound relays 
at each station. One of these relays A, as shown 
in Fig. 534, which shows the general arrangement 
of the system, gives signals on a change in the 
direction of the current, but none on a change in 
the current strength. The other B, gives signals 
on changes in current strength, but none on 
changes in direction. They are, therefore, in- 
dependent of each other, and operate sounders 
that are under the independent control of two 
distinct receiving operators. 

A table, divided into four sections, is provided 
with places for two sending and two receiving 
clerks. The name " A side " is given to the side 
worked by the reversed currents, and the "B 
side" to that worked by the strengthened cur- 
rents. 



DUPLEX RHEOSTAT 

ifUifU 

r] 1 > EARTH 




i CORRECTING 
V RE^AY 



HE.V.ERSING KE 

/ E 

BATTERY 1. BATTERY 2, 

Fig. S3 4- Quadruplex Telegraphy, Differential Method. 

Referring to Fig. 534 the reversing key on the 
"A side " is merely indicated so as to avoid con- 
fusion by too great detail ; as is also the case with 
the increment key or the strengthening key atB. 
From the connections it will be seen that when 
the increment key is at rest, the reversing key 
sends currents from battery I. When the incre- 
ment key is depressed, the reversing key is shifted 
from battery I, and connected by its copper con- 
nection C, with the battery 2, of double the 
strength of I. Since, however, I, is thus connect- 
ed in series with C, the current strength is in- 
creased threefold. 

From the reversing key the current passes 
to the junction of the two coils with which the 
relay B, is differentially wound. It divides here 
between these coils, which are connected to simi- 



lar coils on relay A, as shown. The current 
from one coil on A, is sent to line, while that from 
the other coil goes to earth through the compen- 
sating rheostat. This arrangement forms a du- 
plex system, the outgoing currents of which have 
no effect on the home relays. 

Resistances R 2 and R 3 , are connected to the 
batteries 1 and 2, and the stops in the increment 
key in the manner shown, to the resistance of R 2 
and R 3 . The former is used in order to main- 
tain the resistance of the circuit, whether the bat- 
tery is in or out of circuit. The latter is called 
the spark coil, and is intended to decrease the 
sparking on closing circuit. 

When both are at rest, battery I, has its zinc 
connected to line through A, and its copper to 
earth through R 2 , CI, the lever of key B and 
key A, which last two are permanently connect- 
ed. A reversed or spacing current goes to line, 
without affecting the home relays, since it passes 
in opposite directions and with equal strength 
through differentially wound coils. 

When, however, the key A, is worked alone, 
it reverses the current and the signal is recorded 
by the distant relay A. 

If key B, is worked alone, it breaks connection 
with copper at the junction of the two batteries, 
and makes contact with terminal copper of battery 
2, so as to send a zinc current of threefold strength. 
The distant relay B, records a signal because the 
current is now strong enough to move it. Relay 
A, however, is not affected, since the current has 
not been reversed. 

When both keys are simultaneously in action, 
then whenever B, is pressed, although the strength 
of A, may be increased, since its direction is not 
changed, the polarized tongue of its relay is un- 
affected by the movement of B, but any increase 
of current causes the armature of the distant re- 
lay of B, to move. 

This armature is held in position by springs of 
such a strength as to prevent its motion by a 
weak current, and being unpolarized, responds to 
either positive or negative currents. It, there- 
fore, responds to B, and records a signal. When 
A, is pressed, it reverses the current, and conse- 
quently moves the distant relay A, but has no 
effect on B, since it causes no alternation in the 
strength of the current. . 

The author has taken the above almost liter- 
ally fromCulley's " Handbook of Practical Teleg- 
raphy , ' ' to which the reader is referred for a fuller 
description and details of apparatus. 



Tel.] 



514 



[Tel, 



Telegraphy, Simplex A system of 

telegraphy in which a single message only 
can be sent over the line. 

Telegraphy, Single-Needle A sys- 
tem of telegraphy by means of which the 




Fig. S 35' Single-Needle Telegraphic Apparatus. 

signals transmitted are received- by observing 
the movements of a vertical needle over a 
dial. 




of the observer represent the dashes, and move- 
ments to the left, the dots of the Morse alpha- 
bet. 

The single-needle apparatus of Wheatstone and 
Cooke's system is shown in Figs. 535, and 536. 
Fig. 535, shows the external appearance, and Fig. 




Fig. S3 6. Wheatstone and Cooke's Single- Needle Appa- 
ratus, Internal Arrangement. 

Movements of the top of the needle to the right 



Fig. 537. Wheatstone and Cooke's Single-Needle Ap- 
paratus, External View. 

536, the internal arrangements as seen from the 
back. An astatic needle is placed inside two coi) 
of insulated wire C C. Only 
one of these needles N, is vis- 
ible on the face of the receiving 
instrument. The current from 
the line enters at L, passes 
through the coil C C, and 
leaves at N. 

The movements of the needle 
to the right or the left are ob- 
tained by changing the direc- 
tion of the current in the coils" 
C C. This is effected by work- 
ing the handle when sending, 
and thus moving the commuta- 
tor at S, S, and bringing the 
contact springs resting thereon 
into different contacts. 

In the more modern form of single-needle in- 
strument, shown in Fig. 537, a single magnetic 
needle N S, Fig. 538, only is placed in the 
coil. 

This needle is rigidly attached to a light needle 
- a, b, used only as a pointer, and is alone visible 
in the front of the instrument. The relative dis- 
position of these needles is shown in Fig. 538. 

The reversals of the current, required to deflect 
the needle to the right or left, are obtained by 




Fig. 53$. Needle 
and Pointer. 



Tel.] 



515 



[Tel. 




means of a dotible key or tapper, shown in Fig. 

539- 

The levers L and E, are connected respectively 
to line and earth, and, when not in use, rest against 
C, connected with the positive 
side of the battery ; but when de- 
pressed connect with Z, attached 
to the negative side of the bat- 
tery. 

The depression of L, therefore, 
sends a negative current into the 
line and deflects the needle, say, 
to the left, while the depression 
of E, sends a positive current into 
the line and deflects the needle Fig. 33 g. Double 
to the right. The terms positive Key or Tapper. 
and negative currents are used in telegraphy to 
indicate currents whose direction is positive or 
negative. 

Telegraphy, Speaking- A system 

for the telegraphic transmission of articulate 
speech. (See Telephone.) 

Telegraphy, Step-by-Step A sys- 
tem of telegraphy in which the signals are 
registered by the movements of a needle over 
a dial on which the letters of the alphabet, 
etc., are marked. 

Dial telegraphs are especially employed for 
communication by those who are unable to readily 
read the Morse characters. 

The annexed instrument, devised by Breguet, 
was formerly used on some of the railway sys- 
tems of France. 

A needle advances over a dial by a step-by-step 




Fig. 540. Step-by Step Wheel. 

movement in one direction only. The alternate 
to-and-fro motions of the armature of an electro- 
magnet are employed to impart a step-by-step 
mot. on to a peculiarly shaped toothed wheel 



T, T, Fig. 540, through the action of a horizontal 
armc, attached thereto, and moving between the 
two prongs of a fork d, vibrating on a horizontal 
axis to which is attached a vertical pallet i. 

The receiving instrument is called the indicator, 
and consists of a needle attached to the axis of 
this wheel. The needle moves over the face of 




Fig. 541, Breguet' s Indicator. 

the dial, shown in Fig. 541, on which are marked 
the letters of the alphabet and the numerals. 

The sending instrument is called the manipu. 
lator. It consists of a device for readily sending 
over the line the number of successive impulses 
required to move the needle step-by-step from 
any letter on the indicator to which it may be 
pointing, to the next it is desired to send. 

The dial, shown in Fig. 542, is marked on its 
face with the same characters as the indicator. 
The edge of the wheel is provided with twenty-six 
notches in which a pin attached to a movable arm 
engages. The arm is jointed so that it can be 
placed in any of the notches on the face of the 
wheel. 




Fig. 342. Breguet' s Manipulator. 

Below the dial face, and attached to the same 
axis as the movable arm, is a wheel provided 
with undulations consisting of thirteen elevations 
and thirteen depressions. 



Tel.] 



516 



[Tel 



A lever T, pivoted at a, rests in these undu- 
lations at its upper end, and plays between two 
contact points at P and Q. 

If, now, the dials of the indicator and the man- 
ipulator both being at O, a movement is given to 
the arm by the handle M, to any point on the 
manipulator, there are thus produced the required 
number of makes and breaks to move the needle 
of the indicator to the corresponding letter or 
character. 

Telegraphy, Submarine A system 

of telegraphy in which the line wire consists 
of a submarine cable. 

In long submarine cables, in order to avoid 
retardation from the. self- induction of the cur- 
rent, and the static charge arising from the cable 
acting as a condenser, very small currents are 
used. To detect these a very sensitive receiving 
instrument, such as the mirror galvanometer, or 
the siphon recorder, is employed. (See Galva- 
nometer, Mirror. Recorder, Siphon.) 

According to Culley, the retardation in the 
case of one of the submarine cables between 
Newfoundland and Ireland, amounts to two- 
tenths of a second before a signal sent from one end 
produces any appreciable effect at the other end, 
while three-tenths of a second are required for the 
current through the cable to gain its full strength. 

Telegraphy, Synchronous- M u 1 1 i p 1 e x, 

Delany's System A system devised 

by Delany for the simultaneous telegraphic 
transmission of a number of messages either 
all in the same direction, or part in one direc- 
tion and the remainder in the opposite direc- 
tion. 

The Delany system embraces the following 
parts : 

(i.) A circular table of alternately insulated 
and grounded contacts at either end of a tele- 
graphic line. 

(2.) A synchronized rotating arm or trailing 
contact, at each end of the line, driven by a 
phonic wheel, and maintained in synchronous 
rotation by means of electric impulses automatic- 
ally sent out over the main line in either direc- 
tion, on the failure of the wheel at either end to 
rotate synchronously with that at the other end. 

(3.) Transmitting and receiving instruments 
connecting similar contacts at each end of the 
main line, and forming practically separate and 
independent lines for the simultaneous transmis- 



sion of dispatches over the main line in either 
direction. 

The main line is simultaneously connected at 
both of its ends to corresponding operating in- 
struments, and transferred from one set of instru- 
ments to another so rapidly that the operators, 
either sending or receiving, cannot realize that 
the line has been disconnected from their instru- 
ments and given to others, because each of them 
will always have the line ready for use, even at 
the highest rate of manipulation, and will, there- 
fore, to all practical intents and purposes, have 
at his disposal a private wire between himself 
and the operator with whom he is in communica- 
tion. 

Therefore, although more than one operator 
may be spoken of as simultaneously using the 
line at any given time, yet in reality no two ope- 
rators are absolutely using it at the same time; 
but they follow one another at such short in- 
tervals, and the line is taken from one operator 
and transferred to another so rapidly, that none 
of them can at any time tell but that he has the 
line alone, and that therefore it is practically 
open for the use of every operator just as if he 
alone had control of it. 

There will, therefore, be established, by the 
use of a single line, as many private and separate 
lines as there are transferences of the line from 
the time it is taken from the first operator, and 
again given back to him. 

This system has been extended to as many as 
seventy-two distinct and separate printing cir- 
cuits, maintained and operated on a single con- 
necting line wire. 

The speed at which the circuits may be operated 
is in the inverse order of the number of circuits 
organized. The best results, practically, are 
obtained from six divisions of the contacts in the 
circle, which gives each operator about 36 cont- 
racts with the line per second, a speed which ad- 
mits of the highest rate of transmission on each of 
the six circuits. 

Fig. 543 shows the apparatus at each end of 
the line, at the stations X and Y. The apparatus 
at each end is substantially identical. A steel 
fork a, at each station, is automatically and con- 
tinuously vibrated by the action of the local bat- 
tery L, B, and the electro-magnet A, called the 
vibrator magnet. 

Platinum contacts x, x 1 , placed on the inner 
faces of the tines of the fork, make and break 
contact with delicate contact springs y, y 1 . 



Tel.] 



517 



[Tel. 



The fork being mechanically started into a 
vibratory motion, will automatically make and 
break its local circuit, and thus send impulses 
into the fork magnet A, that will continuously 
maintain the vibrations of the fork, in a well 
known manner. 

The making and breaking of the contacts x 
and y, consequent on the fork's vibration, open 
and close another local battery placed in a circuit 
called the motor circuit, in which is also placed an 
electro-magnet D, the function of which is to 
maintain the continuous rotation of the trans- 
mission apparatus C. 



disc C, is rotated by the electro-magnet D, the 
trailing contact f, sweeps around the circular 




Fig. 543. Delany's Synchronous Mtitiplex Telegraph. 

The continuous vibration of the fork makes and 
breaks the contacts at x and y, and thereby 
makes and breaks the motor circuit. The alter- 
nate magnetizations and demagnetizations of the 
cores of the motor-magnet D, cause the rotation 
of the transmission apparatus C. 

The motor magnet and transmission wheel or 
disc C, provided with projections c, c, is the in- 
vention of Paul La Cour, and is styled by him a 
" phonic wheel." 

The transmission apparatus is illustrated in de- 
tail in Figs. 544 and 545, and is an exact coun- 
terpart of the receiving apparatus at the other 
end of the line. A base plate E, provided with 




Fig. 544- The Phonic Wheel. 
binding posts, carries a vertical rotary shaft F. 
A circular table F 1 , is provided with a series of 
insulated contacts arranged symmetrically around 
the axis of rotation of the shaft. A radial arm F z , 
connected with the shaft F, carries at its outer 
extremity a trailing contact finger f. As the 




Fig' 345- The Phonic Wheel. 
table F 1 , and is brought successively into contact 
with the insulated contact pieces placed on the 
upper face of the table F 1 . 

The main line Q, Q, has one of its ends con- 
nected with the trailing finger f. As the shaft 
F, rotates, the line is therefore brought into suc- 
cessive electrical connection with the series of in- 
sulated contacts in the upper face of the table 
F*. 

Any suitable number of insulated contacts may 
be placed on the circular table F 1 ; sixty are 
shown in Fig. 546. In practice these contacts 
are connected in accordance with the number of 
circuits which it is desired to simultaneously 
maintain on the same wire. In the special case 
shown in the figure above referred to, it is ar- 
ranged so that four separate circuits shall be 
established on the same line wire. 

The sixty contacts are placed in six indepen- 
dent series, numbered from 1 to 10, consecu- 
tively. In the arrangement here shown two of 
the contact pieces in each series of ten are con- 
nected in the same circuit, and, as there are six 
series, each of the circuits so connected will have 
twelve contacts for each rotation of the disc, and 
twelve electrical impulses, as will be afterwards 
described. 

The detailed mechanism, by means of which 
the separate and independent circuits so obtained 
are utilized for the transmission and reception of 
messages, is shown in Fig. 546. R, R 1 , R 2 and 
R 3 , are polarized relays; S, S 1 , S 2 and S :J are 
ordinary Morse sounders, although in the practice 
of this invention some improvement has been in- 
troduced in connection with the receiving instru- 
ments. The connections with the main and the 
local batteries M B and L B, are clearly shown 
in the figure. 

It will be noticed that the relay R, is connected 



Tel.] 



518 



[Tel. 



with the wire r, and with the contacts I and 5 ; 
R 1 is connected by r 1 , with the contacts 2 and 6, 
R 2 , by the wire r 8 , with the contacts 3 and 7, 
and R 3 , by the wire r 3 , with the contacts 4 and 
8. Similar instruments and circuits are placed 
at each end of the line. 

Without further describing the operation of the 
instruments shown in the figure, it need only now 
be borne in mind that the corresponding relays at 
the distant stations are connected with the corre- 
spondingly numbered contacts. When, therefore, 
the trailing contact finger at each station simul- 
taneously touches the contacts bearing the same 
number, the corresponding instruments connected 







Fig. 546. Working and Receiving Currents. 

with these contacts at each station will be placed 
in communication over the main line, the trailing 
contact finger f, completing the connection of 
the main line with the contact arm in the man- 
ner already described. 

Telegraphy, Time A system for 

the telegraphic transmission of time. 

A system of time telegraphy includes a master 
clock, the movements of whose pendulum automati- 
cally transmit a number of electric impulses to a 
number of secondary clocks and thus moves them; 
or self-winding clocks are employed, which are 
corrected daily by an impulse sent over the line 
from a master clock. (See Clock, Electric.') 

Telegraphy, Writing- A species of 

fac-simile telegraphy, by means of which 
the motions of a pen attached to a transmit- 
ting instrument so vary the resistance on 
two lines connected with a receiving instru- 
ment as to cause the current received thereby 
to reproduce the motions, on a pen or stylus, 
which transfers them to a sheet of paper. 



A system of writing telegraphy consists 
essentially of transmitting and receiving in- 
struments connected by a double line wire. 

The transmitting instrument is shown in Fig. 
547. 




Fig. 547. Transmitter of Writing Telegraphy. 

A stylus or pen resting on a top plate, is con- 
nected by the rod C, with a series of steel contact 
springs S, S, secured to the base and placed at 
right angles to one another. A series of resist- 
ances R, R, are connected with the lower ends 
of these contact springs. Two contact bars, 
B, B, are provided on the side facing the springs 
with platinum contacts opposite the contacts on 
the springs. The stylus rod C, is securely fixed 
to the base, but a spring at the lower end per- 
mits of its free movement. A pressure block at 
P, is fastened to the stylus rod, as shown, and in 
its normal position the pressures are adjusted so 
that contact is secured with the first spring. 

A movement of the stylus, as in writing, 
presses the contact bar against the spring, vary- 
ing the position and number of contacts, and 
thereby cutting in or out the resistance necessary 
to effect the proper movement of the receiving 
pen. 

The receiving instrument is shown in Fig. 548. 
It consists of two electro-magnets placed at right 
angles to each other. A double armature sup- 



Tel.] 



519 



[Tel, 



ports the receiving stylus or pen in the manner 
shown. The variations in the current sent over 
the line by the varying resistances introduced 
into the circuit, or cut out or in by the action of 
the transmitting stylus, causes variations in the 
position of the double armature, under the vary- 
ing magnetic attraction of the receiving electro- 
magnet, and thus causes the receiving pen to 
correctly reproduce the motions of the trans- 
mitting pen. 




F*g' 54$' Receiver of Writing Telegraph. 

This system has been operated over a line 
nearly 500 miles in length, when it successfully 
reproduced written characters. 

The author is indebted for the drawings and 
the general facts to the Electrical Engineer of 
New York. 

Tele-Hydro-Barometer, Electric 

An apparatus for electrically transmitting to, 
and recording at a distant station the height 
of water or other liquid. 
Tele-Manometer, Electric — A 

gauge for electrically indicating and record- 
ing pressure at a distance. 

The tele-manometer includes a pressure gauge 
furnished with electric contacts operated by the 
movements of the needle of the steam gauge, for 
instance, and indicating and recording apparatus. 
An alarm bell is provided to call attention to any 



rise of the pressure above or its fall below the 
given or predetermined limits for which the 
hands have been set. 

Telemeter. — An apparatus for electrically 
indicating and recording at a distance the 
pressure on a gauge, the reading of a ther- 
mometer, or the indications of similar in- 
struments. (See Tele-Hydro-Barometer, 
Electric. Tele-Manometer, Electric. Tele- 
Thermometer, Electric?) 

Telephone.— To communicate by means 
of a telephone. 

Telephone. — An apparatus for the electric 
transmission of articulate speech. 

The articulating telephone, though first 
brought into public use by Bell, was invented by 
Reis, in Germany, in 1861. In America, after 
very protracted litigation, Bell has been decided 
legally to be the first inventor, but scientific men 
very generally recognize the principles of the, in- 
vention to be fully anticipated by the earlier in- 
struments of Reis. Bell, however, is uistly en- 
titled to the credit of inventing the first really 
successful telephone. 

In Bell's magneto -electric telephone, the 
transmitting and receiving instruments are iden- 
tical. A coil C, of insulated wire connected with 
the line, is placed on a core of magnetized steel, 
mounted opposite the centre of a circular dia- 
phragm of thin sheet iron, rigidly supported at 
its edges. 

In transmitting, the message is spoken into the 
mouth-piece at one end, as at D, in Fig. 549, and 
the to-and-fro motions thus p 

imparted to the metallic 
diaphragm attached to the 
mouth-piece P, produce in- 
duction currents in the coil 
C, on the magnet M. (See In- 
duction, Electro -Dynamic.) 
These impulses, passing over 
the main line E L, Fig. 550, 
produce similar movements 
in the diaphragm P', of the 
receiving instrument, at D', _ 
and thus cause it to repro- 
duce the message, in articu- F %- S49- Telephone. 
late sounds, to one listening at the receiving in- 
strument. A ground circuit is shown in the 
figure, as usually employed in practice, except 
for long distance and in large cities. 




Tel.] 



520 



[Tel. 



A magneto-telephone constitutes in reality a 
magneto-electric machine, driven or propelled by 
the voice of the speaker, in which the currents 
so produced instead of being commuted are em- 
ployed uncommuted to reproduce the uttered 
speech. 

In actual practice the instrument above de- 
scribed is replaced by the electro-magnetic tele- 

E 

Cpl M' 




Fig- SS°- 



B — Jf 

Telephone Circuit, 




phone, in which the to-and-fro motions of the 
transmitting diaphragm are caused to vary the 
resistance of a button of carbon, or a variable con- 
tact transmitter similar to 
that employed by Reis in 
some of his instruments. 
The variable resistance 
is placed in the circuit of 
a battery, so that on 
speaking into the trans- 
mitter, electric impulses 
are sent over the line and 
are received by a tele- 
phone with a magnet core 
provided with a coil in the 
main-line circuit. 

The telephone is ar- 
ranged for actual com- 
mercial use in the United 
States in the manner Fig. 531. Telephone Ap- 
shown in Fig. 551. paratus. 

Telephone, Bi A term sometimes 

applied to a double telephone receiver so ar- 
ranged as to permit of easy application to 
both ears of the listener at the receiving in- 
strument. 

Telephone Cords.— (See Cords, Tele- 
phone.) 

Telephone, Electro-Capillary A 

telephone in which the movements of the 
transmitting diaphragm produce currents by 
means of variations in the electromotive 
forces of the contact surfaces of liquids in 
capillary tubes. (See Phenomena, Electro- 
Capillary^) 

In Breguet's telephone both the transmitting 
and the receiving: instruments are similar in con- 



struction and operate by means of electro-capil- 
lary phenomena. A vertical capillary tube com- 
municates at its upper end with an air space 
below a diaphragm, and at its lower end with a 
mercury surface on which rests a layer of acidu- 
lated water. 

A line wire connects the mercury reservoirs of 
the transmitting and receiving instruments, the 
remainder of the circuit being formed by another 
wire connecting the mercury near the upper parts 
of the two vertical tubes. 

The alterations in the contact surfaces at the 
transmitting end produced by the movements of 
the diaphragm, cause electric impulses that pro- 
duce similar movements of the diaphragm at the 
receiving end. 

Telephone, Electro-Chemical — A 

name sometimes given to the Edison electro- 
motographic telephone. (See Telephone, 
Electro-Motograph ic.) 

Telephone, Electro-Motographic 

A telephone in which the receiver consists of 
a diaphragm of mica or other elastic material 
operated on the principle of the electro- 
mot ograph. 

A straight lever, which forms part of the line 
circuit, is rigidly attached at one end to the centre 
of the receiving diaphragm, and rests near its 
other end on the surface of a chalk cylinder 
moistened with a solution of caustic potash or 
potassium iodide, maintained in rotation by suit- 
able mechanical means. 

Electric impulses being sent into the line by the 
voice of a speaker talking at a transmitter of ordi- 
nary construction reduce the friction between the 
lever and the cylinder, and produce slipping 
movements of the lever that reproduce articulate 
speech in the receiving diaphragm. 

Telephone, Reaction An electro- 
magnetic telephone in which the currents in- 
duced in a coil of wire attached to the dia- 
phragm are passed through the coils of the 
electro-magnet, and thus react on and 
strengthen it. 

Telephone Switch, Automatic (See 

Switch, Telephone, Automatic?) 

Telephonic. — Pertaining to the telephone. 

Telephonic Alarm. — (See Alarm, Tele- 
phonic?) 



Tel.] 



521 



[Tel. 



Telephonic Cable. — (See Cable, Tele- 
phonic.) 

Telephonic Exchange. — (See Exchange, 
Telephonic, System of.) 

Telephonic Exchange, System of 

(See Excha?ige, Telephonic, System of.) 

Telephonic Joints. — (See Joint, Tele- 
graphic or Telephonic?) 

Telephonically.— In the manner of the 
telephone. (See Telephone?) 

Telephoning 1 . — Communicating by means 
of the telephone. 

Telephote. — An apparatus for the tele- 
graphic transmission of pictures by means of 
the action of light on selenium. (See Tele- 
photography.) 

The telephote is sometimes called the pherope. 

Telephotography. — A system for fac- 
simile transmission by means of dots and 
lines transmitted by means of a continuous 
current whose intensity is varied by a trans- 
mitting instrument containing a selenium re- 
sistance. (See Telegraphy, Tac-Simile. 
Resistance or Cell, Selemum?) 

The transmitter consists of a dark box mounted 
on an axis, so as to be capable of a sidewise 
motion. The picture to be transmitted is 
thrown continuously on the face of the box by 
any lantern projection apparatus, and a small 
opening containing a selenium resistance receives 




wise continuous current in the circuit of which the 
selenium resistance is placed. 

The picture is received at the other end on a 
sheet of chemically prepared paper moved syn- 
chronously with the transmitting box. 

Telescope, Reading A telescope 

employed in electric measurements for read- 
ing the deflections of the galvanometer. 

The image of numbers on an illumined scale is 
seen in the mirror through the telescope, shown 
in Fig. 552. 

Teleseme.— A self-registering hotel an- 
nunciator, by means of which a dial operated 
in a room indicates on the annunciator the 
article or service required. 

Tele-Thermometer, Electric — An 

electric recording thermometer for indicating 
and recording temperature at a distance. 

The tele-thermometer consists essentially of a 
transmitter and a receiver. The transmitter 
consists of a delicate thermometer provided with 
suitable contacts. The receiver, which is in 
circuit with the transmitter, has, in some forms, 
a recording dial on which a continuous record, 
for a day or week, is made. In cases where it is 
desired that a given maximum temperature shall 
not be exceeded, an alarm bell, connected with 
contacts on the dial face, is rung. 

Telluric Magnetic Eorce. — (See Force, 
Magnetic, Telluric?) 

Telpher Line. — (See Line, Telpher?) 
Telpherage.— A system for the convey- 
ance of carriages suspended from electric 




Fig. 552. Reading Telescope. 

the alternations of light and shade, and transmits 
the same as variations in the strength of the other- 



Fig. SS3- Circuit for Telpherage System. 

conductors, and driven by means of electric 
motors, that take directly from the conductors 
the current required to energize them. 



Tem.] 



522 



[The. 



Two lines are provided, an up and a downline, 
that cross each other at regular intervals. Each 
line is in segments, and the alternate segments 
are insulated from each other, but are connected 
electrically by cross-pieces on the supporting 
posts. In this way the line shown in Fig. 553 is 
obtained. 

The two lines are maintained at a difference of 
potential by a dynamo-electric machine at D, 
Fig. 554. As the train at L T, or L' T', is of 
such a length as to come into contact with two 
different segments at the same time, it receives a 
current sufficient to run the motor connected with 
it, the current being received through a conduc- 
tor joining a pair of wheels that are insulated 
from the truck. 

The general arrangement of the line is shown 
in the annexed Fig. 554 




Fig. 55 4> Circuit/or Telpherage System. 

Temperature Alarm. — (See Alarm, Tern- 
perature^ 

Temperature, Effects of, on Electric Re- 
sistance (See Resistance, Effect of 

Heat on Electric?) 

Tempering, Electric —A process 

for temperaing metals in which heat of elec- 
tric origin is employed instead of ordinary 
furnace heat. 

Temporary Intensity of Magnetization. — 

(See Magnetization, Temporary Intensity 
of.) 

Tension, Electric A term often 

loosely applied to signify indifferently surface 
density, electromotive force, dielectric stress, 
or difference of potential. 

This term is now very generally abandoned. 

Terminal, CaMe — — —A water-tight 
covering provided at the end of a cable to 
prevent injury to the cable insulation by the 
moisture of the air. 

Terminal, Negative The negative 

pole of a battery or other electric source, or 
the end of the conductor or wire connected 
with the positive plate. 



Terminal, Positive The positive 

pole of a battery or other electric source, or 
the end of the conductor or wire connected 
to the negative plate. 

Terminals. — A name sometimes applied 
to the poles of a battery or other electric 
source, or to the ends of the conductors or 
wires connected thereto. 

The two terminals are distinguished as the 
positive and the negative. Their names are un- 
like those of the battery plates to which they 
are connected, the positive terminal being con- 
nected with the negative plate and the negative 
terminal with the positive plate. 

Terrestrial Magnetism. — (See Magnet- 
ism, Terrestrial?) 

Testing, Methods of —Various 

methods for determining the values of the 
current strength in any circuit, the difference 
of potential, the resistance, the coulombs, 
the farads, the joules, the watts, etc. (See 
Measurements, Electric?) 

The investigation of an apparatus or cir- 
cuit for the purpose of determining whether 
it is in standard or working condition. 

Testing of Joints. — (See Joint, Test- 
ing of.) 

Testing Pole.— (See Pole, Testing^ 

Testing Transformer. — (See Trans- 
former, Testing?) 

Tetanus. — Continuous, spasmodic contrac- 
tion of the muscles. 

Tetanus, Acoustic Tetanus pro- 
duced in a muscle by means of alternate 
currents induced in a coil of wire by a mag- 
netized steel spring vibrating near the coil 
with sufficient rapidity to give a musical note. 

The rapidity of the inductive shock can be de- 
termined from the pitch of the musical note; hence 
the use of the term acoustic. 

Theatrophone. — A system of telephonic 
communication between theatres or operas 
and subscribers, by means of slot machines. 

Any person at a cafe, club, restaurant or other 
public place, by the theatrophone, is automati- 
cally placed in communication with the theatre 
by means of a receiving telephone so as to hear 



The.] 



523 



[The. 



the performance by dropping a given piece of 
money in the slot of the machine. 

Theodolite, Magnetic — An appa- 
ratus for measuring the declination or varia- 
tion of the magnetic needle at any place. 

A divided circle, like that on a theodolite, is 
supported horizontally. The needle is formed of 
a tubular magnet, having an achromatic lens at 
one end and a scale at the focus of the lens at the 
other end. 

Theory, Alternation, of Muscular Nerve 

Current — A theory proposed by L. 

Hermann, in which the currents of nerves or 
muscular fibres are regarded as a result of 
their alteration from an original condition. 

Hermann states: 

(i.) That protoplasm undergoing partial death 
at any part, either while dying or by metamor- 
phosis, becomes negative to the uninjured part. 

(2.) Protoplasm, when excited at any part, be- 
comes negative to the unexcited part. 

(3.) Protoplasm, when partially heated at any 
part, becomes positive, and, on cooling, negative 
to the unchanged part. 

(4. ) Protoplasm is strongly polarizable on its 
surface, the polarization constantly diminishing 
with excitement and while dying. 

According to this theory, passive, uninjured 
and absolutely fresh tissues are devoid of elec- 
tric currents. This matter must still be regarded 
as unsettled. (See Theory, Molecular, of Mus- 
cles or Nerve Current. ) 

Theory, Contact, of Toltaic Cell 

(See Cell, Voltaic, Contact Theory of.) 



Theory, Difference 



-A theory as to 



the cause of the electric currents excited be- 
tween injured and uninjured protoplasm. 

Theory, Molecular, of Muscles or Nerve 

Current A theory proposed by Du 

Bois Reymond, in which every nerve or mus- 
cular fibre is regarded as composed of a 
series of electromotive molecules arranged 
in series and surrounded by a neutral con- 
ducting fluid. 

" The molecules are supposed to have a posi- 
tive equatorial zone directed towards the surface 
and two negative polar surfaces directed toward 
the transverse section. Every fresh transverse 
section exposes new negative surfaces, and every 



artificial longitudinal section new positive area." 
— (Landois and Sterling. ) 

Theory of Electric Displacement. — (See 
Displacement, Electric, Theory of.) 

Therapeutical Electrization. — (See Elec- 
trization, Therapeutical.) 

Therapeutic Bath, Electro —(See. 

Bath, Electro- Therapeutic) 

Therapeutics, Electro, or Electro- 
Therapy The application of electricity 

to the curing of disease. (See Biology, Elec- 
tro) / 

Therapeutist, Electric One skilled 

in electro-therapy. 

An electro-medical practitioner. 

Therapy, Electro — A term some- 
times used instead of electro-therapeutics. 
(See Therapeutics, Electro, or Electro- 
Therapy) 

Therapy, Magneto Alleged electro- 
therapeutic effects produced by the move- 
ments of magnets over the body of the 
patient. 

It is asserted by eminent authorities that such 
effects have an actual existence. They should, 
however, until more carefully investigated, be 
accepted with extreme caution. 

Therm.— A heat unit proposed by the 
British Association. 

A therm is the amount of heat required to 
raise the temperature of one gramme of pure 
water at the temperature of its maximum density 
one degree centigrade. (See Calorie.) 

Therniaesthesiometer.— An instrument 
employed in electro-therapeutics for testing 
the temperature sense in nervous diseases. 

The thermaesthesiometer consists of two ther- 
mometers movable on a standard, with flat ves- 
sels of mercury in order to readily apply them to 
the skin. The mercury vessel of one of the two 
thermometers is surrounded by an insulated 
platinum wire and may be warmed at pleasure by 
passing a galvanic current through the wire. 

The two vessels, brought to different tempera- 
tures, are set on the same part of the skin, one 
after the other, so as to test the sensibility of the 
skin for the differences in temperature. 

Thermal Absorption.— (See Absorption. 
Thermal) 



The.] 



524 



[The. 



Thermal Cautery. — (See Cautery, Ther- 
mal) 

Thermal Incandescence. — (See Incan- 
descence, Thermal) 

Thermic Balance. — (See Balance, Ther- 
mic, or Bolometer) 

Thermo-Battery.— (See Battery, Thermo) 

Thermo Call. — A call operated by means 
of thermo currents. 

Thermo-Cell.— (See Cell, Thermo-Elec- 
tric^ 

Thermo-Electric Battery. — (See Battery t 
Thermo-Electric ) 

Thermo-Electric Cell.— (See Cell, 
Ther?no-Electric) 

Thermo-Electric Couple. — (See Couple, 
Thermo-Electric) 

Thermo-Electric Diagram. — (See Dia- 
gram, Thermo-Electric) 

Thermo-Electric Effect.— (See Effect, 
Th enno-Electric) 

Thermo-Electric Inversion. — (See Di- 
version, Thermo-Electric) 

Thermo-Electric Pile, Differential ■ 

— (See Pile, Thermo, Differential) 

Thermo-Electric Pile or Battery. (See 

Pile, Thermo-Electric) 

Thermo-Electric Power. — (See Power, 
Thermo-Electric) 

Thermo-Electric Series. — (See Series, 
Thermo-Electric) 

Thermo-Electricity.— (See Electricity, 
Thermo) 

Thermo-Electrometer. — A name some- 
times, but not happily, applied to an electric 
thermometer. (See Thermometer, Electric) 

Thermo-Electromotive Force. — (See 
Force, Electrojnotive, Thermo) 

Thermolysis.— A term applied to the 
chemical decomposition of a substance by 

heat. 

Thermolysis, or dissociation, is an effect pro- 
duced by an action of heat somewhat similar to 
the effect of electrolysis, or chemical decomposi- 
tion produced by the passage of an electric cur- 
rent. When a chemical substance is heated, the 



vibration of its molecules is attended by an inter- 
atomic vibration of its constituent atoms so that a 
decomposition ensues. If the temperature is not 
excessive, these liberated atoms recombine with 
others which they meet. At higher temperatures, 
however, such recombination is impossible, and a 
permanent decomposition ensues, called ther- 
molysis or dissociation. 

Thermometer, Electric A device 

for determining the effects of an electric dis- 
charge by the movements of a liquid column 
on the expansion of a confined mass of air 
through which the discharge is passed. 

Thermometer, Electric Resistance 

— A thermometer the action of which is 
based on the change in the electric resistance 
of metallic substances with changes in tem- 
perature. 

The electric resistance thermometer is used, 
among other purposes, for determining the temper- 
ature of the sea at different depths. Its operation 
is based on the electric resistance of two perfectly 
similar coils of insulated wire, enclosed in separate 
water-tight copper cases. One coil is placed where 
the temperature is to be determined, and the other 
in a vessel of water, the temperature of which is 
altered until the two coils show the same resist- 
ance, when, of course, the temperature of the 
distant coil is the same as that of the water sur- 
rounding the other coil. 

Thermometer Scale, Centigrade 

(See Scale, Ther?no7neter, Centigrade) 

Thermometer Scale, Fahrenheit 

(See Scale, Thermometer, Fahrenheit) 

Thermophone. — Any instrument by means 
of which sounds are produced by the absorp- 
tion of radiant energy. (See Photophone) 

A telephone has been constructed in which the 
motions of the receiving diaphragm are effected 
by the expansions and contractions of a thin me- 
tallic wire connected to the diaphragm and placed 
in the circuit of the main line. 

Thermostat. — An instrument for automati- 
cally maintaining a given temperature by the 
closing of an electric circuit through the ex- 
pansion of a solid or liquid. 

Thermostats are often used in systems of auto- 
matic fire telegraphy and in systems of automatic 
temperature regulation in connection with indi- 



The.] 



525 



[Tic. 



eating instruments for sounding an alarm or giv- 
ing notice when the temperature changes. 

They are operated either on open or closed cir- 
cuits. 

Thermostat Alarm. — (See Alarm, Ther- 
mostat?) 

Thermostat, Closed-Circuit — A 

thermostat maintained normally on a closed 
circuit. 

In closed-circuit thermostats, the adjustment 
for any degree of temperature within a given 
range is effected by means of a screw. 

Thermostat, Electro-Pneumatic 

An instrument for automatically indicating 
the existence of a given temperature by the 
closing of an electric circuit on the expansion 
of a gas. 

Thermostat, Mercurial A thermo- 
stat operating by the ex- 
pansion of a mercury 
column. 

A mercurial thermostat 
is shown in Fig. 555. One 
terminal is connected di- 
rectiy with the mercury; 
the other is placed in the 
arm to the left. On a cer- 
tain predetermined tem- 
perature being reached, the 
rise of the mercury column 
completes the circuit and 
rings an alarm bell. By 
connecting the thermostat 
with an annunciator, the 
particular locality where an 
excessive temperature has 
been reached is indicated. 
Such a system is in use in a well known system of 
fire alarm. 

Thermostat, Open-Circuit A ther- 
mostat maintained normally on an open cir- 
cuit. 

In open-circuit thermostats the adjustment for 
temperature within a given range is effected by 
varying the distance of the fixed and movable 
contact points. 

Thermostatic. — Of or pertaining to a ther- 
mostat. (See Thermostat) 

Thompson's Gauss. — (See Gauss, S. P. 
Thompson s.) 




Fig. SSS' Mercurial 
Ttiermostat. 



Thomson's Gauss. — (See Gauss, Sir Wil- 
liam Thomson's.) 

Three-Branched Sparks.— (See Spark, 
Three-Branched?) 

Three-Filament Incandescent Electric 
Lamp for Multiphase Circuits. — (See Lamp, 
Electric, Inca?idescent, Three-Filament, 
for Multiphase Circuits?) 

Three-Way Trolley Frog.— (See Frog, 
Trolley, Three- Way.) 

Three-Wire System.— (See System, Three- 
Wire.) 

Throttling. — Choking, or stopping off. 

Through Circuit. — (See Circuit, 
Through?) 

Through Line.— (See Line, Through?) 

Throwback Indicator, Electrical 

(See Indicator, Electric Throwback?) 

Throwback Indicator, Mechanical 

— (See Indicator, Mechanical Throwback?) 

Throw of Needle. — (See Needle, Throw 
of.) 

Thumb-Cock Electric Burner.— (See 

Burner, Thianb-Cock Electric) 

Thunder. — A loud noise accompanying a 
lightning discharge. 

Thunder is due to the sudden rush of the sur- 
rounding air to fill the partially vacuous space 
accompanying the disruptive discharge of a cloud. 
This space is caused mainly by the condensation of 
the vapor formed on the passage of the discharge 
through drops of rain or moisture in the air, as 
well as by the expansion of the air itself. 

Thunder Rod.— (See Rod, Thunder:) 

Thunder Storms, Geographical Distribu. 
tion of (See Storms, Thunder, Geo- 
graphical Distributio7i of) 

Tick, Magnetic A faint metallic 

click heard on the magnetization and demag- 
netization of a magnetizable substance. 

Ticker Service, Stock The simul- 
taneous transmission of stock quotations or 
other desired information to a number of 
subscribers. 

The stock ticker-service includes a central 
transmitting station connected with a given num- 



Tic] 



526 



[Tis. 



ber of subscribers, each of whom is furnished 
with a stock ticker. The transmitter at the cen- 
tral station consists of a keyboard and a cylinder 
furnished with spiral pins. The spiral pins are 
connected through a series of pole-changers to 
separate line wires radiating in all directions from 
the central office. 

The connections are such that, a rapid rota- 
tion being given by means of an electric mo- 
tor to the cylinder, the impulses sent out by the 
keyboard are transmitted to each of the separate 
circuits. Since each of these circuits has a num- 
ber of ticker printers connected with it, reports of 
fluctuations in prices are simultaneously printed 
in hundreds of different offices. 



Time-Constant of Electro-Magnet. — (See 
Constant, Time, of Electro-Magnet.) 



Ticker, Stock 



-A form of step-.by- 



step telegraphic instrument employed for au- 
tomatically sending and recording stock quo- 
tations to any desired number of subscribers. 
(See Telegraphy, Step-by- Step.) 
A form of printing telegraph. 

Callahan's Printing Telegraph is used as a 
stock ticker. (See Telegraphy, Printing.) 

Phelps' Stock Printer is employed extensively 
as a stock ticker. This form of printing telegraph 
requires but a single wire, and has a working 
speed of almost thirty words a minute. 

A double type-wheel, maintained in motion by 
clockwork, is stopped at the desired characters 
by the motion of a polarized relay, working be- 
tween the poles of two electro magnets, furnished 
with a soft iron or non-polarized armature. The 
release of the armature of the printing mag- 
net releases a train, and thus insures the impres- 
sion of the character it is desired to print. 

The type-wheel is driven by a step-by-step 
movement obtained by means of rapidly alter- 
nating pulsations. Although these pass through 
the coils of the printing magnet, they follow one 
another too rapidly to charge its coils, so that the 
armature is unaffected until a pause is made, 
when, its armature being attracted, it releases 
the printing mechanism. The message is received 
on a fillet of paper, fed by a suitable mechanism. 

Time-Ball, Electric (See Ball, 

Electric Time?) 

Time-Constant of Circuit. — (See Circuit, 
Time-Constant of.) 

Time-Constant of Condenser. — (See Con- 
denser, Time-Constant of.) 



-An au- 



Time Cut-Out, Automatic — 

omatic cut-out arranged on a storage bat- 
tery so as to cut it in or out of the circuit of 
the charging source at predetermined times. 

Time-Fall of Electromotive Force of 
Secondary or Storage Cell During" Dis- 
charge. — (See Force, Electromotive, of Sec- 
ondary or Storage Cell, Time-Fall of.) 

Time-Lag of Magnetization.— (See Mag- 
netization, Time-Lag of.) 

Time, Reaction The time required 

for the effects of an electric current to pass 
from a nerve to a muscle. 

Time-Rise of Electromotive Force of 
Secondary or Storage Cells During Dis- 
charge. — (See Force, Electromotive, of Sec- 
ondary or Storage Cell, Time-Rise of.) 

Time-Switch. — (See Switch, Time) 

Time, Telegraphic, Register for Rail- 
roads (See Register, Ti7ne,for Rail- 
roads) 

Time Telegraphy. — (See Telegraphy, 
Ti?ne.) 

Tinned Wire.— (See Wire, Tinned) 

Tinning, Electro Covering a sur- 
face with a coating of tin by electro-plating. 
(See Plating, Electro) 

Stannic chloride, or the perchloride of tin, dis- 
solved in water in the proportion of 30 parts of the 
salt to 1,250 of water, makes a good tinning 
bath. 



-A professional 



Tinnitus, Telephone — 

neurosis, or abnormal nervous condition of the 
auditory apparatus, believed to be caused by 
the continual use of the telephone. 

Tips, Polar The free ends of the 

field magnet pole pieces of a dynamo-electric 
machine. 

Tissue, Nerve or Muscular Excitability 

of Electric stimulation of nervous or 

muscular tissue. 



Ton.] 



527 



[Tor. 



The general effects of electric stimulation of 
nervous or muscular tissue may be summarized 
as follows: 

(i.) Electric stimulation of a motor nerve, pro- 
duces a contraction of the muscles to which such 
nerve is distributed. 

(2.) Electric stimulation of a sensory nerve, 
produces pain in the parts to which the nerve is 
distributed. 

(3.) Electric stimulation of mixed motor and 
sensory nerves produces both of the effects men- 
tioned under (1) and (2.) 

Tongs, CaMe Hanger Tongs pro- 
vided with long handles for the purpose of 
attaching the hangers of an aerial cable to 
the suspending wire or rope. 



Tongs, Discharging 



A term some- 



times used for a discharging rod. (See Rod, 
Discharging) 

Tongue, Relay, Bias of A term 

employed to signify such an adjustment of a 
polarized relay, that on the cessation of the 
working current, the relay tongue shall 
always rest against the insulated contact, and 
not against the other contact, or vice versa. 

Sometimes, as in the split-battery duplex, the 
bias is toward the uninsulated contact. (See 
Relay, Polarized.) 

Tool, Lead Scoring A tool for 

readily scoring the surface of the lead of a 
lead-covered cable, when the same is to be 
removed preparatory to making joints. 

Toothed-Ring Armature.— (See Awna- 
ture, Toothed-Ring.) 

Top, Induction A top consisting 

of an iron disc supported on a vertical axis, 
which, when spun before the poles of a steel 
magnet, assumes an inclined position, through 
the influence of the currents induced in the 
disc. 

The top maintains the inclined position so long 
only as the strength of the induced currents is 
sufficiently great ; that is, while speed of rotation 
is sufficiently great. 

Toppler-Holtz Machine.— (See Machine, 
Toppler-Holtz) 
Torch, Electric Gaslighting A 

gaslighting appliance consisting of the com- 



bination of a portable voltaic battery and a 
spark or induction coil. 

The torch is mounted on the end of a rod pro- 
vided with means for turning on the gas. A key 
is then touched and the gas lighted by the spark 
produced by an induction coil or a small electro- 
static induction machine. 

Torpedo, Automobile A torpedo 

which contains in itself the power for its own 
motion. 

The moving power may be that derived from 
compressed air or gas, or from a storage bat- 
tery contained within the torpedo. An auto- 
mobile torpedo provided with a storage battery 
and electric motor would then be distinguished 
from an electrically propelled torpedo, connected 
by means of cables with a driving dynamo 
located outside the torpedo on a ship, or on the 
shore. 

Torpedo Boat.— (See Boat, Torpedo) 

Torpedo Cable. — (See Cable, Torpedo) 

Torpedo, Drifting A torpedo sus- 
pended from a float, and connected by means 
of rope with similar torpedoes, allowed to 
drift with the current, so as to catch against 
a vessel. 

Torpedo, Electric A name some- 
times given to the electric ray. (See Ray, 
Electric) 

Torpedo, Electric An electrically 

operated torpedo. 

This latter usage of the term is the commoner. 

Torpedo, Halpine-Savage A special 

form of torpedo, in which electricity is both 
the propelling and directing power, and in 
which the electric source furnishing the pro- 
pelling current is contained within the 
torpedo. 

In the Halpine-Savage torpedo, the propelling 
power is obtained from a storage battery placed 
within the torpedo. 

Torpedo, Lay A moving torpedo, 

in which the moving power is carbonic acid 
gas, or compressed air, or other similar power 
not electric, and the guiding power is electric. 

The Lay torpedo has the form of a cylindrical 
boat furnished with conical ends. The explosive is 
placed in the fore part of the torpedo. Flags are 



Tor. 



528 



[Ton. 



attached to the torpedo, showing the operator the 
exact course taken by it. 

The torpedo is started, stopped and steered by 
means of electric currents sent to the torpedo 
through an insulated cable connected with the 
torpedo. 

Torpedo Nets.— (See Nets, Torpedo?) 

Torpedo, Outrigger A pole or 

spar torpedo. 

The torpedo is placed in a metallic case and 
supported on the end of a spar or outrigger. The 
spar is depressed until the torpedo is sunk below 
the water line. The torpedo is fired when its end 
comes in contact with the side of the enemy's 
vessel. 

Torpedo, Sims-Edison A special 

form of torpedo in which electricity is both 
the propelling and the directing power, but the 
electric source is situated outside of the 
torpedo. 

The torpedo is propelled by means of an electric 
motor placed in the torpedo, and driven by means 
of an electric current transmitted through a cable 
connected with the sending station. 

Torpedo, Spar A torpedo, attached 

to the end of a spar, and designed to be 
exploded by percussion against the side of an 
enemy's vessel, when thrust against the side 
below the water-line. 

The spar torpedo is but little used, having 
been replaced by more efficient forms. 

— A term some- 



Torpedo, Stationary 



times employed instead of a submarine 
mine. (See Mine, Subitiarine?) 

A stationary torpedo is so named in order to 
distinguish it from a torpedo which is moved 
through the water by any means. (See Torpedo, 
Towing.) 

Torpedo, Towing — A torpedo ar- 
ranged to be towed on the surface after a ves- 
sel and explode when it strikes the side of 
an enemy's vessel. 

The torpedo is shaped so that it maintains dur- 
ing its motion a certain distance from the sides of 
the towing boat or vessel. 

Torque. — That moment of the force ap- 
plied to a dynamo or other machine which 
turns it or causes its rotation. 



The mechanical rotary or turning force 
which acts on. the armature of a dynamo- 
electric machine or motor and causes it to 
rotate. 

In the case of the armature of a dynamo- 
electric machine the torque is equal to the radius 
of the armature, multiplied by the pull at the 
circumference, or the radius of its pulley multiplied 
by the pull at the circumference of the pulley. 

A torque is exerted on the shaft of a motor from 
the electro-magnetic action, or pull at the. 
periphery of the armature. 

The torque is usually measured in pounds of 
pull at the end of a radius or arm I foot in 
length. 

Torricellian Vacuum. — (See Vacuum* 
Torricellian?) 

Torsion Balance, Coulomb's (See 

Balance, Coulomb's Torsion?) 

Torsion Galvanometer.— (See Galvanom- 
eter, Torsion?) 

Total Disconnection. — (See Disconnec- 
tion, Total?) 

Total Earth.— (See Earth, Total?) 

Total Magnetic Induction. — (See Induc- 
tion, Total Magnetic?) 

Touch, Double A method of mag- 
netization in which two closely approximated 
magnet poles are simultaneously drawn from 
one end of the bar to be magnetized to the 
other and back again, and this repeated a 
number of times. 

Touch, Separate A method of 

magnetization in which two magnetizing poles 
are simultaneously applied to the bar to be 
magnetized and drawn over it in opposite di- 
rections. (See Magnetization by Touch?) 

Touch, Single A method of mag- 
netization in which a single magnetizing bar 
is drawn from one end to the other of the bar 
to be magnetized, and returned through the 
air for the next stroke. (See Magnetization* 
Methods of?) 

Tourmaline. — A mineral consisting of 
natural silicates and borates of alumina, lime, 
iron, etc., possessing pyro-electric properties. 
(See Electricity, Tyro.) 



Tow.] 



529 



[Tra. 



Tower, Conning A shot-proof 

tower from which the commander of a turret 
ship directs the movements of a vessel during 
action. 

Tower, Electric —A high tower pro- 
vided for the support of a number of electric 
arc lamps, employed in systems of general 
illumination. 

Tower System of Electric Lighting. — 
The lighting of extended areas by means of 
arc lights placed on the tops of tall towers. 

The tower system of electric illumination is only 
applicable to wide open spaces, since otherwise 
objectionable shadows are apt to be formed. 

Towing Torpedo. — (See Torpedo, Tow- 
ing^ 

Traction, Magnetic The force with 

which a magnet holds on to or retains its 
armature, when once attached thereto. 

Magnetic traction is to be distinguished from 
magnetic attraction, or the ability of a magnet 
pole to draw an armature or other magnets to- 
wards it from a distance. 

Train Wire. — (See Wire, Tram.) 

Tramway, Electric A railway over 

which cars are driven by means of elec- 
tricity. 

An electric railroad. 

The term tramway is sometimes applied to 
roads in cities, as distinguished from inter-urban 
roads. 

Transformer. — An inverted Ruhmkorff 
induction coil employed in systems of dis- 
tribution by means of alternating currents. 

A transformer is sometimes called a converter. 
The word transformer is, however, the one most 
employed. 

A transformer consists essentially of an induc- 
tion coil, Fig. 556, in which the primary wire is 
long and thin, and consequently has many turns, 
as compared with the secondary wire, S, S, which 
is short, thick, and has few turns. 

To prevent heating and loss of energy in con- 
version, the core of the transformer is thoroughly 
laminated; to lower the resistance of its mag- 
netic circuit, the transformer is usually iron-clad. 

In a system of electrical distribution by means 
of transformers, alternating currents, of small 
current strength and comparatively considerable 



difference of potential, are sent over a line from a 
distant station, and passing into the primary wire 
of a number of converters, generally connected 
to the line in multiple arc, produce, by induction 




Fig. 556. Transformer. 

currents of comparatively great strength and 
small difference of potential in the secondary 
wires. 

Various electro -receptive devices are connected 
in multiple arc to circuits connected with the sec- 
ondary wires. 

This method of distribution greatly reduces the 
cost of the main conducting wires or leads in all 
cases where the distance is considerable, since 
considerable energy may be conveniently sent 
over a comparatively thin wire, with but a trifling 
loss, if the difference of potential is sufficiently 
great. 

The general arrangement of the converters on 
the main line, and the connection of the second- 
ary circuits with the electro-receptive devices in 









J 
















A 


fj — 


a"*j]C 




[' 


6 


t 




',* 


V 


< *W ci 






=1 


%i. — 










t 




O 

O 


rf' 


I? 1 






' 


p* 






■O 






O 






O 








ty 




§ 




bJ 








-, ) 


(r- 




J 



Fig. SJ7- Transformer Circuits. 

such a system, are shown in Fig. 557. The trans- 
formers are supported on the line poles, as more 



TraJ 



530 



[Tra. 



clearly shown in Fig. 558, in which the terminals 
of the primary and secondary of the converter 
are readily seen. 

When the converter is properly constructed, 
the loss of conversion at full load is but small; 
that is to say, the number of watts in the secon- 
dary is very nearly equal to the number in the 
primary. A current of 10 amperes, at 2,000 
volts, when passed into a converter the number 
of whose turns in the primary is twenty times the 
number in its secondary, will produce in its sec- 
ondary a current whose strength is about twenty 
times as great, that is, nearly 200 amperes, but 
whose voltage is only about one-twentieth, or, 
100; the watts in the two cases are nearly the 
same, or theoretically 20,000 watts. 

The ratio between the windings of the primary 
and the secondary circuits is called the co-effi- 
cient of transformation. 

In general, the shorter the wire on the second- 
ary, and the smaller its number of turns, the 
greater is the reduction in the difference of po- 
tential, and the greater the current produced. 
The reduction is nearly proportionate to the ratio 
of the number of windings oi the two coils. 



Transformer, Constant-Current 




Fig. 558. Transformer Attached to Poles. 

Transformer, Closed Iron Circuit 

— A transformer the core of which forms a 
complete magnetic circuit. 

These transformers are sometimes called iron- 
-clad transformers. 

Transformer, Commuting A term 

sometimes applied to a variety of motor gen- 
erator in which neither the armature nor the 
field magnets revolve, the variations in the 
polarity of the magnetic circuit being obtained 
•by means of special commutators. 



transformer in which a current of a constant 
potential in the primary is converted into a 
current of constant strength in the secondary, 
despite changes in the load on the secondary. 

Transformer, Core A transformer 

in which the primary and secondary wires 
are wrapped around the outside of a core 
consisting of a bundle of soft iron wires or 
plates. 

A Ruhmkorff coil is a core transformer. 

Transformer, Efficiency of — The 

ratio between the whole energy supplied in 
any given time to the primary circuit of a 
transformer and that which appears in the 
form of electric current in the secondary 
circuit. 

The energy applied to the primary circuit of a 
transformer is dissipated: 

(1.) By eddy currents in the core of the trans- 
former. (See Currents, Eddy.) 

(2.) By hysteresis, or magnetic friction. (See 
Hysteresis. ) 

(3.) By heating of the primary circuit. 

(4.) By heating of the secondary circuit. 

When a transformer is overloaded, its efficiency 
decreases. There is a certain range of second- 
ary resistance and current, within which a trans- 
former is most advantageously operated. 

Transformer Guard. — (See Guard, Trans- 
former, Lightning?) 

Transformer, Hedgehog" A name 

applied to a particular form of open-iron cir- 
cuit transformer. (See Transformer.) 

The advantages claimed for the hedgehog trans- 
former are that it can be made to give a higher 
all-day efficiency, since it insures a smaller loss 
from hysteresis in the iron. The efficiency for 
very small loads, or for no loads is greater than in 
the closed-circuit transformer. 

Transformer, Leakage Current of 

A term sometimes used for the current which 
escapes from the primary through the dielec~ 
trie of a transformer to the secondary circuit. 

The term is a bad one, since the true leakage 
current would be the current which represents 
the leakage between the primary or secondary 
circuit and the ground. 



Tra.] 



531 



[Tra. 



Transformer Lightning Arrester. — (See 
Arrester, Lightning, Transformer.) 

Transformer, Multiple Any form 

of transformer which is connected in multiple 
to the primary circuit. 

A multiple or parallel transformer is self-regu- 
lating under variable loads, provided the electro- 
motive force in the primary is maintained con- 
stant. 

Transformer, Oil A transformer 

which is immersed in oil in order to insure a 
high insulation. 

Transformer, Open-Iron Circuit 

A transformer the iron of which does not form 
.a complete magnetic circuit, but is formed 
instead partly of iron and partly of air. 

Transformer, Pilot A small trans- 
former, placed at any desired portions of a 
line in order to determine the drop of poten- 
tial. 

The pilot transformer is used in connection with 
a lamp or other suitable indicating device. Its use 
is similar to the use of the pilot incandescent lamp. 

Transformer, Rotary-Current A 

transformer operated by means of a rotary 
current. (See Current, Rotating?) 

The rotary current transformer for a rotary 
current of three separate alternating currents com- 
bined, transforms all three currents together. 
There are three cores, connected at one set of 
ends and at the other to the circumference of an 
iron . ring. Each core contains a primary and 
secondary wire. 

Transformer, Rotary-Phase A ro- 
tary current transformer. (See Transfor- 
mer, Rotary-Current .) 

Transformer, Series Transformers 

which are connected in series with the pri- 
mary circuit. 

A series transformer is not as readily made self- 
regulating under variations in the load as a mul- 
tiple transformer. If, however, its core is not 
saturated, and the electromotive force of its 
secondary is small, it can be made fairly self- regu- 
lating. Series transformers are used in the 
Jablochkoff system for feeding arc lamps in the 
shape of Jablochkoff candles. 

Transformer, Shell A transformer 



in which the primary and secondary coils are 
laid on each other, and the iron core is then 
wound through and over them so as to en- 
close all the copper of the primary and 
secondary circuits within the iron. 

The iron shell surrounding the copper may 
consist of the thin plates of iron, built up so as to 
leave a rectangular space for the introduction of 
the primary and secondary, 

Transformer, Step-Down A trans- 
former in which a small current of compara- 
tively great difference of potential is con- 
verted into a large current of comparatively 
small difference of potential. 

An inverted Ruhmkorff induction coil. 

Transformer, Step-Up —A trans- 
former in which a large current of compara- 
tively small difference of potential is con- 
verted into a small current of comparatively 
great difference of potential. 

The term step-up transformer is used in contra- 
distinction to the step -down transformer. 

The old form of Ruhmkorff coil is an example 
of a step-up transformer. 

Transformer, Testing — A trans- 
former employed in any system of distribu- 
tion for the purposes of testing for grounds, 
condition of line, drop of potential, etc. 

Transformer, Welding* A trans- 
former suitable for changing a small electric 
current of comparatively high difference of 
potential, into the heavy currents of low 
difference of potential required for welding 
purposes. 

Welding transformers have in general a very 
low resistance in their secondary coils, and almost 
invariably consist of a single turn or at the most 
of a few turns of very stout wire. 

Transforming Currents.— (See Current, 
Transforming a.) 

Transforming Down. — Transforming by 
means of a step-down transformer. (See 
Transformer, Step-Down.) 

Transforming Station. — (See Station, 
Tra nsforin ing.) 

Transforming Up. — Transforming by 
means of a step-up transformer. (See 
Transformer, Step- Up.) 



Tra.] 



532 



[Tra. 



Transient Currents. — (See Currents^ 
Transient?) 

Transit, Magnetic Variation An 

apparatus for measuring the declination or 
variation of the magnetic needle at any place. 
The variation transit generally consists of an 
altitude and azimuth instrument, the telescope of 
which is so arranged as to be readily converted 
into a microscope. 

Transition Eesistance. — (See Resistance, 
Transition?) 

Translater, Double-Current — A 

telegraphic translater or repeater designed to 
operate on double current transmission. 

Translater, Single-Current — 



-The simul- 



— A tele- 
graphic translater or repeater designed to 
operate a single-current transmission. 

Translater, Telegraphic — A term 

sometimes applied to a telegraphic repeater. 
(See Repeaters, Telegraphic?) 

Translating Device. — (See Device, Trans- 
lating?) 

Translating Devices, Multiple-Arc-Con- 
nected (See Devices, Translating, 

Multiple- Arc- Connected?) 

Translating Devices, Multiple-Con- 
nected — (See Devices, Translating, 

Multiple- Connected) 

Translating Devices, Multiple-Series- 
Connected (See Devices, Translat- 
ing, Multiple- Series- Connected?) 

Translating Devices, Series-Connected 

(See Devices, Translating, Series- 
Connected?) 

Translating Devices, Series-Multiple- 
Connected (See Devices, Translat- 
ing, Series-Multiple- Connected?) 

Translucent-Disc Photometer. — (See 

Photometer, Translucent-Disc?) 

Transmission, Double The simul- 
taneous sending of two messages over a sin- 
gle wire in opposite directions. (See Teleg- 
raphy, Duplex, Bridge Method of.) 



Transmission, Multiple — 

taneous sending of more than two messages 
over a single line or conductor. 

Transmission of Energy. — (See Energy, 
Electric, Transmission of?) 

Transmitter, Carbon, for Telephones 

. — A telephone transmitter consisting of 

a button of compressible carbon. 

The sound waves impart to-and-fro movements 
to the transmitting diaphragm, and this to the 
carbon button, thus varying its resistance by pres- 
sure. This button is placed in circuit with the 
battery and induction coil. (See Telephone.) 

Transmitter, Double-Current 



—The 

transmitting instrument employed in systems 
of telegraphy, by means of which the direc- 
tion of the currents on the line is alternately 
changed, according to whether the key rests 
on its front or on its back stop. 

Double-current transmitters are used in con- 
nection with instruments, such as polarized re- 
lays, which respond to change in the direction of 
the current, rather than to changes in its in- 
tensity. 

Transmitter, Electric A name 

applied to various electric apparatus employed 
in telegraphy or telephony to transmit or send 
the electric impulses over a line wire or con- 
ductor. 

The sending instrument as distinguished 
from the receiving instrument. 

In most telegraphic systems, the transmitting 
instrument consists of various forms of keys for in- 
terrupting or varying the current. In the tele- 
phone the transmitter consists of a diaphragm 
operated by the voice of the speaker. (See Tele- 
phone.) 

Transmitter, Water-Jet Telephone 

— A telephone transmitter consisting of a jet 
of water issuing vertically downwards from a 
small orifice. 

The jet forms a part of the circuit of the re- 
ceiving telephone. In order to reduce its resist- 
ance, the water is rendered acid by the addition 
of sulphuric acid, and a battery of high electro- 
motive force is employed. Since the jet has a 
high resistance, a battery of high resistance can 
be used without inconvenience. 



Tra.] 



533 



[Tro. 



Transposing. — In a system of telephonic 
communication a device for avoiding the bad 
effects of induction by ' alternately crossing 
equal lengths of consecutive sections of the 
line. (See Connection, Telephonic Cross.) 

Transverse Electromotive Force. — (See 
Force, Electromotive, Transverse?) 

Treatment, Hydro-Carbon, of Carbons 

Exposing carbons, while electrically 

heated to incandescence, to the action of a 
carbonizing gas, vapor or liquid, for the pur- 
pose of rendering them more uniformly elec- 
trically conducting throughout. (See Car- 
bons, Flashing Process for?) 

Tree, Parallel, Circuit (See Cir- 
cuit, Parallel- Tree?) 

Trembling Bell.— (See Bell, Tre?nbling?) 

Trigonometrical. — Of or pertaining to 
trigonometry. (See Trigonometry?) 

Trigonometrical Function. — (See Func- 
tion, Trigonometrical?) 

Trigonometrically. — In a trigonometrical 
manner. 

Trigonometry. — That branch of mathe- 
matical science which treats of the methods 
of determining the values of the angles and 
sides of a triangle. 

There are in every triangle three sides and 
three angles. If any three of these parts are 
given, except the three angles, the values of the 
remaining parts can be determined by means of 




F*g- 559' Dynamo Brush Trimmer. 

trigonometry, by what is called the solution of 
the triangle. [See Function, Trigonometrical.) 



Trimmer. — An employee of an electric 
light company who renews the carbons in 
arc lamps. 

Trimmer, Dynamo Brush A de- 
vice for insuring rapid and accurate trimming 
of dynamo brushes. 

The brush trimmer consists of a knife, placed 
as shown in Fig. 559 on a rigid support. The 
brushes are placed under a clamp, and against a 
straight edge, so that a single cut with the knife 
blade insures a clean and true cut. 

Trimming. — A term sometimes applied to 
the act of placing the carbons in an electric 
arc lamp. 

The phrase, carboning a lamp, would appear 
to be preferable to trimming a lamp. 

Triple-Carbon Arc Lamp. — (See Lamp, 
Arc, Triple-Carbon?) 

Tripod Roof Support. — (See Support, 
Tripod Roof?) 

Trolley. — A rolling contact wheel that 
moves over the overhead lines provided for a 
line of electric railway cars, and carries off 
the current required to drive the motor car. 

Trolley Crossing. — A device placed at the 
crossing of two trolley wires, by which the 
trolley wheel running on one wire may cross 
the other. 

Such a device can also be made to hold the two 
wires together. 

Trolley Crossing, Insulated A de- 
vice used at the crossing of two trolley wires, 
which insulates the wires from each other, 
but which permits the trolley wheel of one 
line to cross the other trolley line. 

Trolley Cross-Over.— (See Cross-Over, 
Trolley?) 

Trolley, Double The traveling con- 
ductors, which move over the lines of wire in 
any system of electric railways that employs 
two overhead conductors. 

In one form of double trolley a bar of wood 
carries two hangers, separated from each other, 
and furnished with diverging feet, with clips that 
embrace the two conducting wires. These wires 
serve also as the track for the two-wheeled trolley. 
The trolley consists of two plates connected to and 
insulated from each other under the conductors, 



Tro.] 



534 



[Tub. 



and carrying flanged wheels, extending in over 
the conductors. 

Swinging from the axles of the poles are arms, 
which form a bail-like draft loop, with insulated 
material between their lower ends, and furnish 
means for connection with the car motor. In 
order to remove this trolley from the conducting 
wires, these arms are pressed together at points 
between two points of hangers, which allows 
them to pass between the inner ends of the wheel 
axles. 

The trolley cannot be removed from the wires 
except at the end of the track, and it is therefore 
found in practice to be particularly useful in 
mines, where, from the nature of the galleries, the 
trolley wheel is very apt to become detached from 
the trolley wires. 

Trolley, Drop The trolley wheel 

and rod for an electric car which drops away 
from the wire on slipping from the wire, and 
is reset upwards through proper elastic press- 
ure. 

Trolley Fork.— (See Fork, -Trolley) 
Trolley Frog. — (See Frog, Trolley) 

Trolley Frog 1 , Standard (See Frog, 

Trolley, Standard) 

Trolley Hanger.— (See Hanger, Trolley) 

Trolley Pole.— (See Pole, Trolley) 

Trolley Section. — (See Section, Trolley) 

Trolley, Single A traveling con- 
ductor or wheel which moves over a single 
conductor in a system of electric railways, 
and takes off the current for driving the elec- 
tric motor, in connection with an earth or 
grounded return conductor. 

Trolley Wheel. — (See Wheel, Trolley) 

Trolley, Wire (See Wire, Trolley) 

True Contact Force. — (See Force, True 
Contact) 

True Resistance. — (See Resistance, 
True) 

Trumpet, Electric — An electro- 
magnetic buzzer, the sound of which is 
strengthened by means of a resonator in the 
shape of a trumpet. (See Buzzer, Electric. 
Resonator, Electric) 



The electric trumpet is used to replace electric 
bells. It gives a louder and more penetrating 
sound than the electric bell. 

Trunking Switch Board. — (See Board, 
Switch, Trunki?ig) 

Tube, Crookes' A tube containing 

a high vacuum and adapted for showing any 
of the phenomena of the ultra-gaseous state 
of matter. (See Matter, Radiant, or Ultra- 
Gaseous) 

Tube, Insulating A tube of insu- 
lating material provided for covering a splice 
in an insulated conductor. 



Tube, Mercury 



-Vacuous glass tubes 



in which a flash of light is produced by the 
fall of a small quantity of mercury placed in- 
side it. 

The light is caused by the electricity produced 
by the friction of the mercury in falling against 
the sides of a spiral glass tube placed inside the 
vacuous tube. 

Tube, Plucker A modification of a 

Geissler tube adapted for the study of the 
stratification of the light, and the peculiar- 
ities of the space adjoining the negative elec- 
trode. (See Tubes, Geissler) 



-A high vacuum tube, 



Tube, Spark — 

across which, when the vacuum is sufficiently 
high, the spark from an induction coil will not 
pass. 

A spark tube, connected with incandescent 
lamps while undergoing exhaustion, acts as a 
simple gauge to determine the degree of ex- 
haustion. When an induction coil discharge 
ceases either to pass, or to pass freely, the vacuum 
is considered as sufficient, according to circum- 
stances. 

Tube, Stratification An exhausted 

glass tube, the residual atmosphere of which 
displays alternate dark and light striae, or 
stratifications, on the passage through it of 
an induction coil discharge. (See Discharge, 
Luminous Effects of) 

Tubes* Geissler Vacuum tubes of 

glass containing various gases, liquids or 
solids, provided with platinum electrodes, 
passed through and fused into the glass, de- 
signed to show the various luminous effects 



Tub.] 



535 



[Twi. 



of electric discharges through gases at com- 
paratively low pressures. 

Geissler tubes are made of a great variety of 
shapes, and often include tubes, spirals, spheres, 
etc., within other tubes. These enclosed tubes 
are made either of ordinary glass, or of uranium 
glass in order to obtain the effects of fluorescence. 

The vacuum in Geissler tubes is by no means 
what might be called a high vacuum. Indeed, if 
the exhaustion of the tube be pushed too far, 
much of the brilliancy of the luminous effects is 
lost. 

Some of the many forms of Geissler tubes are 
shown in Fig. 560. 




Fig. 560. Geissler Tubes. 

Tubes of Force.— (See Force, Tubes of.) 
Tubes of Induction. — (See Induction, 
Tubes of.) 

Tubes, Vacuum Glass tubes, from 

which the air has been partially exhausted and 
through which electric discharges are passed 
for the production of luminous effects. (See 
Tubes, Geissler.) 
Tubular Braid.— (See Braid, Tubular.} 
Tumbling- Box. — (See Box, Tumbling.) 
Tuning--Fork or Heed Interrupter. — (See 
Interrupter, Timing-Fork. Interrupter, 
Heed) 

Turn, Ampere A single turn or 

winding in a coil of wire through which one 
ampere passes. 

An ampere-turn is sometimes called an ampere- 
winding. Magneto-motive force in a magnetic 
circuit is proportioned to the number of ampere- 
turns linked with it. The practical unit of mag- 
neto-motive force is X ampere turn = .0796 

ampere turn. Therefore the magneto-motive 



force, m. m. f., is found by multiplying the am- 
pere turns by 4 it or 12.57. 

The number of amperes multiplied by the 
number of windings or turns of wire in a coil give 
the total number of ampere-turns in the coil. 

In a coil of fixed dimensions the magnetizing 
force developed by a given number of ampere-turns 
remains the same as long as the product of the 
amperes and the current remains the same. That 
is to say, the same amount of magnetizing force 
can be obtained by the use of many windings and 
a small current, as in shunt dynamos, or by a few 
turns and a proportionally large current, as in 
series dynamos. (See Machine, Dynamo-Elec- 
tric.) 

Turns, Ampere, Primary — The 

ampere-turns of the primary of an induction 
coil. 

Turns, Ampere, Secondary The 

ampere-turns of the secondary of an induc- 
tion coi J . 

Turns, Dead The number of revo- 
lutions a self-exciting dynamo makes before 
it excites itself. 

Turns, Dead, of Armature Wire 

Those turns of the wire on the armature of a 
dynamo-electric machine which produce no 
useful electromotive force or resultant current, 
on the movement of the armature through the 
magnetic field of the machine. 

The wire on the inside of a Gramme or ring 
armature is dead wire, but not dead turns. 

Turns, Series, of Dynamo-Electric Ma- 
chines The ampere-turns in the 

series circuit of a compound-wound dynamo- 
electric machine. (See Machine, Dynamo- 
Electric, Compound- Wound) 

Turns, Shunt, of Dynamo-Electric Ma- 
chine The ampere-turns in the shunt 

circuit of a compound-wound dynamo-elec- 
tric machine. (See Machine, Dynamo-Elec- 
tric, Compound- Wound) 

Turn-Table, Electric A table, suit- 
able for show windows, revolved around a 
vertical axis by means of an electric motor. 

Twig". — A sub-branch. (See Branch, 
Sub.) 

Twin Wire.— (See Wire, Twin.) 



Twi. 



536 



[Uui. 



Twist in Leads. — (See Leads, Armature, 
Twist in) 

Twisted Bunched Cable.— (See Cable, 
Bunched, Twisted) 

Twisted-Pair Cable.— (See Cable, Twisted- 
Pair) 

Twisting Force. — (See Force, Twisting) 

Two-Fluid Voltaic Cell.— (See Cell, Vol- 
taic, Two-Fluid) 

Two-Point Switch. — (See Switch, Two- 
Point) 

Two, Three, Four, etc., Conductor Cable 

— (See Cable, Two, Three, Four, etc., 

Conductor) 

Two-Way Splice Box. — (See Box, Splice, 
Two- Way) 



Two-Way Switch.— (See Switch, Two. 
Way) 

Type-Printing Telegraph. — (See Teleg- 
raphy, Printing) 



Typewriter, Electric 



-A typewrit- 



ing machine, in which the keys are intended 
to make the contacts only of circuits of 
electro-magnets, by the attraction of the arma- 
tures of which the movements of the type 
levers required for the work of printing are 
effected. 

Electric typewriters secure a uniformity of im- 
pression that is impossible to obtain with hand 
worked machines. They also greatly lessen the 
mechanical labor of writing, (See Dynamograph.) 



U. — A contraction sometimes used for unit. 

Ultra-Gaseous Matter. — (See Matter, 
Radiant, or Ultra-Gaseous) 

Underground Cable.— (See Cable, Under- 
ground) 

Underground Conductor. — (See Con- 
ductor, Underground) 

Undulating Currents. — (See Current, 
Undulating) 

Undulatory Currents. — (See Currents, 
Undulatory) 

Undulatory Discharge. — (See Discharge, 
Undulatory) 

Ungilding Bath.— (See Bath, Ungild- 

Unidirectional Discharge. — (See Dis- 
charge, Unidirectional) 

Unidirectional Leak. — (See Leak, Uni- 
directional) 

Uniform Density of Field.— (See Field, 
Uniform Density of) 

Uniform Magnetic Field. — (See Field, 
Magnetic, Uniform) 

Uniform Magnetic Filament. — (See Fila- 
ment, Unifor?n Magnetic) 



Uniform Potential. — (See Potential, 
Uniform) 

Uniformly Distributed Current. — (See 
Current, Uniformly Distributed.) 

Unipolar Armature. — (See Armature, 
Unipolar) 

Unipolar-Electric Bath. — (See Bath, Uni- 
pola r-Electric) 

Unipolar Induction. — (See Induction, 
Unipolar) 

Unit Angle. — (See Angle, Unit. Velocity, 
Angular) 

Unit Angular Velocity.— (See Velocity, 
Angular) 

Unit, B. A. A term formerly ap- 
plied to the British Association unit of re- 
sistance, or ohm. (See Ohm) 

Unit-Difference of Potential or Electro- 
motive Force —(See Potential, Unit 

Difference of) 

Unit, Magnetic, A A term some- 
times used for a line of magnetic force, or 
the amount of magnetism induced in an area 
of one square centimetre at the centre of a 
coil having a diameter of 10 centimetres and 
carrying a current of 7.9578 amperes. 

Unit, Natural, of Electricity -(See 

Electricity, Natural Unit of) 



Uni.] 

Unit of Acceleration. — (See Acceleration, 
Unit of) 

Unit of Activity — (See Activity, Unit of) 

Unit of Current, Absolute (See 

Current, Absolute Unit of) 

Unit of Current, Jacobi's — (See 

Current, facobi's Unit of) 

Unit of Electrical Supply.— (See Supply, 
Unit of, Electrical) 

Unit of Electromotive Force, Absolute 

— (See Force, Electromotive, Absolute 

Unit of) 

Unit of Electrostatic Capacity. — (See 
Capacity, Electrostatic, Unit of) 

Unit of Heat.— (See Heat Unit) 

Unit of Inductance. — (See Inductance, 
Unit of) 

Unit of Mass.— (See Mass, Unit of) 

Unit of Photometric Intensity.— (See 

Intensity, Photometric, Unit of) 

Unit of Power. — (See Power, Unit of) 

Unit of Pressure, New The Barad. 

(See Barad) 

Unit of Resistance.— (See Resistance, 
Unit of) 

U[nit of Resistance, Absolute (See 

Resistance, Absolute Unit of) 

Unit of Resistance, Jacobi's (See 

Resistance, Unit of, Jacobi's) 

Unit of Resistance, Matthiessen's 

(See Resistance, Unit of, Matthiessen's) 

Unit of Resistance, Yarley's (See 

Resistance, Unit of, Varley's) 

Unit of Telocity, New (See Ve- 
locity, New Unit of) 

Unit Quantity of Electricity. — (See Elec- 
tricity, Unit Qua?itity of) 

Unit-Strength of Current.— (See Cur- 
rent, Unit Strength of) 

Units, Absolute A system of units 

based on the centimetre for the unit of length, 
the gramme for the unit of mass, and the 
second for the unit of time. 



537 [Uni. 

These units are more frequently called the 
centimetre-gramme-second units. 

Units, Centimetre-Gramme-Second 

— A system of units in which the centimetre 
is adopted for the unit of length, the gramme 
for the unit of mass, and the second for unit 
of time. 

This is the same as the absolute system of 
units. 

Units, C. G. S. The centimetre- 
gramme-second units. (See Units, Funda- 
mental) 

Units, Circular Units based upon 

the value of the area of a circle whose diame- 
ter is unity. 

The advantages possessed by the circular units 
of cross-section arise from the fact that in these 
units the areas are equal to the squares of the 
diameter. No necessity exists, therefore, for mul- 
tiplying by .7854. 

Units, Circular (Cross-Sections), Table 
of 

1 circular mil = .78540 square mil. 

" " = .00064514 circular 

millimetre. 

" " = .00050669 square 

millimetre. 

1 square mil = 1.2732 circular mils. 

" " = .00082141 circular 

* millimetre. 

1 circular millimetre =1550.1 circular mils. 

" " = 1217. 4 square mils. 

" " = .78540 square milli- 

metre. 

1 square millimetre = 1973-6 circular mils. 

" " =1.2732 circular mil- 

limetres. 
If d, is the diameter of a circle, the area in 
other units is: 
If d, is in mils, the area in 

square millimetres . .... = d 2 X .00050669. 
d, in millimetres, area in 

square mils =d 8 X 1217.4. 

d, in centimetres, area in 

square inches = d 2 X 12174. 

d, in inches, area in square 

centimetres = d 2 X 5.0669. 

—{Hering.) 



Uni.] 



538 



[Uni. 



Units, Derived Various units ob- 
tained or derived from the fundamental units 
of Length, L., Mass, M., and Time, T. 

The derived units and their dimensions are as 
follows: 

Area, L 3 . — The square centimetre. 

Volume, L 3 . — The cubic centimetre. 

Velocity, V. — Unit distance traversed in unit 
time, or 



V 



L 

r 



(i) 



Acceleration, A. — The rate of change which 
will produce a change of velocity of one centi- 
metre per second. 

A =4 



(2) 



Substituting in equation (2) the value of V, in 
equation (1), we have 
L 






(3) 



Force, F. — The dyne, or the force required to 
act on unit mass in order to impart to it unit 
velocity. 

F = MXA. (4) 

Substituting the value of A, derived from equa- 
tion (2), we have 

V 
F = M X -. 

Substituting the value of V, derived from equa- 
tion (1), we havej, 

M L __ ML 

-f = 7p X 7p = rp.j • (5) 

Work or Energy, W. — The erg, or the work 
done in overcoming unit force through unit dis- 
tance. 



W: 



r xL = |xL = | ! 



Power, P. — The unit rate of doing work. 
ML2 

T — j 



ML ^ 



T« 



(6) 



Units, Dimensions of The values 

given to the units of length, L ; mass, M, and 
time, T. (See Units, Derived?) 

Units, Electro-Magnetic A system 

of units derived from the C. G. S. units, em- 



ployed in electro-magnetic measurements. 
(See Units, Centimetre-Gramme-Second.) 

Units based on the attractions or repul- 
sions between two unit magnetic poles at 
unit distance apart. (See Units, Electro- 
static.) 

Units, Electro-Magnetic, Dimensions of 



Current Strength = Intensity of FieldxLength = 
v'ML 
T 

Quantity = Current X Time = v/M X L . 
Potential, Difference of Potential, Electromo- 
Work 



live Force 



Resistance: 



Quantity 



\/M X V 



Electromotive Force L 



Current T 

Capacity = Quantity _T^ 
Potential - L 

Units, Electrostatic Units based 

on the attractions or repulsions of two unit 
charges of electricity at unit distance apart. 

Two systems of electric units are derived from 
the C. G. S. system, viz., the electrostatic and 
electro -magnetic. These units are based respec- 
tively on the force exerted between two quanti- 
ties of electricity and between two magnet poles. 

The electrostatic units embrace the units of 
quantity, potential and capacity. No particular 
names have as yet been adopted for these units. 

Unit of Quantity. — That quantity of electricity 
which will repel an equal quantity of the same 
kind of electricity placed at a distance of one cen- 
timetre from it with the force of one dyne. 

Electrostatic potential, or power of doing elec- 
trostatic work, is measured in units of work, or 
ergs. 

Unit Difference of Potential. — Such a differ- 
ence of potential between two points as requires 
the expenditure of one erg of work to bring up 
a unit of positive electricity from one point to the 
other against the electric force. 

Unit of Capacity. — Such a capacity of conduc- 
tor as will take a charge of one unit of electricity 
when the potential is unity. 

The ratio between the inductive capacity of a 
substance and that of air, measured under pre- 



Uni.] 



539 



[Uni, 



cisely similar conditions, is called the specific in- 
ductive capacity. 

The specific inductive capacity is obtained by 
comparing the capacity of a condenser filled with 
the particular substance and the capacity of the 
same condenser when filled with air. The spe- 
cific inductive capacity of air is taken as unity. 

Units, Electrostatic, Dimensions of 



Quantity = v/Force X (Distance) 2 = ^F x L- 
M^ L* n/M X L3 



Current = Q uantit y 



1 3 



s/MxL< 



Potential = 



Resistance 



Capacity 



Time 
Work 



M* i; 






Quantity 
Potential 
Current 
Quantity 



= L" 



= L. 



Potential 
Specific Inductive Capacity = 

One Quantity 
Another Quantity = A Sim P 1 ^ Ratio or Number. 

Electromotive Intensity = 

Force _ M * L | T \ _ y/M x L 
Quantity — T 

The fractional and negative exponents used 
above are merely convenient methods of express- 
ing the extraction of roots and division respec- 
tively by the quantity represented by these expo- 
nents. 

Units, Fundamental The units of 

length, time and mass, to which all other 
quantities can be referred. 

The unit of length is now generally taken as 
the centimetre, the unit of time as the second, and 
the unit of mass as the gramme. These form a 
system of measurement known as the centimetre, 
gramme-second system, or the C. G. S. system, or 
absolute system. (See Units, Derived.) 

The dimensions of the fundamental units are 
designated thus: 

Length = L. 
Mass = M. 
Time = T. 



quantity of heat required to raise a given 
weight or quantity of a substance, generally 
water, one degree. 

The principal heat units are the English heat 
unit, the greater and smaller calorie and the 
joule. (See Calorie. Joule.) 

The following table gives the values of some of the prin- 
cipal heat units : 

1 gram, centigrade, .001 kilogram centigrade. 

1 pound Fahrenheit, 1,047.03 joules. 

772. foot-pounds. 

106.731 kilogram metres, 

" .55556 pound centigrade. 

.25200 kilogram centigrade. 
" .29084 watt-hours. 

" .0003953 metric horse-power. 

" .0003899 horse-power hours. 

1 pound centigrade, 1,884.66 joules. 

1,389.6 foot-pounds. 

192. 116 kilogram metres. 

1.800 pound Fahrenheit. 

.4536 kilogram centigrade. 
.52352 watt-hour. 
.0007115 metric horse-power 
hour. 
" .0007018 horse power hour. 

1 kilogram centigrade, 4,154.95 joules. 

3,063.5 foot-pounds. 

423.54 kilogram metres. 

3.9683 pound Fahrenheit. 
2.2046 pound centigrade. 
1. 1542 watt-hour. 
.001569 metric horse-power 

hour. 
.0015472 horse-power hour. 
— Hering. 

— Units based on 



Units, Magnetic 



Units, Heat 



Units based on the 



the force exerted between two magnet poles. 

Unit strength of a magnetic pole is such a 
magnetic strength of pole that repels another 
magnetic pole of equal strength placed at 
unit distance with unit force, or with the 
force of one dyne. 

Magnetic Potential. — Is the power of doing 
work possessed by a magnetic pole. 

Magnetic potential is measured like electro- 
static potential in units of work or in ergs. 

Magnetic Potential, Unit Difference of.— Such 
a difference of magnetic potential between two 
points that requires the expenditure of one erg of 
work to bring a magnetic pole of unit strength 
from one to the other. 

Unit Intensity of Magnetic Field. — Such an 
intensity of magnetic field as acts on a no-th or 
south-seeking pole of unit strength with the force 
of one dyne. 



Uni,] 



540 



[Upr. 



Units, Magnetic, Dimensions of 

Strength of Pole, or 1 
Quantity of Magnetism \ 

= v/ Force X (Distance)- 5 = v/M L 3 



T 



Magnetic Potential 



Work 



_ v/ M X L 
Strength of Pole t 



Force 



s/lJP 



Intensity of Field = Strength of Pole T X / L 

Units, Practical Multiples or frac- 
tions of the absolute or centimetre-gramme- 
second units. 

The practical units have been introduced be- 
cause the absolute units are either too small or 
too large for actual use. 

Electromotive Force. — The Volt = 100,000,- 
000 C. G. S. or absolute units, that is, io 8 abso- 
lute units of resistance. (See Volt.) 

Resistance. — The Ohm= 1,000,000,000 abso- 
lute units of electromotive force, or io 9 absolute 
units. (See Ohm.) 

Current. — The Ampere = ^ absolute unit of 
current. (See Ampere.) 



quantity, of the electro-magnetic system. 
Coulomb.) 

Capacity. — The Farad = 

lute unit of capacity, or io 1 
(See Farad. Henry. Watt. 

Units, Proposed New — 



(See 



abso- 



1,000,000,000 
units of capacity. 
Joule.) 

The follow- 
ing units and terms have recently been pro- 
posed by Oliver Heaviside. 

Some of these have been generally adopted. 

Conductance. — Capacity for conducting elec- 
tricity. 

Numerically, the ratio, in absolute measure, ot 
the current strength to the total electromotive 
force in a circuit of uniform flow. A quantity 
•with the nature of a slowness or reciprocal to a 
velocity. The practical unit is called the mho. 

Conductivity . — Conductance per unit volume. 

Elastance. — Capaciry of a dielectric for oppos- 
ing electric charge or displacement. 

' ' Numerically, the ratio, in absolute measure, 
of the difference of p tential in an electrostatic cir- 
cuit to the total charge or displacement therein 
produced. The reciprocal of permittance and a 
quantity of the inverse nature of a length." 

" Elastivity. — Elastance per unit volume of di- 
electric." 

Impedance. — Capacity for opposing the variable 
flow of electricitv- 



" Numerically,' in the absolute measure, the 
ratio of the total electromotive force to the cur- 
rent strength at any instant in a circuit of a vari- 
able flow. A quantity with the nature of a 
velocity and in any circuit always greater than 
the resistance." 

"■Inductance. — Capacity for magnetic induc- 
tion." 

"Numerically, in absolute measure, the num- 
ber of unit lines of magnetic force linked with a 
circuit traversed by the unit current strength. 
Sometimes alluded to as the co-efficient of self-in- 
duction. A quantity of the nature of a length." 

" Inductivity. — Specific capacity for magnetic 
induction. 

' ' The numerical ratio of the induction in a 
medium to the induction producing it." 

Permittance. — Electrostatic capacity. Capa- 
city of a dielectric for assisting charge or displace- 
ment. 

"Numerically, the ratio, in absolute measure, 
of the total charge or displacement in the electro- 
static circuit, to the difference of potential pro- 
ducing it, A quantity with the nature of a 
length." 

" Permittivity . — The numerical ratio of the 
permittance of a dielectric to that of air. 

"Also known as specific inductive capacity." 

" Reluctance. — Capacity for opposing mag- 
netic induction. 

"Numerically, the ratio, in absolute measure, 
of the magneto-motive force in a magnetic cir- 
cuit to the total induction therein produced. A 
quantity with the nature of the reciprocal of a 
length. Sometimes described as magnetic resist- 
ance." 

Reluctancy or Reluctivity . — Reluctance per unit 
volume. 

"Sometimes described as specific magnetic re- 
sistance. A numeric, the reciprocal of induc- 
tivity.'' 

"Resistance. — Capacity for opposing the 
steady flow of electricity. 

"Numerically, in absolute measure, the ratio 
of the total electromotive force to the current 
strength in a circuit of uniform flow. A quantity 
with the nature of a velocity. The practical unit 
is called the ohm." 

"Resistivity. — Resistance per unit volume; 
sometimes alluded to as specific resistance." 

Universal Discharger. — (See Discharger, 
Universal.) 

Upright Galvanometer.— (See Galva- 
nometer, Upright^ 



Tac. 



541 



[Tar. 



T. — A contraction sometimes used for volt. 

T. — A contraction sometimes used for ve- 
locity. 

V. — A contraction sometimes used for vol- 
ume. 

V. A. — A contraction sometimes used for 
voltaic alternative. (See Alternatives, Vol- 
laic.) 

Vacuum, Absolute A space from 

which all traces of residual gas have been 
removed. 

A term sometimes loosely applied to a par- 
tial vacuum. 

It is doubtful whether an absolute vacuum is 
attainable by any physical means. 

Vacuum, High —A space from which 

nearly all traces of air or residual gas have 
t>een removed. 

Such a vacuum that the length of the 
mean free path of the molecules of the residual 
atmosphere is equal to or exceeds the di- 
mensions of the containing vessel. (See 
Layer, Crookes.) 

Vacuum, Low Such a vacuum that 

the mean free path of the molecules of the 
residual gas is small as compared with the 
dimensions of the containing vessel. (See 
Tubes, Geissler.) 

In a high vacuum groups of molecules can 
move across the containing vessel without meet- 
ing other groups of molecules. In a low vacuum 
such a group of molecules would be broken up by 
collision against other groups before reaching 
the other side of the vessel. 

Yaemvm. Partial — A name some- 
times applied to a low vacuum. (See Vac- 
tium, Law.) 

Vacuum. Torricellian The vacuum 

which exists above the surface of the mercury 
in a barometer tube or other vessel over thirty 
inches in vertical height 

The Torricellian vacuum is high only when the 
mercury has been carefully boiled and the tube 
or other vessel vigorously heated, so as to thor- 



oughly drive out the moisture and adherent film 
of air. 

Yacmmi Tubes. — (See Tubes, Vacuum) 
Taleucy. — The worth or value of a chem- 
ical atom as regards its power of displacing 
other atoms in chemical compounds. r-re 
Atomicity) 

The worth or valency of an atom of oxygen is 
twice as great as that of hydrogen, since one 
atom of oxygen is able to replace two hydrogen 
atoms in chemical combinations. 

Yalve. Electric — An electrically 

controlled or operated valve. 

In systems of electro-pneumatic signals, gaseous 
or liquid pressure controlled by electrically oper- 
ated valves is employed to move signals, ring 
bells, control water and air valves, or to perform 
other similar work. 

Vapor Globe of Incandescent Lamp. — 

(See Globe, Vapor, of Incandescent Lamp.) 

Variable Inductance. — (See Inductance, 
Variable.) 

Variable Period of Electric Current. — 
(See Current, Variable Period oj ".) 

Variable Resistance. — (See Resistance, 
Variable.) 

Variable Resistance. Automatic 

(See Resistance, Variable, Automatic) 

Variable Resistance. Non-Automatic 

— (See Resistance, Variable, ^'on-Auto- 
matic.) 

Variable State of Charge of Telegraph 
Line. — (See State, Variable, of Charge of 
Telegraph Line) 

Variation. Angle of The angle 

which measures the deviation of the magnetic 
needle to the east or west of the true geo- 
graphic north. 

The angle of declination of the magnetic 
needle. (See Declination, Angle of.) 

Variation. Annual An approxi- 
mately regular variation in the magnetic 



Tar.] 



542 



[Tel.. 



needle which occurs at different seasons of 
the year. 

Variation Chart or Map. — (See Map or 
Chart, Isogonic.) 



Variation, Cyclical Magnetic- 



-Secu- 



lar magnetic variations occurring during 
great cycles of time. (See Variation, 
Secular, Variation, Magnetic.) 

Variation, Diurnal An approxi- 
mately regular variation of the magnetic 
needle, which occurs at different hours of the 
day. (See Declination.) 



Variation, Irregular 



-A variation 



of the magnetic needle which occurs at ir- 
regular intervals. (See Declination.) 

Variation, Magnetic Variations in 

the value of the magnetic declination, or 
inclination, that occur simultaneously over 
all parts of the earth. 

The term is also applied to the magnetic decli- 
nation itself. 

These variations are: 

(i.) Secular, or those occurring at great cycles 
of time. 

(2.) Annual, or those occurring at different 
seasons of the year. 

(3.) Diurnal, or those occurring at different 
hours of the day. 

(4.) Irregular, or those accompanying mag- 
netic storms. The first three are periodical; the 
last is irregular. (See Declination, Angle of. 
Chart, Inclination. ) 



Variation, Secular 



-A variation in 



the magnetic declination which occurs at 
great cycles or intervals of time. (See Dec- 
lination. ) 

Varieties of Circuits. — (See Circuits, 
Varieties of.) 

Variometer, Magnetic An instru- 
ment for comparing the horizontal compo- 
nent of the earth's magnetism in different 
localities. 

Varnish, Electric A varnish formed 

of any good insulating material. 

Shel.ac dissolved in alcohol, applied to a 



thoroughly dried surface and afterwards hard- 
ened by baking, forms an excellent varnish. 



Varnish, Stopping-Off 



■A varnish 



used in electro-plating to cover portions 
which are not to receive the metallic coat- 
ing. 

A good stopping-off varnish is made by mixing 
together 10 parts of resin, 6 parts of beeswax, 
4 parts of sealing-wax and 3 parts of rouge, dis- 
solved in turpentine. (See Stopping-Off.) 



Vat, Depositing 



-The vat in which 



the process of electro-plating is carried on. 
(See Plating, Electro.) 

The depositing vat contains the plating liquid^ 
the metallic anode and the object to be plated. 

Vegetation, Effects of Electricity on 

Most vegetable fibres contract when 



an electric current is passed through them 
while on the living plant. 

Some experiments appear to show that electric 
charges and currents hasten the germination and 
growth of certain plants. Other experiments 
seem to show that under certain circumstances 
electric currents retard plant growth. The di- 
rection of the currents is probably of main im- 
portance. 

Velocimeter. — Any apparatus for measur- 
ing the speed of a machine. 

Velocity, Angular The velocity of 

a body moving in a circular path, measured, 
not as usual, by the length of its path divided 
by the time, but with reference to the angle 
it subtends and to the length of the radius. 

Unit angle is that angle subtended by a part 
of the circumference equal to the length of the 
radius, or 57 degrees 17 minutes 44 seconds .8 
nearly. — (Daniell. ) 

Unit angular velocity is the velocity under 
which a particle moving in a circular path, whose 
radius equals unity, would traverse unit angle in 
unit time. 

Velocity, New Unit of The kine. 

(See Kine.) 

Velocity of Discharge. — (See Discharge, 
Velocity of.) 

Velocity Ratio.— (See Ratio, Velocity.) 



Veil.] 



543 



[Tib. 



Teiitilation of Armature. — (See Arma- 
ture, Ve?itilation of.) 

Vernier. — A device for the more accurate 
measurement of small differences of length 
than can be detected by the eye alone, by 
means of the direct reading of the position 
of a mark on a sliding scale. 

The sliding scale is called the vernier. There 
are a variety of vernier scales in use. 

Vertical Component of Earth's Magnet- 
ism. — (See Component, Vertical, of Earth's 
Magnetism. ) 

Vertical Electrostatic Voltmeter. — (See 
Voltmeter, Vertical, Electrostatic. ) 

Verticity, Poles of, Magnetic The 

earth's magnetic poles, as determined by 
means of the dipping needle. 

The point of the north where the angle of dip 
is 90 degrees. (See Map or Chart, Inclination.) 

Vibrating 1 . — Moving to-and-fro. 

Vibrating 1 Bell. — (See Bell, Vibrating) 

Vibrating Contact. — (See Co7itact, Vibrat- 
ing.) 

Vibration. — A to-and-fro motion of the 
particles of an elastic medium. (See Wave.) 

Vibration or Wave, Amplitude of 

The ratio that exists in a wave between 
the degree of condensation and rarefaction 
of the medium in which the wave is propa- 
gated. 

The amplitude of a wave is dependent on the 
amount of energy charged on the medium in 
which the vibration or wave is produced. 

A vibration or wave is a to-and-fro motion pro- 
duced in an elastic material or medium by the 
action of energy thereon. Sound, light and heat 
are subjectively effects produced by the action of 
vibrations or waves, which in the case of sound 
are set up in the air, and, in that of light and 
heat, in a highly tenuous medium called the lumi- 
niferous ether. Objectively they are the waves 
themselves. 

As the amplitude of a sound wave increases, the 
loudness or intensity of the sound increases. As 
the amplitude of the ether wave increases, the 
brilliancy of the light or the intensity of the light 
or heat increases. 



Let A C, Fig. 561 represent an elastic cord or 
string tightly stretched between A and C. If 
the string be plucked by the finger, it will move 
to-and-fro, as shown by the dotted lines. Each 
to-and-fro motion is called a vibration. The 




Fig. J 6 1. Amplitude of Wave. 
vertical distance B D, or B E, represents the 
amplitude of the vibration, and the sound pro- 
duced is louder, the greater the amount of energy 
with which the string has been plucked, or, in 
other words, the greater the value of B D, or 
BE. 

Vibrations assume various forms in solid or 
fluid media, but in all cases the amplitude will 
increase with the increase in the energy that 
causes the vibration. 

Vibration Period. — (See Period, Vibra- 
tion) 

Vibration, Period of The time 

occupied in executing one complete vibration 
or motion to-and-fro. 

— The position 



Vibration, Phase of — 

of the particles in motion in a wave or vibra- 
tion at any instant of time during the wave 
period, as compared with a zero line, or a line 
passing through their mean or middle position. 

Vibrations, Isochronous Vibra- 
tions which perform their to-and-fro motions 
on either side of the position of rest in equal 
times. 

The vibrations of a pendulum are practically 
isochronous, no matter what the amplitude of the 
swing may be, that is, whether the pendulum 
swings through a large arc or a small arc, pro- 
vided this arc be not very great. 

All vibrations that produce musical sounds may 
be regarded as isochronous; that is, in any case, 
the time required to complete a to-and-fro motion 
is the same at the beginning when the sound is 
loud, as at the end, when it is faint. 

Vibrations, Sympathetic Vibra- 
tions set up in bodies by waves of exactly the 
same wave rate as those produced by the 
vibrating body. 

The pitch or tone of the note produced by the 
body set into sympathetic vibration, is exactly the 



Tib.] 



544 



[Vol, 



same as the pitch or tone of the exciting waves or 
vibrations. 

Hertz's experiments show that sympathetic vi- 
brations are excited by electro-magnetic waves. 
(See Electricity, Hertz's Theory of Electro-Mag- 
netic Radiations or Waves.) 

Titrations, Sympathetic, Electrical 

— Vibrations set up in circuits, by the effect 
of pulses in neighboring circuits, that are of 
exactly the same mean length. 

Titrations, Synchronous Vibra- 
tions that are performed not only in the same 
time as one another, but which pass through 
the same portions of their to-and-fro move- 
ment at the same time. 

Tibrator, Electro-Magnetic — A 

lever, or arm, automatically moved to-and- 
fro by the alternate attractions of an electro- 
magnet and an opposing spring, or by the 
successive action of two electro-magnets. 

In either case the movement of the lever is 
utilized to permit the action of first one and then 
the other device. Automatic or trembling bells 
are operated by means of an electro-magnetic 
vibrator. 

Tillari Critical Point. — A term proposed 
by Sir William Thomson for that strength of 
magnetic field at which the reversal of the 
effects of tension occurs. 

Both magnetic susceptibility and permeability 
are affected by mechanical stress, vibration and 
changes of temperature. In a weak magnetic 
field the susceptibility of iron wire is increased by 
longitudinal tension, while in a strong field it 
may be decreased. The particular strength of 
field at which the reversal occurs is called the 
Villari critical point. 

Tiscosity, Magnetic — That prop- 
erty of iron or other paramagnetic substance 
in virtue of which a certain time is required 
before a given magnetizing force can pro- 
duce its effects. (See Hysteresis, Viscous.) 

Tiscous Hysteresis. — (See Hysteresis, 
Viscous?) 

Tis-Tiva. — The energy stored in a moving 
body, and therefore the measure of the amount 
of work that must be performed in order to 
biing a moving body to rest. 



If M, is the mass and V, the velocity 

MV 3 

The Vis-Viva = 

2 

Vitreous Electricity. — (See Electricity \. 
Vitreous?) 
Titrite. — An insulating substance. 

Tolatilization, Electric A term 

sometimes used instead of electric evapora- 
tion. — (See Evaporation, Electric?) 

Tolcanic Lightning. — (See Lightning,. 
Volcanic?) 

Tolt. — The practical unit of electro- 
motive force. 

Such an electromotive force as is induced 
in a conductor which cuts lines of magnetic 
force at the rate of 100,000,000 per sec. 

Such an electromotive force as would 
cause a current of one ampere to flow against 
the resistance of one ohm. 

Such an electromotive force as would 
charge a condenser of the capacity of one 
farad with a quantity of electricity equal to 
one coulomb. 

10 s absolute electro-magnetic units of elec- 
tromotive force. 

Tolt- Ammeter.— A wattmeter. 

A variety of galvanometer capable of di- 
rectly measuring the product of the difference 
of potential and the amperes. (See Watt- 
meter?) 

Tolt Ampere.— A watt.' (See Watt?) 

Volt-Coulomb. — The unit of electric work. 

The joule. (See Joule.) 

Tolt, Mega One million volts. 

Tolt, Micro The one-millionth of a 

volt. 

Toltage. — This term is now very com- 
monly used for either the electromotive force 
or difference of potential of any part of a 
circuit as determined by the reading of a 
voltmeter placed in that part of the circuit. 

Toltage, Terminal The electro- 
motive force expressed in volts of a dynamo 
or other electric source, as indicated by a 
voltmeter placed across its terminals. 

The terminal voltage is greater than that on 
the leads or conductors at some distance from 



Yol.] 



545 



[Vol 



the source and less than that generated by the 
source. 

There is an exception to this general statement 
in the case of certain leads connected with an 
alternating dynamo-electric machine. (See Ef- 
fect, Ferranti.) 

Yoltaic Arc— (See Arc, Voltaic) 

Yoltaic Battery. — (See Battery, Voltaic) 

Voltaic Battery Indicator. — (See Indica- 
tor, Voltaic Battery.) 

Yoltaic Battery Protector. — (See Pro- 
tector, Voltaic Battery.) 

Yoltaic Cell.— (See Cell, Voltaic.) 

Yoltaic Cell, Bichromate — (See 

Cell, Voltaic, Bichromate) 

Yoltaic Cell, Bunsen's (See Cell, 

Voltaic, Bunsen's.) 

Yoltaic Cell, Callaud's (See Cell, 

Voltaic, Callaud's) 

Yoltaic Cell, Capacity of Polarization of 

(See Cell, Voltaic, Capacity of Polar - 

izatio7i of) 

Yoltaic Cell, Closed-Circuit (See 

Cell, Voltaic, Closed-Circuit) 

* Yoltaic Cell, Contact Theory of 

(See Cell, Voltaic, Com act Theory of) 

Yoltaic Cell, Creeping- of (See 

Cell, Voltaic, Creeping in) 

Yoltaic Cell, Daniell's (See Cell, 

Voltaic, Daniell's) 

Yoltaic Cell, Double-Fluid (See 

Cell, Voltaic, Double-Fluid) 

Yoltaic Cell, Dry (See Cell, Vol- 
taic, Dry) 

Yoltaic Cell, Gravity (See Cell, 

Voltaic, Gravity) 

Yoltaic Cell, Grenet (See Cell, 

Voltaic, Grenet) 

Yoltaic Cell, Grove (See Cell, Vol- 
taic, Grove) 

Yoltaic Cell, Leclanche (See Cell, 

Voltaic, Leclanche) 

Yoltaic Cell, Local Action of (See 

Action, Local, of Voltaic Cell) 



Yoltaic Cell, Meidinger (See Cell, 

Voltaic, Meidinger.) 

Yoltaic Cell, Negative Plate of 

(See Plate, Negative, of Voltaic Cell) 

Yoltaic Cell, Open-Circuit — (See 

Cell, Voltaic, Open-Circuit) 

Yoltaic Cell, Poggendorff —(See 

Cell, Voltaic, Poggendorff) 

Yoltaic Cell, Polarization of (See 

Cell, Voltaic, Polarization of) 

Yoltaic Cell, Positive Plate of 

(See Plate, Positive, of Voltaic Cell) 

Yoltaic Cell, Siemens-Halske — 

(See Cell, Voltaic, Siemens-Halske) 

Yoltaic Cell, Simple (See Cell, 

Voltaic, Simple) 

Yoltaic Cell, Single-Fluid (See 

Cell, Voltaic, Single-Fluid) 

Yoltaic Cell, Smee (See Cell, Vol- 
taic, Smee) 

Yoltaic Cell, Standard (See Cell, 

Voltaic, Standard) 

Yoltaic Cell, Standard, Clark's 

(See Cell, Voltaic, Standard, Clark's^) 

Yoltaic Cell, Standard, Clark's, Ray- 

leigh's Form of (See Cell, Voltaic, 

Standard, Rayleigh's Form of Clark's) 

Yoltaic Cell, Standard, Fleming's 

— (See Cell, Voltaic, Standard, Fleming's) 

Yoltaic Cell, Standard, Lodge's 

(See Cell, Voltaic, Standard, Lodge's) 

Yoltaic Cell, Standard, Sir Wm. Thom- 
son's (See Cell, Voltaic, Standard, 

Sir William Thomson's) 

Yoltaic Cell, Standardizing' (See 

Cell, Voltaic, Standardizing a) 

Yoltaic Cell, Two-Fluid (See Cell, 

Voltaic, Two-Fluid) 

Yoltaic Cell, Water (See Cell, 

Voltaic, Water) 

Yoltaic Cell, Zinc-Cartoon (See 

Cell, Voltaic, Zinc-Carbon) 

Yoltaic Cell, Zinc-Copper (See 

Cell, Voltaic, Zinc-Copper) 

Yoltaic Circle.— (See Circle, Voltaic) 



Yol. 



546 



[Vol. 



Yoltaic Circuit. — (See Circuit, Voltaic?) 
Voltaic Couple. — (See Couple, Voltaic.) 
Yoltaic Effect.— (See Effect, Voltaic) 
Yoltaic Electricity. — (See Electricity, 
Voltaic.) 

Yoltaic Element. — (See Eleme?it, Vol- 
taic) 

Yoltaic or Current Induction. — (See In- 
duction, Voltaic.) 

Yoltaineter. — An electrolytic cell em- 
ployed for measuring the quantity of the 
electric current passing through it by the 
amount of chemical decomposition effected 
in a given time. 

Various electrolytes are employed in voltam- 
eters, such as aqueous solutions of sulphuric 
acid, copper sulphate, or other metallic salts. 

In the sulphuric acid voltameter shown in Fig. 
562, the battery terminals are connected with pla- 
tinum electrodes, immersed in water slightly acidu- 
lated with sulphuric acid, and placed inside glass 
tubes, also filled with acidulated water. On the 
passage of the current hydrogen appears at the 
kathode, and oxygen at the anode, in nearly the 
proportion of two volumes to one. (See Ozone.) 




Fig. 362. A Sulphuric Acid Voltameter. 

In the case of water containing sulphuric acid 
{hydrogen sulphate) the decomposition would ap- 
pear to be that of the sulphuric acid rather than 
that of the water. The reaction is as follows: 
H 2 S0 4 =H, +S0 4 . 

The hydrogen appears at the electro negative 
terminal or kathode. The S0 4 appears at the 
electro positive terminal or anode, but combines 
with one molecule of water, thus, S0 4 -f- H 2 = 
H s S0 4 -[-0, gaseous oxygen being driven off at 
the anode. 

Voltameters are not as well suited as galva- 
nometers for the measurement of electric currents, 
because a certain electromotive force must be 
reached before electrolysis is effected. 



The voltameter in reality measures the cou- 
lombs, and, therefore, is valuable as a current 
measurer only when the current is constant. 

Coulomb-meter would, therefore, be the pref- 
erable term. 

Then, again, time is required to produce the 
results, and considerable difficulty is experienced 
in maintaining the current strength constant, 
either on account of variations in the electro- 
motive force of the source, or of variations in the 
resistance of the voltameter. 

Voltameter, Copper A voltameter 

in which the quantity of the current passing 
is determined by the weight of copper de- 
posited. 

A current, the strength of which is constant, is 
passed through the voltameter for a given time. 
The kathode, preferably of platinum, is thor- 
oughly cleaned and dried with a current of heated 
air and accurately weighed before and after. 
The current strength is then deduced from the 
increase in weight and the time. 

A galvanometer is kept in the circuit of the 
battery and voltameter. If a Daniell battery is 
used, it should be kept on closed-circuit through 
a resistance for some time before use, in order to 
insure normal current. 

It will be noticed that the indications of this 
voltameter are based on the gain in weight of the 
kathode. The loss in weight of the anode is mis- 
leading, owing to secondary chemical action and 
disintegration. 

Yoltaineter, Gas A term sometimes 

used for volume voltameter. (See Voltam- 
eter, Volume.) 

Yoltaineter, Siemens' Differential 

A form of voltameter employed by Sir Wil- 
liam Siemens for determining the resistance of 
the platinum spiral used in his electric pyrom- 
eter. (See Pyrometer, Siemens' Electric.) 

Two separate voltameter tubes, provided with 
platinum electrodes and filled with dilute sulphu- 
ric acid, are provided with carefully graduated 
tubes to determine the volume of the decomposed 
gases. (See Voltameter, Volume.) 

A current from a battery is divided by a suit- 
able commutator into two circuits connected re- 
spectively with the two voltameter tubes. In one 
of these circuits a known resistance is placed, in 
the other the resistance to be measured, i. e., the 
platinum coil used in the electric pyrometer. 



Vol.] 



547 



[Vol. 



Toltaineter, Silver A voltameter 

in which the quantity of the current passing- 
is determined by the weight of silver de- 
posited. 

A solution of silver nitrate is used as the elec- 
trolytic liquid. When the current to be measured 
is strong the strength of the silver nitrate solution 
is made stronger. 



Voltameter, Tolinne 



■A voltameter 



in which the quantity of the current passing 
is determined by the volume of the gases 
evolved. 

In some forms of volume voltameter in which 
dilute sulphuric acid is electrolyzed, both the 
hydrogen and the oxygen are measured, either 
separately or together. 

In one form of volume voltameter the hydrogen 
only is collected, and thus the error in volum- 
etric determinations arising from the decrease in 
volume from the formation of ozone is avoided. 
The evolved oxygen is isolated from the hydrogen 
by placing a porous jar between the electrodes. 
The negative electrode, is formed of platinum 
fused in the tube, which, for ease of connec- 
tion, is partially filled with mercury. 

The graduated glass tube, in which the hy- 
drogen is collected, is maintained at a nearly con- 
stant temperature by means of a water column. 
A thermometer is provided for corrections of 
volume as affected by temperature. 

The voltameter contains dilute sulphuric acid, 
about 30 per cent, of acid. 

Voltameter, Weight A voltameter 

in which the quantity of the current passing 
is determined by the difference in the weight 
of the instrument after the circuit has passed 
for a given time. 

A weight voltameter consists essentially of 
platinum electrodes and some means for thor- 
oughly drying the evolved gases. A vessel filled 
with pumice stone moistened with sulphuric acid, 
or a chloride of calcium tube, may be used for this 
purpose. The voltameter is carefully weighed 
before and after the decomposition. The differ- 
ence in weight gives the weight of the sulphuric 
acid decomposed. 

Voltametric Law. — (See Law, Voltamet- 
rzc.) 

Voltmeter. — An instrument used for meas- 



uring difference of potential. (See Galva- 
nometer. Potential, Difference of. Volt.) 

A voltmeter may be constructed on the principle 
of a galvanometer, in which case it differs from 
an ammeter, or ampere meter, which measures 
the current, principally in that the resistance 
of its coils is greater, and that in an ampere meter 
the coils are placed in the circuit, while in a volt- 
meter they are placed as a shunt to the circuit. 

The difference of potential is determined from 
the reading of a voltmeter, by the fact that accord- 
ing to Ohm's law, the product of the current and 
the resistance is equal to the electromotive force, 

E 

as C == — from which we obtain CxR = E, 
K. 

In the ordinary operation of a voltmeter, the 
action of the current in passing through a coil of 
insulated wire is to produce a magnetic field, 
which causes the deflection of a magnetic needle. 
Since the resistance of the voltmeter i* constant, 
the current passing, and hence the deflection of 
the needle, will vary with the value of E. The 
magnetic field produced by the current deflects 
the magnetic needle against the action of another 
field, which may be either the earth's field, or an 
artificial field produced by a permanent or an 
electro-magnet. Or, it may deflect it against the 
action of a spring, or against the force of gravity 
acting on a weight. There thus arise varieties of 
voltmeters, such as permanent-magnet voltmeters, 
spring voltmeters, and gravity voltmeters. 

Or, the current produced by a given difference 
of potential may be used to heat a wire, and the 
value of the potential difference determined by 
the movement of a needle by the consequent 
expansion of a wire. Cardew's voltmeter operates 
on this principle. (See Voltmeter, Cardew's.) 

Or, the potential difference to be measured 
may be utilized to charge a readily movable 
needle, and thus produce electrostatic attractions 
and repulsions. 

This form of instrument is in reality a form of 
electrometer. (See Electro7neter, Quadrant. 
Attraction, Electrostatic.) 

Voltmeter, Cardew's A form of 

voltmeter in which the potential difference is 
measured by the amount of expansion caused 
by the heat of a current passing through a 
fixed resistance. 

The current produced by the difference of 
potential to be measured is passed through a high 



Vol.] 



548 



[Tol. 



resistance wire of platinum silver, the expansion of 
which is caused to move a needle' across a 
graduated arc. The wire is thin and therefore 
quickly acquires the temperature due to the 
current. 

The Cardew voltmeter possesses an advantage 
of being independent of changes of temperature. 
It is also capable of being used to measure the 
potential difference of alternating currents. 

Voltmeter, Closed-Circuit A volt- 
meter in which the points of the circuit, be- 
tween which the potential difference is to be 
measured, are connected with a closed coil 
or circuit, and which gives indications by 
means of the current so produced in said 
circuit. 

All galvanometer-voltmeters are of the closed- 
circuited type. 

The Weston standard voltmeter shown in Fig. 
563 is a closed-circuit voltmeter. 




Fig. 563. Weston Standard Voltmeter. 

Voltmeter, Electro-Magnetic —A 

form of voltmeter in which the difference 
of potential is measured by the movement of 
a magnetic needle in the field of an electro- 
magnet. (See Voltmeter?) 

Voltmeter, Gravity A form of volt- 
meter in which the potential difference is 
measured by the movement of a magnetic 
needle against the pull of a Weight. 

Sir William Thomson's balance instruments are 
used as gravity voltmeters. (See Voltmeter.) 

Voltmeter, Magnetic-Vane A volt- 
meter in which the potential difference is 
measured by the repulsion exerted between a 



fixed and a movable vane of soft iron placed 
within the field of the magnetizing coil. 

A pointer, fixed to the moving vane, serves to 
measure the amount of the repulsion, and conse- 
quently the potential difference producing the 
magnetizing current. The moving vane moves 
under the magnetic repulsion against the action 
of a spring. Discs of copper for damping the 
movements ©f the movable vane, are placed be- 
fore and behind it. 

Voltmeter, Multi-Cellular Electrostatic 

An electrostatic voltmeter in which a 



series of fixed and movable plates are used 
instead of the single pair employed in the 
quadrant electrometer. 

The movable pairs of plates are connected to a 
movable axis and placed vertically above one 
another. To the top of the axis is fixed a light 
aluminium needle or pointer, which moves over a 
graduated scale. A series of fixed plates, suita- 
bly supported and insulated from the ground, 
alternate with the needle plates. 

Voltmeter, Open-Circuit A volt- 
meter in which the points of the circuit where 
potential difference is to be measured are 
connected with an open circuit and give in- 
dications by means of the charges so pro- 
duced. 

Electrometer-voltmeters are of the open-cir- 
cuited type. 

Voltmeter, Permanent Magnet A 

form of voltmeter in which the difference of 
potential is measured by the movement of a 
magnetic needle under the combined action 
of a coil and a permanent magnet, against the 
pull of a spring. (See Voltmeter^ 

Voltmeter, Reducteur or Resistance for 

(See Reducteur or Resistance for 

Voltmeter?) 

Voltmeter, Vertical Electrostatic 

— A form of voltmeter the needle of which 
moves in a vertical instead of in a horizontal 
plane. 

The construction of the vertical electrostatic 
voltmeter is, in general, similar to that of the 
quadrant electrometer. (See Electrometer, Quad- 
rant.) 



Yol. 



549 



[Wat. 



The fixed and movable sectors, the pointer and 
the graduated scale, however, are in vertical in- 
stead of horizontal planes. 




Vertit 



'oltmeter. 



Fig. s 64. 

The general arrangement of the vertical elec- 
trostatic voltmeter will be readily understood by 
an inspection of Fig. 564. 

Volume Voltameter. — (See Voltameter, 
Volume?) 
Vortex Atom. — (See Atom, Vortex) 



Vortex Cylinder.— (See Cylinder, Vor- 
tex.) 

Vortex-Ring- Field. — (See Field, Vortex- 
Ring.) 

Vulcabeston. — An insulating substance 
composed of asbestos and rubber. 

Vulcanite. — A variety of vulcanized rub- 
ber extensively used in the construction of 
electric apparatus. 

Vulcanite is sometimes called ebonite from its 
black color. It is also sometimes called hard 
rubber. 

Though an excellent insulator, vulcanite will 
lose its insulating properties by condensing a film 
of moisture on its surface. This can be best re- 
moved by the careful application of heat. 

The surface is very liable to become covered by 
a film of sulphuric acid, due to the gradual oxi- 
dation of the sulphur. Mere friction will not re- 
move this film, but it may be removed by wash- 
ing with distilled water. A thick coating of var- 
nish will obviate this last defect. 

Vulcanized Fibre.— (See Fibre, Vtdcan- 
ized.) 



w 



W. — A contraction sometimes used for 
watt. 

IV. — A contraction sometimes used for 
work. 

W. — A contraction sometimes used for 
weight. 

Wall Plug-.— (See Plug, Wall.) 

Wall Socket.— (See Socket, Wall.) 

Ward. — A term proposed b\ James Thom- 
son for a line and direction in a line. 

Sir William Thomson thus defines the ward of 
magnetization: " The ward in which the magnet- 
izing force urges a portion of the ideal northern 
magnetic matter or northern polarity." 

Waring- Anti-Induction Cable. — (See 
Cable, Anti-Induction, Waring) 

Waste Field. — (See Field, Jfagnetic, 
Waste.) 

Watches, Demagnetization of Pro- 



cesses for removing magnetism from 
watches. 




Fig. 365. Wright's Demagnetization Apparatus. 

The demagnetiza'ion of watches can be readily 
effected by a method proposed by J. J. Wright. 



Wat.] 



550 



[Wat. 



The watch is held by its chain and slowly lowered 
to the bottom of a hollow conical coil of wire, and 
then slowly withdrawn from the coil. 

The wire is wound on the coil, as shown in 
Fig. 565, in the shape of a cone, viz.: with a 
single turn at the top, and gradually increasing 
in number of turns towards the bottom. The 
conical coil is connected with a source of rapidly 
alternating currents. 

As the watch is lowered into the coil, it gradu- 
ally becomes more and more powerfully magnet- 
ized with alternately opposite polarities, thus 
completely removing any polarity it previously 
possessed. As it is now slowly raised from out 
the hollow cone, this magnetization becomes less 
and less, until, if removed from the conical coil 
while high above its apex, all sensible traces of 
magnetism will have disappeared. 

Watchman's Electric Register. — (See 
Register, Watchman 's Electric) 

Water Battery. — (See Battery, Water) 

Water-Dropping" Accumulator. — (See Ac- 
cumulator, Water-Dropping.) 

Water, Electrolysis of The de- 
composition of water by the passage through 
it of an electric current. 

Water does not appear to conduct electricity 
when pure; it is therefore not quite certain that 
pure water can be electrolytically decomposed. 
The addition of a small quantity of sulphuric 
acid, or of a metallic salt, however, renders its 
electrolysis readily accomplished. (See Vol- 
tameter.) 

In the opinion of most, it is the sulphuric acid 
that is decomposed rather than the water. 

Water Horse-Power. — The Indian Gov- 
ernment's term for horse-power developed 
by falling water. 

The estimate is made by the following simple 
rule : 15 cubic feet of water falling per second 
through 1 foot equals I horsepower. 

Water-Jet Telephone Transmitter.— (See 

Trans7iiitter, Water-Jet Telephone) 

Water - Level Alarm. — (See Alarm, 
Water or Liquid Level) 

Water-Proof Wire. — (See Wire, Water- 
Proof) 

Water Pyrometer. — (See Pyroi7ieter, 
Siemens Water) 



Water Rheostat.— (See Rheostat, Water) 

Water Toltaic Cell.— (See Cell, Voltaic, 
Water) 

Watt. — The unit of electric power. The 
volt-ampere. 

The power developed when 44.25 foot- 
pounds of work are done per minute, or 
0.7375 foot-pounds per second. 

The ? i ¥ of a horse-power. 

There are three equations which give the 
value of the watts, viz. : 

(1.) C E = The watts. 

(2.) C 2 R = The watts. 

(3.) - 2 = The watts. 

Where C = the current in amperes ; E = the 
electromotive force in volts, and R == the resist- 
ance in ohms. (See Energy, Electric.) 

Watt Arc— (See Arc, Watt) 

Watt Generator. — (See Ge?ierator, Watt) 

Watt-Hour. — A unit of electric work. 

A term employed to indicate the expendi- 
ture of an electrical power of one watt, for an 
hour. 

Watt-Hour, Kilo The Board of 

Trade unit of work equal to an output of one 
kilo-watt for one hour. 

Watt, Kilo One thousand watts. 

A unit of power sometimes used in stating 
the output of a dynamo. 

A dynamo of 20 units, or a 20-unit machine, is 
one capable of giving an output of 20 kilo-watts. 

Watt-Meter. — A galvanometer by means 
of which the simultaneous measurement of 
the difference of potential and the current 
passing is rendered possible. 

The watt-meter consists of two coils of insu- 
lated wire, one coarse and the other fine, placed 
at right angles to each other as in the ohm-meter, 
only, instead of the currents acting on a sus- 
pended magnetic needle, they act on each other 
as in the electro-dynamometer. 

Watt-Minute. — A unit of electric work. 

An expenditure of electric power of one 
watt for one minute. 

Watt-Second. — A unit of electric work. 

An expenditure of electric power of one 
watt for one second. 



Web.] 



551 



[Wav 



Wave. — A disturbance in an elastic me- 
dium that is periodic both in space and 
time. 

Ware, Electric An electric disturb- 
ance in an elastic medium that is periodic 
both in space and time. (See Oscillations, 
Electric) 

Waves, Amplitude of The ampli- 
tude of a vibration. (See Vibration or 
Wave, Amplitude of) 

Waves, Displacement Waves pro- 
duced in the ether of dielectrics by means of 
electric displacement. 

The electric stress applied to a dielectric to pro- 
duce electric displacement soon strains it to its 
utmost and no further displacement can occur 
until the direction of the electric power is re- 
versed. A rapidly intermittent current therefore 
can pass through a dielectric and thus produce a 
series of displacement waves. 

Dielectrics, therefore, may be considered as 
pervious or transparent to rapidly intermittent or 
reversed periodic currents, but opaque or imper- 
vious to continuous currents. A condenser inter- 
polated in a telephone circuit does not prevent tele- 
phonic communication, though it does effectually 
stop all continuous currents. 

Waves, Electro-Magnetic — Waves 

in the ether that are given off from a circuit 
through which an oscillating discharge is 
passing, or from a magnetic circuit under- 
going variations in magnetic intensity. 

Waves, Electro-Magnetic, Interference 

of Interference effects similar to those 

produced in the case of waves of light, ob- 
served in the case of electro-magnetic radi- 
ations, or waves, in which one system of 
waves, retarded a half wave length behind 
another system of equal wavelength and am- 
plitude, results in a complete loss of motion 
of the particles of the ether they tend to 
simultaneously affect. 

In order that complete interference may take 
place, it is necessary 

(i.) That the two waves, or system of waves, 
must meet in opposite phases. That is, that one 
be retarded back of the other one-half a wave 
length, or some odd number of half wave lengths. 

(2.) That the waves simultaneously affect the 



same particles of ether in which they are mov- 
ing. 

(3.) That the energy charged on the ether in 
the shape of waves of electro-magnetic radiation, 
must be equal in the case of each system of waves. 

(4.) That the two systems of waves must have 
the same wave length. 

These conditions, it will be seen, are exactly 
the same as in the case of the interference of 
light. 

It will, of course, be readily understood that if 
electro-magnetic radiations can produce the 
effect of resonance, they must also necessarily 
produce interference effects. 

Waves, Electro-Magnetic, Reflection of 

Reflection of electro-magnetic waves 

similar to the reflection of waves of light. 

In his experiments on electro-magnetic radia- 
tions, Dr. Hertz shows that true reflection of 
electro-magnetic waves occurs from the surfaces 
of certain substances placed in the path of the 
waves. 

In some experiments made in a large room, 
Dr. Hertz obtained undoubted indications of re- 
flection of electro-magnetic waves from the walls 
of the room. 

Waves of Condensation and Rarefaction. 

— The alternate spheres of condensed and 
rarefied air by means of which sound is 
transmitted. (See Waves, Sound.) 

Waves, Sound Waves produced in 

air or other elastic media by the vibrations 
of a sonorous body. (See Sound.) 

Way Line. — (See Line, Way.) 

Weather Cross. — (See Cross, Weather.) 

Weber. — A term formerly employed for 
the unit of electric current, and replaced by 
ampere. (See Ampere) 

The term weber was originally used to express 
a quantity of electricity equal to what is nov 
called one coulomb, and a current designated by 
one weber per second. It was, however, used 
finally as a unit of current. 

Weber. — A term proposed by Clausius ana! 
Siemens for a magnetic pole of unit strength, 
but not adopted. 

This same term was also employed to desig- 
nate the unit strength of current, now replaced 
by the term ampere. 



Web.] 



552 



[Wei. 



Weber's Theory of Dialling" net ism. — 

(See Diamagnetism, Weber's Theoiy of.) 

Weight, Atomic The relative 

weights of the atoms of elementary sub- 
stances. 

Since the atoms are assumed to be indivisible, 
they must unite or combine as wholes and not 
as parts. Although we cannot determine exactly 
the actual weights of the different elementary 
atoms, yet we can determine their relative weights 
by ascertaining the smallest proportions in which 
any two elements that combine atom for atom 
will unite with each other. Such liumbers 
will represent the relative weights of the atoms 
as compared with hydrogen. 

Weight Voltameter. — (See Voltameter, 
Weight.) 
Weights and Measures, Metric System 

of A system of weights and measures 

adopted by almost all civilized nations except 
English-speaking, and by the scientific world 
generally. 

For measures of length, the one ten -millionth 
part of the quadrant of a meridian of the earth is 
taken as the unit of length. This unit of length 
is called a metre, and various subdivisions and 
multiples of its length are made on the decimal 
system. 

For a system of weights, the weight of one 
£ubic centimetre of pure water at 39.2 degrees 
Fahr., the temperature of the maximum density of 
water, is taken as the unit of weight. This is 
called a gramme, and various multiples and sub- 
divisions of this unit are made on the decimal 
system. 

The following table of French measures and 
their corresponding English values are taken 
from Deschanel's " Elementary Treatise on 
Natural Philosophy ": 

Length. 

I millimetre = .03937 inch, or about ^ inch. 

1 centimetre = -3937 inch. 

1 decimetre = 3. 937 inches. 

1 metre = 39-37 inches = 3.281 feet =3 
I.0936 yard. 

1 kilometre = 1093.6 yards, or about ~ mile. 

Deschanel gives the length of the meter as 
equal to 39.370432 inches. 

U. S. Coast Survey Bull. No. 9 of 1889, gives 
value of m j ter = 39.36980 inches. Therefore, 
5,-37 is probably as accurate as any other figure. 



Area. 
I square millimetre = .00155 square inch. 
1 square centimetre = .155 square inch. 
1 square decimetre = 15.5 square inches. 
1 square metre = 1550 square inches = 10.764 
square feet = 1.196 square yards. 

Volume. 

1 cubic millimetre = .000061 cubic inch. 

1 cubic centimetre = .061025 cubic inch. 

1 decimetre = 61.0254 cubic inches. 

Cubic metre = 61025 cubic inches = 35.3156 
cubic feet = 1.308 cubic yards. 

The litre (used for liquids) is the same as the 
cubic decimetre, and is equal to 1.7617 pint, or 
.22021 gallon. 

Mass and Weight. 

1 milligramme = .01543 grain. 

1 gramme = 15.432 grains. 

1 kilogramme = 15432.3 grains = 2.205 pounds 
avoirdupois. 

More accurately, the kilogramme is 2.20462125 
pounds. 

Miscellaneous. 

1 gramme per square centimetre = 2.0481 
pounds per square foot. 

1 kilogramme par square centimetre = 14.223 
pounds per square inch. 

1 kilogrammetre = 7.2331 foot-pounds. 

I force de cheval == 75 kilogrammetres per 
second, or 542^ foot pounds per second, nearly, 
whereas 1 hor=e-power (English) = 550 foot- 
pounds per second. 

Conversion of English into French measures ; 
Length. 

1 inch = 2.54 centimetres, nearly. 

1 foot = 30.48 centimetres, nearly. 

1 yard = 91.44 centimetres, nearly. 

1 statute mile = 160933 centimetres, nearly. 

More accurately, I inch = 2. 5399772 centi- 
metres. 

Area. 

1 squareinch = 6.45 square centimetres, nearly. 

1 square foot = 929 square centimetres, nearly. 

1 square yard = 8361 square centimetres, 
nearly. 

1 square mile = 2.59 X 10 1 ° square centimetres, 
nearly. 

Volume. 

I cubic inch = 16.39 cubic centimetres, nearly. 

1 cubic foot = 283 1 6 cubic centimetres, nearly- 



WeL] 



553 



[WeL 



I cubic yard = 764535 cubic centimetres, 
nearly. 

1 gallon = 4541 cubic centimetres, nearly. 

Mass. 
1 grain = .0648 gramme, nearly. 
1 ounce avoirdupois = 28.35 grammes, nearly. 
I pound avoirdupois = 453.6 grammes, nearly. 
1 ton = 1. 016 X io 6 grammes, nearly. 
More accurately, I pound avoirdupois = 
453-59 26 5 grammes. 

Velocity. 
1 mile per hour = 44-7°4 centimetres per 
second. 

1 kilometre per hour = 27.7 centimetres per 
second. 

Density. 
1 pound per cubic foot = .016019 gramme per 
cubic centimetre. 

62.4 pounds per cubic foot = 1 gramme per 
cubic centimetre. 

Force {assuming g = 9S1). 
Weight of 1 grain = 63.57 dynes, nearly. 

" I ounce avoirdupois = 2.78 X 10 4 

dynes, nearly. 
" 1 pound avoirdupois = 4.45 X io 5 

dynes, nearly. 
« 1 ton = 9.97 X io 8 dynes, nearly. 

" 1 gramme = 981 dynes, nearly. 

44 1 kilogramme = 9.81 X io 5 dynes, 

nearly. 
Work {assuming g = 981). 
1 foot-pound = 1.356 X io 7 ergs, nearly. 
1 kilogrammetre = 9.81 x io 7 ergs, nearly. 
Work in a second by one theoretical "horse- 
power" = 7.46 X io 9 ergs, nearly. 

Stress {assuming g = 981). 
I pound per square foot = 479 dynes per 
square centimetre, nearly. 

1 pound per square inch = 6.9 X io 4 dynes per 
centimetre, nearly. 

1 kilogramme per square centimetre = 9.81 
X io 5 dynes per square centimetre, nearly. 

760 millimetres of mercury at o degree C. = 
1. 014 X 10 s dynes per square centimetre, nearly. 
30 inches of mercury at o degree C. = 1.163 
X 10 s dynes per square centimetre, nearly. 

Welding, Electric Effecting the 

welding union of metals by means of heat of 
electric origin. 

In the process of Elihu Thomson, the metals 



are heated to electric incandescence by currents 
obtained from transformers, and are subsequently 
pressed or hammered together. 

Fig. 566, shows the Thomson apparatus for the 
direct system of electric welding. The dynamo 
is combined with the welding apparatus. The 
armature contains two separate windings; one of 
fine wire, in series with the field magnet coils, 
and another of very low resistance, being formed 
of a U-shaped bar of copper. No commutation 
is used, the alternating currents being well 
adapted for heating purposes. The terminals of 
the dynamo are, therefore directly connected to 
the clamps that hold the bar to the welder. 

Fig. 567, shows the apparatus for the Thomson 
Indirect System of Electric Welding. This sys- 
tem is applicable to heavy work, and to cases 
where more than one welding machine is operated 
by the current from a single dynamo. 

In this case a high tension current is converted 




Fig. J 6 6. The Thomson Direct Welder. 

into the large welding current employed, by means 
of a suitably proportioned transformer. 

The welding process is the same in either sys- 
tem, and consists essentially in leading the weld- 
ing current into the pieces to be united through 
their points of junction when brought into firm 
end contact. As the current is led across the 
junction the temperature rises sufficiently to soften 
the metal, when the pieces are firmly pressed to- 
gether by the motion of the clamps or holders. 

In the process of Benardos and Olzewski, the 
heat of the voltaic arc is employed for a some- 
what similar purpose, but by a different process. 

In the Thomson system of electric welding 
alternating currents are employed. They are 
either supplied by an alternating current dynamo 
or by a transformer. 

The process of welding is substantially as fol- 



Wei.] 



554 



[Win. 



lows, viz. : the welding junctions are made slightly- 
convex, so as to touch in but one part of their 
opposing faces. They are made to touch near 
their centres and the welding heat is first reached 
near their points of junction. Pressure is then 
applied by means of a screw, lever or hydraulic 
pressure until all the surfaces are at the welding 
temperature. 

This operation requires in practice but a few 
seconds for small work, and at the most but a 




Fig. 567. The Thomson Indirect Weluer. 

few minutes for larger work. The heating is 
practically local, extending in most cases a dis- 
tance equal to about the diameter of the weld. 

For the purpose of controlling the electro- 
motive force, and thus adapting the same welder to 
different classes of work, when a transformor is 
used, a second transformer provided with a mov- 
able core is placed in series with the first. A 
number of coils of insulated wire are placed in a 
segment of a split-ring laminated-core. These 
may be connected in series or in multiple by a 
switch. An iron armature placed within the 
split ring encloses the annular core and acts as 
the low-resistance secondary. When this is placed 
so as to embrace the primary coils, the difference 
of potential will be different than if moved to one 
side or the other of the ring. 

Welding* Transformer. — (See Trans- 
former, Welding) 

Wheatstone's Electric Balance. — (See 
Balance, Wheatstone's Electric.) 

Wheatstone's Electric Bridge.— (See 

Bridge, Wheatstone's Electric.) 
Wheel, Barlow's or Sturgeon's A 

wheel or disc of metal capable of rotation on 
a horizontal axis, that is set into rotation when 
placed between the poles of magnets and 



traversed by a current of electricity from the 
centre to the circumference. 

Wheel, Phonic A wheel maintained 

in synchronous rotation by means of timed 
electric impulses sent over a line, and em- 
ployed in Delany's synchronous multiplex 
telegraphic system. 

The phonic wheel was invented by La Cour, but 
was first put into successful operation in multiplex 
telegraphy by Delany in his system of synchronous 
multiplex telegraphy. (See Telegraphy, Synchron- 
ous Multiplex, Delany^s System.) Delany ob- 
tains the exact synchronism of the phonic wheel 
by means of a series of correcting electric impulses, 
automatically sent over the line on the failure of 
the phonic wheel at either end of the line to ex- 
actly synchronize with that at the other end. 

Wheel, Reaction, Electric A wheel 

driven by the reaction of a convective dis- 
charge. (See Flyer, Electric.) 

Wheel, Trolley A metallic wheel 

connected with the trolley pole and moved 
over the trolley wire on the motion of the car 
over the tracks, for the purpose of taking the 
current from the trolley wire by means of 
rolling contact therewith. 

Whirl, Electric A term employed 

to indicate the circular direction of the lines 
of magnetic force surrounding a conductor 
conveying an electric current. (See Field, 
Electro-Magnetic.) 

This is more correctly called a magnetic whirl. 
(See Whirl, Magnetic.) 

Whirl, Expanding Magnetic One 

of the magnetic whirls which are sent out 
from a conductor through which a current of 
gradually increasing strength is passing, or 
from a magnet whose magnetism is increas- 
ing. 

These magnetic whirls, according to Hertz, 
move outward through free ether with the velo- 
city of light. 

Whirl, Magnetic The lines of mag- 
netic force which surround the circuit of the 
conductor conveying an electric current. 

Whistle, Steam, Automatic Electric 

— A steam whistle, employed on foggy days 
in some systems of railway signals, when the 



Whi.] 



555 



[Wir. 



visual signals cannot be seen, in which the 
passage of the steam through the whistle is 
automatically obtained by the closing of an 
electric contact, or the passage of the loco- 
motive over a certain part of the track. 

White Heat— (See Heat, White.) 
' White Hot.— (See Hot, White) 

Wimshurst Electrical Machine. — (See 
Machine, Wimshnrst Electrical.) 

Wind, Electric — The convection 

stream of air particles produced at the ex- 
tremities of points attached to the surface of 
charged, insulated conductors. (See Con- 
vection, Electric. Flyer, Electric) 

Windage of Dynamo. — A term proposed 
for the air gap between the armature and the 
pole pieces of a dynamo. 

This term is not much used. 

Winders, Telegraphic Paper Ap- 
paratus for winding or coiling the paper fillets 
used on telegraphic registers. 

When moved by means of a spring they are 
generally styled automatic winders. 

Winding, Ampere A single wind- 
ing or turn through which one ampere passes. 

Ampere-winding is used in the same significa- 
tion as ampere-turn. (See Turn, Ampere.) 

Winding, Bifilar A winding of a 

coil of wire in which, instead of winding the 
wire in one continuous length, it is doubled 
on itself and then wound. 

This method is employed in resistance coils, so 
as to avoid the induction effects. (See Coil, 
Resistance.) 

Winding, Compound, of Dynamo-Electric 

Machine A method of winding in 

which shunt and series coils are placed on 
the field magnets. (See Machine, Dynamo- 
Electric, Compound- Wound) 



Winding, Series 



-A winding of a 



dynamo-electric machine in which a sin- 
gle set of magnetizing coils are placed on the 
field magnets, and connected in series with 
the armature and the external circuit. (See 
Machine, Dynamo-Electric , Series- Wound.) 
Window-Tube Insulation. — (See Insula- 
tor, Window-Tube) 



Wipe Spark.— (See Spark, Wipe) 

Wiping Contact. — (See Contact, Wiping) 

Wire, Air-Line That portion of a 

circuit which is formed by air-strung wires, in 
contradistinction to the portion which passes 
through underground or submarine cables. 

Wire, Binding, for Telegraph Lines 

— The wire used for securing lines of wire 
conductors to the insulators. 

The line wire rests against the insulators at as 
small an area of contact as possible, generally 
only a mere edge. In order to attach the wire 
to the insulator, and protect the wire from chaf- 
ing, it is secured to the insulator by binding with 
wire. 

Wire, Block A line or wire em- 
ployed in a block system for railroads, con- 
necting a block tower with the next tower 
on each side of it. (See Railroads, Block 
System for) 

Wire, Braided A conducting wire 

covered with a braiding, as distinguished from 
a wire that is merely wrapped with insulating 
material. 

Cotton or silk is used for braiding. The cov- 
ering is often coated by a layer of some insu- 
lating gum or varnish dissolved in a rapidly 
drying liquid. It is sometimes covered with melted 
pararffne. 



Fig. j6S. Braided Wire. 

A copper wire covered with insulating material 
and then braided is shown in Fig. 568. 

Wire, Calling A wire employed in 

a telegraphic or telephonic system, by means 
of which a subscriber communicates with the 
central office, or one central office communi- 
cates with another. 

This wire is termed the calling wire in order to 
distinguish from the wire actually used for talking 
or telegraphing. 

Wire, Conductibility and Sizes of 

For tables giving the resistance, size, weight 
per foot, etc., of wire according to some of 
the principal wire gauges see pages 254 and 
256. 



Win] 



556 



[TVir. 



Wire, Copper, Hard-Drawn Copper 

wire that is drawn three or four times after 
annealing. 

The drawing subsequent to annealing renders 
the wire hard and elastic, with but a trifling de- 
crease in its conductivity. A hard-drawn wire, 
of course, possesses greater limits of elasticity 
than soft-drawn wire, and, theretore, in the case 
of air lines, permits of the use of a longer distance 
between adjacent poles. 

Wire, Copper, Soft-Drawn Copper 

wire that is softened by annealing after 
drawing. (See Wire, Copper, Hard- 
Drawn.) 

Wire, Dead, of Armature That 

part of the wire on the armature of a dynamo 
which produces no electromotive force or 
resultant current. 

It is called dead because it does not move 
through the field of the machine. 

Wire, Duplex — An insulated con- 
ductor containing two separate parallel wires. 

Wire, Earth-Grounded —A wire 

one terminal of which is grounded or put to 
earth, so that the earth forms a part of the 
circuit in which the wire is placed. 

Wire, Feeding" — A term sometimes 

applied to the wire or lead of a multiple cir- 
cuit which feeds the main. 

In a system of electric railroads the feeding 
wires feed the trolley wires. 

Wire Finder. — (See Finder, Wire.) 

Wire, Fuse A readily fusible wire 

employed in a safety catch to open the cir- 
cuit when the current is excessive. (See 
Catch, Safety.) 

Wire Gauge, Vernier (See Gauge, 

Wire, Micrometer?) 

Wire, Grounded (See Ground or 

Earth?) 

Wire, House — In a system of in- 
candescent electric lighting any conductor 
that is connected with a service conductor 
and leads to the meter in the house. 

Wire, Insulated — Wire covered 

"with any insulating material. 



Cotton and silk are generally employed for in- 
sulating purposes, either alone, or in connection 
with various gums, resins, or other materials, 
which are rendered plastic by heat, but which 
solidify on cooling. India rubber, caoutchouc, 
and various mixtures and compounds are also em- 
ployed for the same purpose. 

For most of the purposes of line wires, high in- 
sulating powers, combined with a low specific 
inductive capacity, are required in the insulating 
materials. 

For overhead wires a waterproof covering is 
necessary. In the neighborhood of combustible 
materials, some fireproof covering is desirable. 

Wire, Lead A lead fuse wire. 

Wire, Line In telegraphy the wire 

that connects the different stations with one 
another. 

In bell and annunciator circuits, the term line 
wire is sometimes applied to all circuits other 
than the main line. 

In arc-light circuits the term line wire is applied 
to the entire metallic circuit, to which the lamps 
are connected in series. 

Wire, Main The principal wire. 

In any system of bell circuits, the main wire is 
the wire which runs from one pole of the battery 
to one of the springs of all the pushes, in distinc- 
tion from the line wires, or the rest of the wires 
in the battery circuit. 

Wire, Message A line or wire em- 
ployed in a block system for railroads, ex- 
tending along the road and used for local 
traffic or business. (See Railroads, Block 
System for.) 

Wire, Negative A term sometimes 

applied to that wire of a parallel circuit which 
is connected to the negative pole of a source. 

Wire, Neutral The middle w r ire of 

a three-wire system of electric distribution. 

Wire, Omnibus An onmibus bar. 

(See Bars, Omnibus?) 

A bus bar or wire. (See Wires, Bus.) 

Wire, Paraffined Wire wrapped or 

braided with some textile material and after- 
wards coated with paraffine. 

The term paraffined wire is sometimes limited 
to a wrapped wire that is afterwards paraffine 
coated. 



IVir.] 



557 



[Wir. 



Wire, Positive The wire or con- 
ductor connected to the positive pole or ter- 
minal of any electric source. 

Wire, Potentiometer The wire of 

a potentiometer which has been calibrated in 
order to measure the drop of potential in any 
circuit. (See Potentio?neter.) 

Wire, Return The wire or con- 
ductor by means of which the current returns 
to the electric source after having passed 
through the electro-receptive devices. (See 
Sources, Electric. Device, Electro-Recep- 
tive^) 

Wire, Shade Guard (See Guard, 

Wire Shade?) 

Wire, Slide — A wire of uniform 

diameter employed in Wheatstone's electric 
bridge for the proportionate arms of the 
bridge. 

A sliding contact key moves over the slide 
wire and determines the length of the arms. 
Some forms of bridges have a double or a triple 
slide wire. (See. Bridge, Electric, Slide-Form of .) 

Wire, Span The wire employed in 

systems of electric railways for holding the 
trolley wire in place. 

The span-wire is used when the poles are 
erected on both sides of the street or road-bed, 
and the trolley wire, suitably insulated from the 
span wire, is suspended therefrom. 

Wire, Suspending, of Aerial Cable 

The wire from which an aerial cable is strung 
<or suspended. 

In case the aerial cable is unusually heavy the 
suspending wire is replaced by a wire rope. (See 
■Cable, Aerial.) 

Wire, Taped — A conducting wire 

covered with an insulating material in the 
shape of tape. 

A wire covered with an insulating material and 
.subsequently taped is shown in Fig. 569. 



Fig. j6q. Taped Wire. 

Wire, Tinned Copper wire covered 

with a coating of tin prior to its being insu- 



lated. 



The coating of tin is for the purpose of insur- 
ing greater ease in soldering. It is also usetul 
in case vulcanized rubber is used for the insulator, 
to prevent the sulphur from attacking the copper. 

Wire, To To fix or place the con- 
ductors or mains for any electric circuit. 

Wire, Train A line of wire em- 
ployed in a block system for railroads, con- 
nected with the general dispatcher's office, 
and used for sending train orders only. (See 
Railroads, Block System for.) 

Wire, Trolley The wire over which 

the trolley passes in a system of electric rail- 
ways, and from which the current is taken to 
drive the motors on the cars. 

A bare conductor or wire, supported over- 
head on suitable hangers and provided for 
transmitting current by the trolley to the 
motor connected with the car on the passage 
of the trolley wheel over its surface. (See 
Wheel, Trolley.) 

Trolley wires, being necessarily bare, are 
carefully insulated at their points of attachment 
to all supports. 

Wire, Trolley, Continuous A trol- 
ley wire or conductor employed in overhead 
dependent systems of electric railways. (See 
Railroads, Electric, Dependent System of 
Motive Power for?) 

Wire, Trolley, Sectional or Divided 

— A trolley wire or conductor for systems of 
electric railroads in which the wire is divided 
into a number of separate sections that are 
suitably connected with the generating dyna- 
mo by means of feeder wires. (See Rail- 
roads, Electric, Dependent System of Motive 
Power for.) 

Wire, Trunk A main line or wire, 

extending between two distant stations, such 
as between two large cities, and provided 
solely for communication between them, not 
being tapped at intermediate points. 

Wire, Twin A conductor, consist- 
ing of two separately insulated wires, bound 
together by an additional insulating covering. 

Wire, Water-Proof A wire pro- 
tected from the weather by a coating of any 
waterproof material. 



Win] 



558 



[Wir. 



"Wire, Wrapped Wire that is insu- 
lated by placing strands of some insulating 
material, like cotton, parallel to its length, 
and then wrapping a number of strands 
around the wire. 

The wrapped wire is afterwards either coated 
with paraffine or other insulator, or is used with- 
out such coating. 

Wires, Bus A term sometimes used 

for omnibus bars or wires. 

The wires which receive the full current 
generated by the electric source, and carry 
it to the feeders. 

The bus-wires collect the current from all the 
sources, hence the name. 

Wires, Breaking-Weight of The 

weight required to be hung at the end of a 
wire in order to break it. 

Ordinary copper wire will break at about 17 
tons to the square inch of area of cross section. 
Common wrought iron breaks at 25 tons to the 
square inch. These figures are to be regarded as 
approximate only, since almost inappreciable 
differences in the physical condition of metals, as 
well as slight variations in their chemical com- 
position, often produce marked differences in 
their breaking weights. 

Wires, Cross (See Cross, Electric?) 

Wires, Crossing* A device employed 

in telegraphic circuits whereby a faulty con- 
ductor is cut out of the circuit of a telegraph 
line by crossing over to a neighboring, less 
used, line. 

To cut out a faulty section of wire in any cir- 
cuit, such as C D, in the circuit A B C D E, Fig. 
570, a cross-connection is made to a line X Y, 
running near it, and which may be temporarily 
thrown out of use. By this means the interrup- 
tion of an important circuit may be repaired. 
A B C „ D E 



a 



X I ™ y 

Fig. 570. Crossing Wires. 

Wires, Dead Disused and aban- 
doned electric wires. 

The term dead is often applied to a wire 
through which no current is passing. The term, 
however, is more properly applied to a wire 
formerly employed, but subsequently abandoned. 



Dead wires in the neighborhood of active wires 
are a constant menace to life and property, and 
should invariably be carefully removed. 

It is often a matter of considerable importance 
to be able to determine whether or not a current 
is passing through a wire. When the wire is not 
enclosed in a moulding, or fastened against a 
wall, this can readily be ascertained by bringing 
a small compass needle near the wire, when it 
will tend to set itself across the wire. 

The term dead wire, as will be seen, is used in 
two distinct senses. 

Wires, Leading-In The wires or 

conductors which lead the current through 
(into and out of) an electric lamp. 

The term leading-in wires is generally applied 
to incandescent electric lamps, Geissler or 
Crookes tubes, and to various other apparatus. 

Wires, Leading-Up — Wires em- 
ployed for raising an aerial cable to the cable 
hangers. 

Wires, Omnibus A term sometimes 

used for bus wires. (See Wires, Bus.) 

Wires or Conductors, Continuous 

Wires or conductors free from joints. 

Wires or conductors without soldered or 
twisted joints or without any joints whatso- 
ever. 

Wires, the entire lengths of which have 
been taken from the hitherto uncut coil of 
wire from the draw plate. 

Strictly speaking, any metallic circuit consists 
of a continuous wire, whether in one piece or in 
several sections or pieces. The preferable term 
would appear to be un jointed wires or conductors. 

Wires, Phantom A term applied 

to the additional circuits or wires obtained in 
any single wire or conductor by the use of 
some multiplex telegraphic system. (See 
Telegraphy, Multiplex. Telegraphy, Syn- 
chronous-Multiplex, Delanys System.) 

Wires, Pilot In a system of incan- 
descent lighting, where a comparatively low 
potential is employed on the mains, thin wires 
leading directly from the generating station 
to different parts of the mains, in order ta 
determine the differences of potential at such 
points. 



Win] 



559 



[Wor. 



Pilot wires indicate on a voltmeter the differ- 
ence of potential at the various points. The pilot 
wires extend to the various seats of supply, and 
so give instant warning of any change in the 
value of the potential. 

Wires, Pressure In a system of 

incandescent electric lighting, wires or con- 
ductors, series-connected with the junction 
boxes, and employed in connection with suit- 
able voltmeters, to indicate the pressure at 
the junction boxes. 

The pressure wires are sometimes called the 
pilot wires. 

Wires, Tap The wires or conduc- 
tors used to carry the current from the feed- 
ers or mains at the pole to a near point on 
the trolley wire. 

Wiring". — Collectively the wires or con- 
ducting circuits used in any system of electric 
distribution. 

Wiring. — Placing or establishing the wires 
or conductors for any electric circuit. 



Wiring, Case 



Placing or establish- 



ing electric conductors or wires that are held 
in place on the walls or ceiling of a room, by 
means of continuous cleats. 

Wiring, Cleat Placing or estab- 
lishing electric conductors or wires that are 
held in place on the walls or ceiling of a 
room by means of suitably shaped insulating 
cleats. 

Wiring-, Inside The conductors 

that, in a system of incandescent electric 
lighting, lead to the interior of the house or 
area to be lighted. 

Wirinsr, Moulding — Electric con- 
ductors or wires that are held in place on the 
walls or ceiling of a room by means of suit- 
ably shaped mouldings. 

Work.— The product of the force by the 
distance through which the force acts. 

A force whose intensity is equal to one pound 
acting through the distance of one foot, does an 
amount of work equal to one foot-pound. 

Work is to be distinguished from the more gen- 
eral term energy. 



Work, Electric The joule. (See 

Joule.) 

The product of the volts by the coulombs. 
I joule = 10,000,000 ergs, or .73732 foot-pounds. 
" = 1 volt-coulomb. 
" =1 watt for 1 second. 

Work, Electric, Unit of The volt- 
coulomb or joule. (See Volt-Couloi?ib. Joule.) 

Work, Unit of The erg. 

The amount of work done when a force of 
one dyne acts through the distance of one 
centimetre. (See Erg.) 

Raising one gramme against gravity, through 
the distance of one centimetre, requires an 
amount of work equal to 980 ergs. 

Work, Units of Various units em- 
ployed for the measurement of work. 

The following table of Units of Work is taken 
from Hering's work on Dynamo-Electric Ma- 
chines : 

Work. 

I erg = 1 dyne-centimetre. 

1 " = .0000001 joule. 

= 981.00 ergs. 

= .00001 kilogr. -metre. 

= 1937-5 er g s - 

f 10,000,000 ergs, 
•7373 2 4 foot- 
pound, .101937 
kilogram • metre, 
.0013592 metric 
horse- power for 
one second. 

.0013406 horse-power 

for one second. 
= .0009551 pound- 
" Fah., heat unit. 

" =.0005306 pound- 

Centig., heat unit. 
" = .OC02407 kilogr.- 

Centig., heat unit. 
" = .0002778 watt-hour. 

1 foot-pound = 13562600 ergs. 

" = 1.35626 joules. 

" = . 13825 kilogr. metre. 

" =.0018434 metric 

horse-power for 
e second. 
•« ..., =.00181818 horse- 

power for one 
r ^cond. 



1 gramme-centimetre . 
I foot-grain 

I joule, or 1 volt-cou-") 
lomb, or I watt I 
during every second 
or 1 volt-ampere 
during every 
second 

1 volt ampere during 
every second 



f = 1 



I 



Wor.l 

I foot pound, 



I kilogram- metre. 



I watt-hour 



.=.0012953 pound- 

Fah., heat unit. 
. = .0007196 pound- 
Centig., heat unit. 
. = .0003264 kilogr.- 
Centig., heat unit. 
. = .0003767 watt-hour. 
. = 98100000 ergs. 
. = 9.81000 joules. 
. = 7.23314 foot-pounds. 
. = .01333 metric horse- 
power for one 
second. 
. = .013151 horse power 

for one second. 
. =.009369 pound Fah., 

heat unit. 
. = .005 205 pound- 
Centig., heat unit. 
. = .002361 kilogr.- 
Centig., heat unit. 
. = .002725 watt-hour. 
. = 3600 joules. 
. = 2654.4 foot-pounds. 
.=366.97 kilogram- 
metres. 
. = 3.4383 pound-Fah., 

heat units. 
.=1.9102 pound- 
Centig., heat units. 
, . = .8664 k i 1 o g r . - 
Centig., heat units. 
..= .0013592 metric 
horse power hour. 
. .... = .0013406 horse- 
power-hour. 

I metric h. -p. -hour = 2648700 joules. 

" ...._= 1952940 foot-pounds. 

" ....=270000 kilogram- 

metres. 
«■ ....=2529.7 pound-Fah., 

heat units. 
«« ....=1405.4 pound- 

Centig., heat units. 

*' = 637.5 kilogr. -Centig., 

heat units. 
. . . . = 735.75 watt-hours. 
«« . . . . = .98634 horse-power- 

hour. 

I horse -power-hour = 2685400 joules. 

" = 1980000 foot- 

pounds. 
" . ...= 273740 kilogram. 



560 [W01V 

1 horse-power-hour = 2564.8 pound-Fah.,. 

heat units. 

" . . . . = 1424.9 pound- 

Centig. , heat units- 

" ....=646.31 kilogr. - 

Centig , heat units. 

" = 745.941 watt-hours. 

" . . . . = 1. 01385 metric horse- 
power-hour. 
Heat. 
I gram-Centig. = .001 kilogram Centi- 
grade. 

I pound-Fahr = 1047.03 joules. 

= 772 foot-pounds. 

= 106.731 kilogram- 
metres. 
=.55556 pound-Centi- 
grade. 
=.25200 kilogram- 
Centigrade 

= .29084 watt-hour. 

= .0003953 metric 

horse power-hour. 
= .0003899 horse- 
power hour. 

1 pound-Centig = 1884.66 joules. 

. = 1389 6 foot-pounds. 

=192.116 kilogram- 
metres. 
= 1.8000 pound- 
Fahrenheit. 
= .4536 kilogram-Centi- 
grade. 

= .52352 watt-hours. 

==.0007115 metric 

horse -power-hour .. 
" =.0007018 horse- 

power-hour. 

1 kilogram Centig = 415495 joules. 

" = 3063.5 foot-pounds. 

" =423.54 kilogram- 
metres. 
«■' =3.9683 pound- 
Fahrenheit. 
" = 2.2046 pound-Centi- 
grade. 

" = 1. 1542 watt hours. 

" = .001569 metric horse- 

power- hv ur 
" .....= .0015472 horse- 

power-hour. 

Working, Direct The transmis- 



Wor.] 



561 



[Yok. 



sion of signals over a telegraph line with- 
out the use of relays or repeaters. 

Working, Multiple, of a Dynamo-Elec- 
tric 3Iachine A term sometimes used 

for the parallel working of dynamo-electric 
machines. (See Working, Parallel, of Dy- 
namo-Electric Machines.) 

Working*, Parallel, of Dynamo-Electric 

Machines The operation of working 

several dynamo-electric machines as a single 
source, by connecting them with one another 
in parallel or multiple arc. 

The effect of parallel working is to reduce the 
internal resistance of the dynamo. 

If a current be required in a circuit at an electro- 
motive force equal only to that of a single machine, 
and the requirements of the circuit are equal to 
the output of more than a single dynamo, a num- 
ber of dynamos must then be coupled in mul- 
tiple. 

Working", Reverse-Current A 

term sometimes used in telegraphy for a 
method of working by means of a double 
current in place of a single current. 

The double-current system of working was de- 
vised by Varley to permit Morse characters to be 
sent rapidly through underground conductors. 
In order to avoid the retardation due to induction, 
the current was reversed between each signal. 
This reversion in the conductor hastened the dis- 
charge of the conductor. 



Working, Series, of Dynamo-Electric 

Machines Such a coupling of several 

dynamo-electric machines as will deliver the 
current supplied by them in series. 

As in all -series connections of sources, there re- 
sults an electromotive force equal to the sum of 
the electromotive forces of the different dynamos. 



Worming, Cable 



-A central core of 



hemp or jute around which are wrapped the 
several separate conductors of a cable con- 
taining more than a single separate conduc- 
tor. 

Wood's Button Repeater. — (See Repeat- 
ers, Telegraphic) 

Wrapped Wire.— (See Wire, Wrapped.) 

Writing, Electrolytic ■ — Imprinting 

written characters on cloths, or other textile 
fabrics, by the electrolytic decomposition of a 
dyeing substance with which they are im- 
pregnated. 

The cloths, etc., to be written on, are impreg- 
nated with an aniline salt, and placed on an insu- 
lated metallic plate next to the salt, which is con- 
nected to one pole of an electric source. The 
other pole is connected to a carbon electrode, 
which is used as the writing stylus or pencil. By 
suitably connecting the terminals the writing is 
obtained in color on a white ground, or in white 
on a colored ground. (See Dyeing, Electric.) 

Writing Telegraphy. — (See Telegraphy, 
Writing.) 



T-Shaped Sparks. — (See Spark, 
V-Shaped.) 
Yale-Lock-Switch Burglar Alarm. — (See 

Alarm, Yale-Lock-Switch Burglar) 

Yoke, Multiple-Brush —A term 

sometimes applied to multiple brush rocker 
of a dynamo or motor. (See Rocker, Mul- 
tiple-Pair Brush.) 

Yoke, Multiple-Pair Brush A 

device for holding a number of pairs of 
brushes of a dynamo-electric machine in such 



a manner that they can be readily moved or 
rotated on the commutator cylinder. 

The brushes are placed side by side on the com- 
mutator cylinder. In such cases the several pairs 
of brushes are so arranged that they can be 
thrown off or out of contact with the commutator 
cylinder while cleaning the cylinder, without stop- 
ping the machine. 

Yoke, Single-Brush A term some- 
times used for single-brush rocker. (See 
Rocker, Single-Brush) 



Yok.] 



562 



[Zon. 



Yoke, Single-Pair -A single-brush 

rocker. (See Rocker, Single-Brush) 

Yoke, Single-Pair Brush A device 

for holding a single pair of collecting brushes 
of a dynamo-electric machine in such a way 



that they can be readily moved or rotated on 
the commutator cylinder. 

Yoked-Horseshoe Electro-Magnet. — (See 
Magnet, Electro, Yoked-Horseshoe.) 



Z. — A symbol sometimes used in electro- 
therapeutics for contraction. 

The use of Z, is for the purpose of avoiding 
the letter C, which has already been used for cur- 
rent or ampere in Ohm's law. Increasing 
strengths of contraction are represented by Z', 
Z", Z"\ 

Z. — A symbol for electro-chemical equiva- 
lent. 

Zero, False A zero taken midway 

between any two equal and opposite deflec- 
tions of a measuring instrument. 

Zero, Inferred A zero deduced or 

inferred from the deflection produced by a 
charge that is to be measured by comparison 
with the value of the deflection by means of 
a known charge in an electrical measuring 
instrument. 

An inferred zero is usually completely off the 
scale, hence its name. It does not actually exist. 

Zero Methods.— (See Method, Null or 
Zero) 

Zero Potential. — (See Potential, Zero) 



Zero, Shifting 



■A zero that changes 



or shifts in position ; a polar zero in a measur- 
ing instrument. 

Zigzag Electro-Magnet. — (See Magnet, 
Electro, Zigzag) 

Zigzag Electromotive Force.— (See 
Force, Electromotive, Zigzag) 

Zigzag Lightning. — (See Lightning, Zig- 
zag) 

Zinc, Amalgamation of The cov- 
ering or amalgamation of zinc with a layer 
of mercury. 

To amalgamate a plate of zinc, its surface is 
first thoroughly cleaned by immersing the plate in 
dilute sulphuric acid of about I part of acid to 



io or 12 parts of water. A few drops of 
mercury are then rubbed over its surface, thus 
coating it with a bright metallic film of zinc 
amalgam. Care must be taken not to use too 
much mercury, since the zinc plate would thus be 
rendered brittle. 

Zinc-Carbon Yoltaic Cell.— (See Cell, 
Voltaic, Zinc-Carbon) 

Zinc-Copper Yoltaic Cell.— (See Cell, 
Voltaic, Zi?ic-Copper) 

Zinc, Crow-Foot — A crow-foot- 
shaped zinc used in the gravity voltaic cell. 
(See Cell, Voltaic, Gravity) 

The term "crow-foot " refers to the shape of 
the claws. It is hardly a happy term. 

Zinc-Lead Yoltaic Cell.— (See Cell, Vol- 
taic, Zinc-Lead) 

Zinc Sender. — (See Sender, Zinc) 

Zincode of Yoltaic Cell. — A term for- 
merly employed to indicate the zinc terminal 
or electrode of a voltaic cell. 

The negative electrode or kathode are prefer- 
able terms. 

Zone, Anelectrotonic — A name 

sometimes given to the polar zone. (See 
Zone, Polar) 

Zone, Kathelectrotonic A name 

sometimes given to the peripolar zone. (See 
Zo7ie, Peripolar) 

Zone, Peripolar A term proposed 

by De Watteville for the zone or region sur- 
rounding the polar zone on the body of 
a patient undergoing electro-therapeutic 
treatment. 

Zone, Polar A term proposed by 

De Watteville for the zone or region surround- 
ing the therapeutic electrode applied to the 
human body for electric treatment. 



APPENDIX. 



References to Words, Terms and Phrases which appear in the Appendix are preceded by the 
•words "See Appendix" ; all other references apply to the main portion of the Dictionary. 



A. —A symbol proposed for ampera, the 
practical unit of electric current. 

a. — A symbol proposed but not adopted 
for acceleration. 

The defining equation is a — — 

This letter is sometimes, though rarely, 
employed as the symbol for ampere. 

a. — A symbol proposed for angle ex- 
pressed in circular measure. 

,r„ , r- • • arc 

The denning equation is a— — - — 

radius 

A. h. — An abbreviation used for ampere 
hour, a commercial unit of electric quan- 
tity. 

A. t. — An abbreviation ior ampere-turn, 
a practical unit of magneto-motive force. 

Abscissas. — Plural of abscissa. 

Absorptive. — Possessing the power of ab- 
sorption. (See Absorption.) 

Acceleration, Angular The time 

rate of change of angular velocity. 

Accumulation Method for Testing Joints 
in Electric Cables. — (See Appendix — 
Method, Accumulation, for Testing Joints 
in Electric Cables.) 

Accumulator, Bi-3Ietallic A term 

applied to a secondary or storage cell in 
which two different metallic substances are 
employed in connection with a single elec- 



trolytic fluid composed of a solution of a 
salt of one of the metals of the plates. 

Many different bi-metallic accumulators 
have been designed; for example, the cop- 
per-lead accumulator, in which plates of 
copper and lead are immersed in an electro- 
lyte of copper sulphate; or the copper-zinc ac- 
cumulator, in which plates of zinc and copper 
are immersed in an electrolyte of zinc sul- 
phate; or the zinc-lead accumulator, in which 
plates of zinc and lead are immersed in an 
electrolyte of zinc sulphate. 

Accumulator, Charge A term 

sometimes employed for a Leyden jar or 
condenser. (See Jar, Leydeii. Condenser.) 

Accumulator, Copper-Lead — An 

electro-chemical or electrolytic accumula- 
tor consisting of plates of copper and lead 
immersed in a solution of copper sulphate. 

Accumulator, Copper-Zinc — An 

electro-chemical or electrolytic accumu- 
lator consisting of plates of copper and 
zinc immersed in a solution of zinc sul- 
phate. 

Accumulator, Current — A term 

sometimes employed for a Barlow wheel 
when used as an electrical accumulator. 
(See Accumulator.) 

A series-wound dynamo-electric machine 
constitutes in reality a current accumulator. 

Accumulator, Electro-Chemical 



563 



Ace] 



564 



[Ala. 



The name generally given to the ordinary 
secondary or storage battery, in which the 
difference of potential is produced by 
chemical action. (See Cell, Storage.) 

Accumulator, Electrolytic —An 

electro-chemical accumulator. (See Appen- 
dix — Accumulator, Electro- Chemical.) 
Accumulator, Storage 



— A term 

sometimes employed for storage cell. (See 
Cell, Storage.) 

Accumulator, Ziuc-Lead An elec- 
trolytic accumulator consisting of plates of 
zinc and lead immersed in a solution of 
zinc sulphate. 

Acoustic Interference. — (See Appendix 
— Interference, Acoustic.) 

Acoustic Resonance. — (See Appendix — 
Resonance, Acoustic.) 

Acoustic Telegraph. — (See Appendix — 
Telegraph, Acoustic.) 

Actinometer. — An instrument devised to 
measure the relative intensity of the sun's 
rays, or of such artificial light as the elec- 
tric light, etc., etc. 

The actinic power of the sun's rays to 
cause chemical decomposition varies with 
the condition of the atmosphere and the 
position of the sun above the horizon. 

Action, Gyrostatic, of Dynamos on Ship- 
board The action which occurs at 

the bearings of a dynamo running on board 
a tossing ship, whereby gyrostatic stresses 
are set up. 

Action, Protective A term pro- 
posed for the protective action afforded by 
a magnetic field to paramagnetic metals 
when exposed to chemical action. 

The proposed term is not good in view of 
the fact that it is used to cover a number of 
other ki ids of protective actions. 

Experiments as to the protective action of 
a magnetic field on iron, nickel and cobalt 
were undertaken by Prof. Rowland and Dr. 
Bell. The results of these experiments, as 
stated by the experimenters, are as follows : 



"When the magnetic metals are exposed 
to action in a magnetic field, such action is 
decreased or arrested at any points where 
the ratio of the variation of the square of the 
magnetic force tends towards a maximum." 

The results obtained by Rowland and Bell 
were apparently at variance with some more 
recent experiments of Squier, and showed 
that the currents produced by couples of 
similar metals when exposed to chemical 
action in a magnetic field had a direction of 
flow through the liquid from the magnetized 
to the non-magnetized electrode — i. e., in the 
opposite direction to that pointed out by 
Squier in the phenomena of the protective 
throw. (See Appendix — Throw, Protective^) 

Adielectric. — A term proposed for sub- 
stances that are not dielectrics, that is, 
substances whose electric conductivity at 
ordinary temperatures decreases as the tem- 
perature increases. 

Adjustable Rheostat. — (See Appendix — 
Rheostat, Adjustable.) 

Aelotropic. — Heterogeneous with respect 
to direction. 

Aelotropic Medium. — (See Appendix— 
Medium, Aelotropic.) 

After-Working of Dielectric. — (See Ap- 
pendix — Dielectric, After- Working of.) 

Age-Coating of Chamber of Incandescent 
Electric Lamp. — (See Appendix — Chamber 
of Incandescent Electric Lamp, Age-Coat- 
ing of) 

Ageing of Incandescent Electric Lamp, 
— (See Appendix — Lajnp, Incandescent 
Electric, Ageing of. ) 

Agglomerate Leclanche" Voltaic Cell. — 
(See Appendix — Cell, Voltaic, Agglomerate 
Leclanche.) 

Air Telegraphy. — (See Appendix — Teleg- 
raphy, Air.) 

—An alarm sounded 



Alarm, Frost 



or set in operation by means of mechan- 
ism operated by a fall of temperature to or 
below 32 F. 

— A selenium 



Alarm, Photo-Electric 



All.] 



505 



[Alt. 



cell proposed for use in connection with the 
circuit of an electric source and suitable 
electro-receptive devices, so as to permit 
the passage of a stronger current through 
the circuit and the consequent sounding of 
an alarm on the exposure of one of its faces 
to the light. 

By means of this device a burglar, carry- 
ing a light, can be made automatically to ring 
an alarm bell, and thus call the attention of 
a watchman or policeman to his presence. 

Allotropism. — Allotropy. (See Allo- 
tropy.) 

Alternating Current Arc.— (See Appendix 
— Arc, Alternating Current.) 

Alternating Current Potentiometer. — 

(See Appendix — Potentiometer, Alternat- 
ing Current.) 

Alternating Current Rotary Transformer. 

— (See Appendix — Transformer, Alternat- 
ing Current Rotary.) 

Alternating Electromotive Force.— (See 
Appendix — Force, Electromotive, Alternat- 
ing.) 

Alternation, Periodicity of The 

number of alternations per second pro- 
duced by a generator. 

The term periodicity of alternation is 
synonymous with frequency, a briefer and 
more commonly employed word. 

When any particular periodicity or fre- 
quency is spoken of, as, for example, 250 
alternations per second, 125 complete periods 
or cycles per second are meant. 

Commercially, the word alternations is 
used for half-periods or double-frequencies. 
A dynamo with 250 alternations per second 
has 125 periods per second. 



Alternations, Co-phasal 



— Alterna- 



tions whose electromotive forces similarly 
and simultaneously vary. 

The maximum and minimum electromo- 
tive forces of co-phasal alternations are both 
simultaneously and similarly directed. 

Any number of periodic functions are said 



to be co-phasal when the ratio between their 
instantaneous values is constant ; when one 
is a maximum all the remainder will be 
maxima, and when one is a minimum all the 
remainder will be minima. 

Alternator, Compensated An al- 
ternating current dynamo-electric machine 
for sustaining a uniform voltage at some 
point of its circuit under varying loads, 
in which the field magnets are excited 
partly by rectified or commuted currents 
taken from separate armature coils, and 
partly by currents furnished by the com- 
muted current from a small transformer, 
whose primary coil is placed in the main 
circuit. 

Alternator, Compound An alter- 
nating current dynamo-electric machine 
whose field magnets are compound-wound. 

The current from the machine is commonly 
run through a series transformer whose sec- 
ondary winding is connected with the field 
magnets through a commutator. 

Alternator, Magnetic An alter- 
nating dynamo-electric machine in which 
permanent field magnets are employed. 

Alternator, Magneto — A term 

sometimes employed for magnetic alter- 
nator. (See Appendix — Alternator, Mag- 
netic.) 

Alternator, Multiphase An alter- 
nating current dynamo capable of produc- 
ing multiphase currents. 



Alternator, Separate-Coil 



■An al- 



ternating current dynamo-electric machine 
in which the field magnets are excited by 
means of current taken from the coils on 
the armature, which current is first recti- 
fied, or caused to flow in one and the same 
direction, by means of a commutator. 

Alternator, Separately-Excited An 

alternating current dynamo-electric ma- 
chine in which the field magnets are ex- 
cited by means of current furnished from a 
separate source. 



Alt.] 



566 



[Amp. 



Alternator, Two-Phase 



An alter- 



nating current dynamo capable of produc- 
ing two-phase currents. 

The term di-phase alternator would appear 
to be preferable. 

Alternators, Parallel Connection of 

— The connection of two or more alternat- 
ing current dynamo-electric machines in 
parallel, so as to form a single electric 
source. 

When two alternating current dynamo- 
electric machines are connected in parallel, 
if the armature self-induction and resistance 
are not too high, and the engines driving the 
dynamos are under control, or in other words 
governed, then such machines, even if out of 
synchronism, when connected, will almost 
immediately pull each other into synchron- 
ism, each promptly exercising an automatic 
control over the other. 

When alternators possess marked synchro- 
nizing power, care must be exercised to 
adjust them fairly to equality of E. M. F. 
and phase, in order that they may not be in- 
jured by mechanical shock due to excessive 
cross currents, when first connected in 
parallel. A certain amount of armature self- 
induction is therefore desirable to render 
parallel working safe. 

It is a matter of prime importance in the 
parallel running of alternators that the 
shape of the wave of E. M. F. is the same in 
all machines. Otherwise cross currents will 
flow between the machines under all adjust- 
ments. A difficulty is occasionally experi- 
enced in the parallel connection of alternators 
of different size, due to differing wave form. 

Alternators, Parallel, Hunting- of 

A periodical increase and decrease in the 
speed of alternators when running in 
parallel connection as motors or as 
dynamos under certain conditions. 

Alternators, Series Connection of 

The connection of two or more alternating 
current dynamo-electric machines in series, 
so as to form a single electric source. 

The series connection of alternating dyna- 
mo-electric machines is impracticable in or- 



dinary work; for, should such connection be 
made when the two machines are furnishing 
currents in the same phase, as soon as either 
machine differs in the slightest degree in 
phase from the other such difference would 
tend to rapidly increase, until the two ma- 
chines were in opposite phases, when, of 
course, no current would be produced. Hence, 
alternators can be run in series only when 
their armatures are mechanically and rigidly 
connected with each other. 

Amalgamating Solution. — (See Appendix 
— Solution, Amalgamating.} 

Amalgamator, Electric Any ap- 
paratus for the electrical treatment of gold 
or silver ores with mercury. 

An electric amalgamator consists essen- 
tially of an amalgamator driven by elec- 
tric instead of by ordinary mechanical power. 

American Morse Code. — (See Appendix — 
Code, American Morse.) 

Ammeter, Steel- Yard A form of 

ammeter in which the strength ot the cur- 
rent is measured by means of the electro- 
magnetic forces applied to one extremity 
of a steel-yard lever provided with sliding 
weights for balancing these forces. 

Ampere, B. A. Such a current as 

would deposit o.oou 18 gramme of silver 
per second from a neutral solution of 
nitrate of silver in distilled water. 

This value of the ampere was adopted by 
the British Association at its meeting held in 
Edinburgh in August, 1892, the English 
Board of Trade, and by the Chicago Congress 
of 1893. 

Equal to the international ampere. 

Ampere-Centimetre. — A term proposed 
as a unit of magnetism. 

The ampere-centimetre as a unit of mag- 
netism is based on an assumption denied by 
some that any unit length of circuit, say one 
centimetre, conveying a unit current of one 
ampere, will generate a constant number of 
lines of magnetic force. 

The proposed unit has not been accepted. 

Ampere, International The value 



Amp.] 



567 



[App. 



of the international ampere adopted by the 
Chicago Congress ot 1893 as equal to one- 
tenth of the unit of current of the C. G. S. 
system of electro-magnetic units, and 
which is represented sufficiently well for 
practical use by the unvarying current 
which when passed through a solution of 
nitrate of silver in water, and in accord- 
ance with certain specifications, deposits 
silver at the rate of 0.001118 of a gramme 
per second. 

Ampere Meter, Milli An ampere 

meter, which measures in milli-amperes 
the current passing through it. 

Ampere Yards. — (See Appendix — Yards, 
Ampere.) 

Anaesthesia. — Insensibility, especially to 
pain. 

Anaesthesia, Electric Nervous in- 
sensibility produced by means of electricity. 

Local anaesthesia is obtained by means of 
induction apparatus in which the number of 
makes and breaks can be readily varied. It 
has been found in certain cases, when the 
makes and breaks follow one another with a 
given rapidity, which can be determined by 
means of the musicalnote produced, that such 
slight operations as the lancing of a felon can 
readily be performed without pain, after the 
part has been subjected to the action of the 
current for but a few minutes. 

Anemograph, Electric — An ap- 
paratus for electrically registering the direc- 
tion and velocity of the wind. 

Angle of Maximum Sensitiveness of Gal- 
vanometer. — (See Appendix — Galvanom- 
eter, Angle of Maximum Sensitive- 
ness of.) 

Angle, Phase The angle com- 
prised between two different current 
maxima. 

Angular Acceleration. — (See Appendix — 
Acceleration, Angular.) 

Annunciator, Speaking- Tube An 

oral annunciator. (See Annunciator, Oral.) 



Annunciator, Swinging 



-A pendu- 



lum annunciator. (See Annunciator, Pe?i- 
dulum.) 

Annunciator Wire. — (See Appendix — 
Wire, Annunciator.) 

Anodic Rays of Vacuum Tube. — (See Ap- 
pendix — Rays, Anodic, of Vacuiun Tube.} 

Anomalous Helix. — (See Appendix — 
Helix, Anomalous .) 

Anomalous Solenoid. — (See Appendix — 
Solenoid, Anomalous.) 

Anomalous Spiral. — (See Appendix — 
Spiral, Anomalous.) 

Anti-Xode. — The point on a vibrating 
body midway between two successive nodes. 
(See Appendix- — Node.) 

The point of maximum motion in a vibrat- 
ing body. 

Apparatus, Individual Signalling 



Any apparatus by means of which individ- 
ual signals are Operated. (See Appendix — 
Signal, Individual.) 

Lockwood arranges the different methods 
according to which individual signals can be 
operated underthe following heads, namely: 

(1.) Signals operated at each sub-station or 
circuit with different strengths of current. 

(2.) Signals operated by currents of op- 
posed direction. 

(3.) Signals operated both by changes in 
the strength and direction of the current. 

(4.) Electro-magnetic step-by-step devices, 
acting to bring the sub-station signals to a 
ringing point differing for each sub-station, 
and then to close a local branch or shunt cir- 
cuit, including a local bell, to operate alter- 
nating mechanism, or in some way to 
introduce a bell magnet into the circuit. 

(5.) Signals operated by means of various 
arrangements of clockwork bells. 

(6.) Signals operated by means of galva- 
nometers, the movements of whose needles 
cause bells to ring. 

To which may be added, signals operated 
by currents of different periodicity. 

Apparatus, Polyphase Apparatus 



App.] 



568 



[Arm, 



operated by polyphase currents. (See Ap- 
pendix — Currents, Polyphase.) 

Apparatus, Selective Signalling" A 

term sometimes used in place of indi- 
vidual signalling apparatus. (See Appendix 
— Apparatus, Individual Signalling^) 

Apparent Besistance. — (See Appendix — 
Resistaiice, Apparent.) 

Arc, Alternating Current An arc 

formed by means of an alternating current. 

Since in the alternating current the elec- 
trodes become alternately positive and nega- 
tive, neither carbon in the case of a carbon 
arc is markedly brighter than the other, and 
the rate of consumption of both carbons is 
the same. 

Arc, Carbon A voltaic arc formed 

between two carbon electrodes. 

The carbon voltaic arc is the one ordina- 
rily employed, and is formed through a cloud 
of volatilized carbon. (See Arc, Voltaic.) 

Arc, Common, of Aurora Glory 

The inner or common arc of an aurora 
glory. (See Appendix — Glory, Aurora.) 

Arc, Continuous Current A vol- 
taic arc produced by means of a continu- 
ous electric current. 

In a continuous current arc the light is 
principally emitted from a crater in the posi- 
tive carbon. 

Arc, Copper A voltaic arc formed 

between two copper electrodes. 

A copper arc is formed through a cloud of 
volatilized copper. Most metallic arcs are 
longer than carbon arcs. They possess the 
characteristic color of the volatilized metal; 
for example, the copper arc is green. (See 
Arc, Voltaic.) 

A copper or other metallic arc would be 
formed from copper or other metallic rod if it 
formed the positive electrode, and a block of 
carbon or other non-metallic substance 
formed the negative electrode, since it is the 
material of the positive electrode that is vola- 
tilized. 

Arc Lighting Dynamo-Electric Machine. 



— (See Appendix — Machine, Dynamo- 
Electric, Arc Lighting.) 

Arc, Two Thousand Candle Power, Pro- 
posed Definition for The light of an 

arc produced by 10 amperes of current 
and 45 volts potential difference between the 
carbons. 

A 450-watt arc restricted as above, 

Such an arc is sometimes called a full arc. 

The difficulty in measuring the photometric 
intensity of a continuous current carbon arc 
is so great that considerable controversy has 
arisen as to whether or not a given candle 
power is present in certain cases. This dif- 
ficulty arises not only from the fact that the 
light is of much greater intensity in certain 
directions than in others, but also from the 
fact that the candle power of an arc having 
a certain watt value may differ greatly with 
the quality of the carbons employed. 

The adoption of the above definition would, 
therefore, seem to be extremely advisable. 

Armature, Balanced An armature 

of an electro-magnet "whose motion to- 
ward or from the magnetic poles is op- 
posed by the pull of a spring, or the action 
of a weight, so that on the cessation of the 
magnetic attraction the armature will be 
caused to assume the position it had before 
the magnetic action began. 

Strictly speaking, such an armature is not 
balanced; the term, however, is a convenient 
one. 

Armature, Balanced An armature 

of a dynamo-electric machine so constructed 
or adjusted that the line joining the centres 
of inertia of all its cross sections practically 
coincides with the axis of rotation. 

A balanced dynamo armature runs 
smoothly and without mechanical jars or 
vibrations. 

Armature, Balanced — 



— An armature 
of a dynamo or motor in which the winding 
is such as to insure electrical symmetry. 

Armature, Coreless, of Dynamo or Motor 

An armature of a dynamo or motor 



Arm.] 



569 



[Ato. 



not provided with a core of iron or other 
magnetizable material. 

Armature, Di-Phase An armature 

of a motor wound so as -to be operated by 
di-phase currents. 

Armature, Magnetic Sticking- of 

The adherence of the armature of an elec- 
tro-magnet to the poles, after the current 
has ceased to pass through the magnetizing 
coils. 

The cause of sticking is to be ascribed to 
the residual magnetism. 

Sticking is sometimes avoided by means 
of core pins, or by a non-magnetizable coat- 
ing of armature or core. (See Appendix — 
Pins, Core.) 

Armature, Polyphase An arma- 
ture of a motor wound so as to be operated 
by polyphase currents. 

Armature Reaction. — (See Appendix — 
Reaction, Armature.) 

Armature, Three-Phase A tri- 

phase armature. (See Appendix — Arma- 
ture, Tri-Phase.) 

The term tri-phase armature would appear 
to be preferable. 

Armature, Tri-Phase An arma- 
ture of a motor wound so as to be operated 
by tri-phase currents. 

Armature, Two-Phase A di-phase 

armature. (See Appendix — Armature, Di- 
Phase.) 

The term di-phase armature would appear 
to be preferable. 

Arms, Side A term applied to the 

supports for the bearings of railway mo- . 
tors. 

Arrival Curve of Telegraphic Circuit.— 

(See Appendix — Curve, Arrival, of Tele- 
graphic Circuit.) 

Arriving Current of Telegraphic Circuit. 

— (See Appendix — Current, Arriving, of 
Telegraphic Circuit.) 

Asoestos-Porcelain. — A porous substance 
somewhat resembling ordinary porcelain. 



Asbestos-porcelain is made by obtaining 
asbestos fibres in an exceedingly fine powder 
and forming this powder into a paste with 
water, consolidating it under heavy press- 
ure, and subsequently exposing the dried 
particles to the effects of a high temperature. 

Asbestos-porcelain, it is claimed, forms a 
material which, though resembling ordinary 
porcelain, is highly porous. It has been suc- 
cessfully used for the porous cells of voltaic 
batteries, for which purposes it is claimed to 
offer a better conducting path for the current 
than the ordinary unglazed earthenware gen- 
erally employed for such purposes. (See Cell, 
P or otis.) 

Astatic Multiplier. — (See Appendix — 
Multiplier, Astatic^ 

Atmosphere, Electric A term for- 
merly employed for a space rilled with 
electric effluvia. (See Appendix — Effluvia, 
Electric.) 

A term sometimes employed for an elec- 
tro-static field. 

A space occupied by or permeated with 
electric sparks or glow. 

Atmosphere, Magnetic ■ A term 

formerly employed for a space filled with 
magnetic effluvia. (See Appendix — 
Effluvia, Magnetic.} 

A term sometimes employed for a mag- 
netic field. 

An atom whose val- 



Atom, Dyad — 

ency, atomicity or combining power is two. 
(See Atomicity. Element.) 



Atom, Heptad 



•An atom whose 



valency or atomicity is seven. (See Atom- 
icity. Element.) 

Atom, Hexad An atom whose 

valency or atomicity is six. (See Atomicity. 
Ele?nent.) 

Atom, Monad An atom whose 

valency or atomicity is one. (See Atomicity . 
Eleme7it.) 

Atom, Pentad An atom whose 

valency or atomicity is five. (See Atom- 
icity. Element.) 



Ato.] 



570 



[Bac* 



Atom, Tetrad An atom whose 

valency or atomicity is four. (See Atom- 
icity. Element?) 

Atom, Triad An atom whose 

valency or atomicity is three. (See Atom- 
icity. Element.) 

Atomic. — Of or pertaining to the atom. 
(See Atom.) 

Attachment, Electric Clamp A 

device employed in connection with a floor 
push, adapted for ready clamping to a 
table or other support for the purpose of 
holding a push button electrically con- 
nected with the floor push. 

Attachment Plug. — (See Appendix — Plug, 
Attachment.) 

Audible Telegraphic Signal. — (See Ap- 
pendix — Signal, Telegraphic, Audible.) 

Audiometer. — A word sometimes used in 
place of Sonometer. (See Appendix — Sonom- 
eter.) 

Aura, Electric A term formerly 

employed for the breeze produced by elec- 
tric convection. (See Convection, Electric.) 

Aurora, Electrostatic ■ — A luminous 

phenomenon attending the production of an 
electrostatic corona. (See Appendix — 
Corona, Electrostatic.) 

Aurora Glory. — (See Appendix — Glory, 
Aurora.) 



Aurora, Polar 



-A term sometimes 



used indifferently for the aurora borealis, 
or the aurora australis. 

Austral Fluid. — (See Appendix — Fluid, 
Austral.) 

Auto-Exciting. — Self-exciting. 

Auto-Induction. — (See Appendix — Induc- 
tion, Auto.) 

Automatic Guard for Series- Connected 
Incandescent Lamps. — (See Appendix — 
Guard, Automatic, for Series-Connected 
Incandescent Lamps.) 

Automatic Photo-Electric Switch. — (See 
Appendix — Switch, Automatic Photo-Elec- 
tric.) 

Automatic Repeater. — (See Appendix — 
Repeater, Automatic.) 

Automatic Telegraph. — (See Telegraph, 
Automatic?) 

Automatic Telegraphic Transmitter. — 

(See Appendix — Transmitter, Automatic 
Telegraphic.) 

Auto-Reversible or Multiple Tele-Radio- 
phone. — (See Appendix — Tele-Radiophone , 
Auto-Reversible or Multiple.) 

Axial Current. — (See Appendix — Cur- 
rent, Axial.) 



9£>. — A symbol employed for magnetic 
induction. 

The defining equation is §§ = pi <D*C 

B. A. Ampere. — (See Appendix — Ampere, 
B. A.) 

B. A. Ohm.— (See Ohm, B. A.) (See Ap- 
pendix — Ohm, B. A.) 

B. T. U. — A contraction for Board of 
Trade unit, the commercial unit of elec- 
trical work adopted by the British Board of 



Trade, viz., the kilowatt-hour, or the amount 
of work which would be accomplished in 
one hour at the rate of one kilowatt. 

This contraction is a bad one, since it is 
already employed for British thermal unit. 

B. T. U.— A contraction for British 
thermal unit. 

Back Magnetization. — (See Appendix — 
Magnetization, Back.) 

Backing Pau. — (See Appendix — Pan, 
Backing.) 



Bac. 



571 



[Bat. 



Backward Induction of Dynamo Arma- 
ture. — (See Appendix — Induction, Back- 
ward, of Dynamo Armature.) 

Bad Earth. — (See Appendix — Earth, 
Bad.) 

Balance, Coulomb's Electric A 

term sometimes employed for Coulomb's 
torsion balance when used for measuring 
the force of electric repulsion. (See Bal- 
ance, Coulomb's Torsion.) 

Balance, Coulomb's Magnetic Torsion 
A name sometimes given to Cou- 
lomb's torsion balance when employed to 
measure the force of magnetic repulsion. 
(See Balance, Coulomb's Torsion.) 

Balance, Duplex The condition 

of a line in duplex telegraphy, when send- 
ing signals leave the home instruments un- 
affected and ready for response to received 
signals. 

Balance, Electro-Dynamic A bal- 
ance form of electro-dynamometer. (See 
Dynamometer, Electro. Balance, Centi- 
Ampere.) 

Balanced Armature. — (See Appendix — 
Armature, Balanced.) 

Balancing Wire or Conductor. — (See 
Appendix — Wire or Conductor, Balanc- 
ing.) 

Barker's Revolving* Contact Breaker. — 
(See Appendix — Breaker, Contact, Barker s 
Revolving.) 

Barker's Wheel. — (See Appendix — 
Wheel, Barker s.) 

Base, Socket A base for holding 

a lamp socket in position. 

Basket, Dipping — A perforated 

basket of non-corrosive material, em- 
ployed for the reception of articles that are 
to be prepared for the process of electro- 
plating by dipping them in the cleansing 
bath. (See lapping.) 

Basket, Stoneware Dipping — A 

stoneware basket in which the articles are 



placed that are to be subjected to the dip- 
ping process in electro-metallurgy. (See 
Appendix — Basket, Dipping.) 

Bath, Electric Light A variety of 

electro-therapeutic bath, in which all the 
patient's body, except the head, is exposed 
to the radiant light and heat of a number 
of incandescent electric lamps placed in- 
side a closed chamber or box. 

By the use of the electric light bath it is 
claimed that the temperature of the body is 
rapidly increased, and that the effect on the 
skin is the same as that of sunshine. The 
therapeutic value of such a bath is, perhaps, 
to be questioned. 

Battery, Compound A term pro- 
posed by Henry for a number of separate 
voltaic cells, coupled so as to form a 
single cell, in contradistinction to a single 
cell. 

The term battery was originally sometimes, 
loosely applied either to indicate a single 
voltaic cell, or a numberof cells so joined to- 
gether as to form a single electric source. 

Indeed, the term is still loosely employed^ 
even at the present day by some writers. In 
the time of Henry the word battery was ap- 
parently indifferently applied to a single- 
cell or a number of cells, and Henry pro- 
posed the term compound battery to distin- 
guish between a single cell, or, as he called it, 
a battery, and a number of cells joined so as 
to form a single source, which he terms a 
compound battery, but which is to-day, by all 
careful writers, termed a battery. 

Battery, Distant A battery em- 
ployed in a telegraphic system at the re- 
ceiving end of the line. 

Battery, Dry — A number of sepa- 
rate dry voltaic cells combined so as to act 
as a single source. 

A dry pile. (See Pile, Dry.) 

Battery, Element of (See Ap- 
pendix — Element of Battery.) 

Battery, Home The battery em- 
ployed in a telegraphic system at the send- 
ing end of the line. 



Bat. 



572 



[Bic. 



Battery, Polarization —A term 

sometimes employed for a secondary or 
storage battery. 

The term secondary or storage battery 
would appear to be preferable. 

Battery, Secondary, Current Efficiency of 
The ratio between the ampere- 
hours of the discharge and the ampere- 
hours of the charge. 

Battery, Secondary, Efficiency of — 

The ratio between the amount of electrical 
work given out by a battery during its dis- 
charge, and the amount of work expended 
in charging it. 

The efficiency of a secondary battery varies 
with the rates of charge and discharge ; the 
higher these rates the lower the efficiency. 

The efficiency of a secondary battery is ob- 
tained by dividing the amount of electrical 
work in joules or watt-hours, which a battery 
will produce after being charged, by the 
amount of similarly estimated electrical work 
expended in charging it. This is generally 
known as the watt-efficiency. 

The current-efficiency is obtained by divid- 
ing the ampere-hours of the discharge by the 
ampere-hours of the charge. 

Battery, Secondary, Watt-Efficiency of 

The ratio between the amount of 

electrical work in watt-hours a battery will 
yield after being charged, and the amount 
of work in watt-hours expended in charg- 
ing it. 

Battery Syringe. — (See Appendix — 
Syringe, Battery.) 

Battery System for Electric Railway. — 
(See Appendix — Railway, Electric, Bat- 
tery System for.) 

Bead, Chain. — (See Appendix — Chain, 
Bead.) 

Bead Lightning. — (See Appendix — Light, 
ning, Bead.) 

Bearing, Magnetic The angle in- 
cluded between the horizontal line from an 
observer to an object and the observer's 
magnetic meridian. 



Bega. — A prefix proposed by Houston 
and Kennelly for a thousand million, or io 9 • 

Begadyne. — A term proposed by Houston 
and Kennelly for one thousand million 
dynes, or io 9 dynes. 

Begerg. — A term proposed by Houston 
and Kennelly for one thousand million ergs, 
or io 9 ergs. 

Beginning of Current. — (See Appendix — 
Current, Beginning of.) 

Begohm. — A term proposed by Houston 
and Kennelly for one thousand million 
ohms ; i. e., io 9 ohms. 

Bell, Electric, Continuous Action 

An electric bell which continues to ring 
when once started until stopped either by 
hand or automatically. 

Bell, Extension A term some- 
times employed for extension call bell. 
(See Bell, Extension Call.) 

Belt, Creeping of An action of a 

belt due to its retractility, whereby the driv- 
ing pulley travels somewhat faster than the 
driven pulley. 

Suppose the belt possesses true elasticity 
or retractile power, then it will be stretched 
on the work side and come back to its 
original length on the idle side. It therefore 
reaches the driving pulley in a stretched con- 
dition and leaves it in a contracted condition. 
It also reaches the driven pulley in a con- 
tracted condition and leaves it in an elongated 
condition. Suppose this stretch or elonga- 
tion is one per cent, in a given case, the driv- 
ing pulley must move 101 feet for every ioo 
feet of the driven pulley, then there is no 
slip of the belt, only a creep. 

The slip of a belt may cause a consider- 
able loss of peripheral velocity in the pulley. 

Belt, Slipping of The slipping of 

a belt on the revolving pulley it covers, 
causing a loss of speed. 

Bicro. — A prefix proposed by Houston 
and Kennelly denoting the thousand- 
millionth part,. or io~ 9 « 



Bic] 



573 



[Bon, 



Bicrofarad. — A term proposed by Hous- 
ton and Kennelly for the thousandth part 
of a microfarad, or io~ 9 farad. 

Bicrohenry. — A term proposed by Hous- 
ton and Kennelly for the thousand-millionth 
part of a. henry, or one centimetre. 

Bi-Metallic Accumulator. — (See Appendix 
— Accumulator, Bi-Metallic.} 



Biologist, Electro 



-One skilled in 



the art of electro-biology. 
Bioscopist, Electro 



-One skilled in 



the science of electro-bioscopy. 

Blavier's Formulae. — (See Appendix — 
Formula, Blaviers.) 

Blavier's Test. — (See Appendix — Test, 
Blaviers.) 

Block, Ceiling — An attachment 

fastened to ceilings for suspending flexi- 
ble cords and connecting them with the 
supply wires of an incandescent system. 

Block, Double, Duplex In teleg- 
raphy, especially in submarine telegraphy, 
duplex transmission obtained by the aid of a 
condenser inserted in each arm of the Wheat- 
stone balance. (See Telegraphy , Duplex, 
Bridge Method of.) 

Block, Service The set of termi- 
nals from which service wires are taken 
to the interior of a building, usually secured 
to a pole or to the exterior of a building. 

Blow, To A phrase frequently 

employed to indicate the fusion of a safety 
fuse. (See Fuse, Safety.) 

Blowing of Fuse. — (See Appendix — Fuse, 
Blowing of.) 

Blowing Point of Fuse. — (See Appendix 
— Fuse, Blowing Foint of.) 

Blue Magnetic Pole. — (See Appendix — 
Pole, Magtietic, Blue.) 

Board, Distributing — A term 

sometimes employed in a system of tele- 
graphic or telephonic communication for a 
cross connecting board. (See. Board, Cross- 
Connecting.) 



Board, Distributing Switch A 

switch board employed for distributing 
electric current to different circuits. 

A distributing switch board is usually pro- 
vided with wedge-plugs and spring-jacks. 

Board, Lightning Arrester In a 

system of telephonic or telegraphic com- 
munication the board to which the light- 
ning arrester is connected. 

The lightning arrester board often forms 
part of the test-board. 

Board, Test In a system of tele- 
phonic or telegraphic communication the 
board, provided with devices for readily 
connecting testing instruments to any par- 
ticular line, to which all the separate lines 
are connected. 

Bob, Polishing A disc of hard, 

tough wood, provided on its edge with a 
ring or rim of tough leather or hide, and 
employed, when mounted on a shaft and 
put into rapid rotation, for polishing ar- 
ticles so as to prepare them for electro- 
plating. (See Plating, Electro.) 

The polishing bobs are charged for use with 
any suitable abrasive material, such as 
emery, etc. 

Bobbed. — A word sometimes employed 
to characterize a surface that has been 
polished by the action of a bob. (See Ap- 
pendix — Bob, Polishing.) 

Body, Inducteous A term proposed 

by Faraday for a body in which a charge 
is induced by the action of a neighboring 
charged body. 

Body, Inductile A term proposed 

by Faraday for the body containing the in- 
ducing electric charge. 

Bolognian Stone. — (See Appendix — Stone, 
Bolognian.) 

Bond, Electric Rail An electric 

bond or connection between contiguous 
rails of a road using a grounded return. 

In a system of electric roads, where the 
return circuit is grounded, the track offers an 



Bon.] 



574 



[Bro. 



excellent return provided the return joints 
between contiguous rails are electrically con- 
nected. To do this thoroughly, requires, of 
course, such an electric connection as will 
render the bonds of no higher linear resist- 
ance than the main body of the rails. 

Bony Current. — (See Appendix — Cur- 
rent, Bony.') 

Booster. — A scarcely euphonious word 
employed to designate a dynamo inserted 
in a special feeder or group of feeders ot 
an Edison incandescent system in order to 
raise the pressure above the rest of the 
system. 

Boreal Fluid. — (See Appendix — Fluid, 
Boreal.') 

Bougie-Metre. — A name proposed for the 
practical unit of illumination. 

A unit of illumination equal to the normal 
illumination from the bougie-decimale at 
a distance of one metre. 

This unit was proposed by a Sub-Commit- 
tee of the American Institute of Electrical 
Engineers on the provisional programme of 
the Chicago International Electrical Con- 
gress of 1893, on the occasion of the World's 
Columbian Exposition. 

The bougie-decimale is practically equal to 
one English standard candle. By making 
the distance equal to one metre, the practical 
unit of illumination will be approximately 
equal to y 1 ^ carcel-metre, or one metre-candle, 
or to one metre-kerze. 

Bow, Yoltaic A voltaic arc. (See 

Arc, Voltaic.) 



Bowl. Stoneware Dipping 



per- 



forated bowl made of stone or earthen ware 
in which articles are placed that are to be 
subjected to the dipping process in electro- 
metallurgy. (See Dipping.) 

Box, Section In a system of elec- 
tric street railways the box containing the 
section switches and fuses used for the 
control of a section or a line section. 

Box, Starting 1 , of Shunt- Wound Motor 



A box provided with a rheostat or 

variable resistance. 

The armature resistance of a shunt-wound 
motor is generally made very low, in order 
to insure high efficiency and constancy of 
speed. In starting the motor, if it is con- 
nected to the constant potential circuit and 
the driving current be permitted to pass 
directly through its armature, the rush of 
current would be sufficient to injure the 
machine. To avoid this the current is first 
sent through a rheostat, or starting box, 
and, when the speed of the motor is suffi- 
ciently high, and a suitable counter-electro- 
motive force is generated in the armature, 
the resistance coils are gradually cut out 
until the motor is connected directly to the 
constant potential mains. 

Branched Series. — (See Appendix — 
Series, Branched.) 

Break Key. — (See Appendix — Key, 
Break.) 

Break, Quick A break of a cir- 
cuit obtained by means of a quick-break 
switch. (See Appendix — Switch, Quick- 
Break.) 

Breaker, Contact Any device for 

opening or breaking an electric circuit. 
Breaker, Contact, Barker's Revolving 

A form of contact breaker in which 

a toothed wheel is rapidly revolved so that 
its teeth pass successively into and out of a 
mercury surface, and a rapid making and 
breaking of an electric circuit connected 
therewith is thus obtained. 

Breaking Down of Dielectric. — (See Ap- 
pendix — Dielectric, Breaking Down of.) 

Bridge, Thomson's A modified 

form of Wheatstone's bridge proposed by 
Kelvin for the measurement of very small 
resistances. 

Broiler, Electric — A device for 

broiling by means of electrically generated 
heat. 

Rods of insulated metal are suitably con- 
nected in parallel, and raised to incandescence 



Bru. 



575 



[Bur. 



by means of electrically generated heat. (See 
Jleat, Electric.) 

In one form of apparatus made, when a 
potential difference of no volts is applied to 
the terminals, a current of seven amperes 
passes and heats the broiler sufficiently for 
use in about three or four minutes. 

Brush, Cup A brush employed in 

cleansing surfaces that are to be prepared 
for electro-plating, and suitably shaped for 
polishing the inside of a cup or other simi- 
lar hollow surface. 

Brush, Inside Box A brush em- 
ployed in cleansing surfaces so as to 
prepare them for electro-plating, suitably 
shaped for polishing the inside of tubular 
surfaces. 

Brush, Potash A brush employed 

in cleansing, by the use of a caustic, sur- 
faces that are to be electro-plated. 

Brush, Thimble A brush employed 

in cleansing articles that are to be pre- 
pared for electro-plating, and suitably 
shaped for such surfaces as the inside of a 
thimble. 

Brushes, Distributing, of Electric Motor 

The brushes of an electric motor 



corresponding in position to the collecting 
brushes of a dynamo-electric machine. 

It is evident that the brushes of an electric 
motor differ somewhat in their function from 
the collecting brushes of a dynamo-electric 
machine, since in the former case the brushes 
act to distribute a current generated outside 
the motor to certain coils on the armature of 
the motor, while in the latter case they com- 
mute the direction of the current generated 
in the armature. 

Brushes, Finishing — A term em- 
ployed in electro-plating for finer brushes 
than scratch brushes. 

Bucking. — A word employed in the 
operation of street railway passenger cars 
for the sudden stopping of a car, as if by a 
collision. 



The car sometimes refuses to go further ; 
it often, however, stops and then goes ahead 
again almost immediately as if nothing had 
occurred. The cause of bucking is to be as- 
cribed to the fact that the armature being 
grounded, if a second ground occurs in any 
part of the machine, between the armature 
and the trolley, with the ordinary method of 
connecting up, a heavy current flows, produc- 
ing an intensely strong magnetic field and 
at the same time the armature is short cir- 
cuited by means of the two ground connec- 
tions. Under these circumstances the 
dynamo, being short circuited, operates as a 
powerful electro-magnetic brake. This effect 
also occurs when the armature is short-cir- 
cuited by heavy sparking at the brushes, or 
bad insulation (not to ground) in the com- 
mutator. 

The term bucking is sometimes used 
loosely for any cause which prevents an 
electric motor from properly operating. 

Buffing. — Preparing surfaces for the re- 
ception of an electro-plating by subjecting 
them to the polishing action of a revolving 
wheel covered with a buff on the surface of 
which rouge has been spread. 

Building Iron. — (See Appendix — Iron, 
Building.) 

Building Process for Moulds of Electro- 
types. — (See Append'x — Process, Build- 
ing, for Moulds of Electrotypes.) 

Buoy, Electrically Illumined A 

buoy illumined by means of an electric in- 
candescent lamp. 

The electric buoys are connected with the 
generating station on the shore by means of 
heavily armored cables. Spar buoys have 
been successfully lighted by such means. 

Burglar Alarm Contacts. — (See Appendix 
— Contacts, Burglar Alarm.) 

Burglar Alarm Matting. — (See Appendix 
— Matting, Burglar Alarm.) 

Burglar Alarm Trap. — (See Appendix — 
Trap, Burglar Alarm.) 

Burned-Out Incandescent Lamp. — (See 



Bur.] 



576 



[Cal. 



Appendix — Lamp, , Burned- Out Incan- 
descent.') - 

Burnishing. — A word employed in 
electro-plating for a process by means of 
which surfaces are prepared for electro- 
plating by subjecting them to the action of 
burnishing tools. 

The burnishing action consists essentially 
in smoothing and brightening a surface by 
crushing down the small inequalities of the 
surface. The burnishing action is not unlike 
the smoothing action of a hot iron in ironing. 

Button, Commutator-Press — A 



form of press button in which the current 
from a battery or other source is reversed 



in direction to the current previously flow- 
ing from the ordinary signalling button. 

Button, Push, Double-Contact A 

push button provided with two contacts. 

Button Repeater. — (See Appendix — Re- 
peater, Button.) 

Buzz. — A verb expressive of the action 
of an electric bell when it fails to strike dis- 
tinctly and only gives a sound something 
like that of a buzzer. 

An electric bell will "buzz" if the con- 
tacts are out of proper adjustment, or if the 
current passing is too strong. 

By-Pass of Discharge. — A term some- 
times employed for alternative path. (See 
Path, Alternative.) 



C. — A symbol used for capacity. 
The defining equation is C= ^ 

The same symbol is also used for current. 

C. — A symbol used for coulomb, the 
practical unit ol electric quantity. 

The same symbol is also used for current 
and proposed for capacity. 

cm. — An abbreviation frequently em- 
ployed for the centimetre, the C. G. S. unit 
of length. 

cm 2 . — An abbreviation frequently em- 
ployed for square centimetre, the C. G. S. 
unit of surface. 

cm 3 . — An abbreviation frequently em- 
ployed for cubic centimetre, the C. G. S. unit 
of volume. 

cm : s. — An abbreviation frequently em- 
ployed for centimetre per second, the C. G. 
S. unit of velocity. 

cm : s 2 . — An abbreviation frequently em- 
ployed for centimetre per second per sec- 
ond, the C. G. S. unit of acceleration. 

C- R Loss.— (See Appendix— Loss, C*R.) 



Cable, Concentric A cable pro- 
vided with both a leading out and a return 
conductor, one forming a central core or 
conductor and the other an enclosing 
tubular conductor, suitably insulated from 
each other. 

In a concentric cable the central conductor 
is heavily insulated and enclosed in a metallic 
tube which latter acts as a return conductor. 

Cable, Linear Capacity of The quo- 
tient of the capacity of a cable by its 
length. 

Cable, Linear Insulation of The 

product of the insulation resistance of a 
cable and its length. 

The linear insulation is preferably meas- 
ured in kilometre megohms, or mile 
megohms. 

Cage Protector for Lightning Discharges. 
— (See Appendix — Protector, Cage, for 
Lightning Discharges.) 

Callan Voltaic Cell. — (See Appendix — 
Cell, Voltaic, Callan?) 

Callan's Electro-Magnetic Repeater. — 
(See Appendix — Repeater, Electro-Mag- 
?ietic, Callan's.) 



Cal.] 



577 



[Cel. 



Calorimetry. — The science of measuring 
quantities of heat. (See Calorimeter.) 

Capacitance. — A term analogous to 
resistance, proposed by Hospitalier for the 
true or specific capacity of a medium. 

Capacity for Heat, 3Iean Thermal 

The mean thermal capacity for heat of a 
body between two stated temperatures is the 
quantity of heat required to raise it from 
the lower of these temperatures to the 
higher, divided by the difference of tem- 
peratures. (See Heat, Specific.) 



Casting", Electric 



-A process for 



Capacity, Kilometric, of Cable 



-The 



capacity of a cable in microfarads per kilo- 
metre. (See Cable, Electric.) 

Capacity, Magneto-Inductive — A 

term sometimes employed for magnetic per- 
meability. (See Permeability , Magnetic.) 

The word permeability is preferable. 

Capacity, Specific Dielectric — A 

term sometimes employed in place of 
specific inductive capacity. (See Capacity, 
Specific Inductive.) 

Carbon Arc. — (See Appendix — Arc, Car- 
bon.) 

Carbon Pencil.— (See Appendix — Pencil, 
Carbon.) 

Carbons, Skew Adjustment of, in Arc 
Lamp The adjustment of the car- 
bons of an arc lamp by means of which the 
positive carbon is placed a short distance 
in front of, back and out of a vertical line 
with, the negative carbon. 

The skew adjustment is employed in a 
projector or search light for the purpose of 
insuring the formation of the crater on the 
edge of the positive carbon so that the prin- 
cipal part of the light is thrown out hori- 
zontally. 

Cardan's Suspension of Compass Needle. — 

(See Appendix — Suspension of Compass 
Needle, Cardan 's,) 

Carrying Capacity of Safety Fuse. — (See 
Appendix — Fuse, Safely, Carrying 
Capacity of.) 



the casting of metals that have been fused 
by means of heat of electric origin. 

The metals are fused by heat in a specially 
provided furnace from which all the air has 
been exhausted. The fused metal is then 
run into moulds from which the air has also 
be£n exhausted. 

The vacuum and the electric melting, it is 
claimed, produce a greater liquidity of the 
metal than do the ordinary methods, and 
hence insure a readier flow and more sharply 
marked castings. The metal of the casting 
is also for the same reason extremely close 
and fine grained, and is free from blow-holes. 

Castor and Pollux Light. — (See Appen- 
dix — Light, Castor and Pollux.) 

Cataphoric Electrode. — (See Appendix — 
Electrode, Cataphoric.) 

Cataphoric Medication. — (See Appendix 
— Medication, Cataphoric.) 

Ceiling Block. — (See Appendix — Block, 
Ceiling.) 

Ceiling Kosette. — (See Appendix — 
Rosette, Ceiling.) 

Cell, Double-Liquid A term some- 
times employed in place of double-fluid 
cell. (See Cell, Voltaic, Double-Fluid.) 

Cell, Dry Gelatine A term applied 

to a type of dry voltaic cell in which the 
exciting liquid is absorbed by, or com- 
bined with, a variety of gelatinous sub- 
stances. 

The term gelatine dry cell is by no means 
limited to cases in which gelatine, either in 
whole or in part, forms the material for the 
retention of the exciting liquid. On the con- 
trary, such cells most frequently contain a 
mixture of various mineral substances which 
on standing assume a gelatinous or semi- 
gelatinous condition from the water com- 
bining with the substances. 

Cell, Earth A term frequently 

applied to a variety of cell consisting of 
any voltaic couple buried in a compara- 
tively moist stratum of earth. 



Cel.] 



578 



[Cel. 



In such cases the moisture of the earth 
acts as the electrolyte and the electromotive 
forces developed depend on the character of 
the voltaic couples employed. 

The term earth cell is sometimes improp- 
erly applied to the case of two similar metal- 
lic plates buried in the earth at considerable 
distances from one another. In such cases 
the current produced is obtain2d in part at 
least by means of the difference of potential 
caused between the two points of the earth 
at which the separate plates are located. 

It is evident, however, that the current 
produced by such earth cells, improperly so- 
called, is in reality obtained from the earth 
as an electric source, the plates with their 
metallic terminals simply forming conduct- 
ors for carrying off the current generated by 
the difference of potential already existing 
in the earth. (See Currents, Earth.) 

Cell, Galvanic A term sometimes 

employed instead of voltaic cell. (See 
Cell, Voltaic.) 

Cell, Gas A term sometimes ap- 
plied to one of the cells of a gas battery. 
(See Battery, Gas.) 

Cell, Lead Sulphate of Copper A 

form of storage cell in which two plates of 
lead are immersed in a solution of copper 
sulphate. 

On the passage of the charging current 
one lead plate becomes coated with lead 
peroxide and the other with metallic copper. 
(See Cell, Storage.) 

Cell, Lead Sulphate of Zinc A 

form of storage cell in which two plates oi 
lead are immersed in a solution of zinc 
sulphate. 

On the passage of the charging current 
one plate becomes coated with lead peroxide 
and the other with metallic zinc. 

This cell, according to Reynier, has an 
electromotive force of as high as from 2.8 
to 2.6 volts, but soon falls to from 2.3 to 2 
volts. (See Cell, Storage.) 

Cell, Light A term sometimes 

employed for a photo-electric cell. (See 
Cell, Photo-Electric.) 



Radiant energy, whether of the luminous 
type, as in the case of light, or of the non- 
luminous type, as in the case of heat, pro- 
duces a difference of potential under a variety 
of circumstances. 

In some cases violet-colored light seems to 
produce the most marked effects. 

Roughly speaking, photo-electric, or light 
cells, can be grouped into two fairly sharply 
marked classes, namely: 

(1.) Those in which the electricity accom- 
panies some chemical decomposition which 
acts to produce a current. 

(2.) Those in which slight molecular 
changes occur which result in the production 
of an electric current. 

The production of electricity in cells of the 
latter type, by the action of light alone, is 
probably analogous to the production of 
pyro-electricity in the case of certain crys- 
talline bodies. (See Electricity, Pyro.) 

Cell, Magneto-Chemical A cell in- 
vented by Balsamo, in which two similarly 
magnetized bars are immersed with the 
north pole of one and the south pole of the 
other in a solution of oxalic acid. 

Under these circumstances the magnet 
having its north pole immersed in the ex- 
citing liquid acts like the zinc plate, and the 
one having its south pole like the copper of 
an ordinary zinc-copper couple immersed in 
dilute sulphuric acid. 

The influence a magnetic fluid exerts on 
chemical action has been investigated by 
Rowland and Bell, and by Squier. (See 
Appendix — Action, Protective. Throw, Pro- 
tective. Throw, Concentration.) 

Cell, Photo-Electric Impulsion A 



term sometimes applied to an impulsion 
cell. (See Cell, Impulsion.) 

Cell, Primary A term sometimes 

employed for a voltaic cell. (See Cell, Vol- 
taic?) 

The term primary cell is employed in con- 
tradistinction to secondary or storage cell. 
(See Cell, Storage.) 

Cell, Regenerative A term pro- 
posed for an early form of storage or sec- 



€el.] 



579 



[Cha, 



ondary cell, invented by Thomson and 
Houston, consisting of two plates of cop- 
per immersed in a solution of zinc sul- 
phate. 

Two plates were placed, one at the bottom 
of the solution, and the other near the top. 
On the passage of the charging current, 
one of the plates through the decomposition 
of the zinc sulphate was partially con- 
verted into copper sulphate and the other 
plate was coated with metallic zinc. The con- 
nections were such that the plate partially- 
converted into zinc sulphate was placed at 
the bottom of the cell, and the one partially 
converted into and covered by metallic zinc, 
at the top. 

The passage of the charging current thus 
produced a variety of gravity cell. On the 
exhaustion of the cell there remained two in- 
ert plates of copper immersed in a solution 
of zinc sulphate. 

Cell, Thermo-Cliemical A variety 

of heat cell in which a difference of po- 
tential is produced and maintained between 
two plates immersed in a suitable liquid 
when one plate is kept at a higher tem- 
perature than the other. 

A heat cell forms in reality a species of 
storage battery in which the charging of the 
cell is obtained by the expenditure of heat 
energy. 

In true heat cells a chemical action occurs 
which is readily and completely reversible 
by heat. 

Cell, Voltaic, Agglomerate Leclanche 

A variety of Leclanche cell in 

which the mixture of carbon and dioxide of 
manganese is made into a solid mass by 
pressure. 

The advantage claimed for the agglomer- 
ate Leclanche cell is that the porous cup em- 
ployed in the other forms of this cell is dis- 
pensed with. 

Cell, Voltaic, Callan A zinc-iron 

couple, the elements of which are immersed 
respectively in an electrolyte of dilute sul- 
phuric acid, and an electrolyte consisting 



of a mixture of strong nitric and sulphuric 
acids. 

In the Callan cell the iron plays the part of 
the negative element. It is not attacked by 
the nitric acid provided the acid be suffi- 
ciently strong. The reasons generally as- 
signed for the non-action of the acid on the 
iron are either the so-called passive state 
of the iron or the formation on the surface 
of an insoluble oxide. (See State, Passive.) 

This cell is sometimes called the iron cell, 
or the Maynooth. It is difficult to maintain 
this cell in good action, owing to the liability 
of the nitric acid to act on the iron when- 
ever its strength falls below a certain point. 

Cell, Voltaic, Heat A cell in which 

heat energy is changed or converted into 
electric energy. 

Park Benjamin divides heat cells into three 
classes, namely: 

(i.) Those in which heat acts upon the 
materials of the cell by causing fusion or de- 
composition. 

(2.) Those in which heat acts to set free 
chemical affinities whereby the cell is caused 
to operate, regeneration after exhaustion 
taking place at a lower temperature. 

(3) Thermo-chemical cells, or those in 
which the difference of potential is maintained 
between two plates immersed in a liquid by 
heating one plate to a higher temperature 
than the other. 



Cell, Voltaic, Maynooth 



■A name 



sometimes given to the Callan voltaic cell. 
(See Appendix — Cell, Voltaic, Callan.) 

Cell, Voltaic, Single-Liquid A term 

sometimes employed in place of a single- 
fluid cell. (See Cell, Voltaic, Single- 
Fluid.) 

Cessation of Current. — (See Appendix — 
Curre?it, Cessation of.) 

Chain, Bead A chain employed in 

connection with a pendant electric burner. 
(See Burner, Plain Pendant Electric.) 

Chain, Galvanic A term lormerly 

applied to a galvanic, or more properly 



Cha.] 



580 



[Chr. 



speaking-, voltaic circuit. (See Circuit, 
Voltaic.) 

Chamber of Incandescent Electric Lamp, 
Age-Coating of The gradual darken- 
ing of the enclosing glass chamber of an 
incandescent electric lamp. 

This coating may be due to a deposit of 
carbon or a hydrocarbon, or a deposit of metal 
deflagrated or volatilized by the heat of the 
filament. 

Charge Accumulator. — (See Appendix — 
Accumulator, Charge.) 

Charge Current on Telegraphic Line. — 
(See Appendix — Line, Telegraphic, Charge 
Current on.) 

Charge, Linear Density of The 

amount of electricity per unit of length of 
conductor. (See Charge, Electric.) 

Charge, Minus A negative charge. 

(See Charge, Negative.) 

Charge, Plus A positive charge. 

(See Charge, Positive.) 

Charge, Sweeping-Out A phrase 

employed in double-current signalling for 
the freeing of the line from a charge pro- 
duced by the sending of one signal, by re- 
versing the direction of the current through 
the line. 

The "sweeping-out" of the charge on a 
telegraphic line decreases the amount of re- 
tardation. (See Retardation.) 

Charge, Volume Density of The 

amount of electricity per unit of volume. 

(See Charge, Electric.) 



Check, Telephone Time 



-A device 



by means of which, in a telephone ex- 
change system, a drop shutter is automati- 
cally released at a particular trunk wire 
indicator, at the beginning of the time that 
a subscriber is given the use of the trunk 
line, and automatically disconnected, and 
the central station operator's attention is 
called to the fact of such disconnection. 
By the use of the time-check, disputes as 



to the length of time a subscriber is given 
the use of a trunk line is avoided. 

A telephone time-check is sometimes 
called a telephone meter. (See Appendix — 

Meter, Telephonic.) 

Chemical Generator of Electricity. — (See 
Appendix — Generator, Chemical, of Elec- 
tricity.) 

Chemical Telegraph. — (See Appendix — 
Telegraph, Chemical.) 

Chemism. — A word sometimes em- 
ployed for chemical affinity. (See Affinity, 
Chemical.) 

Chemistry, Thermo That branch 

of chemistry which treats of the measure- 
ment of chemical energy in thermal units. 

According to Berthelot : 

(i.) The amount of heat set free in any 
chemical reaction is a measure of the total 
work done during that reaction. 

(2.) Changes produced in any system not 
attended by external effects produce an evolu- 
tion of heat dependent only on the initial and 
final states of the system. 

(3.) Every chemical change effected in a 
system independent of external energy tends 
to produce that body or system of, bodies, 
the formation of which evolves a maximum 
heat. 

Choke Magnet. — (See Appendix — Mag- 
net, Choke.) 

Chronograph, Spark A form of 

electric chronograph in which the time of a 
certain event is indicated by means of the 
spark of a Ruhmkorff or spark coil. 

In a form of spark chronograph for meas- 
uring the time in which a falling body moves 
through different parts of its path, the path 
of the body is marked on a moving sheet of 
paper by means of a series of sparks from a 
Ruhmkorff coil. 

Chronometer, Electric — 



An elec- 
trically controlled or operated mechanism 
for indicating or recording time. (See 
Clock, Electric^ 



Cir.] 



581 



[CIo. 



Circuit Closer. — (See Appendix — Closer, 
Circuit.) 

Circuit Closer for Pull Bell.— (See Ap- 
pendix — Pull Bell, Circuit Closer for.) 

Circuit, Consumption A circuit in 

which the energy of the electric current is 
consumed or utilized for energizing electro- 
receptive devices. 

Electric energy is consumed in all parts of 
an electric circuit. The term consumption 
circuit, however, is limited to that part of an 
electric circuit in which the electro-receptive 
devices are placed which are energized by 
the passage of the electric current through 
them. 

Circuit, Electrical Timing of (See 

Appendix — Tuning of Electrical Circuit.) 
Circuit, Magnetic, External A 

term sometimes employed for that part of 
a magnetic circuit which lies outside of a 
magnet. (See Circuit, Magnetic.) 

Circuit, Magnetic, Internal A 

term sometimes employed for that part of a 
magnetic circuit which lies within the mag- 
net. (See Circuit, Magnetic.) 

Circuit, Multiple-Parallel A term 

sometimes employed for a multiple of 
parallel circuits. (See Circuit, Multiple.) 

Circuit, Parallel- Arc — A term 

sometimes employed in place of parallel or 
multiple circuit. (See Circuit, Multiple.) 

Circuit, Eesonant A circuit whose 

dimensions are such as to bring it into res- 
onance with, or to tune it to, the period ol 
another circuit. 

Circuit, Surging An electrical 

circuit through which electrical surgings 
are passing. 

Lodge employs this term, surging circuit, 
in the following restricted sense. 

" I have been accustomed especially to 
apply the name ' surging circuit ' to the case 
where sparks are obtained not between two 
distinct parts of a circuit, but between two 
points on one and the same good conductor, 



under circumstances when it does not form 
the alternative path to anywhere, and when 
it would ordinarily be supposed that there 
was no possible reason for a spark at all." 

The term surging circuit is applied gen- 
erally to circuits through which surging dis- 
charges are passing; as, for example, the 
condenser-motor circuit in the Stanley-Kelley 
system. 

Circuit, Telegraphic, Working Efficiency 

of The variation or margin between 

the joint resistance of the conductor and the 
resistance of the insulator by which the con- 
ductor is supported. 

According to F. L. Pope the working effi- 
ciency may be increased in two ways, viz.: 

(i.) By increasing the insulation resist- 
ance. 

(2.) By decreasing the resistance of the 
conductor. 

Circular Magnetization. — (See Appendix 
— Mag n etiza Hon , Circu lar.) 

Clamp, Feeder Any clamping de- 
vice for connecting or fastening a feeder 
wire to a trolley wire. 

Clip. — A slight break in the signal re- 
ceived in a system of duplex telegraphy 
under certain circumstances. 

Clip, Feeder In a system of elec- 
tric street railways a clamp furnished with 
a device whereby a feeder wire may be 
readily connected to a trolley wire. 

Clips, Stay-Eye — Iron bands 

clamped to the string beams of the roof 
with an iron ring projecting from the sur- 
face of the roof, to which the stay rods of 
telegraphic or telephonic standards are 
screwed. 

Clock, Directing A term some- 
times employed instead of controlling or 
master clock. (See Clock, Electrical- 
Controlling.) 

Clock, Electric, Watchman's A 

watchman's electric register. (See Regis- 
ter, Watchman 's, Electric.) 



Clo.] 



582 



[Com. 



Clock, Primary Electric 



A term 

sometimes employed in place of the con- 
trolling or master clock. (See Clock, 
Master.} 

Clock, Standard — In a system of 

time telegraphy the master clock. (See 
Clock, Master.) 

Closed-Circuit Transformer. — (See Ap- 
pendix — Transformer, Closed- Circuit.) 

Closed-Conducting- Sheath for Lightning 
Protection. — (See Appendix — Sheath, 
Closed-Conducting, for Lightning Protec- 
tion.) 

Closer, Circuit Any device for 

completing or closing a circuit. 

Clown's-Hat Curve. — (See Appendix — 
Curve, Clown's-Hat.) 

Code, American Morse A term 

sometimes employed for the Morse tele- 
graphic alphabet. (See Alphabet: Tele- 
graphic, Morse's.) 

Code, Dot-and-Dash A term some- 
times employed for the Morse telegraphic 
code. (See Code, Telegraphic.) 

Code, International Morse A 

term sometimes employed for the interna- 
tional telegraphic alphabet. (See Alpha- 
bet, Telegraphic: International Code.) 



Coil, Faradic 



— A term sometimes 



employed in place of a Faradic machine or 
medical induction coil. (See Machine, 
Faradic.) 

Coil, Ground A small rheostat 

employed in duplex telegraphy at the home 
station for the purpose of giving the appara- 
tus in such station an equal resistance to 
the currents coming from the distant sta- 
tion. (Pope.) 

The resistance of the ground coil should 
be equal to the resistance of the spark coil, 
plus the internal resistance of the battery. 



Coil, Induction Ribbon 



-An induc- 



cuits of which are made of metallic ribbons 

instead of wires. 

Coil, Induction, Self A coil of wire 

possessing a self induction. 

A choking coil. (See Coil, Choking.) 
Coil, Spark, Telegraphic A small 

rheostat employed in duplex telegraphy at 

the home station in connection with the 

ground coil. (See Appendix — Coil, 

Ground.) 

The resistance of the spark coil should 
be made sufficiently great to prevent the po- 
larization of the battery when it is momenta- 
rily short-circuited. 

Coils, Differential Coils that are 

differentially wound. (See Appendix — 
Winding, Differe7itial^ 

Coils, Field, of Dynamo The coils 

of wire wound on the held magnet cores 
for the production of the magnetic field. 

Coked Core of Incandescent Filament. — 

(See Appendix — Core, Coked, of Incandes- 
cent Filament,) 

Coked Filament. — (See Appendix — Fila- 
ment, Coked.) 

Coking, Electrical Subjecting a 

carbon to the coking process. (See Ap- 
pendix — Process, Coking, for Filament of 
Incandescent Electric Lamp.) 

Coking of Filament. — (See Appendix — 
Filament, Coking of.) 

Coking Process for Filament of Incandes- 
cent Electric Lamp. — (See Appendix — Iroc- 
ess, Coking, for Filament of Incandescent 
Electric Lamp.) 

Collecting Combs. — (See Appendix — 
Combs, Collecting.) 

Comazant. — A term formerly applied to 
St. Elmo's fire. 

A corposant. (See Corposant. Fire, 
St. Elmo's.) 

Combination Fittings for Chandeliers, 



tion coil, the primary and secondary cir- Brackets, etc. — (See Appendix — Fittings, 



Com.] 



583 



[Con. 



Combination, for Chandeliers, Brackets, 
etc.) 

Combs, Collecting A term some- 
times employed for the collecting points of 
a frictional electrical machine, or of an 
electrostatic induction machine. (See Ma- 
chine, Frictional Electric. Machine, 
Electrostatic Induction.) 

Common Arc of Aurora Glory. — (See Ap- 
pendix — Arc, Common, of Aurora Glory.) 

Commutator Press-Button. — (See Ap- 
pendix — Button, Commutator-Fress.) 

Commutatorless. — Not provided with a 
commutator. (See Commutator ; Dynamo- 
Electric Machine.) 

Compass, Declination — A decli- 
nometer. (See Declinometer.) 

Compensated Alternator. — (See Appen- 
dix — Alternator, Compensated.) 

Compensating- Alternating' Dynamo-Elec- 
tric Machine. — (See Appendix — Machine, 
Dynamo - Electric, Compensating- Alter- 
nating.) 

Compensator, Magnetic A device 

for neutralizing the effects produced on a 
magnetic needle by the local magnetism of 
a ship. 

Complex-Harmonic Alternating Electro- 
motive Forces. — (See Appendix — Forces, 
Electromotive, Complex-Harmonic Alter- 
nating.) 

Complex-Harmonic Currents. — (See Ap- 
pendix — Currents, Complex-Harmonic.) 

Complex-Magnetic Shell. — (See Appen- 
dix — Shell, Complex-Magnetic .) 

Compound Alternator. — (See Appendix — 
Alternator, Compound.) 

Compound Battery. — (See Appendix — 
Battery, Compound.) 

Compound Electro-Magnet. — A term 
sometimes applied to an induction coil. 
(See Appendix — Magnet, Electro-Com- 
pound.) 



Compound .Magnet. — (See Appendix — 
Magnet, Compound.) 

Concentration Throw. — (See Appendix — 
Throw, Concentration.) 

Concentric Cable. — (See Appendix — 
Cable, Concentric.) 

Concentric Wiring. — (See Appendix — 
Wiring, Concentric.) 

Conductance, Specific Specific 

conductivity. (See Conductivity, Specific.) 

Conductibility. — Possessing the power of 
conducting electricity. 

Conductivity. 

Conducting Cord and Tip. — (See Appen- 
dix — Cord and Tip, Conducting.) 

Conducting Cord Tip. — (See Appendix — 
Tip, Conducting Cord,) 

Conduction Lightning Protection.— (See 
Appendix — Protection, Conduction Light- 
ning.) 

Conduction Lightning Protector. — (See 
Appendix — Protector, Conduction Light- 
ning^ 

Conduction, Metallic — A term 

sometimes employed for the conduction of 
electricity through a solid conductor in con- 
tradistinction to its conduction through an 
electrolyte. (See Co?iduction, Electrolytic.) 

Conduction Resistance. — (See Appendix 
— Resistance, Conduction.) 

Conductivity, Percentage, of Wire 

— The conductivity of a particular copper 
wire compared with the conductivity of 
another wire of the same dimensions of pure 
material at a standard temperature. 

The percentage conductivity is readily ob- 
tained by multiplying the calculated resist- 
ance of the pure material by ioo and dividing 
the result by the measured resistance of the 
particular wire. 

Conductor, Electric, Glowing of 

Emitting light from any conductor heated 
to electrical incandescence. 



Con.] 



584 



[Con. 



The current strength required to produce 
a glow in a conductor varies in a marked 
manner with the character and density of 
the gas surrounding the conductor. 

Conductor, Electric, Melting' of 

Fusion of a conductor by means of the heat 
of electric currents. 

The strength of current required to fuse 
or melt a conductor varies with a number of 
circumstances, so that a wire which will not 
fuse under the influence of a certain current 
strength may fuse at another time under a 
much smaller current strength if the con- 
ditions are different. Among these influences 
may be mentioned the nature of the medium 
surrounding the conductor, as well as the 
temperature of said medium. Sometimes, 
too, a coating of oxide forms on the surface 
of the conductor, which modifies its ability 
to throw off or radiate its heat. 

When subjected to alternating currents a 
fuse wire has its fusing point gradually 
lowered. 

Conductor, Electric, Volatilization of 

— The volatilization of a conductor pro- 
duced by the passage of an electric current 
through it. 

The current required to volatilize a con- 
ductor will necessarily vary with the same 
circumstances that modify its electric glow- 
ing or melting. (See Appendix — Conductor , 
Electric, Glowing of. Conductor, Electric, 
Melting of.) 

Conductor or Line Wire, Dip of 

The sag of a telegraphic or telephonic wire 
or conductor between two supports due to 
its weight. 

Conductor Resistance, — (See Appendix — 
Resistance, Conductor.) 

Conductor, Semi A term some- 
times applied to substances, such as acids, 
saline salts, water, etc., whose power of 
conduction for electricity is neither very 
high nor very low. 

Substances that occupy an intermediate 
position between conductors and so-called 
non-conductors for electricity. 



Conductor, Stranding of Forming 

a conductor of several smaller conductors 
for the purpose of reducing the self-induc- 
tion or eddy currents, or of increasing its 
flexibility. (See Induction, Self.) 

Conductor System for Railroad. — (See 
Appendix — Railroad, Conductor System 
for.) 

Conflict, Electric A term proposed 

by Oersted for a magnetic field surround- 
ing a conductor through which a current 
of electricity is flowing. 

Oersted speaks as follows of his discovery 
of the magnetic qualities of the region around 
a conductor through which an electrical cur- 
rent is flowing : " That this conflict performs 
circles around the wire, for without this con- 
dition it seems impossible that one part of 
the wire when placed below the magnetic 
needle shall drive its pole to the east, and 
when placed above it to the west." 

Connector, Copper A particular 

form of connector employed in the gravity 
voltaic cell for connecting the copper ele- 
ment to the circuit wire or conductor. 

A name applied technical'y to a form of 
electric light fitting or coupler for connect- 
ing large wires or conductors. 

Consonance. — Literally, sounding at the 
same time,. 

Strictly speaking, two sounds are said to 
be in consonance when they are sounded to- 
gether. In this sense we speak of pleasing 
consonances or harmonious chords. Often, 
however, the word consonance is used in 
contradistinction to dissonance as indicating 
two sounds that are in unison with each 
other. 

The word consonance is also frequently 
employed in the sense of increasing or re- 
enforcing a sound; such, for example, as the 
method of increasing the sound produced by 
a vibrating string or cord by stretching the 
cord over an elastic body like a table. In 
such cases the table takes up the motions or 
vibrations of the cord, and, by thus setting in 
motion a greater mass of air, increases the 



Con.] 



585 



[Con, 



amplitude of the waves and consequently 
the intensity of the sound. This use of the 
word consonance is to be distinguished from 
resonance, in which an increase in the inten- 
sity of the sound is also produced by waves 
or vibrations set up in another body with, 
however, this difference : in the case of reso- 
nance the re-enforcement is effected by vibra- 
tions set up in a body that is tuned to vibrate 
in exact unison with a vibrating body; while 
in the case of consonance no such tuning is 
necessary ; or, briefly, consonant vibration is 
forced vibration, while resonant vibration is 
natural or free vibration excited by the 
vibrating body. 

Consonator. — Any body possessing the 
power of increasing the strength of sound 
by consonance. (See Appendix — Con- 
sonance.) 

This use of the word consonator is analo 
gous to the use of the word resonator; viz., 
a body having the power of increasing the 
strength of sound by resonance. (See Reso- 
nator.) A consonator, however, differs from 
a resonator in the manner in which it 
strengthens the sound. 

Constant-Potential Motor. — (See Appen- 
dix — Motor, Constant-Potential.) 

Constant, Verdet's — The mag- 
neto-optic constant of a transparent sub- 
stance, usualiy expressed in minutes of arc 
rotation of the plane of polarization, for a 
luminous ray of definite wave length through 
the magnetized substance at a definite 
temperature between points on the ray 
path whose magnetic potential differs by 
unity. 

Verdet's constant is usually taken for the 
D line at the temperature of I5°C. Its value 
for monohydrated sulphuric acid according 
to Bichat, and Mascart and Joubert equals 
0.0104 '■ 

Consumption Circuit. — (See Appendix — 
Circuit, Consumption?) 

Contact Breaker. — (See Appendix — 
Breaker, Contact.) 

Contact, Drop Relay A form of 



relay contact in which the attraction of 
an armature on the passage of a current 
releases a drop and thus completes a local 
circuit which remains closed until the drop 
is replaced or reset. 

By the suitable combination of a drop re- 
lay and a bell, the bell may become a con- 
tinuous ringing bell. 

Contact, Floor A term sometimes 

employed in place of floor push. (See 
Push, Floor.) 

Contact, Full A variety of fault 

produced by a part of the circuit being 
accidentally placed in contact with a good 
metallic circuit. (See Contacts.) 

Contact, Relay A term frequently 

applied to a form of electro-magnetic in- 
strument by means of which a local circuit 
is completed by the passage of a current. 

A relay contact is in reality a form of key 
or push, which, instead of being opened or 
closed by means of the hand, is closed by 
means of an electro-magnet. Relay contacts 
are of two kinds, namely, spring relay con- 
tacts and drop relav contacts. 

Contact Resistance. — (See Appendix — 
Resistance, Contact.) 

Contact, Spring Relay A form of 

relay contact which is interrupted by the 
action of a spring, as soon as the current 
is broken. 

Contact Theory of Electricity. — (See 
Appendix — Theory t Contact, of Elec- 
tricity.) 



Contact, Total 



■A term sometimes 



employed for full metallic contact. (See 
Contact, Full-Metallic.) 

Contact, Window or Blind A 

variety of burglar-alarm contact by means 
of which an alarm bell is rung by a slight 
pressure against a blind caused by any at- 
tempt to enter from without after having 
broken the glass in the window. (See 
Alarm, Burglar.) 



Con.] 



586 



[Cor. 



Contacts, Burglar Alarm — Con- 
tacts by means of which the opening or 
closing of a. door or window, or the passage 
of a person across a given space, is caused 
to ring an alarm bell. (See Alarm, Burglar.') 

Continuous Action of Electric Bell. — (See 
Appendix — Bell, Electric, Continuous Ac- 
tio 71 of.) 

Continuous Current Arc. — (See Appendix 
— Arc, Continuous Current.) 

Continuous Current Transformer. — (See 
Appendix — Transformer, Continuous Cur- 
rent.) 

Contracting Magnetic Whirl. — (See Ap- 
pendix — Whirl, Contracting Magnetic?) 

Contraction, Over-Maximal An in- 
crease in the electrical stimulation of a 
motor nerve beyond the point where an 
apparent maximum stimulus has been 
reached. 

Between the condition of the first maxi- 
mum and the second maximum an increase 
in the strength of the current is followed by 
a decrease in the stimulation. On, how- 
ever, a further increase in the current 
strength a second increase in the contrac- 
tion, termed the over-maximal contraction, 
occurs. 

Contraplex Telegraph. — (See Appendix — 
Telegrap h, Con trap lex . ) 

Convection Transference. — (See Appen- 
dix — Transference, Convection.) 

Conversion of Electromotive Force. — 
(See Appendix — Force, Electromotive, 
Conversion of,) 

Conversion, Ratio of A term some- 
times employed instead of ratio of trans- 
formation. (See Appendix — Transforma- 
tion, Ratio of.) 

Convert. — To transform or change. 

Converter, Rotary A rotary trans- 
former. (See Appendix — Transformer, 
Rotary.) 

Converting. — Transforming or changing. 



Co-phasal. — Two or more quantities 
which vary harmonically, and whose rates 
of increase or decrease at any given time 
maintain a constant ratio. 

Co-phasal Alternations. — (See Appendix 
— -Alternatio7is, Co-phasal.) 

Copper Arc. — (See Appendix — Arc, Cop- 
per.) 

Copper Connector. — (See Appendix — 
Connector, Copper.) 

Copper-Lead Accumulator. — (See Appen- 
dix — Accumulator, Copper-Lead.) 

Copper Resistance. — (See Appendix — 
Resistance, Copper.) 

Copper Shell of Electrotype. — (See Ap- 
pendix — Shell, Copper, of Electrotype.) 

Copper-Zinc Accumulator. — (See Appen- 
dix — Accumulator, Copper-ZUic.) 

Cord and Tip, Conducting — A con- 
ducting cord provided at one of its ends 
with a tip for the purpose of ready inser- 
tion in a wall socket. 

Cord, Incandescent Lamp A flex- 
ible lamp cord of two strands suitable for 
use with a pendent incandescent lamp. 

Core, Coked, of Incandescent Filament 
A filament for an incandescent elec- 
tric lamp, formed of a core of electrically 
coked carbon, whose surface is covered 
with a deposit of carbon derived from the 
electrical decomposition of a hydrocarbon 
gas or vapor. 

Core Loss of Transformer. — (See Appen- 
dix — Loss, Core, of Transformer.) 

Core Pins of Magnet. — (See Appendix — 
Pins, Core, of Magnet.) 

Cores, Krizik's Cores for magnetic 

solenoids shaped so as to insure an ap- 
proximately uniform pull in different posi- 
tions in the solenoid. (See Bars, Krizik's.) 

Coreless Armature of Dynamo or Motor. 
— (See Appendix — Armature, Coreless, of 
Dynaino or Motor.) 



Cor.] 



587 



[Cor. 



Corona, Electrostatic — A luminous 

effect produced on the surface of a thin 
sheet of mica, or other similar insulating 
material, when placed between two elec- 
trodes between which discharges of com- 
paratively high difference of potential are 
passing. 

Steinmetz describes the phenomena of the 
electrostatic aurora and corona in the Elec- 
trical Engineer for April 5, 1893, as follows : 
"Very interesting luminous effects take 
place when a thin sheet of good insulating 
material, as mica, is placed between the elec- 
trodes. At a difference of potential of 830 
volts and a thickness of mica of 1.8 milli- 
centimetres, in darkness a faint bluish 
glow becomes visible between the mica 
and the electrodes. This glow is very- 
perceptible at 970 volts, and faintly visi- 
ble in broad daylight at 1,560 volts. With 
increasing difference of potential, this bluish 
glow increases in intensity, forming a sharply 
defined, smooth blue line around the elec- 
trodes at their point of contact with the 
mica. 

" At a difference of potential of 4.5 kilo- 
volts — thickness of mica of 2.3 milli-centi- 
metres — violet creepers of about two mm. 
length break here and there out of the line 
of bluish glow. These creepers are distinctly 
different from the blue glow surrounding the 
electrodes and increasein number and length 
with increasing potential, until they form a 
broad electrostatic aurora surrounding the 
electrodes on either surface of the mica 
sheet, consisting of an infinite number of 
small violet streamers, rushing with a hiss- 
ing noise over the mica. This corona in- 
creases rapidly in width until it reaches the 
edges of the mica sheet. Then white sparks 
of intense brightness pass from electrode to 
electrode over the surface of the mica, first 
few in number, then with increasing poten- 
tial, covering the whole sheet with an in- 
finite number of streaks of lightning with a 
roaring noise. The amount of current pass- 
ing through these sparks is exceedingly 
small, for no perceptible reaction upon the 
primary circuit was noticed. The length of 
these sparks is many times larger than the 



sparking distance in air, being tenfold at 17 
kilovolts. They are intensely hot, and leave 
whitish marks, due to calcination, on the 
mica when passing over it. The sheet of 
mica, and especially the electrodes, become 
heated very rapidly, the mica twists and be- 
gins to splinter, to separate into sheets, untiL 
finally it breaks down. 

"The width of the electrostatic corona is" 
half the length of these sparks. The length of 
these sparks depends somewhat upon fre- 
quency and the thickness of the mica sheet, 
being greater for higher frequency and thin- 
ner mica disc, but apparently only in so far 
as the capacity, or rather the charging cur- 
rent of the condenser, represented by the 
mica disc as dielectric, is increased there- 
by." 

Corrosion, Electrolytic A terra 

frequently employed for the corrosion of. 
water or gas pipes or other masses ot 
metal buried in the earth by electrolytic 
action. 

In the case of such large currents as those- 
employed in the electric railway car systems,, 
or other similar earth-connected circuits, the; r 
corrosion may become marked. In such cases, 
electrolytic corrosion is due to the return, 
current. 

The amount of corrosion varies according 
to whether the railroad tracks are made the 
positive or negative terminal of the driving 
source. 

It is claimed by some that electrolytic cor- 
rosion is lessened by connecting the trolley 
line to the negative terminal of the battery 
and the tracks to the positive terminal. 

Perrine describes this matter as follows : 

"A more complete system of ground- 
ing seems, however, to offer at least a par- 
tial solution of this difficulty, which may 
only be completely worked out in a careful 
study of the special conditions in some par- 
ticular case. 

" For such a complete system of ground- 
ing, in order to reduce to a minimum elec- 
trolytic corrosion, the negative pole of the 
dynamo should be connected to the trolley 
and feeder line ; then at the station connec- 
tions should be made not only with the rails, 



Cos. 



588 



[Cou. 



and wells, but also with all water and gas 
pipes, which piping system should also be 
frequently connected to the track and track 
feeder, so that whatever current passes by 
the medium of these pipes should flow out of 
the earth into them, and thence to the rails 
by means of metallic and not electrolytic 
conduction. If this be completely accom- 
plished there can be no corrosion of the pipes 
caused by the current flowing out of the 
pipes to the rails, and the only corrosion 
possible will be that due to the local action 
caused by the difference of potential along 
the pipes themselves." 

It would appear that the total corrosion of 
pipes that are not in metallic connection with 
the circuit is independent of the polarity of 
the terminal, since the same amount of cur- 
rent which enters the pipe f r om the ground 
must leave it by again passing to ground. 
In this manner the area of entrance into the 
pipe is protected and its area of exit cor- 
roded electrolytically. By changing the 
terminals the protected and corroded parts 
are merely interchanged. 

By making the shunt current passing 
through the pipes leave the pipes by means 
of a metallic conductor instead of by the 
ground, the entire system of pipes is brought 
below the potential of the ground and a pro- 
tection or partial protection is thus effected. 

Experiments made on the West End Rail- 
road of Boston and elsewhere, appear to 
show that it makes but little difference which 
terminal is connected to earth. It is by 
many considered best to alternately connect 
the positive and negative terminals to earth 
for a period of a week at a time and not to 
depend on the earth for a return, or make 
use of a supplemental wire, but to double- 
bond the rails with heavy copper wire, plac- 
ing the connections back i\ to 3 feet respect- 
ively from the end of the rails to avoid the 
motion of the joint. With a Tail 70 pounds 
to the yard, on a four track road, this is 
equivalent to about 28 inches cross-section of 
steel, the carrying capacity of which is 4^ 
square inches of copper. If, therefore, an 
equally good connection is made from the rails 
to the generator at the power station, there is 
thus provided a path capable of carrying 



10,000 amperes without undue heating. Rails 
bonded in this manner and used as returns, 
will avoid the variable resistance of the earth 
arising from dry weather, poor contact with 
earth, frost, etc., and will consequently avoid 
electrolytic corrosion in neighboring pipes. 

Cosine Law of Illumination. — (See Ap- 
pendix — Illumination, Cosine Law of.) 

Coulomb, International The value 

of the international coulomb adopted bythe 
Chicago Congress of 1893, as equal to the 
quantity of electricity transferred by a cur- 
rent of one international ampere in one 
second. 

Coulomb Meter. — (See Appendix — Meter, 
Coulomb.') 

Coulomb's Electric Balance. — (See Ap- 
pendix — Balance, Coulomb's Electric.) 
Coulomb's Magnetic Torsion Balance. — 

(See Appendix — Balance, Coulomb's Mag- 
netic Torsion.) 
Counter, Electro- Clironometric 

An apparatus employed in a system of elec- 
trical clocks to so transmit the motion 
of an ordinary clock to a number of sepa- 
rate clocks as to control or operate them. 

Electro-chronometric counters consist es- 
sentially of two parts, namely, 

(1.) The indicator or apparatus connected 
with the regulating clock and operating to 
periodically make and break the current of a 
battery. 

(2.) The mechanism that moves the clock 
hands when actuated by the current sent into 
the line by the indicator. 

Counter-Electromotive Force of Elec- 
trolysis. — (See Appendix — Electrolysis, 
Counter-Electromotive Force of.) 

Couple, Molecular Voltaic A vol- 
taic couple formed of the atoms or radicals 
of a molecule. 

Lermantoff has shown that during the 
development of the photographic image in 
moist collodion a true electrolysis occurs, 
each silver molecule produced by the action 
of the light on the sensitized plate forming a 



€ra.] 



voltaic couple with a molecule of silver 
nitrate and a molecule of iron sulphate of a 
developer. 

Crater of Arc. — A crater formed in 
the end of the positive carbon electrode in 
a carbon voltaic arc. (See Arc, Voltaic.} 

Creeping" of Belt. — (See Appendix — Belt, 
Creeping of.) 

Cross-Fire. — A term employed in teleg- 
raphy for an escape or leakage of current 
from one telegraphic line to another, due to 
defective insulation. 

A cross-fire is sometimes called a weather 
cross. (See Cross, Weather.} 

Cross-Induction of Dynamo Armature. — 

(See Appendix — Induction, Cross, of 
Dynamo Armature.) 

Cross, Metallic A form of fault 

attended by a leakage or escape of current 
from a telegraphic line due to the absolute 
contact between two or more wires or con- 
ductors, so that part of the current from 
one line passes to the other. 

Cross-Over, Trolley In a system 

of electric street railways a device permit- 
ting the ready passage of a trolley wheel in 
a continuous direction from one to another 
of two adjacent wires. 

Cross, Peltier's A cross made by 

placing two plates of dissimilar metals in 
contact at right angles to each other, and 
employed for the study of the Peltier effect. 
(See Effect, Peltier.) 

Crossing- Frog". — A term sometimes em- 
ployed in place of trolley cross-over. 

Crystal, Pyro-Electric Any crys- 
talline substance capable of producing 
pyro-electric phenomena on being unequally 
heated. 

Tourmaline, electric calamine, boracite, 
quartz, tartrate of potash, and sulphate of 
quinine are examples of pyro-electric crys- 
tals. 



589 [Car. 

Cubic Energy.— (See Appendix— Energy, 

Cubic.) 

Cup Brush.— (See Appendix— Brush, 

Cup.) 

Current Accumulator. — (See Appendix — 
Accumulator, Current?) 

Current, Arriving, of Telegraphic Circuit 

A term employed to designate the 

current on a telegraphic line or conductor 
near the distant end of the wire close to 
where it enters the ground or earth. 

Current, Axial A term proposed 

for a current whose direction coincides 



with the direction of the lines of magnetic 
force. 

This use of the term axial current is in 
contradistinction to a radial current, or one 
whose direction is at right angles to the 
direction of the lines of magnetic force. 

The term axial current is employed in elec- 
tro-therapeutics in a different sense to the 
above. (See Current, Axial.) 

Current, Beginning' of A term 

sometimes employed for the making or 
closing of the current in any circuit. 

Current, Bony A term proposed 

by Becquerel for the electric current re- 
sulting from the difference of potential ex- 
isting between two different parts of a bone 
of a recently killed animal. 

If a bone be taken from a recently killed 
animal and the marrow connected by means 
of metallic terminals with the surface of the 
bone, an electric current will flow through 
the circuit, for which Becquerel proposed the 
name bony current. 

This term is not generally adopted. 

Current, Cessation of — A term 

sometimes employed for the breaking of 
the current in any circuit. 

Current, Demagnetizing A cur- 
rent whose magnetic field is employed to 
decrease the strength of an already existing 
magnetic field by directing its lines of 
force oppositely to that of the existing field. 



Cur.] 



590 



[Cur. 



Current, Effective A term pro- 
posed by Ayrton, but not accepted, for the 
current producing a given effect. 

This term, Ayrton thinks, is an unfortunate 
one, since the effective current will of course 
depend on the character of the effect the cur- 
rent is desired to produce. 

If, however, the word "effect" be under- 
stood to mean "power," then the vagueness 
ceases, and, since the power is proportional 
to the square of the current, the effective 
current is the square root of the mean 
squares, but all the effects produced by an 
alternating current are proportional to the 
square root of the mean squares. 

The ordinary meaning of effective current 
is that given it by the definition of the Elec- 
trical Congress of Paris, in 1889, viz., the 
square root of the time average of the square 
of the current. 

An alternating or periodically varying 
current has an "effective" strength such 
that if this effective strength were steadily 
maintained in the same direction through a 
given resistance it would generate as much 
heat in a given length of time as the periodi- 
cal current. 

When electrolysis or the magnetization of 
iron is the effect produced, the effective cur- 
rent is identical with the mean current. 
Where a heating or dynamometric effect is to 
be produced, the effective current is equal to 
the square root of the mean square of the 
current. 

Current, Effective Starting, of Motor 

The indicated value of the starting 



a current. (See Appendix — Current,. 
Upper Harmonics of.) 

-A term proposed by 



current of a motor as observed on an 
ammeter. 

Current Efficiency of Secondary Battery. 

— (See Appendix — Battery, Secondary, 
Current Efficiency of.) 

Current, Entering, of Telegraphic Cir- 
cuit A term employed to designate 

the current on a telegraphic line or con- 
ductor near the battery. 

Current, Harmonics of A term 

sometimes used for the upper harmonics of 



Current, M. — 

Ayrton for mean current. 

This term, M. current, is employed to sig- 
nify the average value with respect to time, 
and is obtained by dividing the total quantity 
of electricity which passes through a given 
circuit in a given number of seconds by the 
number of seconds. It has not been gen- 
erally accepted. 

Current, M. S. A term proposed 

by Ayrton for mean square current. 

This term was proposed in order to avoid 
the use of the alleged vague term, effective 
current. It applies to cases where the effec- 
tive current has a value equal to the mean 
square of the current. It has not been gen- 
erally accepted. 

Current, Maximum Starting, of Motor 

The highest value that the starting 

current of a motor attains. 

Current of Charge on Telegraphic Line. 

— (See Appendix — Line, Telegraphic, 
Charge Current on.) 

Current, Polyphase A term now 

generally employed in place of multiphase 
current. (See Current, Multiphase.) 

Current, Polyphase Alternating, Pro- 
posed A. I. E. E. Definition for A 

combination of more than two alternating 
currents differing in phase. 

Current, R. M. S. — A term pro- 
posed by Ayrton lor the square root of the 
mean square of the current. 

This term was proposed in order to avoid 
the use of the alleged vague term, effective 
current. It applies to cases where the effec- 
tive current has a value equal to the square 
root of the mean square of the current. It 
has not been generally accepted. 

Current, Radial A term proposed 

for a current whose direction is at right 
angles to the direction of the lines of mag- 
netic force. 



Car.] 



591 



[Cur. 



This use of the word radial current is in 
contradistinction to the word axial current, 
whose direction coincides with that of the 
lines of magnetic force. (See Appendix — 
Current, Axial.') 

Current, Simple or Two-Phase Alternat- 
ing* Two alternating currents whose 

phases differ by 90 or by 270 . 

Current, Sinusoidal A term some- 
times employed for sinuous current. (See 
Current, Sinuous.) 

A simple-harmonic current in respect to 
time. 

A current whose strengths graphically 
set forth as ordinates as time to abscissas 
follow a sinusoidal curve. 

Current, Starting", of Motor The 

current which a motor requires in order to 
start from a state of rest. 

Current Transformation. — (See Appen- 
dix — Transform a tio n , Cur r en t. ) 

Current, Triphase A term some- 
times employed in place of three-phase 
current. (See Appendix — Currents, Three- 
Phase.) 

Current, Triphase Alternating, Proposed 
A. I. E. E. Definition for Three al- 
ternating currents whose phases differ by 
6o° or 120 . 



Current, Tubular 



-A term some- 



times applied to a current that traverses 
the superficial portions only of a conductor. 

When a rapidly intermittent current is sent 
through a solid conductor, the current den- 
sity is greater at the surface of the conductor 
than in the central portions, and, when the 
rapidity of alternation becomes very great, 
is confined to an exceedingly thin outer layer. 

A tubular current possesses no magnet- 
izing power on anything placed inside the 
tube. 

Current, Upper Harmonics of A 

series of higher harmonic currents of 
greater frequency than the fundamental 
current impressed on a simple-harmonic 



current by any means. (See Appendix — 
Currents, Complex-Harmonic.) 

Current, Virtual — A somewhat 

vague term sometimes employed for a cur- 
rent virtually equivalent to something else. 

A term employed for the square root of 
the mean square of the current strength. 

Current, Working, of Motor The 

current required to maintain a motor when 
its load is on. 

Currents, Complex-Harmonic — 



Currents which result from the superposi- 
tion of several simple-harmonic currents. 
(See Current, Simple-Harmonic .) 

Currents resulting from the co-existence 
of the higher harmonic currents with the 
fundamental harmonic current. 

Unless certain precautions are taken the 
currents produced in the secondary circuit of 
a transformer or induction coil are by no 
means simple-harmonic currents. It is true, 
of course, that the fundamental frequency 
has the same frequency as that of the cur- 
rents sent through the primary circuit, but 
the currents so induced in the secondary, 
however, are complex-harmonic currents, 
their frequency depending, according to Pu- 
pin: " On the fundamental frequency of the 
ohmic resistance, and especially on the self- 
induction and electrostatic capacity of the 
primary or secondary circuits." 

Complex-harmonic currents of the second- 
ary of induction coils possess a fundamental 
frequency the same as the frequency of the 
currents impressed on the primary, but they 
have associated with them a number of 
higher harmonic currents, which correspond 
to the overtones of a musical note. 

These overtones are due to rapid elec- 
trical oscillations accompanying the spark 
discharges. The association of these higher 
harmonic currents with the fundamental 
harmonic current produces what are called 
complex-harmonic currents. 

Complex-harmonic currents always exist 
when there is iron in a circuit, especially if 
the iron is highly magnetized, when they are 
due to the fact that the magnetization pro- 



Cur.] 



592 



[Cur. 



duced is not proportional to the magnetizing 
force. 

It is only in circuits of constant resistance, 
containing no iron, that the current produced 
by a simple harmonic or sine wave of E. M. 
F. is a sine wave. Magnetic hysteresis, or 
a periodically varying resistance as by an 
electric arc, causes a distortion of the cur- 
rent and a consequent superposition of 
higher harmonics on the fundamental wave. 
Consequently the primary currents of trans- 
formers at open secondary circuit or very 
light load are complex harmonics, and 
approach more nearly to true sine shapes at 
increasing loads. When, however, the 
secondary E. M. Fs. of a transformer are 
simply harmonics, the secondary currents 
are also simply harmonics, in circuits with- 
out iron cored coils. 

Currents produced by complex-harmonic 
E. M. F. are also complex harmonic; gen- 
erally, however, the higher complex har- 
monics of the E. M. F. wave are larger than 
the complex harmonics of the current wave. 



Currents, Mutually-Induced 



-Cur- 



rents set up or produced by means of 
mutual induction. (See Induction, Mu- 
tual.) 



Currents, Polyphase 



Currents 



differing in phase from one another and, 
therefore, requiring separate circuits for 
use. 

The currents may differ from one another 
by one-half phase, by one-third of a phase, 
a quarter phase and so on, when they are 
respectively called di-phase or two-phase 
currents, triphase or three-phase currents, 
and four-phase currents. An ordinary alter- 
nating current is called a single-phase or Uni- 
phase current. The latter term is the prefer- 
able one. 

The term polyphase currents is applied to 
all currents over three-phase, though some- 
times also to all currents over two-phase. 

Currents, Polyphased, Alternating 

— Two or more alternating currents differ- 
ing in phases from each other. 

Currents, Skin A term some- 



times applied to the currents that are 
limited to the surface of a solid conductor. 
Rapidly alternating currents are limited 
to the surface of solid conductors since be- 
fore any such currents have time to pene- 
trate towards the centre of a solid conductor 
their direction is reversed, thus limiting 
them to the surface portions. 

Currents, Three-Phase Triphased 

currents. (See Appendix — Currents, Tri- 
phased, Alternating.) 

Currents, Triphased, Alternating 



— Three alternating currents differing 120 
in phase from each other. 

In the two-phase system two currents 
differing in phase 90° have a common return 
wire whose area should be V 2 greater than 
either leading wire. 

In the three-phase system each of three 
currents differing in phase 120° uses alter- 
nately one or two of the three wires for a 
return. 

Curve, Arrival, of Telegraph Circuit 

A curve of ordinates and abscissas 

which represent respectively the times and 
the gradual increase of current at the re- 
ceiving end of a telegraph circuit from the 
time the circuit is closed until the time the 
current has reached its full strength. 

Curve, Clown's Hat A term pro- 
posed for the curve of a current or electro- 
motive force in which the pressure generated 
increases or decreases at a maximum rate 
of change. 

The name is taken from the shape of the 
curve being somewhat similar to the shape 
of a peaked or clown's hat. 

Curve, Top-Hat A term proposed 

for the current or E. M. F. in which the 
pressure generated is fairly constant for a 
considerable time at its maximum rise and 
fall. 

The name is taken from the shape of the 
curve being somewhat similar to that of a 
top-hat, or flat crowned hat. A current for 
the primary of a transformer or induction 



Cut.] 



593 



[Dec. 



coil, however, of the top-hat type, makes a 
bad form of secondary current curve, for in 
such a curve the rate of change, whether 
increasing or decreasing, would be small. 
The current whose curve of electromotive 
force is sharp and peaked like a clown's hat 
would, of course, be preferable. 

Cut-In, A A term sometimes 

employed in place of film cut-out. 

An automatic-guard cut-out. (See Cut- 
Out, Film.) (See Appendix — Guard, Auto- 
matic, for Series-Connected Incandescent 
Lamps.) 

Cut-Out, D. P. A contraction 

for double-pole cut-out. (See Appendix — 
Cut-Out, Double-Pole,) 

Cut-Out, Double-Pole A cut-out 

which provides in one operation the cut- 
ting out of both the positive and the nega- 
tive leads. 

Cut-Out, Electro-Magnetic A term 

sometimes employed for a cut-out operated 
by means of an electro-magnet. (See Cut- 
Out, Automatic, for Series-Comiected 
Electro-Receptive Devices.) 

A form of electro-magnetic cut-out is used 



in charging accumulators and sometimes in 
street railway circuits. 

Cut-Out, S. P. A contraction for 

single-pole cut-out. (See Appendix — Cut- 
Out, Single-Pole.) 

Cut-Out, Single-Pole A cut-out by 

means of which the circuit is broken or 
cut in one of the two leads only. 

Cut-Out, Wedge A form of cut- 
out employed on telegraphic circuits. 

The ends of the instrument wire are con- 
nected to the opposite sides of a wedge 
formed of two brass plates suitably insulated 
from one another. The ends of the line wire 
or conductor are suitably connected to two 
metallic pieces that are maintained in elec- 
trical contact by means of a spring electri- 
cally connected to one of the pieces and 
caused to bear with elastic pressure against 
the other piece. In order to introduce an 
instrument into the line circuit, a switch- 
wedge, or plug, is inserted between the two 
pieces, and, thus separating them, opens 
the circuit of the line wire or conductor, and 
at the same time connects it with the instru- 
ment thus introduced. 

Cyclic. — Of or pertaining to a cycle. 
(See Cycle.) 



D. B. Switch. — (See Appendix — Switch, 
D. B.) 

D. P. Cut-Out (See Appendix— Cut- 
Out, D. P.) 

D. P. Switch. — (See Appendix — Switch, 
D. P.) 

Damping Magnet. — (See Magnet, Damp- 
ing.) 

Dark Discharge. — (See Appendix — Dis- 
charge, Dark.) 

Dark Segment of Aurora. — (See Appen- 
dix — Segment, Dark, of Aurora.) 

Dead Ground. — (See Appendix — Ground, 
Dead.) 



Declination Compass. — (See Appendix — 
Compass, Declination.) 

Decomposition, Electro-Chemical 

A term often employed for electrolytic 
decomposition. (See Electrolysis.) 

Decomposition, Molecular — The 

separation or breaking up of a molecule 
into its constituent atoms or radicals. 

Molecular decomposition may be effected 
in the following ways, namely: 

(i) By electrolysis, or the action of an 
electric current. 

(2) By thermolysis, or the action of heat.' 

(3) By actinism, or the action of light. 



Def.] 



594 



[Die. 



(4) By chemism, or the action of superior 
chemical affinity. 

(5) By pressure. 

Deflecting Magnet. — (See Appendix — 
Magnet, Deflecting.) 

Degree, Water- Gramme — The 

amount of heat required to raise the tem- 
perature of one gramme of water at 4 C, 
the temperature of its maximum density, 
one degree centigrade. 

A small calorie. (See Calorie, Small.) 

Delta Triphase System. — (See Appendix 
— System, Delta Triphase^) 

Demagnetizing Current. — (See Appen- 
dix — Current, Demagnetizing.) 

Depolarizer. — The material employed in 
a voltaic cell for the purpose of depolarizing 
it. (See Cell, Voltaic, Polarization of.) 

In most cases the depolarizer is a different 
liquid and is kept separate from the exciting 
liquid or electrolyte. In some cases, how- 
ever, the depolarizer is mixed with the excit- 
ing liquid. 

Deposit, Electro - Metallurgical Burnt 

A term sometimes applied to a black 

deposit of metal which is thrown down 
when the intensity of the depositing cur- 
rent is too strong. (See Deposit, Electro- 
Met a llurgica I. ) 

Deviation, (Juadrantal, of Mariner's Com- 
pass The deviation of the magnetic 

needle due to the induced magnetism in 
the iron of a ship acting as a mass of soft 
iron, and not as a permanent magnet. 

Quadrantal deviation changes sign and 
passes through successive opposite maxima 
four times in one complete revolution of the 
ship. 

Quadrantal deviation is corrected by plac- 
ing masses of soft iron, usually spherical in 
shape, in suitable positions on each side of 
the compass. 

Deviation, Semi- Circular, of Mariner's 
Compass The deviation of a mag- 
netic needle due to the permanent mag- 



netism in the iron of a ship having its 
resultant in the horizontal plane. 

Semi-circular deviation passes through 
two opposite maxima and two zero points as 
the ship completes a revolution, and these 
zero points of deviation occur when the 
resultant magnetic axis of the ship coincides 
with the magnetic meridian. 

Semi-circular deviation is corrected by 
fastening a permanent magnet in the proper 
position near the compass to neutralize the 
influence of the ship's iron. 

Diagram, Load — A 'diagram or 

curve representing to scale the load or ac- 
tivity of a plant at different times. 

Dial, Induced Single-Needle — A 

dial employed in single-needle telegraphy 
in which both the needle and its axle are 
formed of soft iron and have magnetism 
induced in them by means of permanent 
horseshoe magnets placed so as to act 
magnetically on the needle. 

The object of the induced single-needle 
telegraphic dial is for the purpose of avoid- 
ing the weakening of the magnetism of the 
needle, or its total loss or reversal, by vari- 
ous means, such, for example, as a discharge 
of lightning, the effect of earth currents, etc. 

Dial Telegraph. — (See Appendix — Tele* 
graph, Dial.) 

Dialyzing. — Subjecting to the process of 
dialysis. (See Dialysis.) 

Diamagnetized. — Endowed with dia- 
magnetic properties. (See Diamagnetism.) 

Diamond Drill. — (See Appendix — Drill, 
Electric, Diamond.) 

Dielectric, After- Working of A 

term sometimes employed for a residual 
charge. (See Charge, Residual.) 

The term after-working of a dielectric was 
proposed by Boltzmann. It is not much 
used in the United States. 

Dielectric, Breaking-Down of 

Such a weakening of a dielectric that per- 
mits a disruptive discharge to pass through 



Die.] 



595 



[Dis. 



its substance. (See Appendix — Dielectric, 
Disruptive Strength of.) 

Dielectric, Disruptive Strength of 

— The resistance which an insulating 
medium or dielectric offers to the disrupt- 
ive passage of an electric discharge 
through it. 

According to Steinmetz the disruptive 
strength of different materials shows no re- 
lation to their electric resistance. 

Dielectric Hysteresis. — (See Appendix — 
Hysteresis, Dielectric.) 

Difference of Tension. — (See Appendix — 
Tension, Difference of.) 

Differential Coils. — (See Appendix — 
■Coils, Differential.) 

Differential Electro-Dynamometer. — (See 
Appendix — Dynamometer, Electro, Differ- 
ential.) 

Differential Electro-Magnet. — (See Ap- 
pendix — Magnet, Differential, Electro.) 

Differential Winding. — (See Appendix — 
Winding, Differential.) 

Diffusing Globes for Electric Lights. — 

(See Appendix — Globes, Diffusing, for 
Electric Lights?) 

Di-Phase Armature. — (See Appendix — 
Armature, Di-Phase.) 

Di-Phase Generator. — (See Appendix — 
Generator, Di-Phase.) 

Di-Phase Motor, — (See Appendix — 
Motor, Di-Phase.) 

Diplex Telegraph. — (See Appendix — 
Telegraph, Diplex.) 

Dip of Line Wire or Conductor. — (See 
Appendix — Conductor or Line Wire, Dip 
of.) 

Dipping Basket. — (See Appendix — Bas- 
ket, Dipping.) 

Dipping Hook. — (See Appendix — Hook, 
Dipping.) 



Dips. — Acid solutions employed in elec- 
tro-plating in which articles that are to be 
plated are cleansed by dipping. 

Direct-Current Dynamo-Electric Ma- 
chine. — (See Appendix — Machine, Dyna- 
?no-Electric, Direct- Current.) 

Direct-Current Exciter. — (See Appendix 
—Exciter, Direct-Current.) 

Direct- Current Rotary Transformer. — 

(See Appendix — Transformer, Direct-Cur- 
rent Rotary.) 

Direct Reading Galvanometer. — (See 
Appendix — Galvanometer, Direct Read- 
ing.) 

Direct Working of Telegraphic Sounder. 

— (See Appendix — Worki?ig, Direct, of 
Telegraphic Sounder.) 

Directed - Streaming Discharge. — (See 
Appendix — Discharge, Directed-Stream- 

ing.) 

Directing Clock. — (See Appendix — Clock, 
Directing.) 

Disc, Retarding A copper disc 

supported on a rotating shaft, and so 
placed as to cut the lines of force from a 
magnet for the purpose of retarding the 
speed of rotation. 

In Elihu Thomson's recording electric 
meter a copper disc, moving in the field of a 
permanent magnet, is so retarded that the 
resulting number of revolutions is directly 
proportional to the energy to be measured. 

Discharge, Dark A term applied 

by Faraday to that portion of a convective 
discharge, separating the positive from the 
negative electrode, that occurs under 
certain circumstances through a rarefied 
gas. 

Discharge, Directed-Streaining 

A Tesla discharge which assumes the 
shape of a hollow luminous cone. 
The discharge takes place between a sphere or 
ball S (Fig. 570), and a ring-shaped electrode. 



Dis.] 



596 



[Dis. 



W, thereby producing a hollow luminous cone 
such as is shown in the figure. 




Fig. 57 °- Directed- Streaming Discharge, 

Discharge, Luminous Disc-Shaped 

— A name given to a variety of Tesla dis- 
charge that occurs between ring-shaped ter- 
minals. 

The terminals are arranged as shown in Fig. 
571. On the passage of the current a luminous 




shaped terminals C, C, which presents the ap- 
pearance shown in the figure. 

Discharge, Slow, Method of An 

insulation test for a well-insulated telegraphic 
line, by the observation of the rate at which 
a charge leaks out when the conductor is left 
insulated. 

A well-insulated cable will take, say, half an 
hour to fall to half charge, and, with uniform, 
cables, this time is independent of their length. 

Discharge, Spark An electric dis- 
charge effected by means of a spark. 

A disruptive discharge. (See Discharge, Dis- 
ruptive.) 

Discharge, Tesla An exceedingly 

high frequency discharge. 

The Tesla discharge is so named after its dis- 
coverer, Nikola Tesla. 

Dish, Chafing, Electric An elec- 
trically heated chafing dish. 

An electric heater is applied to an ordinary 
chafing dish, so as to permit the electrical heat- 
ing to take the place of ordinary heating. 

A form of electrically heated chafing dish is 
shown in Fig. 572, and will be readily understood 
from inspection. (See Heater, Electric. ) 




Fig* 571. Luminous Disc-Shaped Discharge. 

disc-shaped discharge occurs between the ring- 



Fig. 57 2. Electric Chafing Dish. 

Disruptive Strength of Dielectric. — (See 
Appendix— -Dielectric, Disruptive Strength 

of.) 

Dissonance, Electric Electric dis- 
agreement. 

Two alternating currents are in electric dis- 
sonance when their periods are different. The 
term electric dissonance is employed in contra- 
distinction to electric consonance. 

Distance, Striking The distance 

through which a disruptive discharge will 
pass. (See Discharge, Disruptive.) 

Distance, Striking, for Various Sub- 
stances Tables of Steinmetz give the 

following values for the striking distances of 
various mediums under certain ciroumstances. 



Dis.] 



597 



[Dis. 



Air 

Mica 

Vulcanized Fibre 

Dry Wood Fibre 

Paraffined Paper S 

Melted Paraffin, 65 C 8 

Boiled Linseed 0il,2i° C 5 

Turpentine Oil 8 



8 IN MILLI-CENTIMETRES, V IN KILO-VOLTS. 
5 = 36 ( e -i. 3 V_ i ) + 54 V + i.2V» 

8 = .24V+.0145V 9 

fi = 7.66 V + 2.3 V 2 2. 

8 = 7.66 V 2. 



3 V... 

12.4 V. 

12.5 v. 
15.7 v. 



Copal Varnish 

Crude Lubricating Oil 

Vulcabeston 

Asbestos Paper 

Creeping discharge over surface of Mica. 



= 30 V 

= 60 V 

= 28 V 

= 23 V 

= 55 (V-2)* 



6.9 
3-9 
7-6 
7-i 
9-7 
4.4 
4.0 
2.7 
4-5 



<V 

< v 
<v 
<v 
<v 

<v 
<v 
<v 

< V 

= v 

< V 

<v 

< V 



_ 24.0 
_ 20.3 
_ 22 -5 

< 21.6 

< 24.8 
_ 27.1 
<«.3 
<-5.6 
_ 20.4 

< .5.9 

< 12.6 

< 5.o 
<x 7 .. 



In the above table 8 equals the thickness 
of the dielectric in milli-centimetres, or 
thousandths of a cm.; e equals the Napierian 
base, and V equals the potential difference in 
kilo-volts. 



The last column gives the lowest and highest 
values of V in the experiments on the different 
materials. 

The following table gives the data concerning 
a disruptive discharge through air: 



Table I.— Disruptive Discharge Through Air. 

5 = 36 



(e~ l 3 V - I ) + 54V + i.2V.^ 



Maximum Differ- 


Sparking Distance 


Electrostatic Gra- 


Sparking Distance 


Difference. 


Difference in 


ence of Potential 


observed in Milli- 


dient, in Kilo- 


calculated in Milli- 


8 — 5 


per cent, of 


in Kilo-Volts. 


centimetres. 


Volts per cm. 


centimetres. 


8 










calc. obs. 


calc. 


V 


8 
obs. 


S 


8 
calc. 


A 


X 


.18 


3-o 


60 


2.2 


— .8 


(-36) 


.26 


4.6 


57 


3-8 


— .8 


(-21) 


.29 


5-i 


57 


4-5 


— .8 


—13-3 


>4 6 


8.1 


57 


8.9 


+ -8 


+ 9-o 


. 4 8 


9.1 


53 


9-5 


+ -4 


+ 4-2 


•53 


11 


48 


11. 








•7i 


16 


44 


17. 1 


+ 1.1 


+ 6.4 


1.43 


48 


30 


49-3 


+ 1.3 


+ 2.6 


1.76 


68 


26 


66.4 


— 1.6 


— 2.4 


2.46 


100 


25 


IOS-7 


+ 5-7 


+ 5-4 


3-96 


190 


21 


197 


+ 7 


+ 3-5 


5-5 


287 


19 


297 

584 


+ 10 


+ 3-4 


9-5 


575 


17 


+ 9 


+ 1.6 


12.7 


860 


15 


844 


-16 


— 1.9 


15-7 


1150 


14 


IIIO 


—40 


-3-6 


196 


1440 


14 


1480 


+40 


+ 2.7 


22.6 


1730 


13 


1800 


+70 


+ 3-9 


24.0 


2010 


12 


1950 


—60 


— 3-i 


Average 








±14-7 


± 4.2 









Distant Battery. — (See Appendix — Bat- 
tery, Distant.) 



Distortion of Magnetic Field.— (See 
Appendix — Field, Magnetic, Distortion of.} 



Dis.] 



598 



[Dyn. 



Distributing Board.— (See Appendix — 
Board, Distributing.) 

Distributing" Brushes of Electric Motor. 

— (See Appendix — Brushes, Distributing, of 
Electric Motor) 

Distributing Switch Board.— (See Appen- 
dix — Board, Distributing Switch) 

Distribution of Complex Lamellar Mag- 
netism. — (See Appendix — Magnetism, Com- 
plex La?nellar, Distribution of) 



Disturbance, Magnetic 



— A term 



sometimes employed for the temporary varia- 
tions in the intensity of the earth's magnet- 
ism caused by a magnetic storm. 

Divided Touch. — (See Appendix — Touch, 
Divided.) 

Door Trigger. — (See Appendix— Trigger, 
Door) 

Dot-and-Dash Code. — (See Appendix — 
Code, Dot-and-Dash) 

Double Block, Duplex. — (See Appendix — 
Block, Double Duplex) 

Double-Bronze Wire. — (See Appendix — 
Wire, Double-Bronze) 

Double-Contact Push. — (See Appendix — 
Push, Double-Contact) 

Double-Contact Push Button.— (See Ap- 
pendix — Button, Push, Double-Contact) 

Double-Current Telegraphic Working.— 

(See Appendix — Working, Double-Cur retit 
Telegraphic) 

Double-Curve Pull-Off. — (See Appendix — 
Pull-Off, Double-Curve) 

Double-Curve Trolley Hanger.— (See 

Hanger, Double-Curve Trolley) 

Double Liquid Voltaic Cell.— (See Cell, 
Voltaic, Double Liquid) 

Double-Pole Cut-Out.— (See Appendix— 
Cut-Out, Double-Pole) 

Double-Wire System for Electric Light 

Leads. — (See Appendix — Leads, Double- 
Wire System for Electric Light) 



Drifting of Zero Point.— A term fre- 
quently employed in place of shifting of zero 
point. (See Appendix — Shifting of Spot of 
Light) 

Drift of Needle.— (See Appendix— Needle, 
Drift of) 

Drill, Electric Diamond A dia- 
mond drill driven by electric power. 

Drill, Electro-Percussion A drill 

for quarrying or mining purposes, in which 
the reciprocating motion is obtained by send- 
ing alternately a current through a pair of sole- 
noids of which the drill stock forms the core. 

Drill, Electro-Reciprocating An 

electro-percussion drill. (See Appendix — 
Drill, Electro-Perctission) 

Drop Relay-Contact.— (See Appendix— 
Cojitact, Drop-Relay) 
Drop Trolley.— (See Trolley, Drop) 

Dry Battery.— (See Appendix— Battery, 
Dry) 

Dry Gelatine Cell.— (See Appendix— CV// S 
Dry Gelatine) 

Duplex Balance. — (See Appendix — Bal- 
ance, Duplex) 

Duplex Telegraph. — (See Appendix — 
Telegraph, Duplex) 

Duplex Telephony. — (See Appendix— 
Telephony, Duplex) 

Dust, Electrical Aggregation of, in Dust- 
Laden Air A coalescence of a great 

number of separate particles of dust, in dust- 
laden air, by means of the action of an elec- 
trical brush discharge. 

If a brush or convection discharge be passed 
through dust or smoke-laden air, contained for 
purposes of observation in a glass globe, the 
electrical aggregation of the particles of dust or 
smoke rapidly clears the air. This method is 
practically employed in the manufacture of lamp- 
black. 

Dyad Atom. — (See Appendix — Atom, 
Dyad) 

Dynamic Multiplier.— (See Appendix— 
Multiplier, Dyjiamic) 

Dynamics.— That branch of mechanics 



Dm.] 



599 



[Eff. 



which treats of the action of a force in pro- 
ducing motions or pressures. 

Dynamo-Electric Machine for Electro- 
Plating, — (See Appendix — Machine, Dy- 
namo-Electric, for Electro-Plating.) 

Dynamo, Idle Wire of (See Appen- 
dix — Wire, Idle, of Armature of Dynamo?) 

Dynamometer, Electro, Differential 

— A double dynamometer with the moving 
coils rigidly connected and oppositely influ- 
enced, so that the movement of the suspen- 
sion system can be reduced to zero by elec- 
trical adjustments when the instrument is 
under operation. 

Dynamo, Motor (See Appendix — 

Motor, Dynamo?) 

Dynamo or Motor Frame. — (See Appen- 
dix — Frame, Dynamo or Motor) 

Dynamo Standards. — (See Appendix — 
Standards, Dyna?no.) 

Dynamos Coupled in Potential Series. — 
(See Appendix — Series, Potential, Dynamos 
Coupled in.) 

Dynamotor. — A continuous current trans- 
former. 



A term now generally employed for motor- 
generator. (See Generator, Motor?) 

A motor-dynamo, or motor-generator, is prac- 
tically a dynamo driven by means of an electric 
current. The motor-dynamo consists of two dis- 
tinct or separate armatures placed on the same 
shaft, or two separate armature windings placed 
on the same core. On sending the current 
through one armature or winding it acts as a 
motor and turns the shaft, thus producing current 
in the other armature or winding. Such a ma- 
chine is sometimes called a rotary transformer, 
though this name is preferably limited to a ma- 
chine containing only a single armature, which 
acts as a generator and motor armature. (See 
Transformer, Constant Current.) 

Such a machine is employed for transforming 
continuous currents into continuous currents of 
different potential, or for transforming alternating 
or polyphase currents into continuous currents, or 
vice versa. 

Dyne : cm. — An abbreviation proposed for 
dyne-centimetre, the C. G. S. unit of moment 
of couple. 

Dyne :cm 2 . — An abbreviation proposed for 
dyne per square centimetre, the C. G. S. unit 
of pressure. 



E. — A symbol proposed for electromotive 
force. 

The defining equation is E = RC. 

e. — A symbol proposed for difference of 
potential. 

The defining equation is e = rC. 

E. H. P. — A contraction for electrical horse- 
power. 

Earth, Bad A term sometimes em- 
ployed for a ground or connection to earth, 
the electric resistance of which is compara- 
tively high. (See Earth or Ground.) 

Earth Cell.— (See Appendix— Cell, Earth) 

Earth, Good A term sometimes em- 
ployed for a ground or connection to earth, 



the electric resistance of which is compara- 
tively low. (See Earth or Ground) 

Earthed. — Connected to ground or earth. 

Easement. — A permit, obtained from the 
owner of a property, for the erection of poles 
or attachments for telephonic, telegraphic or 
other electric lines. 

Effect, Page The faint sounds pro- 
duced when a piece of iron is rapidly magnet- 
ized and demagnetized. 

A faint click is produced when a bar of iron is 
magnetized or demagnetized. When, therefore, 
such a bar undergoes rapid magnetization and de- 
magnetization these separate sounds link them- 
selves into a continuous musical note, thus pro- 
ducing what is known as the Page effect. In the 



Eff. 



600 



[Ele. 



larger masses of iron employed in transformer 
cores and alternator armatures, the Page effect 
sometimes rises to a loud humming noise. 

Effects of Temperature on the Electric 
Resistance of Metals— (See Appendix — 
Resistance, Electric, of Metals, Effect of 
Te7nperatiire on) 

Effective Current— (See Appendix— Cur- 
rent, Effective?) 

Effective Starting Current of Motor. — 

(See Appendix — Current, Effective Starting, 
of Motor?) 

Efficiency of Electric Lamp. — (See Appen- 
dix — Lamp, Electric, Efficiency of.) 

Efficiency of Electric Motor. — (See 
Appendix — Motor, Efficiency of Electric) 

Efficiency of Radiation. — (See Appendix 
— Radiatio7i, Efficie?icy of.) 

Efficiency of Secondary Battery. — (See 
Appendix — Battery, Secondary, Efficiency 
of) 

Effluvia, Electric A term em- 
ployed in the early history of electricity for 
supposed effluvia proceeding from an electri- 
fied body and causing electrical phenomena. 

Effluvia, Magnetic A term em- 
ployed in the early history of magnetism for 
assumed, imponderable effluvia which were 
supposed to be given off by magnets. 

The doctrine of magnetic effluvia may be re- 
garded as a forerunner of the doctrine of lines of 
magnetic force introduced into science by Fara- 
day. 

In some of his earlier writings Boyle framed 
the hypothesis of a magnetic atmosphere, or 
region surrounding a magnet. He conceived 
the idea that magnetic effluvia, emitted from 
one of the poles of the magnet, passed through 
the space surrounding the magnet and re-entered 
it. at its other pole. As will be seen, this concep- 
tion closely resembles the modern conception con- 
cerning the flow of lines of magnetic force, or of 
magnetic flux. 

Egg", Electric A term formerly em- 
ployed for an egg-shaped vessel containing 
a partial vacuum through which an electric 
discharge is passed for the purpose of obtain- 
ing luminous effects. 



Elastance. — A word proposed for the re- 
ciprocal of permittance. (See Appendix — 
Permittance) 

Elastivity. — The elastance of a dielectric 
referred to unit volume. 

If the dielectric possesses great permittance it 
has of course but little elastance. 

Electric Amalgamator. — (See Appendix — 
Amalgamator, Electric) 

Electric Ana&sthesia. — (See Appendix — 
Ancestkesia, Electric) 

Electric Anemograph. — (See Appendix — 
Anemograph, Electric) 

Electric Atmosphere. — (See Appendix — 
Atmosphere, Electric) 

Electric Aura. — (See Appendix — Aura, 
Electric) 

Electric Broiler. — (See Appendix — 
Broiler, Electric) 

Electric Casting. — (See Appendix — Cast- 
ing, Electric) 

Electric Chafing-Dish. — (See Appendix — 
Dish, Chafing, Electric) 

Electric Chronometer. — (See Appendix — 
Chro7iometer, Electric) 

Electric Clamp Attachment. — (See Ap- 
pendix — Attachment, Electric Clamp) 

Electric Coil Heater. — (See Appendix — 
Heater, Coil, Electric) 

Electric Conflict. — (See Appendix — Con- 
flict, Electric) 

Electric Deck-Planer. — (See Appendix — 
Planer, Electric Deck) 

Electric Dissonance. — (See Appendix — 
Dissonance, Electric) 

Electric Door-Trip.— (See Appendix- 
TV/^, Door, Electric) 

Electric Effluvia. — (See Appendix — Efflu- 
via, Electric) 

Electric Egg. — (See Appendix — Egg, Elec- 
tric) 

Electric Escapement.— (See Appendix — 
Escapement, Electric.) 



Ele.] 



601 



[Ele, 



Electric Excitation. — (See Appendix — 
Excitation, Electric?) 

Electric Flat-iron. — (See Appendix — 
Flat-iron, Electric?) 

Electric Fluid. — (See Appendix — Fluid, 
Electric?) 

Electric Forge. — (See Appendix — Forge, 
Electric?) 

Electric Glue-Pot. — (See Appendix — 
Glue- Pot, Electric?) 

Electric Gnomon. — (See Appendix — Gno- 
mon, Electric.) 

Electric Harpoon. — (See Appendix — Har- 
poon, Electric?) 

Electric Horology.— (See Appendix — 
Horology, Electric.) 

Electric Hummer. — (See Appendix — 
Hummer, Electric?) 

Electric-Light Bath. — (See Appendix — 
Bath, Electric-Light?) 

Electric Machine Tool. — (See Appendix 
— Tool, Electric Machine?) 

Electric Matter. — (See Appendix — Mat- 
ter, Electric?) 

Electric Meteorograph. — (See Appendix 
— Meteorograph, Electric?) 

Electric Meteorology. — (See Appendix — 
Meteorology, Electric?) 

Electric Mining. — (See Appendix — Min- 
ing, Electric.) 

Electric Pendulum. — (See Appendix — 
Pendulum, Electric?) 

Electric Photo-Micography. — (See Ap- 
pendix — Photo-Micography, Electric?) 

Electric Pocket Gauge. — (See Appendix — 
Gauge, Electric Pocket?) 

Electric Pressure. — (See Appendix — 
Pressure, Electric?) 

Electric Radiation. — (See Appendix — 
Radiation, Electric?) 

Electric Radiator. — (See Appendix— Ra- 
diator, Electric.) 

Electric Rail Bond. — (See Appendix — 
Bond, Electric Rail?) 



Electric Residue.— (See Appendix— Resi- 
due, Electric?) 

Electric Spark.— (See Appendix— Spark, 
Electric. ) 

Electric Stopper Lamp.— (See Appendix— 
La?np, Electric Stopper.) 

Electric Stove-Plate.— (See Appendix— 
Stove-Plate, Electric.) 

Electric Telegraph.— (See Appendix— 
Telegraph, Electric?) 

Electric Tourniquet. — (See Appendix — 
Tourniquet, Electric.) 

Electric Wand. — (See Appendix — Wand, 
Electric.) 

Electric Windmill. — (See Appendix — 
Windmill, Electric.) 

Electrical Aggregation of Dust in Dust- 
Laden Air. — (See Appendix — Dust, Electri- 
cal Aggregation of, in Dust-Lade?i Air.) 

Electrical Aggregation of Raindrops. — 

(See Appendix — Raindrops, Electrical Ag- 
gregation of.) 

Electrical Baking Oven.— (See Appendix 
— Oven, Bakmg, Electrical.) 

Electrical Bombardment Lamp.— (See 

Appendix — Lanip, Bo7nbardment, Electri- 
cal.) 

Electrical Coking. — (See Appendix— Cok- 
ing, Electrical?) 

Electrical Equivalent of Heat.— (See 
Appendix — Heat, Electrical Equivalent of.) 

Electrical Harmonics. — (See Appendix — 
Harmonics, Electrical?) 

Electrical Stimulus of Nerve. — (See 
Appendix — Stimulus, Electrical, of Nerve?) 

Electrically Illumined Buoy. — (See 
Appendix — Buoy, Electrically Illumined.) 

Electrically Tuned System.— (See Appen- 
dix — System, Electrically Tuned.) 

Electricity, Reversible Heating Effect of 

A term sometimes employed in place 

of the Peltier effect. (See Effect, Peltier.) 



Ele.] 



602 



[Ele. 



An effect of this character is called reversible, 
because when the current is passed across an 
electro- thermal junction in one direction, heat is 
produced, while if it is passed in the opposite di- 
rection, cold is produced. 

Electricity, Spontaneous A term 

formerly employed for the electricity pro- 
duced by the melting of sulphur. 

This term is, of course, not employed at present, 
since electricity can never, properly speaking, be 
produced spontaneously. 

Electrification, Negative — The 

charging of a body with negative electricity. 

The negative charge. 

Electrification, Positive —The 

charging of a body with positive electricity. 

The positive charge. 

Electripherous. — A word proposed for 
anything capable of bearing or transmitting 
electricity. 

This word is unnecessary and its use should 
not be encouraged. 

Electrize, To To charge or electrify 

a body. 

The word corresponds to magnetize, to render 
a body magnetic or endow it with magnetic prop- 
erties. 

The word is sometimes spelled electrise. 

Electrizer. — That which electrizes or 
charges with electricity. 

Electro-Biologist. — (See Appendix — Biol- 
ogist, Electro?) 

Electro-Bioscopist. — (See Appendix — 
Bioscopist, Electro?) 

Electro-Chemical Accumulator. — (See 
Appendix — Accumulator, Electro-Chemical?) 

Electro-Chemical Decomposition. — (See 
Appendix — Decomposition, Electro- Chemi- 
cal?) 

Electro-Chemical Filtration. — (See Ap- 
pendix — Filtration, Electro-Chemical) 

Electro-Chronometric Counter. — (See 
Appendix — Counter, Electro-Chronometric?) 

Electro-Compound Magnet. — (See Appen- 
dix — Magnet, Electro-Compound) 

Electro-Culture.— Stimulating the growth 
of vegetation by means of electricity. 



The term is a bad one, since it should equally 
apply to a similar stimulation of animal growth. 

The term electro-culture has been proposed to 
characterize the electric stimulation of vegetation, 
which consists essentially in sending an electric 
current either through the plant whose growth is 
to be stimulated, or through the earth near the 
plant. 

In an experiment recently tried in France, a 
kilogramme of potatoes placed in the path of a 
weak current, under conditions exactly similar to 
those of an equal weight of potatoes uninfluenced 
by the electric current, produced 21 kilogrammes 
of healthy tubers as compared to 12 \ kilogrammes 
of non-electrically stimulated tubers. 

These experiments developed the fact that if a 
quantity of manure be planted near the positive 
pole of an electric source, the assimilable parts of 
the manure are transported or carried towards 
the negative pole. 

The phenomena would, therefore, appear to be 
connected with those of electric osmose or cata- 
phoresis. (See Osmose, Electric. Cataphoresis.) 

Electrode, Cataphoric — In electro- 
therapeutics an electrode impregnated with 
the medicament it is desired to introduce into 
the part to be treated by cataphoric medica- 
tion. (See Appendix — Medication, Cata- 
phoric) 

Electro-Deposition. — A term sometimes 
employed for electric deposition. (See Metal- 
lurgy, Electro) 

Electro-Dynamic Balance. — (See Appen- 
dix — Balance, Electro-Dynamic) 

Electro-Dynamic Interrupter. — (See Ap- 
pendix — Interrupter, Electro-Dynamic) 

Electro-Dynamic Rotation. — (See Appen- 
dix — Rotation, Electro-Dyna?nic) 

Electro-Dynamic Whirls. — (See Appen- 
dix — Whirls, Electro-Dynamic) 

Electro-Genesis. — A word proposed for 
the production of electricity. 

Electro-Genie. — Producing electricity. 

Electro-Gilding. — (See Appendix— Gild- 
ing, Electro) 

Electrograph. — A curve produced by a 
recording electrometer. 

Electrography.— A word proposed for that 
branch of science which treats of electricity. 



Ele.] 



603 



[Ele. 



A word proposed for the copying of fine en- 
graving on copper or steel by means of elec- 
tro-deposition. 

It will be seen that the word electrography has 
been proposed for two entirely distinct senses. 
The first use of the word would appear to be 
entirely unjustifiable. 

Electro-Kinetic Energy. — (See Appendix 
— Energy, Electro-Kinetic?) 

Electro-Lithotrity. — (See Appendix — 
Lithotrity, Electro?) 

Electrolization. — The act of being elec- 
trolyzed. 

The word is sometimes spelled electrolisation. 

Electrologist. — An electrician. 

The use of this word is entirely unnecessary. 

Electrolysis, Counter - Electromotive 

Force of — The counter-electromotive 

force produced in a plating bath or a second- 
ary cell by electrolysis. 

Electrolyte. — The exciting liquid in a 
voltaic cell. 

A compound liquid which is separable into 
its constituent ions by the passage of elec- 
tricity through it. 

Electrolytic Accumulator. — (See Appen- 
dix — Accumulator, Electrolytic.) 

Electrolytic Corrosion. — (See Appendix 
— Corrosion, Electrolytic?) 

Electrolytic Meter. — (See Appendix— 
Meter, Electrolytic?) 

Electro-Magnetic Cut-Out. — (See Appen- 
dix — Cut-Out, Electro-Magnetic.) 

Electro-Magnetic Gyroscope. — (See Ap- 
pendix — Gyroscope, Electro-Magnetic.) 

Electro-Magnetic Interference. — (See 
Ap pendix — Interference, Electro-Magnetic?) 

Electro-Magnetic Multiplier. — (See Ap- 
pendix — Multiplier, Electro-Magnetic?) 

Electro-Magnetic Separator. — (See Ap- 
pendix — Separator, Electro-Magnetic.) 

Electro-Magnetic Sorter.— (See Appen- 
dix — Sorter, Electro-Magnetic.) 

Electro-3Iaguetic Telegraph. — (See Ap- 
pendix — Telegraph, Electro-Magnetic.) 



Electro-Metallurgical Burnt Deposit. 

— (See Appendix — Deposit, Electro-Metal- 
lurgical Burnt?) 
Electrometer, Heterostatic — An 

electrometer in which the electrification to 
be tested is not the only electrification em- 
ployed. (See Heterostatic?) 

Electrometer, Idiostatic An elec- 
trometer in which the electrification to be 
tested is the only electrification employed. 
(See Idiostatic.) 

Electrometer, Long-Range A form 

of attracted-disc electrometer in which the 
range of the scale is comparatively long. 

Electrometer, Repulsion An elec- 
trometer in which the differences of potential 
are measured by means of the repulsion 
existing between two similarly charged 
bodies. 

Coulomb's torsion balance is an instrument of 
this class. A gold-leaf electrometer, when ar- 
ranged so that the amount of deviation can be 
readily measured, is also a repulsion electrometer. 

Electrometer, Symmetrical — A 

form of electrometer in which the needle is 
unaffected when it is placed symmetrically as, 
regards the deflecting segments. 

A quadrant electrometer is a form of sym- 
metrical electrometer. 

Electrometer, Thermo —A term 

sometimes employed for an electric ther- 
mometer. 

This use of the term probably arose from the 
fact that such an instrument may be employed to 
measure roughly the difference of potential be- 
tween points between which a spark passes. 

Electrometer Voltmeter. — (See Appen- 
dix — Voltmeter, Eleclro?net£r.) 

Electrometric. — Of or pertaining to an 
electrometer. 

Electromotive Force, Transformation of 

(See Appendix — Transformation, as. 

of Electromotive Force?) 

Electronome. — A term proposed for a 
measurer of electricity. 

This term is not only unnecessary, but is devoid 
of any precise meaning and may serve as an. 



Ele.] 



604 



[End. 



illustration of the thoughtless manner in which 
electric words are proposed. 

Electropath.— One skilled in the art of 
electro-therapy. 

Electropathy.— A word proposed for the 
treatment of disease by means of electricity. 

The word electro-therapy or electro-thera- 
peutics is generally used. 

Electro-Percussion Drill.— (See Appen- 
dix — Drill, Electro-Percussio?i.) 

Electrophone. — A word proposed by Ader 
for a form of telephone employing carbon 
contacts. 

Electro-Physiologist. — (See Appendix — 
Physiologist, Electro?) 

Electro-Potential Energy. — (See Appen- 
dix — Energy, Electro-Potential?) 

Electro-Puncturation. — (See Appendix — 
Puncturation, Electro?) 

Electro-Reciprocating Drill. — (See Ap- 
pendix — Drill, Electro-Reciprocati7ig) 

Electroscope, Semaphoric A name 

sometimes given to Henley's quadrant elec- 
troscope. (See Electroscope, Quadrant, 
Henley 's.) 

Electroscopic Gauge. — (See Appendix — 
Gauge, Electroscopic.) 

Electrostatic Aurora. — (See Appendix — 
Aurora, Electrostatic?) 

Electrostatic Corona. — (See Appendix— 
Corona, Electrostatic?) 

Electrostatic Influence. — (See Appendix 
— Influence, Electrostatic?) 

Electrostatic Motion. — (See Appendix— 
Motion, Electrostatic?) 

Electrostatic Motor. — (See Appendix — 
Motor, Electrostatic?) 

Electrostatic Strain. — (See Appendix — 
Strain, Electrostatic?) 

Electro-Steeling.— (See Appendix— Steel- 
ing, Electro?) 

Electro-Stereotype. — (See Appendix— 
Stereotype, Electro.) 

Electro-Synthesis.— (See Appendix— Syn- 
thesis, Electro?) 



Electro-Therniancy. — (See Appendix — 
Thermancy, Electro?) 

Electro-Thermotic. — (See Appendix— 
Thermotic, Electro?) 

Electro-Tint. — (See Appendix— Tint- 
Electro?) 

Electrotome. — A term formerly applied to 
an automatic contact breaker which vibrated 
with sufficient rapidity to produce a musical 
note. (See Contact Breaker, Automatic?) 

Electro-Tonicity. — (See Appendix— Toni- 
city, Electro?) 

Electro, Turtle-Back An electro- 
type curved so as to be capable of being em- 
ployed in the cylinder of a rotary newspaper 
press. 

Element of Battery. — A term sometimes 
applied to a single electric source or a battery 
of sources. 

Element of Yoltaic Battery. — A term 
sometimes applied to a single cell of a voltaic 
battery. 

The term element is properly applied to a 
single complete voltaic cell only when such a 
cell forms one of a number of cells so connected 
in a battery as to form a single electric source. 

It would appear that the use of the word ele- 
ment in the case of a single voltaic cell, whether 
connected with the battery or not, is inadvisable. 

Elliptical Rotary Magnetization. — (See 
Appendix — Magnetization, Elliptical Ro- 
tary?) 

Elongation, Maximum Negative 

The position of a vibrating body when it is 
at the extremity of its path on the negative 
side. 

Elongation, Maximum Positive 

The position of a vibrating body when it is 
at the extremity of its path on the positive 
side. 

Emission, Selective A selective 

radiation. (See Appendix — Radiation, Se- 
lective) 

End-to-End Joint. — (See Appendix— -Joint, 
End-to-End.) 



End.] 



605 



[Fac. 



Endosmose, Yoltaic A term some- 
times employed in place of electric osmose. 
(See Osmose, Electric) 

Energetics. — That branch of mechanics 
which treats of the transfer, transformation 
or modification of energy. 

Energy, Cubic A term sometimes 

employed for volumetric energy. (See 
Appendix — Energy, Volumetric) 

Energy, Electro-Kinetic Electric 

energy that is actually engaged in doing 
work. (See Energy, Kinetic) 

Energy, Electro-Potential Elec- 
tric energy possessing the power of, but not 
actually doing, work. (See Energy, Pote?i- 
tial) 

Energy, Specific Volumetric en- 
ergy. 

Energy, Tolnmetric A term pro- 
posed by Hospitalier for a quantity equal to 
the work divided by the volume. 

Energy, Tolnmetric, C. 0. S. Unit of 
An erg per cubic centimetre. 

Entering Current of Telegraphic Cir- 
cuit. — (See Appendix — Current, Entering, 
of Telegraphic Circuit) 

Epoch. — The time reckoned in the case of 
a vibrating body from the point of reckoning 
to the point of maximum positive elongation. 

Equalizing Wires. — (See Appendix — 
Wires, Equalizing) 

Equatorial Region of Magnet.— (See 
Appendix — Region, Equatorial, of Magnet) 

Ergometer. — A term proposed for an in- 
strument for measuring the amount of work 
done by a machine. 



This would more properly be called an erg- 
meter. The word, however, is seldom used. 

Erg : s. — An abbreviation proposed for erg 
per second, the C. G. S. unit of power. 
Error, Heeling, of Mariner's Compass 

The error in deviation of the mag- 
netic needle produced by that portion of the 
induced and permanent magnetism of the 
iron in a ship brought into action by the roll- 
ing or heeling of the vessel. 

Escape. — A term employed in telegraphy 
for leakage of the current from the line wire 
or conductor, from the effect of insufficient 
or faulty insulation, or from contact of the 
line with wet buildings or other uninsulated 
bodies. 

Escapement, Electric An electri- 
cally actuated clock escapement. 

Evanescent Telegraphic Signal. — (See 
Appendix — Signal, Telegraphic, Evanes- 
cent) 

Exciter, Direct Current A source 

of direct current, generally a direct current 
dynamo, employed for exciting the field mag- 
nets of an alternating current dynamo. 

Excitation, Electric The produc- 
tion of electrification by any means. 

Exhausted Plates of Storage Cell. — (See 
Appendix — Plates, Exhausted, of Storage 
Cell) 

Extension Bell. — (See Appendix— i?<?/7, 
Extension) 

External Magnetic Circuit. — (See Ap- 
pendix — Circuit, Magnetic, External) 

External Magnetic Field.— (See Appen- 
dix — Field, Magnetic, External) 



F. — A symbol proposed for farad, the 
practical unit of capacity. 

F. — A symbol proposed for force. 

The defining equation is F = M X A. The 
same symbol is also proposed for farad. 

eh— A symbol proposed for magneto- 
motive force. 



The defining equation is cF = 47T N I. 

F. M. — A contraction sometimes employed 
for field magnets. 

Fac-Simile Telegraph.— (See Appendix — 
Telegraph, Fac-Simile) 

Factor, Power The factor, less 

than unity, which must be applied to the ap- 



Fal.] 



600 



[FiL 



parent activity in an alternating current cir- 
cuit as obtained by the product of the volts 
and the amperes, in order to obtain the true 
activity. 

With sinusoidal currents and electromotive 
forces, the power factor is also equal to the cosine 
of the angle of lag in the current before or behind 
the pressure. 

Fallback Indicator. — (See Appendix — 
Indicator, Fallback?) 

Farad, International The value of 

the international farad adopted by the Chi- 
cago Congress of 1893 as equal to the capac- 
ity of a conductor charged to a potential of 
one international volt by one international 
coulomb of electricity. 

Faradic Coil. — (See Appendix— C02'/, Far- 
adze.) 

Faradism. — A word sometimes employed 
for faradization. 

Faradization would appear to be the preferable 
word. (See Faradization.) 

Fault, Low Test A term sometimes 

applied to a fault in an underground cable 
when the insulation resistance falls below a 
certain minimum value, say, for example, 5 
megohms per 100 volts per mile. 

Fault, Resultant — The apparent 

position and magnitude of a fault in a cable 
due to the resultant of all its leakage upon 
the electrical measurements made. 

Feeder Clamp. — (See Appendix — Clamp, 
Feeder?) 

Feeder Clip. — (See Appendix — Clip, 
Feeder?) 

Feeder for Trolley Conductor.— A wire 
or conductor of low resistance, employed for 
transmitting electric current directly from the 
power station to the trolley wire, and serving 
to maintain the potential at the point of junc- 
tion. 

Ferro-Magnetic. — A word sometimes em- 
ployed in place of paramagnetic. 

Ferro-Magnetism.— A word sometimes 
applied to the magnetism possessed by iron, 
or, in general, by paramagnetic substances. 
(See Paramagnetic?) 



Field Coils of Dynamo.— (See Appendix,. 
Coils, Field, of Dynamo?) 

Field, Magnetic, Distortion of A 

change in the direction or grouping of lines 
of magnetic force, in the field of a dynamo- 
electric machine or electric motor, produced 
by the reaction of the armature, or the mag- 
neto-motive force of the armature current. 

This distortion of the field renders it necessary 
to give a lead to the collecting or distributing 
brushes. (See Lead, Angle of. Lead of 
Brushes of Dynamo-Electric Machine.) 

Field, Magnetic, External That 

portion of a magnetic field which lies outside 
the magnet or external to it. (See Field, 
Magnetic?) 

Field, Magnetic, Internal That 

portion of a magnetic field which lies within 
the magnet. 

Field of Force. — (See Appendix — Force, 
Field of.) 

Field Plates. — (See Appendix — Plates, 
Field.) 

Field Spools of Dynamo-Electric Ma- 
chine. — (See Appendix, Spools, Field, of 
Dynamo-Electric Machine.) 

Figures, Karsten's A name some- 
times given to electric breath figures. (See 
Figures, Breath.) 

Filament, Coked A carbon fila- 
ment for an incandescent electric lamp that 
has been subjected to electrical heating in a 
vacuum, not only until thoroughly freed from 
its occluded gases, but also until its carbon is 
changed into a variety of coke. 

The coked carbon filament is the invention of 
Lodyguine. The coking is carried on in a 
vacuum, the process being continued for about 
eight seconds after the occluded gases have been 
driven off. 

The carrying off of the occluded gas is effected 
in the usual manner, and the strength of the cur- 
rent is then increased considerably. Under 
these circumstances the carbon of the filament 
becomes changed into a variety of coke. 

It is claimed that under the coking process the 
filament has its permanent or cold resistance 
greatly decreased until it becomes approximately 



Ml.] 



607 



[Flu. 



of the same value as that of the hot resistance of 
the filament before it was coked. The process is 
sometimes carried further than this, depending 
on the character cf the original carbonization. 

It is necessary, however, to stop the coking 
treatment when this point of resistance has been 
reached, since, if the heating be continued beyond 
this, the resistance of the filament again rises. 

Filament, Coking- of Subjecting a 

filament to the coking process. (See Fila- 
ment, Coked.) 

Filament, Incandescent A fila- 
ment that is rendered incandescent by the 
passage of an electric current. (See Lamp, 
Incandescent, Electric Filament of) 

In other words, a filament is incandescent only 
while it is actually emitting its own light. 

Filament, Incandescing' A fila- 
ment that can be rendered incandescent by 
the passage of an electric current. (See 
Lamp, Incandescent, Electric Fila?ne?it of.) 

Filament, Mounting- of A suitable 

connection for the filament to the leading- 
in wires inside the chamber of an incan- 
descent electric lamp. 

Filament, Treated Coked A car- 
bon filament the core of which has been elec- 
trically coked and whose surface is covered 
with, electrically deposited carbon derived 
from the decomposition of a hydrocarbon gas 
or vapor. 

Filtration, Electro-Chemical A 

term formerly employed in place of electric 
endosmose. (See Osmose, Electric. Phe- 
nomena, P or ret.) 

Finishing- Brushes.— (See Appendix — 
Brushes, Finishing.) 

Fire Alarm Telegraph. — (See Appendix — 
Telegraph, Fire Alarm) 

Fire Glow. — (See Appendix — Glow, Fire) 

Fitting-s, Combination, for Chandeliers, 

Brackets, Etc. Fittings that provide 

for the use of both gas and electricity 

Five-Wire System. — (See Appendix — Sys- 
tem, Five- Wire) 

Flash, Multiple Lightning- Several 



lightning flashes that apparently come from 
the same cloud. 

Lodge traces the cause of multiple lightning 
flashes to the same circumstances that produce 
in a Leyden jar the tendency of the jar to neu- 
tralize its charges by overflowing. (See Appen- 
dix — Jar, Leyden, Overflow of.) 

Flashing. — A process to which carbons 
are subjected, in order to give them a uniform 
electrical resistance throughout their entire 
length. (See Carbons, Flashing Process 
for.) 

Flat-Iron, Electric An electrically 

heated flat-iron. 

A hollow flat-iron provided with a suitably 
placed electric heater. (See Heater, Electric) 

Floor Contact— (See Appendix— Contact, 
Floor) 

Fluid, Austral — A term formerly 

employed for the magnetic fluid that was 
supposed to exist around or emanate from 
the austral pole of a magnet. (See Pole, 
Magnetic Austral) 

Fluid, Boreal A term formerly 

employed for the magnetic fluid that was 
supposed to exist around or emanate from 
the boreal pole of a magnet. (See Pole, 
Magnetic, Boreal) 

Fluid, Electric An assumed fluid 

which was formerly believed to be the cause 
of electric excitement. 

A belief in electric fluids no longer exists among 
intelligent electricians. 

Fluid, Magnetic A term formerly 

employed for an assumed fluid which was be- 
lieved to cause magnetic phenomena. 

The belief in magnetic fluids no longer exists. 

Fluid, Negative A specific fluid 

which was formerly believed by the advo- 
cates of the double-fluid electric hypothesis 
to be the cause of negative electric excite- 
ment. (See Appendix — Fluid, Positive) 

A deficit of an assumed single electric fluid. 
(See Electricity, Single-Fluid Hypothesis 
of) 

Fluid, Positive — A specific fluid 

which was formerly believed by the adherents 



Flu.] 



608 



[Fra. 



of the double-fluid electric hypothesis to be 
the cause of positive electric excitement. 

A surplusage of an assumed single electric 
fluid. 

According to the views of the single-fluid elec- 
tric hypothesis, positive excitement was supposed 
to be due to the surplusage of an assumed single 
electric fluid, the negative excitement being as- 
sumed to be due to its deficit. (See Electricity ', 
Single- Fluid Hypothesis of. ) 

Flush-Key Switch. — (See Appendix — 
Switch, Flush-Key?) 
Force, Electric, Transformation of 

— Producing or effecting a change in the 
value of the electromotive force by means of 
an induction coil, transformer or condenser, 
or by electric resonance. (See Transformer?) 

Force, Electromotive, Alternating 

— An electromotive force periodically passing 
through zero between positive and negative 
values. (See Current, Alternating) 

Force, Electromotive, Conversion of 

— A change in the value of the electromo- 
tive force produced by means of an induction 
coil, transformer or condenser, or by electric 
resonance. (See Transformer?) 

Force, Electromotive, Impressed, Pro- 
posed A. I. E. E. Definition for The 

ratio of the total activity in an electrically 
conducting circuit to its instantaneous cur- 
rent strength. 

Force, Electromotive, Opposing" 

A term sometimes employed for counter- 
electromotive force. (See Force, Electro- 
motive, Counter?) 

Force, Electromotive, Toltaic A 

term sometimes employed for the electromo- 
tive force generated at the electrodes of an 
electrolytic cell, in contradistinction to the 
counter-electromotive force produced at such 
electrodes by their polarization. 

Force, Field of — The space trav- 
ersed or crossed by the lines of electrostatic 
or magnetic force. 

An electrostatic field. (See Field, Elec- 
trostatic?) 

A magnetic field. (See Field, Magnetic?) 



Force, Magne-Crystallic 



— A name 

proposed by Faraday for the force assumed as 
the cause producing the change in the nature 
of the magnetism of certain crystalline bodies 
in different directions. (See Action, Magne- 
Crystallic?) 

Force, Volta Electromotive An 

electromotive force produced by means of 
the voltaic cell. (See Cell, Voltaic?) 

Forces, Electromotive, Complex-Har- 
monic Alternating The electromo- 
tive forces producing complex harmonic alter- 
nating currents. (See Appendix — Currents, 
Compiex-Ha rm on ic?) 



Forge, Electric 



A forge so ar- 



ranged that the metals to be subjected to 
forging can be electrically heated while in 
place on the forge. 

Formulae, Blavier's The formulae 

employed for computing the Blavier test. 
(See Appendix — Test, Blavier's.) 

Formulas. — Plural of formula. 

Four-Pole Dynamo-Electric Machine. — 

(See Appendix — Machine, Dynamo-Electric, 
Four-Pole?) 

Fourth State or Condition of Matter. — 

(See Appendix — Matter, Fourth State or 
Condition of.) 

Four- Way Switch. — (See Appendk — 
Switch, Four- Way.) 

Four-Wire System. — (See Appendix — 
System, Four- Wire.) 

Frame, Dynamo or Motor A term 

applied to the iron body of a dynamo or 
motor, including the pole pieces and stand- 
ards of the machine, but exclusive of the 
base plates and bearings. (See Machine,. 
Dynamo-Electric. Motor, Electric.) 

Frame, Trolley Base A frame for 

receiving the standard which supports the 
trolley pole. 

Franklinism. — A word sometimes em- 
ployed for franklinization. 

Franklinization would appear to be the prefer- 
able word. (See Franklinization.) 



Fre.] 



609 



[Gal 



Free or Insulated. — (See Appendix— Insu- 
lated or Free.) 

Frequencies, Harmonic Frequen- 
cies higher than the fundamental, present in 
complex-harmonic currents. (See Appen- 
dix — Currents, Coinplex-Harmonic) 

Frequencies, Tesla A term em- 
ployed for exceedingly high frequencies. 

The frequencies employed by Tesla amounted 
lo many hundreds of thousands per second. 

Frequency, Fundamental — The 

nominal or lowest frequency of a current 
which has harmonics. 

Frequency, Vibration —A term 

expressing the number of vibrations per 
second. 

In the case of a musical note the vibration fre- 
quency corresponds to the pitch of the note. 

Frog" Crossing. — (See Appendix — Cross- 
ing Frog?) 

Frost Alarm. — (See Appendix — Alarm, 
Frosty 

Full Contact. — (See Appendix — Contact, 
Full.) 

Full Load. — (See Appendix— Load, Full) 

Fundamental Frequency. — (See Appen- 
dix — Frequency, Fundamental) 

Fuse, Blowing of A term some- 
times employed for the fusing or volatiliza- 



tion of a fuse wire or safety plug. (See 
Fuse, Safety) 

Fuse, Blowing Point of The tem- 
perature or the current strength at which a 
fuse blows out or melts. 

The exact current strength at which a fuse 
blows out or melts varies, not only with the tem- 
perature of the wire, but also with the position, 
in which the fuse wire is placed in the fuse block,. 
and the nature of the block, its size, whether the 
current is direct or alternating, etc. 

The ratio, which should exist between the carry- 
ing capacity of a fuse, and the condition of its 
ultimate fusing, will of course depend on the 
character of the circuit the fuse is intended to 
guard. With small currents, such for example as 
are employed in electric lighting, a narrow margin, 
may be employed without detriment, but in the 
case of railway systems, however, a wider range 
is necessarily given to the blowing point of the 
fuse, for the amount of current required in such, 
systems, near heavy grades, is so much in com- 
parison to what is ordinarily employed that if 
too narrow a limit were given to the fusing point 
considerable annoyance would be experienced 
from the fuse blowing out too frequently. 

Fuse, Safety, Carrying Capacity of 

— The current strength a fuse wire or plug 
can carry without the line it protects becom- 
ing dangerously heated. 



G 



g. — An abbreviation proposed for one 
gramme, the C. G. S. unit of mass. 

g. cm 2 . — An abbreviation proposed for 
gramme centimetre squared, the C. G. S. unit 
of moment of inertia. 

Galvanic Cell. — (See Appendix — Cell, 
Galvanic) 

Galvanic Chain. — (See Appendix — Chain, 
Galvanic) 

Galvanic RiDg.— (See Appendix— Ring, 
Galvanic) 

Galvanist.— One skilled in the "art of 
galvanism." (Obsolete.) 



The word has no precise meaning, since the 
word galvanism is employed in two entirely dif- 
ferent senses ; namely, as current electricity and 
as a particular method of applying electricity to 
the curing of diseases. 

Galvanoglyphy. — The process of produc- 
ing an electrotype. 

This word, though good etymologically, is un- 
necessary ; moreover, the word electrotype is 
almost universally employed. 

Galvanography. — A term proposed for 
the copying of fine engravings on copper or 
steel plates by means of electro-deposition. 

Galvano-Magnetic. — A word proposed for 
electro-magnetic. 



Gal.] 



610 



[G n, 



The use of this word is unwarranted and should 
not be encouraged. 

Galvanometer, Angle of Maximum Sensi- 
tiveness of The angle of deflection at 

which a given small alteration in the strength 
of the current produces the greatest change 
in the deflection of the needle. 

Galvanometer, Direct Reading" 

A galvanometer in which the absolute value 
of the deflection in current strength is ob- 
tained directly without the use of tables or 
curves. 

Galvanometer, Helmholtz — A 

double-ring tangent galvanometer, the two 
ring coils of which are parallel to each other 
and are placed on opposite sides of the mag- 
netic needle at such positions that their mag- 
netic field at the needle may be as nearly 
uniform as possible, and much more nearly 
uniform than a single coil could produce. 

Galvanometer, Optical A form of 

galvanometer proposed by Potier based on 
the magnetic rotary power of liquids. (See 
Refraction, Double, Electric?) 

Galvanometer, Pocket A galvan- 
ometer small enough to be readily carried in 
the pocket. 

Galvanometer Voltmeter. — (See Appen- 
dix — Voltmeter, Galvanometer.) 

Galvanotonus. — A term proposed by 
Pfluger for the state of tetanus produced in a 
muscle that has been overstimulated electri- 
cally. 

Galvanotropism. — Movements produced 
in living organisms by the passage of elec- 
tricity through them. 

The word galvanotropism has been proposed 
to describe such phenomena as the movements 
observed in the roots of plants, when placed be- 
tween two opposite electrodes. The direction of 
these movements seems to be such as would place 
the longer axis of the root in the direction of the 
plane of the current. 

Gap, Air, Shunting An air gap in 

a circuit placed around a galvanometer or 
other instrument for the purpose of affording 
protection to the galvanometer or other instru- 
ment from the effects of powerful disruptive 
discharges. 



The inductive resistance of the coil to the 
rapidly varying oscillatory discharges is so great 
that the discharges take instead a path through 
an air gap. Since such an air gap thus shunts the 
discharge from the galvanometer or other coils, it 
is called a shunting air gap. 

Gas Cell. — (See Appendix— Cell, Gas.) 

Gas Polarization. — (See Appendix — Po- 
larization, Gas.) 

Gauge, Electric Pocket A gauge 

for an electric battery or other similar source 
small enough to be readily carried in the 
pocket. 

Gauge, Electroscopic A term ap- 
plied by Gaugain to a form of discharging 
gold-leaf electroscope. (See Electroscope, 
Gold-Leaf.) 

Gauss, Proposed A. I. E. E. Definition for 

A practical unit of magnetic intensity* 

the value of which is equal to one C. G. S. 
unit; that is, one C. G. S. line per square 
centimetre. 

This unit is a modification of that proposed by 
a Sub-Committee of the American Institute of 
Electrical Engineers on the Provisional Pro- 
gramme for the International Electrical Con- 
gress, held in Chicago, 1893, on the occasion of 
the World's Columbian Exposition. 

Generator, Chemical, of Electricity 

— A term sometimes employed in place of a 
voltaic pile or battery. 

This use of the term generator is sanctioned by 
the similar use of the word in other connections. 
Of course it will be understood that it is difference 
of potential and not electricity that is generated. 

Generator, Biphase A generator 

which delivers two-phase or diphase currents. 

Generator, High- Voltage Electro-Mag- 
netic An electro-magnetic generator 

arranged so as to give a high electromotive 
force. 

Generator, Polyphase A gener- 
ator which delivers more than single-phase 
currents. 

The term polyphase is frequently employed 
only in the sense of greater than diphase. 

Generator, Railway A dynamo- 



Gen.] 



611 



[Gro. 



electric machine which develops the current 
employed in systems of electric railways. 

Generator, Self-Compounding Polyphase 

— A polyphase generator whose field 

magnets are compound-wound. 

Generator, Thermo-Electric —A 

term sometimes employed for a thermo-elec- 
tric pile. (See Pile, Ther mo-Electric?) 

The term is equally applicable to the pyro- 
magnetic generator. 

Generator, Three-Phase A tri- 

phase generator. (See Appendix — Gener- 
ator, Tri-Phase.) 

The term tri-phase generator would appear to 
be preferable. 

Generator, Tri-Phase A generator 

which delivers three-phase or tri-phase cur- 
rents. 

Generator, Two-Phase A di-phase 

generator. (See Appendix — Generator, Di- 
Phase.) 

The term di-phase generator would appear to 
be preferable. 

Gilbert. — A term proposed for the prac- 
tical unit of magneto-motive force. 

A unit of magneto-motive force having 
the value of the absolute unit or equal to 

10 

— ampere-turn. 

This unit is a modification of that proposed by 
a Sub-Committee of the American Institute of 
Electrical Engineers on Provisional Programme 
for the International Electrical Congress, held 
in Chicago, in 1893. 

Gilding 1 , Electro Electric gilding. 

Electro-plating with gold. (See Gilding, 
Electric.) 

Glass Screw Insulator. — (See Appendix — 
Insulator, Glass- Screw?) 

Globes, Diffusing, for Electric Lights. 

Globes so constructed as to insure 

a diffusion of the light. 

The diffusion is generally obtained by means 
of ground glass. In order to avoid the loss of 
light that attends the use of ground glass, diffusion 
globes have been made of clear glass furnished 
with a number of refraction or total internal re- 



flecting lenses, in the manner of the well-known 
Fresnel lens. 



Glory, Aurora 



-A term proposed 



by Nordenskjold for an almost constant 
crown of light, single, double or multiple, 
which occupies a nearly fixed position in the 
heavens. 

Nordenskjold describes the aurora glory as fol- 
lows: 

" Our globe, even during a minimum aurora 
year, is adorned with an almost constant crown 
of light, single, double, or multiple, whose inner 
edge was usually, during the winter of 1878-79, 
at a height of about 0.03 of the radius of the 
earth (120 miles) above its surface, whose surface 
was somewhat under the earth's surface, having 
its centre a little north of the magnetic pole, and 
which, with a diameter of about 0.32 radius of 
the earth (about 1,280 miles), extends in a plane 
perpendicular to the earth's radius which passes 
through the centre of this luminous ring. " 

Glow, Fire A term employed by 

the ancients for an aurora. (See Aurora 
Borealis. Aurora Australis.) 

Glow Illumination. — (See Appendix — 
Illumination, Glow?) 

Glow Lamp. 

Glow?) 



-(See Appendix — Lainp, 



Glowing of Electric Conductor. — (See 
Appendix — Conductor, Electric, Glowing of.) 

Glue-Pot, Electric An electrically 

heated glue-pot. 

An electric heater is applied to a glue -pot of 
ordinary construction. (See Heater, Electric.) 

Gnomon, Electric A term formerly 

applied to a variety of pith ball electrometer. 

Good Earth. — (See Appendix — Earth, 
Good.) 

Ground Coil. — (See Appendix — Coil, 
Ground?) 

Ground, Dead A term sometimes 

applied to a fault or interruption in a tele- 
graphic line in which the escape to earth or 
ground is so great that it is impossible to 
operate the line. 

Dead earth. (See Earth, Dead or Total?) 

Grounding. — A word sometimes employed 



Gro.] 



612 



[Har, 



n electro-metallurgy for a preparatory pro- 
cess in burnishing. (See Appendix— Bur- 
nishing^) 

Grouping System for Electric Light 
Leads. — (See Appendix — Leads, Grouping 
System for Electric Light) 

Guard, Automatic, for Series-Connected 

Incandescent Lamps A device placed 

on each series-connected incandescent elec- 
tric lamp for the purpose of short circuiting 



the holder should the lamp filament break. 
A film cut-out. (See Cut-Out, Film.) 
An automatic guard may consist of a sheet of 

paraffine paper placed between two metallic 

knobs. 

Gyroscope, Electro-Magnetic A 

gyroscope driven by an electro-magnet. 

Gyrostatic Action of Dynamos on Ship- 
board. — (See Appendix — Action, Gyrostatic, 
of Dynamos on Shipboard) 



H. — A symbol used for field intensity. 

F 
The defining equation is H = — 

Here F = the force and m the strength of the 
pole. 

H. — An abbreviation proposed for henry, 
the practical unit of mutual induction, self- 
induction, or inductance. 

This abbreviation is seldom used. 

h. — An abbreviation for hour, one of the 
practical units of time. 

IK:.— A symbol proposed for magnetizing 
force. 



-Get- 



The defining equation is $£ 



_ 4 7TNI 



Where N, is the number of windings, and L, 
the length of the solenoid generating the mag- 
netizing force. 

HP or H\~A contraction for horse-power. 

This contraction is universally employed in all 
English-speaking countries. 

Harmonic Frequencies. — (See Appendix 
— Frequencies, Harmonic) 

Harmonic Motion.— (See Appendix — Mo- 
tion, Harmonic) 

Harmonic Telegraph.— (See Appendix — 
Telegraph, Harmonic) 

Harmonics, Electrical —A term 

sometimes employed in place of the upper 
harmonic currents generally. (See Appen- 
dix — Currents, Complex-Harmonic) 

Harmonics of Current— (See Appendix— 
Current, Harmonics of) 



Harmonics, Weeding-Out of — 

ting rid of, or removing some or all of the 
upper harmonic currents from a funda- 
mental harmonic current. 

The weeding-out process is generally effected 
by means of electric resonance. The presence of 
self-induction or capacity in the circuit has the 
same effect. It is partly on this account that we 
cannot yet speak across the Atlantic cable, the 
upper harmonics of the voice being weeded out 
more than the lower and made to lag more. 
(See Appendix — Harmonics, Weeding -Out of ] by 
Electrical Resonance. ) 

Harmonics, Weeding-Out of, by Electri- 
cal Resonance The weeding-out of 

the upper harmonics of a complex-harmonic 
current by altering the natural period of the 
system until it is in unison or in resonance 
with the fundamental harmonic. 

"A resonant circuit," says Pupin, "behaves 
towards a complex-harmonic electromotive force 
just the same as an acoustic resonator toward a 
source of complex sound. It brings out prom- 
inently that harmonic with which it is in reso- 
nance. To express this numerically, say that 
the ratio of the amplitude of the fundamental har- 
monic electromotive force to that of the next 
higher harmonic (supposing it to be even no 
higher than an octave) is 2 to 1. Then the cir- 
cuit can be easily brought into resonance with 
the fundamental harmonic in such a way as to 
increase the ratio of the amplitudes of the cor- 
responding simple harmonic currents 60 : 1. The- 
oretically (and to a great extent practically also) 
that ratio can be made anything we please by in- 
creasing continually the coefficient of self-indue- 



Hiir.] 



61< 



[Her 



tion and diminishing the capacity without de- 
stroying the resonance. In other words, we can, 
by the proper single tuning, weed out the upper 
harmonics as much as we please. B^t, as will be 
indicated later on, it is not always advisable to 
avail ourselves too much of a means of weeding 
out the upper harmonics by using very large self- 
induction. The best method of tuning depends 
on the nature of the problem before us." 

Harpoon, Electric A harpoon con- 
taining a bomb, that is electrically fired or 
exploded by the harpooner after imbedding 
the harpoon. 

Heat, Electrical Equivalent of A 

quantity representing the electrical energy 
produced by the action of a given amount or 
quantity of heat energy. 

Heater, Coil, Electric An electric 

heater in which 
the heat is pro- 
duced by the pas- 
sage of an electric 
current through a 
coiled metallic rib- 
bon. 

A form of coil 
heater is^ shown in 
Fig. 573- 

Heater, Pri- 
mary Electric 

A term 

proposed for the 
main electric heat- 
er in a building. 
(See Heater, Elec- 
tric^) 

Heeling Error 




Fig. 57 3' C°il Heater. 



of Mariner's Compass.— (See Appendix — 
Error, Heeling, of Mariner s Compass. 

Helix. — A word sometimes used in elec- 
tricity and magnetism in place of coil or sole- 
noid. (See Coil, Electric?) 

Helix, Anomalous —A helix so 

wound as to produce an anomalous magnet. 
(See Magnet, Anomalotis) 

Helix, Left-Handed A term some- 
times employed in place of a left-handed 



solenoid. (See Solenoid, Left-Handed. 
Solenoid, Practical.) 

Helix, Magnetic — A coil that is 

rendered magnetic by the passage through it 
of an electric current. (See Coil, Electric.) 

Helix, Magnetizing* A magnetiz- 
ing coil. (See Coil, Electric.) 



Helix, Right-Handed 



-A term 



sometimes employed in place of right-handed 
solenoid. (See Solenoid, Right-Handed. 
Solenoid, Practical?) 

Helmholtz Galvanometer. — (See Appen- 
dix — Galvanometer, Helmholtz?) 

Henry, International The value 

of the international henry adopted by the 
Chicago Congress of 1893, as equal to the 
induction in a circuit when the electromotive 
force induced in this circuit is one interna- 
tional volt, while the inducing current varies 
at the rate of one ampere per second. 

Henry, Proposed A. I. E. E. Definition 

for The name adopted by the Elec- 
trical Congress of 1893 for the practical unit 
of inductance. 

A unit of inductance having the value of 
io 9 absolute units, or nearly the length of an 
earth's quadrant. 

This name was proposed by a Sub-Committee 
of the American Institute of Electrical Engineers 
on Provisional Programme of the International 
Electrical Congress, in Chicago, 1893, on the occa- 
sion of the World's Columbian Exposition. 

This name was adopted by the said Inter- 
national Electrical Congress in August, 1893, with 
the following definition : 

A henry is the induction in a circuit when the 
electromotive force induced in this circuit is one 
international volt, while the inducing current 
varies at the rate of one international ampere per 
second. 

Heptad Atom. — (See Appendix — Atom, 
Hefitad.) 

Hertz's Axial Oscillator.— (See Appen- 
dix — Oscillator, Hertz s Axial.) 

Hertz's Linear Oscillator. — (See Appen- 
dix — Oscillator, Hertz s Linear) 

Hertz's Oscillator. — (See Appendix—' 
Oscillator, Hertz's.) 



Ber.] 



614 



[ML 



Hertzian Wares.— (See Appendix— 
Waves, Hertzian.) 

Heterostatic Electrometer. — (See Appen- 
dix — Electrometer, Heterostatic) 

Hexad Atom. — (See Appendix— Atom, 
Hexad.) 

High-Frequency Transformer. — (See Ap- 
pendix — Transformer, High-Frequency?) 

High- foltage Electro-Magnetic Gener- 
ator. — (See Appendix — Generator, High- 
Voltage Electro-Magnetic.) 

Home Battery.— (See Appendix— Battery, 
Home) 

Hook, Dipping A metallic hook 

provided for holding articles that are to be 
cleansed, in order to prepare them for electro- 
plating by subjecting them to the dipping 
process. (See Dipping) 

The dipping hook should be made of metal as 
nearly resembling the article to be plated as pos- 
sible, so as thereby to prevent voltaic action tak- 
ing place between the two metals with a conse- 
quent marking at the points of contact. 

Horizontal Intensity of Earth's Magnet- 
ism. — (See Appendix — Magnetism, Hori- 
zontal Intensity of Earth's) 

Horology, Electric That branch of 

electric science which treats of the applica- 
tions of electricity to the regulation or opera- 
tion of clocks. (See Clock, Electric) 

Hummer. — A word sometimes employed 
in place of buzzer. (See Buzzer, Electric) 

Hummer, Electric A term some- 
times used for electric buzzer. 



Hunting of Parallel Alternators.— (See 

Appendix — Alternators, Parallel, Hunting 
of) 

Hysteresis, Dielectric A term pro- 
posed by Steinmetz for a variety of molecular 
friction, analogous to magnetic hysteresis, pro- 
duced in a dielectric under changes of electro- 
static stress. 

The losses caused by dielectric hysteresis are 
probably proportional to the frequency and to the 
square of the E. M. F., i. e., to the electrostatic 
field intensity. 

Losses ascribed to defective insulation are often, 
in the opinion of Steinmetz, caused, at least in part, 
by dielectric hysteresis. 

Hysteresis, Magnetic A variety of 

molecular friction produced in the molecules 
of a magnetizable substance during changes 
of magnetic stress. 

According to Steinmetz, the loss occasioned by 
magnetic hysteresis is proportional to the fre- 
quency and to the i.6th power of the magnetic 
variation. 

According to Steinmetz, for a magnetic cycle 
performed between the limits of magnetic induc- 
tion B x and B 2 , the loss in ergs per cubic cm. is 
B 2 \i.6 



-(S^) 1 



where n, the coefficient of hysteresis, averages 
.0033 in average good sheet iron, .013 in cast 
iron, .003 to .03 in cast steel, and reaches as high 
as .08 in hardened steel. 

With alternating magnetism the formula can 
be written 

L=nB 1 - 6 

The actual existence of magnetic hysteresis is 
denied by some able electricians. 



I. — A symbol proposed for intensity of 
current. 

The defining equation is I = ^ 

9 A symbol used in France and 

Germany for intensity of magnetization. 

c, _ 9TC 

The defining equation is 9 y— 



Idiostatic Electrometer. — (See Appendix 
—Electrometer, Idiostatic) 

Idle Wire of Armature. — (See Appendix 
— Wire, Idle, of Armature) 

Idle Wire of Armature of Motor.— (See 
Wire, Idle, of Armature of Motor) 

Idle Wire of Dynamo.— (See Appendix — 
Wire, Idle, of Armature of Dynamo) 



ML] 



615 



[In<L 



Idle Wire of Motor.— (See Appendix — 
Wire, Idle, of Arinature of Motor.) 

Illumination, Cosine Law of The 

intensity of the illumination emitted from or 
received by any element of surface is propor- 
tional to the cosine of the angle between its 
normal, and the direction of the radiation. 

Illumination, Glow A term pro- 
posed for an illumination similar to that of 
the glow-worm ; that is, illumination without 
sensible heat. 

All artificial sources of light, such, for example, 
as a coal-oil lamp, a gas jet, an incandescent elec- 
tric lamp, or an arc lamp, contain a much greater 
percentage of non-luminous than of luminous 
radiation, that is, of heat than light, being at the 
most a few per cent, of light, and considerably 
over 95 per cent, of heat. 

The most economical artificial lighting is, of 
course, impossible under these circumstances. 

In the light emitted by a firefly or a glow 
worm, practically all the radiation consists of 
light or radiation within the limits of visibility. 

The term glow illumination has been proposed 
for illumination by light such as is furnished by a 
firefly or glow-worm; viz., for the light emitted 
by any source which is capable of producing 
luminous radiation only. In some forms of Tesla 
lamps the illumination closely approaches glow 
illumination. 

Immediate False Zero. — (See Appendix 
— Zero, Immediate False.) 

Incandescent Bombardment Lamp. — 
(See Appendix — Lamp, Incandescent Bom- 
bardment.) 

Incandescent Filament. — (See Appendix 
— Filament, Incandescent.) 

Incandescent Lamp Cord. — (See Appen- 
dix — Cord, hicandescent Lamp.) 

Incandescent Lighting' Dynamo-Electric 
Machine. — (See Appendix — Machine, Dy- 
namo-Electric, Incandescent Lighting.) 

Incandescing Filament. — (See Appendix 
— Filame?it, Incandescing. ) 

Inclination Magnetometer. — (See Appen- 
dix — Magnetometer, Inclination.) 

Indicator, Disc, Mechanical Replacement 
Of Such a replacement or resetting of 



a disc, arm, shutter or semaphore of an indi- 
cator as must be done by hand. 

A non-automatic replacement of an indi- 
cator disc. 

Indicator, Fall-Back A term some- 
times employed in place of drop indicator. 

Indicator, Light, of Railroad Signal 

A device by means of which an indi- 
cation is given as to whether a signal lamp is 
lighted or not. 

The light indicator is operated by means of a 
metallic bar, which increases in length by means 
of the heat of the lamp when lighted. 

Indicator, Polarized A term some- 
times employed for an indicator provided 
with a polarized armature. 

Indicator, Pole An apparatus em- 
ployed for readily determining whether the 
poles of a dynamo battery or other source 
are positive or negative. 

A convenient form of pole indicator consists of 
a small electrolytic cell filled with a solution of a 
metallic salt. On the passage of the current 
through the electrolyte the character of the poles 
is readily determined by the change in color of 
the liquid adjacent to one pole of the indicator. 

There are other well-known forms of pole in- 
dicators. 



Indicator, Tele 



-A term sometimes 



employed in place of telemeter. (See Telem- 
eter^) 

Indicator, Telephone An indi- 
cator employed on a telephone circuit to indi- 
cate the number of the correspondent calling. 
(See Indicator, Electric?) 

A telephone indicator, as generally constructed, 
consists of some form of mechanical drop oper- 
ated by the attraction of the armature of an 
electro-magnet which, permitting the fall of a 
drop or shutter, exposes the particular number of 
the correspondent calling. 

Indicator, Tri-Polar An electro- 
magnetic indicator, with three poles. 

A straight- bar magnet is employed, one end of 
which forms one pole and the other end is con- 
nected with a U-shaped piece of soft iron, so as 
to bring the two free ends of the latter up to the 



Ind.1 



616 



[Ind. 



line on the other pole. There are thus produced 
three poles; hence, the name, tri-polar. 

Indifferent Point. — (See Appendix — 
Poi?it, Indifferent?) 

Individual Signal. — (See Appendix — 
Signal, Individual?) 

Individual Signaling Apparatus. — (See 
Appendix — Apparatus, Individual Signal- 
ing. 

Induced Electric Surgings.— (See Appen- 
dix — Surgings, Induced Electric?) 

Induced Single-Needle Dial. — (See Ap- 
pendix — Dial, Induced Single-Needle?) 

Inductance, Mutual, Proposed A. I. E. E. 
Definition for The mutual induc- 
tance of one electric circuit upon another is 
the ratio of the total magnetic induction 
linked with the second, due to a uniform cur- 
rent in the first, to the strength of that 
current. 

The mutual inductance between two electric 
circuits is reciprocally equal when the environ- 
ing medium has constant inductivity. 

The C. G. S. unit of mutual inductance is one 
centimetre; the practical unit of self-inductance 
is one henry. 

The following modification of the definition 
would appear to be preferable, viz. : the mutual 
inductance of one circuit on another is the ratio 
of the sum of the linkages of lines of magnetic 
induction with the second, due to a uniform cur- 
rent in the first, to the strength of that current. 

Inductance, Non-Ferric A term 

proposed to distinguish an inductance in 
which no iron or magnetic metal enters. 

A coil of copper forms a non-ferric inductance ; 
the insertion of an iron core into the coil makes 
it become a ferric inductance. 

Inductance, Self, Proposed A. I. E. E. 

Definition for The ratio of the total 

magnetic induction, linked with and estab- 
lished by an electric current, to the uniform 
strength of the same. 

The inductance of a conducting circuit is con- 
stant when its environing medium has constant 
inductivity. A modification has been proposed 
for this definition similar to that proposed for 
mutual inductance. 



Inductance, Specific A term pro- 
posed for the comparative value of induc- 
tance. (See Inductance.} 

Inductance Speed. — (See Appendix — 
Speed, Inductance?) 

Inducteous Body. — (See Appendix— Body, 
Inducteous.) 

Induction, Auto A term sometimes 

employed instead of self-induction. (See In- 
duction, Self.) 

Induction, Backward, of Dynamo Arma- 
ture The component of the armature 

magnetization opposing the magnetization of 
the field magnets. (See Appendix— Induc- 
tion, Cross, of Dynamo Armature?) 

Were there no forward lead given to the 
brushes, there would be no back induction ; there 
would, however, be cross induction. 

Induction, Cross, of Dynamo Armature 

A term sometimes employed in place 

of the induction produced in the armature of 
a dynamo-electric machine from the ampere 
turns acting across the main magnetic cir- 
cuit, i. e., those due to the current in the 
armature, and is the lead of the brushes 
tending to produce magnetic poles crosswise 
to the regular poles of the machine. 

Induction, Magne-Electric A term 

formerly employed for magneto-electric in- 
duction. (See Induction, Magneto-Electric?) 

Induction, Magnetic, Terrestrial 

The production of magnetism by the action 
of the earth's magnetic field. 

Induction Motor. — (See Appendix — Mo- 
tor, Induction?) 

Induction Telegraph. — (See Appendix — 
Telegraph, Induction?) 

Inductivity.— A word proposed for spe- 
cific inductance. (See Appendix — Induct- 
ance, Specific?) 

Inductivity, Proposed A. I. E. E. for 

: The inductivity at any point in an 

isotropic medium is the ratio added to unity 
of 4 it times the intensity of the magnetiza- 
tion there existing to the magnetizing flux 
density. 



Ind.] 



617 



[Int. 



The ratio of the flux density to the mag- 
netizing force. 

The conventional symbol is jit and it is synony- 
mous with permeability. 

Inductric Body. — (See Appendix — Body, 
Inductric) 

Influence, Electrostatic A word 

sometimes employed in place of electro- 
static induction. (See Induction, Electro- 
static?) , 

There would appear to be no real necessity 
for the abandonment of the term induction for 
the effects produced by an electrostatic field. 
The general similarity of the phenomena would, 
indeed, appear to render it advisable to retain 
the word electrostatic induction, to show its close 
relation to electro-magnetic induction. 

In-Put. — The energy absorbed by a ma- 
chine in driving it or causing it to perform a 
certain amount of work. 

This word is used in contradistinction to out- 
put. 

Inside Box Brush. — (See Appendix— 
Brush, Inside Box.) 

Instrument, S.*N., Telegraphic A 

contraction employed for single-needle tele- 
graphic instrument. 

Insulated or Free A term em- 
ployed in telegraphy. 

A wire is said to be free insulated when it is 
disconnected from its apparatus and left insu- 
lated. 

Insulation, Kilometric, of Cable 

The insulation of a cable measured in kilo- 
metre-megohms or the average insulation of 
one kilometre in megohms. 

Insulation Lightning 1 Protection.— (See 

Appendix — Protection, Insulation Light- 
ning.) 

Insulation Lightning Protector. — (See 
Appendix — Protector, Insulation Light- 
ning^ 

Insulator, Glass-Screw A glass in- 
sulator provided with a screw thread inside 
the glass for the purpose of ready attach- 
ment to the insulator pin. 

Insulator, Shackle A term some- 
times employed for any form of shackle in- 



sulator. (See Insulator, Single-Shackle. 
Insulator, Double-Shackle.) 

Insulator, Tree A variety of insu- 
lator suitable for attachment to trees, and 
designed so as to keep the conductor from 
being brought into contact with the branches. 

The insulator -proper is mounted on a shaft 
which plays in a ball and socket joint, the cup 
of which is fastened to the tree ; the line is there- 
fore kept in its normal position despite the move- 
ments of the tree. 

In-Take. — A word sometimes used in place 
of In-Put. 

Intensity of Radiation. — (See Appendix— 
Radiation, Intensity of.) 

Interference, Acoustic Interfer- 
ence of sound waves. 

The term acoustic interference is employed in 
contradistinction to luminous interference. 

Interference, Electro-Magnetic A 

term sometimes employed for the interference 
of electro-magnetic waves. 

The term electro-magnetic interference is em- 
ployed in contradistinction to acoustic or lumi- 
nous interference, even though it be granted that 
luminous waves are electro- magnetic waves. 



-A term 



Interference, Luminous — 

sometimes employed for the interference of 
light waves. 

The term luminous interference is used in 
contradistinction to acoustic or electric inter- 
ference. 

Internal Magnetic Circuit. — (See Ap- 
pendix — Circuit, Magnetic, Internal.) 

Internal Magnetic Field. — (See Appen- 
dix— Field, Magnetic, Internal) 

International Ampere. — (See Appendix 
— Ampere, International) 

International Coulomb.— (See Appendix 
— Coulomb, International) 

International Farad.— (See Appendix — 
Farad, International) 

International Henry. — (See Appendix — 
Henry, International) 

International Joule. — (See Appendix — 
Joule, International) 



Int.] 



618 



[Int. 



International Morse Code.— (See Appen- 
dix — Code, International Morsel) 

International Ohm. — (See Appendix — 
Ohm, International.) 

International Yolt. — (See Appendix — 
Volt, International.) 

International Watt. — (See Appendix — 
Watt, International.) 

Interrupter, Electro-Dynamic A 

name proposed by Pupin for an interrupter for 
the primary circuit of an induction coil con- 
sisting of an elastic wire stretched like the 
wire of a sonometer or monochord between 
the poles of a permanent horseshoe magnet. 

The term sonometer interrupter might, per- 
haps, be more descriptive of the apparatus em- 
ployed. 

The circuit connections are such that when the 
wire is set into vibration these vibrations are con- 
tinued under the action of the field produced by 
the magnet. The construction and operation of 
an electro-dynamic interrupter are given by its 
inventor, Pupin, as follows : 

"In the meantime experience suggested the 
form given in Fig. 574 as best suited to the pur- 
pose for which the interrupter was first de- 
signed. The diagram of Fig. 575 explains the 

m 




Fig. 57 4> 



. rr^fi" 



i3S 



Fig. 575- 
construction of the apparatus more clearly. A 
stout aluminium, or phosphor-bronze wire, the 
vibrator, is stretched between the pole pieces d 
and e, of two permanent Weston magnets, such 
as this distinguished electrician uses in his 
voltmeters. 

"Fig. 576 gives the front view of one of the 
magnets. The cross-section of the vibrator is 
seen there between the pole pieces N, S, as a black 
dot. The short line a b extending from the vi- 
brator to the mercury cup below is the dipper, a 
short, thin, amalgamated copper wire, which is 
soldered to the vibrator. The vibrator rests on 




two hard rubber bridges f g. One of its ends is 
rigidly attached to the wooden frame of the 
apparatus, the other end is attached to a lever h, 
which, worked by a micrometer screw, varies 
the tension of the vibrator. 
There are three mercury 
cups, a, b, c, and three 
dippers (which unfortun- 
ately do not appear in Fig. 
574). The middle cup b, is | 
fixed in position, and the 
middle dipper, being at the 
nodal point of the vibrator, 
makes a permanent contact 
there. The other two dippers make contact with 
mercury cups which can be raised or lowered by 
means of a nut and screw as represented in Fig. 
574, and indicated in diagram 575. The con- 
struction of the adjustable mercury cups and the 
stretching lever were copied from Dr. Max Wien's 
magnetic interrupter (Wiedem. Ann. 1891 and 
1892). The middle cup (see Fig. 577) is connected 
to one pole, F, of the gravity or storage cell, the 
other two cups are connected one to one end and 
the other to the other end of the primary of the 

& 5K rtu. Aq <& 



Fig. 57 1>- 




Fig. 577- 
small coil A B. From the middle point, C, of the 
primary a wire leads to the other pole of the cell. 
Auxiliary small coils, E and D, and condensers, 
H and G, are inserted in the circuits as indicated. 
Their functions will be explained further below. 

"The vibrator vibrates with a node at the 
middle dipper as soon as the tension has reached a 
certain, by no means high, limit. A permanent 
contact is therefore maintained at this point, and 
the contact is made at one of the cups just at 
about the same moment as it is broken at the 
other cup. Leaving the condensers out of con- 
sideration for the present, it is evident that this 
form of the current make-and-break produces 
the same effect upon the iron core of the coil as 
an alternating current would. The advantage of 
this needs no comment ; but although the iron 
core consists of the finest iron wire that can be 
obtained in the market, yet it must be remem- 



Int.] 



619 



[ISO. 



bered that the vibrator is expected to work some- 
times at the rate of 512, or more, complete periods 
per second. Another immediate advantage 
which this interrupter offers is a considerable 
diminution of sparking. The addition of con- 
densers, besides performing other functions 
which will be discussed presently, reduces the 
break sparks almost to invisibility, even when 
currents as large as half of an ampere are used. 
Each half of the primary coil consists of 532 turns 
of No. 22 silk-covered wire wound over an iron 
core of 30 centimetres in length, 4 square centi- 
metres in cross-section, and consisting of very 
fine, soft iron wire." 

Interrupter, Sonometer A term 

sometimes employed in place of electro- 
dynamic interrupter. (See Appendix — In- 
terrupter, Electro-Dynamic^) 

Interrupter, Telegraphic A de- 
vice for making and breaking a circuit at a 
definite rate. 

A telegraphic key or other analogous de- 
vice. 

Interrupter, Telegraphic, Mechanical 

A form of mechanical telegraphic 

sounder for learners in which no battery is 
required. 

A mechanical telegraphic interrupter is pro- 
vided with a full-size key with a full set of adjust- 
ments. In fact, it resembles an ordinary key, 
except in that it requires no battery to operate it. 
It differs, therefore, from the snapper sounder, 
which is not intended to resemble a sounder, but 
merely to give the sounds of the Morse characters 
with the simplest mechanism. 

Interruption, Telegraphic A term 

sometimes employed in telegraphy for faults 
in general. 

According to Pope, telegraphic faults or inter- 
ruptions arise from the following causes, viz.: 

(1.) Disconnections or breaks. 

(2.) Partial disconnections or resistance. 

(3.) Escapes. 

(4.) Crosses. 

Ions, Migration of A term em- 
ployed to express the movement of the ions 
in an electrolyte during electrolysis. 

The hypothesis of Grothuss attempts to explain 
the fact that in electrolysis the anions and kathions 
do not appear in any part of the electrolyte ex- 



cept at the electrodes, no ions apparently being 
set free in the liquid. (See Hypothesis, Grdthtiss' . ) 

When copper electrodes are employed in the 
electrolysis of a solution of copper sulphate, the 
solution becomes from two to three times weaker 
at the kathode than at the other electrode. 
Hittorf explains this fact on the assumption that 
during the migration the SO4 radical moves, 
through the liquid more rapidly than the Cu 
radical. 

Grothuss' hypothesis has been objected to be- 
cause it requires a finite force to bring about the 
decomposition of the electrolyte, and the experi- 
ments of Helmholtz prove that the interior of an 
electrolyte is unable to withstand the slightest 
electrostatic stress. Clausius has modified Grot- 
huss' hypothesis so as to bring it more into 
accord with the kinetic theory of matter. He 
believes that some of the moving molecules of the 
electrolyte are broken up into their constituent 
ions as a result of occasional molecular impact, 
and that it is these separated ions only that appear 
at the electrodes. Arrhenius asserts that during 
electrolysis the greater part of the molecules of 
the electrolyte are thus dissociated. The veloc- 
ity of the dissociated ions is assumed to be pro- 
portioned to the potential gradient in the elec- 
trolyte. According to this theory a continuous 
movement of positively charged ions occurs 
towards the negative electrode or kathode and of 
negatively charged ions towards the positive 
electrode or anode. 

Iron, Building A heated iron tool,. 

by means of which the mould impressed by 
the printed page, it is desired to electrotype, 
is built up preparatory to being placed in the 
electroplating bath. 

A building iron consists essentially of a suitably- 
shaped iron tool which is employed while hot in 
connection with strips of wax for bringing up or 
raising the blank spaces in a mould between the 
pages and paragraphs. 

Iron-Loss in Transformer. — (See Ap- 
pendix — Tratisformer, Iron-Loss in.) 

Isonisation. — A term proposed for a de- 
crease in the strength with which the separate 
atoms or radicals are held together in the 
molecules of an electrolyte. 

A term proposed for that modified dis- 
sociation of a molecule which consists in a 



Iso.] 



620 



[Key. 



weakening of the force which holds the ions 
of the molecules together in an electrolyte. 

The term isonisation does not, as might be 
supposed, refer to the complete separation of an 
electrolyte into its ions by electrolysis, but to a 
preparatory weakening of the bonds which hold 
the ions together in a solution in which elec- 
trolysis is about to occur. 



This term was proposed by Fitzgerald for the 
purpose of covering the peculiar action of elec- 
trolysis so far as its behavior to aqueous solutions 
of metallic salts is concerned. 

Isotropic— Homogeneous with respect to 
direction. 

Employed in reference to the properties of a 
medium. 



Jack Switch. — (See Appendix— Switch, 
Jack) 

Jar, Leyden, Overflow of A term 

sometimes employed for the discharge of a 
Leychn jar by a disruptive discharge around 
its edge. 

Joint, End-to-End A term fre- 
quently employed in place of butt joint. (See 
Joint, Butt) 

Joint, Sliding An expansion joint. 

(See Joint, Expansion) 

Joule, International The value 

of the international joule adopted by the Chi- 
cago Congress of 1893, as equal to io 7 units 
of work in the C. G. S. system, and which is 



represented sufficiently well for practical use 
by the energy expended in one second by one 
international ampere in an international ohm. 

Joule-Meter. — Any apparatus capable of 
measuring energy in joules. 

An energy meter as distinguished from a 
watt-meter. 

Juniper. — A temporary shunt or circuit put 
around a lamp or loop on a series circuit, to 
enable it to be readily removed or repaired. 

A jumper usually consists of a piece of wire of 
sufficient size to carry the current past the faulty 
lamp or other device which it is desired to tem- 
porarily remove or repair. 



K 



K. — A symbol for moment of inertia. 
The defining equation is M X L 2 ' 

K (Kappa). — A symbol proposed for mag- 
netic susceptibility. 

3 • 1 



The defining equation is K 



U l ' e 'H 



kg 1 . — An abbreviation for kilogramme, the 
practical unit of mass. 

kg: cm 2 . — An abbreviation proposed for 
kilogramme per square centimetre, the prac- 
tical unit of pressure. 

kgm. — An abbreviation for kilogrammetre, 
the practical unit of moment of a couple or 
of work. 

kgin: s. — An abbreviation proposed for 
kilogrammetre per second, the practical unit 
of power. 



KR. — A contraction for the total capacity 
of a telephone wire or conductor multiplied 
by its total resistance. 

KR Law. — (See Appendix — Law, The 
KR) 

Kapp Line. — (See Appendix — Line, 
Kapp) 

Karsten's Figures. — (See Appendix — 
Figures, Karsten's) 

Kathodic Rays of Vacuum Tube. — (See 
Appendix — Rays, Kathodic, oj Vacuum 
Tube) 

Kerite Tape. — (See Appendix — Tape, 
Kerite) 

Key, Break A key which breaks 

or opens the circuit when depressed. 



Key.] 



621 



[Lam. 



Key, Strap — A telegraphic key 

formed of a single plate of elastic material. 

The elastic strip of conducting material is 
fixed at one end. Its motion in one direction is 
effected by the hand of the operator, and its re- 
turn in the opposite direction by the elasticity of 
the material. 

Key, Successive Contact A key so 

arranged as to make or break one contact 
after another. 

A successive contact key is frequently used in 
connection with a Wheatstone bridge ; where it 
is desirable to make or close the battery circuit 
before making or closing the galvanometer cir- 
cuit, or to break the battery circuit after break- 
ing or opening the galvanometer circuit. This is 
done by means of a successive contact key. A 
successive contact key is also sometimes called a 
double contact key. (See Key, Double -Contact 
For??i of Bridge, Sprague's. Key, Double-Con- 
tact, La?nbert , s.) 

Key, Tapper A term sometimes 

employed in place of Morse tapper. (See 
Appendix — Tapper, Morse.) 



Kick of Relay. — A momentary effect, 
more powerful than usual, produced on the 
armature of a relay by the current of charge 
on the closing of the circuit. 

The kick varies in its amount or intensity not 
only with the electrostatic capacity of the line, 
but also with its length and with the perfection of 
its insulation. 

Kilerg. — A kilo-erg. 

Kilo-Erg 1 . — One thousand ergs. 

Kilo-Tolt.— One thousand volts. 

Kilometric Capacity of Cable. — (See 
Appendix — Capacity, Kilometric, of Cable?) 

Kilometric Insulation of Cable. — (See 
Appendix — Insulation, Kilometric, of Cable?) 

Kinematics. — That branch of mechanics 
which treats of motions, irrespective of the 
mass moved or the forces which produce or 
oppose its motion. 

Kinetics. — That branch of dynamics which 
treats of the action of forces in producing or 
modifying motion. 

Krizik's Cores.— (See Appendix— Cores, 
Krizik's.) 



L m . — A symbol proposed for co-efficient of 
mutual induction. 

L s . — A symbol proposed for co-efficient of 
self-induction or inductance. 

The defining equation is L s = y 

Lag, Translation A term proposed 

by Elihu Thomson, who defines it as follows : 
" Lag due to the traverse of a conductor con- 
veying current past a magnet pole, whereby 
the action of the current in that conductor 
becomes displaced in the direction of the 
motion and produces a moving field, the iron 
mass or body tending to accommodate itself 
to the direction of the lines of force in the 
moving field." 

The phenomena of a shifting field are observed 
when a coil with an iron wire core is energized 
by an alternating current so as to produce an 



alternating field, and a wheel made up of iron 
discs around which is a rim or band of copper 
overhanging the edges of the disc is placed in 
such field. On the energizing of the coil, the 
wheel, which is mounted on pivots, when 
mechanically started in rotation in either direc- 
tion, will increase both in speed and torque to a 
degree depending on the frequency of the current, 
the friction to be overcome on the alternating 
field and on the iron and copper of the wheel. 
(See Field, Magnetic, Shifting.) 

Lamp, Arc, Striking" Mechanism of 

— The mechanism in an arc lamp by means 
of which the carbons are separated to the 
distance at which it is desired the arc shall 
be maintained between them. 

Lamp, Bombardment, Electrical ^A 

lamp in which the light is produced in a 
vacuous space by means of the bombard- 



Lam.] 



622 



[Lawr 



ment of the molecules of the residual gas by 
the passage of electrical discharges. 

The molecules in their rapid to-and-fro motions 
are caused to strike against, and thus raise to in- 
candescence, strips or bars of refractory material, 
such as carbon, etc. 

Tesla's straight-filament incandescent electric 
lamp is a form of electric bombardment lamp. 
(See Lamp, Incandescent, Straight- Filament .) 

Lamp, Burned-Out Incandescent 

A term sometimes employed for an electric 
incandescent lamp which is no longer able 
to furnish efficient electric light. 

An incandescent electric lamp is, strictly speak- 
ing, to be regarded as burned out when it no 
longer furnishes a suitable light, and this, 
whether the filament or chamber has been 
actually destroyed or not. 

Lamp, Electric, Efficiency of — 

Strictly, the ratio of the luminous energy 
emitted by the lamp, to the energy absorbed 
by the lamp. 

The term efficiency of a lamp is less accur- 
ately used to signify its relative watts per candle 
power. The Edison lamps are of high efficiency 
if 3.1 watts per c. p., and of low efficiency if 
greater. 

Lamp, Electric Stopper A term 

nowgenerally em- 
ployed for an in- 
candescent elec- 
tric lamp in which 
the chamber is 
stopped, not as 
formerly by the 
fusion of the 
glass, but by the 
action of a glass 
stopper hermeti- 
cally sealed by 
the use of suit- 
able cement. 

Fig. 578 shows a 
lamp of this type. 

Lamp, Glow 

— A lamp 

the light of which is produced by glow 
illumination. (See Appendix — Illumination, 

Glow.) 




Fig. 578. Electric 
Lamp. 



The term glow lamp is already generally em- 
ployed in England and Germany for the ordinary- 
incandescent electric lamp. It would appear that 
the term incandescent lamp generally employed 
in America is preferable. The term glow-lamp 
should be limited, as above, to a lamp producing 
an approximately cold light ; namely, a lamp 
operating by glow illumination. 

Lamp, Incandescent Bombardment 

— An electric lamp in which a refractory 
material is rendered incandescent by the 
molecular bombardment produced by the 
passage of an electric discharge through a 
rarefied space. 

Most of Tesla's lamps are of the bombardment 
type and are of a great variety of forms, but in 
all of them refractory substances like carbon are 
rendered incandescent by the passage of very 
rapidly alternating currents through rarefied 
gases. (See Lamp, Electric, Incandescent Ball. 
Lamp, Incandescent, Straight Filament. ) 

Lamp, Incandescent Electric, Ageing* of 

A term sometimes employed for a 



gradual decrease in the economical light 
emitted by an incandescent electric lamp 
attending its continued use. 



Lamp, Phosphorescent 



-A lamp 



whose light is obtained by means of the phos- 
phorescent effects attending the discharges of 
electricity through a rarefied space. 

In phosphorescent lamps the phosphorescent 
effects are produced by causing the molecules ot 
the residual gas to strike against some readily 
phosphorescent material. Such lamps are some- 
times called bombardment lamps. But the term 
bombardment lamp is [perhaps more properly 
restricted to cases where molecular bombardment 
raises a substance of high refractory power, such 
as carbon, to incandescence ; while the term 
phosphorescent lamps is limited to cases where 
the material so raised to luminescence is a phos- 
phorescent material. (See Bombardment, Molec- 
ular.) 

Law, The KR. A generalization 

claimed by some as a law, but denied by 
most, which assigns a limit to the distance 
through which intelligible telephonic com- 
munication can be carried on to cases where 
the product of K, the capacity of the tele- 



Lea.] 



623 



[Lig. 



phone circuit, multiplied by R, its resistance, 
does not exceed a certain value. 

Preece originally fixed the limits of intelligible 
communication of speech by means of a telephone 
to cases where the product of K and R did 
not exceed 15,000. Preece's figures do not agree 
with the results of practical telephone work in the 
United States; such, for example, as in the case of 
the line now in actual operation between Boston 
and Chicago. 

Preece's general method of calculating the K 
R of a metallic circuit was by multiplying the 
total capacity of the line by its total resistance 
and then dividing by four, since the capacity of 
an insulated loop is taken as one-fourth of the 
capacity of the entire length of the line measured 
against the ground. Even when calculated in 
this way the K R of the Boston-Chicago con- 
ductor line is nearly 54,000. 

Lead Sulphate of Copper Cell.— (See Ap- 
pendix — Cell, Lead Sulphate of Copper) 

Lead Sulphate of Zinc Cell.— (See Ap- 
pendix — Cell, Lead Sulphate of Zinc) 

Leads, Double-Wire System for Electric 

Light A term employed for a parallel 

or multiple system of leads for electric light. 
(See Circuit, Parallel. Circuit, Multiple) 

Leads, Grouping- System for Electric 

Light A term sometimes employed 

for series-multiple circuits. (See Circuity 
Series-Multiple) 

Leads, Single Wire System for Electric 

Light A term sometimes employed for 

a circuit in which the current after passing- 
through the lamps is returned by means of 
the earth or ground. 

This is called the single wire system for electric 
light leads because but a single wire or con- 
ductor is employed in the circuit, the return being 
made through the ground or earth. 

Leak, Telegraphic, Resistance of 

The resistance offered by a leak in a tele- 
graphic line or circuit. 

Leakance. — A word proposed by Heavi- 
side for leakage conductance. 

It will be seen that the proposed word is an 
abbreviation or contraction for leakage-conduct- 



Lease, Way 



-A permit obtained from 



the owner of a property for the erection of 
poles or other attachments for telephonic or 
telegraphic lines. 

Left-Hand Trolley Switch.— (See Ap- 
pendix — Switch, Left-Ha7id Trolley) 

Left-Handed. Helix. — (See Appendix— 
Helix, Left-Handed) 

Left-Handed Rotation. — (See Appendix— 
Rotation, Left-Handed) 

Left-Handed Spiral. — (See Appendix — 
Spiral, Left-Handed) 

Lever Switch. — (See Appendix — Switch, 
Lever) 

Light, Castor and Pollux A term 

formerly used in place of St. Elmo's fire. 

Light Cell. — (See Appendix — Cell, Light) 

Light Indicator of Railroad Signal. — 
(See Appendix — Indicator, Light, of Rail- 
road Signal) 

Light Load. — (See Appendix — Load, 
Light) 

Light, Northern An aurora bore- 

alis. 

Lighting, Vacuuai-Tube Artificial 

illumination obtained by the passage of elec- 
tric discharges through vacuum tubes. 

A practical system of electric lighting by means 
of vacuum tubes was not long ago regarded as an 
impossibility ; now, however, through the labors 
of many distinguished men, especially those of 
Tesla, such a system, which seems to possess 
many advantages, bids fair in event of certain 
difficulties being overcome to become a formid- 
able rival to the incandescent electric lighting. 

In a system ot vacuum-tube lighting, some 
source of high alternating potential furnishing 
from 50,000 to 100,000 volts or more is employed. 
Such discharges are most readily obtained by 
means of an alternator and disruptive discharges 
from condensers in connection with an oil trans- 
former. The oil transformer is employed on ac- 
count of the high resistance of the oil as a dielec- 
tric. One of the most important advantages 
which vacuum-tube lighting possesses over light- 
ing by means of the ordinary incandescent electric 
lamp is that it produces a cold light or illumination 
of the type of glow illumination. (See Appendix 
— Illumination, Glow) 



Lis-] 



624 



[Lum. 



Lightning' Arrester Board.— (See Appen- 
dix — Board, Lightning Arrester?) 



Lightning, Bead 



-A form of light- 



ning discharge in which the flash produces a 
discontinuous line of light, thus causing the 
discharge to assume a bead-like appearance. 

Lightning Tube.— (See Appendix— Tube, 
Lightning?) 

Limit, Magnetic — 



-A term sometimes 
employed for the temperature at which a 
magnetic substance loses its magnetism on 
exposure to heat. 

Line, Kapp 



-A term proposed, but 



not generally adopted, for the English unit of 
magnetic induction. 

This term, which defines the lines per square 
inch instead of per square centimetre, does not 
harmonize with the C. G. S. system of units, 
and, therefore, should not be encouraged. 

Line, Telegraphic, Charge Current on 

The current produced by the initial 



rush of electricity into a telegraphic line on 
the closing of the circuit. 

Lines of Magnetization. — (See Appen- 
dix — Magnetization, Lines of.) 

Linear Capacity of Cable. — (See Appen- 
dix — Cable, Linear Capacity of.) 

Linear Density of Charge. — (See Appen- 
dix — Charge, Linear Density of.) 

Linear Insulation of Cable. — (See Ap- 
pendix — Cable, Linear Insulation of.) 

Liquid, Quickening A term some- 
times applied to a quicking solution. (See 
Solution, Quicking?) 

Lithanode. — A name employed for a solid 
highly conducting block of lead peroxide pre- 
pared by a certain process for the plate of a 
storage cell. (See Cell, Storage?) 

The word lithanode is properly applied to the 
product produced by Fitzgerald's process. 



posed for a crushing or removing of urinary 
calculi by means of electrolysis. 

Load. — The work thrown upon an electro- 
magnetic system or machine. 

The load on a dynamo, for example, means 
the value of its activity or rate of doing work. 

Load Diagram. — (See Appendix — Dia- 
gram, Loaa.) 

Load, Full A term indicating the 

condition of running with a comparatively 
large amount of work. 



Load, Light 



-A term indicating the 



condition of running with a comparatively 
small amount of work. 



-An electric 



Lithotrity, Electro 



-A term pro- 



Locomotive, Telpher — 

motor by means of which telpher cars are 
drawn on a telpher line. (See Telpherage.) 

Long-Range Electrometer.— (See Appen- 
dix — Electrometer, Long-Range.) 

Loop Test. — (See Appendix — Test, Loop.) 

Loss, C 2 R A term for the loss of 

energy in a conductor due to the ohmic re- 
sistance offered by the conductor to its pas- 
sage. 

The product C 3 R = activity in watts. In 
this formula, C, is the current in amperes and R, 
is the ohmic resistance in ohms, and, when multi- 
plied by the proper factor, it will give the value of 
the loss in heat units. 



Loss, Core, of Transformer A loss 

of energy in the core of a transformer due to 
hysteresis and Foucault or eddy currents, etc, 

Low-Frequency Transformer. — (See Ap- 
pendix — Transformer, Low-Frequency.) 

Low-Test Fault. —(See Appendix — Fault,. 
Low- Test?) 

Luminous Disc-Shaped Discharge. — (See 
Appendix — Discharge, Luminous Disc- 
Shaped?) 

Luminous Interference. — (See Appendix 
— Interference, Luminous?) 



Mac] 



625 



[Mac. 



M 



9U. — A symbol for magnetic moment. 
The defining equation is 9ft, = m I. 

m. — An abbreviation for minute, one of 
the practical units of time. 

m. — A symbol for strength of magnetic 
pole. 



The defining equation is F 



m 2 



in. — An abbreviation for metre, the prac- 
tical unit of length. 

li. — A symbol for magnetic permeability or 
inductivity. 



The defining equation is /.i ■ 



orC 



m 2 . — An abbreviation for square metre, 
the practical unit of surface. 

m 3 . — A n abbreviation for cubic metre, the 
practical unit of volume. 

m. a. — A contraction for milli-ampere # 
(See Milli- Ampere,) 

m : s. — An abbreviation proposed for metre- 
per-second, the practical unit of velocity. 

in : s 2 . — An abbreviation proposed for 
metre-per-second-per-second, the practical 
unit of acceleration. 

M. Current. — (See Appendix— Current, 
M.) 

M. P. — A contraction proposed for man- 
power. 

M. S. Current. — (See Appendix — Current, 
M. S.) 

Machine, Dynamo-Electric, Arc Lighting 

A dynamo-electric machine suitable 

for supplying current to arc lamps. 

Arc lights are almost invariably connected to 
the circuit in series. In such cases the series- 
wound dynamo is preferable for feeding such cir- 
cuits. (See Alac/iine, Dynavw- Electric, Series- 
Wound. ) 

Machine, Dynamo-Electric, Compensat- 
ing-Alternating A term proposed 



for a compensating alternator. (See Appen- 
dix — Alternator, Compensated.) 

Machine, Dynamo-Electric, Direct Cur- 
rent A term sometimes employed in 

place of continuous current dynamo-electric 
machine. (See Machine, Dynamo-Electric, 
Continuous Current.) 

Machine, Dynamo-Electric, for Electro- 
Plating A dynamo-electric machine 

suitable for use in electro-plating. (See Ma- 
chine, Dynamo-Electric . Plating, Electro!) 

An electro-plating dynamo-electric machine 
possesses many advantages over a voltaic battery 
for the ready production of the current required' 
in electro-plating. By its use the tedious, expen- 
sive, and often unhealthy charging of a voltaic 
battery is entirely dispensed with, since the mere 
running of a belt over a pulley, and the proper 
speeding of the machine, is all that is required to 
furnish a suitable current. 

Dynamo-electric machines for electro-plating 
should be furnished with a device for the purpose 
of preventing a reversal of the polarity of the 
dynamo by means of the current produced by the 
polarization of the electrodes or articles con- 
nected with the plating bath. The tendency of 
this current is of course opposed to that of the 
current furnished to the bath, and, should the ma- 
chine be continued in use as a source of cur- 
rent for plating while its polarity is reversed, the 
metal already deposited on the articles that are 
being electro-plated will be removed. 

In the early history of the art, considerable 
difficulty was experienced with series-wound 
machines due to reversals in the polarity of the 
dynamos, by means of the current sent back- 
wards through the dynamo by the counter E. 
M. F. of the electro-plating bath, whenever, by 
reason of a decrease of current strength, or a de- 
crease of the speed of the dynamo, its E. M. F. 
fell below the counter E. M. F. of the bath. 

Weston prevents such a reversal of the polarity 
of the dynamo by opening the circuit of the ma- 
chine as soon as the speed of the machine falls 
below a certain point. He does this by means 
of the centrifugal force acting on a small quantity 
of mercury in a small hollow conical-shap.d 
vessel. 



Mac] 



626 



[Mag. 



Brush first accomplished this same result by 
means of a shunt which he called a "teaser." 
His early plating machine containing this device 
was the prototype of the compound wound dy- 
namo-electro machine. In it the coils of the field 
magnets are excited partly by the main current 
and partly by a current shunting across the 
brushes of the machine. A machine so con- 
structed possesses the great advantage of render- 
ing the machine self- regulating under certain 
circumstances. This additional or shunt circuit 
takes a variety of forms. (See Machine, Dyna??io- 
Electric, Compound- Wound. ) 

The difficulty of reversed polarity has disap- 
peared since the introduction of the shunt or 
compound wound dynamo, i. e., a dynamo whose 
field is wholly or in part excited by a current 
shunted across the brushes of the armature. In 
such a machine, even if the E. M. F. falls below 
the counter E. M. F. of the bath, the current in 
the shunt field, and therefore the polarity, re- 
mains unchanged, and the current reverses only 
in the armature. 

Machine, Dynamo-Electric, Four-Pole 

A term sometimes employed for a 



dynamo-electric machine in which the field is 
produced by two separate north poles, and 
two separate south poles. 

Machine, Dynamo-Electric, Incandescent 
Lighting" — A term sometimes em- 
ployed for a dynamo-electric machine suit- 
able for furnishing the currents employed for 
incandescent electric lamps. 

For all cases where the incandescent electric 
lamps are connected to the leads in multiple-arc, 
or any of its varieties, any machine capable of 
producing and maintaining a constant potential 
at its terminals, notwithstanding changes in the 
load on it, is suitable for use as an incandescent 
electric-lighting dynamo -electric machine. Com- 
pound-wound machines are generally employed 
for such purposes. (See Machine, Dynamo- 
Electric, Cofnpound- Wound. ) 

Machine, Dynamo-Electric, Separate- 
Coil Alternating' A term sometimes 

employed for a separate coil alternator. 
(See Appendix — Alternator, Separate-Coil.) 

Machine, Dynamo-Electric, Separately 
Excited Alternating' A term some- 
times employed for separately excited alter- 



nator. (See Appendix —Alternator, Sepa- 
rately Excited.) 

Machine, Dynamo-Electric, Six-Pole 

A term sometimes employed for a 

dynamo-electric machine in which the field 
is produced by six poles, i. e., three separate 
north poles and three separate south poles. 

Machine, Dynamo-Electric, Two-Pole 

A term sometimes employed for a 

dynamo-electric machine in which two poles 
only are employed for producing the field. 

Such a machine is usually called a bi -polar 
machine. 

Machine, Magneto-Electric, Alternating 

An alternating current dynamo-elec- 
tric machine, the field of which is produced 
by permanent magnets. 

A magneto alternator. (See Appendix — 
Alternator, Magneto.) 

Machine, Speeding of Obtaining 

the requisite number of rotations of an arma- 
ture of a machine per second. 

Machines as ordinarily constructed produce 
their most economical output for practical pur- 
poses when a certain speed of rotation has been 
obtained. 

Machines, Dynamo-Electric, Alternating, 

Parallel Working of The working of 

two or more alternators in parallel. (See 
Appendix — Alternators, Parallel Connection 
of) 

Machines, Dynamo-Electric, Alternating, 
Series- Working The series connec- 
tion of two or more alternating dynamo-electric 
machines. (See Appendix — Alter?tators, 
Series Connection of.) 

Magazine, Magnetic A term some- 
times employed for a compound magnet. 
(See Magnet, Compound). (Obsolete.) 

Magne-Crystallic Force. — (See Appendix 
— Force, Magne-Crystallic.) 

Magne-Electric Induction. — (See Ap- 
pendix — Induction, Magne-Electric) 

Magnet, Choke A term proposed, 

for choking coil. (See Coil, Choking) 

The term choking coil would appear to be 
preferable. 



Hag.] 



627 



[Mag. 



Magnet, Compound A term for- 
merly applied to an induction coil with two 
separate circuits. 

The use of this word is inadvisable. The same 
word is already correctly employed for a mag- 
net formed of a number of separate magnets. 
(See Magnet, Co?npouna.) 



Magnet, Deflectim 



-The 



perma- 



nent magnet of a magnetometer employed 
for deflecting a small magnetic needle sus- 
pended at a definite distance in order to com- 
pare its influence with that of the earth's 
horizontal magnetic force. 

Magnet, Differential, Electro A 

differentially wound electro-magnet. (See 
Appendix — Winding, Differential.) 

Magnet, Electro-Compound — A 

term formerly applied to an electro-magnet 
the core of which is wound with two sepa- 
rate wires or conductors. 

Magnet, Laminated, Permanent 

A term sometimes employed in place of com- 
pound magnet. 

Magnet, North Pole of, Proposed A. I. 

E. E. Definition for The pole of a 

magnet which seeks the geographical north 
pole. 

Magnet, South Pole of, Proposed A. I. 

E. E. Definition for The pole of a 

magnet which seeks the geographical south 
pole. 

Magnet, Theoretical A hypotheti- 
cal magnet assumed for the purpose of 
mathematical discussion, as fulfilling the fol- 
lowing conditions, namely : An infinitely long 
and thin, uniformly magnetized bar. 

Magnet, Voltaic A term some- 
times employed for a solenoid or electro- 
magnetic helix. (See Solenoid.) 

Magnetic Alternator.— (See Appendix — 
Alternator, Magnetic.) 

Magnetic Atmosphere. — (See Appendix — 
Atmosphere, Magnetic.) 

Magnetic Bearing.— (See Appendix— 
Bearing, Magnetic.) 

3Iagnetic Compensator. — (See Appendix 
— Compensator, Magnetic.) 



Magnetic Disturbance.— (See Appendix— 
Disturbance, Magnetic?) 

Magnetic Effluvia. — (See Appendix — 
Effluvia, Magnetic?) 

Magnetic Fluid. — (See Appendix — Fluid, 
Magnetic.) 

Magnetic Flux Path.— (See Appendix— 
Path, Mag7ietic Flux?) 

Magnetic Helix. — (See Appendix— Helix, 
Magnetic.) 

Magnetic Hysteresis.— (See Appendix— 
Hysteresis, Magnetic.) 

Magnetic Limit.— (See Appendix— Limit, 
Magnetic?) 

Magnetic Magazine. — (See Appendix — 
Magazine, Magnetic.) 

Magnetic Phantom. — (See Appendix — 
Phantom, Magnetic}) 

Magnetic Shading. — (See Appendix— 
Shading, Magnetic.) 

Magnetic Source. — (See Appendix — 
Source, Magnetic?) 

Magnetic Spectrum. — (See Appendix — 
Spectrtim, Magnetic.) 

Magnetic Spiral. — (See Appendix — 
Spiral, Magnetic.) 

Magnetic Voltmeter.— (See Appendix — 
Voltmeter, Magnetic?) 

Magnetics.— That branch of science which 
treats of the laws and phenomena of mag- 
netism. 

The use of this term should not be encouraged. 

Magnetician. — A word proposed for one 
skilled in the science of magnetism as known. 

This word appears to be a good one, but is 
little used. 

Magnetine. — A word formerly employed 
for the principle of magnetism, or for the im- 
ponderable, hypothetical fluid in which mag- 
netic phenomena were assumed to take place. 

Magnetisation. — (See Magnetizatioti?) 

Magnetisation, Back (See Appen- 
dix — Magnetization, Back?) 

Magnetisation, Lines of (See Ap- 
pendix — Magnetization, Lines of.) 



Mag.] 



628 



[Mag. 



Magnetish. — Possessing the property of 
magnetism to a limited degree. 

This term is a bad one, and its use should be 
avoided. 

Magnetism, Complex-Lamellar, Distri- 
bution of The distribution of the 

magnetism of a finite magnet into an infinite 
number of complex magnetic shells. 

Magnetism, Horizontal Intensity of 

Earth's -The force which causes a 

magnetic needle to come to rest in a hori- 
zontal position in the earth's field. 

The horizontal intensity of the earth's mag- 
netism can be determined by means of a magnet- 
ometer. The horizontal intensity at any place is 
proportional to the square root of the number of 
oscillations which a needle suspended about a 
vertical axis performs at that place in a given 
time, when disturbed from its position of rest in 
the earth's field. 

Magnetism, Total Intensity of Earth's 

The entire force of the earth's mag- 
netism. 

The total intensity of the earth's magnetism 
is equal to the resultant of the horizontal and 
vertical intensities, or to the quotient of the hori- 
zontal intensity by the cosine of the angle of dip. 

Magnetism, Remanent A phrase 

sometimes used in place of residual magnet- 
ism. (See Magnetism, Residual.) 

Magnetism, Specific A term pro- 
posed for the quotient of the magnetic moment 
of a magnet by its mass. 
Magnetism, Vertical Intensity of Earth's 

The force which tends to cause a 

magnetic needle to assume a vertical position. 
The following formula gives the vertical inten- 
sity of the earth's magnetism : 
V = H. tan. 
Where V = vertical intensity. 

H = the horizontal intensity, 
and = the angle of dip. 

Magnetist. — A magnetician. 

The word magnetician is preferable. 

Magnetizability. — Possessing the ability 
of becoming magnetized. 

Magnetization, Back A term pro- 
posed in place of back or backward induc- 



tion. (See Appendix — Induction, Back- 
ward.) 

Magnetization, Circular The mag- 
netization which exists in a diphase motor 
in which two alternating magnetic fluxes of 
equal amplitude are produced in quadrature 
or at right angles to each other. 

Magnetization, Elliptical Rotary 

The magnetization which exists in a diphase 
motor in which two alternating magnetic 
fluxes exist out of phase with each other. 

Magnetization, Lines of A term 

sometimes employed for lines of magnetic in- 
duction. 

When lines of magnetic force pass through air, 
the number of lines of induction are the same as 
the number of lines of magnetizing force ; when, 
however, the lines of force pass through iron, the 
number of such lines of induction is greatly in- 
creased. 

Magnetizee. — A word proposed to desig- 
nate a person who believes he is placed 
under the power of animal magnetism. 

Magnetizer. — A word proposed to desig- 
nate a person who claims to place another 
under the power of animal magnetism. 

Magnetizing Helix. — (See Appendix — 
Helix, Magnetizing) 

Magnetizing Spiral.— (See Appendix — 
Spiral, Magnetizing) 

Magneto-Alternator. — (See Alternator, 
Magneto.) 

Magneto-Chemical Cell.— (See Appendix 
— Cell, Magneto-Chemical.) 

Magnetod. — A word employed by Reichen- 
bach for the assumed force or principle of 
animal magnetism. 

Magneto-Electric Alternating Machine. 

— (See Appendix — Machine, Magneto-Elec- 
tric Alternating) 

Magneto-Inductive Capacity. — (See Ap- 
pendix — Capacity, Magneto-Inductive) 

Magnetology. — That branch of science 
which treats of magnetism. 

The word magnetism would appear to be 
preferable. 



Mag.] 



629 



[tier. 



Magnetometer, Inclination — A 

form of magnetometer suitable for measur- 
ing variations in the magnetic inclination at 
any place. 
Magnetometer, Registering Declination 

A form of magnetometer in which the 

variations of the declination at any place can 
be automatically registered. 

Magnetometer, Variation A form 

of magnetometer suitable for measuring 
changes in the magnetic variation at any 
place. 

Magneto-Metric. — Of or pertaining to 
the measurement of magnetic force. 

Magnetometry. — That branch of science 
which treats of the measurement of the 
strength of magnetic fields. 

Magneto-Motor.— (See Appendix — Motor, 
Magneto.) 

Magnetophone. — A word sometimes used 
for a magneto telephone. 

Magneto-Tapper. — (See Appendix — Tap- 
per, Magneto.) 

Man Power. — (See Appendix — Power, 
Man) 

Manual Repeater. — (See Appendix — Re- 
peater, Manual.) 

Manual Translation. — (See Appendix — 
Translation, Manual) 

Marks, Ripple, Electrical Wave 

marks produced in a fine powder by the dis- 
charge of a Leyden jar in its neighborhood. 

These ripple marks are due to waves set up in 
the air by the passage of the discharge. 

The same discharge that produces waves in 
ether also sets up waves in the surrounding air. 
It can be shown that the same discharge that can 
excite ether waves I kilometre in length can 
excite waves in the air about I millimetre in 
length. 

3Iatt. — A word employed in electro-plating 
to designate the appearance presented by an 
electro-plating of silver in which the deposit 
is interlaced and closely massed together. 
(See Plating, Electro) 

Matter, Electric — A term formerly 

applied to the matter which was believed to 



constitute the effluvia formerly assumed to 
pass off from an electrified body. 

Matter, Fourth State or Condition of 

A term sometimes employed for the 

ultra-gaseous or radiant state of matter. (See 
Matter, Radiant or Ultra-Gaseous.) 

Matting, Burglar Alarm A mat- 
ting provided with a number of invisible con- 
tacts connected with alarm bells whose cir- 
cuits are closed by treading on the matting. 
(See Matting, Invisible Electric Floor) 

Maximum Negative Elongation. — (See 
Appendix — Elongation, Maximum Nega- 
tive) 

Maximum Positive Elongation.— (See 

Appendix — Elongation, Maximum Posi- 
tive) 
Maximum Starting Current of Motor. — 

(See Appendix — Current, Maximum Start- 
ing, of Motor) 

Maynooth Voltaic Cell. — (See Appendix 
— Cell, Voltaic, Maynooth) 

Mechanical Replacement of Disc-Indi- 
cator. — (See Appendix — Indicator, Disc, 
Mechanical Replaceinent of) 

Mechanical Telegraphic Interrupter.— 
(See Appendix — Interrupter, Telegraphic, 
Mechanical) 

Medication, Cataphoric The intro- 
duction of drugs or other medicaments into 
the body through its tissues by the cataphoric 
action of an electric current. (See Cata- 
phoresis. Osjnose, Electric) 

Medium, Aelotropic A medium 

which manifests different actions in definite 
directions ; /. e., an eolotropic medium. (See 
Medium, Eolotropic) 

Crystallized bodies are in general notably 
aelotropic, while amorphous substances are gen- 
erally isotropic. 

An aelotropic substance may be expected to 
possess different electrostatic elastivity and in- 
ductive capacity in different directions. 

Melting of Electric Conductor.— (See 

Appendix — Conductor, Electric, Melting of) 
Mercurial Phosphorus. — (See Appendix 
— Phosphorus, Mercurial) 



Het.] 



630 



[Mho. 



Metallic Conduction.— (See Appendix— 
Conduction, Metallic) 

Metallic Cross. — (See Appendix — Cross, 
Metallic) 

Metallo-Chronies. — Colors which appear 
when a salt of lead, such as the acetate, is 
electrolyzed under peculiar circumstances. 

Metallo chromes are produced by electrolytic 
deposits of peroxide of lead in the neighborhood 
of the anode. When the thickness of the coating, 
which is deposited on a plate of polished steel, is 
properly regulated, a series of brilliant colors 
appear. 

Gassiot recommends the following process for 
obtaining metallo-chromes. 

" Place the polished steel plate in a glass basin 
containing a clear solution of acetate of lead, and 
over it a piece of card. A small rim of wood 
should be placed over the card, and on that a 
circular copper disc. On contact being made 
from 5 to 20 minutes, with two or three cells of a 
small constant battery, the steel plate being con- 
nected with the positive electrode, and the cop- 
per disc with the negative, the deposit will be 
effected, and a series of exquisite colors will ap- 
pear on the steel plate. The colors are films of 
peroxide of lead thrown down on the surface of 
the steel, and the varied tints are occasioned by 
the varying thicknesses of the precipitated film, 
the light being reflected through them from the 
metallic surface below. By reflected light every 
prismatic color is seen ; and by transmitted light 
a series of prismatic colors complementary to the 
first series appears, occupying the place of the 
former series. 

' ' The colors are seen in the greatest perfection 
by placing the plate before a window, and inclin- 
ing a white sheet of paper at 45 degrees over it. " 

Similar colorations are obtained when other 
substances are electrolytically deposited. Under 
certain conditions these colorations assume the 
form of concentric circles, that are sometimes 
called Nobili's rings. 

Nobili's rings are readily obtained by placing 
a drop of acetate of copper on a silver plate and 
touching the middle of the drop with a piece of 
zinc. Under these circumstances prismatically 
colored rings are formed, that are disposed 
concentrically around the point of contact of the 
zinc. 

Meteorograph, Electric. — An apparatus 
for automatically registering various meteor- 



ological values, such, for example, as the in- 
dications of a barometer or thermometer, the 
direction and velocity of the wind, or the 
value of the rainfall. 

Meteorology. — That branch of physics 
which treats of the phenomena of the atmos- 
phere. 

Meteorology, Electric That branch 

of meteorology which treats of the electric 
phenomena of the atmosphere. 

Meter, Coulomb Any form of ap- 
paratus capable of measuring the number of 
coulombs that pass in a circuit in a given time. 

Any form of galvanometer which gives the cur- 
rent in amperes will give the number of coulombs 
that pass if the time the current is flowing is 
known. Various forms of electric meters will 
therefore give the number of coulombs that pass 
in a circuit. (See Meter, Electric.) 

Meter, Electrolytic — An electro- 
chemical meter. (See Meter, Electro-Chem- 
ical) 

Meter, Quantity A coulomb meter. 

Meter, Telephonic A meter em- 
ployed for recording the time during which a 
telephone is in use. 

The telephonic meter, as at present constructed, 
consists essentially of a clock, the pendulum of 
which is caught by means of a lever connected with 
the telephone lever. By such means the clock is 
stopped while the telephone is out of use or is 
hung on its hook. 

Method, Accumulation, for. Testing 

Joints in Electric Cables A sensitive 

method of testing the insulation of a joint, or 
of a few feet of gutta-percha core, by allowing 
the leakage of the joint to accumulate through 
a condenser for a considerable time and then 
measuring the condenser discharge. 

Method of Slow Discharge.— (See Appen- 
dix — Discharge, Slow, Method of.) 

Mho, Proposed A. I. E. E. Definition for 

A name proposed for the practical 

unit of conductivity. 

A unit of electrical conductance of the 
value of io~ 9 absolute units; or, in other 
words, having a value equal to the reciprocal 
of the ohm. 



Mho.] 



631 



[Mot. 



This name for the practical unit of electrical 
conductance was proposed by a Sub-Committee 
of the American Institute of Electrical Engineers 
on Provisional Programme of the International 
Electrical Congress, held in Chicago, U. S. A., 
in 1893, on the occasion of the World's Columbian 
Exposition. 

Milometer. — An instrument for measuring 
the value of conductance in mhos. (See Con- 
ductance. Mho) 

Micauite. — A name sometimes given to a 
variety of insulating material made from pure 
mica bound together by some cementing 
material. 

Micro-Ohm. — The millionth of an ohm. 

Microphone, Plastic-Circuit — A 

microphone in which the ordinary variable 
contact is replaced by a plastic material of 
low conducting power. 

The plastic-circuit microphone is the invention 
of Clammond. In it the ordinary powder form- 
ing the loose contact is obtained by means of a 
plastic material composed of a mixture of a good 
conducting substance with some plastic non-con- 
ducting material. 

The advantage claimed for the plastic-circuit 
telephone transmitter is that it has a much greater 
range of operation than the ordinary contact 
microphone, being able to transmit either faint or 
loud tones with equal distinctness. 

Migration of Ions. — (See Appendix — Ions, 
Migration 0/.) 

Mile, Ohm The number obtained 

by multiplying the weight of 1 mile of wire 
of a given substance by its resistance. 

The ohm mile of a given substance is the mass 
of a mile of wire of that substance having the 
resistance of an ohm. 

Milli- Ammeter. — A milli-ampere meter. 

Milli-Ampere Meter. — (See Meter, Milli- 
Ampere) 

Mining, Electric Carrying on the 

various operations of mining by means of 
electric power. 

Electricity has been successfully employed in 
mining for the driving of percussion or rotary 
drills, for electric haulage, for pumping, and for 
purposes of communication, ventilation, power 
and artificial lighting. 



Minus Charge.— (See Appendix— Charge, 
Minus.) 

Molecular Decomposition. — (See Ap- 
pendix — Decomposition, Molecular.) 

Molecular Voltaic Couple.— (See Ap- 
pendix — Couple, Molecular Voltaic.) 

Monad Atom. — (See Appendix — Atom, 
Monad.) 

Monochord. — A single stretched wire for 
measuring the relative number of vibrations 
produced by different musical notes. 

The instrument takes the name monochord, 
from the fact that it consists, practically, of a 
single chord stretched between two points of 
support over a resonant case, and provided with 
means for suitably adjusting its tension so as to 
produce, when vibrating as a whole, a note of a 
given musical pitch. When it is required to de- 
termine the relative number of vibrations existing 
between the note which the monochord produces 
and some other note, a sliding bridge is placed 
in some intermediate part of the wire so as to cut 
off a part of its length. 

When the length of the original wire has been 
shortened by means of a sliding bridge, so that 
it produces a higher note whose pitch is to be 
compared with that of the wire vibrating as a 
whole, the relative number of vibrations are then 
inversely proportional to the lengths of the two 



■A disc formed of 



Mop, Polishing — 

circular pieces of calico, felt, or similar soft 
material mounted on a shaft and employed, 
When put in rapid rotation, for polishing 
articles so as to prepare their surfaces for 
electro-plating. (See Plating, Electro.) 

For use, mops are charged with fine polishing 
material; as, rouge, tripoli, etc. 

Mopped. — Polished by the action of a mop. 
(See Appendix — Mop, Polishing) 

Morse Push. — (See Appendix — Push, 
Morse) 

Morse Tapper. — (See Appendix — Tapper, 
Morse) 

Motion, Electrostatic Motion pro- 
duced by means of an electrostatic field 
somewhat similar to the motion produced by 
means of a magnetic field. 



Mot.] 



63^ 



[Mot, 



Electrostatic motion may be produced by vary- 
ing electrostatic fields placed at right angles to 
each other. When the force varies in accordance 
with the sine law, and the difference in phase 
varies by only 90 degrees, a uniform tendency to 
rotation is produced. 

Motion, Harmonic A term some- 
times employed in place of simple-harmonic 
motion. (See Motion, Simple-Harmo?iic) 

Motion, Periodic A term some- 
times employed in place of simple-periodic 
motion. (See Motion, Simple-Periodic) 

Motor, Constant-Potential — A 

motor designed for operation by means of a 
constant potential current. 

Where the motor is to be operated at a constant 
speed, or by a constant-potential circuit, such, 
for example, as an incandescent lighting circuit, 
it is generally made a plain, shunt-wound motor. 

Motor, Diphase A motor which 

requires for its operation two diphase cur- 
rents. 

The armature of such a motor is always wound 
either with two separate circuits, or has two 
separate connections to the same common wind- 
ing. 

This term would appear preferable to the term 
two-phase motor. 

Motor, Dynamo A constant cur- 
rent transformer or dynamotor. (See Ap- 
pendix— Dynamotor) 

Motor, Efficiency of Electric The 

watts delivered at the motor pulley, divided 
by the watts supplied. 
Motor, Electric Street Railway, Bucking" 

of (See Appendix — Bucking) 

Motor, Electrostatic -A motor 

driven by means of the induction of two 
varied electrostatic fields at right angles to 
each other. 

Generally, a motor driven by the action of 
electrostatic fields. 

Motor, Idle Wire of (See Ap- 
pendix — Wire, Idle, of Armature of Motor) 

Motor, Induction A motor in which 

the magnetic field is produced entirely by the 



working current, as distinguished from a 
motor in which the field magnets are inde- 
pendently maintained. 

An induction motor consists essentially of coils 
of wire and laminated iron discs so related to one 
another that the currents in the moving parts are 
induced by currents in the stationary parts. 

Motor, Magneto A term formerly 

employed for a voltaic battery coupled in 
parallel. 

The current furnished by such a battery being 
capable, when employed with suitable electro- 
magnets, to produce powerful magnetism, was 
called a magneto-motor. This word is generally 
used as below. 

Motor, Magneto A motor whose 

field is produced by permanent magnets. 

Motor-Man. — A word generally applied to 
the person who operates the motor car of 
street railway systems. 

Motor, Multiphase A term some- 
times en- ployed in place of polyphase motor. 
(See Appendix— Motor, Polyphase) 

Motor, Polyphase A motor ope- 
rated by means of polyphase currents. 

Motor, Polyphase, Unsymmetrical 

— An unbalanced polyphase motor; i. e., a 
motor where one circuit carries a greater 
load than the other circuit or circuits. 

Motor, Single-Phase A uni-phase 

motor. 

The term uni-phase is preferable. 

Motor, Synchronous, Self-Starting 

— A motor of the synchronous type that is 
capable of self-starting. 

Motor, Three-Phase A tri-phase 

motor. (See Appendix — Motor, Tri-Phase) 

The term tri-phase motor would appear to be 
preferable. 

Motor, Tri-Phase A motor which 

requires for its operation three tri-phase cur- 
rents. 

The armature of such a motor is always wound 
either with three separate circuits or has three 
separate connections to a common winding. 

Motor, Two-Phase — A diphase 

motor. (See Appendix — Motor, Diphase) 



Mot.] 



633 



[Nip. 



The term diphase motor would appear to be 
preferable. 

Motor, Uni-Phase A motor which 

requires for its operation a simple alternating 
current ; i. e., a current which is uni-phase. 

The term uni-phase is preferable to the term 
single-phase. 

Mounting of Filament. — (See Appendix 
Filament, Mounting of) 

Multi-Phase Alternator. — (See Appendix 
— Alternator, Multi-Phased) 

Multi-Phase Motor. — (See Appendix — 
Motor, Multi-Phase) 

Multiple Auto-reversible Tele-radio- 
phone. — (See Appendix — Tele-radiophone, 
Auto-reversible or Multiple) 

Multiple-Lightning' Flash. — (See Ap- 
pendix — Flash, Multiple-Lightning) 

Multiple-Parallel Circuit. — (See Ap- 
pendix — Circuit, Multiple-Parallel) 



Multiplex Telegraph.— (See Appendix- 
Telegraph, Multiplex) 

Multiplex Telephony.— (See Appendix- 
Telephony, Multiplex) 



Multiplier, Astatic 



-A term some- 



times employed for an astatic galvanometer. 
(See Galvanometer, Astatic.) 



-A term for- 



Multiplier, Dynamic — 

merly applied to a self-induction coil. (See 
Appendix — Coil, Induction, Self) 

Multiplier, Electro-Magnetic A 

term sometimes employed for Sweigger's 
Multiplier. (See Multiplier, Sweigger's) 

Municipal System of Incandescent Elec- 
tric Lighting.— (See Appendix— System, 
Municipal, of Electric Lighting) 

Mutually Induced Currents.— (See Ap- 
pendix— Currents, Mutually Induced) 



N 



n.—A symbol sometimes employed for 
frequency. 

Natural Period. — (See Appendix — Period, 
Natural) 

Needle, Drift of The failure of the 

needle of a galvanometer to remain at its 
zero point when no current is passing through 
its coils, usually due to variation in the 
magnetic condition of the needle, or to 
variation in the torsion of the suspending 
fibre, local causes, etc. 

Needle Telegraph. — (See Appendix — 
Telegraph, Needle) 

Needle, Vertical Magnetic A 

term sometimes employed for a dipping 
needle. (See Needle, Magnetic, Dippi?ig) 

Negative Electrification. — (See Appendix 
— Electrification, Negative) 

Negative Fluid.— (See Appendix— Fluid, 
Negative) 

Negative Spark.— (See Appendix— Spa rk, 
Negative) 



Neutral Zone of Electrically Charged 
Insulated Conductor. — (See Appendix— 
Zone, Neutral, of Electrically Charged In- 
sulated Cofiductor) 

Neutral Zone of Magnet— (See Ap- 
pendix — Zone, Neutral, of Magnet) 

Nipple on Negative Carbon. — A small 
projection formed at the end of the negative 
carbon directly opposite the positive carbon 
of a voltaic arc that has been established for 
some little time. 

The nipple is formed at the end of the nega- 
tive carbon directly opposite the crater in the op- 
posing end of the positive carbon by the de- 
position of volatilized carbon from the positive 
electrode. The material of the nipple is pure 
graphite or plumbago. 

If the ends of the carbons, that are thrown away 
from an electric arc lamp on trimming the lamp, 
be examined, they will be found to possess either 
a small crater or a small projection or nipple at 
their burned end. 



Nod.] 



634 



[Osc. 



Either of these ends, but especially the nipple 
at the negative carbon, is formed of pure graphite 
sufficiently soft to be readily used for some con- 
siderable time as a lead pencil. 

Node. — A point of comparative rest in a 
vibrating body. 

Since the position of an anti-node for a funda- 
mental tone may be the position of the node for 
one of its harmonics, it is clear that the nodes are 
often necessarily only points of relative rest. 



Non-Automatic Repeater. — (See Appen- 
dix — Repeater, Non- Automatic?) 

Non-Ferric Inductance. — (See Appendix 
— Inductance, Non-Ferric?) 

Non-Polar Transformer. — (See Appen- 
dix — Transformer, Non-Polar?) 

Northern Light. — (See Appendix— Light, 
Northern?) 



0. — An abbreviation sometimes used for 
ohm, the practical unit of electric resistance. 

co. — A symbol sometimes used for angular 
velocity. 

V 
The defining equation is 00= — 

0: cm. — An abbreviation proposed for 
ohm-centimeter, the practical unit of resis- 
tivity. 

Oersted, Proposed A. I. E. E. Definition 

for A name proposed for the practical 

unit of magnetic reluctance. 

A unit of magnetic reluctance having a 
value of one absolute unit. 

This name was proposed by a Sub-Committee 
of the American Institute of Electrical Engineers 
on Provisional Programme for the International 
Electrical Congress, held in Chicago, U. S. A., 
in 1893, on the occasion of the World's Columbian 
Exposition. 

Ohm, B. A. A resistance of 14.4521 

grammes of mercury in the form of a col- 
umn of uniform cross-section (one square 
millimetre) and 104.8 centimetres in height 
at o degree C. 

The above value of the ohm was adopted as 
the unit of the British Association at its meeting 
held in Edinburgh in August, 1892. 

Ohm, International — The value 

of the international ohm adopted at the 
Chicago Congress of 1893, as being the re- 
sistance column based upon the ohm equal 
to io 9 units of resistance of the C. G. S. 
system of electro-magnetic units, and is rep- 
resented by the resistance offered to an un- 



varying electric current by a column of 
mercury at the temperature of melting ice 
14.4521 grammes in mass, of a constant cross 
sectional area, and of the length of 106.3 
centimetres. 

Ohm Mile. — (See Appendix— Mile, Ohm.) 

Ohm, Proposed A. I. E. E. Definition for 
The resistance offered at the tempera- 
ture of melting ice by a column of mercury, 
14.4521 grammes in mass, of a constant cross- 
sectional area and of a length of 106.3 centi- 
metres. 

One-Way Door Trigger. — (See Appendix 
— Trigger, One- Way Door?) 

Open-Circuit Transformer. — (See Ap- 
pendix — Transformer, Open-Circuit?) 

Opposing Electromotive Force. — (See 
Appendix — Force, Electromotive, Opposing?) 

Optical Galvanometer. — (See Appendix — 
Galvanometer, Optical?) 

Oscillator, Hertz's A term some- 
times employed for two insulated metallic 
plates, to which are attached metallic rods, 
terminated by rounded knobs or balls separ- 
ated by an air gap or air space, through which 
a disruptive discharge passes. 

The metallic plates represent the opposite coat- 
ing of a Leyden jar. When employed as Hertz's 
oscillator each plate is connected to the terminal 
of a Ruhmkorff coil, and at each discharge elec- 
trical surgings are produced, which cause waves 
to radiate from the plates into the surrounding 
ether. 

— A term 



Oscillator, Hertz's Axial — 

sometimes employed for Hertz's linear oscil- 



Osc] 



635 



[Par. 



lator. (See Appendix — Oscillator, Hertz's 
Linear.) 



Oscillator, Hertz's Linear 



A form 



of Hertz's oscillator in which a straight or 
linear conductor is employed instead of a 
plate as in the ordinary oscillator. (See Ap- 
pendix — Oscillator, Hertz's.) 

According to Lodge, a thunder cloud con- 
nected to the earth by means of a lightning rod 
forms a linear oscillator. 

Out-Put. — The useful energy given out by 
a machine. 

The out-put is generally taken in connection or 
in comparison with the in-put. When the use- 
ful or available electric energy of any source is 



divided by the total electric energy, the value of 
a ratio, called the efficiency, is obtained. In this 
case the out-put, when divided by the total in-put,, 
gives the efficiency. (See Efficiency, Electric. ) 

Oven, Baking", Electrical An elec- 
trically heated Daking oven. 

Almost any form of baking oven can be heated 
by means of electric heaters suitably placed 
therein. 

Overflow of Leyden Jar. — (See Appendix 
— Jar, Leydeii, Overflow of.) 

Overlap Test— (See Appendix — Test, 
Overlap.) 

Over-Maximal Contraction. — (See Ap- 
pendix — Contraction, Over-Maximal^) 



P. — A symbol proposed for power. 

W 

The defining equation is P = t= 

P.-—A symbol proposed for electric power. 

The same symbol is proposed for mechanical 
power. 

The defining equation is P = C E. 

p. — A symbol proposed for pressure. 

F 
The defining equation is p = — 

$. — A symbol employed for flux of mag- 
netic force. 
The defining equation is $ = £$ X S. 

Pacinotti Teeth.— (See Appendix— Teeth, 
Pacinotti.) 

Page Effect— (See Appendix— Effect, 
Page.) 

Pair, Thermo A thermo couple. 

(See Couple, Tker mo-Electric.) 

Pair, Thermo-Electric A term 

sometimes employed in place of thermo-elec- 
tric couple. (See Couple, Thermo-Electric :) 

Pair, Yoltaic A term sometimes 

employed in place of voltaic couple. (See 
Couple, Voltaic^) 



Pan, Backing A pan in which the 

copper shell of an electrotype is placed, in 
order to receive its backing of type metal. 

When the copper shell has been placed in the 
backing-pan, for the purpose of receiving its 
backing of type-metal, it has its back covered 
with sheets of tin-foil. It is then placed along 
with the backing-pan in the melting-pot, a pot 
filled with melted type-metal, on which it is per- 
mitted to float until the covering of tin- foil is 
melted. It is now removed and placed on a level 
table where the molten metal from the melting 
pot is poured over it until a layer of the required 
thickness is obtained. 

Pan-Telephone.— (See Appendix— Tele- 
phone, Pan.) 

Parallel-Arc Circuit. — (See Appendix — 
Circuit, Parallel- Arc.) 

Parallel Connection of Alternators. — 

(See Appendix — Alternators, Parallel Con- 
nection of.) 

Parallel Working of Alternating Dy- 
namo-Electric Machines. — (See Appendix — 
Machines, Dynamo-Electric, Alternating , 
Parallel Working of) 

Paramagnetized. — Endowed with para- 
magnetic properties. (See Paramagnetism.) 



Pas. 



636 



[Pha. 



■(See Appendix — 



-The path or 



Passive Resistance. 

Resistance, Passive?) 

Path, Magnetic Flux 

circuit taken by the lines of magnetic force 
or flux. 

Pear Push. — (See Appendix — Push, 
Pear.) 

Peltier's Cross. — (See Appendix— Cross, 
Peltier's.) 

Pencil, Carhon A term sometimes 

employed for a carbon rod. 

A rod or cylinder of carbon, as distinguished 
from a plate. 

Pendant Socket. — (See Appendix — Socket, 
Pendant?) 

Pendulum, Electric A term some- 
times employed for a pith ball electroscope, 
so arranged as to move to-and-fro like an 
ordinary pendulum. 

This use of the term is to be avoided, since the 
word, as primarily employed, signifies either a 
pendulum driven by electric impulses, or a pen- 
dulum so arranged as to produce timed impulses. 

The term electroscopic or electrostatic pen- 
dulum would appear preferable. (See Pendulum, 
Alectric.) 

Pentad Atom. — (See Appendix — Atom, 
Pentad.) 

Percentage Conductivity of Wire. — (See 
Appendix — Conductivity, Percentage, of 
Wire?) 

Period. — The interval of time between two 
sw<§#essive passages of a vibration through 
a given point of its path taken in the same 
direetion. 



Period, Natural 



-The period of 



harmonic frequency which brings it to the 
same value as that of the fundamental fre- 
quency. 

The natural period, according to Lodge, is 
represented by the following formula. 

T = 2 it n/LC X 10-3 
Where T = the period in seconds. 

L = the coefficient of self-induction in 

henries. 
C = the capacity in micro farads. 



The natural period can be varied either by 
varying the self-induction of the circuit or by 
varying its capacity. 

Period, Variable, of Telegraph Line 

— The time required for a current in a tele- 
graph line to reach a constant strength 
after the circuit through it is closed. 

Periodic Motion.— (See Appendix — Mo- 
tion, Periodic) 

Periodicity of Alternation. — (See Ap- 
pendix — Alternation, Periodicity of.) 

Permanent Laminated Magnet. — (See 
Appendix — Magnet, Laminated, Perma- 
nent?) 

Permanent Telegraphic Signal.— (See 

Appendix — Sig?zal, Telegraphic, Perma- 
nent?) 

Permeation. — A word sometimes em- 
ployed for the number of lines of magnetic 
force per square centimetre. 

Permittance. — A word proposed for 
dielectric capacity. (See Appendix — Capa- 
city, Specific Dielectric?) 

Electrostatic induction takes place between the 
two coatings of a condenser, or between two 
copper conductors across the dielectric between 
them. Dielectrics differ greatly in their ability 
to permit this influence to pass through them, and 
this difference has been called the dielectric 
capacity, the specific inductive capacity, the in- 
ductive capacity, or the permittance. (See 
Capacity, Specific Inductive.) 

Permittivity. — A word sometimes em- 
ployed for specific permittance. (See Ap- 
pendix — Permittance?) 

Phantom, Magnetic A term some- 
times employed for magnetic figures. (See. 
Figures, Magnetic. Field, Magnetic?) 

Phantom Streams. — (See Appendix — 
Streams, Phantom?) 

Phase. — The fractional part of a period 
which has passed since a vibrating body last 
passed through the extreme point of its path 
in the positive direction. 

Phase Angle. — (See Appendix — Angle, 
Phase?) 



Pha.] 



637 



[Plu. 



Phase Windings.. — (See Appendix — 
Windings, Phase.) 

Phenomena. — Plural of phenomenon. 

Phonogram. — A dispatch transmitted by 
means of a telephone. 

The word phonogram corresponds to the word 
telegram. 

This word is also used for the record produced 
by a phonograph. 

Phonoplex Telegraph. — (See Appendix — 
Telegraph, Phonoplex?) 

Phosphorescent Lamp.— (See Appendix — 
Lamp, Phosphorescent.) 

Phosphorus, Mercurial —A term 

employed by Hawksbee in 1795 for the light 
produced by the motion of a column of mer- 
cury in an exhausted tube. 

The light so produced is due to electricity 
caused by the friction of the mercury against the 
walls of the tube. Such a light is often seen in 
the Torricellian vacuum which exists in the space 
above the mercurial column in a barometer tube. 

Photo-Electric Alarm. — (See Appendix — 
Alarin, Photo-Electric?) 

Photo-Electric Impulsion Cell. — (See 
Appendix — Cell, Photo-Electric Impulsion.) 

Photometer, Spectro A form of 

photometer suitable for measuring the rela- 
tive intensities of lights of different qualities. 

A spectro-photometer consists essentially of 
means by which the two parallel beams of light 
that are to be compared are passed side by side 
through the same prism. The field is then 
limited to a single color, and the respective 
intensities of the two lights as regards this par- 
ticular character of radiation are then compared. 

Photo-Micrography, Electric The 

art of photographing microscopic images by 
means of the electric light. 

Physiologist, Electro One skilled 

in the art of electro-physiology. (See Physi- 
ology, Electro.) 

Pins, Core, of Magnet Small pins 

of copper or other non-magnetic material 
placed in the cores of an electro-magnet at 
its poles for the purpose of preventing stick- 



Planer, Electric Deck An elec- 
trically driven rotary cutter or planer, adapted 
for the ready planing of the deck of a ship. 

Fig- 579 shows an electric deck planer. The 
rotary cutter revolves at some three thousand 




579. An Electric Deck Planer. 



revolutions per minute, and is so arranged as to 
be readily adapted for a varying depth of cut. 

Plastic-Circuit Microphone.— (See Ap- 
pendix — Microphone, Plastic-Circuit) 

Plates, Exhausted, of Storage Cell 

A phrase employed to characterize the condi- 
tion of the plates of a storage battery when 
they have furnished all the current they are 
capable of producing without being injured. 
(See Plates of Secondary or Storage Cell, 
Forming of.) 

Plates, Field A term sometimes 

applied to the plates of tin-foil, on a Toppler- 
Holtz influence machine, which act as in- 
ductors. (See Machine, Toppler-Holtz.) 

Plates, Formed, of Storage Cell 

A phrase employed to characterize the condi- 
tion of the plates of a new storage battery 
when they have been prepared for regular 
service by a preliminary process of charging, 
or charging and discharging. (See Plates of 
Secondary or Storage Cell, Forming of.) 

Plating Trough. — (See Appendix — 
Trough, Plating.) 

Plug, Attachment A plug for at- 
taching and connecting a flexible cord to any 
lamp socket or receptacle. 

Plus Charge. — (See Appendix — Charge, 
Plus.) 



Poc. 



638 



[Pot. 



Pocket Galvanometer.- (See Appendix — 
Galvanometer, Pocket?) 

Point, Indifferent A term some- 
times employed for the neutral point of a 
magnet. (See Line, Neutral, of a Magnet?) 

Point, Smashing, of Incandescent Elec- 
tric Lamps The point in the life of 

an incandescent electric lamp at which it is 
said to be more economical to replace it by 
a new lamp than it is to keep it any longer 
in use. 

The life of an incandescent electric lamp can 
be preserved for many thousand hours. It is 
claimed, however, that, so far as economy is con- 
cerned, it is more economical after a certain 
number of hours burning to replace it by another 
than it is to continue it any longer in use. This 
conclusion, however, is by no means generally 
accepted. 

The length of life will, of course, depend on 
the make of the lamp and the potential to which 
it has been exposed. Cases, however, may fre- 
quently arise where it will be more economical to 
use the lamp under an increased difference of po- 
tential than to cease using it. 

Polar Aurora. — (See Appendix — Aurora, 
Polar.) 

Polar Transformer. — (See Appendix — 
Transformer, Polar?) 

Polarization Battery. — (See Appendix — 
Battery, Polar izatio7i. ) 

Polarization, Gas A term some- 
times employed for that form of polarization 
which is due to the collection of a gas, gen- 
erally hydrogen, on the negative plate. (See 
Cell, Voltaic, Polarization of.) 

Polarized Indicator. — (See Appendix — 
Indicator, Polarized?) 

Pole Indicator. — (See Appendix — Indi- 
cator, Pole?) 

Pole, Magnetic, Blue —A term 

sometimes employed for that pole of a mag- 
net which points approximately towards the 
geographical south pole. 

The natural confusion arising from this non- 
descriptive term is still further increased by the 
fact that some writers use the word blue-pole for 



the pole which points towards the geographical 
north pole. 

Pole, Magnetic, Eed A term some- 
times employed for the pole of a magnet 
which points approximately towards the geo- 
graphical north pole. 

Sometimes used in opposite sense. (See Ap- 
pendix — Pole, Magnetic, Blue.) 

Pole, Magnetic, Unmarked —A 

term sometimes employed for the south pole 
of a magnet. 

Pole, Resultant Magnetic A term 

sometimes employed for a consequent pole. 
(See Pole, Consequent') 

Polishing Boh.— (See Appendix— Bob, 
Polishing?) 

Polishing Mop.— (See Appendix— Mop,. 
Polishing.) 

Polyphase Apparatus.— (See Appendix — 
Apparatus, Polyphase.) 

Polyphase Armature.— (See Appendix — 
Armature, Polyphase.) 

Polyphase Currents. — (See Appendix-^ 
Currents, Polyphase.) 

Polyphase Generator.— (See Appendix— 
Generator, Polyphase.) 

Polyphase Motor. — (See Appendix — 
Motor, Polyphase?) 

Polyphase Working.— (See Appendix— 
Working, Polyphase.) 

Polyphased Alternating Currents. — (See 
Appendix — Currents, Polyphased, Alternat- 
ing?) 

Positive Electrification.— (See Appendix 
— Electrification, Positive?) 

Positive Fluid.— (See Appendix— Fluid t 
Positive?) 

Positive Spark. — (See Appendix— Spark, 
Positive.) 

Potash Brush. — (See Appendix — Brushy 
Potash?) 

Potential, Scalar A potential pos- 
sessing magnitude and sign without directive 
signification, as distinguished from, a vector 
potential, which possesses both direction and 



rot.] 



639 



[Pro. 



magnitude. (See Appendix — Potential, Vec- 
tor.) 



Potential, Vector 



-A potential pos- 



sessing directive properties and one that may 
be derived by the process of summation 
from vectors, or elementary directed quanti- 
ties, as opposed to a scalar potential, which 
possesses undirected magnitude. (See Ap- 
pendix — Potential, Scalar?) 

Potentiometer, Alternating" Current 

— A form of potentiometer designed for 
measuring the differences of potential in al- 
ternating current circuits. 

Power Factor. — (See Appendix — Factor, 
Power?) 

Power, Man A unit of power equal 

to iV horse-power, or about 74^ watts. 

Pressure, Electric A term some- 
times loosely employed for difference of po- 
tential or electromotive force. (See Poten- 
tial, Difference of.) 

The terms potential difference and elec- 
tromotive force are preferable terms. The use 
of the term electric pressure can well be aban- 
doned. The term electric pressure, however, is 
much to be preferred to the very objectionable 
term electric tension, or difference of tension. 

Primary Cell. — (See Appendix — Cell, 
Primary?) 

Primary Electric Clock. — (See Appendix 
— Clock, Primary Electric?) 

Primary Electric Heater. — (See Appendix 
— Heater, Prifnary Electric?) 

Primary Spiral of Induction Coil.— (See 
Appendix — Spiral, Primary, of Induction 
Coil?) 

Process, Building-, for Moulds of Elec- 
trotypes A process for bringing up 

the blank spaces in the mould of an electro- 
type by the use of wax, melted by a build- 
ing iron — the high places thus built up 
becoming depressions in the finished plate. 

Process, Coking, for Filament of Incan- 
descent Electric Lamp — A process 



for converting the carbon of an incandescent 
filament into coke, by subjecting it, while in 
a vacuum, to the prolonged heating action of 
a powerful electric current. (See Appendix — 
Filament, Coked?) 

Process, Quicking A term em- 
ployed in electro-plating for a process by 
means of which an article that is to be electro- 
plated with silver, is previously coated with a 
layer of mercury by dipping it into a quicking 
solution, /'. e., a solution of salt of mercury. 
(See Solution, Quicki7ig.) 

Process, Stopping-Otf A process 

employed in electro-plating by means of which 
an article which is to be electro-plated on por- 
tions only of its surface with one metal, and 
on other portions with another metal, is first 
completely covered by an electro-plating of 
the cheaper metal, and is then stopped-off , by 
covering with a coating of non-conducting 
varnish such portions only of its surface as 
are not to receive the deposit of the dearer 
metal. (See Stopping-Off?) 

Process, Stopping-Out A process 

employed in electrotyping by means of which 
those parts of an electrotype mould that are 
not to be copied in the electrotype are covered 
with clean hot wax. • 

The stopping-out process is similar to the stop- 
ping-off process in electro-plating. Wherever the 
black lead or plumbago surface is covered with 
clean wax, the copper fails to be deposited. 

Proposed A. I. E. E. Definition for 
Impressed Electromotive Force. — (See Ap- 
pendix — Force, Electromotive, Impressed, 
Proposed A. I. E. E. Definition for) 

Proposed A. I. E. E. Definition for Gauss. 

— (See Appendix — Gauss, Proposed A. I. E. 
E. Definitio?ifor.) 

Proposed A. I. E. E. Definition for 
Henry. — (See Appendix — Henry, Proposed 
A. I. E. E. Definition for?) 

Proposed A. I. E. E. Definition for In- 
ductivity. — (See Appendix — Inductivity, 
Proposed A. I. E. E. Defi?iition for.) 



Pro.] 



640 



[Pal, 



Proposed A. I. E. E. Definition for Mho. 

— (See Appendix — Mho, Proposed A. I. E. E. 
Definition for.) 

Proposed A. I. E. E. Definition for 
Mutual Inductance. — (See Appendix — In- 
ductance, Mutual, Proposed A. I, E. E. Defi- 
nition for :) 

Proposed A. I. E. E. Definition for North 

Pole of Magnet. — (See Appendix — Magnet, 
North Pole of, Proposed A. I. E. E. Defini- 
tion for.) 

Proposed A. I. E. E. Definition for 

Oersted. — (See Appendix — Oersted, Proposed 
A.I. E. E. Definition for.) 

Proposed A. I. E. E. Definition for Ohm. 

— (See Appendix — Ohm, Proposed A. I. E. 
E. Definition for.) 

Proposed A. I. E. E. Definition for Poly- 
phase Alternating Current. — (See Appen- 
dix — Current, Polyphase Alternating, Pro- 
posed A. I. E. E. Definition for :) 

Proposed A. I. E. E. Definition for Re- 
luctivity. — (See Appendix — Reluctivity, 
Proposed A. I. E. E. Definition for.) 

Proposed A. I. E. E. Definition for Self- 
Inductance. — (See Appendix — Inductance, 
Self, Proposed A. I. E. E. Definition for.) 

Proposed A. I. E. E. Definition for South 
Pole of Magnet. — (See Appendix — Magnet, 
South Pole of, Proposed A. I. E. E. Defini- 
tion for.) 

Proposed A. I. E. E. Definition for 
Triphase Alternating Current— (See Ap- 
pendix — Current, Triphase Alternating, 
Proposed A. I. E. E. Definition for) 

Proposed A. I. E. E. Definition for Yolt. 

— (See Appendix — Volt, Proposed A. I. E. E. 
Definition for.) 

Proposed A. I. E. E. Definition for Watt. 

— (See Appendix — Watt, Proposed A. I. E. 
E. Definition for.) 

Proposed A. I. E. E. Definition for Web- 
er. — (See Appendix — Weber, A. I. E. E. 
Definition for.) 



Protection, Conduction Lightning 

— The protection of any instrument from the 
passage of a current due to lightning around 
its coils, and so disturbing the magnetism of 
the needle. 

Protection, Insulation Lightning 

— The protection of any instrument from the 
jumping of a spark across it from layer to 
layer. 

Protective Action.— (See Appendix— Ac- 
tion, Protective) 

Protective Throw. — (See Appendix — 
Throw, Protective) 

Protector, Cage, for Lightning Dis- 
charges A term sometimes employed 

for protecting sheaths for lightning dis- 
charges. (See Sheath, Protective) 

The method consists essentially in surrounding 
the body to be protected by conducting wires in, 
the form of a cage. 

Protector, Conduction Lightning 

A lightning protector by means of which a 
current is prevented from passing around the 
coil of a galvanometer or other needle instru- 
ment, and thus disturbing the magnetism of 
the needle. 
Protector, Insulation Lightning 



A lightning protector by means of which a 
discharge is prevented from jumping across 
the coil of an instrument from layer to layer, 
and thus damaging the insulation. 

Pull Bell, Circuit Closer for A 

device suitable for attachment to a mechanical 
door pull, so as to make an electrical contact 
for the ringing of an electric bell, without pre- 
venting the original bell from being operated 
by the mechanical pull. 



^In a system 



Pull-Off, Double Curve — 

of electric street railways a hanger supported 
by a lateral strain in opposite directions, used 
generally at the ends of both single and 
double curves and at intermediate points on 
double track curves. 
A double curve hanger. 

Pull-Off, Single Curve In a system 

of electric street railways a hanger supported 



Pul.] 



641 



[Raa. 



in one direction by a lateral strain except at 
the ends and on the inside curve of double 
tracks. 

A single curve hanger. 

Puncturation, Electro A term pro- 
posed for electro-puncture. 

Electro-puncture would appear to be the pref- 
erable term. (See, Puncture, Electro.) 

Push, Double-Contact A push pro- 
vided with two contacts, so arranged that the 
pressure of the push opens one contact and 
closes the other. 

Push, Morse A term sometimes 

employed in place of double-contact push. 
(See Appendix — Push, Double-Co?itact) 

Push, Pear A pear-shaped push 



provided for attachment to a flexible con- 
ducting cord. 



Push, Sounder 



-An apparatus, con- 



sisting of a push so combined with a sounder 
as readily to enable the one pushing it to 
know whether a distant bell has rung or not 
on the depression of the push button. 

Push Switch.— (See Appendix— Switch, 
Push.) 

Pyro-Electric Crystal.— (See Appendix— 
Crystal, Pyro-Electric.) 

Pyrogravure.— A process for the decora- 
tion of wood, copper or glass by the burning 
action of an electrically or otherwise heated 
tool. 



Q. — A symbol used for quantity of elec- 
tricity. 
The defining equation is Q = CT. 

Quad. — An abbreviation sometimes em- 
ployed for a unit of self-inductance. (See 
Quadrant?) 

The same abbreviation is also employed for 
quadruplex, but the context will generally pre- 
vent any confusion. 

Quadmeter. — A secohmmeter. (See Sec- 
ohmmeter.) 

Quadrantal Deviation of Mariner's Com- 
pass. — (See Appendix — Deviation, Quad- 
rantal, of Mariner's Compass) 

Quadruplex Telegraph.— (See Appendix 
— Telegraph, Quadruplex) 

Quality of Radiation.— (See Appendix — 
Radiation, Quality of.) 



Quantity Meter.— (See Appendix— Meter 
Quantity.) 

Quick Break.— (See Appendix— Break, 
Quick) 

Quick-Break Switch.— (See Appendix — 
Switch, Quick-Break) 

Quickened. — A term employed in electro- 
plating for a surface which has been prepared 
for the reception of a deposit of silver, by 
dipping the article into a quickening liquid. 
(See Solution, Quicking) 

Quickening Liquid. — (See Appendix— 
Liquid, Quickening) 

Quickening" Solution. — A quicking solu- 
tion. (See Solution, Quicking) 

Quicking Process. — (See Appendix — Pro- 
cess, Quicking) 



R. — A symbol used for resistance. 



The defining equation is R = — 



p. — A symbol used for specific electrical 
resistance or reluctivity. 

The symbol v has been proposed for this quan- 
31.— A symbol proposed for magnetic re- tity by Hospitalier. 
sistance or reluctance. R - M - s - Current.— (See Appendix-Cwr- 

L rent, R. M. S.) 



The defining equation is gft 



S 



Raad.— A name formerly given by the 



Rad.] 



642 



[Rai. 



Arabians to the torpedo or electrical ray. 
(See Torpedo, Electric. Ray, Electric?) 

Radial Current. — (See Appendix— Cur- 
rent, Radial?) 

Radian. — Unit angle. 
An angle such that its circular arc is equal 
in length to its radius. 

Its value in degrees is approximately 5 7° 17' 

45"- 

The radian is not employed in practical appli- 
cations, since the degree is the unit angle in 
ordinary use, but in mathematics angles are 
nearly always discussed in terms of the radian. 

Radian Per Second. — Unit angular 
velocity of a rotating body. 

Radiation, Efficiency of A term 

sometimes employed to represent the ratio of 
the non-luminous to the luminous radiation in 
the case of a body emitting light and heat. 

The efficiency of the ordinary sources of arti- 
ficial light is very low. The efficiency of the 
radiation of the firefly or glow-worm is very 
high, practically all its radiation belonging to the 
luminous type. 

Radiation, Electric The transfer- 
ence of electric energy by means of waves 
set up in the surrounding ether. 

During the oscillatory discharge of a Ley den jar, 
or, in general, during any disruptive discharge, 
the electricity surges or rushes to and fro, send- 
ing out or radiating its energy into the surround- 
ing ether by means of waves. 

It does this until all its energy is either directly 
dissipated in this manner, or is converted into 
heat in the conductor, which is afterwards dis- 
sipated as heat-waves. 

The lengths of the waves thus sent out into 
space by means of direct radiation of the electri- 
cal energy depend on a variety of circumstances, 
the most important of which are : 

(1.) On the capacity of the condensers. 

(2.) On the self-induction of the radiating 
system. 

Radiation, Intensity of The ratio 

existing between the amount or quantity of 
radiation and the surface. 

Radiation, Quality of Variations 

in the radiation due to differences, both in the 



various wave lengths present and in the 
polarization. 

Radiation, Selective — Radiation 

limited to waves of a particular wave length. 

The character of the radiation depends. 

(1.) On the nature of the body. 

(2.) On the condition of its surface. 

(3,) On the temperature. 

Langley has shown that in the case of a lumin- 
ous body the proportion existing between the 
visible radiation and the invisible radiation varies 
greatly in different cases. In the case of a gas 
flame, 2.4%" of the radiation is luminous. In the 
case of the arc light about 10 per cent, is lumin- 
ous, while in the light emitted by the firefly or 
the glow-worm practically all the radiation is 
luminous. 

Radiator, Electric An electric 

heater so placed as to radiate its heat into 
the room or space to be heated. 

Any electric heater applied to heat the air or 
space that surrounds it may be regarded as an 
electric radiator. 

Electric radiators are generally so placed as to 
prevent direct contact with their heated surfaces. 

Radiophonic Sounds.— (See Appendix — 
Sounds, Radiophonic?) 

Railroad, Conductor System for 



A system for the propulsion of cars by 
means of electricity taken from a conductor 
placed near the road. (See Railroads, Elec- 
tric, Dependent System of Motive Power 
for) 

Railway, Electric, Battery System for 

A system for the propulsion of cars 

by means of electricity derived from storage 
or secondary batteries placed on the cars. 
(See Railroads, Electric, Independent Sys- 
tem of Motive Power for) 

Railway Generator. — (See Appendix— 
Generator, Railway) 

Raindrops, Electrical Aggregation of 

The coalescence of a number of 

separate raindrops into a single drop by the 
action of electricity. 

Rayleigh has observed the fact that if a verti- 
cal water-jet is subjected to the influence of an 
electrified stick of sealing wax held a short dis- 



Kat.J 



643 



[Rep. 



tance from the drop, the jet at once shrinks upon 
itself and greatly changes its appearance, a great 
number of separate drops collecting into single 
larger drops. 

Examining the drops by means of intermittent 
illumination the coalition of the separate drops 
can be readily seen. When no difference of 
potential exists between the separate drops they 
do not unite or coalesce, but when a difference 
of potential exists, coalescence occurs, and, since 
such coalescence causes an increased difference of 
potential, the drops rapidly increase, both in size 
and potential difference. 

Eatio of Conversion.— (See Appendix — 
Conversion, Ratio of.) 

Ratio of Transformation. — (See Appen- 
dix — Transformation, Ratio of.) 

Rays, Anodic, of Vacuum Tube 



The rays of light which appear in the neigh- 
borhood of the anode of a vacuum tube 
through which a rapid electric discharge is 
passing. 

Rays, Kathodic, of Vacuum Tube 

The rays of light which appear in the neigh- 
borhood of the kathode of a vacuum tube 
through which a rapid electric discharge is 
passing. 

Reactance.— A term proposed by Hospital- 
ier for a quantity of the same dimensions as 
the resistance, which does not absorb energy, 
and the square of which added to the square 
of the resistance gives the square of the im- 
pedance to simple harmonic currents. 

Calling Ceff, the effective current, E e ff, the 
effective electromotive force, gd, the pulsation, or 
2 Tt times the frequency, then — 

Eeff 
C e ff = 



i/r2 +(- l -^k)'' 



The factor in the parenthesis is what Hospital- 
ler proposes to call the reactance. 

Reaction, Armature The reactive 

magnetic influence produced by the current 
in the armature of a dynamo or motor upon 
the magnetic circuit of the machine. 

Red Magnetic Pole.— (See Appendix— 
Pole, Magnetic, Red.) 



Redressed.— Commuted or caused to take 
the same direction. 

The commutator redresses or commutes the 
currents in the armature and causes them to flow 
in the same direction. 

Regenerative Cell.— (See Appendix— Cell, 
Regenerative?) 
Region, Equatorial, of Magnet A 

term sometimes employed for the portions of 
a magnet which lie near the equator. (See 
Magnet, Equator of) 

Registering Declination Magnetometer. 

— (See Appendix — Magnetoineter, Register- 
ing Declination.) 

Regulating Socket— (See Appendix— 
Socket, Regulating.) 

Relay Contact— (See Appendix— Contact, 
Relay.) 

Relay, Kick of (See Appendix — 

Kick of Relay.) 

Relay, Polar, Telegraphic A tele- 
graphic relay provided with a polarized arma- 
ture. (See Armature, Polarized) 

Reluctancy. — An alternative word pro- 
posed for reluctivity. (See Reluctivity. Re- 
luctance, Magnetic) 

Reluctivity, Proposed A. I. E. E. Defini- 
tion for The reciprocal of permea- 
bility, 

Remanent Magnetism. — (See Appendix — 
Magnetism, Remanent) 

Repeater, Automatic A telegraphic 

repeater which acts automatically. (See Re- 
peaters, Telegraphic) 

Repeater, Button A form of 

manual repeater. (See Repeaters, Tele- 
graphic) 

Repeater, Electro-Magnetic, Callan's 

— A term formerly applied to a variety of 
vibrating contact breaker. 

Repeater, Manual A telegraphic 

repeater which is operated by hand. (See 
Repeaters, Telegraphic) 

Repeater, Non- Automatic A term 

sometimes employed for manual repeater. 
(See Repeaters, Telegraphic) 



Rep.] 



644 



[Key. 



Repeating Telegraphic Station. — (See 
Appendix — Station, Repeating Telegraphic?) 

Repulsion Electrometer. — (See Appendix 
— Electrometer, Repulsion?) 

Residue, Electric A term proposed 

for residual charge. 

The term electric residue would appear to be 
entirely unnecessary. 

Resistance, Apparent — A term 

sometimes employed for the impedance of a 
circuit or the resistance it offers to the pas- 
sage of an alternating current. 

Resistance, Conduction The re- 
sistance offered by a conductor to the pas- 
sage of an electric current. 

Resistance, Conductor A term fre- 
quently employed for copper resistance. (See 
Appendix — Resistance, Copper?) 

Resistance, Contact A resistance 

produced by the contact of two surfaces. 

Resistance, Copper A term fre- 
quently employed for expressing the resist- 
ance of a telegraphic conductor. 

The value of the copper resistance is generally 
expressed in ohms-per-mile, ohms-per-knot or 
ohms-per-kilometre. 

Resistance, Electric, of Metals, Effect of 
Temperature on A change in the re- 
sistance of a metal following a given change 
in temperature. 

At decreasing temperatures an increase occurs 
in the electric conducting power of the metals. 

Dewar, by means of the intense cold produced 
by liquefied oxygen, found that at very low tem- 
peratures all pure metals increase in their conduct- 
ing power as the temperature decreases. The 
temperature curve is such that, the resistivity of 
pure metals would be zero at, or even before, the 
absolute zero of temperature. In such a case, 
if a wire or conductor of pure metal were placed 
in the approximately absolute zero of inter- 
stellar space, electricity would pass through it 
without loss. This must, however, be regarded 
only as a hypothesis. 

According to Dewar, most non-conducting 
bodies show a conductivity decreasing with the 
temperature. 



Resistance of Telegraphic Leah.— (Sec 
Appendix — Leak, Telegraphic, Resistance 
of.) 

Resistance, Passive A term some- 
times employed for the ohmic resistance of a 
circuit. (See Resistance, Ohmic.) 

Resistance, Specific Magnetic A 

word proposed for reluctivity. (See Reluc- 
tivity.) 

Resistance, Transition A term 

formerly employed for the resistance experi- 
enced by a voltaic cell shortly after closing a 
circuit. 

The transition resistance was inferred fr«m the 
decrease in the current strength, and was for- 
merly attributed to a change in the character of 
the electrode. It is now generally ascribed to the 
electromotive force of polarization. 

This term is also employed in a somewhat 
similar sense in electro-therapeutics. (See Re- 
sistance, Transition. ) 

Resistivity. — A term proposed for specific 
resistance. (See Resistance, Specific.) 

Resistivity is the inverse of specific conductivity. 

Resonance, Acoustic — The excite- 
ment or production of waves or vibrations of 
sound in an elastic body by means of succes- 
sive impulses received by such body from the 
sound waves striking it. 

Acoustic resonance is a particular case of sym- 
pathetic vibrations. Like all cases of such vibra- 
tions, there must exist between the sonorous body 
in which the waves of vibrations are excited, and 
the body which is producing the exciting waves, 
an identity of wavelength; or, in other words, 
there must exist between the two strict syn- 
chronism, so that the effects of timed impulses 
may be permitted. 

Resonant Circuit. — (See Appendix — Cir- 
cuit, Resonant?) 

Resultant Fault. — (See Appendix — Fault, 
Resultant?) 

Resultant Magnetic Pole. — (See Appendix 
— -Pole, Resultant Magnetic?) 

Retarding Disc. — (See Appendix — Disc, 
Retarding. 

Reversals. — In telegraphy, alternate cur- 
rent signals transmitted for the purpose of 



Rev.] 



645 



[Sea. 



adjustment ; as, for example, in obtaining a 
duplex balance. 

Reversible Heating- Effect of Electric- 
ity. — (See Appendix — Electricity, Reversible 
Heating Effect of) 

Rheostat, Adjustable An adjustable 

resistance, in a compound-wound dynamo- 
electric machine, employed to adjust com- 
pounding for a greater or less than tested 
speed or a greater or less wiring loss. 

A term someiimes employed for a rheostat, 
or a resistance that can readily be adjusted 
or altered. (See Rheostat) 

Strictly speaking, any rheostat is an adjustable 
resistance ; therefore, this latter use of the term 
adjustable rheostat would seem to be unnecessary. 

Ribbon Induction Coil. — (See Appendix 
— Coil, Induction Ribbon.) 

Right-Hand Trolley Switch.- (See Ap- 
pendix — Switch, Right-Hand Trolley?) 

Right-Handed Helix. — (See Appendix — 
Helix, Right-Handed) 

Right-Handed Rotation. — (See Appendix 
— Rotation, Right-Handed) 

Right-Handed Spiral. — (See Appendix — 
Spiral, Right-Handed) 

Ring, Galvanic A term sometimes 

applied to a galvanic, or, more properly speak- 
ing, voltaic circuit. (See Circuit, Voltaic) 

Ripple Marks. — (See Appendix — Marks, 
Ripple, Electrical) 

Rise. — In interior house wiring that portion 
of a conductor which rises vertically from one 
floor to another. 

Rocking* Switch. — (See Appendix — 
Switch, Rocking) 



Rosette, Ceiling A ceiling block of 

ornamental and rosiform design. 

Rotary Converter.— (See Appendix- Con- 
verter, Rotary) 

Rotary Transformer.— (See Appendix — 
Transformer, Rotary) 
Rotation, Electro-Dynamic " The 

rotation of a magnetic field produced as thi 
resultant of two or more magnetic or mag- 
netizing forces of variable intensity acting at 
an angle to one another, whose maxima do 
not coincide, but whose periods are the same." 
— Gutinann. 

Rotation, Left-Handed A rotation 

the direction of which is opposite to that of 
the hands of a watch when one looks directly 
at the face of the watch. 

Rotation, Right-Handed A rota- 
tion the direction of which is the same as 
that of the hands of a watch when one looks 
directly at the face of the watch. 

A direction the same as that of an ordinary 
right-handed screw, when we turn the upper side 
of the right-hand outwards. 

Rubber Tape.— (See Appendix— Tape, 
Rubber) 

Rumble. — A barrel or other hollow box 
revolved by mechanical power in which small 
articles that are to be electro-plated are 
placed for the purpose of polishing them. 

When subjected to the rotation of the barrel 
the articles became polished by friction against 
one another. Some dry sawdust is frequently 
placed in the barrel, to aid in the polishing pro- 
cess. 

Running Torque of Motor.— (See Appen- 
dix — Torque, Running, of Motor.) 



s 



S.— A symbol proposed for surface. 

The defining equation is S = L X L« 

S. — An abbreviation proposed for second, 
the C. G. S. unit of time. 

S. N. Telegraphic Instrument.— (See Ap- 
pendix — Instrument, S. N., Telegraphic) 



S. P. Cut-Out— (See Appendix— Cut- Out, 
S.F.) 

Sag of Conductor or Line Wire.— (See 
Appendix— Conductor or Line Wire, Dip of) 

Scalar Potential.— (See Appendix— Po- 
tential, Scalar) 



Sec] 



646 



[Ser. 



Secondary Spiral of Induction Coil. — 

(See Appendix — Spiral, Secondary, of In- 
duction Coil.) 

Section Box. — (See Appendix — Box, Sec- 
tion^ 

Segment, Dark, of Aurora A dark 

or non-illumined portion of the sky in the 
neighborhood of an aurora. 

Segment, Unlighted, of Aurora 



A term employed by Nordenskjold in place of 
dark segment of aurora. (See Appendix — 
Segment, Dark, of Aurora?) 

Selective Emission. — (See Appendix — 
E?nission, Selective.) 

Selective Radiation. — (See Appendix — 
Radiation, Selective.) 

Selective Signal. — (See Appendix — Sig- 
nal, Selective.) 

Selective Signalling Apparatus.— (See 
Appendix — Apparatus, Selective Signal- 
ling.) 

Self-Compounding Polyphase Genera- 
tor. — (See Appendix — Generator, Self-Com- 
pounding Polyphase.) 

Self-induction Coil.— (See Appendix — 
Coil, Induction, Self.) 

Self-Starting Synchronous Motor.— (See 
Appendix — Motor, Synchronous, Self-Start- 
ing) 

Semaphoric Electroscope. — (See Appen- 
dix — Electroscope, Semaphoric) 

Semi-Circular Deviation of Mariner's 
Compass. — (See Appendix — Deviation, Semi- 
circular, of Mariner s Compass.) 

Semi-Conductors. — (See Appendix— Con- 
ductor, Semi) 

Sensitiveness of Telephone.— (See Ap- 
pendix — Telephone, Sensitiveness of) 

Separable Conducting Cord Tip.— (See 
Appendix — Tip, Conducting Cord, Sep- 
arable) 

Separate-Coil Alternator. — (See Appen- 
dix — Alternator, Separate-Coil) 

Separate - Coil Alternating Dynamo- 
Electric Machine. — (See Appendix— Ma- 



chine, Dynamo-Electric , Separate-Coil Al- 
ternating) 

Separately-Excited Alternating Dynamo- 
Electric Machine. — (See Appendix — Ma- 
chine, Dynamo-Electric , Separately Excited 
Alternating) 

Separately-Excited Alternator. — (See 
Appendix — Alternator , Separately-Excited) 

Separator, Electro-Magnetic A 

device for separating the useful ore from the 
dross in low grade finely granulated iron ores. 
Septum. — A wall or diaphragm through 
which osmotic diffusion can take place. (See 
Osmose. Osmose, Electric) 

Series, Branched A term some- 
times employed in place of series-multiple. 
(See Series-Multiple) 

Series Connection of Alternators. — (See 
Appendix — Alternators, Series Connection 
of) 

Series, Potential, Dynamos Coupled in 

A term sometimes employed in teleg- 
raphy for a particular coupling of dynamo- 
electric machines in series. 

In the application of a number of dynamo-elec- 
tric machines to the operation of telegraphic lines 
in a central station, where a number of different 
lines enter or leave the station, different voltages 
are required on the different lines. These differ- 
ent voltages are most readily obtained by coup- 
ling the machines in what is called potential 
series. 

In potential-series coupling, the dynamos are 
connected together in series, that is, the positive 
brush of one dynamo is connected to the negative 
brush of another, its positive brush to the nega- 
tive of another, and so on throughout the series. 
One terminal of the battery of dynamos is 
grounded, and the other connected to the line. 
The terminals of the various telegraphic lines are 
then connected to points of junction of contiguous 
dynamos where their opposite brushes are con- 
nected. By these means the requisite difference 
of potential is readily obtained. 

Series Working of Alternating Dynamo- 
Electric Machines. — (See Appendix — Ma- 
chines, Dyna?no-Electric, Alternating, Series 
Working) 



Ser.] 



647 



[Sig. 



Service Block. — (See Appendix— Block, 
Service, 

Shackle Insulator. — (See Appendix — In- 
sulator, Shackle!) 



Shell, Simple Magnetic 



-A mag- 



Shading, Magnetic 



-A term some- 



times employed for magnetic screening. (See 
Screening, Mag?ietic. ) 

Sheath, Closed-Conducting, for Light- 
ning Protection A form of lightning 

conductor proposed by Maxwell, consisting 
essentially of a net-work or cage-like con- 
ductor surrounding the house or building to 
be protected. 

The theory for the protection of a building by 
means of a conducting sheath is based on the well 
known fact that there is no trace of electrostatic 
charge inside a hollow conductor. 

It is now well known that there are circum- 
stances under which the closed-conducting circuit 
does not thoroughly protect a building on which 
it is placed. If the number of such circuits is suf- 
ficiently great so as to form a close- meshed cage, 
the protection thus afforded is excellent. Such a 
sheath, however, might be dangerous to touch. 

Lodge, who has studied the matter of lightning 
protection very thoroughly, thus humorously re- 
marks concerning the system of sheath lightning 
protection: 

' ' It would be unpleasant, when you are driven 
home out of a storm, to find it so highly charged 
as to knock you down directly you tried to enter. 
An earth connection is necessary as well." 

Shell, Complex-Magnetic A mag- 
netic shell whose strength varies from one 
part to another. 

A complex magnetic shell will result from the 
overlapping of a number of simple magnetic 
shells. 

Shell, Copper, of Electrotype A 

thin sheet of electrolytically deposited copper. 

The copper shell is rendered sufficiently rigid 
for use by being covered with a backing of type 
metal. 

In order to permit this metal readily to adhere 
to the back of the shell it is thoroughly cleansed 
and then covered on the back with sheets of tin- 
foil, which are melted in the 'backing-pan pre- 
paratory to receiving the coating of type metal. 



netic shell whose strength is everywhere 
equal. 

Shifting of Spot of Light.— A movement 
of a spot of light on a scale produced by 
other causes than those acting during the 
proper operation of the instrument, and caus- 
ing the spot of light to move away from its 
true zero position. 

In the case of a galvanometer the spot of light, 
instead of remaining at the zero point, shifts or 
moves from one side to another of the zero point. 

This movement is sometimes called the drifting 
of the zero point. 

The shifting of the spot of light is, of course, 
caused by the drift of the needle. 

Shunting Air Gap.— (See Appendix — 
Gap, Air, Shunting.) 

Shunt-Out. — A cut-out device for remov- 
ing an electro-receptive device from a circuit, 
without breaking the circuit, by providing a 
short circuit between its terminals. 

An electro-magnetic cut-out provides a shunt- 
out of the device it is desired to cut-out. It will 
be seen, however, that all a shunt-out does is to 
provide a by-path, the resistance of which is so 
small as compared with the resistance of the de- 
vice cut-out, that practically all the current flows 
past the device through the shunt path, thus prac- 
tically cutting it out from the circuit ; or, more 
properly speaking, cutting it out from the opera- 
tive current. 

Side Arms. — (See Appendix — Anns, 
Side.) 

Signal, Individual In any system 

of electric communication devices by means 
of which bells or other signals, at two or 
more stations electrically connected in the 
same circuit, are not operated at all of the 
stations by the calls sent over the line to the 
call bell at any particular station, but in which 
each particular bell is only operated by its own 
call to the exclusion of the other calls. 

Signal, Selective A term some- 
times employed in place of individual signal. 
— (See Appendix — Signal, Individual.) 

Signal, Telegraphic, Audible Tele- 
graphic signals that can be heard. 



Sig.] 



648 



[Sol. 



Examples of audible telegraphic signals are to 
be found in the signals given by various sounders 
of the Morse type. 

The signals of electric bells are also audible 
signals. 

Signal, Telegraphic, Evanescent 

Telegraphic signals that leave no permanent 
record. 

Examples of evanescent telegraphic signals are 
found in the audible signals produced by most 
forms of telegraphic sounders. 

Signal, Telegraphic, Permanent 

Telegraphic signals that are recorded by any 
means which leaves a permanent record. 

The various forms of recording or registering 
apparatus employed in telegraphy produce per- 
manent signals. — (See Recorder, Morse. Rec- 
order, Chemical, Bain's. Recorder, Siphon. Reg- 
ister, Telegraphic.) 

Signal, Telegraphic, Visual Tele- 
graphic signals that can be seen. 

Examples of visual telegraphic signals are to be 
found in the various galvanometric receiving ap- 
paratus employed in cable telegraphy, or, in gen- 
eral, in needle telegraphy. The signals received 
on the siphon recorder, for example, are visible 
signals. (See Recorder, Siphon.) 

Simple Alternating or Two-Phase Cur- 
rent. — (See Appendix — Current, Simple or 
Two-Phase Alternating) 

Simple-Magnetic Shell. — (See Appendix 
— Shell, Simple- Magnetic.) 

Single-Current Telegraphic Working. 
— (See Appendix — Working, Single-Cur- 
rent, Telegraphic.) 

Single Curve Pull-Off.— (See Appendix— 
Pull-Off, Single Curve.) 

Single-Liquid Voltaic Cell.— (See Cell, 
Voltaic, Single-Fluid) 

Single-Phase Motor. — (See Appendix — 
Motor, Single-Phase.) 

Single-Pole Cut-Out. — (See Appendix — 
Cut-Out, Single-Pole) 

Single- Wire System for Electric Light 
Leads. — (See Appendix — Leads, Single- 
Wire System for Electric Light) 

Sinusoidal Current. — (See Appendix — 
Current, Sinusoidal) 



Six-Pole Dynamo-Electric Machine. — 

(See Appendix — Machi?ie, Dynajno-Electric, 
Six-Pole) 

Six- Wire System.— (See Appendix— Sys- 
tem, Six- Wire) 

Skew Adjustment of Carbons in Arc 
Lamp. — (See Appendix — Carbons, Skew Ad- 
justment of, in Arc Lamp) 

Skin Currents. —(See Appendix— Cur- 
rents, Skin) 

Sliding Joint.— (See Appendix— -Joint, 
Sliding.) 

Slinging Wires.— (See Appendix— Wires, 
Slinging) 

Slipping of Belt— (See Appendix— Zfe#, 
Slipping of) 

Smashing Point of Incandescent Elec- 
tric Lamps. — (See Appendix — Poi?it, Smash- 
ing, of Incandescent Electric Lamps) 

Snapper Sounder. — (See Appendix — 
Sounder, Snapper) 

Socket Base. — (See Appendix — Base, 
Socket) 

Socket, Pendant An attachment to 

a socket provided with a chain or chains for 
turning on or off a lamp not readily accessi- 
ble. 

Socket, Regulating A lamp socket 

fitted with an adjustment under control of a 
key or switch for regulating the degree of 
incandescence of the filament. 

Socket, Temporary A simple and 

unfinished form of socket for holding a lamp 
temporarily. 

Solenoid, Anomalous A term 

sometimes applied to a solenoid with conse- 
quent poles. (See Solenoid, Practical) 

Solution, Amalgamating A solu- 
tion of mercury employed for readily amal- 
gamating the zincs of a voltaic battery. 

Maycock gives the following as a good amalga- 
mating solution: 

Two pounds mercury. 

Five pounds nitric acid. 

Ten pounds hydrochloric acid. 

The mercury and nitric acid are mixed together, 



Son.] 



649 



[Spa. 



and, after the mercury is dissolved, the 10 pounds 
of hydrochloric acid are added. 

To use this liquid the zincs are first cleansed 
and then dipped into the solution and afterwards 
rinsed with clean water. 

Sonometer. — A monochord. (See Appen- 
dix — Monochord?) 

Sonometer Interrupter. — (See Appendix 
— Interrupter, Sonometer?) 

Sorter, Electro-Magnetic An elec- 
tro-magnetic separator, sometimes applied to 
a magnetic separator. (See Appendix — Sep- 
arator, Electro-Magnetic.) 

Sounder Push. — (See Appendix — Push, 
Sounder?) 

Sounder, Snapper A sounder for 

producing the sounds corresponding to the 
Morse characters, as they are heard on a 
sounder, in which the audible signals are 
produced by the flexure of a spring. 

A sounder snapper consists essentially of a 
dented spring plate firmly connected at one end 
and the other end moved to-and-fro by hand. 

It is used to produce sounds similar to those of 
the regular electro-magnetic sounder, only, in- 
stead of being operated by an electric current, it is 
operated solely by hand. 

Sounder, Telegraphic Box — A 

sounder, the receiving magnets of which are 
enclosed in a hollow box for the purpose of 
increasing the intensity of the sound by means 
of resonance. 

Sounds, Radio-phonic Sounds re- 
sulting from the direct action of radiation on 
certain bodies. (See Sonorescence.) 

It is the photophonic sounds, produced in the 
receiving instrument of a photophone, that are 
employed for the transmission of speech or other 
intelligence. (See Photophone?) 

Mercadier gives the following conclusions as 
the result of his experiments on radiophonic 
sounds: 

(i.) " The radiophone (radiophonic sound) 
does not appear to be an effect produced by the 
mass of the receiving plate vibrating transversely, 
like an ordinary vibrating plate. The nature of 
the molecules of the receiver and their mode of 
aggregation do not appear to exercise a predom- 
inant influence on the production of sounds. 



" The radiophonic phenomena appear to result 
principally from an action exercised at the sur- 
face of the receiver, and are amplified when this 
surface is covered with substances like lamp- 
black, platinum-black, and the like. 

(2.) " Radiophonic sounds result from the direct 
action of radiations on the receivers. Radiophonic 
sounds are produced principally by the undula- 
tions of great length of wave, called ' calorific.' 

(3.) " The medium in which radiophonic vi- 
bration is produced is the layer of condensed air 
on the surface of the receivers. This layer of air, 
particularly when the surfaces are smoked, or 
covered with a substance absorbing heat, is alter- 
nately heated and cooled by intermittent radia- 
tions, with the result that periodic and regular 
dilatations and contractions are set up ; hence a 
vibratory movement communicated to the ad- 
jacent gaseous layers, which also vibrate directly 
under the same influence. 

(4. ) " Radiophonic sounds cannot be produced 
unless the medium which surrounds the receiving 
surfaces is gaseous. A liquid or solid medium 
cannot produce them; but a gaseous medium 
containing vapor, particularly vapor of am- 
monia or ether, develops them in a remarkable 
way : those vapors which have the greatest ab- 
sorbing thermic power give out the greatest 
effects." 

Source, Magnetic Any arrangement 

of parts capable of producing lines of mag- 
netic force. 

A permanent magnet, an electro-magnet, or a 
circuit through which an electric current is 
passing, may act as a magnetic source. 

Spark Chronograph. — (See Appendix — 
Chronograph, Spark.) 

Spark Discharge. — (See Appendix — Dis- 
charge, Spark.) 

Spark, Electric The phenomena 

produced by a disruptive discharge in the air 
space or gap through which the discharge 
passes. 

Spark, Negative A spark produced 

by the discharge of a negatively charged con- 
ductor. 

Spark, Positive A spark produced 

by the disruptive discharge of a positively 
charsred conductor. 



Spa. 



650 



[Sta.. 



Sparking Terminals. — (See Appendix — 
Terminals, Sparking?) 

Speaking Telegraph. — (See Appendix — 
Telegraph, Speaking?) 

Speaking-Tube Annunciator. — (See Ap- 
pendix — Annunciator , Speaking- Tube?) 

Specific Conductance. — (See Appendix — 
Conductance, Specific?) 

Specific Dielectric Capacity. — (See Ap- 
pendix — Capacity, Specific Dielectric?) 

Specific Energy. — (See Appendix — En- 
ergy, Specific. 

Specific Inductance. — (See Appendix — 
Inductance, Specific?) 

Specific Magnetic Resistance.— (See Ap- 
pendix — Resistance, Specific Magnetic?) 

Specific Magnetism.— (See Appendix — 
Magnetism, Specific?) 

Spectro-Photometer. — (See Appendix — 
Photometer, Spectro?) 

Spectrum, Magnetic A term some- 
times employed in place of magnetic figure 
or magnetic field. 

The term magnetic spectrum is unfortunate 
since magnetic figures so produced can hardly be 
regarded as spectra, but merely as collections 
of iron filings arranged in the order which the 
lines of magnetic force take in the space or at- 
mosphere outside the magnet. 

Speed, Inductance A term pro- 
posed for the product of a coefficient of self- 
induction by an angular velocity. 

Speeding of Machine.— (See Appendix— 
Machine, Speeding of?) 

Spiral. — A term sometimes employed in 
electricity and magnetism in place of an open 
coil. (See Coil, Electric?) 

Spiral, Anomalous A term some- 
times employed in place of an anomalous 
helix or solenoid. (See Appendix — Solenoid, 
Anomalous?) 

Spiral, Left-Handed A term some- 
times employed in place of left-handed 
solenoid. (See Solenoid, Left-Handed. Sole- 
noid, Practical?) 



Spiral, Magnetic 



■A term some- 



times employed in place of magnetic helix. 
(See Coil, Electric?) 

Spiral, Magnetizing A term some- 
times employed in place of a magnetizing 
helix or coil. (See Coil, Electric?) 

Spiral, Primary, of Induction Coil 

A term sometimes employed for the primary 
of an induction coil. (See Coil, Induction?) 

Spiral, Right-Handed A term 

sometimes employed in place of right-handed 
solenoid. (See Solenoid, Right-Handed. 
Solenoid, Practical?) 

Spiral, Secondary, of Induction Coil 

— A term sometimes employed for the sec- 
ondary of an induction coil. (See Coil, In- 
duction?) 

Spontaneous Electricity. — (See Appendix 
— Electricity, Spontaneous?) 

Spools, Field, of Dynamo-Electric Ma- 
chine A term sometimes employed 

for the forms on which the field coils are 
wound. 

Spring Relay Contact. — (See Appendix — 
Contact, Spring Relay?) 

Spring Voltmeter. — (See Appendix — 
Voltmeter, Spring?) 

Standard Clock. — (See Appendix— Clock, 
Standard?) 

Standard Trolley Switch. — (See Appen- 
dix — Switch, Standard Trolley?) 

Standards. — Telegraphic or telephonic 
supports placed on the roof of a building for 
the purpose of supporting telegraphic or 
telephonic wires or conductors. 

Standards, Dynamo A term ap- 
plied to the supports for the bearings of a 
dynamo. 

Starting Box of Shunt- Wound Motor.— 
(See Appendix— Box, Starting, of Shunt- 
Wound Motor?) 

Starting Current of Motor. — (See Appen- 
dix — Current, Starting, of Motor?) 

Starting Torque of Motor.— (See Appen- 
dix — Torque, Starting, of Motor?) 

Static Transformer. — See Appendix — 
Transformer, Static?) 



Sta.] 



651 



[Str. 



Station, Repeating Telegraphic 

A station situated at some intermediate 
point on a long telegraphic line where the 
currents from the sending station are passed 
through a relay by means of which they are 
sent on to the next station by means of a 
current from a local battery. 

Station, Translating Telegraphic 

— A receiving station. 

The station at which the signals are re- 
ceived. 

Stay-Eye Clips. — (See Appendix — Clips, 
St ay- Eye?) 

Steeling, Electro The art of cover- 
ing copper electros with hardened iron. 

Steel- Yard Ammeter. — (See Appendix — 
Ammeter, Steel- Yard?) 

Steeps.— A word sometimes employed in 
electro-plating for dips or dipping liquids or 
solutions. 

Steno - Telegraphy. — (See Appendix — 
Telegraphy, Steno?) 

Stereotype, Electro A word some- 
times employed for electrotype. 

The term electrotype would appear to be 
preferable. 

Sticking of Magnetic Armature.— (See 

Appendix — Armature, Magnetic Sticking 
of) 
Stimulation, Unipolar, of a Nerve 

— The stimulation of a nerve produced by 
the application of a single electrode to the 
nerve. 

This term was proposed by Du Bois Reymond, 
and is sometimes employed in electro-therapeu- 
tics. According to Reymond unipolar stimula- 
tion of a nerve is due to the action of the to- 
and-fro motions of the electric current between 
the free ends of the open induction circuit at the 
moment of induction. 

Stimulus, Electrical, of Nerve 

The effect which electricity produces by its 

passage through a nerve. 
Landois and Sterling give the following facts 

concerning the electric stimulation of a nerve : 
The stimulation is more powerful— 
(i.) At the moment the current is completed. 



(2.) At the moment the current ceases. 

(3.) When a constant electric current increases-- 
or decreases in its strength. The more rapid the 
variations, the more energetic the stimulation. 

(4.) To stimulate a nerve, the current must 
have a certain duration. 

(5.) The electric current is most active when 
applied to the longer axis of the nerve, and be- 
comes inactive when applied at right angles to^ 
this axis. 

(6.) The greater the length of nerve treated by" 
the current, the smaller is the stimulus that is 
required. 

Stone, Bolognian A term origin- 
ally applied to a calcareous substance that 
became phosphorescent on exposure to light. 

Stoneware Dipping Basket— (See Appen- 
dix — Basket, Stoneware Dipping.) 

Stoneware Dipping Bowl.— (See Appen- 
dix — Bowl, Stoneware Dipping?) 

Stopping-Off Process.— (See Appendix — 
Process, Stopping-Off?) 

Stopping-Out Process.— (See Appendix — 
Process, Stopping-Out?) 

Storage Accumulator.— (See Appendix — 
Accumulator, Storage?) 

Storage Battery, Formed Plates of 

— (See Appendix — Plates, Formed, of Stor- 
age Cell?) 

Stove, Plate, Electric A form of 

electric stove in which the heat is imparted 
to the plate from a suitably shaped resist- 
ance. 

A form of plate stove is shown in Fig. 580, a 




Fig. j8o. Electric Plate Stove. 

part of the top being cut away to show the elec- 
tric heater. 

Strain. — The deformation produced by 
the action of a stress. 

Strain, Electrostatic A strain or 

deformation produced in any medium by 



Str. 



652 



[Swi. 



means of the stress caused by an electro- 
static field. 

Stranding of Conductor. — (See Appendix 
— Conductor, Stranding of.) 

Strap Key. — (See Appendix — Key, Strap.) 

Streams, Phantom A term some- 
times applied to a variety of the Tesla stream- 
ing discharge. (See Discharge, Streaming.) 

Striking Distance. — (See Appendix — Dis- 
tance, Striki?ig.) 

Striking Distance for Various Sub- 
stances. — (See Appendix — Distance, Strik- 
ing, for Various Substances.) 

Striking Mechanism of Arc Lamp.— (See 
Appendix — Lamp, Arc, Striking Mechan- 
ism of.) 

Stroboscope. — An instrument employed 
in the study of periodic motion. 

The stroboscope is based on the illumination at 
frequent intervals of the body whose motion is to 
be studied. 

Stroboscopic. — Of or pertaining to the 
stroboscope. 

Struck. — A word employed in electro- 
plating to characterize a surface that has 
been covered with a film of electro-deposited 
nickel by being placed in a bath and exposed 
for a few moments to the action of a strong 
current. 

When the surface of the article to be plated 
has been struck or covered with a thin film of 
nickel, the remainder of the coating is deposited 
on the surface by the action of a weaker current. 

Successive Contact Key.— (See Appendix 
— Key, Successive Contact?) 

Surging Circuit. — (See Appendix — Cir- 
cuit, Surging.) 

Surgings, Induced Electric Elec- 
trical surgings induced in neighboring con- 
ductors by means of electrical surgings or 
oscillating discharges. (See Discharge, 
Oscillating?) 

Suspension of Compass Needle, Cardan's 

A term sometimes employed for gim- 

bal suspension. (See Gimbals?) 

Sweeping-Out Charge.— (See Appendix— 

Charge, Sweeping-Out?) 



Swinging Annunciator.- 

-A?munciator, Swinging.) 



-(See Appendix 



Switch, Automatic Photo-Electric 

— A switch that is automatically opened or 
closed on the exposure of its face to differ- 
ences of illumination. 

A selenium cell is so placed in a circuit in com- 
bination with an electro-magnetic switch that 
when one of the selenium faces is exposed to the 
decreasing illumination of approaching night a 
current is produced by such decrease of light, the 
direction of which is such as to automatically 
turn on or light an electric lamp, and conversely, 
on the approach of daylight and the consequent 
increase of solar illumination, to turn off the 
light. 



— A contraction for 
(See Switch, Double- 



Switch, D. B. — 

double-break switch. 
Break?) 

Switch, D. P. A contraction for 

double-pole switch. (See Switch, Double- 
Pole?) 

— A switch whose 



Switch, Flush Key — 

mechanism is contained in a box, the face of 
which is flush with the wall or other support 
to which the switch is attached. 

The switch is opened or closed by means of a 
key. 




Fig. 581. Flush Key Switch. 

A form of flush switch is shown in Fig. 581 
in which a removable key, instead of the ordinary, 
fixed key, is employed for opening and closing the 
switch. 



Swi.] 



653 



[Sys. 



Switch, Four- Way A term some- 
times employed in place of four-point switch. 
(See Switch, Pour-Point.) 

Switch, Jack A term sometimes 

employed in place of spring-jack. (See 
Spring-Jack.) 

Switch, Left-Haiid Trolley In a 

system of electric street railways a trolley 
switch designed for use at a point where a 
branch trolley leaves the main line to the 
left-hand side in the going direction. 



•Any form of switch 



Switch, Lever — 

in which the circuit is closed or opened by 
means of the movement of a lever arm. 

Switch, Push A switch included in 

a push case and operated by means of a push 
button. 

In push switches successive motions of the but- 
ton make or break the circuit. 



■A switch by 



Switch, Quick-Break — 

means of which a circuit is rapidly or quickly 
broken. 

Switch, Right-Hand Trolley In a 

system of electric street railways a switch de- 
signed for use at a point where a branch 
trolley wire leaves the main line to the right 
in the going direction. 



Switch, Rocking 1 



-A form of switch 



operated by means of an electro-magnet by 
which storage cells are automatically removed 
from the circuit of the charging dynamo to 
prevent the battery from discharging through 
it in case the voltage of the dynamo falls 
below the E. M. F. of the battery. 



Switch, Standard Trolley In a 

system of electric railways the device em- 
ployed to hold together the trolley wires at 
any point where the wire branches, and for 
automatically guiding a trolley wheel along 
the wire over the track taken by the car. 

Switch, T. P. A contraction for 

Triple-Pole Switch. (See Appendix — Switch, 
Triple-Poie. 

Switch, Three-Way A term some- 
times employed in place of three-point switch. 
(See Switch, Three-Point.) 



Switch, Three-Way Trolley In a 

system of electric street railways, a trolley 
switch designed for use at a point where the 
line branches in three directions. 

Switch, Triple-Pole A switch con- 
sisting of a combination of three separate 
switches for opening or closing the three cir- 
cuits at the same instant. 

Symmetrical Electrometer.— (See Appen- 
dix — Electrometer, Symmetrical?) 

Symphonance.— A word proposed in place 
of resonance. (See Reso?ia?ice, Electric.) 
(See Appendix — Resonance, Acoustic?) 

Synchronous-Multiplex Telegraph.— (See 
Appendix— Telegraph, Synchronous-Multi- 
plex?) 

Synthesis, Electro The combina- 
tion of electro-positive and electro-negative 
radicals under the influence of electricity. 

Syringe, Battery A syringe ar- 
ranged to readily transfer the acid or spent 
liquids from a voltaic cell or battery for the 
introduction of fresh liquid. 

System, Delta Tri-Phase A tri- 

phase system in which the terminal connec- 
tions resemble in form the Greek letter delta. 

System, Electrically Tuned A 

term sometimes employed for a circuit or 
system of circuits that has been brought into 
electrical resonance with another circuit or 
system of circuits. (See Resonance, Elec- 
tric.) 

System, Five- Wire A system sim- 
ilar in its arrangements to the three-wire 
system in which four dynamos are connected 
to five wires or conductors. (See System, 
Three- Wire?) 

In such a case there are three wires or con- 
ductors occupying the position corresponding in 
general to the neutral wire or conductor in a 
three-wire system. 

System, Four- Wire A system sim- 
ilar in its general arrangement to the three- 
wire system, in which three dynamos are 
connected to four wires or conductors. (See 
System, Three- Wire?) 

In such a case there are two wires or conduct- 
ors occupying in general a position correspond- 



Sys.] 



654 



[Tel 



ing to the neutral wire of the three-wire system. 
(See System, Three-Wire.) 

System, Municipal, of Electric Lighting 

A series system of incandescent light- 



ing invented by Edison for use in cities, par- 
ticularly for street or window lamps, and 
operated at a total continuous current pressure 
of i ,000 volts. 



System, Six- Wire 



•A system sim- 



ilar in general to the three-wire system in 
which five dynamos are connected to six 
conductors or leads. (See Appendix — Sys- 
tem, Five- Wire.) 

System, Y Tri-Phase A tri-phase 

system in which the terminal apparatus re- 
sembles in form the capital letter Y. 



t. — A symbol used for time. 

t : m. — An abbreviation proposed for revo- 
lutions per minute, a practical unit of angular 
velocity. 

T. P. Switch. — (See Appendix — Switch, 
T. P.) 

Tap Wire in Quadruplex Telegraphy. — 
(See Appendix — Wire, Tap, in Quadruplex 
Telegraphy?) 

Tape, Kerite A kerite covered in- 
sulating tape. 

Tape, Rubber Insulating tape 

made of rubber. 

Tapper Key. — (See Appendix — Key, Tap- 
per.) 

Tapper, Magneto A term some- 
times employed in place of magneto key. 
(See Key, Magneto-Electric?) 

Tapper, Morse A form of tele- 
graphic key provided with two contacts, one 
in front and the other in the back, arranged 
so that the depression of the key makes one 
contact and breaks the other. 

Teeth, Pacinotti A term some- 
times employed in place of Pacinotti pro- 
jections. (See Projections, Pacinotti?) 

Telegram. — A telegraphic dispatch or com- 
munication. 

Literally, anything written by means of a tele- 
graph. 

Telegraph. — Any instrument or combina- 
tion of instruments for conveying a commu- 
nication or dispatch to a distance by means 
other than the unassisted voice. 



Telegraph, Acoustic —A general 

term embracing the apparatus employed in 
acoustic telegraphy. (See Telegraphy, 
Acoustic?) 

Telegraph, Automatic — A general 

term embracing the apparatus employed in 
automatic or machine telegraphy. (See 
Telegraphy, Automatic,) 

Telegraph, Chemical A general 

term embracing the apparatus employed in 
chemical telegraphy. (See Telegraphy 
Chemical?) 

Telegraph, Contraplex A general 

term embracing the apparatus employed in 
contraplex telegraphy. (See Telegraphy, 
Contraplex?) 

Telegraph, Dial A general term 

embracing the apparatus employed in dial 
telegraphy. (See Telegraphy, Dial.) 

Telegraph, Diplex A general term 

embracing the apparatus employed in diplex 
telegraphy. (See Telegraphy, Diplex?) 

Telegraph, Duplex A general term 

embracing the apparatus employed in duplex 
telegraphy. (See Telegraphy, Duplex, 
Bridge Method of. Telegraphy, Duplex, 
Differential Method of.) 

Telegraph, Electric An electrical 

instrument for conveying a communication 
or dispatch to a distance by means other than 
the unassisted voice. 

Electric telegraphs are of a great variety of 
forms. They may be divided into classes, either 
according to the number of dispatches they can 
simultaneously transmit, or according to the 



Tel.] 



655 



[Tel, 



method employed for transmitting or receiving 
the dispatches. 

According to the number of messages they can 
transmit simultaneously, telegraphs are divided 
into duplex, diplex, contraplex, quadruplex, 
multiplex, phonoplex, harmonic, synchronous- 
multiplex, etc., etc. 

According to the differences in the method of 
transmitting and receiving the messages, they are 
divided into the electro-magnetic, the needle, 
the chemical, the dial, the fac-simile, the writing, 
the acoustic, the speaking, the induction, the 
automatic, the fire-alarm, etc., etc. 

Telegraph, Electro-Magnetic — A 

general term embracing the apparatus em- 
ployed in the various systems of electro- 
magnetic telegraphy. 

Telegraph, Fac- Simile A general 

term embracing the apparatus employed in 
fac-simile telegraphy. (See Telegraphy, Fac- 
simile) 

Telegraph, Fire- Alarm A general 

term embracing the apparatus employed in 
fire-alarm telegraphy. (See Telegraphy, 
Fire-Alarm) 

Telegraph, Harmonic A general 

term embracing the apparatus employed in 
harmonic telegraphy. (See Telegraphy, 
Grays Harmonic Multiple) 

Telegraph, Induction A general 

term embracing the apparatus employed in 
induction telegraphy. (See Telegraphy, In- 
duction.) 

Telegraph, Multiplex — A general 

term embracing the apparatus employed in 
multiplex telegraphy. (See Telegraphy, 
Multiplex.) 

Telegraph, Needle A general term 

embracing the apparatus employed in needle 
telegraphy. (See Telegraphy, Needle Sys- 
tem of.) 

Telegraph, Phonoplex A general 

term embracing the apparatus employed in 
phonoplex telegraphy. (See Telegraphy, 
Phonoplex.) 

Telegraph, Quadruplex A general 

term embracing the apparatus employed in 
quadruplex telegraphy. (See Telegraphy, 



Quadruplex, Bridge Method of. Teleg- 
raphy, Quadruplex, Differential Method 
of.) 

Telegraph, Speaking A general 

term embracing the apparatus employed in 
speaking telegraphy. (See Telegraphy, 
Speaking. Telephone) 

Telegraph, Synchronous-Multiplex 

— A general term embracing the apparatus 
employed in synchronous-multiplex teleg- 
raphy. (See Telegraphy, Synchronous- 
Midtiplex) 

Telegraph, To To write or com- 
municate at a distance by means of the tele- 
graph. 

Telegraph, Writing —A general 

term embracing the apparatus employed in 
writing telegraphy. (See Telegraphy, 
Writing) 

Telegraphic Box Sounder. — (See Appen- 
dix — Sounder, Telegraphic Box) 

Telegraphic Interrupter.— (See Appen- 
dix — Interrupter, Telegraphic) 

Telegraphic Interruption. — (See Appen- 
dix — Interruption, Telegraphic) 

Telegraphic Polar Relay. — (See Appen- 
dix — Relay, Polar, Telegraphic) 

Telegraphic Spark Coil.— (See Appendix 
— Coil, Spark, Telegraphic) 

Telegraphist.— One skilled in the art of 
transmitting intelligence by means of the tele- 
graph. 

Telegraphy, Air A term some- 
times employed for induction telegraphy. 
(See Telegraphy, Induction) 

The term air telegraphy has been applied on 
account of the fact that the electric impulses on 
one line wire or conductor are transmitted across 
an air space to a neighboring line wire or con- 
ductor, i. e., the air acts as the dielectric through 
which the induction takes place. 

Telegraphy, Steno A system of 

telegraphy in which the sounds of a word are 
represented by characters in place of letters. 

Steno-telegraphy differs from ordinary telegra- 
phy in the same manner that shorthand writing 
differs from longhand writing. 



Tel.] 



056 



[Ten. 



The object of steno-telegraphy is, of course, to 
insure increased economy in speed. 

Tele-Indicator. — (See Append ix — Indi- 
cator, Tele.) 

Tele-Meteorograph.— A form of meteoro- 
graph. (See Appendix — Meteorograph.) 

Telephone Indicator. — (See Appendix— 
Indicator, Telephoned) 

Telephone, Pan -A word proposed 

for a certain sensitive form of telephone. 

The particular form of telephone for which the 
name pan-telephone was proposed was an instru- 
ment with a microphone transmitter. 

Telephone, Sensitiveness of The 

ability of a telephone properly to respond to 
currents much smaller than those required 
for the operation of some other telephonic 
apparatus. 

The telephone is characterized by its extreme 
sensitiveness, requiring, as it does, for its opera- 
tion a very small current. It is for this reason 
that the current produced in the telephone circuit 
by the induction of neighboring conductors 
causes the annoying cross-talk in the telephone. 

Telephone, Thermo A telephone 

transmitter consisting of a tense wire, one end 
of which is connected with the transmitting 
diaphragm, placed in circuit with a receiving 
telephone battery, and having a current pass- 
ing through it of sufficient strength to heat it. 

On speaking near the wire the waves in the 
air periodically cool the wire, and its resistance 
varies, and accordingly the current in the line 
varies. A thermo receiver is made in a similar 
manner, and the telephone current heats the 
wire periodically and sets the diaphragm in 
motion. 

Telephone Time Check.— (See Appendix— 
Check, Telephone Time?) 

Telephonic Meter. — (See Appendix— 
Meter, Telephonic) 

Telephonist. — One skilled in the art of 
telephony. 

Telephony. — The art of transmitting intel- 
ligence by the use of the telephone. (See 
Telephone.) 

Telephony, Duplex A system of 

telephony by means of which a single line 



wire or conductor can be simultaneously used 
by two subscribers. 

Telephony, Multiplex A system of 

telephony by means of which a single line 
wire or conductor can be simultaneously 
used by a number of subscribers. 

Tele-radiophone. — A form of radiophone 
arranged for the simultaneous transmission 
of telegraphic and telephonic messages. 

Tele-radiophone, Auto-reversible or Mul- 
tiple A photophone so arranged that 

a number of telegraphic communications may 
be simultaneously sent over a line wire or 
conductor either all in one direction or part 
in one direction and the remainder in oppo- 
site directions. u 

The adjectives auto-reversible and multiple refer 
to the fact that the messages can be transmitted 
either all in the same direction, or a number in 
one direction and the remainder in the opposite 
direction. 

A multiple auto-reversible tele-radiophone is an 
invention of Mercadier's, based on the electrical 
properties of selenium. 

A number of selenium cells of variable resist- 
ance are employed at the sending station, where 
they are placed in the circuit of a battery of a few 
elements and of a line wire extending to the 1 e- 
ceiving station, which is connected with a number 
of receivers equal to the number of selenium 
cells of variable resistance. 

When luminous radiations are intermitted so as 
to have the relative succession and duration of 
the characters of the Morse alphabet, and these 
impulses are sent over the line, they affect the 
receivers at the other end. Each transmitter 
sends into the line impulses of a definite rate and 
only affects that receiving instrument at the other 
end which is tuned in unison with it. The ap- 
paratus is similar in its general action to Gray's 
system of multiple harmonic telegraphy. (See 
Telegraphy, Gray' s Harmonic Multiple.) 

Telpher Locomotive.— (See Appendix — 
Locomotive, Telpher.) 

Temporary Socket. — (See Appendix— 
Socket, Temporary.) 

Tension, Difference of An objec- 
tionable term sometimes employed in place 
of difference of potential. 



Ter.] 



657 



[Tho. 



This use of the term should be strictly avoided, 
as it is unnecessary and to a great extent mean- 
ingless. 

Terella. — Literally, a little earth. 

A sphere of hardened steel, or, as used by Gil- 
bert, of loadstone, having marked thereon the 
poles and equator, and so magnetized that the dis- 
tribution of its magnetism shall resemble the dis- 
tribution of the earth's magnetism. 

Terminals, Sparking — Terminals 

between which a series of disruptive dis- 
charges are passed. 

Sparking terminals are generally provided with 
rounded or blunt or disc-shaped ends so as to pre- 
vent a convective discharge from taking place. 

Terrestrial Magnetic Induction. — (See 
Appendix — Induction, Mag7ietic, Terres- 
trial^) 

Tesla Discharge. — (See Appendix — Dis- 
charge, Testa.) 

Tesla Frequencies. — (See Appendix — Fre- 
quencies, Testa.) 

Test, Blavier's A test introduced 

by Blavier for localizing a single fault in a 
single telegraphic line or conductor by meas- 
uring the resistance at one end of the line 
when the other end is alternately freed and 
earthed. 

Test Board. — (See Appendix— Board, 
Test.) 

Test, Loop A localization test for a 

single fault in a loop of two telegraphic wires, 
or in a complete metallic circuit. 

Test, Overlap A localization test for 

a single fault in a single telegraphic line by ob- 
serving the resistance from each end and 
deducing from the amount to which the sum 
of the resistances overlap the total conductor 
resistance of the line. 

Tetrad Atom. — (See Appendix— Atom, 
Tetrad.) 

Theoretical Magnet. — (See Appendix — 
Magnet, Theoretical?) 

Theory, Contact, of Electricity A 

theory that ascribes the production of elec- 
tricity in a voltaic cell, and to some extent 



the production of electricity by friction, to the 
contact of dissimilar substances or surfaces. 

The act of contact is assumed to produce a 
difference of potential. While mere contact may 
unquestionably produce a difference of potential, 
it requires the liberation of the chemical potential 
energy of the metal of the positive plate of a 
voltaic couple to maintain such differences of 
potential as to produce a continuous' flow of a 
current. 

Therinancy, Electro A term pro- 
posed for that branch of electricity which 
treats of the effects produced by an electric 
current on the temperature of a thermo- 
electric junction . 

Thermo-Chemical Cell.— (See Appendix — 
Cell, Ther mo-Chemical^) 

Thermo Chemistry.— (See Appendix— 
Chemistry, Ther?no.) 

Thermo-Electric Generator. — (See Ap- 
pendix — Generator, Thermo-Electric.) 

Thermo-Electric Pair. — (See Appendix — 
Pair, Thermo-Electric?) 

Thermo-Electrometer.— (See Appendix — 
Electrometer, Thermo?) 

Thernio-Multiplier. — A thermopile. 

Thermo Pair.— (See Appendix — Pair, 
Thermo?) 

Thermo-Phone. — An electrical instrument 
for producing sounds by means of electrically 
produced heat. 

Thermostatic. — Of or pertaining to a 
thermostat. 

Thermo-Telephone. — (See Appendix — 
Telephone, Thermo.) 

Thermotic, Electro Of or pertain- 
ing to heat produced by electricity. 

Thimble Brush. — (See Appendix — Brush, 
Thimble.) 

Thomson. — A name proposed for the unit 
of conductivity. 

The term mho is to-day generally employed 
for the unit of conductivity. The plan of em- 
ploying the names of celebrated deceased elec- 
tricians is a good one and should not be departed 
from, no matter how deservedly great the name 
of the living electrician. 



Tho.] 



658 



[Tip. 



Thomson's Bridge. — (See Appendix — 
Bridge, Thomson' s.) 

Three-Phase Armature.— (See Appendix 
■ — Armature, Three-Phased) 

Three-Phase Currents. — (See Appendix— 
Currents, Three-Phased) 

Three-Phase Generator.— (See Appendix 
— Generator, Three-Phase) 

Three-Phase Motor. — (See Appendix — 
Motor, Three-Phase) 

Three-Way Switch. — (See Appendix — 
Switch, Three- Way) 

Three -Way Trolley Switch. — (See Appen- 
dix — Switch, Three- Way Trolley) 

Throw, Concentration — A term 

proposed by Squier for the deflection of a 
magnetic needle by a current produced under 
certain circumstances by a couple formed of 
similar plates of iron or other paramagnetic 
metals when exposed to chemical action while 
under the influence of a magnetic field. 

The concentration throw is a phenomenon mark- 
ing the reversal of the direction of current pro- 
duced by a couple of paramagnetic metals when 
exposed to the action of a magnetic field. Squier 
has observed in the case of a couple formed of 
similar plates of iron exposed to the action of 
nitric acid while in a magnetic field, that under 
certain conditions the effect of suddenly putting 
•on a magnetic field was to produce a less rapid 
deflection of the galvanometer in the opposite 
direction, so that the electrode which was formerly 
protected, by being the negative plate of the 
couple, was now the one acted on by becoming 
the positive plate. 

It is the above phenomenon for which Squier 
proposes the term of concentration throw. 

According to Squier, « ' The ' protective throw ' 
is due to the actual attraction of the magnet for 
the ion, and is always in the direction to protect 
the more strongly magnetized parts, while the 
■* concentrated throw ' is always in the opposite 
direction, and depends upon the distribution of 
the iron salts present in the solution, and the con- 
vection currents in the liquid. The concentration 
of the products of the reaction about the point, 
would tend to produce a ferrous reaction instead 
of a ferric reaction, and experiments show that a 



higher electromotive force is obtained with cells 
in which a ferrous reaction takes place than with 
those in which a ferric reaction occurs, and this 
change in the character of the reaction produced 
by the concentration probably accounts, at least 
in part, for the increased electromotive force at 
the point." 

Throw, Protective A term pro- 
posed for the protection afforded by a mag- 
netic field to paramagnetic metals exposed to 
chemical action. 

When two similar electrodes of iron, or other 
paramagnetic metals, are exposed to chemical 
action while under the influence of a strong mag- 
netic field, they act as a voltaic couple and the 
direction of the current produced depends on 
the direction of the lines of magnetic force. In 
the case of iron exposed to the action of nitric 
acid, one electrode being in the shape of a pointed 
cylinder and the other in the shape of a disc, 
when the lines of magnetic force of the field coin- 
cide in the direction with the length of the disc, 
the current produced passes through the liquid 
from the disc to the electrode, that is, from the 
less magnetized electrode, to the more magnet- 
ized electrode, the presence of the magnetic field 
determining the direction of the current pro- 
duced. In this, as in all similar cases of voltaic 
couples, the negative plate or electrode is pro- 
tected from the chemical action, the positive plate 
alone being acted on. 

The name protective throw is proposed by 
Squier for the protection so afforded, who has 
studied the phenomena. The proposed term 
would appear to be an unfortunate one, the pro- 
tection not being afforded by the throw of the 
needle. 

Tint-Electro.— A term proposed for a 
method of electric engraving. 

Tip, Conducting- Cord A blunted 

or rounded conductor placed at one of the 
ends of a wire for the purpose of readily in- 
serting it into a binding post or into a hole in 
a plate. 

Tip, Conducting Cord, Separable 

A cord and tip arranged so that the tip is 
readily detachable from the cord. 

The method of attachment can be insured in 
a variety of ways. A screw thread forms one of 
the most obvious. 



Ton.] 



659 



[Tra. 



Tonicity, Electro A term some- 
times employed for electrotonus. (See 
Electrotonus.) 

Tool, Electric Machine A machine 

tool of any character driven directly by elec- 
tric power. 

In electric machine tools the motor is generally 
so placed that the moving power is thus connected 
directly to the machine instead of transmitted to 
it by means of belting. Among the many advan- 
tages possessed by electric machine tools is that 
such tools do away entirely with lines of shafting. 

Top-Hat Curve. — (See Appendix — Curve, 
Top-Hat.) 
Torque, Running', of Motor The 

torque exerted by a motor while running. 



Torque, Starting", of Motor 



-The 



torque exerted by a motor at the moment of 
starting. 

The starting torque in a well-constructed motor, 
either of the alternating or continuous type, is 
always in excess of the torque it exerts at full load. 

Total Contact. — (See Appendix — Contact, 
Total.) 
Total Intensity of Earth's Magnetism. — 

(See Appendix — Magnetism, Total Intensity 
of Earth's) 

Touch, Divided A term sometimes 

employed in place of separate touch. (See 
Touch, Separate) 

Tourniquet, Electric A term some- 
times employed in place of electric flyer. (See 
Flyer, Electric) 

Transference, Convection — The 

transference of electricity in a liquid sub- 
stance unattended by chemical changes in the 
liquid. 

Convection transference of electricity appears to 
partake of the nature of atomic convection, the 
charge being carried by each atom or group of 
atoms in the direction in which the electricity is 
being transferred. 

Transform. — To change or convert. 

To convert or change the electromotive 
force and consequently simultaneously to 
change the current strength of the circuit by 
any means. 



Strictly speaking, a transformer is regarded as 
changing the electromotive force. It therefore 
produces at the same time changes in the value of 
the current strength. When we speak of a step- 
down transformer we refer to a transformer which 
lowers or decreases the value of the electromotive 
force, although, of course, at the same time, it 
is employed to raise or increase the strength of 
the current. 

Tranformation.— The act of transforming 
or changing. 

Transformation, as of Electromotive 

Force —A change in the value of the 

electromotive force by means of an induction 
coil or transformer. (See Transformer) 

Electric power is equal to the product of the 
current by the electromotive force. By the use 
of a transformer the electromotive force, and con- 
sequently the current strength, are changed or 
altered in value. Since in a well-constructed 
transformer but very little energy is lost in trans- 
formation, the product of C E, in the primary 
very nearly equals the product of C E', in the 
secondary. It follows, therefore, that as the elec- 
tromotive force increases in the secondary, the 
current strength decreases and vice versa. 

In the case of a transformer the transformation 
is directly proportional to the ratio of the number 
of turns of the primary and the secondary cir- 
cuits. 



Transformation, Current 



-The act 



of changing the value of the current in any 
circuit by changes effected in its electromotive 
force. (See Transformer) 

The act of changing the character of the cur- 
rent, such, for example, as a direct into an alternat- 
ing current or the reverse, or a single alternating 
current of short wave length and high frequency 
into triphase or polyphase currents. 

It will be observed that the term current trans- 
formation is employed in two distinct senses. 

Transformation of Electric Force. — (See 
Appendix — Force, Electric, Transfor?na- 
tion of) 

Transformation, Ratio of The ratio 

between the electromotive force produced in 
the secondary of an induction coil or trans- 
former and the electromotive force impressed 
on the primary. 



Tra.] 



660 



[Tra, 



The ratio of transformation depends on the rel- 
ative number of turns of the secondary and pri- 
mary coils of the transformer. In a well-con- 
structed transformer there is very little energy lost 
in producing a transformation by means of 
mutual induction. Consequently the energy pro- 
duced in the secondary must very nearly equal 
the energy, that has been expended in the 
primary. Suppose, for example, that the number 
of turns of the secondary of an induction coil is 
one-fiftieth that of the primary ; then the difference 
of potential induced in the secondary will be but 
one-fiftieth that impressed on the primary. In 
order to make the product of the current strength 
and the difference of potential in the secondary 
equal to the product of the current strength and 
difference of potential in the primary, the cur- 
rent strength in the secondary will have to be 
fifty times greater than the current strength in 
the primary; or, in other words, the product 
of C and E, in the primary will very nearly 
equal the product of C and E' in the secondary, 
i. e., C E = C E' nearly, assuming their lag 
factors to be equal. 

Transformer, Alternating-Current Ro- 

tary A term sometimes employed for 

an alternating current motor which at the 
same time, by means of a suitable commu- 
tator, delivers continuous currents on a sep- 
arate circuit. 

Transformer, Closed-Circuit A 

term sometimes employed for closed-iron- 
circuit transformer. (See Transformer, 
Closed Iron Circuit?) 

Transformer, Continuous Current 

— A term sometimes used for motor-dynamo 
or dynamotor. (See Transformer, Constant 
Current?) 

Transformer, Direct-Current Rotary 

— A term sometimes employed for a motor- 
generator. (See Generator, Motor.) 
Transformer, High-Frequency A 

transformer in which the frequency of the 
currents employed is high. 

Transformer, Iron-Loss in A loss 

of energy in a transformer due to magnetic 
hysteresis or molecular magnetic friction and 
to the setting up of eddy or Foucault currents 
in the iron. 



According to Steinmetz, there is no sensible 
magnetic viscosity in a transformer up to 204.5 
complete periods per second. If the eddy or 
Foucault currents are excluded, the hysteresis loss 
of a transformer can, up to 200 complete periods 
per second, be exactly predetermined by calcula- 
tions based on tests at slow cycles, magnetic 
viscosity being absent. 

Transformer, Low-Frequency — 

A transformer in which the frequency of the 
currents employed is low. 

Transformer, Non-Polar A term 

sometimes employed in place of closed-iron- 
circuit transformer. (See Transformer, 
Closed Iron Circuit) 

Transformer, Open-Circuit A term 

frequently employed for open-iron-circuit 
transformer. (See Transformer, Open Iron 
Circuit) 

A variety of open-circuit transformer is shown 
in Fig. 582. 




Fig. 58 2. Open-Circuited Transformer. 

Transformer, Polar A term some- 
times employed for open-circuit transformer. 
(See Appendix — Transformer, Open-Cir- 
cuit) 

Transformer, Rotary A term gen- 
erally employed for the combination of a 
motor and generator in one machine, i. e., 
one armature and one motor. 

Sometimes employed in place of a con- 
tinuous current transformer. (See Trans- 
former, Constant Current. 

The rotary transformer is employed either to 
transform continuous currents into continuous 
currents of different potential, in which case its 
armature contains two windings, the generator 



Tra.] 



661 



[Tri. 



winding and the motor winding, and the ratio of 
transformation is equal to the ratio of the turns 
of the two windings; or for converting alternate 
or polyphase currents into continuous currents, 
in which case if the maximum alternate current 
potential equals the continuous current potential, 
it generally contains one armature winding only, 
which is connected to the continuous current 
commutator, and at two, three or four equidistant 
points to collector rings. 

Such rotary transformers are used extensively 
in long-distance power transmission for convert- 
ing the alternating or polyphase currents into 
continuous currents for railway circuits, or for 
supplying alternating current circuits, or for elec- 
tric welding. 

The term rotary transformer should not be con- 
founded with rotary current transformer. (See 
Transformer, Rotary Current.) 

Transformer, Static A term some- 
times employed for an ordinary transformer 
as distinguished from a rotary transformer. 
(See Appendix — Transformer, Rotary) 

Transforming. — Converting or changing 
the electromotive force and consequently the 
current strength in any circuit. 

Transition Resistance.— (See Appendix— 
Resistance, Transition) 
Translating Telegraphic Station.— (See 

Appendix — Station, Translating Tele- 
graphic) 

Translation Lag. — (See Appendix— Lag, 
Translation.) 

Translation, Manual In telegra- 
phy, especially in sub-marine telegraphy, the 
translation of a message from one circuit 
directly to another by an operator, who trans- 
mits to the second circuit, direct from sig- 
nals received on the first, without writing 
down or transcribing the message. 

Transmitter, Automatic Telegraphic 

An apparatus employed in a system 

of automatic telegraphy for sending or trans- 
mitting the prepared messages. 

The message for automatic telegraphy is pre- 
pared by properly punching or perforating a slip 
or fillet of paper. This fillet is passed through 
a transmitter so as to transmit automatically. 



Transposition.— In telephony a reversal in 
the relative position of two parallel conductors. 

Transpositions are made in conducting wires 
in order to neutralize the electromotive forces 
produced by neighboring currents. 

Trap, Burglar Alarm A spring 

burglar-alarm contact held in an open posi- 
tion by the pull of a string against the action 
of a spring. 

The slightest disturbance of the spring 
draws the contact in one direction, and the 
destruction of the string permits the spring 
to draw it in the opposite direction, in 
either case insuring the closing of a circuit 
and the ringing of an alarm bell. 

Treated Coked Filament— (See Appen- 
dix — Filament, Treated Coked) 

Tree Insulator. — (See Appendix — Insu- 
lator, Tree.) 

Tregadyne. — A term proposed by Houston 
and Kennelly for a million million dynes, or 
a million megadynes, or io 12 dynes. 

Trega. — A prefix proposed by Houston 
and Kennelly for a million million or io 12 . 

Tregerg. — A term proposed by Houston 
and Kennelly for a million million ergs, or a 
million megergs, or io 12 ergs. 

Tregohm. — A term proposed by Houston 
and Kennelly for a million million ohms, or 
a million megohms, or io 12 ohms. 

Triad Atom. — (See Appendix — Atom, 
Triad) 

Trico. — A term proposed by Houston and 
Kennelly for the million millionth part, or 
io" 12 . 

Tricofarad. — A term proposed by Houston 
and Kennelly for the millionth part of a 
microfarad, or io~ 12 farad. 

Trigger, Door A device by means 

of which notice is given of the opening or 
closing of a door or window. 

Trigger, One- Way Door A door 

trigger which operates on the opening of the 
door only. 

Trigger, Two- Way Door A door 

trigger which operates both when the door is 
opened and when it is closed. 



Tri.] 



662 



[Upp. 



Trip, Door, Electric 



— A device for 
ringing a bell so as to announce the entrance 
of a customer. 

The bell is rung only when the door passes the 
trip, but does not ring when the door is opened, 
or when it is being closed. 

Tri-Phase Armature. — (See Appendix — 
Armature, Tri-Phase) 

Tri-Phase Current. — (See Appendix — 
Current, Tri-Phase) 

Tri-Phase Generator. — (See Appendix — 
Generator, Tri-Phase. ) 

Tri-Phase Motor.— See Appendix— Motor, 
Tri-Phase. ) 

Triphased Alternating" Currents. — (See 
Appendix — Currents, Triphased, Alternat- 
ing^ 

Turtle-Back Electro.— (See Appendix— 
Electro, Turtle-Back) 

Two-Phase Alternator.— (See Appendix— 
Alternator, Two-Phase) 

Two-Phase Armature. — (See Appendix — 
Armature, Two-Phase) 

Two-Phase Generator. — (See Appendix — 
Generator, Two-Phase.) 

Two-Phase Motor. — (See Appendix — Mo- 
tor, Two-Phase) 



Two-Pole Dynamo-Electric Machine. — 

(See Appendix — Machine, Dynamo-Electric, 
Two-Pole) 

Two-Thousand Candle-Power Arc, Defi- 
nition for (See Appendix — Arc, Two- 
Thousand Candle-Power, Proposed Defini- 
tion for) 

Two-Way Door Trigger. — (See Appendix 
— Trigger, Two- Way, Door) 

Triple-Pole Switch. 

Switch, Triple-Pole) 

Tri-Polar Indicator. 

Didicator, Tri-Polar) 



(See Appendix^ 



■(See Appendix- 



Trolley Base Frame. — (See Appendix — 
Frame, Trolley Base) 

Trough, Plating A term some- 
times employed in place of plating bath. 
(See Bath, Electro-Plating) 



Tube, Lightning 

(See Fulgurite) 



-A fulgurite. 



Tubular Current. — (See Appendix— Cur- 
rent, Tubular) 

Tuning of Electrical Circuit.— Altering 
the period of a circuit or varying the capacity 
or self-induction of the circuit so as to bring 
it into resonance with another circuit. 



Uni-Phase Armature Winding.— (See Ap- 
pendix— Winding, Uni-Phase Armature) 

Uni-Phase Motor.— (See Appendix— Mo- 
tor, Uni-Phase.) 

Unipolar Stimulation of Nerve. — (See 
Appendix— Stimulation, Unipolar, of a 
Nerve) 

Unit, C. G. S., of Volumetric Energy 

— (See Appendix— Energy, Volumetric, C. G 
S. Unit of) 



Unlighted Segment of Aurora.— (See 

Appendix — Segment, Unlighted, of Aurora) 

Unmarked Magnetic Pole.— (See Appen- 
dix — Pole, Magnetic, Unmarked) 

Unsymmetrical Polyphase Motor.— (See 
Appendix— J/0/0/% Polyphase, Unsynimet- 
rical) 

Upper Harmonics of Current.— (See 

Appendix — Current, Upper Harmonics of) 



Vac] 



663 



[ToL 



V. — A symbol used for volt or for volume. 
The defining equation is V = L X L X L. 
The same symbol is also employed for volt. 

v. — A symbol used for velocity. 

The defining equation is v= = 

The same letter is proposed as a symbol for volt. 
Its use should be limited to one or the other 
quantity. 

v. — A symbol for the ratio between th e 
units of resistance in the electrostatic and 
electromagnetic C. G. S. system of measure- 
ment ; i. e., for velocity ratio. (See Ratio, 
Velocity.) 

Vacuum-Tube Lighting 1 .— (See Appendix 
— Lighting, Vacuum- Tube.) 

Variable Period of Telegraph Line. — 

(See Appendix — Period, Variable, of Tele- 
g raph Line.) 

Variation Magnetometer. — (See Appen- 
dix — Magnetometer, Variatio?i) 

Vector Potential. — (See Appendix — Po- 
tential, Vector.) 

Verdet's Constant. — (See Appendix— Con- 
stant, Verdet's.) 

Vertical Intensity of Earth's Magnetism. 

— (See Appendix — Magnetism, Vertical In- 
tensity of Earth's) 

Vertical Magnetic Needle.— (See Appen- 
dix — Needle, Vertical Magnetic.) 

Vibration Frequency. — (See Appendix — 
Frequency, Vibration.) 

Vibrator. — An electromagnetic device pro- 
vided on a siphon recorder for maintaining 
the siphon in continual vibration so that ink 
is thrown down upon the fillet of paper be- 
neath. 

Virtual Current.— (See Appendix— Cur- 
rent, Virtual.) 

Visual Telegraphic Signal.— (See Appen- 
dix — Sig?ial, Telegraphic, Visual) 



Volatilization of Electric Conductor. — 

(See Appendix— Conductor, Electric, Vola- 
tilization of) 

Volt, International The value of 

the international volt adopted by the Chicago 
Congress of 1893 as equal to such an electro- 
motive force that, steadily applied to a con- 
ductor whose resistance is one international 
ohm, will produce a current of one interna- 
tional ampere, and which is represented suffi- 
ciently well for practical use by tM f of the 
electromotive force between the electrodes of 
the voltaic cell known as Clark's cell, at a 
temperature of 15 C, and prepared in ac- 
cordance with certain specifications. 

Volt, Proposed A. I. E. E. Definition for 
The product of the A. I. E. E. am- 
pere by the A. I. E. E. ohm. 

Volt-Ammeter. — A term proposed for any 
electric instrument capable of measuring 
either the volts or the amperes in a circuit, or 
both. 

A measurer of the volt-amperes or the 
watts. 

A wattmeter. 

The word wattmeter would appear to be pref- 
erable. 

Volta-Electric. — Of or pertaining to voltaic 
electricity. (See Electricity, Voltaic.) 

Volta-Electricity. — Voltaic electricity. 
(See Electricity, Voltaic.) 

Volta-Electrometer. — A voltameter. (See 
Voltameter) 

VoltaElectrometric. — Producing voltaic 
electricity. (See Electricity, Voltaic.) 

Volta-Electromotive Force.— (See Ap- 
pendix — Force, Volta-Electromotive) 

Volta-Plast.— A word proposed for the 
voltaic battery employed in electrotyping. 

The use of this wor'd would appear to be en- 
tirely unnecessary. There is nothing peculiar 
about this employment of the voltaic battery. 



Tol.] 



664 



[Vol, 



Volta-Type. — A word proposed for elec- 
trotype. 

The use of this word would appear to be en- 
tirely unnecessary. The word electrotype is pref- 
erable. 

Voltagraphy. — Electrotypy. 
The word electrotypy would appear to be far 
preferable. 

Yoltaic Battery, Element of — (See 

Appendix — Element of Voltaic Battery) 

Yoltaic Bow. — (See Appendix — Bow, Vol- 
taic?) 

Voltaic Cell, Callan (See Appen- 
dix — Cell, Voltaic, Callan) 

Yoltaic Cell, Maynooth (See Ap- 
pendix — Cell, Voltaic, Maynooth) 

Voltaic Electromotive Force.— (See Ap- 
pendix — Force, Electromotive, Voltaic) 

Voltaic Endosmose. — (See Appendix— 
Endosmose, Voltaic) 

Voltaic Heat Cell.— (See Appendix— Cell, 
Voltaic Heat) 

Voltaic Magnet. — (See Appendix— Mag- 
net, Voltaic) 

Voltaic Pair. — (See Appendix — Pair, 
Voltaic) 

Voltaism. — A word sometimes employed 
in electro-therapeutics for treatment by means 
of the voltaic current. 

The production of electricity by means of 
voltaic couples. 

The latter use of this word was the meaning 
given to it by Sturgeon in 1842, who denned it as 
follows: "The production of electricity by the 
association of metals and other organic bodies by 
the simple contact of inorganic bodies." 

Voltmeter, Electrometer A volt- 
meter in which the difference of potential to 
be measured charges insulated conductors, 
the electrostatic attractions and repulsions of 
which produce a deflection of a suitably sus- 
pended metallic needle. • 

A term frequently employed for voltam- 
eter. (See Electrometer. Volta?neter) 



Voltmeter, Galvanometer —Any 

form of galvanometer so arranged as to 
readily measure difference of potential. 

A term sometimes employed for a galva- 
nometer. 

Galvanometer-voltmeters may be constructed 
in a great variety of forms. 

In all such cases, however, the difference of 
potential is measured by the deflection of a needle 
of a galvanoi-ieter by means of the magnetic field 
produced by the current which flows through a 
conductor connecting the two points whose differ- 
ence of potential is to be measured. 

In any galvanometer-voltmeter a magnetic field 
produced, as above described, by the difference 
of potential which is to be measured, may deflect 
a magnetic needle against the following forces, 
namely: 

(1.) Against a magnetic field. (See Appendix 
— Voltmeter, Magnetic. ) 

(2.) Against the action of a spring. (See Ap- 
pend ix — Voltmeter, Spring. ) 

(3.) Against the action of gravity acting on a 
weight. (See Appendix — Voltmeter, Weight.) 



-An instru- 



Voltmeter, Magnetic — 

meat in which the magnetic field of a cur- 
rent, which is proportional to the difference 
of potential to be measured, deflects a mova- 
ble needle against the action of the field of 
a magnet. (See Voltmeter) 

Voltmeter, Spring" — An instrument 

in which the magnetic field of a current, 
which is proportional to the difference of po- 
tential to be measured, deflects a movable 
needle against the action of a spring. (See 
Voltmeter) 

Voltmeter, Weight An instrument 

in which the magnetic field of a current, which 
is proportional to the difference of potential 
to be measured, deflects a movable needle 
against the action of a weight. (See Volt- 
meter) 

Volume Density of Charge.— (See Appen- 
dix — Charge, Volwne Density of) 

Volumetric Energy. — (See Appendix — 
Energy, Volumetric.) 



Wan.] 



665 



[Wlii, 



w 



W. — A contraction used for the physical 
quantity energy , whether it be electrical, ther- 
mal, mechanical or chemical, or, in general, 
to represent the product of the force by the 
distance. 

W. — A symbol used for electric energy. 

The defining equation is W = C E T. 

The same letter is proposed as the symbol for 
work and moment of a couple. 

W. — A symbol proposed for the moment of 
a couple. 

This letter is also employed as the symbol for 
work. 

The defining equation is F X D. 

w. li. — An abbreviation proposed for watt- 
hour, the practical unit of electric energy. 

"Wand, Electric — A term some- 
times used for an electrophorus in the form 
of a torch. 

An electric wand is employed for gas lighting 
by a spark produced by means of a small static 
machine in the handle upon the electrophorus. 

Watchman's Electric Clock. — (See Appen- 
dix — Clock, Electric, Watchman's?) 

Water-Gramme Degree.— (See Appendix 
— Degree, Water-Gratmne.) 

Watt-Efficiency of Secondary Battery. — 
(See Appendix — Battery, Secondary, Watt- 
Efficiency of.) 

Watt, International The value of 

the international watt, adopted by the Chicago 
Congress of 1893, is equal to 10" units of 
power in the C. G. S. system, and which is 
the work done at the rate of one joule per 
second. 

Watt, Proposed A. I. E. E. Definition for 

The product of the square of the 

A. I. E. E. ampere and the A. I. E. E. ohm. 

Waves, Hertzian A term sometimes 

employed for electro-magnetic waves. 

Waves in the ether that are produced by oscil- 
latory discharges passing through a circuit or by 
a magnetic circuit undergoing variations in its 



magnetic intensity. (See Electricity, Hertz's 
Theory of Electro-Magnetic Radiation, or 
Waves.) 

Way Lease. — (See Appendix — Lease, 
Way.) 

Weber, A. I. E. E. Definition for 

A name proposed for the practical unit of 
magnetic flux, 

A unit of magnetic flux having the value of 
one absolute unit or line. 

This unit is a modification of that proposed by 
a Sub-Committee of the American Institute of 
Electrical Engineers on Provisional Programme 
for the International Electrical Congress held in 
Chicago, U. S. A., in 1893, on the occasion of the 
World's Columbian Exposition. 

The term weber was formerly applied to the 
unit of current; it never, however, came into 
very extensive use in the United States. 

Wedge Cnt-Out.— (See Appendix— Cut- 
Out, Wedge.) 

Weeding-Ont of Harmonics.— (See Ap- 
pendix — Harmonics, Weeding-Oitt of.) 

Weeding-Ont of Harmonics by Electrical 
Resonance. — (See Appendix — Harmonics, 
Weeding-Out of, by Electrical Resonance?) 

Weight Voltmeter. — (See Appendix — 
Volt7iieter, Weight?) 

Wheel, Barker's — A term some- 
times applied to a Barker revolving contact 
breaker. (See Appendix — Breaker, Contact, 
Barker s Revolving.) 

Whirl, Contracting Magnetic A 

magnetic whirl which is decreasing or mov- 
ing in towards the electro-magnet or circuit 
which is producing it. 

When variations occur in the strength of 
the magnetism produced by variations in the 
strength of the current, expanding or contracting 
whirls are produced around the conductor which 
move outwards or from the conductor when the 
strength of the magnetism is increasing, and in- 
wards or towards the conductor when such 
strength is decreasing. These whirls produce 



Whi.] 



666 



[Wir. 



electro-magnetic waves in the surrounding ether 
which are called Hertzian electro-magnetic 
waves. (See Whirl, Expanding Magnetic. 
Electricity y Hertz's Theory of.) 

Whirls, Electro-Dynamic A whirl- 
ing or rotary motion produced in a cloud of 
copper oxide in a voltameter when traversed 
by a powerful electric discharge while under 
the influence of a magnetic field. 

The direction of the rotation is opposite to the 
hands of a watch before a north magnetic pole 
and in the same direction as the hands of a watch 
before a south pole. 

Winding, Differential A — ny double 

winding of the magnet coils such that the 
two fields produced thereby are opposed to 
each other. 

Winding, Single-Phase Armature 

— A uni-phase armature winding. — (See Ap- 
pendix — Winding, Uni-Phase Armature?) 

Winding, Uni-Phase Armature 

The winding of the armature of a motor such 
as to enable it to be operated by uni-phase 
currents. 

Windings, Phase —The separate 

windings on the armature of a polyphase 
motor. (See Appendix — Motor, Polyphase?) 

Windmill, Electric A term some- 
times employed in place of electric flyer. 
(See Flyer, Electric?) 

Window or Blind Contact. — (See Appen- 
dix — Contact, Window or Blind?) 

Wire, Annunciator Insulated wire 

suitable for use in connection with annuncia- 
tors, or other similar purposes. 

Wire, Double Bronze A conduct- 
ing wire furnished with an aluminium-bronze 
core and a copper-brass envelope. 

A double bronze wire possesses great tensile 
strength, extreme toughness, and a comparatively 
low electrical resistance. 

A No. n standard gauge double bronze wire 
has a breaking strain of 850 pounds and a re- 
sistance of 443 ohms per mile at 60 degrees Fahr. 

Such a wire is so tough that it will stand from 
eight to ten bends of 180 degrees each in alter- 
nate directions through a radius of 5 millimetres. 



Wire, Idle, of Armature A term 

sometimes employed in place of dead wire. 
(See Wire, Dead, of Armature?) 

Wire, Idle, of Armature of Dynamo 

■. — A term applied to that part of the wire on 
the armature of a dynamo-electric machine 
in which no useful electromotive force is pro- 
duced. 

The dead wire on an armature. (See Wire, 
Dead, of Armature?) 

Wire, Idle, of Armature of Motor 

—A term applied to that part of the wire on 
the armature of a motor in which the field pro- 
duced by the driving current never exercises 
useful action in driving the motor, in so far as 
no counter electromotive force is generated 
in it. 

Wire or Conductor, Balancing A 

term sometimes employed for a neutral wire 
or conductor of a three-wire system. 

Wire, Tap, in Quadruplex Telegraphy 

The intermediate wire or conductor, 

in a system of quadruplex telegraphy, which 
divides the battery into two unequal parts, 
called respectively the long end and the short 
end. 

Wires, Equalizing Two wires or 

conductors, one of which is employed for 
connecting the two positive brushes and the 
other for connecting the two negative brushes 
of two compounded dynamos when coupled in 
parallel. 

In general, wires or conductors employed for 
equalizing electrical pressure or difference of 
potential in two or more circuits. 

In the coupling of two compound-wound 
dynamos, the equalizing wires are connected one 
to the two positive brushes and the other to the 
two negative brushes of the coupled machines. 
By these means the electrical pressure or differ- 
ence of potential at the terminals of the two dyna- 
mos is made equal, and consequently the currents 
in the two fields are also made equal. 

Wires, Slinging A term sometimes 

employed in electro-plating for the wires or 
conductors by which the articles that are to 
be electro-plated are hung from the kathode 
in the plating bath. 



WirJ 



667 



[Zon. 



— Wiring by 
(See Appendix 



Wiring, Concentric — 

means of concentric cables. 
— Cable, Concentric.) 

Working 1 Current of Motor. — (See Ap- 
pendix — Current, Working, of Motor.) 

Working, Direct, of Telegraphic Sounder 

A term sometimes employed for the 

method in which a telegraphic sounder is 
operated by means of the current received 
from the line wire or conductor from the dis- 
tant station in contradistinction to the method 
where the receiving instrument is operated by 
means of a local battery. 

Working, Double-Current Telegraphic 

A term sometimes employed for 

double-current signaling. (See Signaling, 
Double-Current!) 



Working Efficiency of Telegraphic Cir- 
cuit. — (See Appendix - Circuit, Telegraphic,. 
Working Efficiency of.) 

Working, Polyphase A general 

term employed to express the actual applica- 
tion of polyphase currents. 

In polyphase currents the armature of the 
motor is provided with separate sets of coils 
grouped in two's, three's, etc., and put success- 
ively into action at suitable periods. 

Working, Single-Current Telegraphic 

A term sometimes employed for 

single-current signaling. (See Signaling, 
Single-Current!) 

Writing Telegraph.— (See Appendix — 
Telegraphy, Writing!) 



Y Tri-Phase System.— (See Appendix — 
System, Y Tri-Phase.) 
Yards, Ampere The product of the 



current in amperes by the distance in yards 
through which it passes. (See Feet, Ampere t 
Turn, Ampere!) 



Zero, Immediate False A term 

employed in Wheatstone bridge measure- 
ments for an observation made to that posi- 
tion of the galvanometer needle as zero, which 
is assumed, or which tends to be assumed, 
immediately after the opening of the circuit 
of the testing current. 

Zinc-Lead Accumulator. — (See Appendix 
— Accumulator, Zinc-Lead.) 



Zone, Neutral, of Electrically Charged/ 

Insulated Conductor That portion 

of an insulated conductor, charged by elec- 
trostatic induction, which lies approximately 
midway between its positive and negative 
ends. 

Zone, Neutral, of Magnet A term 

sometimes employed for equator of magnet,. 
(See Magnet, Equator of!) 



APPENDIX B. 



A. — A symbol for ampere (Partly Interna- 
tional usage). 

A. or An. — A contraction for anode. 

a. — A symbol proposed for acceleration. 

a. — A symbol for an angle. 

A. B. C. Telegraph Instrument.— 
A step-by-step dial telegraph instrument 
marked with the letters of the alphabet. 

A. C. — A contraction for alternating cur- 
rent. 

A. C. C. — A contraction for anodic closure 
contraction . 

A. D. C. — A contraction for anodic dura- 
tion contraction. 

A. H. — A contraction for ampere-hour. 

A. H. E. — A contraction for ampere-hour 
efficiency. 

A. O. C. — A contraction for anodic opening 
contraction. 

A. T. — A contraction for ampere-turn. 

A. W. G. — A contraction for American 
wire gauge. 

Abnormal Dispersion. — Anomalous dis- 
persion. 

Abnormal Earth-Current.— A tempo- 
rary, stronger, and more variable earth 
current than usual. 

Abnormal Magnetization. — Magnetiza- 
tion generally in concentric layers of al- 
ternate polarity, produced by oscillatory 
or Leyden-jar discharges. (Obsolete.) 

Abnormal Vapor - Densities. — Vapor 
densities whose values do not appear to 
conform to Avogadro's hypothesis. 

Abreast. — Connected in multiple or paral- 
lel. 

Abscissa. — The co-ordinate of a point 
measured along the axis of abscissas. 

Absolute.— (1) Complete in itself. (2) Not 
dependent on secondary bases. 

Absolute Block System for Railroads. 
A block system in which one train only 
is^ permitted to occupy a given block, or 
division of the road, at any one time. 



669 



Absolute Calibration.— The determina- 
tion of the absolute reading of an electro- 
meter, galvanometer, voltmeter, am- 
meter, or other instrument. 

Absolute Electro-Dynamometer.— An 

electro-dynamometer for the measurement 
of electric currents in C. G. S. units by 
reference to the moment of a bifilar 
suspension and constants derived from 
the winding of the coils. 
Absolute Electrometer.— An electrome- 
ter in which the value of the electromo- 
tive force is directly determined in abso- 
lute units from the deflection of its mov- 
able index. 

Absolute Expansion.— The real expan- 
sion of a liquid, or the expansion it would 
have independently of any change in the 
dimensions of its containing vessel. 

Absolute Galvanometer.— Any galvano- 
meter whose indications are directly de- 
termined in absolute units of current. 

Absolute Inductivity.— The real indue 
tivity of a medium as distinguished from 
the ratio of its inductivity to the induc- 
tivity of vacuum. 

Absolute Insulation.— The total insula- 
tion of a circuit or conductor without 
reference to its length. 

Absolute Permittivity.— The real per- 
mittivity of a medium as distinguished 
from the ratio of its permittivity to the 
permittivity of vacuum. 

Absolute Photometric Standard.— A 
term for a fundamental standard of light 
employed in photometric measurements, 
in contra-distinction to a secondaiy 
standard. 

Absolute Unit of Current.— (1) A cur- 
rent of such a strength that when passed 
through a wire one centimetre in length, 
bent in the form of an arc of a circle one 
centimetre in radius, will act with a force 
of a dyne on a magnetic pole of unit 
strength placed at the centre of the arc. 
(2) A current of 10 amperes. 



Abs.] 



670 



LACl. 



Absolute Unit of Electromotive 
Force.— (1) The C. G. S. unit of electro- 
motive force. (2) The one-hundred mil- 
lionth of a volt. 

Absolute Unit of Inductance.— A 
length equal to one centimetre. (2) The 
one billionth (10 9 ) part of a henry. 

Absolute Unit of Induction.— A term 
sometimes used for the absolute unit of 
inductance. 

Absolute Unit of Magnetomotive 
Force. — A unit of magnetomotive force 
equal to 47r multiplied by unit current 
of one turn. 

Absolute Unit of Resistance.— (1) The 
one thousand millionth of an ohm. (2) A 
micjohm. 

Absolute Units. — The centimetre- 
gramme-second system of units. 

Absolute Vacuum.— (1) A space from 
which all traces of residual gas have been 
removed. (2) A term sometimes loosely 
applied to a high vacuum. 

Absolute Zero of Temperature.— 

(1) The temperature of a substance in 
which its molecules are absolutely at rest, 
or possess no kinetic energy. (2) A tem- 
perature of approximately — 273°C. 
Absorption. — The taking in or drinking 
in of one form of matter by another, such 
as a gas, a vapor, or a liquid by any sub- 
stance, usually a solid ; or of energy of 
sound, light, heat or electricity by ordi- 
nary matter. 

Absorption Current.— The current of 
diminishing strength which flows into 
a dielectric under electrification, and 
which is partly capable of being restored 
during continued discharge. 

Absorption Dynamometer.— The name 
given to a dynamometer in which me- 
chanical power is measured and at the 
same time absorbed, in contradistinction 
to a transmission dynamometer, in which 
the power to be measured is all or nearly 
all transmitted. 

Absorption, Electric— The apparent 
soaking of an electric charge into the 
glass or other solid dielectric of a Leyden 
jar or condenser. 

Absorption of Sound.— Acoustic absorp- 
tion, 

Absorption Spectrum.— A spectrum 
containing gaps or dark spaces due to ab- 
sorption by some medium which the radi- 
ation has traversed. 

Absorptive. — Possessing the power of ab- 
sorption. 

Absorptive Power. — The power possessed 



by certain substances of taking in and 
condensing gases within their pores. 
Acceleration. — (1) The time-rate of change 
of velocity. (2) Increase or decrease of 
velocity. 

Accumulated Electricity.— Stored elec- 
tricity, as in a condenser. 

Accumulating Electricity. — S t o r i n g 
electricity. 

Accumulation of Electricity.— (1) The 
collection of an electric charge in a Ley- 
den jar or condenser. (2) The increase in 
an electric charge by devices called ac- 
cumulators. (3) The production of a 
charge by an influence machine. (4) The 
collection of electric energy by storage 
batteries or accumulators. 

Accumulator.— (1) A word sometimes ap- 
plied to a current accumulator. (2) A 
Leyden jar or condenser. (3) A secondary 
or storage battery: 

Accumulator Distribution.— Distribu- 
tion of electric energy by means of ac- 
cumulators. 

Accumulator Traction. — Car traction in 
which the motors are driven by storage 
batteries carried on the car. 

Acetometer.— (1) A hydrometer gradua- 
ted for determining the strength of com- 
mercial acetic acid or vinegar. (2) An 
acidometer. 

Acheson Effect.— The change in the elec- 
tromotive force of the secondary of a trans- 
former due to changes of temperature in 
its core. 

Achromatic. — Free from false coloration. 

Achromatic Lens.— A lens capable of 
forming images free from false coloration. 

Achromatic Ocular.— An achromatic 
eye-piece. 

Achromatisable. — Capable of being freed 
from false coloration. 

Achromatise. — To free from false colora- 
tion. 

Aehromatising. — Freeing from false 
coloration. 

Acidimeter. — An acidometer. 

Acidometer, — A hydrometer for measur- 
ing the specific gravity of an acid liquid, 
and thereby determining its degree of 
acidity. 

Aclinic. — (1) Of or pertaining to no mag- 
netic inclination. (2) Devoid of magnetic 
inclination or dip. 

Aclinic Line.— (1) A line connecting 
places on the earth's surface which have 
no magnetic inclination. (2) The mag- 
netic equator of the earth. 



Aco.] 



671 



[Act, 



Acoustic— Of or pertaining to sound. 

Acoustic Absorption.— The absorption 
by a vibrating body, of the energy of the 
sound waves produced by another vibrat- 
ing body. 

Acoustic Interference.— Interference of 
sound waves. 

Acoustic Resonance.— (1) The increase 
in the intensity of the sound emitted by 
a sonorous body by means of sympathetic 
vibrations set up in a co-periodic sounding 
body. (2) The condition by virtue of 
which a sonorous body is capable of having 
sympathetic vibrations produced in it by 
a' neighboring sounding body. 

Acoustic Synchronizer.— An instrument 
for indicating the synchronism of two 
alternating currents or alternators, by an 
acoustic apparatus in which silence is 
produced at synchronism. 

Acoustic Telegraph. — Any telegraph 
whose signals are appreciated by the ear, 
as distinguished from a visual telegraph. 

Acoustic Telegraphy.— Sound tele- 
graphy : or, any system of telegraplry in 
which the signals are received by sound, 
in contradistinction to being received 
visually. 

Acoustic Tetanus.— Tetanus produced by 
alternating currents from an induction 
coil, when its contact piece is vibrating 
with sufficient rapidity to produce a musi- 
cal note. 

Acoutemeter, Electric. — An apparatus 
for electrically testing the delicacy of 
hearing. 

Actinic. — Of or pertaining to the chemical 
effect produced by light or other form of 
radiant energy. 

Actinic Photometer. — A photometer in 
which the intensity of light is measured 
by the amount of chemical decomposition 
it produces. 

Actinic Ray.— A ray of light, or other 
form of radiant energy, possessing the 
power of producing chemical action. 

Actinism. — The chemical effects of light. 

Actino-Electricity. — Electricity pro- 
duced in crystalline substances by the 
action of radiant energy. 

Actinograph. — An apparatus for measur- 
ing and recording the intensity of the 
chemical effects of light. 

Actinography. — The method of produc- 
ing records by the chemical effects of 
light: 

Actinometer. — (1) An apparatus for meas- 
uring the intensity of the chemical effects 
of light. (2) A pyrheliometer. 



Actinometer, Electric. — An apparatus 
for electrically measuring the intensity of 
the chemically active rays present in any 
radiation. 

Actinometry. — The science of measuring 
the intensity of the chemical effects of 
radiant energy. 

Action Currents.— Physiological currents 
produced in a muscle or nerve during its 
activity. 

Active Coil or Conductor.— A coil or 
conductor carrying an electric current. 

Active Component of Exciting Cur- 
rent. (1) The active current in an alter- 
nating-current circuit as distinguished 
from the wattless current. (2) In an 
alternating-current circuit the component 
of current which is in phase with the E. 
M. F. (3) In an alternating-current cir- 
cuit the product of the E. M. F. and the 
effective or apparent conductance. 

Active Current.— (1) The working com- 
ponent of a current in an alternating-cur- 
rent circuit as distinguished from the wat- 
tless component of current. (2) The com- 
ponent of an alternating-electric current 
that is in phase with the impressed electro- 
motive force. 

Active Electromotive Force.— In an al- 
ternating-current circuit that component 
of the impressed electromotive force 
which is expended in overcoming the 
ohmic resistance, as distinguished from 
the component which is expended in over- 
coming the induced C. E. M. F. 

Active Loop. — Any single loop in a circuit 
that is traversed by an electric current. 

Active Mass. — In electrolysis the quantity 
of an electrolyte which is disassociated 
into its ions, and which is, therefore, 
active in conveying the electrolysing cur- 
rent. 

Active Material of Storage Cell.— The 
substance or substances in a storage or 
secondary cell, that undergo decompo- 
sition while charging or discharging, and 
which serve to store the electric en- 
ergy. 

Active Molecules. — (1) Those molecules 
in an electrolyte that, during the passage 
of an electric current, are resolved into 
their constituent ions and which, there- 
fore, alone affect the molecular conduc- 
tivity of the electrolyte. (2) The dis- 
associated molecules in an electrolyte. 

Active Plate of Voltaic Cell. — A name 
sometimes given to the zinc or other plate 
of a voltaic or primary cell which is dis- 
solved during action. 

Active Polar Surface of Magnet.— That 



Act.] 



672 



TAdy. 



surface of a magnet from which the use- 
ful flux emerges, or into which it enters. 

Active Pressure.— In an alternating-cur- 
rent circuit that component of the im- 
pressed pressure which is expended in 
overcoming the ohmic resistance. 

Active Pressure — A term sometimes em- 
ployed for the pressure that is effective 
in producing a current, as distinguished 
from the impressed pressure. 

Active Wire. — That portion of the wire 
on the armature of a dynamo or motor 
that is passed through the inducing mag- 
netic flux as distinguished from the re- 
mainder of the wire sometimes called 
" idle wire," which does not pass through 
such flux. 

Activity. — (1) Power. (2) Rate-of-doing- 
work. (3) The work done per second, in 
uniform working. 

Actual Cautery. — A cautery produced by 
the agency of a white heat. 

Actual Energy.— (1) Energy actually 
employed in doing w T ork, as distinguished 
from energy that, though possessing the 
power of doing work, is in the latent or 
potential state. (2) Kinetic energy. 

Actual Efficiency. — Commercial effici- 
ency. 

Acute Angle. — Any angle less than a right 
angle or 90 degrees. 

Acute- Angled Trolley-Crossing.— A 
contact plate suspended at the point of in- 
tersection of two trolley wires crossing 
at an acute angle. 

Acyclic Region. — (1) A region devoid of 
cyclosis. (2) A simply connected region. 

Adapter. — (1) A screw-nozzle fitted to an 
incandescent electric lamp and provided 
with a screw-thread to enable it to be 
readily placed on a gas bracket, or chan- 
delier, in the place of an ordinary gas 
burner. (2) A device which permits in- 
candescent electric lamps of one manufac- 
ture to be readily placed in the socket of 
a lamp of another manufacture. (3) Ap- 
paratus designed to permit the ready use 
of a continuous-electric current employed 
for incandescent lighting to produce the 
feeble continuous currents employed in 
electro-therapeutic work. 

Adherence.— The quality or property of 
adhesion. 

Adhesion. — The mutual attraction which 
exists between unlike molecules, as dis- 
tinguished from the attraction of like 
molecules, or cohesion. 

Adhesion, Electric. — The adhesion be- 
tween surfaces due to the attraction of 
unlike electrostatic charges. 



Adhesion, Magnetic— The adhesion be- 
tween surfaces due to magnetic flux. 

Adhesive Tape.— A tape covered with in- 
sulating material and possessing adhesive 
properties, employed for covering bared 
conductors, at joints, or other similar 
places. 

Adiabatic Expansion.— The expansion of 
a gas which neither receives nor gives out 
heat to the walls of the chamber in which 
the expansion takes place, as distin- 
guished from isothermal expansion. 

A diathermancy.— Opacity to heat. 

Adiathermanic. — Of or pertaining to- 
adiathermancy. 

Adieiectric. — (1) Not dilectric. (2) A term 
proposed for substances, not dielectrics, 
whose electric conductivity at ordinary 
temperatures decreases as the temperature 
increases. 

Adjustable Angle Crossing.— A form of 
trolley crossing in which the angle of in- 
tersection is adjustable. 

Adjustable Condenser.— A condenser 
whose capacity can be readily varied 
within certain limits. 

Adjustable Resistance. — A resistance 
whose value can be readily varied within 
certain limits. 

Adjustable Rheostat. — An adjustable re- 
sistance. 

Adjustable Vacuum Tube.— A vacuum 
tube employed for X-ray w r ork wmose 
vacuum can be decreased by the action 
of heat on a vaporizable substance. 

Adjustable Wire Clip for Trolley 
Wire. — A clip, capable of adjustment as 
to its position, inserted in an insulator 
and designed for holding a trolley wire in 
place. 

Adjuster for Lamp Pendant.— Any de- 
vice for adjusting or altering the height 
or position of a pendant lamp. 

Adjusting Cleat. — Any cleat that is ca- 
pable of adjustment as to alignment or 
height. 

Adjustment. — Any regulation of an ap- 
paratus that will enable it properly to 
perform its functions. 

Adjustment of Relay. — Such a regula- 
tion of a receiving relay as will permit it 
to readily respond to signals sent over the 
line. 

Admittance.— (1) The reciprocal of the 
impedance in an alternating-current cir- 
cuit. (2) The apparent conductance of 
an alternating-current circuit or con- 
ductor. 

Advanced Quadrature. — In an alternate 



Ady.] 



673 



[Air. 



ing-current circuit the condition of being 
90° in phase ahead of some particular 
E. M. F., flux, or current. 

Adynamic System of Currents.— A sys- 
tem of currents so opposed to each other 
in direction as to neutralize one another's 
magnetic effects. 

Aeolotropic. — Heterogeneous with re- 
spect to direction. 

Aeolotropic Medium. — (1) A medium 
possessing different properties in different 
directions. (2) A medium in which equal 
stresses applied in any direction do not 
produce equal strains. 

JEpinus' Condenser.— An early form of 
air condenser. 

Aerial Cable. — An electric cable sus- 
pended in the air. 

Aerial Circuit. — (1) That portion of a cir- 
cuit which consists of aerial conductors 
or lines. (2) A circuit of overhead wire. 

Aerial Conductor. — An overhead con- 
ductor. 

Aerial Line. — An overhead line. 

Aerial Telephone Cable.— A suitably 
supported overhead telephone cable. 

Aerodromic Transportation. — Trans- 
portation bj r means of a balloon -supported 
car over a suitable support guide. 

Aerodynamics. — The science whicli treats 
of the forces produced by air in motion. 

Aero-Ferric-Circuit Transformer.— An 
open-circuit transformer. 

Aero-Ferric Inductance. — The induct- 
ance possessed by a coil or coils whose 
magnetic circuit consists partly of air and 
partly of iron. 

Aero-Ferric Magnetic Circuit. — A 
magnetic circuit that is completed partly 
through air and partly through iron. 

Aerolite. — A meteorite. 

Aero-Therapeutics. — Treatment of dis- 
ease by means of air under pressures other 
than that of the atmosphere. 

After Currents. — Electric currents pro- 
duced in nerve or in muscular tissue, on 
the cessation of a constant current which 
has been flowing through it. 

After Glow of Exhausted Bulb. — A 
fluorescent glow, observed in an ex- 
hausted glass chamber, after its with- 
drawal from electrostatic influence. 

Age-Coating of Electric Incandescent 
Lamp Chamber. — A. blackening of the 
chamber of an electric incandescent lamp 
due to the deposit thereon, during use, of 
carbon, or other opaque substance. 

Ageing of Alcohol, Electric— Artifi- 
43 



cially ageing alcohol by exposing it to the 
action of electrically generated ozone. 

Ageing of Electric Incandescent 
Lamp. — A gradual decrease in the effi- 
ciency of an electric incandescent lamp 
due either to the age coating of its cham- 
ber, or to the deterioration of its filament. 

Ageing of Magnet.— Treating a perma- 
nent magnet for the purpose of rendering 
its magnetic condition more permanent. 

Ageing of Transformer.— (1) A decrease 
in the efficiency of a transformer owing 
to the ageing of its core. (2) Fatigue of 
transformer. 

Ageing of Transformer Core.— Increase 
in the hysteretic coefficient in the iron 
of a transformer core, during the first few 
months of its commercial operation, from 
its continued magnetic reversals at com- 
paratively high temperature. 

Agglomerate Leclanche' Cell.— A form 
of Leclanche cell which dispenses with 
the porous cup by employing the carbon 
and black oxide of manganese formed 
into a solid mass by pressure. 

Agitator for Plating Vat.— A device for 
ensuring a uniformity in the density of 
the plating solution in a depositing vat, 
by mechanical stirring. 

Agonal. — Of or pertaining to an agone. 

Agone. — (1) A line connecting places on 
the earth's surface where the magnetic 
needle points to the true geographical 
north. (2) The line of no declination. 

Agonic. — Of or pertaining to an agone. 

Agonic Line.— (1) A line connecting ter- 
restrial points having no declination or 
variation. (2) The agone. 

Air Battery.— A form of voltaic battery 
whose electromotive force is increased by 
the direct absorption of oxygen from the 
air. 

Air Blast for Commutator.— A jet of air 

applied to the surface of the commutator 
of a dynamo-electric machine to prevent 
destructive flashing. 

Air-Blast Transformer. — A transformer 
which is cooled by a blast of air. 

Air Churning.— The movement of the air 
that occurs in the vicinity of the arma- 
ture of a dynamo or motor during rotation 
resulting in "a loss of energy to the machine. 

Air Condenser.— A condenser in which 
air is the dielectric. 

Air-Cooled Transformer.— (1) A trans- 
former which is cooled by the passage 
through it of convection currents of air 
set up by its increase of temperature. 
(2) An air-blast transformer. 



Air.] 



674 



[All. 



Air-Core Solenoid.— A solenoid which 
has no core other than air. 

Air-Core Transformer.— A transformer 
which is destitute of a core other than 
that of air. 

Air-Expansion Lightning Arrester.— 
A form of lightning arrester in which the 
arc, when formed, is blown out by the 
expansion of a mass of confined air under 
the influence of the heat of the arc. 

Air Field. — That portion of a magnetic 
field in which the magnetic flux passes 
through air only. 

Air Film of Lamp Chamber.— A film of 
condensed air that tends to remain on the 
walls of an exhausted lamp chamber after 
the action of the air pump. 

Air Gap. — In a magnetic circuit, any gap 
or opening containing air only. 

Air Gap of Commutator.— The air space 
between contiguous segments in an air- 
insulated commutator. 

Air Insulation. — An insulation obtained 
by air, or by the action of air. 

Air Ley den. — An air condenser. 

Air-Line Wire. — That portion of a circuit 
which consists of overhead wires, in con- 
tradistinction to the portion which passes 
through underground conduits, or 
through a submarine cable. 

Air Magnetic Circuit. — A magnetic 
circuit in which the flux passes wholly 
through air. 

Air Path. — The path a disruptive discharge 
takes through the air. 

Air Pump. — A device for removing air or 
other gas from a containing vessel. 

Air Reluctance. — The reluctance of that 
portion of a magnetic circuit which con- 
sists of air. 

Air Resistance of Dynamo.— The me- 
chanical resistance to the rotation of a 
dynamo due to the surrounding air. 

Air Space. — (1) The space that exists, be- 
tween the surface of an armature and the 
polar surface within which it rotates. 
(2) The space between opposed surfaces 
of a comb lightning-arrester. 

Air-Space Cut-Out. — A modified form of 
paper cut-out in which the disc of paper 
or mica is replaced by an air-space. 

Air-Space Submarine Cable.— A mul- 
tiple-conductor submarine cable, having 
a core in which an internal air space is 
provided for separating the conductors. 

Air Telegraphy.— (1) Aerial telegraphy. 
(2) Induction telegraphy. (3) Wireless tel- 
egraphy. 



Air-Washing of Lamp Filament.— A 

deleterious effect produced on the fila- 
ment of an incandescent electric lamp by 
the molecular bombardment of the resid- 
ual gaseous atmosphere of its chamber. 

Alarm, Electric— (1) Any automatic elec- 
tric device by which attention is called 
to the occurrence of certain events, such 
as the opening of a door or window, the 
stepping of a person on a mat or stair- 
case, the rise or fall of temperature be- 
yond a certain predetermined point, etc., 
by the closing or opening of an electric 
circuit. (2) A device for calling a person 
to a telegraphic or telephonic instru- 
ment. 

Alarm Point.— In a system of fire teleg- 
raphy, any point from which an alarm 
is sent out. 

Alarm Wires of Submarine Cable.— 
Extra insulated wires imbedded in the 
fibrous serving of a submarine cable, be- 
tween the sheathing wires and the con- 
ductor core, and capable of giving an 
alarm when their insulation is affected 
through injury to the cable, before the 
working conductor or central core may 
be injured. 

Aligned Magnetomotive Force.— The 
magnetomotive force in a magnetic cir- 
cuit containing iron, due to the aligning 
of the molecular magnets of the iron 
under the influence of the impressed 
magnetic force or prime flux. 

"Alive." — (1) A name sometimes given 
to a live wire or circuit. (2) An active 
wire or circuit. 

All-Day Efficiency of Transformer.— 

The ratio of the energy commercially 
supplied by a transformer in 24 hours to 
the energy absorbed by it from the mains 
during that time. 

All-Night Arc Lamp.— A double-carbon 
arc lamp. 

Allotropic. — Of or pertaining to allo- 
tropism. 

Allotropic State. — A modification of a 
substance by means of which, without 
any change in chemical composition, it 
acquires physical or chemical properties 
differing from those it ordinarily pos- 
sesses. 

Allotropism. — The state or condition re- 
sulting from acquiring the allotropic 
state. 

Allotropy. — The property of, or capacity 
for, acquiring the allotropic state. 

Alloy. — A combination or homogeneous 
mixture of two or more metallic sub- 
stances. 



All]. 



675 



[Alt. 



Alloy. — To form a combination or homo- 
geneous mixture of two or more metallic 
substances. 

Alphabetic Telegraph.— (1) A telegraph 
in which the letters of the message to be 
sent are spelled out in succession from a 
dial. (2) An A, B, C, telegraph. 

Alteration Theory of Muscular or 
Nerve Currents. — A theory which 
traces the origin of electric currents in 
the nerves or muscular fibres to an alter- 
ation from their original condition. 

Alternate Currents. — Alternating cur- 
rents. 

Alternating. — Periodically changing in 
direction. 

Alternating Arc— (1) An alternating-cur- 
rent arc. (2) An arc supplied from an 
alternating-current circuit. 

Alternating Continuous-Current Corn- 
mutating Machine. — A secondary gen- 
erator for transforming from alternating 
to continuous currents by the aid of a 
commutator. 

Alternating-Current Arc— A voltaic arc 
produced by alternating electric currents. 

Alternating-Current Armature-Wind- 
ing. — A.n armature winding suitable for 
the production of alternating currents. 

Alternating - Current Dynamo - Elec- 
tric Machine. — A dynamo-electric ma- 
chine producing alternating currents in 
its external circuit. 

Alternating-Current Electric Motor. 
— A motor driven by alternating electric 
currents. 

Alternating-Current Electro-Magnet. 
— An electro-magnet whose coils are 
traversed by alternating currents, and 
which, although constantly reversing in 
magnetism, yet possesses a continued at- 
traction for its armature. 

Alternating - Current Phase - Meter.— 
An apparatus for measuring the differ- 
ence between the phases of two alternat- 
ing currents. 

Alternating - Current Potentiometer. 

— A potentiometer suitable for measuring 
the difference of pressure in an alternat- 
ing-current circuit. 

Alternating-Current Power.— (1) Elec- 
tric power supplied through the medium 
of alternating currents. (2) The product 
of the effective alternating-current 
strength, the effective pressure under 
which that current is supplied, and the 
power factor. (3) With sinusoidal elec- 
tromotive forces and currents, the pro- 
duct of the effective current strength, 



the effective pressure under which that 
current is supplied, and the cosine of the 
phase-difference between the two. 
Alternating-Current Pressure Indi- 
cator. - - An alternating - current volt- 
meter. 

Alternating-Current Regulator.— (1) A 
regulator for maintaining- constant the 
pressure of an alternating-current gen- 
erator. (2) A regulator for controlling 
the strength of an alternating current. 

Alternating-Current Rotary Trans- 
former. — A rotary transformer for 
transforming alternating into continu- 
ous-currents, or vice-versa. 

Alternating-Current Transmission.— 
Transmission of power or energy by 
means of alternating currents. 

Alternating-Current Rush. — (1) A term 
sometimes applied to the first rush or 
wave of alternating current passing into 
the primary coil of a transformer at the 
moment it is connected to the mains. (2) 
A term sometimes applied to the oscilla- 
tory discharge of a condenser. 

Alternating-Current Working.— Feed- 
ing lamps, motors, or other receptive 
devices by means of alternating cur- 
rents. 

Alternating Currents. — (1) Currents 
which flow alternately in opposite direc- 
tions. (2) Currents whose directions are 
periodically reversed. 

Alternating Discharge.— (1) A dis- 
charge which periodically changes its 
direction. (2) An oscillatory discharge. 

Alternating Dynamo - Electric Ma- 
chine. — An alternating-current dynamo- 
electric machine. 

Alternating Electromotive Forces. — 
Electromotive forces whose directions 
are periodically reversing. 

Alternating Electrostatic Field.— A 
field of electrostatic flux whose direction 
is periodically reversing. 

Alternating Electrostatic Potential.— 
An electrostatic potential whose value is 
periodically changing sign. 

Alternating Influence Machine— An 
electrostatic influence machine which de- 
livers periodically alternating electric dis- 
charges or currents. 

Alternating Magnetic Field.— A mag- 
netic field the direction of whose flux 
periodically changes. 

Alternating Magnetic Potential.— A 
magnetic potential whose value is period- 
ically changing sign. 

Alternating Magnetic Call-Bell.— A 



Alt]. 



676 



[Amp, 



call-bell operated by the uncommuted 
currents of a magneto-electric machine. 
Alternating Magneto - Electric Ma- 
chine. — A magneto-electric generator 
that produces alternating currents in its 
external circuit. 

Alternating Potential. — A potential, 
whether electrostatic, electric, or mag- 
netic, that is periodically changing in 
sign. 

Alternating Sparking Distance. — The 
air space across which an alternating- 
current disruptive-discharge would. pass. 

Alternation. — (1) A change in direction. 
(2) A change or reversal in the direction 
of an electromotive force or current. (3) 
A single vibration or oscillation as distin- 
guished from a complete cycle or double 
vibration. 

Alternation of Current. — A change in 
the direction of a current. 

Alternations. — Successive changes in the 
direction of a current or electro-motive 
force. 

Alternative Air-Path of Magnetic 
Flux. — In a ferric magnetic circuit a 
field, outside the iron of the circuit, 
through which a portion of the magnetic 
flux passes. 

Alternative Path. — The path or circuit 
taken by an impulsive discharge through 
an insulator in preference to a conducting 
path or circuit, of enormously smaller 
ohmic resistance, open to the discharge. 

Alternator. — The name generally given 
to an alternating-current dynamo or gen- 
erator. 

Amalgam. — A combination or mixture of 
a metal with mercury. 

Amalgam, Electric. — A substance with 
which the rubbers of the ordinary fric- 
tional electric machine are covered. 

Amalgamate. — To form into an amalgam. 

Amalgamating. — Forming into an amal- 
gam. 

Amalgamating Solution.— A solution 
of a salt of mercury employed for readily 
amalgamating the zincs of a voltaic 
battery. 

Amalgamation. — The act of forming into 
an amalgam or effecting the combina- 
tion of a metal with mercury. 

Amalgamation of Zinc— Coating the 
surface of the zinc of a voltaic cell with 
mercury. 

Amalgamator, Electric— An electrically 
driven amalgamator for the treatment of 
gold or silver ores with mercury. 



Amazite.— The name given to a particular 
kind of insulating material. 

Amber. — A resinous substance generally 
of a transparent yellow color. 

American Morse Code.— The Morse tele- 
graphic code employed in America, as 
distinguished from that employed in 
other parts of the w 7 orld. 

American System of Telegraphy. — 
The Morse system of telegraphy as em- 
ployed in America. 

American Telegraphic Code. — The 
American Morse code of telegraphic sig- 
nals. 

American Twist Joint.— A joint between 
two conducting wires in which each end 
is twisted around the other. 

American Wire Gauge.— The name gen- 
erally given to the Brown and Sharpe 
wire gauge, in which the largest wire, 
No. 0000, has a diameter of 0.46", the wire 
No. 36, 0.005", and all other diameters are 
in geometrical progression. 

Ammeter. — Any form of galvanometer 
which is capable of measuring current 
strength directly in amperes. 

Ammeter Panel of Switchboard.— In a 
central station the panel of the switch- 
board which carries the principal amme- 
ter or ammeters. 

Ammunition Hoist, Electric— An elec- 
trically operated hoist employed for rais- 
ing ammunition to the gun deck or turret 
of a ship. 

Amorphous. — Possessing no definite crys- 
talline form. 

Amperage. — The number of amperes pass- 
ing in a circuit in a given time. 

Ampere.— (1) The practical un , of electric 
current. (2) A rate of flow of electricity 
transmitting one coulomb per second. (3) 
The current of electricity which would 
pass through a circuit whose resistance is 
one ohm, under an electro-motive force 
of one volt. (4) A current of such a 
strength as will deposit 1.118 milli- 
grammes of silver per second from a spe- 
cifically prepared solution of silver ni- 
trate. 

Ampere-Arc — A single conductor, bent 
in the form of an arc of a circle, and used 
in an electric balance for measuring cur- 
rent. 

Ampere-Balance.— A balance form of 
ammeter which measures currents of a 
few amperes, or which determines a cur- 
rent strength of one ampere. 

Ampere-Centimetre.— A proposed unit 
of magnetic flux equal to the flux pro- 



Amp.] 



67' 



[Anae, 



duced by one ampere flowing through a 
circuit one centimetre in length. 

Ampere-Foot.— A unit of current strength 
multiplied by the distance to which said 
current is carried, employed in calculat- 
ing the fall of electric pressure in distri- 
buting mains. (2) The magnetic flux or 
flux density developed in a coil. 

Ampere-Hour. — (1) A unit of electrical 
quantity equal to the quantity of elec- 
tricity conveyed by one ampere flowing 
for one hour. (2) A quantity of elec- 
tricity equal to 3600 coulombs. 

Ampere-Hour • Efficiency of Storage 
Battery. — (1) In a cycle of charge and 
discharge, the ratio between the ampere- 
hours taken out of a storage battery and 
the ampere-hours put into it. (2) The 
quantity efficiency of a storage battery 
as distinguished from the energy effi- 
ciency. 

Ampere-Hour Meter.— A meter which is 
capable of measuring an electric supply 
in ampere-hours. 

Ampere-Hour Output of Storage Bat- 
tery. — The amount of useful electric 
quantity produced by a storage battery 
in ampere-hours. 

Ampere-Meter. — An ammeter. 

Ampere-Minute. — A unit of electrical 
quantity equal to the electric quantity 
conveyed by one ampere in one minute. 

Ampere-Bing. — A word sometimes used 
for ampere-turn. 

Ampere-Second. — (1) A unit of electric 
quantity equal to the quantity of elec- 
tricity conveyed by one ampere flowing 
for one second. (2) A coulomb. 

Ampere-Stream in Armature.— The ag- 
gregate current in amperes produced by 
all the conductors on a dynamo armature. 

Ampere-Tap.— In a system of electric dis- 
tribution a tap provided in a branch cir- 
cuit for carrying off a current of one am- 
pere. 

Ampere-Turn.— A unit of magneto-motive 
force equal to that produced by one am- 
pere flowing around a single turn of wire. 

Ampere- Volt. — A word sometimes used 
for volt-ampere, or watt. 

Ampere-Yard. — A proposed unit of elec- 
tric current multiplied by distance 
through which said current is carried, 
sometimes employed in calculations. 

Ampere-Winding.— A word sometimes 
used for ampere-turn ; i. e. , a single wind- 
ing or turn through which one ampere 
passes. 

Ampere-per-Square-Centimetre. — A 



unit of density of current expressed in 
amperes-per-square-centimetre of normal 
cross-section of conductor. 

Ampere-per-Square-Inch.— A unit of 
density of current expressed in amperes 
per-square-inch of area of normal cross- 
section of conductor. 

Ampere's Rule for Deflection of Nee- 
dle. — The north-seeking pole of a mag- 
netic needle is deflected by a current to 
the left-hand of an observer who is sup- 
posed to be swimming in the current 
while facing the needle. 

Ampere's Theory of Magnetism.— A 
theory or hypothesis which ascribes the 
cause of magnetism to the presence of 
electric currents in the ultimate particles 
of a magnet. 

Amperian Currents.— The electric cur- 
rents that are assumed, in the Amperian 
theory of magnetism, to flow in closed 
circuits around the ultimate particles of 
a magnet. 

Amphigenic Charge. — A name proposed 
for an electric charge, whose surface den- 
sity varies in sign. 

Amplitude of Galvanometer Swing.— 

(1) In a series of ballistic galvanometer 
deflections, the half sum of the deflection 
or elongation from zero, on one side of the 
scale, and the means of the preceding and 
following elongations on the other side. 

(2) When referred to radian measure the 
ratio of the above quantity to the distance 
of the scale from the mirror. 

Amplitude of Simple-Harmonic Mo- 
tion. — The maximum cyclic value of a 
simple-harmonic or simple-periodic vibra- 
tion ; or, the distance in a straight line 
from the median position to the position 
of greatest elongation. 

Amplitude of Vibration or Wave. — 
The extent of the excursion of a simply 
vibrating particle on either side of its vi- 
brating point or point of rest. 

Amyl-Acetate Standard.— (1) A photo- 
metric standard lamp of definite dimen- 
sions burning amyl-acetate. (2) The 
Hefner- Alteneck standard lamp. 

Amyloid.— (1) A substance employed in 
the manufacture of incandescent lamp 
filaments produced by the action of sul- 
phuric acid on cellulose. (2) Parchment- 
ized cellulose. 

Amyloid Filament. — An incandescent 
lamp filament made from amyloid. 

Aneemic Cataphoresis. — Cataphoretic 
medication accompanied by the applica- 
tion of bandages to .retard local circula- 
tion in the parts treated. 



Anae.] 



678 



[Ang. 



Anaesthesia.— Insensibility to pain. 

Anaesthesia, Electric.— Nervous insen- 
sibility obtained by electrical means. 

Analogous Pole. — In a pyro-electric sub- 
stance like tourmaline, the pole that ac- 
quires a positive electrification while the 
temperature of the crystal is rising. 

Analysis. — The determination of the com- 
position of a compound substance by sep- 
arating it into the elementary substances 
of which it is composed. 

Analysis, Electric. — The determination 
of the composition of a compound sub- 
stance by electric means. 

Analyzable. — Capable of being analyzed. 

Analyze. — To separate into component 
parts. 

Analyzer, Electric— A gridiron of me- 
tallic wires which is transparent to per- 
pendicularly incident electro-magnetic 
waves, when the length of the wires is 
perpendicular to the electric oscillations, 
but is opaque to them, that is, possesses 
the ability to absorb or reflect them, when 
rotated 90° from its former position ; i. e., 
when parallel to the electric oscillations. 

Analyzing. — Separating into component 
parts. 

Anaphoresis. — A term sometimes applied 
for the electric osmose which occurs in 
the neighborhood of the anode. 

Anchor. — In a trolley system the diagonal 
tie wires which bind the trolley wire 
longitudinally to adjacent poles in order 
to maintain a uniform degree of tension 
in the trolley wire. 

Anchor Log. — A log partially buried in the 
ground and serving as an anchor for a tel- 
egraphic pole. 

Anchor Platform. — A frame-work at- 
tached to an anchor-pole by means of 
which the pole is solidly set in the earth. 

Anchor Pole. — (1) A pole for overhead 
wires of sufficient stiffness to take the en- 
tire tension at points where an abrupt 
angle occurs, or where the conductors 
enter underground conduits. (2) A ter- 
minal pole. 

Anchor-Ring Core.— A toroidal core. 

Anchor Strain-Ear.— In an overhead 
trolley system a trolley ear or insulator 
employed for anchoring the trolley wire, 
or maintaining it taut, so as to ensure 
good and continuous contact with the 
trolley wheel. 

Anchored. — (l)Kept in position by means 
of an anchor strain-ear. (2) Kept in posi- 
tion by means of an anchor, as a buoy or 
ship. (3) Maintained in a given position. 



Anchored Filament.— An incandescent 
lamp filament supported at its centre to* 
prevent injury to it by excessive vibra- 
tion. 

Anelectric — A word formerly applied to 
conducting substances which it was be- 
lieved could not be electrified by friction. 
(Obsolete.) 

Anelectrotonic State.— The state or con- 
dition of electrotonus. 

Anelectrotonic Zone. — The polar zone. 

Anelectrotonus.— The decreased func- 
tional activity which occurs in a nerve in 
the neighborhood of the anode or positive 
electrode. 

Anemograph. — A recording anemometer. 

Anemograph, Electric— An electrically 
recording anemometer. 

Anemometer. — An apparatus for record- 
ing the intensity and direction of the 
wind. 

Anemometer, Electric— An apparatus 
for electrically recording the intensity 
and direction of the wind. 

Anemometry.— The measurement of the 
direction and intensity of the wind. 

Anemoscope. — An instrument which in- 
dicates but does not measure the inten- 
sity, or record the direction of the wind. 

Aneroid.— Devoid of liquid. 

Aneroid Barometer. — An apparatus for 
measuring atmospheric pressure, which 
operates by the to-and-fro movements of 
one of the walls of a partially exhausted 
elastic metallic box. 

Angle. — The deviation of direction be- 
tween two intersecting lines or planes. 

Angle Cathetometer.— A cathetometer 
suitable for measuring angular deviation. 

Angle of Declination.— (1) The angle 
which measures the deviation of the mag- 
netic needle to the east or west of the true 
geographical north. (2) The angle of va- 
riation of a magnetic needle. 

Angle of Dielectric Hysteretic Lag. — 
In a condenser traversed by an alterna- 
ting current the angle whose tangent is 
equal to the ratio of the hysteretic con- 
ductance to the hysteretic susceptance of I 
the condenser, or to the angle whose co- 
tangent is the ratio of the hysteretic re- 
actance of condensance to the hysteretic 
resistance of the condenser. 

Angle of Dip.— (1) The angle which a 
magnetic needle, free to move in both a 
vertical and horizontal plane, makes with 
the horizontal line passing through its 
point of support. (2) The angle of inclina- 
tion of a magnetic needle. 



Ang.] 



679 



[Ann. 



Angle of Hysteretic Advance of Phase. 

The angle by which the equivalent sine 
wave of exciting current leads the sine 
wave of magnetism, in a transformer or 
choking coil containing iron. 

Angle of Inclination. — The angle of dip. 

Angle of Lag.— The angle of lag of a dy- 
namo-electric machine. 

Angle of Lag of Current.— (1) An angle 
whose tangent is equal to the ratio of the 
inductive to the ohmic resistance in a cir- 
cuit. (2) An angle whose cosine is equal 
to the ohmic resistance divided by the 
impedance of a circuit. (3) An angle 
whose cosine is the ratio of the real to the 
apparent power in an alternating-current 
circuit. 

Angle of Lag of Dynamo-Electric Ma- 
chine. — (1) The angle through which the 
axis of magnetization of the armature of 
a dynamo-electric machine is shifted by 
reason of the resistance its core offers to 
cyclic reversals of magnetization. (2) 
The angle through which the axis of 
magnetization of the armature of a dyna- 
mo-electric machine is shifted by reason 
of both hysteresis and armature reaction. 
(3) The backward angular deviation from 
the normal of the brushes of a motor in 
order to secure sparkless commutation. 

Angle of Lead.— The forward angular de- 
viation from the normal position which 
must be given to the collecting brushes 
on the commutator of a continuous-cur- 
rent generator in order to obtain quiet 
commutation . 

Angle of Maximum Sensitiveness of 
Galvanometer.— The angle of deflection 
at which a given small alteration in the 
current strength produces the greatest 
deflection of the change in the needle. 

Angle of Polar Span. — The angular dis- 
tance which the pole pieces extend cir- 
cumf erentially around the armature bore. 

Angle of Variation.— The angle of de- 
clination of the magnetic needle. 

Angular. — Of or pertaining to an angle. 

Angular Acceleration. — The time rate 
of change of angular velocity. 

Angular Couple. — The angular force. 

Angular Currents. — Currents flowing 
through circuits which intersect one an- 
other at any angle. 

Angular Energy. — The product of one- 
half the square of the angular velocity 
and the moment of inertia. 

Angular Force. — The force which causes 
the rate of change of angular momentum. 

Angular Momentum.— The product of 



the moment of inertia at any instant and 
the angular velocity. 
Angular Torque.— The angular twist or 
couple. 

Angular Velocity.— (1) The velocity of a 
point moving relatively to a centre of 
rotation or to some selected point, and 
usually measured in degrees per second, or 
in radians per second. (2) In a sinusoidal- 
current circuit the product of 6.2832 and 
the frequency of the current. 

Angular Wire Gauge.— A wire gauge 
measurer formed of a metallic strip con- 
taining a tapering, or acute-angled slot 
with graduated edges. 

Animal Electricity.— Electricity pro- 
duced in the bodies of animals during 
life. 

Animal Magnetism.— A term sometimes 
applied to hypnotism or artificial som- 
nambulism. 

Anion. — The electro-negative ion or radical 
of a molecule. 

Anisotropic Conductor.— A conductor 
which though homogeneous in structure 
possesses different conductivities in dif- 
ferent directions. 

Anisotropic Medium.— (1) A medium 
in which equal stresses do not produce 
equal strains when applied in different 
directions. (2) An eolotropic medium. 

Annealing. — The art of softening metals 
by heating and subsequent gradual cool- 
ing. 

Annealing, Electric— A process for an- 
nealing metals in which electric heat is 
substituted for ordinary heat. 

Annual Inequality of Earth's Mag- 
netism. — (1) A variation in any of the 
elements of the earth's magnetism de- 
pendent upon the relative position of the 
sun and earth. (2) Annual variations in 
the earth's magnetism. 

Annual Load-Factor.— (1) The ratio be- 
tween the mean output of a central station 
in one year, and the maximum output at 
any time during the year. (2) The ratio 
between the mean daily output of a cen- 
tral station in one year, and the mean 
daily maximum output in the same year. 

Annual Variations of Magnetic 
Needle. — Variations in the magnetic de- 
clination that occur at regular periods of 
the year. 

Annunciator Board. — A board on which 
annunciator drops are placed. 

Annunciator Clock, Electric— A clock 
employed in connection with an an- 
nunciator for automatically disconnect- 



Ann.] 



680 



[Ant, 



ing certain circuits at certain predeter- 
mined times. 

Annunciator Drop. — An annunciator 
signal whose dropping indicates the clos- 
ing or opening of the circuit of a partic- 
ular electro-magnet connected therewith. 

Annunciator Wire.— A class of insulated 
wire prepared for use in annunciator 
circuits. 

Anodal. — Of or pertaining to the anode. 

Anodal Diffusion.— A word sometimes 
used for cataphoretic medication. 

Anode. Ml) The conductor or plate of a 
decomposition cell connected with the 
positive terminal of a battery or other 
electric source. (2) The terminal of an 
electric source out of which the current 
flows into the electrolyte of a decompos- 
ing cell or voltameter. (3) In a vacu- 
um tube, electrolytic cell, bath, or re- 
ceptive device, the terminal at which the 
current enters, as distinguished from the 
cathode, at which the current leaves. 

Anodic. — Of or pertaining to the anode. 

Anodic Closure Contraction. — The 
muscular contraction produced by the 
closing of a voltaic circuit, the anode of 
which is placed over a nerve, and the 
cathode at some other part of the body. 

Anodic Contraction. — The muscular con- 
traction produced in the neighborhood of 
the anode, either on opening or closing 
the circuit. 

Anodic Currents. — In a polarized voltaic 
couple immersed in acidulated water, 
the electric currents produced by the 
agitation of the plate connected with the 
anode. 

Anodic Duration Contraction.— The 
time during which a muscle continues 
contracted on the opening or closing of a 
circuit whose anode is placed over the 
part contracted. 

Anodic Electro-Diagnostic Reactions. 
The characteristic reactions which oc- 
cur at the anode of an electric source 
placed over any part of a living body. 

Anodic Opening Contraction.— The 
muscular contraction produced by the 
opening of a voltaic circuit the anode of 
which is placed over a nerve and the 
cathode at some other part of the body. 

Anodic Rays. — The radiation claimed to 
emanate from the anode of an X-ray tube. 

Anodic Zone. — The zone or region sur- 
rounding the anode when employed as a 
therapeutic electrode. 

Anodograph. — A word proposed for a 
radiograph. 



Anomalous.— (1) Irregular. (2) Not in 
accordance with the ordinary rule. 

Anomalous Dispersion.— An abnormal 
dispersion in which the order of the wave 
frequencies is inverted as regards their 
order in ordinary dispersion. 

Anomalous Helix.— A helix wound so as 
to produce an anomalous magnet. 

Anomalous Magnet. — A magnet possess- 
ing more than two free poles. 

Anomalous Magnetization.— (1) The 
magnetization produced by the oscillatory 
discharge of a condenser or Ley den jar. 
(2) Magnetization which produces more 
than two free poles in a magnet. 

Anomalous Pole. — A name sometimes 
given to those poles of an anomalous 
magnet which consist of two similar 
adjacent poles. 

Anomalous Solenoid. — An anomalous 
helix. 

Anomalous Spiral. — An anomalous helix. 

Answer Back Signal. — A return signal. 

Answering Call-Box. — A call-box at 
which an answering signal is obtained, 
indicating that the call has been received 
at the central station. 

Answering Board. — In a telephone 
switchboard the board holding the an- 
swering jacks. 

Answering Jacks.— In any panel of a 
telephone switchboard the jacks con- 
nected with the subscribers whose calling 
drops are placed in that panel, so that 
each call may be immediately answered 
at an adjacent jack. 

Answering Key. — In a telephone switch- 
board a lever contact key which enables 
the operator to bring her head telephone 
into connection with any subscriber. 

Anti-Cathode of X-Ray Tube.— (1) A 

deflection plate placed opposite the ca- 
thode of an X-ray tube. (2) A platinum 
plate supported inside an X-ray tube to 
receive the cathodic bombardment. 

Anti-Conical System of Distribution. 
A system of conical conductors employed 
in anti-parallel feeding. 

Anti-Hum. — A device for lessening the 
humming sound due to the vibration of 
an aerial wire. 

Anti-Induction.— Opposing or preventing 
induction and its effects. 

Anti-Induction Cable.— A cable whose 
conductors are so arranged as to avoid 
the effects of induction, either from them- 
selves or from neighboring conductors. 

Anti-Induction Conductor.— A con- 



Ant.] 



681 



[App. 



ductor constructed so as to avoid injur- 
ious inductive effects from neighboring 
circuits. 

Anti-Induction Telephone Cable. — 
(1) A telephone cable in which the con- 
ductors are so arranged as to neutralize 
the effects of induction produced by- 
neigh boring circuits. (2) A telephone cable 
in which the effects of electrostatic in- 
duction from neighboring circuits is 
avoided by a metallic covering or sheath- 
ing that is grounded at suitable inter- 
vals. 

Antilogous Pole. — The pole of a pyro- 
electric substance like tourmaline, which 
acquires a negative electrification while 
the temperature of the crystal is rising. 

Antimonious Lead. — An alloy of lead 
and antimony employed for the grid of a 
storage battery because it is not acted on 
by the charging current. 

Antinode. — The point in a vibrating string, 
wire, or plate, midway between adjacent 
nodes. 

Anti-Parallel Feeding.— A method of 
feeding in a system of parallel distribu- 
tion in which the pressure at the ter- 
minals of all the translating devices is 
kept approximately uniform by employ- 
ing mains tapering in opposite directions ; 
that is, with their large ends connected 
to the generator terminals or bus-bars, 
and the mains proceeding in opposite 
directions around the circuit to be sup- 
plied. 

Anti-phase.— (1) A phase relation be- 
tween two periodic currents such that 
they tend to decrease the amplitude of 
the motion. (2) Phase opposition. 

Anvil of Telegraph Key.— The front 
stop of a Morse telegraph key, upon which 
the lever descends in signalling. 

Aperiodic. — (1) Not characterized by 
periodicity. (2) Devoid of periodicity. 
(3) Coming to rest steadily wuthout oscil- 
lations. 

Aperiodic Galvanometer.— (1) A gal- 
vanometer whose needle comes to rest 
without any oscillation. (2) A dead- 
beat galvanometer. 

A-Pole. — A telegraph double-pole shaped 
like a letter A. 

Apparent Electromotive Force.— The 
E. M. F. apparently acting in a circuit as 
measured by the drop of pressure due to 
the resistance of the circuit and the cur- 
rent strength passing through it. 

Apparent Coefficient of Induction.— 
A term sometimes used for the apparent 
inductance in a circuit which either en- 



velops iron, or is inductively associated 
with secondary circuits. 
Apparent Coefficient of Magnetic In- 
duction. — The apparent permeability of 
a substance as expressed by the amount 
of magnetic flux that passes through it 
per unit of normal cross-sectional area, 
differing from the true value on account 
of the presence of eddy currents. 

Apparent Conductor-Resistance.— The 

impedance of a conductor which forms 
part of an alternating-current circuit con- 
taining both resistance and reactance. 

Apparent Efficiency of Alternator.— 

The ratio of the electric activity delivered 
at the terminals of an alternator, as the 
product of volts and amperes supplied, to 
the activity mechanically absorbed at its 
pulley or shaft ; in contradistinction to 
the efficiency determined from the true 
electric activity delivered. 

Apparent Efficiency.— The efficiency of 
a generator, motor, or other apparatus, in 
an alternating-current circuit based upon 
the volt-amperes or apparent power as dis- 
tinguished from efficiency based on real 
powder. 

Apparent Efficiency of Alternating- 
Current Motor. — The ratio of the power 
mechanically delivered by the motor to 
the apparent activity it receives at its ter- 
minals ; as distinguished from the effi- 
ciency based upon the real electric activity 
received. 

Apparent Energy. — (1) The product of 
the effective current and the effective 
pressure in an alternating-current circuit. 
(2) Apparent activity, as opposed to true 
activity. (3) In a sinusoidal-current cir- 
cuit, or simple alternating-current circuit, 
the product of effective volts and effective 
amperes uncorrected for the cosine of the 
angle of their phase difference. 

Apparent Expansion. — The increase in 
the volume of a liquid by expansion irre- 
spective of the expansion of its con- 
taining vessel. 

Apparent Insulation. — The insulation 
resistance of a circuit, uncorrected for 
the effect of leakage in the measuring 
current. 

Apparent Impedance. — (1) In an alter- 
nating-current circuit the virtual imped- 
ance in a primary circuit due to the 
presence of an associated secondary cir- 
cuit. (2) The joint impedance of a net- 
work of impedances. 

Apparent Insulation of Telegraphic 
Line. — The insulation of a telegraph line 



App.] 



682 



[Arc. 



uncorrected for its conductor resistance, 
or for the drop in testing potential at the 
more remote portions. 

Apparent Magnetization.— The magnet- 
ization due to the superposition of two 
separate magnetizations. 

Apparent Power. — In an alternating- 
current circuit, the apparent watts, or the 
product obtained by multiplying the volts 
by the amperes, as read directly from a 
voltmeter and ammeter. 

Apparent Reluctance. — The reluctance 
of a magnetic circuit, or portion thereof, 
under the influence of a complex of such 
superposed magnetic fluxes as may prac- 
tically be developed, as distinguished 
from its reluctance under a single mag- 
netising force. 

Apparent Resistance. — The impedance 
in an alternating-current circuit or por- 
tion thereof. 

Apparent Torque Efficiency.— In an 
alternating-current motor, the ratio of the 
torque actually developed to the torque 
which it would give at the same volt- 
ampere or apparent electric input in volt- 
amperes if there were neither internal 
losses nor phase displacement in the motor. 

Apparent Watts. — The apparent power 
in an alternating-current circuit as dis- 
tinguished from the real power. 

Apron Grapnel. — A form of grapnel for 
grappling a cable in which the prongs are 
protected from breakage on rocks by an 
apron or covering, only a sufficient space 
being left between the apron and the 
prongs for the entrance of the cable. 

Aqueous Solution. — A solution of a salt 
or other substance in water. 

Arago's Disc. — A disc of copper or other 
non-magnetic metallic substance which, 
when rapidly rotated under a magnetic 
needle supported independently of the 
disc, causes the needle to be deflected in 
the direction of rotation, and. when the 
velocity of the disc is sufficiently great, to 
rotate with it. 

Arborescent Discharges. — Disruptive 
discharges obtained from a high-potential 
discharge of a series-connected battery. 

Arborescent Deposits. — Tree-shaped 
electro-metallurgical deposits. 

Arc— (1) A voltaic arc. (2) A portion of a 
circle, or other plane conic section. 

Arc. — To discharge in the form of a voltaic 
arc. 

Arc Ammeter. — An ammeter on an arc 
circuit. 

Arc Blow-Pipe, Electric— A blow-pipe 



in which the air-blast is obtained by a. 
convective discharge. 

Arc-Circuit Cut-Out.— A cut-out placed 
in a series arc-light circuit to prevent the- 
extinguishment of any lamp from break- 
ing the entire circuit. 

Arc-Circuit Cut-Out Box.— A box for 
holding an arc-circuit cut-out. 

Arc-Circuit Indicator.— A device in the 
form of a simple galvanometer which in- 
dicates when the current is passing 
through an arc-light circuit. 

Arc Crater Photometric Standard.— A 

photometric standard based on the inten- 
sity of light normally emitted from a 
definite area of the crater of a carbon 
voltaic arc. 

Arc, Electric. — A term sometimes em- 
ployed for the voltaic arc. 

Arc-Lamp, Electric— (1) An electric lamp 
whose source of light is the voltaic arc. 
(2) An incandescent electric lamp, em- 
ployed to illumine the circles of telescopes 
or other instruments in an observatory. 

Arc-Lamp Compensator.— A reactive or 
choking coil, placed in the circuit of a 
lamp or lamps for the purpose of auto- 
matically regulating the amount of cur- 
rent passing through the lamp or lamps. 

Arc-Lamp Globe. — A glass globe sur- 
rounding the arc of an arc lamp. 

Arc-Lamp Hand-Board. — An arc-lamp 
hanger-board. 

Are-Lamp Hanger. — A board from which 
an arc lamp is suspended, provided with 
electric connections for readily short-cir- 
cuiting the lamp. 

Arc-Lamp Spark-Arrester. — A gauze 
chimney surrounding the arc and em- 
ployed for the purpose of preventing fires 
when arc lamps are placed near com- 
bustible materials, as in shop windows. 

Arc-Lamp Suspension-Board. — (1) A 
board for suspending an arc lamp. (2) 
an arc-lamp hanger-board. 

Arc-Light . — The light of the carbon 
voltaic arc. 

Arc-Light Circuit. — (1) A circuit in ( 
which arc-lights are placed. (2) Gen- 
erally, a series-connected circuit. 

Arc-Light Cut-Out. — A switch for short- 
circuiting an arc-lamp and so cutting it- 
out of the circuit. (2) A cut-out which 
automatically removes an arc-lamp from 
the circuit. 

Arc-Light Difiuser. — Any diff user for 
scattering or diffusing the light from an 
arc light so as to avoid the production of 
intense shadows. 



Arc] 



683 



[Arm, 



Arc-Light Generator.— A dynamo-elec- 
tric machine that furnishes current for 
arc-light circuits. 

Arc-Light-Points. — The carbon pencils 
between which the arc is maintained in 
an arc light. 

Arc-Light Projector.— An arc lamp pro- 
vided with a reflector for obtaining a 
beam of approximately parallel rays of 
light. 

Arc-Light Meter. — A form of electric 
current timer. 

Arc-Light Regulator.— A device, gene- 
rally automatic, for maintaining the car- 
bons of an arc-lamp a constant distance 
apart during the operation of the lamp. 

Arc-Light Tower. — A tower employed in 
out-door illumination for supporting a 
number of arc lamps. 

Arc-Light Transformer. — A transfor- 
mer which supplies alternating currents 
to arc-lamps. 

Arc-Lighter. — An arc-light generator. 

Arc-Lighting.— Artificial illumination 
obtained by means of arc lights. 

Arc-Lighting Dynamo-Electric Ma- 
chine. — An arc-light generator. 

Arc Plug-Switchboard. — A switchboard 
provided with spring-jack contacts con- 
nected with the terminals of different 
circuits, and plug switches connected with 
the dynamo terminals, by means of which 
any dynamo can be connected with any 
circuit ; or a number of circuits connected 
with the same dynamo ; or a number of 
separate dynamos placed in the same 
circuit. 

Arc Micrometer.— An apparatus for 
measuring the length of a voltaic arc by 
means of a micrometer. 

Arc Standard of Light. — A photometric 
standard based on the intensity of the 
light emitted by a given area of crater of 
the positive carbon in a carbon arc. 

Arc Switchboard. — An arc plug-switch- 
board . 

Arcing. — Discharging by means of voltaic 
arcs. 

Areometer. — An instrument for readily 

. determining the specific gravity of 
liquids. 

Areometry. — The measurement of the 
specific gravity of liquids by means of 
areometers. 

Argand Electric Burner. — An Argand 
burner provided with a device for elec- 
trically igniting the gas. 



Argand Electric Lighter.— An Argand 
electric burner. 

Argand Valve-Burner or Lighter.— 
An Argand burner provided with means 
whereby the gas can be both turned on 
and lighted electrically. 

Argymometry. — The art of determining 
the weight of electrically deposited silver. 

Arithmetical Mean Value of Periodic 
Current of E. M. P. Wave.— The arith- 
metical average of all the instantaneous 
values during one complete period. 

Arm of Balance or Bridge. — One of the 

resistances of an electric balance or 
bridge. 

Arms of Balance or Bridge.— Two sepa- 
rate resistances, the value of one of which 
is usually a decimal multiple of the other, 
employed in an electric bridge or balance, 
in connection with a known resistance, 
to determine the value of an unknown 
resistance. 

Armature. — (1) A mass of iron or other 
magnetizable material placed on or near 
the poles of a magnet. (2) The armature 
of a dynamo-electric machine. 

Armature Bars. — (1) Heavy copper bars 
of rectangular or trapezoidal cross-sec- 
tion, or of imbricated rectangular strips, 
or of rectangular bars of compressed 
stranded wire, or of special forgings, em- 
ployed on large drum armatures in place 
of the ordinary wire windings. (2) Heavy 
conductors employed for armature wind- 
ings. 

Armature Binding Wires. — Coils of 
wire bound on the outside of the armature 
wires for the purpose of preventing their 
separating from the armature core by 
centrifugal force. 

Armature Bore. — The space between the 
pole-pieces of a dynamo or motor provided 
for the rotation of the armature. 

Armature Chamber. — (1) The armature 
bore. (2) An armature pocket. 

Armature Chambers. — Spaces left in the 
armature core for the reception of the 
armature coils. 

Armature Core-Discs.— The thin discs 
of sheet-iron that form, when assembled, 
the laminated core of the armature of a 
dynamo or motor. 

Armature Core of Dynamo.— The mass 
of laminated iron on which the armature 
coils or conductors of a dynamo or motor 
are placed. 

Armature Covering.— A covering of can- 
vas or other suitable material placed on 
an armature for the purpose of protecting 
its conductors from injury or dirt. 



Arm.] 



684 



[Art. 



Armature Hole.— (1) The armature bore. 
(2) A hole made in the core for the recep- 
tion of an armature coil or winding. 

Armature Inductors. — The bars, strips, 
or coils, placed on the dynamo armature 
core, in which electromotive forces are 
induced by rotation. 

Armature Loop. — The single conducting 
coil or loop on a dynamo or motor arma- 
ture. 

Armature of Cable. — The sheathing or 
protective coat placed on the outside of a 
cable. 

Armature of Condenser. — A term some- 
times applied to the metallic plates or 
coatings of a condenser or Leyden jar. 

Armature of Dynamo.— (1) Coils of in- 
sulated wire together with the iron core 
on or around which such coils are wpund. 
(2) That part of a dynamo in which useful 
differences of potential or useful currents 
are generated. (3) Generally that part of 
a dynamo which is revolved between the 
pole-pieces of the field magnets. (4) That 
member of a dynamo in which the mag- 
netic flux is caused to successively fill 
and empty the coils and thereby gener- 
ate E. M. Fs. 

Armatures of Holtz Machine.— The 
pieces of paper that are placed on the 
stationary plate of a Holtz, or other simi- 
lar electrostatic induction machine, near 
the openings in the same. 

Armature Pinion. — A toothed wheel 
placed on the armature shaft of a street- 
car motor for engaging the teeth of the 
reducing gear. 

Armature Pockets. — Spaces provided in 
an armature core for the reception of the 
armature coils. 

Armature Projections.— Those portions 
of the armature core between which the 
armature slots, pockets, or chambers are 
situated. 

Armature Reaction.— The reactive mag- 
netic influence produced, by the current 
in the armature of a dynamo or motor, 
on the magnetic circuit of the machine. 

Armature Segment. — That portion of an 
armature winding, or armature inductor, 
whose circuit is included between two 
contiguous segments of the commutator. 

Armature Slots.— Slots provided in an 
armature core for the reception of the 
armature coils. 

Armature Spider.— A metal frame-work, 
keyed to the armature shaft, and pro- 
vided with radial arms for firmly holding 
the armature core. 



Armature Stampings.— Stampings of 
soft sheet iron intended for the core discs 
of a laminated armature core. 

Armature Turns. — The separate turns of 
conductors on the armature of a dynamo 
or motor. 

Armature Varnish. — An insulating var- 
nish sometimes applied to armature wind- 
ings for the purpose of increasing their 
powers of resisting moisture and friction. 

Armature Winding-Space.— Longitu- 
dinal grooves or spaces left in the arma- 
ture core for the reception of the arma- 
ture coils. 

Armed Magnet. — A magnet provided 
with an armature. 

Armor of Cable.— The protecting sheath- 
ing or metallic covering of a submarine 
or other electric cable. 

Armored. — Provided with armor, as of the 
protective sheathing of a cable. 

Armored Cable. — A cable provided with 
a protective sheathing or armor. 

Armored Conductor.— A conductor pro-' 
vided with a protective sheathing or 
armor. 

Army Telegraph.— The telegraphic ap- 
paratus employed in field service in the 
army. 

Arrester Plate of Lightning Protec- 
tor. — The ground-connected plate of a 
comb lightning-arrester. 

Arrester Plates . — A term sometimes ap- 
plied to the two plates of an ordinary 
comb lightning-protector. 

Arrival Curve of Current in Sub- 
marine Cable or Telegraphic Cir- 
cuit. — A curve showing the gradual 
increase in the strength of current reach- 
ing the receiving end of a submarine 
cable under a given condition of signal- 
ling. 

Articulate Speech. — The successive tones 
of the human voice that are necessary to 
produce intelligible words. 

Artificial Cable. — A circuit containing 
associated resistance and capacity, and 
employed in a system of duplex sub- 
marine telegraphy corresponding to the 
artificial line in duplex aerial line tele- 
graphy. 

Artificial Cable Leak. — A leak purpose- 
ly introduced at some point in the circuit 
of an artificial cable employed in duplex 
cable telegraphy. 

Artificial Carbons. — Carbons obtained 
by the carbonization of a mixture of pul- 
verized carbon with a carbonizable liquid. 



Art.] 



685 



[Ato. 



Artificial Fault in Cable.— A fault pur- 
posely made in an artificial cable for the 
purpose of studying its behavior under 
tests. 

Artificial Illumination.— The employ- 
ment of artificial sources of light. 

Artificial Line. — In duplex telegraphy a 
combination of resistance coils and con- 
densers which serves to balance an actual 
telegraph line. 

Artificial Magnet. — A magnet produced 
by induction from another magnet or 
from an electric current. 

Asbestos Porcelain. — A porous sub- 
stance, somewhat resembling ordinary 
porcelain, employed for the porous cells 
of voltaic batteries. 

A-Side of Quadruplex Table.— That 
side of a quadruplex system which is 
worked by means of reversed currents. 

Asphyxia. — Suspended respiration event- 
ually resulting in death from non-aeration 
of the blood. 

Assumed Direction of Flow of Cur- 
rent. — A convention which regards the 
current as leaving an electric source at 
its positive pole, and returning to it at its 
negative pole. 

Assymmetrical. — Devoid of symmetry. 

Assymmetrical Resistance.— A resist- 
ance which is claimed to be greater to a 
flow of current in one direction than in 
another. 

Astatic. — Devoid of magnetic directive 
power. 

Astatic Circle. — A term sometimes used 
for astatic circuit. 

Astatic Circuit. — A circuit, consisting of 
two closed curves enclosing equal sur- 
faces, which is not deflected by the 
earth's field on the passage of a current 
through it. 

Astatic Couple. — Two magnets of equal 
strength so placed one above the other in 
a vertical plane as completely to neutral- 
ize each other's effects. 

Astatic Galvanometer.— A galvanometer 
provided with an astatic needle or cir- 
cuit. 

Astatic Multiplier. — An astatic galvano- 
meter. 

Astatic Needle. — (1) A compound mag- 
netic needle of great sensibility, possess- 
ing little or no directive power. (2) An 
astatic needle consisting of two separate 
needles rigidly connected and placed par- 
allel one directly over the other with 
opposite poles opposed. 

Astatic Pair. — An astatic couple. 



Astatic System. — An astatic combination 

of magnets. 
Astaticizing. — Rendering a system astatic. 
Astigmatism. — A defect in the lenses of 

the eye which prevents horizontal and 

vertical lines from being in focus at the 

same time. 
Astronomical Meridian.— A great circle 

passing through any point of the heavens 

and the north and south poles of the 

heavens. 

Asymptote of Curve.— A straight line 
which continually approaches a curved 
line, but which meets it only at an in- 
finite distance. 

Asynchronism.— Devoid of synchronism. 

Asynchronous. — Occurring or acting 
non-simultaneously. 

Asynchronous Alternating-Current 
Motor. — A motor whose speed is not 
synchronous with that of its driving gen- 
erator, both machines having the same 
number of poles. 

Atmosphere. — (1) A unit of gaseous or 
fluid pressure equal to 14-73 pounds per 
square inch. (2) The ocean of air which 
surrounds the earth. 

Atmospheric. — Of or pertaining to the 
atmosphere. 

Atmospheric Cathode Discharge.— An 
X-ray discharge which is assumed to ac- 
company and form part of the sun's 
radiation. 

Atmospheric Electricity. — The free 
electricity which is present in the atmos- 
phere. 

Atom. — (1) An ultimate particle of mat- 
ter. (2) The smallest quantity of ele- 
mentary or simple matter that can exist. 

Atom of Electricity. — A quantity of 
electricity equal in amount to that pos- 
sessed by any chemical monad atom. 

Atomic. — Of or pertaining to the atom. 
Atomic Attraction. — (1) The attraction 

which causes the atoms to combine. (2) 

Chemical affinity. 
Atomic Capacity. — The equivalence or 

valency of an atom. 

Atomic Currents. — A term sometimes 
employed instead of molecular or Ampe- 
rian currents. 

Atomic Energy. — Chemical potential 
energy. 

Atomic Heat. — A constant product ob- 
tained by multiplying the specific heat of 
an elementary substance by its atomic 
weight. 



Ato.] 



686 



[Aut. 



Atomic Weight.— The relative weight of 
the atoms of elementary substances. 

Atomicity. — (1) The combining capacity 
of the atoms. (2) The relative equiva- 
lence of the atoms, or their atomic ca- 
pacity. 

Atomization. — The act of obtaining li- 
quids in a spray of finely divided parti- 
cles. 

Atomize. — To separate into a spray by 
means of an atomizer. 

Atomizer. — An apparatus for readily ob- 
taining a finely divided jet or spray of 
liquid. 

Attachment Plug.— A plug provided for 
insertion in a screw socket or spring jack, 
for the ready connection of a lamp or 
other receptive device to a circuit. 

Attract. — To draw together. 

Attracted-Disc Electrometer.— A form 
of electrometer in which the force is 
measured by the attraction existing be- 
tween two charged discs. 

Attracting. — Drawing together. 

Attraction. — Literally the act of drawing 
together. 

Attraction of Gravitation.— (1) Mass at- 
traction ; or, the attraction which causes 
masses of matter to tend to move towards 
one another. (2) The attraction which 
causes bodies to fall to the earth. (3) Molar 
attraction. 

Attractions and Repulsions of Cur- 
rents. — The tendency of active circuits 
to be attracted to or repelled from one 
another by the mutual action of their 
magnetic fields. 

Audible Code. — A term employed in rail- 
way signalling for a code of audible sig- 
nals in railway service. 

Audible Telegraphic Signal.— A signal 
which is received by the ear in contra- 
distinction to a visual signal or one re- 
ceived by the eye. 

Audiometer. — A form of induction bal- 
ance or sonometer employed in testing 
the acuteness of hearing. 

Audiphone. — A thin plate of hard rubber 
held in firm contact with the teeth and 
maintained at a certain tension by strings 
attached to one of its edges, employed for 
the purpose of aiding the hearing. 

Auger. — A boring tool for cutting holes 
for telegraph poles. 

Aura, Electric. — A term sometimes ap- 
plied to an electric brush or convective 
discharge. 

Aural Electrode.— An electrode suitably 



shaped for the therapeutic treatment of 
the ear. 

Aurora. — (1) Luminous sheets, columns, 
arches, or pillars of pale flashing light, 
generally of a reddish color, seen in the 
Northern and Southern heavens. (2) The 
Northern and Southern lights. 

Aurora Australis.— (1) The Southern 
light. (2) A name given to an appear- 
ance in the Southern heavens similar to 
that of the aurora borealis. 

Aurora Borealis. — The Northern light. 

Aurora Glory. — A term proposed for the 
almost constant crown or crowns of light, 
which occupy a nearly fixed position in 
the heavens during the continuance of 
an aurora. 

Aurora Polaris.— A general name for the 
aurora borealis or the aurora australis. 

Auroral. — Of or pertaining to an aurora. 

Auroral Arch. — An arch-like form some- 
times assumed by the auroral light. 

Auroral Bands. — Approximately parallel 
streams of light that are sometimes seen 
during the prevalence of an aurora. 

Auroral Coronse. — Crown-shaped appear- 
ances sometimes assumed by the auroral 
light. 

Auroral Curtain. — A curtain-shaped 
sheet of auroral light. 

Auroral Flashes.— (1) Sudden variations 
in the intensity of the auroral light. 
(2) Intermittent flashes of auroral light. 

Auroral Light. — The light given off by 
an aurora. 

Auroral Storm. — An unusual prevalence 
of auroras. 

Auroral Streams. — Auroral streamers. 

Auroral Streamers.— Flashing columns 
or pillars of light that are emitted from 
portions of the sky during the prevalence 
of an aurora. 

Austral. — Of or pertaining to the South. 

Austral Fluid.— A term formerly em- 
ployed for that magnetic fluid which was 
supposed to exist around or to emanate 
from the austral pole of a magnet. 

Austral Magnetic Pole.— (1) The name 
formerly employed in France for the 
north-seeking pole of a magnet. (Not in 
general use.) (2) That pole of a magnet 
which points to the earth's geographical 
north. (Not in general use.) 

Auto-Car. — (1) An automobile car. (2) 
A car provided with storage batteries. 

Auto-Converter. — (1) A choking coil con- 
nected across a circuit and tapped at va- 
rious points to enable a reduced E. M. F. 



Aut.] 



68' 



[Aut, 



to be obtained. (2) An auto-transformer. 
(3) A choking coil connected to an induc- 
tion motor by a switch in such a manner 
as to facilitate the starting of the motor 
under load. 

Auto-Excitation. — Self- excitation. 

Auto-Exciting.— Self-exciting. 

Autographic Telegraphy.— (1) Fac- 
simile telegraphy. (2) A writing tele- 
graph. 

Auto-Induction. — A word sometimes em- 
ployed instead of self-induction. 

Auto-Kinetic System of Fire Telegra- 
phy. — A system of fire telegraphy in 
which the transmitters are connected in 
series in a pair of circuits, so that, when 
an alarm is being transmitted from one 
a 1 arm point, no other alarm, received at 
the same time, will be transmitted until 
the first has been recorded. 

Automatic Annunciator Drop. — An 
annunciator drop which on the closing of 
a distant circuit falls and holds the cir- 
cuit closed until the drop is raised. 

Automatic Answer-Back. — An auto- 
matic return-signal call-box. 

Automatic Argand Burner.— An Ar- 
gand burner furnished with a device by 
means of which it can be either auto- 
matically lighted or extinguished at a 
distance. 

Automatic Gas Cut-OfF.— A device for 
automatically cutting out the battery 
from an electric gas-lighting circuit, on 
the accidental grounding of the circuit. 

Automatic Guard for Series-Con- 
nected Incandescent Lamps.— (1) 
An automatic cut-out, placed on a series- 
connected incandescent lamp, for the 
purpose of short-circuiting the holder 
should the lamp filament break. (2) A 
film cut-out. 

Automatic Indicating-Grapnel.— A 
grapnel which automatically completes 
the circuit of an electric bell or indicator 
on a cable ship, as soon as the cable is 
hooked. 

Automatic Indicator. — Any automatic 
device for electrically indicating the 
number of times a circuit has been opened 
or closed, thus showing the number of 
times any operation has occurred, which 
has caused the opening or closing of the 
circuit. 

Automatic Indicator for Grapnel.— 
An apparatus employed with a grapnel 
for indicating when the grapnel comes 
off the sea bottom. 

Automatic Inker. — An ink- writing Morse 



recorder which is automatically self- 
starting upon its operation by telegraphic 
currents. 

Automatic Interrupter. — An automatic 
contact-breaker. 

Automatic Locking-Switch. — A com- 
bined key and switch employed in sub- 
marine cables, whereby the switch is 
automatically locked and thus prevented 
from being left for sending, when it 
should be left for receiving, or vice-versa. 

Automatic Make-and-Break.— A device 
whereby the to-and-f ro movements of the 
armature of an electro-magnet are caused 
to automatically make and break its cir- 
cuit. 

Automatic Multiple-Transmitter.— In 

a telegraphic signalling or calling system, 
the means whereby the requisite number 
of spacing and electric impulses for any 
of a number of different calls, is auto- 
matically sent over a line, in order to pro- 
duce a given signal, such for example, in 
a system of police telegraphy, as a call for 
an ambulance, a call for a squad, etc. 

Automatic Oiler. — An oil cup or reservoir 
that automatically spreads oil over the 
bearing of a machine in motion. 

Automatic Overload-Switch for Stor- 
age Battery. — An automatic electro- 
magnetic switch, inserted in the discharg- 
ing circuit of a storage battery, by means 
of which, when the discharging current 
exceeds a certain safe limiting strength, it 
is automatically opened. 

Automatic Paper-Winder.— An appa- 
ratus for carrying and automatically 
winding the paper fillet or strip used on 
telegraphic registers. 

Automatic Photo-Electric Switch.— 
A switch that is automatically opened or 
closed on the exposure of its face to 
differences of illumination. 

Automatic Regulation of Dynamo- 
Electric Machine. — Such a regulation 
of a dynamo-electric machine as will 
automatically preserve constant, either 
the current strength or the potential dif- 
ference at its terminals. 

Automatic Regulation of Motor.— Such 
a regulation of a motor as will maintain 
constant its speed, or its torque. 

Automatic Regulator.— A device for 
securing automatic regulation of a dy- 
namo or motor, as distinguished from 
hand regulation. 

Automatic Repeater. — A telegraphic re- 
peater which is automatically operated, in 
contradistinction to a manual repeater 
which is operated or controlled by hand. 



Aut.] 



688 



[Aut. 



Automatic Rheostat. — An automatic 
variable resistance. 

Automatic Rheotome. — An automatic 
contact-breaker. 

Automatic Ringing - Through. — A 

means by which in junction telephone 
working the attention of the distant ex- 
change can be secured by the act of estab- 
lishing connection at the originating ex- 
change without the necessity of calling up 
the distant exchange after connection 
has been made. 

Automatic Search-Light.— A search- 
light in which a parallel, or slightly 
divergent beam of light, is caused au- 
tomatically to sweep the horizon and thus 
disclose the approach of a torpedo boat or 
other similar danger. 

Automatic Signalling. -- - Telegraphic 
transmission by machine-made contacts as 
distinguished from telegraphic signalling 
by hand. 

Automatic-Call-Box. — A form of tele- 
phone call-box by means of which the 
service of a telephone exchange can be ob- 
tained by a payment made into a box, 
thus dispensing with the services of an 
attendant. 

Automatic Chemical Telegraphy.— 
Automatic telegraphy in which the sig- 
nals are recorded on a fillet or band of 
chemically prepared paper. 

Automatic Circuit-Breaker.— A device 
for automatically opening a circuit when 
the current passing through it is exces- 
sive. 

Automatic Clearing Indicator.— (1) A 

self -restoring drop . ( 2 ) A clearing indica- 
tor at a telephone exchange on a junction 
line, which automatically indicates when 
the conversation has terminated. 

Automatic Contact-Breaker.— A device 
for causing an electric current to rapidly 
make and break its own circuit. 

Automatic Counter.— In railway block- 
signalling, an electro-magnetic device 
for recording and indicating the signals 
of an audible code. 

Automatic Curb-Sender.— In subma- 
rine telegraphy, a transmitter in which 
each signal is curbed automatically ; i. e., 
each signal is followed by one or more 
alternately directed impulses before earth- 
ing, for the purpose of clearing the line 
of its static charge. 

Automatic Cut-in.— Any arrangement 
of parts that will automatically introduce 
a translating device or an electric source 
into a circuit on the occurrence of any 
predetermined event. 



Automatic Cut-Out.— Any arrangement 
of parts that will automatically cut-out 
or remove a translating device or an elec- 
tric source from a circuit on the Occur- 
rence of a predetermined event. 

Automatic Cut-Out for Storage Bat- 
tery. — An automatic electro-magnetic 
switch, inserted into the charging cir- 
cuit of a storage battery, so arranged that 
if the charging current falls below a safe 
limiting strength the charging circuit 
will be opened. 

Automatic Cut-Out for Multiple-Con- 
nected Electro-Receptive Devices. 
— (1) A device for automatically cutting 
an electro-receptive device, such as a 
lamp, out of a circuit. (2) A safety catch 
or safety base. 

Automatic Cut-Out for Series-Con- 
nected Electro-Receptive Devices. 
Means whereby an electro-receptive de- 
vice, such as an arc lamp, is to all intents 
and purposes automatically cut-out of, or 
removed from, a circuit, by means of a 
shunt of low resistance which permits the 
greater part of the current to flow past 
the lamp. 

Automatic Cut-Out of Magneto. — A 
cut-out switch for automatically remov- 
ing the armature of a magneto from the 
telephone circuit by the action of a spring, 
as soon as the handle is released. 

Automatic Drop. — An automatic annun- 
ciator drop. 

Automatic Electric Alarm-Bell.— An 
electric alarm-bell furnished with an 
automatic contact-breaker. 

Automatic Electric Bell.— (1) A trem- 
bling or vibrating bell. (2) An auto- 
matic electric alarm-bell. 

Automatic Electric Gas-Burner. — An 

electric device for both turning on the 
gas and lighting it, and turning the gas off, 
and thus extinguishing the light, by alter- 
nately touching different buttons. 
Automatic Electric Safety System for 
Railroads. — A system for automatically 
preventing the approach of two trains, 
whatever their speed, beyond a pre- 
determined distance from each other. 

Automatic Fire-Alarm. — An instrument 
for automatically telegraphing an alarm 
of fire from any locality on its increase in 
temperature beyond a certain predeter- 
mined point. 

Automatic Fire- Annunciator. — An an- 
nunciator for automatically indicating 
the point from which a fire-alarm has 
been sent. 

Automatic Steam-Whistle, Electric— 



Aut.] 



[Aux. 



A steam- whistle employed in absolute 
block systems for railroads, whereby, 
during fogs or snow-storms, when the 
signals are hidden from view, the loco- 
motive, on passing over a portion of the 
road at a convenient distance from the 
signal, is caused to make a succession of 
electric contacts, whereby a steam whis- 
tle is blown on the moving train. 

Automatic Switch.— (1) A switch which 
is automatically opened or closed on the 
occurrence of certain predetermined 
events. (2) In double-current telegraphy 
an electro-magnetic switch which enables 
the distant station to stop the sending 
operator at the home station. 

Automatic Switch for Incandescent 
Electric Lamps.— (1) A safety fuse or 
safety cut-out. (2) Any switch by means 
of which incandescent lamps can be 
lighted or extinguished at a distance. (3) 
A device for automatically closing the 
circuit of a lamp or lamps on the opening 
of a door, or passage of a barrier. (4) A 
device for automatically opening the cir- 
cuit of a lamp or lamps after the expira- 
tion of a predetermined time or at the 
closing of a door. 

Automatic Telegraph.— A general term 
embracing the apparatus employed in 
automatic or machine telegraphy. 

Automatic Telegraph-Sounder.— A 
form of automatic telegraphic transmit- 
ter. 

Automatic Telegraph-Transmitter. — 
(1) A device for automatically transmit- 
ting signals by means of embossed or per- 
forated slips drawn under suitable con- 
tact devices. (2) A transmitter employed 
in automatic telegraphy for sending pre- 
pared messages. 

Automatic Telegraphy. — A system of 
telegraphy by means of which a tele- 
graphic message is automatically trans- 
mitted over a line by the motion of a pre- 
viously perforated fillet of paper, the 
perforations of which are arranged in the 
order and length required to form the 
characters to be transmitted. 

Automatic Telephone-Exchange.— A 
system of telephony in which the sub- 
scribers are able to secure selective inter- 
communication without the aid of an 
exchange operator. 

Automatic Telephone Hook. — An auto- 
matic telephone switch, operated by hang- 
ing up the telephone used in connection 
with it. 

Automatic Telephone Switch. — (1) A 
device for automatically transferring the 
connection of the main line from the tele- 
44 



phone to the call-bell by the weight of 
the telephone when hung up. (2) A 
switch operated by the act of hanging up 
or taking down a telephone from a hook 
and employed to introduce or remove a 
call-bell from the line. 

Automatic Time Cut-Out.— A device 
which automatically cuts a translating 
device or an electric source from a circuit 
at a certain predetermined time, or after 
the lapse of a predetermined time. 

Automatic Variable Resistance.— A 
resistance the value of which can be auto- 
matically varied. 

Automatically Regulable.— Capable of 
automatic regulation. 

Automatically Regulate.— To regulate 
in an automatic manner. 

Automobile.— (1) Self-movable. (2) Con- 
taining the power necessary for its own 
motion. 

Automobile Carriage.— A horseless car- 
riage. 

Automobile Torpedo. — A torpedo which 
contains the power required for its pro- 
pulsion. 

Automobile Vehicle.— An automobile 
carriage. 

Auto-Reversible Tele-Radiophone . — 

(1) A photophone arranged so that a num- 
ber of telegraphic communications may 
be simultaneously sent either all in the 
same direction, or part in one direction, 
and the remainder in the opposite direc- 
tion. (2) A multiple tele-radiophone. 

Auto-Starter. — (1) A self-starting mech- 
anism. (2) A self -starting ink- writer. 
(3) A self-starting motor. 

Auto-Telephone System. — A system of 
multiple-circuit telephony in which a 
single battery is employed, whereby a 
number of telephone stations can be con- 
nected by a single cable without the use 
of a distributing board, or exchange. 

Auto-Transformer. — A one-coil trans- 
former consisting of a choking coil con- 
nected across a pair of alternating-current 
mains, and so arranged that a current or 
pressure differing from tliat su pplied by 
the mains can be obtained from it by 
tapping it at different points. 

Auxiliary Bus.— A central-station bus- 
bar connected to an auxiliary pressure ; 
i. e., a pressure different from the main- 
station pressure. 

Auxiliary Alarm Telegraph. — In a sys- 
tem of fire-alarm telegraphy, where an 
alarm received in any one circuit is auto- 
matically repeated over all the other cir- 



Ave.] 



690 



[Bac. 



cuits, means whereby the repetition of 
the signals are prevented from interfering 
with the incoming signals of any of the 
other circuits. 
Average Efficiency of Motor.— (1) The 
efficiency of an electric motor based on 
its average or mean load. (2) The ratio 
of all the work that a motor delivers in a 
given time to the electric energy it has 
absorbed in that time. 

Average Electromotive Eorce. — The 
mean electromotive force. 

Average Life of Incandescent Lamp. 
The mean time during which a number 
of incandescent lamps will continue to 
burn without breaking when connected 
with a circuit of given pressure. 

Average Value of Periodic Current 
or E. M. F. — The arithmetical mean 
value of a periodic current or E. M. F., 
with respect to magnitude and without 
respect to sign or direction. 

Avogrado's Hypothesis. — Equal vol- 
umes of different gases measured at the 
same temperature and pressure contain 
the same number of molecules. 

Axes of Co-Ordinates.— A vertical and a 
horizontal line, usually intersecting each 
other at right angles, and called respec- 
tively the axes of ordinates and abscissas, 
from which the ordinates and abscissas 
are measured. 

Axial. — Of or pertaining to an axis. 



Axial Current.— In electro-therapeutics, 
a current flowing in a nerve in the oppo- 
site direction to the normal impulse of 
the nerve. 

Axial Magnet. — A name sometimes given 
to a solenoid with a straight core. 

Axis of Abscissae or Abscissas.— The 
horizontal line in the axes of co-ordinates. 

Axis of Magnetic Needle.— A straight 
line drawn through a magnetic needle, 
and joining its poles. 

Axis of Ordinates.— The vertical line in 
the axes of co-ordinates. 

Azimuth. — In astronomy, the angle sub- 
tended at an observer between the plane 
of an azimuth circle and the plane of the 
meridian. 

Azimuth Circle. — The arc of a great 
circle passing through the zenith, or the 
point of the heavens directly overhead, 
and the nadir, or the point directly be- 
neath. 

Azimuth Compass. — (1) A compass used 
for measuring the horizontal angular dis- 
tance of any distant object from the mag- 
netic meridian. (2) The mariner's com- 
pass. 

Azimuth Telegraph. — On a war-ship a 
telegraph for indicating at any or all 
guns the azimuth of a target. 

Azimuth and Range Telegraph.— On 
a war-ship a combined telegraph to the 
guns of the azimuth and range of a target. 



B 



§S. — A symbol for magnetic intensity, or 
induction density, usually expressed in 
C. G. S. units per normal square centi- 
metre. (Partly International usage. ) 

B. — (1) A symbol for magnetic induction, or 
the amount of flux per normal square 
centimetre of the magnetized material. 
(2) A symbol for susceptance in alter- 
nating-current circuits. 

B. A. Ampere. — The British Association 
ampere in a circuit whose resistance is 
one B. A. ohm under an E. M. F. of 
one B. A. volt. 

B. A. Balance. — A type of balance or 
bridge, originally employed by the British 
Association Committee in duplicating B. 
A. ohms. 

B. A. Ohrn. — (1) The British Association 
ohm. (2) The resistance of a column of 
mercury one square millimetre in area of 
normal cross-section, and 104.9 centi- 
metres in length, at the temperature of 
zero centigrade. 



B. A. U. — A contraction for British Asso- 
ciation unit or ohm. 

B. A. Unit. — The British Association unit 
of resistance or ohm. 

B. S. G. — A contraction for British stand- 
ard gauge. 

B. & S. W. G. — A contraction for Brown 
and Sharpe's wire gauge. 

B. T. U. — (1) A contraction for British 
thermal unit. (2) A contraction for Board 
of Trade unit. 

B. W. G. — A contraction for Birmingham 
wire gauge. 

Back Ampere-Turns. — Ampere-turns on 
a dynamo armature which tend to oppose 
the flux produced by the field magnets. 

Back Electromotive Force.— A term 
sometimes used for counter-electromotive 
force. 

Back Induction. — An induction opposed 
to the field and tending to weaken or 
neutralize it. 



Bac] 



691 



[Bal 



Back Magnetization. — A term some- 
times used for backward or back induc- 
tion. 

Back Magnetization of Armature. — 

Counter-magnetomotive forces acting in 
the main magnetic circuit of the field 
coils, and tending to reduce the useful 
flux passing through the armature. 

Back of Electro-Magnet.— The yoke of 
an electro-magnet. 

Back Pitch. — The backward pitch of the 
armature windings. 

Back Stroke of Lightning.— The return 

stroke of lightning. 

Back Stop of Key. — A stop placed on the 
back of a telegraph key in order to limit 
its motion in the direction of release. 

Back-Turns of Armature. — (1) Those 
turns on an armature whose current 
tends to demagnetize the field. (2) The 
back ampere-turns. 

Backing Metal. — An alloy that is placed 
on the back of the copper shell of an elec- 
trotype in order to stiffen it. 

Backing Pan. — The pan in which the cop- 
per shell of an electrotype is placed in 
order to receive its backing of type 
metal. 

Backward Induction of Dynamo Ar- 
mature. — The component of the arma- 
ture induction that opposes the induction 
of the field magnets. 

Backward Pitch of Armature Wind- 
ings. — A pitch which is always left- 
handed, or counter-clockwise, when re- 
garded from the commutator side. 

Backward Waves. — In a closed circuit 
supplied by a dynamo or other source of 
electromotive force, a wave of potential 
that is assumed to start from the negative 
pole of the dynamo and travel around 
the circuit in the opposite direction to the 
forward wave of positive potential from 
the positive pole of the dynamo. 

Bad Earth. — A term sometimes applied to 
a bad ground, or a connection to earth 
whose electric resistance is comparatively 
high. 

Bain Telegraph Code. — An old form of 
telegraphic alphabet originally employed 
in connection with the Bain printing 
instrument. 

Bain's Chemical Recorder. — An appa- 
ratus for recording the dots and dashes of 
a telegraphic despatch on a sheet of chemi- 
cally prepared paper. 

Bain's Chemical Solution. — Bain's print- 
ing solution. 



Bain's Printing Solution.— (1) The so- 
lution used in Bains chemical recorder. 
(2) A solution of potassium ferro-cyanide 
and water. 

Baking Oven, Electric— An electrically 
heated baking oven. 

Balance Arm. — One of the arms of an 
electric balance. 

Balance Arms.— The arms of an electric 
balance. 

Balance, Electric— A term sometimes 
used for an electric bridge. 

Balance Galvanometer.— A dynamo gal- 
vanometer employed for indicating when 
the pressure of the dynamo is equal to 
the pressure on the bus-bars. 

Balance Indicator. — Any device for indi- 
cating when an electric balance has been 
obtained. 

Balance Indicator of Three-Wire Sys- 
tem. — A device for indicating when a 
balance is obtained between the positive 
and negative leads of a three-wire system 
of distribution. 

Balance of Induction in Cable. — The 
neutralization of induction in a cable by 
the presence of equal and opposite effects. 

Balance of Telegraphic Circuit.— The 
condition of a duplexed telegraph line 
when the home relay ceases to respond to 
the home key. 

Balance Photometer. — A photometer 
based on the decomposition of iodide of 
nitrogen by the action of light. 

Balanced Armature. — (1) An armature 
whose weight is symmetrically distributed 
as regards its axis of rotation. (2) An 
armature that has been so adjusted by 
the addition of weights that its weight is 
symmetrically distributed with reference 
to its axis of rotation. 

Balanced Circuit.— A telephonic, tele- 
graphic, or other circuit which has been 
so erected and adjusted as to be free 
from mutual inductive disturbances from 
neighboring circuits. 

Balanced Load. — A load which is sym- 
metrically divided between two or more 
generating units, as in the three-wire, 
five-wire, multiple, or polyphase systems 
of distribution. 

Balanced Magnetic Circuits of Arma- 
ture. — The magnetic circuits traversing 
the armature of a dynamo-electric ma- 
chine through which the magnetic fluxes 
produced by the field are symmetrically 
distributed in regard to flux density, total 
flux, and geometrical distribution. 

Balanced Metallic Circuit.— A metallic 



BaL] 



692 



[Ban. 



circuit, the two sides of which have sim- 
ilar electric properties. 

Balanced Polyphase System.— A poly- 
phase system all the branches of which 
are symmetrical in regard to their electro- 
motive force, current, and phase. 

Balanced Reaction Coil. — A coil em- 
ployed in a system of distribution by 
alternating-current transformers for 
maintaining a constant current in the sec- 
ondary circuit or circuits despite changes 
in the load placed therein. 

Balanced Resistance. — A resistance so 
placed in a bridge or balance as to be bal- 
anced by the remaining resistances in the 
bridge. 

Balanced System. — An electric system 
of distribution or communication which 
is so adjusted as to be free from mutual 
inductive disturbances from neighboring 
systems. 

Balancing.— Rendering a metallic tele- 
phone circuit free from inductive dis- 
turbances from other lines. 

Balancing Coil of Armature. — An aux- 
iliary field-winding in series with an 
armature, and having its magnetomotive 
force equal and opposite to that of the 
armature current, so that their total mag- 
netic effect upon the field is zero, and the 
field flux remains unchanged at all loads. 

Balancing of Telegraph Line.— In du- 
plex or quadruplex telegraphy the opera- 
tion of adjusting the balance between 
the real and artificial lines, whereby the 
home signals do not affect the receiving 
instruments. 

Balancing Relay. — A differentially wound 
relay. , 

Balancing Resistance for Dynamos.— 
A regulating resistance that possesses a 
sufficient range to balance one dynamo 
against another with which it is operated 
in parallel. 

Balancing Thermopile. — (1) A double 
thermopile. (2) A differential thermo- 
pile. 

Balancing Wire or Conductor.— A term 
sometimes employed for the neutral wire 
or conductor of a three- wire system. 

Balata. — An insulating material. 

Ball Lightning. — A name sometimes 
given to globular lightning. 

Ballistic Curve.— The curve actually de- 
scribed by a projectile thrown through 
the air in any other than a vertical direc- 
tion. 

Ballistic Galvanometer.— (1) A galvano- 
meter designed to measure the total quan- 



tity of electricity in a discharge lasting for 
a brief interval, as, for example, the cur- 
rent caused by the discharge of a conden- 
ser. (2) A galvanometer, in which the 
movable part is as little damped as pos- 
sible, suitable for measuring electric 
charges or discharges, and usually ad- 
justed to have a long period of vibration 
or slow swing. 

Ballistic Pendulum.— A pendulum with 
a heavy bob employed to determine the 
velocity of a projectile fired into it. 

Balloon Buoy. — A buoy used in submarine 
cable work somewhat resembling a bal- 
loon in shape. 

Balloon, Electric— (1) A balloon or air- 
ship provided with electric power so as to 
be capable of being started or moved 
against the direction of the wind. (2) An 
electrically dirigible balloon. 

Balloon Signalling for Military Pur- 
poses. — Transmitting intelligence, as of 
the movements of an enemy's army, 
from observations made in balloons by 
means of telephone circuits directly 
connected with the balloons. 

Band Arc Lamp. — An arc lamp in which 
the feeding of the carbons is effected 
through the movements of a band of cop- 
per, which carries the upper carbon holder 
and conducts the current into the arc. 

Band or Banded Spectrum.— The con- 
dition assumed by the spectrum of a com- 
pressed gas or vapor when sufficiently 
heated, in which the lines of the ordinary 
spectrum are broadened into bands. 

Banjo. — A wooden drum fastened upon a 
kite-shaped board, employed for tighten- 
ing a pole-strung telephone or telegraph 
wire. 

Bank Board. — A small switchboard con- 
taining a bank of lamps used in an alter- 
nating-current series-incandescent system 
of street lighting, and usually supplied 
with an ammeter and switch for intro- 
ducing one or more relief lamps. 

Bank of Lamps. — A group of electric 
lamps collected together in a common 
structure, usually for the purpose of ob- 
taining a load. 

Bank of Transformers. — A group of 
transformers collected together in a com- 
mon structure usually either for the pur- 
pose of obtaining a load, or for readily 
varying the pressure. 

Banked Battery. — A term sometimes 
applied to a battery from which a num- 
ber of separate circuits are supplied with 
current. 

Banking Transformers.— (1) Grouping 



Bar.] 



69[ 



[Bat. 



transformers in a common structure either 
for the purpose of obtaining a load, or 
for readily varying the pressure. (2) As- 
sociating transformers in parallel. (3) 
Associating transformers in series. 

Bar Armature. — An armature whose con- 
ductors are formed of bars. 

Bar Electro-Magnet.— An electro-mag- 
net, the core of which is in the form of a 
straight bar or rod. 

Bar Windings. — Armature windings 
composed of copper bars. 

Bar- Wound Armature. — An armature 
in which the conductors have the form of 
bars. 

Barad. — (1) A unit of intensity of pressure. 
(2) A dyne per square centimetre. 

Bare Arc-Light Carbons. — Arc-light car- 
bons or pencils unprovided with an elec- 
tro-plating of copper or other conducting 
metal. 

Bare Carbons. — Arc-light or battery car- 
bons, unprovided with an electro-plating 
of copper. 

Barker's Wheel. — An early form of reac- 
tion water wheel. 

Barlow's Wheel. — A wheel or disc of 
metal, capable of rotation on an axis, 
that is set into rotation when placed be- 
tween the poles of magnets and traversed 
between its centre and circumference by 
a current of electricity. 

Barometer. — An apparatus for measuring 
the atmospheric pressure. 

Barometric Column.— A column, usually 
of mercury, approximately 30 inches in 
vertical height, sustained in a barometer 
or other tube by the atmospheric pres- 
sure. 

Barometric Gradient.— The drop or fall 
of atmospheric pressure per unit of dis- 
tance as measured between two adjacent 
isobars. 

Barrel of Jack. — In telephony a conduct- 
ing cylinder in a jack for making con- 
tact with the sleeve of a plug. 

Barrow-Reel.— A reel supported on a 
barrow for convenience in paying out an 
overhead conductor during its installa- 
tion. 

Bar Winding of Armature.— A winding 
consisting of insulated copper bars con- 
nected at their extremities. 

Base Frame of Generator.— The frame 
on which a generator is supported. 

Basis Metal of Electro-Plating.— The 
metal on whose surface an electro-plating 
is to be deposited. 



Batch Working. — In telegraphy a method 
of operating consisting in sending a 
plurality of messages in one direction over 
a line, and then a plurality of messages 
in the opposite direction, as distinguished 
from up-and-down working. 

Bathometer.— An instrument for obtain- 
ing deep-sea soundings without the use 
of a sounding-line. 

Battery. — A name frequently used for an 
electric-battery. 

Battery.— (1) To place a storage battery 
on a storage-battery car. (2) To supply 
a battery to a station or circuit. 

Battery Car.— A storage-battery car. 

Battery, Electric— A general name ap- 
plied to the combination, as a single 
source, of a number of separate electric 
sources. 

Battery Gauge.— A form of portable gal- 
vanometer suitable for ordinary battery 
testing work. 

Battery Jar. — A jar provided for holding 
the electrolyte of each of the separate 
cells of a primary or secondary battery. 

Battery Lamp. — An incandescent lamp 
of such low voltage as to be readily oper- 
ated by the ordinary voltage of a battery 
of a few series-connected cells. 

Battery Motor. — Am electric motor so 
wound as to be properly operated by the 
comparatively low electromotive force of 
an ordinary battery. 

Battery of Alternators. — A number of 
separate alternators so connected as to be 
capable of acting as a single alternator. 

Battery of Generators.— A number of 
separate generators so connected as to be 
capable of acting as a single generator. 

Battery Pole-Changer.— A form of trans- 
mitter employed in duplex telegraphy for 
readily reversing the direction of the 
main battery so as to send signals to the 
line. 

Battery Solution. — The exciting liquid 
or electrolyte of a primary or secondary 
cell. 

Battery Stand. — The insulating or insu- 
lated stand provided for holding a pri- 
mary or secondary battery. 

Battery Syringe. — A syringe for either re- 
moving the acid or spent liquids from a 
voltaic battery, or for introducing fresh 
liquid. 

Battery System for Electric Railroads. 
A system for the propulsion of street cars 
by means of storage batteries. 

Battery Transformer. — A step-up trans- 
former so wound as to be readily operated 



Bat.] 



694 



[Bic. 



by a primary battery of a few series-con- 
nected cells. 

Battle Circuit. — A circuit on a warship, 
connected with the conning tower and 
provided for use during action. 

Battle Lantern. — A form of safety lantern 
for use in action on board a warship. 

Bead Areometer. — A form of hydrometer 
suitable for rapidly testing the density of 
the exciting liquid in a storage cell. 

Bead Chain. — A chain of metallic beads 
sometimes employed for the pull in a 
pendant electric-burner. 

Bead Hydrometer.— A bead areometer. 

Bead Lightning. — A form of lightning 
discharge in which the flashes produce a 
discontinuous line of light possessing a 
bead-like appearance. 

Beaded Cable. — A form of cable employed 
for high-tension transmission, provided 
with a sheathing of strung porcelain 
beads. 

Bec-Carcel. — The carcel, r~ French photo- 
metric standard. 

Becquerel Radiation. — An invisible ra- 
diation, discovered by Becquerel, emitted 
by certain salts, especially those of ura- 
nium, capable both of penetrating many 
media opaque to ordinary light, and 
affecting a photographic plate. 

Becquerel Rays. — Becquerel radiation. 

Bed-Plate of Dynamo-Electric Ma- 
chine. — The base or frame of a dynamo- 
electric machine. 

Bega. — A prefix for a billion, one thousand 
million, or 10 9 . 

Begadyne. — One billion dynes, or roughly, 
the earth's gravitational force on a ton 
of matter. 

Beg-Erg. — One billion ergs ; or, 73.7 foot- 
pounds, approximately. 

Beg-Ohm. — One billion ohms, or one thou- 
sand megohms. 

Begohm Galvanometer. — A galvano- 
meter which gives unit deflection through 
a resistance of one begohm in circuit with 
one volt. 

Bell Box. — In telephony a box containing 
or designed to contain a telephone bell. 

Bell Hanger's Joint. — A careless form of 
telegraphic or telephonic joint in which 
the ends of the wires are merely looped 
into each other. 

Bell Month of Cable Tank.— A circular 
aperture provided in the top of a cable 
tank, through which a cable is led into 
or taken out of the tank. 



Bell Pull, Electric— Any circuit-closing 
device operated by a pull. 

Bell-Shaped Magnet.— A modified form 
of horse-shoe magnet in the form of a 
split tube, and in which the approached 
poles are semi circular in shape. 

Bell Switch. — A switch connected with a 
telephone alarm-bell for the purpose of 
throwing it in or out of circuit. 

Belt Circuit. — A series lighting circuit 
extending in the form of a wide loop, 
belt, or circle, as opposed to a circuit 
formed of two closely associated parallel 
wires. 

Belt-Driven Generator.— A generator 
driven by means of belting, as distin- 
guished from a direct-driven or rope- 
driven generator. 

Belt-Driving or Coupling.— Driving or 

coupling by means of belts. 

Belt, Electric— A belt suitably shaped 
so as to be capable of being worn on the 
body, consisting either of imaginary or 
real voltaic or thermo-electric couples, 
and employed for its alleged therapeutic 
effects. 

Belt of Current.— The total current gen- 
erated by an armature at any moment, 
assumed as making a single turn around 
the armature. 

Belt Speed.— The velocity of translation 
or linear speed of a belt in the transmission 
of power. 

Bessel's Functions.— A series of mathe- 
matical functions often connected with 
problems in electricity and satisfying a 
certain relation first enunciated by Bessel 
in connection with an astronomical prob- 
lem. 

Bias of Relay Tongue. — A term em- 
ployed to signify such an adjustment of 
a polarized relay that on the cessation 
of a working current the relay tongue 
shall always rest against the insulated 
contact, and not against the other con- 
tact, or vice versa. 

Bichromate Voltaic Cell.— A zinc-car- 
bon couple employed with a solution of 
bichromate of potash and sulphuric acid 
in water. ' 

Bicro. — A prefix for one billionth, one 
thousand millionth, or 10- 9 . 

Bicro-Ampere.— The billionth of an am- 
pere. 

Bicro-Farad.— The billionth of a farad. 
Biero-Henry.— The billionth of a henry. 
Bicron.— A unit of length equal to the 

billionth of a metre, and indicated by the 

symbol juju. 



Bic] 



695 



[Bi-T. 



Bicycle Car.— An electrically propelled 
car whose weight rests on a single rail, 
and which is kept in position by a guide 
rail supported vertically above the main 
rail. 

Bicycle Electric Lamp. — An incandes- 
cent lamp suitable for use on a bicycle 
and usually operated by a small voltaic 
battery. 

Bifilar Control of Galvanometer 
Needle. — The control of a galvanometer 
needle whereby it returns to its position 
of rest, on the removal of the deviating 
force, by the operation of a bifilar sus- 
pension. 

Bifllar Suspension.— Suspension by 
means of parallel vertical wires or fibres 
as distinguished from suspension by a 
single wire or fibre. 

Bifilar Winding. — The method of wind- 
ing employed in resistance coils to obviate 
the effects of self-induction, in which the 
wire, instead of being wound in one contin- 
uous length, is doubled on itself before 
winding. 

Bight of Cable. — A single loop or bend 
of cable. 

Bimetallic Accumulator. — An accumu- 
lator or storage cell whose positive and 
negative plates are formed respectively 
of two different metals. 

Bimetallic Helix. — A compound helix of 
two metals of different expansibilities, 
such as copper and steel, firmly riveted 
or soldered together, so that the helix is 
twisted or moved in one direction by un- 
equal expansion, and in the opposite direc- 
tion by unequal contraction. 

Bimetallic Thermometer.— A thermom- 
eter whose operation depends on the ex- 
pansion and contraction of a bimetallic 
helix. 

Bimetallic Thermostat.— A form of ther- 
mostat employed for opening or closing a 
circuit by the expansions and contractions 
of a bimetallic arc-shaped spring. 

Bimetallic Wire. — A compound tele- 
phone or telegraph wire consisting of a 
steel core and a copper envelope, suitable 
for long-span overhead-construction. 

Binary Compound. — A compound 
formed by the union of two different 
elements. 

Binding Coils. — Coils of wire, wound on 
the outside of the armature coils and at 
right angles thereto, to prevent the loosen- 
ing of the armature coils during rotation 
by centrifugal force. 

Binding Post. — A metallic binding screw, 
rigidly fixed to some apparatus or support, 



and employed for conveniently making 
firm electric connections. 
Binding Screw. — A name sometimes ap- 
plied to a binding post. 

Binding Wire for Telegraph Lines.— 

(1) The wire employed for securing a tele- 
graph wire to the insulator which sup- 
ports it. (2) A tie wire. 

Binnacle Compass.— A compass on board 
ship placed in a binnacle for use in steer- 
ing or directing the vessel. 

Biograph. — An apparatus for obtaining on 
a screen, from a rapid succession of suit- 
able pictures, the appearance of the actual 
movements of natural objects. 

Bioplasm.— (1) Any form of living matter 
possessing the power of reproduction. 

(2) Living protoplasm. 
Bioscope.— A biograph. 

Bioscopy, Electric. — The determination 
of the presence of life or death by the 
passage of electricity through the nerves 
or muscles. 

Bipolar. — Having two poles. 

Bipolar Armature. — An armature suit- 
able for use in a bipolar field. 

Bipolar Armature-Winding.— Any ar- 
mature winding suitable for use in a 
bipolar field. 

Bipolar Bath. — An electro-therapeutic 
bath, the current supplied to which enters 
at one part of the bath-tub and leaves 
at another. 

Bipolar Dynamo-Electric Machine.— 
A dynamo-electric machine with a bi- 
polar field. 

Bipolar Generator. — A bipolar dynamo- 
electric machine. 

Bipolar Magnetic Field.— A magnetic 
field formed by two opposite magnetic 
poles. 

Bird Cage, Electric. — A bird-cage-shaped 
wire screen employed by Hertz in his in- 
vestigations on the propagation of electro- 
magnetic waves for screening the spark 
micrometer. 

Bird Cage. — In submarine cable-work, a 
mechanical distortion of the sheathing 
in which the wires are locally bulged out- 
wards leaving the serving or core visible 
or exposed. 

Birmingham Wire Gauge. — An En- 
glish wire gauge. 

Bismuth Spiral. — A flat spiral of bismuth 
wire employed for the measurement of 
strong magnetic fields. 

Bi-Telephone. — A term sometimes ap- 
plied to a double telephone receiver ar- 



Biv.] 



696 



[Bol 



ranged so as to permit the ready applica- 
tion of both ears of the listener to the 
receiving instruments. 

Bivalent. — (1) Possessing an atomicity or 
valency of two. (2) Divalent. 

Bitite. — A variety of insulating material. 

Black Electro-Metallurgical Deposit. 
A dark electro-metallurgical deposit that 
is thrown down from the metal in a plat- 
ing bath when too strong a current is 
employed. 

Black Lead. — Plumbago or graphite. 

Black Leading Machine for Electro- 
Types. — A machine for covering the 
printing surface of the wax impression 
employed in electro-typing with an elec- 
trically conducting surface of black lead. 

Black Light. — Non-luminous radiation. 

Blake Telephone Transmitter.— A 

form of carbon telephone transmitter. 

Blank Panel. — A panel on a switchboard 
provided for the support of extra circuit 
connections or instruments. 

Blasting, Electric. — The electric ignition 
of powder or other explosive material in 
a blast. 

Blavier's Formulae.— The formulae em- 
ployed in the Blavier test. 

Blavier's Test. — A test introduced by 
Blavier, for localizing a single fault in a 
single telegraph line or conductor, by 
measuring the resistance at one end of 
the line, when the other end is succes- 
sively freed and earthed. 

Bleaching, Electric— A bleaching pro- 
cess in which the bleaching agents are 
liberated as required by electrolytic de- 
composition. 

Block. — To stop or check by means of a 
block system. 

Block-Facing. — In a system of electric 
distribution mains a section of conductors 
extending in front of a city block-facing. 

Block System for Railroads.— A sys- 
tem for avoiding the collision of moving 
railroad trains, by dividing the road into 
a number of separate blocks or sections of 
a given length, and so maintaining tele- 
graphic communication between towers 
located at the ends of each of such blocks, 
as to prevent, by the display of suitable 
signals, more than one train or engine 
from being on the same block at the same 
time. 

Block Wire. — The line or wire employed 
in block systems for railroads connecting 
each block tower with the next tower on 
each side of it. 



Blooms. — Masses of wrought or cast metal, 
generally rectangular in shape and ap- 
proximately six inches square and three 
or four feet in length, from which wires 
are obtained by rolling. 

Blow. — To melt or fuse a safety fuse. 

Blow-Pipe, Electric— A blow-pipe in 
which the air-blast is obtained by a con- 
vective electric discharge. 

Blower, Electric. — An electrically driven 
blower. 

Blowing a Fuse.— The fusion or volatili- 
zation of a fuse wire or safety strip by 
the current passing through it. 

Blowing Point of Fuse.— The current 
strength at which a fuse blows or melts. 

Blue Magnetic Pole.— A term sometimes 
employed for the south-seeking magnetic 
pole. 

Bluestone Gravity Cell.— A voltaic cell 
consisting of a zinc-copper couple whose 
elements are immersed respectively in 
electrolytes of zinc sulphate and copper 
sulphate. 

Board of Trade Unit.— (1) A unit of elec- 
tric supply, or the energy contained in a 
current of 1,000 amperes flowing for one 
hour under a pressure of one volt. (2) A 
kilowatt-hour. 

Boat, Electric— An electrically propelled 
boat. 

Bobbed. — A word employed to character- 
ize a surface that has been polished by 
the action of a bob. 

Bobbin, Electric— A coil of insulated 
wire suitable for the passage of an elec- 
tric current for any purpose, as, for ex- 
ample, energizing an electro-magnet. 

Body-Protector, Electric— A device for 
protecting the human body against the 
accidental passage through it of an electric 
discharge. 

Boiler-Feed, Electric— A device for 
electrically opening a boiler-feed appa- 
ratus when the water in the. boiler falls 
to a certain predetermined point. 

Boiling of Secondary or Storage Cell. 

A term sometimes applied to the gassing 

of a storage cell. 
Bole. — A unit of momentum, proposed by 

the British Association, equal to one 

gramme-kine. 
Bolognian Stone. — A name formerlygiven 

to a calcareous substance that becomes 

phosphorescent on exposure to light. 

Bolometer. — (1) An apparatus for electri- 
cally measuring small differences of 
temperature. (2) A fine wire or thin strip 



Bol.] 



697 



[Bra. 



of metal whose resistance is altered by 
incident radiant energy. 

Bolometric Spectrum. — The luminous 
and non-luminous spectrum obtained by 
the use of a rock-salt prism, or a diffraction 
grating, for the measurement of radia- 
tion in the bolometric spectrometer. 

Bole-metric Spectrometer.— A spectro- 
meter designed for the measurement of 
radiation, luminous or otherwise. 

Bolt. — A lightning discharge. 

Bombardment, Electric— M o 1 e c u 1 a r 
bombardment. 

Bombardment Incandescent Lamp, 
Electric. — An electric lamp in which re- 
fractory material is rendered incandes- 
cent by molecular bombardment produced 
by the passage of an electric discharge 
through a rarefied space. 

Bonded Rails. — In any electric system 
where the rails are used as a part of the 
circuit, as in a trolley system, rails con- 
nected at their joints by suitable bonds 
for the purpose of bringing them into 
good electric contact with one another. 

Bonding Resistance of Rail. — The resist- 
ance offered in a rail circuit at the 
bonded joints. 

Bonsalite. — An insulating substance. 

Bony Current. — The electric current re- 
sulting from the difference of potential 
existing between the different parts of a 
bone in a recently killed animal. 

Booster. — A dynamo, inserted in a special 
feeder or group of feeders in a 'distribu- 
tion system, for the purpose of raising the 
pressure of that feeder or group of feed- 
ers, above that of the rest of the system. 

Boreal Fluid. — A term formerly applied 
to the fluid that was supposed to exist 
around, or to emanate from, the boreal 
pole of a magnet. 

Boring, Electric. — Forming holes in 
metals or minerals by the heat of the 
voltaic arc. 

Bot. — A contraction sometimes used for 
Board of Trade unit of electric supply, or 
the kilowatt-hour. 

Boucherize. — To subject to the boucher- 
izing process. 

Boucherizing. — A process for preserving 
wooden telegraph poles, or railroad sleep- 
ers, by injecting a solution of copper sul- 
phate' into tlie pores of the wood. 

Bougie-Decimale. — (1) The standard 
French candle. (2) A standard of lumi- 
nous intensity equal to the l-20th of that 
of the Violle molten-platinum standard. 

Bougie-Metre. — A unit of illumination 



equal to the normal illumination from 
a bougie-decimale at the distance of one 
metre, sometimes called a lux. 

Bound Charge. — The condition of a charge 
on a conductor placed near another con- 
ductor, but separated from it by a me- 
dium through which electrostatic induc- 
tion can take place. 

Bow Gear.— The gear placed at the bow of 
a cable ship for the ready handling of a 
cable or the ropes used in cable work. 

Box Balance. — A box form of electric 
bridge. 

Box Bridge. — A commercial form of elec- 
tric bridge or balance in which both the 
arms of the bridge and the known resist- 
ances consist of standardized resistance 
coils placed in a suitable box. 

Box-Sounding Relay.— A relay whose 
magnet is surrounded by a resonant case 
of wood, for the purpose of increasing the 
intensity of the sounds made by the ar- 
mature of the magnet. 

Boxing the Compass. —Naming consec- 
utively all the different points or rhumbs 
of a compass from any one of them. 

Bracket-Arm. — An arm supported by a 
bracket for carrying a line insulator. 

Bracket- Arm Hanger. — A hanger for an 
overhead trolley line supported on a 
bracket arm. 

Bracket Pole. — In a system of overhead 
"wires, a pole employed for the support 
of the brackets provided for the suspen- 
sion of the overhead wires or conductors. 

Bracket Suspension-Ear. — A trolley ear 
supported on a bracket arm, designed for 
the suspension of an overhead trolley 
wire. 

Brake Arm. — An arm or lever connected 
with the brake shoe, and by which the 
brake power is applied. 

Brake Disc. — An electro-magnet in the 
form of a disc, employed in an electric 
street-car brake. 

Brake Handle. — A handle projecting 
above the dasher of a car for the opera- 
tion of the handbrake mechanism. 

Brake Shoe. — A mass of metal whose out- 
line conforms to the tread of a car wheel, 
which is pressed against the circumfer- 
ence of the wheel on the operation of 
the brake mechanism, for the purpose of 
stopping the car. 

Braided Wire. — A wire covered with a 
braiding of insulating material. 

Branch.— (t) In a system of parallel distri- 
bution, any conductor from which outlets 



Bra.] 



698 



[Bre. 



are taken or taps made. (2) One of the 
divisions of a divided conductor. 

Branches.— (1) Conductors connected to 
the submains or supply conductors in a 
system of incandescent lighting. (2) 
Wires tapped to mains. 

Branch Block. — A porcelain block pro- 
vided with suitable grooves in which the 
terminals or conductors are placed for 
connecting a pair of branch wires to the 
mains. 

Branch Box. — A box containing a branch 
block. 

Branch Circuits. — (1) Additional circuits 
provided at points of a circuit where the 
current branches or divides, part of the 
current flowing through the branch, and 
the remainder flowing through the origi- 
nal circuit. (2) A shunt circuit. 

Branch Conductor. — (1) A conductor 
placed in a branch or shunt circuit. 
(2) A smaller or sub-conductor tapping a 
main. 

Branch Coupling Box.— In a system of 
street mains a coupling box suitable for 
connecting a house service connection 
with the incandescent mains supplying 
the house. 

Branch Cut-Out. — A safety fuse or cut- 
out, inserted between a pair of branch 
wires and the mains supplying them. 

Branch Fuse. — A branch cut-out or safety 
fuse. 

Branch of Multiple Circuit. — Any of 
the separate circuits that are connected 
between the mains in a multiple circuit. 

Branch Point of Circuit.— Any point of 
a circuit from which a branch is taken 
off. 

Branch-Wire Terminal Telephone 
Switchboard. — A three-wire multiple 
switchboard for a telephone in which the 
jacks for any one subscriber are connected 
in successive panels in parallel instead of 
in series. 

Branched Magnetic Circuit.— A mag- 
netic circuit in which the flux sub- 
divides into a number of separate mag- 
netic circuits. 

Branched Series. — A term sometimes em- 
ployed for series-multiple. 

Branching Boards. — Multiple telephone 
switchboards connected on the branching 
or multiple system. 

Branching Telephone System.— (1) A 
system of multiple telephone switchboards 
employing the branching or three-wire 
switchboard. (2) A system of multiple 
telephone switchboard in which the vari- 



ous jacks on one line are connected in 
parallel instead of in series. 

Branding, Electric. — The process where- 
by a branding tool is heated to incan- 
descence by an electric current instead 
of by ordinary means. 

Bread-and-Butter Cable. — A name 
given to a form of light submarine cable 
in which the sheathing consists alter- 
nately of yarns and wires. 

Breadth Coefficient of Armature Coil. 
The ratio of the effective electromotive 
force induced in an armature coil to the 
effective electromotive force which would 
be induced if the coil had no breadth ; i. e. , 
if all its wire could be compressed into 
the space occupied by a single turn. 

Breadth of Coil. — The angular distance to 
which a coil extends circumferentially 
around an armature core. 

Break. — Any lack of conducting continuity 
in a circuit. 

Break-Down Switch. — A panel switch 
employed in small three-wire systems, 
for connecting the positive and negative 
bus-bars so as to convert the system into 
a two-wire system, and thus, in case of 
a break-down, to permit the system to 
be supplied with current from a single 
dynamo. 

Break-Induced Current.— (1) The cur- 
rent induced in an active circuit by 
breaking or opening that circuit. (2) The 
current induced in a secondary circuit on 
the breaking of the circuit of the pri- 
mary. 

Break Key .— A key which opens or breaks 
the circuit when depressed. 

Break Shock. — A term sometimes em- 
ployed in electro-therapeutics for the 
physiological shock produced on the open- 
ing or breaking of an electric circuit. 

Break Signal. — In telegraphy a name 
given to the signal which separates the 
preamble from the text of a message, or 
the text from the signature. 

Breaking Capacity of Switch.— The 

strength of current which can be safely 
and effectively interrupted by a switch, 
as distinguished from the carrying capac- 
ity of the same. 

Breaking Down of Dielectric. — Such a 
weakening of a dielectric subjected to 
electric pressure as permits disruptive 
discharges to pass through its substance. 

Breaking Down of Insulation. —The 
failure of an insulating material, as evi- 
denced by the disruptive passage of an 
electric discharge through it. 



Bre.] 



699 



[Br 



Breaking In.— (1) An interruption in the 
sending of a telegraphic despatch by an 
intermediate operator who endeavors to 
simultaneously use the line. (2) Introduc- 
ing a key into a telegraph circuit by open- _ 
ing its switch. (3) Interrupting the con- 
tinuity of a circuit. 

Breaking the Primary. — Opening or 
breaking the circuit of the primary of an 
induction coil or transformer. 

Breaking Weight of "Wire.— The weight 
required to be hung on the end of a wire 
in order to break it. 

Breast Plate. — The breast support for the 
microphone transmitter of a central 
telephone station operator. 

Breast Telephone Transmitter. — A 
telephone transmitter supported for con- 
venience on a plate placed on the breast 
of the operator. 

Breath Figures, Electric. — Faint figures 
of condensed vapor produced by electrify- 
ing a coin or other conducting object, 
placing it momentarily on the surface of 
a clean, bright, glass sheet, and then 
breathing gently on the spot where the 
coin was placed. 

Breeze, Electric. — A brush discharge em- 
ployed in electro-therapeutics. 

Breguet's Manipulator. — A sending in- 
strument employed by Breguet in his 
system of step-by-step, or dial telegraphy. 

" Bridge." — A word sometimes employed 
for multiple-arc. 

Bridge Arms. — The arms of an electric 
bridge or balance. 

Bridge Balance of Telegraph Line.— 
Such a balance of a duplexed telegraph 
line, obtained by an electric bridge, in 
which the home relay ceases to respond 
to the home key. 

Bridge Duplex. — The bridge method of 
duplex telegraphy, as distinguished from 
the differential method. 

Bridge, Electric— (1) A device whereby 
an unknown electric resistance is readily 
measured. (2) A device for measuring 
an unknown resistance by comparison 
with two fixed resistances and an adjust- 
able resistance. 

Bridge Method of Duplex Teleg- 
raphy.— (1) A system whereby two 
telegraphic messages can be simultane- 
ously transmitted over a single wire in 
opposite directions, when a bridge balance 
of the line has been obtained. (2) A sys- 
tem of duplex telegraphy by means of a 
single-bridge duplex-system. 

Bridge of a Fuse.— A small gap at a fuse 



in a metallic circuit filled with a semi- 
conducting compound in which heat is 
developed by a current. 

Bridge System of Quadruplex Teleg- 
raphy. — A system of quadruplex telegra- 
phy by means of a bridge duplex system. 

Bridges. — Heavy copper wires suitably 
shaped for connecting a dynamo-electric 
machine in an incandescent lighting sta- 
tion to the bus-bars. 

Bridge-Wire.— The wire in a Wheat- 
stone's Bridge in which the galvanometer 
is inserted. 

Bridge with Secondary Conductors. 
A form of Wheatstone bridge employ- 
ing an additional pair of resistances, arid 
suitable for measuring very low resist- 
ances. 

Bridging Bell.— A polarized electric bell 
permanently connected across the circuit 
employed in the bridging-bell system of 
telephony. 

Bridging-Bell Telephone System.— A 
system of telephone communication in 
which the call bells are placed in multiple- 
arc, permanently bridging the two line 
conductors of metallic circuits, or legged 
to the ground in grounded circuits, so 
that, when a call is sent out, every bell 
in the line rings, the particular station 
needed being indicated by a suitable code 
of signals. 

Bridging Coils. — In telephony, coils which 
are connected across a telephone circuit, 
as distinguished from coils placed in 
series in the circuit. 

Bridging Indicator. — In telephony, an 
indicator connected in shunt across a 
circuit instead of in series. 

Bridging Belay. — In telephony or tele- 
graphy, a relay which is connected in 
shunt across a circuit instead of in series. 

Bridle Chain. — In submarine cable work, 
the chain on a buoy which is connected 
to the buoy rope, and by which the buoy 
rope may be picked up, when the buoy 
is released at the slip chain. 

Bridle Wires. — (1) Wires connecting the 
separate line wires with a cable box or 
tower. (2) Wires for looping a telegraph 
station into a line or lines. 

Bright Deposit. — In the electro-plating of 
silver a bright surface of deposited metal 
produced by a special final process in the 
plating. 

Bright Dipping.— Cleansing a metal sur- 
face by dipping it in acid liquids for the 
purpose of ensuring a bright electro- 
metallurgical coating. 



Bri.] 



700 



[Bui. 



Bright Dipping Liquid.— The liquid em- 
ployed in bright dipping. 

Brilliancy of Light.— (1) The brightness 
of a luminous source. (2) The quantity 
of light that is emitted normally from 
unit surface of a luminous source. (3) 
The intrinsic intensity of a luminous 
source. 

Britannia Joint. — A telegraphic or tele- 
phonic joint in which the ends of the 
wires are laid side-by-side, bound to- 
gether, and subsequently soldered. 

British Association Unit.— A term for- 
merly applied to the British Association 
unit of resistance or ohm. 

Broiler, Electric— An electrically heated 
broiler. 

Broken Circuit.— (1) An open circuit. 
(2) A circuit whose electric continuity 
has been disturbed, and through which 
the current has, therefore, ceased to pass. 

Brother-in-Law. — A bell whose sound is 
the same as that of the car indicator, con- 
cealed by a dishonest conductor for the 
purpose of avoiding ringing the bell of 
the car indicator when a fare has been 
collected. 

Brush-and-Spray Discharge.-A stream- 
ing form of high-potential discharge pos- 
sessing the appearance of a spray of 
silvery white sparks, or of a branch of thin 
silvery sheets around a powerful brush, 
obtained by increasing the frequency of 
the alternations. 

Brush Contact-Surface.— (1) That portion 
of a commutator surface which is in con- 
tact with the brushes at any moment of 
time. (2) The surface area of a brush 
applied to a contact surface. 

Brush Discharge.— The faintly luminous 
discharge which takes place from a 
positively charged pointed conductor. 

Brush Electrode.— A conducting brush- 
ghaped electrode employed in electro- 
therapeutic treatment. 

Brush-Holder Cable.— A stranded con- 
ductor or cable employed in a dynamo 
or motor for direct connection to the 
brushes. 

Brush Holders for Dynamo-Electric 
Machine. — Devices for supporting the 
collecting brushes of a dynamo-electric 
machine. 

Brush Pressure. — (1) The electric pressure 
at the brushes of a dynamo-electric ma- 
chine. (2) Mechanical pressure on a 
brush. 

Brush Rocker. — In a dynamo or motor 
any device for shifting the position of the 
brushes on the commutator cylinder. 



Brush Shifting Device.— A modified 
form of brush rocker. 

Brushes of Dynamo-Electric Ma- 
chines.— Strips of metal, bundles of wire 
or wire gauze, slit plates of metal, or 
plates of carbon, that bear on the com- 
mutator cylinder of a dynamo, and carry 
off the current generated. 

B-Side of Quadruplex Table.— That 

side of a quadruplex table which is 
worked by means of strengthened cur- 
rents. 

Bucking. — A term employed in the opera- 
tion of street-railway passenger cars for a 
sudden stopping of the car as if by a col- 
lision, due to opposition between two 
motors. 

Buckled Diaphragm.— A fault in a 
telephonic transmitter or receiver due to 
a dent or warping in the diaphragm. 

Buckling. — The warping or irregularities 
produced in the surface of the plates of 
storage cells by a too rapid discharge. 

Buffing. — Preparing surfaces for the re- 
ception of electro-plating by subjecting 
them to the polishing action of a revolv- 
ing wheel covered with a buff, on the 
surface of which rouge has been spread. 

Bug. — (1) A term employed in quadru- 
plex telegraphy to designate any fault in 
the operation of the apparatus. (2) Gen- 
erally, a fault in the operation of any 
electric apparatus. (3) A particular fault 
or difficulty in quadruplex telegraphy 
consisting of an interference between the 
A and B-sides. 

Bug-Trap. — A device employed to over- 
come the bug in quadruplex telegraphy. 

Building-Iron. — A heated iron tool by 
means of which the mould impressed by 
a printed page, which it is desired to 
electro-type, is built up preparatory to its 
being placed in the plating bath. 

Building Knife. — A heated knife-shaped 
tool employed in removing the wax that 
has been forced up around the sides of 
the matrix during the taking of the im- 
pression. 

Building Process for Electro-Type 
Metals. — A process for bringing up the 
blank spaces in the mould of an electro- 
type by the addition of wax plates melted 
into place by the building-iron, the high 
spaces thus built-up becoming depressions 
in the finished plate. 

Building Switch. — A switch provided 
with an insulating handle for cutting a 
building in or out of an electric circuit, 
usually, a series circuit. 

Building Tool.— A form of building iron. 



Bui.] 



701 



[Bus, 



" Building-TJp " of Dynamo.— The ac- 
tion whereby a dynamo-electric machine 
rapidly reaches its maximum E. M. F. 
after starting. 

" Built-in " Underground Conductor. 
An underground conductor which, in- 
stead of being placed in the duct of a 
conduit or tube so as to be capable of re- 
moval therefrom, at any time, is perma- 
nently " built in" or surrounded by the 
insulating and protective material. 

"Built-TJp" Magnet.— A composite per- 
manent magnet. 

Bullet Probe. — A probe containing elec- 
trical conductors, so arranged that the 
contact of the probe with a bullet closes 
an electric circuit and operates an electric 
signal. 

Bunched Cable. — A cable containing 
more than a single wire or conductor. 

Bunsen Screen. — The screen of a Bunsen 
or translucent-disc photometer. 

Bunsen Voltaic Cell. — A zinc-carbon 
couple whose elements are immersed 
respectively in electrolytes of dilute sul- 
phuric and strong nitric acids. 

Buoy, Electric. — A buoy on which elec- 
trically produced luminous signals are 
displayed. 

Burette. — A graduated glass tube em- 
ployed for readily measuring the volume 
of a liquid. 

Burglar- Alarm, Electric. — An electric 
device for automatically announcing the 
opening of a door, window, closet, drawer 
or safe, or the passage of a person through 
a hallway, or on a stairway. 

Burglar-Alarm Annunciator, Elec- 
tric. — An annunciator used in connec- 
tion with a system of burglar-alarms. 

Burglar-Alarm Contacts. — Contacts fit- 
ted to windows, doors, tills, safes, floors, 
etc., so that the movements of the various 
parts from their natural positions, sound 
an alarm. 

Burglar-Alarm Matting. — A matting 
provided with a number of invisible con- 
tacts connected with an alarm bell, whose 
circuits are closed by treading on the 
matting. 

Buried Cable or Conductor.— An un- 
derground cable or conductor placed di- 
rectly in the earth, in contra-distinction 
to one placed in a conduit or subway. 

Buried Transformer. — A transformer, 
provided with a water-tight cover and 
placed below the surface of the ground. 

Burn-Out. — The destruction of an arma- 
ture, or any part of an electric apparatus, 



by the passage of an excessive current 
due to short-circuit or other cause. 

Burned-Out Incandescent Lamp.— An 
incandescent lamp which through con- 
tinued use is no longer able to furnish 
electric light. 

Burner, Electric— A gas-burner that is 
capable of being electrically lighted. 

Burnetize.— To subject to the burnetizing 
process. 

Burnetizing.— A method adopted for the 
preservation of wooden telegraph poles, 
by injecting a solution of zinc-chloride 
into the pores of the wood. 

Burning at Commutator of Dynamo. 
An arcing at the brushes of a dynamo- 
electric machine, due either to their im- 
perfect contact or improper position, re- 
sulting in the loss of energy to the circuit, 
and the destruction of the commutator 
segments, or of the brushes. 

Burnishing.— A process by means of 
which surfaces are prepared for electro- 
plating by subjecting them to the action 
of burnishing tools. 

Burnt Electro-Metallurgical Deposit. 
The black deposit of metal which is 
thrown down when the intensity of the 
depositing current is too strong. 

Bus. — A word generally used instead of 
omnibus. 

Bus-Bar Connectors.— Connectors em- 
ployed for connecting or joining the ends 
of bus-bars. 

Bus-Bar Stand.— A bus-bar support on a 
switchboard. 

Bus-Bar Voltmeter.— A voltmeter em- 
ployed in a central station for measuring 
the pressure between the bus-bars. 

Bus-Bars. — Heavy bars of conducting 
metal connected directly to the poles of 
one or more dynamo-electric machines, 
and, therefore, receiving the entire cur- 
rent produced by the machines. 

Bus Field-Excitation. — Excitation of the 
field of a generator by current taken 
directly* from the bus-bars. 

Bus-Rods or Wires.— Terms frequently 
used for bus-bars. 

Bushing of Socket. — A sleeve or cylinder 
of insulating material inserted at the 
entrance of a lamp socket for the pro- 
tection of the entering conductors. 

Busy -Back. — A jack at a central telephone 
exchange connected with a battery and 
vibrator, in such a way that the operator 
by inserting the plug of an incoming line 
into this jack can notify a calling operator 
that the subscriber desired is busy. 



Bus.] 



702 



[Cab, 



Busy Test. — A simple test whereby a tele- 
phone operator at a multiple switchboard 
can readily tell whether any wire or cir- 
cuit connected with the switchboard is 
or is not in use at any moment of time. 

Butt Joint. — (1) An end-to-end joint. (2) 
A joint effected in wires by placing the 
wires end on and subsequently soldering 
or welding them. 

Butt Prop. — A tool sometimes called a 
"dead man," used in the erection of 
telegraph poles. 

Button Repeater. — A manual telegraphic 
repeater whereby the proper connections 



are made for repeating a message in 
either direction, by turning a button. 

Buzzer, Electric.— (1) A call, not as loud 
as that of an electric bell, employing a 
humming sound by the use of a suffi- 
ciently rapid automatic contact-breaker. 
(2) A telephone receiver for morse circuits 
employing a vibrating contact key. 

Buzzing of Bell.— An improper action of 
an electric bell, whereby it produces a 
buzzing sound instead of its proper ring- 
ing. 

By-Pass of Discharge.— A term some- 
times employed for alternative path. 



C — A contraction for Centigrade. 

C. — A contraction for current. 

C. — A symbol for capacity. (Partly inter- 
national usage.) 

C. — A symbol for coulomb. 

C. E. M. F. — A contraction for counter 
electromotive force. 

C. G. S. — A contraction for centimetre- 
gramme-second. 

C C. — A contraction for cubic centimetre, 
the C. G. S. unit of volume. 

cm. — An abbreviation for centimetre, the 
C. G. S. unit of length. 

cm 2 . — An abbreviation for square centi- 
metre, the C. G. S. unit of surface. 

cm 3 . — An abbreviation for cubic centi- 
metre, the C. G. S. unit of volume. 

C. M. M. P. — A contraction for counter- 
magnetomotive force. 

C. P. — A contraction for candle-power. 

C. R. — A contraction for conductor-resist- 
ance. 

C 2 R Activity.— (1) The I 2 R activity. 
(2) That portion of the electric activity 
which is expended in heating the con- 
ductor, and due to the ohmic resistance 
offered by the conductor to the passage 
of the current. (3) The thermal activity 
of a circuit expressed in watts, and equal 
to the square of the current strength in 
amperes multiplied by the resistance in 
ohms. 

C 2 R Loss. — The loss of energy in a con- 
ductor due to the ohmic resistance and 
the current strength. 

C. G-. S. Units. — The centimetre-gramme- 
second units. 

Cabinet Seat Contact.— A contact 
placed in a silence telephone cabinet, 
underneath a seat, and closed by the 
weight of a person on the seat. 



Cable. — (1) An electric cable. (2) A mes- 
sage transmitted by means of an electric 
cable. 

Cable. — To send a telegraphic despatch by 
means of a cable. 

Cable Alphabet.— Tli e code or telegraphic 
alphabet employed in cable signalling. 

Cable Box.— A box provided for the re- 
ception and protection of a cable head, 

Cable Buoy. — A buoy generally secured 
by a mushroom anchor and provided for 
temporarily holding or securing an end of 
a cable during its laying or repair. 

Cable Casing. — The metallic sheathing of 

a cable. 
Cable Cell.— A voltaic cell formed by an 

exposed broken end of a submarine copper 

conductor and the iron sheathing of the 

cable. 

Cable Clearing-House System.— A 

system whereby every message sent over 
a submarine cable is returned to the head 
office and a comparison effected between 
the original message, as received for 
transmission, and the final message, as 
delivered to the addressee. 

Cable Clip. — A term sometimes used for 
cable hanger. 

Cable Closing Machine. — A machine for 
covering a cable with its sheathing. 

Cable Code.— (1) A cable alphabet. 
(2) A cable cipher. 

Cable Core. — (1) The insulated conducting 
wires of an electric cable. (2) The elec- 
trically essential portion of a cable as dis^ 
tinguished from its sheath or protection. 

Cable Cross-Connecting Board.— In a 
telephone exchange, where a number of 
cables enter the building from the outside, 
a distributing board, placed in a termi- 
nal room to facilitate the work that is 



Cab.] 



'03 



[Cab. 



constantly going on of making and chang- 
ing the connections of the subscribers' 
lines to the switchboard cables. 

Cable Currents. — (1) Various currents that 
exist in a submarine cable and interfere 
with the testing, consisting of earth cur- 
rents, electrostatic charge and discharge 
currents, and polarization currents due to 
a fault or break. (2) A current flowing 
through a cable in the absence of any im- 
pressed E. M. F. (3) The current which 
tends to flow in a broken cable from the 
exposed copper conductor at the fracture 
to the iron sheathing through the ap- 
paratus at the station. 

Cable Despatch.— A despatch sent by 
means of a cable. 

Cable Drum. — (1) In cable machinery, a 
drum on which cable is wound for coil- 
ing, shipping, laying, or turning over. 
(2) A drum or reel on which cable is 
wound for transport. 

Cable, Electric. — A combination of an 
extended length of a single insulated elec- 
tric conductor, or of two or more sepa- 
rately insulated electric conductors, cov- 
ered externally with a metallic sheathing 
or armor. 

Cable Fault. — Any failure in the proper 
working of a cable due either to a total 
or partial fracture of the cable, or to a 
heavy electric leakage. 

Cable Float.— A float employed for tem- 
porarily relieving the tension on a cable 
while it is being paid out. 

Cablegram. — A telegraph message re- 
ceived by cable. 

Cable Grapnel. — A heavy pronged iron 
hook provided for picking up a cable by 
grappling. 

Cable Grip. — (1) The grip provided for 
holding the en d of an underground cable 
while it is being drawn into a duct. 
(2) In a cable road the grip by means of 
which a car is driven by the moving 
cable. 

Cable Ground.— The locality of a cable 
operation or repair. 

Cable Hanger. — A hanger or hook suit- 
ably secured to a cable and designed to 
sustain its weight by intermediately sup- 
porting it on an iron or steel wire strung 
above the cable. 

Cable Hanger Tongs. — Tongs provided 
with long handles for attaching the 
hangers of an aerial cable to the suspend- 
ing wire or rope. 

Cable Head. — A rectangular board pro- 
vided with binding posts and fuse wires 



for the purpose of receiving the wires of 
overhead lines where they enter a cable. 

Cable House. — A hut provided for secur- 
ing and protecting the end of a submarine 
cable when it is landed. 

Cable Hut. — A cable house. 

Cable Joint. — An insulated electric con- 
nection made between the cores of two 
separate lengths of cable. 

Cable Junction-Box. — A junction box for 
holding and protecting the insulated 
connections or joints between cables. 

Cable Laid-Up-in-Layers.— A cable all 
of whose conducting wires are in layers. 

Cable Laid-Up-in-Re verse-Layers. —A 
cable the alternate layers of whose con- 
ductors are twisted in opposite directions. 

Cable Laid-up-in-Twisted-Pairs.— A 
cable every pair of whose wires is twisted 
together. 

Cable Land Line.— (1) A land line com- 
posed of cable. (2) A land line connected 
to a cable. 

Cable Laying. — The process of placing a 
cable on the sea-bottom. 

Cable Lead. — A lead formed of a cable 
of several stranded conductors, as dis- 
tinguished from a lead containing a 
single conductor. 

Cable Message.— A cable despatch. 

Cable Office. — An office connected with a 
cable. 

Cable Protector.— (1) A device for the 
safe discharge of the charge induced in 
the metallic sheathing of a cable, or in 
the conductors surrounding or adjacent 
to the cables, consequent on changes in 
the electromotive force applied to the 
conducting core of the cable. (2) A fuse 
device provided for the protection of each 
of the wires of an aerial cable, placed in 
the cable head at the junction where an 
aerial line enters the cable head. 

Cable Rack. — A rack placed at the back 
of a multiple telephone switchboard for 
supporting the cabled switchboard con- 
ductors and providing ready access to the 
same. 

Cable Repairing.— The process of repair- 
ing a broken or faulty cable. 

Cable Resister.— A form of float or buoy 
provided for lessening the strain on a 
cable while paying it out. 

Cable Road.— A system of car propulsion 
in which the cars are drawn by the 
movement of an underground cable to 
which the moving cars are attached by a 
suitable grip. 



Cab.] 



704 



[Cal. 



Cable Sending-Key.— A key employed 
for readily sending the positive and nega- 
tive current impulses required to trans- 
mit the cable alphabet or code. 

Cable Serving.— A covering of hemp Or 
jute spun around the insulated core of a 
cable in order to protect it from the pres- 
sure of the iron wire armor or sheathing 
of the cable. 

Cable Ship. — A ship provided with the 
apparatus required for laying or repairing 
submarine cables. 

Cable Signals. — Signals received over the 
circuit of a cable. 

Cable Speaking-Set.— The apparatus 
used in signalling over a cable. 

Cable Spinning-Jenny.— A device for 
readily binding an aerial cable to a sup- 
porting wire. 

Cable Splice. — A connection between the 
sheathing or armor of two lengths of 
cable. 

Cable Stopper. — A flexible grip applied 
to a cable to keep it from moving or 
slipping. 

Cable Suspender.— A device for suspend- 
ing an aerial cable. 

Cable Switchboard.— A switchboard to 
which the cable conductors are connected. 

Cable Tank. — A strong water-tight tank 
placed on a cable ship and provided for 
holding a coiled section of cable that is 
ready for laying. 

Cable Telegraph. — A general term in- 
cluding all the apparatus employed in 
cable telegraphy. 

Cable Telegraphy. — Telegraphic com- 
munication carried on over a submarine 
cable. 

Cable Terminal. — A water-tight covering 
provided at the free end of a telephone 
cable to prevent injury to the cable's in- 
sulation by the moisture of the air. 

Cable Terminal-Pole. — The terminal pole 
of an aerial line provided where the ends 
of an aerial line are connected with an 
underground cable for the support of the 
cable head. 

Cable Terminal - Switchboard. — A 

board in a cable head where the wires 
are spread out and connected in proper 
order to a number of binding posts which 
in their turn are connected through fuse 
wires to binding posts receiving the ends 
of overhead wires. 

Cable Transformer. — An alternating- 
current transformer in which the pri- 
mary and secondary conductors have the 



form of a cable overlaid by an iron 
sheath or magnetic circuit. 

Cable Vault. — A vault provided in a 
building where cables enter from under- 
ground conduits, and where the cables 
are opened and connected to fusible plugs 
or safety catches. 

Cable Testing. — The process or methods 
of trying or measuring the electric or 
mechanical capabilities of a cable. 

Cable Well. — A cable tank. 

Cable Winder. — A cable spinning- jenny. 

Cable Work. — Any operation connected 
with the manufacture, shipping, laying, 
testing, or repair of cables. 

Cable Worming.— A central core of hemp 
or jute around which are wrapped the 
several separate conductors of any cable 
that contains more than a single con- 
ductor. 

Cabled. — Transmitted by means of cable 
telegraphy. 

Cabling. — Transmitting by means of cable 
telegraphy. 

Cadmium Standard Cell.— A standard 
voltaic cell of very low temperature 
coefficient of variation in E. M. F., em- 
ploying a cadmium-zinc couple. 

Cage Lightning-Protector. — A term 
sometimes employed for a lightning pro- 
tector consisting of wires in the form of 
a cage surrounding the body to be pro- 
tected. 

Calamine, Electric— A crystalline va- 
riety of silicate of zinc that possesses pyro- 
electric properties. 

Calculagraph. — A machine employed in 
long-distance telephony for registering 
the time during which the use of a line 
by a subscriber continues. 

Cal-Eleetrie Generator.— A generator 
whose operation depends on the produc- 
tion of electricity in the secondary coil of 
a transformer by changes of temperature 
in its iron core. 

Cal-Electrieity . — Electricity produced by 
changes of temperature in the iron core 
of a transformer. 

Calibrate. — To determine the absolute or #■ 
relative values of the scale divisions, or of 
the indications of any electrical instru- 
ment, such as a galvanometer, electro- 
meter, voltmeter, wattmeter, or other 
similar instrument. 

Calibrating. — Determining or marking off 
the values or readings of a galvanometer, 
electrometer, voltmeter, wattmeter, or 
other similar electrical instrument. 

Call.— (1) In telephony, the signal or call of 



€alj 



05 



[Can, 



a subscriber for connection to some other 
subscriber. (2) In telegraphy, the signal 
for attention, or the call for response from 
the distant operator. 
Call-Bell, Electric— An electric bell used 
to call the attention of an operator to the 
fact that his correspondent wishes to 
communicate with him. 

Call-Key. — Any suitable key for sending 
an electric call. 

Callaud Voltaic Cell. — A name some- 
times given to the blue-stone gravity cell. 

Calling Circuit. — In the Law system of 
telephony, a common calling- w T ire circuit 
connecting the central exchange through 
all the subscribers' offices in a given 
group, and employed for sending calls to 
the central office. 

Calling Drops. — In an isolated-station 
switchboard, drops employed for indicat- 
ing the particular subscriber calling. 

Calling Plug.— That plug of a pair of 
plugs, at a central telephone switchboard, 
which is inserted in the jack of the sub- 
scriber wanted and through which that 
subscriber is called up. 

Calling Side of Telephone Circuit. — 
That side of a telephone circuit over 
which a call arrives. 

Calling Station. — Any station that desires 
to be placed in communication with an- 
other station. 

Calling Wire. — A wire forming the call- 
ing circuit in a system of telephony. 

Call Signal. — In telegraphy, the signal or 
group of signals indicating the particular 
station called. 

Call Wire. — (1) A speaking wire. (2) A 
wire connecting two telephone exchanges, 
for the purpose of transmitting instruc- 
tions, as distinguished from a wire em- 
ployed for establishing communication 
between subscribers. (3) A w T ire employed 
for calling the attention of a central- 
station operator by a subscriber, as dis- 
tinguished from the wires through which 
he communicates with other subscribers. 

Call- Wire Key. — A subscriber's key em- 
ployed to call the operator at a central 
telephone station. 

Call- Wire Switchboard.— A switchboard 
at a telephone station auxiliary to a 
multiple switchboard in a call-wire 
system, and employed for suitably divid- 
ing up call- wires among the operators, 
so as to equalize their work. 

Call- Wire System.— A system of tel- 
ephony in which special wires are em- 

45 



ployed to call the operator at the central 
station. 

Calorescence.— The transformation of ob- 
scure heat rays into luminous rays on 
impact with certain solid substances. 

Caloric. — A term formerly applied to the 
assumed fluid that was believed to be the 
cause or essence of heat. 

Calorie.— (1) A heat unit. (2) The quantity 
of heat required to raise 1 gramme of 
water 1° centigrade. 

Calorific Intensity .—The temperature at- 
tained in combustion. 

Calorimeter. — An instrument for measur- 
ing the amount of heat contained in, or 
developed by, a given body. 

Calorimeter, Electric— An instrument 
for measuring the heat developed, in a 
given time, in any conductor, by an elec- 
tric current. 

Calorimetric— Of or pertaining to the 
calorimeter. 

Calorimetric Conductivity. — Specific 
heat transference, or the conductivity of 
a substance based on the quantity of heat 
transferred in a given time, independently 
of the temperature attained. 

Calorimetric Measurement. — The meas- 
urement of heat energy by means of a 
calorimeter. 

Calorimetric Photometer. — A photo- 
meter in which the light to be measured 
is absorbed by the face of a thermo-pile, 
and its photometric intensity estimated 
from the strength of the electric current 
thereby produced. 

Calorimetry. — The art of measuring heat 
energy by means of a calorimeter. 

Calorimotor. — (1) A deflagrator. (2) A 
word formerly employed for a number of 
series-connected voltaic cells. (Obsolete.) 

Calory. — A less preferable orthography 
sometimes employed for calorie. 

Canalization. — (1) A network of conduct- 
ors. (2) A system of electric mains. 

Candle. — (1) A unit of photometric inten- 
sity. (2) The photometric intensity which 
would be produced by a standard candle 
burning at the rate of two grains per 
minute. 

Candle Balance. — A balance support pro- 
vided for the standard candle of a photo- 
meter, so arranged as continuously to 
weigh the candle and so determine its rate 
of consumption while in use. 

Candle, Electric. — A Jablochkoff candle. 

Candle-Foot. — A unit of illumination 

equal to that normally produced by a 



706 



[Cap. 



standard British candle, at a distance of 
one foot, and sometimes called a lux. 

Candle-Power.— (1) The intensity of light 
emitted by a luminous body estimated in 
standard candles. (2) The photometric 
intensity of one standard candle . 

Canopy. — (1) In a multiple telephone ex- 
change, an overhanging frame suitably 
supported from above, and containing 
plugs and drops. (2) An ornamental 
metallic covering employed in incandes- 
cent lighting for an electrolier or pendant 
outlet. 

Canopy Switch.— An overhead switch 
placed at each end of a trolley car for the 
purpose of permitting the motorman to 
turn the current on or off the car as de- 
sired, when, for example, he wishes to in- 
spect a fuse block or controller without 
pulling down the trolley pole. 

Cant Hook. — A tool employed in the erec- 
tion of telegraph poles consisting of a pole 
furnished with a curved pivoted hook 
employed for turning or rolling a telegraph 
pole. 

Caoutchouc. — (1) A resinous substance 
possessing high powers of electric insula- 
tion, obtained from the milky juice of cer- 
tain tropical trees. (2) India rubber. 

Cap Wire. — An overhead wire carried on 
the summit of a pole, as distinguished 
from an overhead wire carried on a cross 
arm. 

Capability of Dynamo - Electric Ma- 
chine. — The maximum theoretical activ- 
ity of a dynamo as expressed by the square 
of its electromotive force divided by its 
resistance. 

Capacitance. — (1) A term proposed in 
place of capacity. (2) The reactance of 
a condenser in an alternating-current 
circuit. 

Capacity Balance of Duplex System.— 
The balance of capacity in duplex teleg- 
raphy as opposed to a balance of resist- 
ance. 

Capacity Circuit. — A circuit containing 
capacity but no inductance. 

Capacity Current of Cable.— (1) The 
current in a cable due to its capacity. 
(2) The charging or discharging current 
in a cable. 

Capacity Load. — The apparent load or 
current of a high-tension generator due 
to the capacity of the distributing con- 
ductors as distinguished from the load or 
current usefully distributed. 

Capacity of Accumulator. — The avail- 
able output of a storage battery expressed 
either in ampere-hours, or in watt-hours. 



Capacity of Cable.— (1) The quantity of 
electricity required to raise a given length 
of cable to a given potential, divided by 
the potential. (2) In a multiple cable, the 
amount of charge at unit potential which 
any single conductor will take up, the 
rest of the conductors being grounded. 
(3) The ability of a conducting wire or 
cable to permit a certain quantity of 
electricity to be passed into it before ac- 
quiring a certain potential. 

Capacity of Cable Tank.— The accom- 
modation of a cable tank expressed either 
voluminally in cubic feet, or in relation 
to the number of miles of a given type of 
cable which can be practically stowed 
away in it. 

Capacity of Condenser.— (1) The quan- 
tity of electricity a condenser is capable 
of holding in coulombs when charged to 
a pressure of one volt. (2) The ratio be- 
tween the quantity of electricity in cou- 
lombs on one coating of a condenser and 
the potential difference in volts between 
the two coatings. 

Capacity of Leyden Jar.— The quantity 
of electricity a Leyden jar will take under 
unit difference of potential. 

Capacity of Line. — The ability of a line 
to act as a condenser, and, therefore, like 
it, to possess capacity. 

Capacity of Polarization of Voltaic 
Cell. — The capacity of becoming polar- 
ized when subjected to a steady discharge. 

Capacity of Secondary or Storage Cell. 
The capacity of an accumulator. 

Capacity Pressure.— (1) In a condenser 
connected with a source of alternating 
currents, a pressure in phase with the 
condenser current. (2) A pressure due 
to a capacity. (3) The pressure at the 
terminals of a condenser. 

Capacity Reactance. — (1) The reactance 
of a condenser due to its capacity. 
(2) The condensance. (3) The capacitance. 

Capacity Resistance.— (1) A term pro- 
posed for the resistance which a conden- 
ser or other substance possessing electric 
capacity offers to the passage of an alter- 
nating electric current. (2) The impe- 
dance of a condenser. 

Capillarity. — The elevation or depression 
of liquids in tubes of small internal diam- 
eter. 

Capillary. — Of small or hair-like diameter 
or size. 

Capillary Attraction. — The molecular 
attractions concerned in capillary phe- 
nomena. 



Cap.] 



707 



[Car 



Capillary Contact-Key. — A form of fluid 
contact-key in which the circuit is closed 
or broken by means of a wire which is 
dipped into or removed from the surface 
of a mass of mercury. 

Capillary Electrometer.— An electro- 
meter, in which difference of potential 
is measured by the movements of a drop 
of sulphuric acid in a tube filled with 
mercury. 

Capsizing Thermometer. — A thermom- 
eter employed in deep sea soundings for 
cable work, which is caused to record the 
temperature at the moment the lead 
commences to ascend from the bottom, 
by causing the thermometer to be re- 
versed or capsized. 

Car Annunciator. — An annunciator 
placed in a car for the purpose of calling 
a waiter or porter. 

Car Barn. — A covered shed provided with 
tracks in which trolley cars are stored 
when not in use. 

Car Body. — The wooden framework of a 
street-railway car which encloses the 
space provided for the passengers. 

Car-Brake, Electric— A car-brake that 
is operated by the electric current pro- 
duced by the motor acting as a generator 
when the current is turned off and the 
car is rapidly moving. 

Car-Brake Mechanism.— The mechan- 
ism for applying the brake to a car- wheel. 

Car Controller. — (1) A device placed at 
each end of the platform of a trolley car, 
under the control of the motor man for 
starting, stopping, reversing or changing 
the velocity of a trolley car. (2) A series- 
parallel car-controller. 

Car-Heater, Electric. — An electric heat- 
er consisting essentially of suitably sup- 
ported coils of insulated wire traversed 
by an electric current. 

Car-Lamp, Electric. — An incandescent 
lamp generally provided with an anchored 
filament, suitable for use in street-railway 
cars. 

Car-Propulsion, Electric— The propul- 
sion of cars by means of electric motors. 

Car Truck. — The part of a car on which 
the car body rests. 

Car Wiring. — The distribution of conduct- 
ors on an electric street car. 

Carbon. — An elementary substance which 
occurs naturally in three distinct allo- 
tropic forms : graphite, charcoal and the 
diamond. 

Carbon Arc. — A voltaic arc formed be- 
tween carbon electrodes. 



Carbon Brushes for Electric Motors 
or Generators. — Plates of artificial car- 
bon employed as the brushes of dynamos 
or motors. 

Carbon Button.— A button-shaped carbon 
mass whose resistance varies with press- 
ure. 

Carbon Cell.— (1) A silvered plate of glass 
provided on its silvered side with a num- 
ber of zigzag furrows filled with carbon 
soot, and employed as the receiving in- 
strument in a photophone. (2) A voltaic 
cell employing carbon as one of its ele- 
ments. 

Carbon Clutch or Clamp for Arc 
Lamps. — A clutch or clamp attached to 
the lamp rod or the support of the positive 
or upper carbon of an arc lamp, provided 
for gripping or holding the carbon. 

Carbon Diaphragm of Telephone. — 
A thin sheet of carbon employed as the 
diaphragm in certain forms of telephone 
transmitters. 

Carbon Electrodes for Arc Lamps. — 
The carbons of an electric arc lamp be- 
tween which the arc is maintained. 

Carbon Holder. — A device employed in 
an arc lamp for supporting the lower or 
negative carbon. 

Carbon Megohm.— A resistance of ap- 
proximately one megohm composed of a 
thin film or strip of graphite. 

Carbon Motor Brush.— A carbon brush 
employed on a motor. 

Carbon Pencils. — A word sometimes used 
for the carbons employed in arc lamps. 

Carbon-Point Lightning-Arrester.— A 
lightning arrester in which the disruptive 
discharge occurs between opposed carbon 
points. 

Carbon Points. — The carbon rods or pen- 
cils employed in arc lamps. 

Carbon Rheostat. — An adjustable resist- 
ance formed of carbon plates or powder 
whose resistance can be varied by pres- 
sure. 

Carbon Telephone Transmitter.— A 
telephone transmitter whose operation is 
dependent on variations in the resistance 
of a carbon button, or of a mass of loose 
granulated carbon, on the to-and-fro 
movements of the diaphragm. 

Carbon Tongs. — A pair of tongs suitable 
for gripping arc-light carbons. 

Carbon Transmitter. — A carbon tele- 
phone transmitter. 

Carbons. — A general term applied to the 
carbons or negative elements of voltaic 
cells. 



Car.] 



708 



[Cat, 



Carbonic Acid Gas.— A gaseous substance 
formed by the union of one atom of car- 
bon with two atoms of oxygen. 

Carboning Lamps.— Placing carbons in 
electric arc lamps. 

Carbonizable. — Capable of being carbon- 
ized. 

Carbonization. — The act of carbonizing. 

Carbonize. — To reduce a carbonizable sub- 
stance to carbon. 

Carbonized Cloth Discs for High Re- 
sistance. — Discs of cloth carbonized by 
heating to an exceedingly high temper- 
ature while out of contact with air. 

Carbonizer. — Any apparatus suitable for 
reducing a carbonizable • material to car- 
bon. 

Carbonizing. — Subjecting a carbonizable 
substance to the process of carbonization. 

Carbonizing Box.— A box prepared for 
holding the carbon filaments of incandes- 
cent lamps during their carbonization. 

Carbonizing Frame.— A suitably shaped 
block of carbon prepared for winding the 
cotton threads, or other plastic carboniz- 
able material, employed for the filaments 
of incandescent lamps, before submitting 
them to the carbonizing process. 

Carcass of Dynamo-Electric Machine. 

A term sometimes used for the iron frame- 
work of a dynamo. 

Carcel. — (1) A French photometric stand- 
ard of light. (2) The light emitted by 
a lamp of definite dimensions burning 
42 grammes of Colza oil in an hour, with 
a flame 40 millimetres in height. 

Carcel Lamp. — An oil lamp employed in 
France as a photometric standard. 

Carcel Standard.— The carcel. 

Carcel Standard Gas-Jet.— A lighted 
gas jet employed for determining the can- 
dle-power of gas by measuring the height 
of a jet of gas, burning under certain 
conditions, when used in connection with 
the light of a larger gas-burner burning 
under similar conditions, for a photo- 
metric measurement of electric lights. 

Cardan Suspension of Compass 
Needle. — The gimbal suspension of a 
compass needle. 

Cardew Voltmeter. — A voltmeter whose 
indications are obtained by the expansion 
of a long fine wire by the passage through 
it of the current to be measured. 

Carnot's Cycle.— A cycle of steps or oper- 
ations proposed by Carnot for convenience 
in studying the transformation of heat 
into work. 



Carriers of Replenishes— The moving 
'conductors of a replenisher which carry 
the charges and thus permit an accumu- 
lation of such charges. 

Carrying Capacity. — The maximum cur- 
rent strength that any conductor can 
safely transmit. 

Carrying Capacity of Safety Fuse.— 
The maximum current strength which a 
fuse wire or block can carry without 
melting. 

Carrying Hooks. — A pair of curved hooks 
pivoted together and provided with han- 
dles, for carrying telegraph poles. 

Cascade Charging of Leyden Jars or 
Condensers. — A method of charging 
Leyden jars or condensers by means of 
the electricity liberated by induction 
from one coating when a charge is pass- 
ing into the other coating. 

Cascade Connection. — A term sometimes 
employed for series connection. 

Cascade Connection of Condensers. 
A term sometimes employed for a series- 
connection of condensers. 

Case-Hardening, Electric— S u p e r- 
ficially hardening a piece of metal by 
means of electrically generated heat. 

Case Wiring. — A wiring in which the elec- 
tric conductors are held in place on the 
walls or ceilings of a room by means of 
continuous cleats. 

Casings. — Grooves or panelled channels 
for carrying wires in a house. 

Cast Rail-Bond.— A method for bonding 
the successive track rails, in a system of 
trolley propulsion, by casting molten 
iron around all except the upper portions 
of the joint. 

Casting, Electric. — A process for casting 
metals, in which the metals are fused by 
means of heat of electric origin. 

Castor and Pollux Light.— A term for- 
merly used for the St. Elmo's fire. 

Catalisis. — An objectionable orthography 
sometimes employed for catalysis. 

Catalysis. — The influence produced on 
chemical combination or decomposition, 
by the presence of certain substances 
which, without undergoing any changes 
themselves, produce changes in the affini- 
ties of other substances by their mere 
contact or presence. 

Catalytic. — Of or pertaining to catalysis. 

Cataphoresis. — Electric osmose. 

Cataphoretic. — Of or pertaining to cata- 
phoresis. 

Cataphoretic Actio n. — Cataphoretic 
medication or demedication. 



€at.] 



'09 



[Cei. 



Cataphoretic Demedication.— A means 
whereby material is removed from differ- 
ent parts of the body by means of cata- 
phoresis. 

Cataphoretic Electrode. — (1) An elec- 
trode containing in solution the drug or 
medicament that is to be introduced into 
the body by cataphoresis. (2) The anode. 

Cataphoretic Medication.— The intro- 
duction of a drug or medicament into the 
body by means of cataphoresis. 

Cataphoric. — Of or pertaining to cata- 
phoresis. 

Catelectrotonus. — An orthography some- 
times employed for cathelectrotonus. 

Catenary. — A catenary curve. 

Catenary Curve.— The curve described 
by the sagging of a wire, under its own 
weight, when stretched between two 
points of support. 

Catheleetrotonic. — Of or pertaining to 
cathelectrotonus. 

Catheleetrotonic State.— The condition 
of increased functional activity of a 
nerve in the neighborhood of the cathode 
to whose influence it is subjected. 

Catheleetrotonic Zone. — A name some- 
times given to the peripolar zone. 

Cathelectrotonus. — In electro-therapeu- 
tics the condition of increased functional 
activity that occurs in a nerve in the 
neighborhood of the cathode or negative 
electrode. 

Cathetometer. — An instrument for the 
accurate measurement of small heights 
or distances. 

Cathion. — The electro-positive ion, atom, 
or radical, into which the molecule of an 
electrolyte is decomposed by electrolysis. 

Cathodal. — Of or pertaining to the 
cathode. 

Cathode. — (1) The conductor or plate of 
an electro-decomposition cell connected 
with the negative terminal of a battery 
or other electric source. (2) The terminal 
of an electric source into which the cur- 
rent flows from the electrolyte of a de- 
composition cell or voltameter. (3) The 
electrode of a bath, tube, body, or device 
by which the current leaves the same. 
(4) The negative electrode. 

Cathode Cup. — (1) A cup-shaped cathode 
of an X-ray tube. (2) A concave mirror 
attached to the cathode of an X-ray or 
other high- vacuum tube. 

Cathode Pictures.— X-ray or Roentgen- 
ray pictures. 

Cathode Ray Spectrum. — A succession 
of light and dark phosphorescent bands 



produced on a screen, in an exhausted 

Crookes tube, by magnetically deflected 

cathode rays. 
Cathode Rays.— Radiation emitted from 

the cathode or negative electrode of a 

Crookes or X-ray tube. 
Cat ho die. — Of or pertaining to the 

cathode. 

Cathode Streams.— Cathode rays. 

Cathodic Current.— In a polarized vol- 
taic couple immersed in acidulated water, 
the current produced by the agitation of 
the plate connected with the cathode. 

Cathodic Electro-Diagnostic Reac- 
tions. — The reactions which occur at the 
cathode placed on or over any part of a 
living body. 

Cathodic Rays.— The cathode rays, 

Cathodic Streamings.— Cathode rays. 

Cathodogram. — A Roentgen or X-ray 
picture. 

Cathodograph.— A radiograph. 

Cation. — An orthography sometimes em- 
ployed for cathion. 

Catoptrics. — That branch of optics which 
treats of the reflection of light. 

Cauterization. — The act of cauterizing or 
burning with a heated, solid or caustic 
substance. 

Cauterization, Electric— Subjecting to 
cauterization by means of an electrically 
heated wire. 

Cauterize. — To subject to cauterization. 

Cauterizer, Electric— A name some- 
times given to an electric cautery. 

Cautery Battery. — A term sometimes 
employed in electro-therapeutics for a 
multiple-connected voltaic battery adapt- 
ed for producing incandescence for cau- 
tery effects. 

Cautery Cabinet. — A cabinet containing 
a cautery battery, switchboard, cautery 
knives and other necessaries for electric 
cauterization. 

Cautery Cell. — A cell suitable for use in 
a cautery battery. 

Cautery, Electric. — The application to 
the human body of variously shaped plat- 
inum wires, heated to incandescence by 
the electric current, for removing dis- 
eased growths, or for stopping hemor- 
rhages. 

Cautery Knife-Electrode. — A knife- 
shaped electrode that is rendered incan- 
descent by the passage through it of an 
electric current. 

Ceiling Block. — An attachment fastened 
to the ceiling for suspending flexible 



Cei.] 



710 



[Cen. 



cords, and connecting them with the sup- 
ply wires of an incandescent system. 
Ceiling Board. — An arc light hanger 
board. 

Ceiling Bracket. — (1) A ceiling canopy. 
(2) A bracket for supporting an insulated 
wire or wires to a ceiling. 

Ceiling Cut-Out. — A cut-out placed in a 
ceiling block. 

Ceiling Fan. — An electrically driven fan 
suspended from the ceiling. 

Ceiling Rose. — An ornamental ceiling 
plate from which an electric conductor 
passes. 

Ceiling Rosette. — An ornamental, rose- 
shaped ceiling block. 

Cell of Primary or Secondary Battery. 
A jar of a primary or secondary battery 
containing a single couple and its elec- 
trolyte. 

Celluloid Lamp-Filament. — A lamp 

filament made by carbonizing celluloid, 

a modified form of cellulose. 
Celluvert Fibre. — A variety of insulating 

material. 
Centi. — A prefix for the one hundredth 

part. 
Centi- Ampere. — The hundredth of an 

ampere. 

Centi- Ampere Balance. — An ammeter in 
the form of a balance, capable of measur- 
ing current strengths readily expressed in 
centi-amperes (i. e., from ^ ampere to 
1 ampere). 

Centigrade Thermometer Scale. — A 
thermometer scale in which the length 
of the thermometric tube, between the 
melting point of ice and the boiling point 
of water, is divided into one hundred 
equal parts or degrees. 

Centigramme. — The hundredth of a 
gramme ; or, 0.1543 grains avoirdupois. 

Centilitre. — The hundredth of a litre ; or, 
0.6102 cubic inch. 

Centimetre. — The hundredth of a metre ; 
or, 0.3937 inch. 

Centimetre-Gramme-Second System. 

A system based on the centimetre as the 
unit of length, the gramme as the unit of 
mass, and the second as the unit of time. 

Centimetre-Gramme-Second Units. — 
The units of the centimetre-gramme- 
second system. 

Centipede Cable-Grapnel. — A grapnel 
whose projecting prongs give it an ap- 
pearance somewhat resembling a centi- 
pede. 



Central. — A name given to any central 
telephone exchange or office. 

Central Galvanization. — A variety of 
general galvanization in which the 
cathode is placed over the epigastrium 
and the anode moved over the body. 

Central Lighting-Station.— A station 
where the generators and distributing 
apparatus are placed for producing the 
current which lights the lamps in a given 
district. 

Central-Station Burglar- Alarm. — A 
burglar-alarm whose contacts, situated at 
the place to be protected, are connected 
by suitable circuits with alarms placed in 
a centrally located station. 

Central-Station Lighting.— The lighting 
of a number of houses or other buildings 
from a single centrally located station. 

Central - Station Multiple - Switch- 
Board. — A switchboard employed in a 
central telephone exchange, in which 
each subscriber's jack appears in more 
than a single panel. 

Central Telephone Exchange.— (1) A 
central telephone office connected with 
a plurality of subscribers or telephone 
stations. (2) A central exchange con- 
nected with a plurality of local exchanges. 

Central - Telephone - Exchange Mul- 
tiple-Switchboard. — Any form of 
switchboard employed in a central tele- 
phone exchange, by means of which 
numerous subscribers connected there- 
with can be readily connected to one 
another. 

Centrally Grounded Wire of Railway 
Circuit. — A conductor or wire extending 
along the roadbed, parallel to the rails of 
a pair of tracks, connected to the bond 
wires, and itself grounded at intervals. 

Cement-Lined Conduit.— A conduit of 
wood, stone or metal, the surfaces of 
whose ducts are lined with cement. 

Centre-Pole Trolley Line Construc- 
tion. — A form of aerial line construction 
in which the trolley wires are suspended 
from poles placed in the middle of the 
street or road. 

Centre of Distribution. — In a system of j 
incandescent distribution any point at 
which the supply current is branched or 
radially distributed to mains, to sub- 
mains, or to translating devices. 

Centre of Gravity.— The centre of weight 
of a body. 

Centre of Oscillation.— A point in a body 
swinging like a pendulum, which is 
neither accelerated nor retarded, during 
its oscillations, by the portions of the pen- 



Ceii.] 



711 



[Che. 



dulum that are situated above or below 
it. 

Centre of Percussion.— That point in a 
body, suspended so as to move as a pen- 
dulum, at which a blow perpendicular to 
the radius would produce no pressure 
at the axis. 

Centre-Pole Construction.— In a double- 
track trolley system, especially on broad 
streets, a system of pole construction in 
which poles are placed between the two 
tracks, provided with bracket arms ex- 
tending over each track for the support 
of the trolley wire. 

Centre Railway Line — A trolley line of 
centre-pole construction. 

Centrifugal Force. — That force which is 
supposed to urge a rotating body directly 
away from the centre of rotation. 

Centrifugal Governor. — A device for 
maintaining constant the speed of a steam 
engine or other prime mover, despite 
certain changes in its load or work. 

Centrifuge. — (1) An apparatus for separat- 
ing solids from liquids or liquids of differ- 
ent density from one another by centri- 
fugal forces. (2) A centrifugal separator. 

Centrifuge, Electric. — A centrifuge 
driven by an electromagnetic motor. 

Centripetal. — Seeking the centre. 
Cerebration. — The action of the brain in 

producing thought. 
Chafe. — A weak or worn place in the 

sheathing of a submarine cable due to 

attrition. 

Chafing-Dish,Electric.— An electrically- 
heated chafing dish. 

Chain Cable-Grapnel.— A grapnel whose 
prongs are attached to the links of a 
chain. 

Chain Lightning. — A variety of light- 
ning flash in which the discharge assumes 
a rippling, chain-like appearance. 

Chain Pull. — A pendant chain attached to 
a pendant burner for the movement of 
the wipe-spark spring and the ratchet in 
an electrically-lighted gas-burner. 

Chamber of Incandescent Lamp.— The 
glass bulb or chamber of an incandescent 
lamp provided for maintaining a high 
vacuum, and for the reception of the 
filament. 

Change-Over Switch. — A switch pro- 
vided in a central station for transferring 
a working circuit from one dynamo to 
another, or from one battery of dynamos 
to another. 

Change Ratio of Transformer. — The 
ratio of transformation. 



Changing Switch. — A change - over 

switch. 

Characteristic Curve. — (1) A diagram 
in which a curve is employed to represent 
the relation of certain varying values. 
(2) A curve indicating the characteristic 
properties of a dynamo-electric machine 
under various phases of operation. (3) A 
curve indicating the electromotive force 
of a generator, as a variable dependent on 
the excitation. 

Characteristic Curve of Dynamo.— A 
curve showing the pressure at the ter- 
minals of a dynamo at different field ex- 
citations. 

Characteristics of Sound.— (1) The pe- 
culiarities that enable different musical 
sounds to be readily distinguished from 
one another. (2) The tone or pitch, in- 
tensity or loudness, and the quality or 
timbre of sounds. 

Charge Accumulator.— A xvord some- 
times given to a Leyden jar or condenser. 

Charge Current onTelegraphic Line.— 
The current produced by the initial rush 
of electricity into a telegraph line on the 
closing of the circuit. 

Charge, Electric— The quantity of elec- 
tricity that exists on the surface of an 
insulated electrified conductor. 

Charged Body.— A body containing an 
electric charge. 

Charged' Cell.— A cell of a storage battery 
that has been acted on by a charging cur- 
rent. 

Charging Accumulators or Storage 
Batteries.— Sending an electric current 
into storage batteries or accumulators for 
the purpose of enabling them to act as 
electric sources. 

Charging Current. — The current em- 
ployed in charging a storage battery or 
accumulator. 

Chatterton's Compound.— An insulat- 
ing compound for cementing together the 
alternate coatings of gutta-percha em- 
ployed on a cable conductor, or for filling 
up the space between the stranded con- 
ductors. 

Checking Action. — A term sometimes 
employed for a dampening action. 

Checking Instrument. — An instrument 
in a cable station for recording sending or 
out-going signals on a recorder slip. 

Chemical Affinity. — (1) Atomic attrac- 
tion. (2) The force that causes atoms to 
unite and form molecules. 

Chemical Annunciator.— A term some- 



Che.] 



712 



[Chr, 



times employed for electrolytic annun- 
ciator. 
Chemical Battery. — A name sometimes 
given to a voltaic telegraph battery as 
distinguished from a dynamo. 

Chemical Change. — Any change in mat- 
ter resulting from atomic combination 
and the consequent formation of new 
molecules. 

Chemical Effect.— (1) Any effect occa- 
sioned by atomic combination, in which 
the substances entering into combination 
lose all those properties and peculiar- 
ities by which they are ordinarily recog- 
nized. (2) Atomic combination result- 
ing in the formation of new molecules. 

Chemical Equivalent. — (1) The quotient 
obtained by dividing the atomic weight 
of an elementary substance by its atom- 
icity. (2) The ratio between the quantity 
of an element and the quantity of hy- 
drogen it is capable of replacing. (3) The 
quantity of an elementary substance that 
is capable of combining with or replacing 
one atom of hydrogen. 

Chemical Galvano-Cautery. — A term 
sometimes applied to electro-puncture or 
the application of electrolysis to the treat- 
ment of diseased growths. 

Chemical Generator of Electricity. — 

A term sometimes emphrved in place of a 
voltaic pile or battery. 
Chemical Phosphorescence.— A variety 
of phosphorescence in which ttie emitted 
light is produced by the actual combus- 
tion of a specific chemical substance by 
the oxygen of the air, as in the phosphor- 
escence of the fire-fly, or the glow-worm. 

Chemical Photometer. — A photometer 
in which the intensity of light to be meas- 
ured is determined by the amount of 
chemical action produced in a given time. 

Chemical Potential Energy.— The po- 
tential energy possessed by the element- 
ary chemical atoms. 

Chemical Recording Meter.— A meter 
which records by means of electrolysis 
the quantity of electricity supplied in a 
given time. 

Chemical Separation. — Chemical decom- 
position. 

Chemical Telegraph.— A general term 
for the apparatus employed in chemical 
telegraphy. 

Chemical Telegraphy.— A system of 
telegraphy, in which the dots and dashes 
of the Morse alphabet, or other telegraphic 
code, are recorded on a fillet of moistened 
paper by the electrolytic action of the 



current on some chemical substance with 
which the paper is impregnated. 
Chemical Telephone. — The name given 
to a telephone operating on the principles 
of the electro-motograph. 

Chemical Velocity.— The ratio of the 
amount of substance transformed in any 
chemical process to the time required for 
its transformation. 

Chemism. — A word sometimes employed 
for chemical affinity. 

Chief Operator.— The senior operator on 
duty in a telegraph or telephone office. 

Chimes, Electric— A chime of bells rung 
by the attractions and repulsions of elec- 
trostatic charges. 

Chimney Bracket. — A bracket for sup- 
porting an overhead wire fastened to a 
chimney corner. 

Chloride Storage Cell.— A name given 
to a storage-cell in which the plates are 
formed of grids of antimonious lead, cast 
around pastilles or buttons of fused chlo- 
ride of lead, which, when properly sub- 
jected to the charging current, are con- 
verted into spongy metallic lead and lead 
peroxide, on the negative and positive 
plates respectively. 

Choke Coil. — A name sometimes given to 
a choking coil. 

Choke Magnet. — A word sometimes used 
for choking coil. 

Choking Coil. — A coil of wire so wound 
on a core of iron as to possess high self- 
induction when used on alternating-cur- 
rent circuits. 

Choking Effect. — The effect produced 
by a choking coil in ' obstructing or cut- 
ting off an alternating current with a 
smaller loss of power than would its use 
as a mere ohmic resistance. 

Chord Armature Windings.— (1) Ar- 
mature windings partly formed by chords 
of arcs on the periphery to which they 
are applied. (2) An armature winding 
in which the wire is carried from one 
point on the surface to another along a 
chord of the included arc. 

Chromosphere. — An intensely hot gaseous 
envelope surrounding the central lumin- 
ous nucleus or photosphere of the sun. 

Chronograph, Electric— An electric ap- 
paratus for automatically measuring and 
registering small intervals of time. 

Chronograph Record.— A record ob- 
tained by means of a chronograph. 

Chronometer, Electric— An electrically 
controlled and operated mechanism for 
indicating and recording time. 



Chr.] 



713 



[Cir. 



Chronoscope, Electric— (1) An appa- 
ratus for electrically indicating but not 
measuring small intervals of time. (2) An 
electrically operated device by which 
small intervals of time can be measured. 

Cigar-Lighter, Electric. — An apparatus 
for electrically lighting a cigar. 

Cinematograph.— A biograph. 

Cipher Code. — A code in which a number 
of words or phrases are represented by 
single words, or by arbitrary words or 
syllables. 

Cipher Message. — A code message. 

Circle of Reference. — A circle by refer- 
ence to which simple-harmonic motion 
may be studied by comparison with uni- 
form motion around such circle. 

Circuit Breaker. — Any device for open- 
ing or breaking a circuit. 

Circuit Closer. — Any device for making 
or closing a circuit. 

Circuit-Closer Bell-Pull.— A device, 
suitable for attachment to a mechanical 
door pull, which makes a contact for the 
ringing of an electric bell, without pre- 
venting the original bell from being 
operated by the mechanical pull. 

Circuit, Electric— The path in which 
electricity circulates or passes from a 
given point around or through a conduct- 
ing path back again to its starting-point. 

Circuit Indicator.— A rough form of gal- 
vanometer employed to indicate the pres- 
ence and direction of a current in a cir- 
cuit, and, in some cases, to roughly indi- 
cate its strength. 

Circuit Loop-Break. — A device for in- 
troducing a loop into any part of an 
aerial line circuit. 

Circuit Loop-Break Insulator. — An in- 
sulator employed in a circuit loop-break. 

Circuital. — (1) Of or pertaining to a cir- 
cuit. (2) Flowing or passing in a closed 
circuit. 

Circuital Flux. — (1) A term sometimes 
employed for circular flux. (2) The flux 
surrounding any circuit. (3) Flux com- 
pleting a closed circuit. 

Circuital Gaussage. — The gaussage as 
measured once completely around a 
closed magnetic circuit. 

Circuital Vector. — A vector quantity 
which does not terminate in space but 
forms a closed curve or endless chain. 

Circuital Voltage. — The voltage as meas- 
ured around a closed circuit. 

Circuitation. — The line integral of a 
vector quantity taken around a circuit. 



Circular Bell. — A term sometimes applied 
to a bell so constructed that all of its 
moving parts are contained in the gong. 

Circular Current.— A current flowing 
through a circular path. 

Circular Flux.— (1) A term sometimes 
employed for the concentric circular flux 
which surrounds an active cylindrical 
wire or conductor. (2) Generally, cir- 
cuital flux. 

Circular Magnetic Flux.— Circular flux. 

Circular Magnetism.— (1) The magnet- 
ism of a cylindrical rod of iron or steel one 
of whose poles extends circumferentially 
around the rod while the other pole is 
situated at and around its centre. (2) A 
circular distribution of magnetic flux. 

Circular Magnetization.— The magnet- 
ization producing circular magnetism. 

Circular Mil. — (1) A unit of area employed 
in measuring the cross-section of wires, 
equal, approximately, to 0.7854 square 
mils. (2) The area of a circle one mil in 
diameter. 

Circular Millage. — The areas of cross- 
sections of wires or conductors expressed 
in circular mils. 

Circular Scratch Brush.— A scratch 
brush of circular shape, suitable for 
being set in rapid rotation by a lathe. 

Circular Touch.— A method of magnet- 
ization by touch in which four bars are 
placed in the form of a rectangle and the 
magnetizing magnet is placed in contact 
at any point, drawn around the rectangle 
a number of times, and removed at the 
point where its motion began. 

Circular Type of Periodically Alter- 
nating E. M. F. — A periodically alter- 
nating E. M. F. having a curve whose 
values in different parts of a cycle are 
such that when plotted in a curve they 
will produce a circular outline. 

Circular Units of Area. — Various units 
employed for measuring areas of cross- 
section by reference to the area of a unit 
circle, such, for example, as the circular 
mil. 

Circulating Power. — A term employed 
by Hopkinson for the method of taking 
power out of a machine as a motor and 
utilizing this power to drive the generator 
with which it is connected. 

Circumferential Speed.— The speed of 
any point on the circumference of a ro- 
tating wheel or armature. 

Circumnux. — A term sometimes employed 
for the product of armature current and 
the total number of armature conductors 
divided by the number of poles. 



Cla.] 



714 



[Clo. 



Clamp for Are Lamps.— (1) A device for 
gripping the lamp rod of an arc-lamp. 
(2) The carbon clutch or clamp of an arc- 
lamp. 

Clamp Splicing-Ear.— A trolley splicing 
ear in which the two ends of the wire are 
placed in the jaws of a clamp and then 
pressed together and secured by a bolt. 

Clamp Terminals.— Simple screw-clamps 
serving as terminals for connecting the 
ends of flexible cords or other wires. 

Clark Element. — A name sometimes 
given to a Clark standard voltaic cell. 

Clark's Compound.— A bituminous and 
siliceous compound employed on the 
outer casing of the sheathing of a sub- 
marine cable. 

Clark's Standard Voltaic Cell.— A form 
of zinc-mercury couple employed, in con- 
nection with electrolytes of mercurous 
sulphate and zinc sulphate, as a standard 
cell. 

Clay Electrode. — A therapeutic electrode 
of clay shaped so as to fit the part of the 
body to be treated. 

Clearance. — The gap space between the 
surface of a rotating armature and the 
opposed polar surface of the field magnets 
of a dynamo or motor. 

Clearance Space. — The clearance. 

Clearing. — In telephony, the operation of 
disconnecting subscribers who have been 
in connection, and restoring the lines to 
their normal conditions. 

Clearing-Out Drops. — (1 ) Electro-mag- 
netic drop-shutters placed in a telephone 
exchange in circuit with a pair of com- 
municating subscribers, so that the fall- 
ing of the shutter when they " ring off" 
indicates that the conversation is ended. 
(2) Ring-off drops. 

Clearing-Out Relays. — Relays provided 
for operating clearing-out drops. 

Clearing Signal.— (1) A ring-off signal. 
(2) A signal in a telephone exchange to 
indicate that a telephonic conversation 
has ended. 

Cleat Wiring. — Placing or establishing 
electric conductors or wires on walls or 
ceilings by means of suitably shaped in- 
sulating cleats. 

Cleat, Electric. — A suitably shaped piece 
of wood, porcelain, hard-rubber or other 
non-conducting material used for fasten- 
ing and supporting electric conductors to 
ceilings and walls. 

Cleavage Electricity. — Electrification 
produced by the cleavage of crystalline 
substances. 



Clepsydra, Electric— An instrument for 
measuring time by the escape of water or 
other licmid under electric control. 

Click Wire. — (1) A wire of a multiple 
telephone switchboard employed for the 
engaged test, by which a click is heard 
in the operator's telephone when the sub- 
scriber asked for is busy. (2) The busy 
test wire. 

Clip. — A slight break in signalling where- 
by a signal is unduly shortened, that is 
likely to occur with an imperfect adjust- 
ment of duplex orquadruplex telegraphy. 

Clip Switch.— A switch in which the 
switch-lever enters the base of a clip. 

Clipping of Telegraphic Signal.— The 
curtailing of a telegraph signal due to 
defective adjustments or to disturbances 
on the line. 

Clock, Electric— A clock the works of 
which are moved, controlled or regulated, 
either entirely or partially, by the electric 
current. 

Clock Meter.— An electric meter in which 
clock-work is employed. 

Clock Register. — A register employed 
in connection with a clock for recording 
the time of an occurrence. 

Clockwise Motion.— A rotary motion 
whose direction is the same as that of the 
hands of a clock, viewed from the face. 

Clockwork Feed for Arc Lamps.— An 
arc-lamp mechanism in which one or both 
carbons are fed by trains of wheel 
work. 

Closed Car-Wheel.— A car-wheel in 
which the portion of the wheel between 
the flange and the axle is formed of an 
imperforate mass. 

Closed Circuit. — A completed circuit. 

Closed - Circuit Burglar- Alarm.— A 
burglar alarm that is normally on closed 
circuit, and which operates on the open- 
ing of the circuit by the opening of the 
contacts. 

Closed-Circuit Signalling.— A system 
of single-circuit signalling in which the 
sending batteries are placed at each end 
of the line and are so connected as to 
remain always in circuit. 

Closed-Circuit Thermostat.— A ther- 
mostat maintained normally on closed 
circuit. 

Closed-Circuit Transformer.— A term 
sometimes employed for closed iron-cir- 
cuit transformer. 

Closed-Circuit Voltaic Cell or Bat- 
tery. — A voltaic cell or battery that can 
be left for a considerable time on a closed 



Clo.] 



715 



[Cod, 



circuit of comparatively small resistance 
without serious polarization. 

Closed-Circuit Voltmeter. — A volt- 
meter intended to be in permanent con- 
nection with the pressure it is designed 
to measure. 

Closed-Circuited. — Placed in a closed or 
completed circuit. 

Closed-Circuited Conductor. — A con- 
ductor connected in a closed or completed 
circuit. 

Closed-Circular Current. — A current 
flowing in a circular circuit. 

Closed-Circular Solenoid.— A circular 
solenoid closed upon itself so as to form a 
tore. 

Closed-Coil Armature.— (1) An armature 
the coils of which are never on open cir- 
cuit during rotation. (2) A dynamo ar- 
mature whose coils are grouped in sec- 
tions and connected with successive bars 
of a commutator, so as to be continuously 
connected together in a closed circuit. 

Closed-Coil Winding. — Any winding 
by which the armature coils are connect- 
ed in closed circuit during the operation 
of the machine. 

Closed-Conducting Sheath for Light- 
ning Protector.— A method for light- 
ning protection consisting in forming a 
wire-sheathing or netting around the ob- 
ject to be protected. 

Closed Iron -Circuit Transformer.— 
(1) A transformer, the core of which forms 
a completed magnetic circuit. (2) An 
iron-clad transformer. 

Closed Iron - Magnetic Circuit. — A 
magnetic* circuit all of whose path is 
completed by iron. 

Closed Loop. — A single loop of wire or 
conductor placed on a closed circuit. 

Closed - Loop Parallel - Circuit. — A 
variety of parallel circuit in which both 
the leading and returning conductors form 
closed loops, between which the trans- 
lating devices are bridged. 

Closed Magnetic Circuit.— A magnetic 
circuit which lies wholly in iron or other 
substance of high magnetic permeability. 

Closed Magnetic Circuit of Atom. — A 
closed magnetic circuit whose flux is 
supposed to lie entirely within the atom. 

Closed-Magnetic Circuit of Molecule. 
A closed magnetic circuit assumed to 
lie wholly within the molecule. 

Closed Magnetic Core. — A magnetic 
core so shaped as to provide a complete 
iron path or circuit for the magnetic flux 
of its field. 



Closet System of Parallel Distribu- 
tion. — A system of parallel distribution 
and house wiring in which the various 
receptive devices are collected in groups 
each of which is supplied with a separate 
and independent supply circuit back to 
the service ; as distinguished from a tree 
system. 

Closed Trolley Car.— A trolley car en- 
closed from the outer air as distinguished 
from an open or summer car. 

Closure. — The completion of an electric 
circuit. 

Clown's Hat Curve. — A curve of current 
or electromotive force in which the pres- 
sure generated increases or decreases at 
a rapid rate of change, and whose 
shape is somewhat similar to the shape of 
a peaked hat or a clown's hat. 

Club - Footed Electro-Magnet. — An 
electro-magnet whose core is in the form 
of a horse-shoe and is provided with a 
magnetizing coil on one pole only. 

Cluster Call. — A globe of metal from 
which a cluster of incandescent lamps 
radiate. 

Clutch for Arc Lamps. — A carbon 
clutch or clamp for arc lamps. 

Clutching Device.— (1) Any device em- 
ployed for clutching or holding the car- 
bons in an arc-lamp. (2) A device for 
clutching or holding any object subjected 
to occasional motion. 

Coarse Winding of Field Magnets.— 
The series-winding of a compound-wound 
machine. 

Co-acting. — Acting simultaneously or to- 
gether. 

Coating. — An adherent layer or covering. 

Coating of Condenser. — A sheet of tin 
foil placed on one side of a Leyden jar or 
condenser, directly opposite a similar sheet 
on the other side, for the purpose of 
receiving and collecting an electric 
charge. 

Coatings of Leyden Jar. — The sheets of 
tin foil or other conductor placed on op- 
posite sides of a Leyden jar or condenser. 

Code Name. — In telegraphy, the symbol, 
word, or group of letters, standing for, 
or representing the name of some person, 
association, or thing, according to a pre- 
arranged code. 

Code or Coded Telegraphy.— A system 
of telegraphy employed for sending de- 
spatches in which the time required for 
transmitting is considerably decreased 
by employing code words instead of the 
actual words of the message. 



Cod.] 



716 



[Coi. 



Coded Telegraph Messages or Code 

Messages. — Messages that are sent by 
the use of prearranged words, any one of 
which may stand for a group of words, 
a phrase, or a complete sentence. 

Code Time. — In telegraphy, the code sig- 
nals in the preamble of a message which 
signify and indicate the time at which the 
message was received for transmission. 

Coefficient of Electro-Magnetic Iner- 
tia. — A term sometimes employed in 
place of the coefficient of inductance or 
self-inductance of a circuit. 

Coefficient of Expansion.— The frac- 
tional increase in the length of a bar or 
rod. when heated from 32 to 33 degrees 
Fahr. , or from to 1 degree Cent. 

Coefficient of Hysteresis.— (1) The work 
expended hysteretically in a cubic-centi- 
metre of iron, or other magnetic substance, 
in a single cycle of unit magnetic flux 
density. (2) The coefficient which multi- 
plied by the volume of iron, the frequency 
of alternation, and the l-6th power of the 
maximum flux density gives the hyster- 
etic activity. 

Coefficient of Inductance.— (1) A con- 
stant quantity such that, when multiplied 
by the current strength passing through 
any coil or circuit, will numerically rep- 
resent the flux linkage with that coil or 
circuit due to that current. (2) A term 
sometimes used for coefficient of self-in- 
duction. (3) The ratio of the C. E. M. F. 
of self-induction in a coil or circuit to 
the time-rate-of-change of the inducing 
current. 

Coefficient of Induction.— A term some- 
times used for coefficient of magnetic in- 
duction. 

Coefficient of Magnetic Induction.— 

(1) A term sometimes used instead of 
magnetic permeability. (2) The ratio 
between the quantity of magnetic flux 
that passes through any area of normal 
cross-section of a magnetic circuit and 
the magnetizing force producing that 
flux. 

Coefficient of Magnetic Leakage.— 

(1) The ratio of the flux through a leakage 
path to the flux through an armature. 

(2) The ratio of the mutual induction in 
a transformer as reduced by magnetic 
leakage to the mutual induction in the 
absence of magnetic leakage. 

Coefficient of Magnetization. — A num- 
ber representing the intensity of magneti- 
zation produced in a magnetizable body 
divided by the magnetizing force, and 
usually represented by the symbol «. 



Coefficient of Mutual Inductance.— 

(1) The ratio of the electromotive force 
induced in a circuit to the rate-of-change 
of the inducing current in a magnetically 
associated circuit. (2) The ratio of the 
total flux-linkage with a circuit proceed- 
ing from an associated inducing circuit, 
to the strength of current flowing in the 
latter. 

Coefficient of Mutual Induction.— The 

coefficient of mutual inductance. 

Coefficient of Potential.— (1) A co- 
efficient w T hich multiplied into the charge 
of a body gives its potential. (2) The ratio 
of the potential of an electrified body to 
its charge, when all neighboring bodies 
are uncharged. 

Coefficient of Reflection.— The percent- 
age value expressing the ratio of the 
intensity of the reflected ray to the in- 
tensity of the incident ray. 

Coefficient of Self-induction.— (1) Self- 
inductance. (2) The ratio in any circuit 
of the flux induced by and linked with a 
current, to the strength of that current. 
(3) The ratio in any circuit of the E. M. 
F. of self-induction to the rate-of-change 
of the current. 

Coercitive Force. — A name sometimes 
employed for coercive force. 

Coercive Force. — (1) The power of resist- 
ing changes in magnetization. (2) In 
cyclic magnetization the demagnetizing 
force which must be applied to a mag- 
netic substance in order to completely 
demagnetize it- 

Coherer. — A detector of electro-magnetic 
waves consisting of conducting particles 
forming a semi-conducting •bridge be- 
tween two electrodes. 

Coil and Plunger for Electro-Magnet. 
A movable iron core which is attracted 
into a hollow coil or solenoid when a cur- 
rent passes through said coil. 

Coil, Electric. — (1) A convolution of insu- 
lated wire through which an electric 
current may be passed. (2) A number of 
turns of wire, or a spool of wire, through 
which an electric current may be passed. 

Coil-Heater, Electric. — A heater whose 
heat is obtained by the passage of an 
electric current through a suitably sup- 
ported coil of wire. 

Coil Winding. — Loop or lap winding. 

Coil Winding of Alternator.— (1) A 

form of winding applied to the armature 
of an alternator in which the wire is 
made into coils that are laid upon the 
surface of the armature core. (2) A term 
sometimes used for loop winding. 



Coi.] 



717 



[Com, 



Coiling Space of Cable Tank.— The 
space provided in a cable tank for the re- 
ception of a cable. 

Coked Core of Incandescent Filament. 
An incandescent lamp filament formed 
of a core of electrically coked carbon 
whose surface is covered with a deposit 
of carbon by the flashing process. 

Coked Filament. — A carbon filament for 
an incandescent lamp that has been so sub- 
jected to electrical heating in a vacuum 
as not only to be thoroughly freed from 
its occluded gases but also to have its car- 
bon changed into a variety of coke. 

Coking, Electric. — Subjecting carbon to 
the coking process. 

Coking of Filament.— Subjecting a fila- 
ment to the coking process. 

Coking Process for Filament of In- 
candescent Lamp. — A process for 
converting the carbon of an incandescent 
filament into coke by subjecting it, while 
in a vacuum, to the prolonged heating 
action of a powerful electric current. 

Cold Light. — (1) Luminous radiation 
unaccompanied by obscure radiation. 
(2) Radiation confined within the limits of 
the visible spectrum. (3) The light of a 
fire-fly or glow-worm. 

Collapsing Drum. — A visual-signal drum 
capable of manual distension and collapse. 

Collation. — The repetition of a message or 
important parts of the same by an oper- 
ator at a telegraph station who has re- 
ceived it over the line, to the transmitting 
operator at the sending station. 

Collecting Ammeter— An ammeter in a 
central station which collects, and, there- 
fore, indicates the total current received 
from two or more separate generators, 
and usually employed to indicate the total 
current output of a station. 

Collecting Brushes of Dynamo-Elec- 
tric Machine. — Conducting brushes 
which bear on the commutator cylinder 
of a dynamo and carry off the current 
generated by the E. M. F. in the armature 
coils. (2) The brushes which bear on 
the collecting rings of an alternator 
armature. 

Collecting Combs. — The collecting points 
of a frictional electric machine, or of an 
electrostatic induction machine. 

Collecting Panel. — A panel in a switch- 
board which collects all the current sup- 
plied by the generators connected to that 
switchboard. 

Collecting Rings for Alternators.— 
Metallic rings connected with the ter- 
minals of the armature coils of an alter- 



nator on which brushes rest to carry off 
the alternating currents. 
Collectors, Electric— Devices employed 
for collecting electricity from a moving 
electric source. 

Collectors of Alternators.— The collect- 
ing rings. 

Collectors of Dynamo-Electric Ma- 
chine. — The brushes that rest on the 
commutator cylinder and carry off the 
current generated on the rotation of the 
armature. 

Collectors of Frictional Electric Ma- 
chine. — The metallic points that collect 
the charge from the glass plate or cylin- 
der of a frictional electric machine. 

Colloids. — One of the two classes into 
which substances are separated by dial- 
ysis. 

Colombin. — An insulating substance con- 
sisting of a mixture of sulphates of barium 
and calcium placed between the parallel 
carbons of the Jablochkoff candle. 

Column, Electric— A term formerly ap- 
plied to a voltaic pile. 

Colza Oil. — The oil employed in the Carcel 
standard lamp. 

Comazant. — (1) A term formerly applied 
to a St. Elmo's fire. (2) A corposant. 

Collector Rings. — The collecting rings 
of an alternator. 

Comb Lightning-Arrester. — A form of 
lightning-arrester in which the line wires 
are connected to two metallic plates pro- 
vided with serrations like the teeth of a 
comb, and placed near to another ground- 
connected plate, which may or may not 
be furnished with similar serrations. 

Comb of Storage Battery .—The grid of 
a storage battery. 

Comb Protector. — A comb lightning-ar- 
rester. 

Combination Anchor-Poles.— (1) An 
anchor pole intended for the support of 
both aerial wires and aerial cables. (2) A 
composite anchor-pole. 

Combination Bracket. — (1) A bracket 
for supporting a pair of insulators side by 
side'. (2) A bracket for supporting both 
a gas lamp and an incandescent lamp. 

Combination Fittings for Chandeliers. 
Fittings that provide for the use of both 
gas and electricity. 

Com bination Gas-Fixtures.— Combina- 
tion fittings. 

Combination Lightning-Protector.— 
A form of combined film and fuse light- 
ning-protector employed on telephone 



€om.] 



718 



[Com, 



circuits, arranged so as to ground the cir- 
cuit either under the action of high pres- 
sures, or under the action of an unduly 
strong current. 

Combination Line-Protector. — A corn- 
bin ation lightning-protector. 

Combination Protector. — A combination 
lightning-protector. 

Combination Rheostat. — A form of box 
rheostat, or resistance box, which con- 
tains within its cover several separate 
series of resistance coils. 

Combination Triphase- Winding. — A 

triphase winding combining both the star 
winding and the triangular winding. 

Combined Fibre and Spring Suspen- 
sion. — A suspension of a needle by the 
combined use of a spiral spring and a 
single fibre. 

Combined Tangent and Sine Galvano- 
meter. — A galvanometer furnished with 
two magnetic needles of different lengths, 
one a small needle for tangent measure- 
ments, and the other a long needle for 
sine measurements. 

" Come Along." — A small portable vise 
capable of ready attachment to an aerial 
telegraph or telephone cable, and used in 
connection with a line dynamometer to 
pull up the wire to its proper tension. 

Commercial Efficiency.— The useful or 
available energy produced by any ma- 
chine or apparatus divided by the total 
energy it absorbs. 

Commercial Efficiency of Dynamo, or 
Generator. — The ratio of the output of 
a dynamo, or the useful and available 
electric energy delivered at its terminals, 
divided by its intake, or the mechanical 
energy required to drive it. 

Commercial Efficiency of Motor.— The 

ratio between the mechanical activity 
developed at a motor pulley and the elec- 
tric activity absorbed at its terminals. 

Common Are of Aurora Glory.— The 
inner or common arc of an aurora glory. 

Common Return. — A return conductor 
common to several circuits. 

Common Side of Quadruplex System. 

In quadruplex telegraphy, the neutral or 
No 2. side, as distinguished from the polar 
or No 1. side. 

Communicator, Electric. — A term for- 
merly employed for a telegraphic key. 

Commutating Machine.— A rotary 
transformer. 

Commutation. — The act of commuting or 
causing a number of electromotive forces 



or currents to take one and the same 
direction. 

Commutation Fringe. — A term em- 
ployed for the induction produced by an 
edge or fringe of the magnetic flux at the 
pole tip, under which commutation takes 
place. 

Commutator.- -(1) Any device for chang- 
ing in one portion of a circuit the direc- 
tions of electromotive forces or currents 
in another portion. (2) A device for 
changing alternating into continuous 
currents, or vice versa. 

Commutator. — A name sometimes given 
to a universal switch or pin switchboard. 

Commutator Bar.— One of the insulated 
segments of a commutator. 

Commutator Coils. — Coils wound around 
an armature core for the purpose of pre- 
venting sparking, connected at one of 
their ends to the main windings at points 
between the coil sections, and at the 
other end to the commutator segments. 

Commutator Motor.— An alternating- 
current motor in which the armature is 
provided with a commutator. 

Commutator of Dynamo-Electric Ma- 
chine. — The device employed to cause 
the electromotive forces generated in an 
armature, on its rotation in the magnetic 
field, to take one and the same direction 
externally. 

Commutator Press Button.— A press 
button employed in a system of telephony, 
at a subscribers' station, for calling the 
central station by reversing a battery. 

Commutator Segments or Strips.— The 
insulated bars of a commutator. 

Commutatorless.— Devoid of a commu- 
tator. 

Commutatorless Contin uous-Current 
Dynamo. — (1) A dynamo that furnishes 
continuous currents without the aid of a 
commutator. (2) The so-called unipolar 
dynamo. 

Commuted. — Caused to take one and the 
same direction. 

Commuted Currents or Electromotive 
Forces. — Currents or electromotive 
forces that have undergone commutation. 

Commuted Magneto-Generator.— A 

magneto-generator whose currents are 
commuted. 

Commutated.— Commuted. 

Commutating.— Commuting. 

Commuting.— Changing direction. 

Commuting Transformer.— A rotary 
commutator. 



Com.] 



719 



[Com, 



Companion Loops.— A pair of telegraphic 
loop-circuits, connecting a pair of branch 
offices with the main office, in which there 
is a duplex set, so connected therewith, 
that the instruments at the branch offices 
are made the virtual duplex instruments 
of the main station ; one branch office 
sending while the other is receiving. 

Comparator. — An apparatus for compar- 
ing standards of lengths or gauges. 

Compartment Man-Hole of Conduit. 

A man-hole provided with suitably sup- 
ported shelves or compartments that pro- 
tect different cable sections. 

Compass. — A mariner's compass. 

Compass Card. — A card used in a mari- 
ner's compass on which are marked the 
four cardinal points of the compass ; 
North, South, East and West, and again 
sub-divided into 32 points called rhumbs, 
and also frequently divided circumferen- 
tially into degrees. 

Compass Sights. — Small holes or narrow 
slits made in opaque plates, affixed to the 
compass box, for use in taking bearings. 

Compensated Alternator.— An alterna- 
tor employed for sustaining a uniform 
voltage at some point of its circuit under 
varying loads, whose field magnets are 
excited partly by constant currents taken 
from a separate generator, and partly by 
currents supplied by the load current in 
the armature. 

Compensated Excitation of Alterna- 
tor. — The excitation of an alternating- 
current dynamo whose field is partly sep- 
arately excited, and partly excited from 
the main circuit of the machine. 

Compensated Galvanometer.— A dif- 
ferential galvanometer for indicating 
pressure at a distant point of a continu- 
ous-current circuit, having one coil in 
shunt and the other in series with said 
circuit. 

Compensated Meter-Bridge. — A meter- 
bridge so arranged that its indications 
are compensated for the effects of tem- 
perature. 

Compensated Resistance-Coil.— A re- 
sistance-coil so arranged as to be compen- 
sated for the effect of temperature upon 
its resistance. 

Compensated System of Currents. — 
In telegraphy with the Wheatstone auto- 
matic apparatus, a system of double-cur- 
rent signalling in which both the initial 
and final currents are weakened before 
removal by the interposition of a resist- 
ance in the battery circuit. 

Compensated Voltmeter.— A central- 



station voltmeter connected to the bus- 
bars in such a manner that its indications 
are automatically corrected for the drop of 
pressure in some particular feeder or group 
of feeders, so that its readings correspond 
to the pressure supplied to the mains. 

Compensated Wattmeter.— A watt- 
meter so wound as to be compensated for 
the effect of reactance in its shunt circuit. 

Compensated Coils. — A term sometimes 
applied to the series Coils placed on a 
shunt- wound machine. 

Compensated Condenser. — A condenser 
employed in duplex telegraphy to give to 
the artificial line a static capacity equal 
to that of the main line. 

Compensated Potential-Indicator.— A 

compensated voltmeter. 

Compensating Line. — An artificial line 
employed in duplex telegraphy. 

Compensating Magnet. — A magnet 
placed over a galvanometer or other 
needle, for the purpose of varying the di- 
rection and intensity of the earth's mag- 
netic force on such needle. 

Compensating Pole. — A small bar elec- 
tro-magnet, or electro-magnetic coil, 
placed perpendicularly between the pole- 
pieces of a dynamo to compensate for the 
cross magnetization of the armature cur- 
rents. 

Compensating Wire. — In a system of 
differential duplex telegraphy, the arti- 
ficial line or wire, as distinguished from 
the real line or wire. 

Compensation Photometer.— (1) A pho- 
tometer in which the illumination of the 
two parts of the photometer screen is 
equalized by diminishing the intensity of 
the pencil of light by polarization. (2) A 
polarization photometer. 

Compensator. — An auto-transformer. 

Compensator for Alternating-Current 
Lamps. — A choking coil or compensator, 
placed in circuit with the lamps in an 
alternating-current circuit, for the pur- 
pose of automatically regulating the cur- 
rent strength in the lamps. 

Compensator System.— A system of al- 
ternating-current electric distribution 
from high-pressure mains to low-pressure 
translating devices, in which the latter 
are connected in derived circuits between 
sections of choking coils connected across 
the mains. 

Complement of Angle.— What an angle 
lacks to make its value equal to 90°, or 
a right angle. 

Complete Fault.— Any fault which com- 
pletely interrupts telegraphic or telephon- 



Com.] 



720 



[Com, 



ic communication as distinguished from a 
partial fault. 

Complete Wave.— (1) Two successive al- 
ternations, or a double alternation of a 
periodically-alternating quantity. (2) A 
cycle. 

Completed Circuit.— (1) A closed cir- 
cuit. (2) A circuit whose conducting 
continuity is unbroken. 

Completing a Circuit.— Closing a circuit. 

Complex Distribution of Lamellar 
Magnetism. — A distribution of the mag- 
netism of a finite magnet into an infinite 
number of complex-magnetic shells. 

Complex-Harmonic Motion. — Motion 
resulting from the superposition or co- 
action of a plurality of simple-harmonic 
motions. 

Complex-Harmonic Alternating E. M. 

F.s. — Electromotive forces resulting 
from the combination of a fundamental- 
harmonic electromotive force and its 
harmonics. 

Complex-Harmonic Currents. — Cur- 
rents produced by complex-harmonic 
electromotive forces. 

Complex - Harmonic Electromotive 
Forces. — Complex-harmonic alternating 
electromotive forces. 

Complex-Magnetic Shell.— (1) A mag- 
netic shell whose strength varies from 
one part to another of its surface. (2) A 
distribution of magnetization equivalent 
to an association or superposition of a 
number of separate magnetic shells of 
arbitrary strength and area. 

Complex Quantities.— Any quantity 
made up of two parts, one of which is 
measured along an axis of reference, and 
the other in a direction at right angles to 
such axis, these axes being sometimes 
described as the real and imaginary axes 
respectively. 

Component. — One of the two or more 
separate forces into which any single 
force may be resolved ; or, conversely, the 
separate forces which together produce 
any single resulting force. 

Component Currents. — The two or more 
currents into which it may be conceived 
that a single current may be divided so 
as to be the equivalent* of that single 
current. 

Component Electromotive Forces.— 
The two or more E. M. F.s into which 
any given E. M. F. may be resolved. 

Component Inductions. — The two or 
more inductions into which any given 
magnetic flux may be resolved so as to be 
its equivalent. 



Components of Impedance.— The ener- 
gy component or effective resistance, and 
the wattless component or effective re- 
actance. 

Composite Anchor-Pole. — A combina- 
tion anchor-pole. 

Composite Balance.— A balance with two 
pairs of fixed coils of coarse and fine wire 
respectively, employed for measuring 
strong or feeble currents as desired. 

Composite Dynamo.— A compound- 
wound dynamo. 

Composite Excitation.— Any excitation 
of the field magnets of a dynamo in which 
more than a single winding is employed, 
such as a shunt and a series winding. 

Composite Field.— The field of a com- 
positely-excited dynamo. 

Composite-Field Dynamo.— (1) A dy- 
namo whose field has a composite excita- 
tion. (2) A dynamo whose field is com- 
pound wound. 

Composite Grid. — A storage-battery grid 
made of a number of sheets of lead foil 
covered with graphite, placed between 
two plates of sheet lead which are held 
together with lead rivets. 

Composite Horse-Shoe Magnet.— A 

compound horse-shoe magnet. 
Composite Kilo-Ampere Balance.— A 

balance form of ammeter, provided with 
coarse and fine windings, so arranged that 
the instrument will serve as a kilo-ampere 
meter, as a centi-ampere meter, or, as a 
voltmeter. 
Composite Wire.— (1) A wire provided 
with a steel core and an external copper 
sheath, possessing sufficient tensile 
strength to enable it to be used in long 
spans without excessive sagging. (2) A 
bimetallic ware. 

Compositely-Excited Dynamo.— (1) A 

compound-wound dynamo. (2) A com- 
posite-field dynamo. 
Composition of Forces.— Finding the 
direction, and intensity of a single force 
which represents the total effect of two 
or more forces that are acting simultane- 
ously on a body. " 

Compound. — An asphaltic composition 
employed in the sheathing of submarine 
cables. 

Compound Alternator.— A compound- 
wound alternator. 

Compound Arc. — An arc formed of more 
than two separate electrodes. 

Compound Battery.— A term formerly 
employed for a battery of voltaic cells, as 



Com.] 



721 



[Con, 



contradistinguished from a single cell. 
(Obsolete.) 

Compound Cable.— A multiple-core cable. 

Compound Circuit. — A circuit contain- 
ing more than a single source, or more 
than a single electro-receptive device, or 
both. (Not in general use.) 

Compound Condenser.— (1) A name 
sometimes given to subdivided condenser. 
(2) A composite condenser. 

Compound Electro-Magnet.— A word 
formerly employed for an electro-magnet 
consisting of an iron core wound with 
two or more separate magnetizing cir- 
cuits. (Not in general use.) 

Compound Magnet.— A number of single 
magnets placed parallel, side by side, 
and with their similar poles adjacent. 

Compound Radical. — (1) A group of un- 
saturated atoms. (2) A group of elemen- 
tary atoms some of whose bonds are in- 
terconnected or joined with the bonds of 
other atoms. 

Compound Receiver. — A telephone re- 
ceiver employed by an operator at a 
central station, and composed of two 
separate telephone receivers united into 
one common frame or receptacle with a 
single ear-piece, for the purpose of afford- 
ing a separate distinct circuit and dia- 
phragm, independently of the speaking 
circuit and diaphragm. 

Compound Telegraph-Wire.— A bi- 
metallic telegraph wire. 

Compound Winding.— A method of 
winding dynamos or motors in which 
both shunt and series coils are placed on 
the field magnets. 

Compound - Wound.— (1) Having asso- 
ciated shunt and series windings. 
(2) Compositely wound. 

Compound-Wound Alternator.— An 
alternator whose fields are compound- 
wound. 

Compound-Wound Continuous-Cur- 
rent Generator. — A continuous-current 
generator whose fields are compound- 
wound, for the purpose of maintaining 
the pressure constant under all loads. 

Compound- Wound Field.— A field pro- 
vided with compound windings. 

Compound-Wound Motor.— A motor 
whose field is compound wound, for the 
purpose of maintaining its speed constant 
under all loads. 

Compound- Wound Voltmeter. — (1) A 

compensated voltmeter. (2) A voltmeter 
having more than one winding. 
Concealed Wiring. — Interior wiring 
46 



placed out of sight, and either built in 
the plaster of a room or carried through 
suitable conduits placed therein. 
Concentration of Lines of Force.— 
Any increase in the intensity of a mag- 
netic flux. 

Concentration Throw.— The deflection 
of a magnetic needle by a current, pro- 
duced under certain circumstances by a 
couple formed of plates or iron or other 
paramagnetic metal, when exposed to 
chemical action while in a magnetic field. 

Concentric Cable.— (1) A cable provided 
with both a leading and return conductor 
insulated from each other, and forming 
respectively the central core or conductor, 
and the enclosing tubular conductor. 
(2) A cable having concentric conductors. 

Concentric-Carbon Electrodes.— Con- 
centric-carbon electrodes employed in a 
modified form of Jablochkoff candle. 

Concentric Conductors. — Cylindrical 
coaxial conductors insulated from each 
other. 

Concentric-Cylindrical Carbons. — A 
cylindrical rod of carbon placed inside a 
hollow cylinder of carbon, but separated 
from it either by an air space, or by some 
refractory insulating material, employed 
in a form of Jablochkoff candle. 

Concentric Mains.— Mains employing 
concentric cables. 

Concentric Wiring.— Wiring by means 
of concentric cables. 

Condensance. — Capacity reactance. 

Condenser. — (1) A device for increasing 
the capacity of an insulated conductor 
by bringing it near another earth- 
connected conductor but separated there- 
from by any medium that will permit 
electrostatic induction to take place 
through its mass. (2) Any variety of 
electrostatic accumulator. 

Condenser Capacity .—The capacity of a 
condenser. 

Condenser Circuit.— Any circuit in which 
a condenser is inserted. 

Condenser Lightning- A r r e s t e r.— A 
form of lightning arrester whose opera- 
tion depends on the connection of a con- 
denser with some part of the circuit to be 
protected. 

Condenser Pressure. — The difference of 
potential at the terminals of a condenser. 

Condenser Rheostat. — A rheostat in the 
circuit of a condenser in an artificial 
line of a duplex or quadruplex system. 

Condenser Signalling.— Any form of 



Con.] 



722 



[Con, 



telegraphic or telephonic signalling in 
which condensers are employed. 

Condenser Working. — Condenser signal- 
ling. 

Condensing Electroscope.— An electro- 
scope provided with a condenser for 
the purpose of rendering evident feeble 
charges. 

Conduct. — (1) To pass electricity through 
conducting substances. (2) To carry, or 
to possess the power of carrying, an elec- 
tric current. 

Conductance. — (1) A word sometimes 
used in place of conducting power. 

* (2) The reciprocal of resistance. (3) In 
a continuous-current circuit the ratio of 
the current strength to the E. M. F. 
(4) In an alternating-current circuit the 
quantitj r whose square added to the square 
of the susceptance is equal to the square 
of the admittance. 

Conductance, Electric— Conducting 
power for electricity. 

Conductance Leak. — A leak in a cable or 
circuit produced by conduction as dis- 
tinguished from a leak possessing induc- 
tion. 

Conductibility.— (1) Possessing the 
power of conducting electricity. (2) Con- 
ductivity. 

Conducting Cord. — A small insulated 
flexible cable usually consisting of a 
stranded conductor or conductors. 

Conducting Cord Tip.— A blunted or 
rounded conductor placed at one of the 
ends of a cord or wire for the purpose of 
readily inserting it into a binding post or 
into a plug hole. 

Conducting Loop. — A loop of wire or 
other electric conductor. 

Conducting Power.— The ability pos- 
sessed by a given length and area of 
normal cross-section of a substance for con- 
ducting light, heat, electricity, or mag- 
netism, as compared with that possessed 
by an equal length and area of normal 
cross-section of some other substance 
taken as a standard. 

Conducting Power for Electricity.— 

The ability possessed by a given length 
and area of normal cross-section of a sub- 
stance to conduct electricity, as compared 
with that possessed by an equal length 
and area of normal cross-section of some 
other substance taken as a standard, 
such, for example, as pure copper. 

Conducting Power for Heat.— The 
ability possessed by a substance to trans- 
mit heat through its mass. 



Conducting Power for Lines of Mag- 
netic Force.— (1) Permeability. (2) In- 
ductivity. 

Conduction Current.— The current that 
passes through a metallic or other con- 
ducting substance, as distinguished from 
one produced in a non-conductor or 
dielectric. 

Conduction, Electric— (1) The so-called 
flow or passage of electricity through a 
metallic or other similar substance. 
(2) The ability of a substance to determine 
the direction in which electric energy 
shall be transmitted through the ether 
surrounding it. (3) The ability of a sub- 
stance to determine the direction in which 
a current of electricity shall pass from 
one point to another. 

Conduction Lightning-Protection. — 
The protection of any instrument from 
the passage of a current due to lightning 
through its coils. 

Conduction Lightning-Protector. — A 
lightning protector by means of which a 
current is prevented from passing through 
the coils of a galvanometer, or other 
needle instrument, and thus injuriously 
disturb the magnetism of the needle. 

Conduction Resistance.— The resistance 
offered by a conductor to an electric 
current. 

Conductive. — Possessing the power of 
conducting. 

Conductive Discharge. — A discharge 
effected by leading the charge off through 
a conductor placed in contact with the 
charged body, as opposed to a convective 
or disruptive discharge. 

Conductivity, Electric— (1) The recip- 
rocal of electric resistivity. (2) The con- 
ductance of a substance referred to unit 
dimensions. 

Conductivity Resistance. — The resist- 
ance offered by a substance to electric 
conduction, or to the passage of elec- 
tricity through its mass. 

Conductor. — (1) Any substance which 
will permit the so-called passage of an 
electric current. (2) A substance which 
possesses the ability of determining the 
direction in which electric energy shall 
pass through the ether in the dielectric 
surrounding it. 

Conductor Resistance.— A term fre- 
quently employed for copper resistance. 

Conductor System. — A net-work of in- 
terconnected conductors employed for 
distributing electricity. 

Conduit Cables.— A cable conductor or 
set of conductors laid in a conduit. 



€on.] 



723 



[Con, 



Conduit Conductors.— Conductors in- 
tended for use in underground circuits, 
provided with an insulation suitable to 
maintain the electric integrity of the 
separate circuits. 

Conduit, Electric. — An underground 

space, either single or provided with a 

number of separate spaces called ducts, 

• employed for the reception of electric 

wires or cables. 

Conduit Trolley-System.— A single or 
double-trolley system in which the trolley 
wire or wires are placed in an under- 
ground slotted conduit, the trolley wheel 
being replaced by a plow or sled pushed 
or drawn through the slot. 

Coned Plunger for Electromagnetic 
S o 1 e n o i d. — A cone-shaped core, em- 
ployed in connection with a solenoid in- 
stead of the ordinary cylindrical core, for 
the purpose of obtaining a comparatively 
uniform pull through a fairly extended 
movement of the core. 

Conflict, Electric. — A term proposed for 
the magnetic field surrounding an active 
conductor. 

Congelation. — The act of freezing, or the 
change of a liquid into a solid on loss of 
heat. 

Conical Conductor.— (1) A cone-shaped 
conductor, which gradually increases or 
decreases in diameter, thus assuming the 
form of a tapering cone, employed to 
obtain an approximately constant current 
density through a system of parallel dis- 
tribution. (2) In practice, a cylindrical 
conductor that tapers by sections, the 
diameter being reduced in each succeed- 
ing length. 

Conjoined E. M. F.'s. — A number of elec- 
tromotive forces simultaneously acting 
in one circuit. 

Conjugate Coils. — Two coils whose con- 
ductors are conjugate to each other. 

Conjugate Conductors.— (1) In a con- 
ducting net-work, two conductors so re- 
lated that the introduction of an E. M. F. 
in one produces no current in the other. 
(2) Two conductors so placed as regards 
each other that an interruption of the 
current in one, produces no induced cur- 
rent in the other. 

Conjugate Functions. — The real and im- 
aginary components of a function of a 
complex variable. 

Connect. — To place or bring into electric 
contact. 

Connecting. — Placing or bringing into 
electric contact. 



Connecting Bars.— Metallic bars at a 
call-wire multiple-switchboard, for con- 
necting the operator's set with the call- 
wire jacks through a cord. 

Connecting In "Bridge."— A phrase 
sometimes employed for connecting in 
multiple arc or parallel. 

Connecting Jack.— A jack for introduc- 
ing a loop into a telephone circuit. 

Connecting Peg.— A metallic block for 
bridging an air gap and so making an 
electric connection. 

Connecting Screws. — A term sometimes 
employed indifferently for connectors or 
for binding posts. 

Connecting Side of Telephone Switch- 
board. — That side of a telephone switch- 
board at which connections are made 
with subscribers wanted, as distinguished 
from the side at which calls are received. 

Connecting Sleeve. — A metallic sleeve 
employed as a connector for readily join- 
ing the ends of two or more wires. 

Connecting-Up.— (1) In telegraphy, join- 
ing up. (2) The operation of establishing 
an electric circuit. 

Connection.— The act of placing in electric 
or magnetic contact. 

Connection Board of Transformer.— A 
board usually located in an accessible 
place in a transformer case, and provided 
with binding posts for conveniently mak- 
ing or changing the connections of the 
transformer coils with the external cir- 
cuits. 

Connection for Intensity.— A phrase 
formerly employed for connection in 
series. (Nearly obsolete.) 

Connection for Quantity.— A phrase 
formerly employed for connection in mul- 
tiple. (Nearly obsolete.) 

Connection in Cascade.— A term some- 
times empkwed for connection in series. 

Connection in Sequence. — A term some- 
times used for connection in series. 

Connection of Battery for Intensity. 
A term formerly employed for the series- 
connection of the cells in a battery. (Ob- 
solete.) 

Connection of Battery for Quantity.— 
A term formerly employed for a multiple 
or parallel connection of the cells in a bat- 
tery. (Obsolete.) 

Connector. — A device for readily connect- 
ing or joining the ends of two or more 
conductors. 

Conning Tower. — A shell-proof tower 
from which the commander on a turreted 



Con.] 



724 



[Con. 



war-sliip directs its movements when in 
action. 

Consequent Points.— The points or places 
in an anomalous magnet where its conse- 
quent poles are situated. 

Consequent Pole.— (1) A magnet pole 
formed by two free north or two free 
south poles placed together. (2) A mag- 
net pole developed at some point of a 
magnet other than its extremities. 

Consequent Poles of Dynamo. — 

(1) Dynamo poles formed by the juxtapo- 
sition of two similar magnetic poles. 

(2) Dynamo poles developed at polar pro- 
jections unprovided with magnetizing 
coils. 

Consequent Resistance. — A term pro- 
posed for the apparent resistance of a 
conductor traversed by alternating cur- 
rents, as modified by the skin effect, and 
as distinguished from its ohmic resist- 
ance or its inductive resistance. 

Conservation of Energy.— (1) A term 
indicative of the fact that energy can 
never be annihilated, so that if it disap- 
pears in one form, it must reappear in 
some other form. (2) The indestructi- 
bility of energy. 

Consonance. — (1) A phase agreement be- 
tween two simple-periodic waves or vibra- 
tions. (2) The reinforcement of sound 
waves, or their increase in intensity, by 
means of vibrating bodies that are not in 
resonance with, or are tuned to vibrate 
in unison with, the sounding body. 

(3) Forced unison. 

Consonance, Electric. — In an alternat- 
ing-current circuit the co-phasing of the 
impressed E. M. F. with the primary cur- 
rent, due to the influence of capacity in 
an inductively associated secondary cir- 
cuit. 

Consonant Electric Circuit.— (1) An 
alternating-current circuit containing re- 
sistance and inductance, and inductively 
associated with a secondary circuit con- 
taining resistance, inductance, and capac- 
ity, in such a manner that the secondary 
inductance and capacity neutralize the 
inductance of the primary circuit. (2) A 
primary alternating-current circuit devoid 
of reactance or choking effect, owing to 
the presence of a condenser in a secondary 
circuit, as distinguished from the effect 
of a condenser inserted in the primary 
circuit directly. 

Consonator. — Any body capable of rein- 
forcing sound by consonance. 

Constant. — Possessing an invariable value. 



Constant Cell. — Any voltaic cell which, 
under certain circumstances, is capable of 
furnishing a constant electromotive force 
and current. 

Constant Current.— (1) A direct current, 
or one that always flows in the same di- 
rection. (2) A current whose strength is 
unvarying. 

Constant - Current Alternating - Cur- 
rent Dynamo. — An alternator which 
supplies a constant effective current 
strength in its circuit. 

Constant-Current Arc-Lamp.— A series- 
connected arc-lamp. 

Constant-Current Circuit.— A circuit 
whose current strength is maintained 
constant notwithstanding changes in its 
resistance. 

Constant-Current Dynamo.— A con- 
stant-current generator. 

Constant-Current Generator.— A term 
applied to a generator intended to pro- 
duce a constant strength of current de- 
spite changes in its load. 

Constant-CurrentTransformation.— A 
change or transformation in the strength 
of a constant current. 

Constant-Current Transformer.— (1) A 
transformer which is intended to raise or 
reduce a current strength in a given con- 
stant ratio. (2) A transformer designed 
to maintain a constant strength of current 
in its secondary circuit, despite changes 
of load. 

Constant Inductance.— (1) The induc- 
tance of a circuit immersed in or wholly 
surrounded by a material of constant 
magnetic permeability. (2) An induc- 
tance which does not vary with the cur- 
rent strength. 

Constant-Potential Alternating-Cur- 
rent Dynamo.— (1) An alternator which 
supplies a constant effective pressure at 
its terminals. (2) A compounded alter- 
nator. 

Constant-Potential Arc-Lamp.— An 
arc lamp employed on constant-potential 
or incandescent mains. 

Constant-Potential Circuit. — (1) A cir- 
cuit whose potential is maintained ap- 
proximately constant. (2) A multiple-arc 
or parallel-connected circuit. 

Constant-Potential Dynamo.— (1) A 

dynamo that furnishes an approximately 
constant difference of potential or elec- 
tromotive force despite changes in its re- 
sistance or load. (2) A shunt or com- 
pound-wound dynamo. 
Constant-Potential Generator.— A con- 
stant-potential dynamo. 



Con.] 



725 



[Con. 



Constant-Potential Motor.— (1) A motor 
designed for operation by means of a con- 
stant-potential current. (2) Generally, a 
shunt-wound or compound-wound motor. 

Consumer. — One who receives electric 
supply. 

Consumer's Terminals. — In a system of 
electric distribution the terminals of a 
house service, the property of the house, 
and at which the electric supply is de- 
livered by the supply company. 

Consumption Circuit.— Any circuit in 
which an electro-receptive device is 
placed. 

Contact Breaker.— A device for breaking 
or opening an electric circuit. 

Contact Electromotive Force.— Elec- 
tromotive force produced by the mere 
contact of dissimilar metals. 

Contact Electricity.— Electricity pro- 
duced by contact electromotive forces. 

Contact Force. — A contact electromotive 
force. 

Contact Lamp. — A name sometimes given 
to a semi-incandescent lamp. 

Contact Resistance. — Resistance pro- 
duced at the contact of two or more sur- 
faces. 

Contact Ring of Telephone Plug.— A 
plug in a multiple telephone switchboard 
carrying an insulated metal ring or sleeve 
establishing a circuit for the busy test. 

Contact Rings of Alternator.— The col- 
lector rings of an alternator. 

Contact Series. — A series of metals ar- 
ranged in such an order that each becomes 
positively electrified by contact with the 
one that follows it. 

Contact Screw. — A screw the end of 
which is provided with a platinum or 
other contact, employed to close the 
circuit of any electric device in whose 
circuit it is placed. 

Contact Theory of Electricity .—A the- 
ory that ascribes the production of elec- 
tromotive forces, or of electricity, to the 
contact of dissimilar substances or sur- 
faces. 

Contact Theory of Voltaic Cell.— The 
contact theory of electricity applied to 
the production of electricity in a voltaic 
cell. 

Contacts. — (1) Conducting pieces or plates 
introduced into electric circuits at points 
wiiere it is desired to open and close the 
circuit. (2) A variety of fault occasioned 
in any circuit by the accidental contact 
of any part of the circuit with a conduct- 
ing body. (3) A metallic cross or faulty 



connection between two telegraphic or 
telephonic circuits. 

Containing Cell.— (1) A jar provided for 
holding or containing the solution or 
electrolyte employed in connection with 
a primary or secondary voltaic couple. 
(2) A jar or receptacle for containing any 
liquid or solution, as in an electro-plating 
bath. 

Continental Telegraphic-Code.— A tele- 
graphic-code employed in Europe gener- 
ally. 

Continuator. — A constant-current dyna- 
mo. (Not in use.) 

Continuity of Circuit. — The uninter- 
rupted conducting condition of a circuit. 

Continuity-Preserving Transmitter.— 
A transmitter employed in duplex teleg- 
raphy, so arranged that the line wire 
may be transferred from the battery to 
the earth without any break in the conti- 
nuity of the circuit. 

Continuous- Alternating Transformer. 

(1) A secondary generator for transform- 
ing continuous into alternating currents. 

(2) A dynamotor, motor-dynamo, or ro- 
tary transformer. 

Continuous Current.— (1) An electric 
current which flows in one and the same 
direction. (2) A direct current. 

Continuous-Current Arc. — A voltaic arc 
produced by a continuous current, as dis- 
tinguished from one produced by alternat- 
ing currents. 

Continuous-Current Armature-Wind- 
ings. — Armature windings suitable for 
use in continuous-current generators. 

Continuous-Current Dynamo-Electric 
Machine. — A continuous-current gener- 
ator. 

Continuous-Current Generator.— Any 
generator capable of furnishing contin- 
uous currents. 

Continuous-Current Motor.— A motor 
operated by continuous or direct currents. 

Continuous-Current Transformer.— (1) 
A dynamotor or motor-dynamo. (2) A 
transformer from one continuous pressure 
and current to another. 

Continuous E. M. F.'s.— Electromotive 
forces whose direction and value remain 
constant. 

Continuous - Sounding or Ringing 
Electric-Bell. — (l)An electric bell, which 
on completion of its circuit continues 
sounding until stopped. (2) A trembling 
bell. 

Continuous Spectrum.— (1) A luminous 
spectrum that is devoid of the Fraunhofer 



Con.] 



726 



[Con. 



dark lines, or which contains all the phys- 
iologically effective luminous frequencies. 
(2) The spectrum of a sufficiently heated 
incandescent solid. 

Continuous- Surface Commutator.— A 
dynamo commutator, whose surface con- 
tains no breaks in the gaps between con- 
tiguous commutator bars; i.e., whose 
gaps are filled with an insulating material 
instead of being left with air spaces. 

Continuous Trolley Wire. — An un- 
jointed trolley wire. 

Continuous Winding. — A term fre- 
quently employed for wave winding or 
undulatory winding of an armature. 

Continuous Wire or Conductor. — An 
unjointed wire or conductor. 

Continuously Insulated Cable. —A 

length of cable extending continuously 
between two points without any taps. 

Contracting Magnetic Whirls.— Mag- 
netic whirls which are decreasing or mov- 
ing in towards the electro-magnet or cir- 
cuit producing them. 

Contractures. — In electro-therapeutics 
prolonged muscular spasms or tetanus 
caused by the passage of electric currents. 

Contraplex Telegraph. — A general term 
embracing the apparatus employed in 
contraplex telegraphy. 

Contraplex Telegraphy.— Duplex teleg- 
raphy in which transmissions are simul- 
taneously made from opposite ends of the 
line. 

Controlled Clock. — A clock whose works 
are controlled or regulated either entirely 
or partially, by an electric current. 

Controller. — (1) The magnet employed in 
a system of automatic constant-current 
regulation, whose coils are traversed by 
the main current, employed automatically 
to throw a regulator magnet into or out 
of the main circuit on changes of the cur- 
rent passing. (2) Any electric mechanism 
for controlling a circuit or system. (3) An 
electric switching mechanism for control- 
ling the speed of a motor or motors. (4) A 
street-railway car-controller. 

Controller Resistance. — Resistance em- 
ployed in connection with street-car con- 
trollers for starting or stopping the mo- 
tors, or for varying their speed. 

Controller Switch.— (1) The switch oper- 
ating the switch cylinder of a street-car 
controller. (2) Any switch employed in 
connection with a street-car controller. 

Controlling Box. — The box holding any 
controlling rheostat or controller. 

Controlling Block, Electric— In a sys- 
tem of time-telegraphy, the master clock 



whose impulses move or regulate the 
secondary clocks. 

Controlling Magnet.— (1) Any magnet 
which controls some particular action, 
as, for example, the attraction of a needle 
in a galvanometer. (2) A name some-j 
times given to the controller in an auto- 
matic system of current regulation. 

Controlling Stand. — The support or stand 
provided for holding the apparatus em- 
ployed for controlling a motor. 

Convection Currents. — Currents pro- 
duced by the bodily carrying forward of 
static charges in convection streams. 

Convection, Electric— The air streams 
which are thrown off from points on the 
surface of a charged insulated conductor. 

Convection of Heat, Electric— (1) A 
term employed to express the dissymmet- 
rical distribution of temperature that 
occurs when an electric current is sent 
through a metallic wire, the middle of 
which is maintained at one constant tem- 
perature, and the ends at another constant 
temperature. (2) Distribution of heat 
which attends the passage of an electric 
current through an unequally heated con- 
ductor. 

Convection Streams.— Streams of elec- 
trified air, or other gaseous or vaporous 
particles, given off from sharp points on 
the surface of highly charged insulated 
conductors. 

Convection Transference. — The trans- 
ference of electricity by means of convec- 
tion streams. 

Convective Discharge.— The discharge 
which occurs from the points of a highly 
charged conductor, through the electro- 
static repulsion of similarly charged air 
particles, which thus carry off minute 
charges. 

Converging Magnetic Flux. — Magnetic 
flux that converges or radiates from a 
point or points. 

Conversion of Electromotive Force- 
Any increase or decrease in the value of 
an electromotive force produced by means 
of a transformer. 

Convert. — To transform or change an elec- t 
tromotive force or current. 

Converted Currents. — Electric currents 
whose strengths have been increased or 
decreased by means of a transformer. 

Converter. — A name sometimes given 
to a transformer. 

Converter Bracket. — (1) A bracket for 
holding a pair of insulators and a single 
light converter and shunt box in an alter- 
nating-current series-system of street light- 



Con.] 



727 



[Cop. 



ing. (2) A bracket for supporting an al- 
ternating-current converter. 

Converter Fuse.— A safety fuse connect- 
ed with the circuit or circuits of a 
converter or transformer, and usually 
mounted in the transformer case. 

Converting. — Transforming or changing 
an electromotive force or current. 

Converting Currents.— (1) Changing the 
value of the current strength by means 
of transformers. (2) Changing a contin- 
uous into an alternating current, or vice 
versa. 

Converting Station. — (1) A transform- 
ing station. (2) A station containing 
transformers. 

Conveyer, Electric. — An electrically op- 
erated or controlled system of transport- 
ing material. 

Convolutions of Wire. — The separate 
loops or turns in a helix or coil. 

Cooling-Box of Hydro-Electric Ma- 
chine. — A box provided in Armstrong's 
hydro-electric machine for the steam to 
pass through before leaving the nozzle. 

Cooling Surface. — The surface from 
which a hot body can dissipate its heat 
energy. 

Cooling Surface of Armature. — That 
portion of an armature surface from 
which it can dissipate into the surround- 
ing air, the heat energy produced in it 
by the passage of the currents generated 
during its rotation. 

Cooling Tubes. — Tubes inserted in the 
frame or casing of an alternating-current 
transformer for the supply of cold water 
from an external pump' or source. 

Co-Periodic. — Possessing the same peri- 
odicity. 

Co-Periodic E. M. F.'s, Currents or 
Fluxes. — Electromotive forces, currents 
or fluxes, possessing the same periodicity. 

Co-Phasal. — Possessing the same phase. 

Co-Phasal Alternations. — Alternations 
possessing the same phase. 

Co-Phase. — (1) Coincidence in phase of 
co-periodic motions. (2) Such a phase 
relation between two periodic but non- 
co-periodic quantities as tends to increase 
the amplitude of the motion. 

Copper Arc. — An arc formed between 
copper electrodes. 

Copper Bath. — An electrolytic bath 
containing an electrolyzable solution of a 
copper salt, and a copper plate forming 
the anode, and placed in an electrolyte 
near the object to be electroplated, which 
forms the cathode. 



Copper Battery.— A battery employed in 
sending copper currents to line. 

Copper Conductivity Standard.— (1) 
According to rules of the British Institu- 
tion of Electrical Engineers, a metre- 
gramme wire of standard conductivity, 
whose resistance is 0.1519 international 
ohm at 15°C, corresponding to Matthies- 
sen's standard for hard copper. (2) Ac- 
cording to a committee of the American 
Institute of Electrical Engineers, a copper 
metre-gramme, of Matthiessen standard 
soft copper conductivity, whose resistance 
is 0.1501 ohm at 15°C. 

Copper Connector. — (1) A particular 
form of connector employed in the grav- 
ity voltaic cell for connecting the copper 
element to the circuit wire or conductor. 
(2) A special form of coupler for con- 
necting large wires or conductors. 

Copper Current.— A term sometimes 
used in telegraphy for a positive current. 

Copper Efficiency. — The ratio of the 
electric energy delivered by a copper con- 
ducting system, to the energy delivered 
to that system. 

Copper Fuse- Wire Terminals.— Copper 
terminals provided for connection with 
the terminals of fuse wires or safety 
catches. 

Copper Heat. — The heat which appears 
in a copper conductor due to the passage 
through it of an electric current. 

Copper-Lead Accumulator. — An ac- 
cumulator or storage battery consisting 
of plates of copper and lead immersed in 
a solution of copper sulphate. 

Copper Loss.— The total loss of energy 
produced by the passage of a current 
through the copper wire of a dynamo, 
motor, or conducting system generally. 

Copper Magnetic Circuit.— That portion 
of a magnetic circuit which is completed 
through copper. 

Copper Plating.— Electro - plating with 
copper. 

Copper Resistance. — In submarine tel 
egraphy, conductor resistance. 

Copper Resistivity.— The specific re- 
sistance of copper of Matthiessen soft cop- 
per standard referred to the resistance of 
a cube one centimetre in length of edge, 
such a cube offering between parallel 
faces a resistance of 1.594 microhms at 
0° C. (2) The resistivity of a copper wire. 

Copper Ribbon.— A variety of strap cop- 
per. 

Copper Shell of Electro - Type.— The 

thin electrolytic deposit of copper which, 
when stiffened by the backing metal and 



€op.] 



728 



[Cos. 



suitably mounted on a block, forms the 
electro-type. 

Copper Strap. — Copper conductors in the 
form of straps or flat bars. 

Copper Tape. —Rectangular straps or bars 
of copper employed for armature wind- 
ings. 

Copper Voltameter. — A voltameter 
whose indications are dependent on the 
electrolysis of a solution of a copper salt. 

Copper-Zinc Accumulator.— An accu- 
mulator or storage cell consisting of a 
plate of copper and a plate of zinc im- 
mersed in a solution of zinc sulphate. 

Coppered Arc-Light Carbons.— Carbons 
employed in arc-lamps, covered electro- 
lytically with copper. 

Coppered Carbons.— Carbons for arc- 
lamps, or batteries, that are electrolyti- 
cally coated with copper. 

Coppered Plumbago.— Powdered plum- 
bago coated with copper for use in the 
metallization of objects to be electro- 
plated. 

Copying Telegraph.— A fac-simile or 
automatic telegraph. 

Cord Adjuster. — A device for adjusting 
the length of a pendant cord. 

Cord, Electric. — A flexible, insulated elec- 
tric conductor, generally containing two 
parallel wires. 

Cord Peg.— A cord to which a connecting 
peg is attached. 

Cord-Peg Connection.— Connection in a 
switchboard by means of a cord peg. 

Cord Pendant.— A flexible or stranded 
conductor employed for a lamp pendant. 

Cord Shelf.— A shelf provided for the 
holding of the cord pegs of a telephone 
switchboard. 

Core Discs. — Stampings or cuttings of 
sheet iron, employed, when suitably as- 
sembled, for the laminated core of a 
dynamo or motor armature, or other 
dynamo-electric apparatus. 

Core Losses. — The hysteresis and the 
Foucault or eddy-current losses of the 
core of a dynamo, motor, or transformer. 

Core Losses of Transformer. — (1) The 

hysteresis and Foucault-curfent losses in 
the core of a transformer. (2) The iron 
losses in a transformer. 

Core of Cable. — (1) The insulated wires em- 
ployed for the transmission of the current 
through a conducting cable. (2) The elec- 
tric conductor and insulator as distin- 
guished from the mechanical serving and 
sheathing of a cable. 



Core Pins of Magnet.— Pins in the cores 
of a magnet for securing their firm 
mechanical union with the yoke. 

Core Ratio of Cable. — The ratio between 
the diameter of the core of a cable and the 
mean diameter of the conductor strand. 

Core Transformer.— (1) A transformer in 
which the iron forms the core or central 
portion on which the wire windings are 
placed. (2) A transformer possessing a 
core capable of insertion or removal. 

Cored Carbons. — Arc-light carbons pro- 
vided with a soft centre of carbon. 

Cored Electrodes.— Cored arc-light car- 
bons. 

Coreless.— Devoid of a core. 

Coreless Armature of Dynamo or 
Motor. — An armature of a dynamo or 
motor unprovided with the usual core 
of iron. 

Corn-Plaster Euse.— A strip of fusible 
metal rolled up with an asbestos tape in 
the form of a cylinder and employed as 
a safety catch in a telephone switchboard. 

Cornice Bracket. — A form of insulator 
bracket for use on the under side of cor- 
nices. 

Corposant. — A name sometimes given by 
sailors to the St. Elmo's fire. 

Coronse. — (1) Crown - shaped masses of 
light sometimes seen during the preva- 
lence of aurorse. (2) Auroral coronse. 

Corpuscle. — (1) An ultimate particle in an 
assumed highly tenuous substance that 
was formerly believed to be emitted by 
highly heated bodies. (2) Any of the 
ultimate particles of the matter into 
which it has been assumed that the ulti- 
mate elementary atoms may be divided. 

Correcting Eactor of Wattmeter. — 
The correction which must be applied to 
the readings of an alternating-current 
wattmeter when the reactance in its 
shunt circuit cannot be neglected. 

Correcting Relay.— <1) A relay employed 
in the Delaney system of synchronous- 
multiplex telegraphy to aid in obtaining 
synchronism. (2) In a quadruplex sys- 
tem, a relay intermediate between the 
polarized receiving relay and its sounder, 
for the purpose of preventing false signals 
or kicks. 

Correlation of Energy. — A term some- 
times applied to the different phases under 
which energy may appear. 

Corrugated Reflector. — A reflector 
formed of silvered corrugated glass. 

Cosine. — (1) One of the trigonometrical 
functions. (2) The ratio of the base to 



Cos.] 



729 



[Cou, 



the hypothenuse of a right-angled triangle 
in which the hypothenuse is the radius 
vector, and the angle between the base 
and hypothenuse the angle whose cosine 
is considered. 

Cosine Law of Illumination. — The in- 
tensity of illumination, of a surface 
illumined by a single-point source, varies 
as the cosine of the angle of the rays 
incident upon the surface from that 
source. 

Cosinusoid. — A curve of cosines. 

Cotangent. — (1) One of the trigonometrical 
functions. (2) The reciprocal of the tan- 
gent of an angle. 

Coulomb. — (1) The practical unit of elec- 
tric quantity. (2) Such a quantity of 
electricity as would pass in one second 
through a circuit conveying one ampere. 
(3) The quantity of electricity contained 
in a condenser of one farad capacity, 
when subjected to the E. M. F. of one 
volt. 

Coulomb Meter. — A meter for measuring 
in coulombs, the quantity of electricity 
which passes through any circuit. 

Coulomb's Electric Balance.— A tor- 
sion balance for measuring the forces of 
electric oi magnetic repulsion. 

Coulomb's Torsion Balance. — An ap- 
paratus for measuring the force of elec- 
tric or magnetic repulsion between two 
similarly charged bodies, or between two 
similar magnet poles, by opposing to such 
forces the torsion of a thin wire. 

Coulomb- Volt. — A word sometimes em- 
ployed for the volt-coulomb or joule. 

Counter-Clockwise Motion.— A rotary 
motion whose direction is opposed to that 
of the hands of a clock, as viewed from 
the clock face. 

Counter Communication Telephone 
Switch. — A switch arranged in a tele- 
phone system in connection with a silence 
cabinet, whereby a person occupying the 
cabinet is unable to call up the exchange 
without the sanction and assistance of an 
attendant in the office outside the cabinet. 

Counter, Electric— (1) A device for 
counting and registering such quantities 
as the number of fares collected, gallons of 
water pumped, sheets of paper printed, 
votes polled, revolutions of an engine per 
second, etc. (2) Any counting device 
operated or controlled by electricity. 

Counter Electro-Dynamic Force.— The 
electro-magnetic force which is set up in 
a dynamo armature opposing the im- 
pressed driving force. 



Counter-Electromotive Force.— (1) An 

opposed or reverse electromotive force 
which tends to set up a current in the 
opposite direction to that actually pro- 
duced by a source. (2) In an electric 
motor, an electromotive force produced 
by the rotation of the armature and op- 
posed to that produced by the driving 
current. 

Counter-Electromotive Force Cell. — 

(1) An electrolytic cell inserted in the 
charging circuit of a storage battery to re- 
duce the charging current strength, usu- 
ally composed of opposed plates or grids of 
antimonious lead from the surfaces of 
which gases are disengaged by electrol- 
ysis. (2) Additional cells, generally with- 
out active material, employed with a stor- 
age battery which has to be charged at a 
pressure above the normal pressure, and 
inserted between the dynamo and the 
mains to maintain their pressure normal. 
Counter-Electromotive Force Light- 
ning-Arrester. — (1) A lightning-arrester 
in which the passage of a discharge 
through the instruments to be protected 
is opposed by a counter electromotive 
force generated by induction on the pas- 
sage of the lightning discharge. (2.) A 
choking-coil lightning-arrester. 

Counter-Electromotive Force of Arc. — 

An electromotive force produced during 
the formation of a carbon voltaic arc op- 
posed to that which maintains the arc. 

Counter-Electromotive Force of Con- 
vective Discharge. — Resistance to the 
passage of an electric discharge through 
a high vacuum, somewhat of the nature 
of a counter electromotive force. 

Counter-Electromotive Force of Elec- 
trolysis. — A counter electromotive force 
produced by electrolysis in the plating 
bath of an electrolytic cell. 

Counter-Electromotive Force of In- 
duction. — The counter electromotive 
force of self or mutual induction. 

Counter-Electromotive Force of Mut- 
ual Induction. — (1) Counter-electro- 
motive force produced by mutual induc- 
tion between neighboring circuits. (2) 
Counter-electromotive force in the pri- 
mary circuit of a transformer produced by 
the mutual induction from the current 
in the secondary circuit. 

Counter-Electromotive Force of Polar- 
ization. — Electromotive force developed 
in a voltaic cell or plating bath by polar- 
ization, and opposed to that which pro- 
duces the current of the cell. 

Counter-Electromotive Force of Self- 
induction. — The counter-electromotive 



Con.] 



730 



[Cri, 



force produced in the primary circuit of an 
induction coil by the action thereon of an 
alternating electromotive force. 
Counter-Electromotive Force of Self- 
induction of the Primary. — The 
counter-electromotive force produced in 
the primary circuit of a transformer by 
the action of induction of the primary 
current on itself, as distinguished from 
that produced by mutual induction from 
the secondary current. 

Counter-Electromotive Force of Self- 
induction of the Secondary. — The 
counter-electromotive force produced in 
the secondary by periodic variations in 
the effective electromotive force in the 
secondary circuit. 

Counter-Electromotive Force of Stor- 
age Battery. — The electromotive force 
in a storage battery which opposes the 
electromotive force employed in charging. 

Counter-Electromotive Force of Volt-' 
aic Cell. — The counter-electromotive 
force in a voltaic cell due to its polariza- 
tion. 

Counter Inductive Effect.— An opposal 
of current or charge b}^ means of an elec- 
tromotive force produced by induction. 

Counter Pressure.— A term sometimes 
used for counter-electromotive force. 

Couple. — (1) In mechanics, two equal and 
parallel, but oppositely directed forces, 
not acting in the same line, and tending to 
produce rotation. (2) The two elements 
in a voltaic cell or thermo-electric cell. 

Coupled Cells. — A number of separate 
cells so connected or coupled as to form 
a battery or single electric source. 

Coupling Box for Electric Tubes.— A 
box provided for the ready connection of 
the conductors in the separate lengths 
of underground electric tubes. 

Coupling Clamp for Underground Con- 
ductors. — An electric coupling between 
two lengths of underground conductors. 

Coupling Joint for Underground 
Tubing. — A joint for the separate con- 
ductors in an underground tubing, con- 
sisting generally of a flexible conductor 
and connectors for ready attachment to 
the ends of the conductor. 

Coupling of Voltaic Cells or Other 
Electric Sources. — Connecting a num- 
ber of separate voltaic cells, or other sep- 
arate electric sources, so as to enable them 
to act as a battery or single electric 
source. 

Coupling Transformer. — A transformer 
which employs polyphasal coupling of 
magnetic circuits. 



Cradle Dynamometer. — A dynamometer 
in which the dynamo to be tested is sup- 
ported in a cradle, and the mechanical 
energy it receives or transmits is measured' 
by the torque developed by the cradle 
about its axis. 

Cradle Suspension of Street-Car Mo- 
tor. — A method of supporting a street- 
car motor on its truck upon a spring 
cradle. 

Crater in Positive Carbon.— A depression 
in the end of the positive carbon of an 
arc-lamp, which occurs after the arc has 
been maintained for some little time. 

"Creep" of Belt.— A term sometimes 
used for the slip of a belt. 

Creepage. — The residual elastic torsion of 
a suspension fibre. 

Creeping, Electric— A term sometimes 
applied to the creeping of a current. 

Creeping in Voltaic Cell.— The formation 
by efflorescence of salts on the sides of 
the porous cup of the voltaic cell, on the 
binding posts, or on the walls of the 
vessel containing the electrolyte. 

Creeping of Belt.— (1) An action of a driv- 
ing belt due to its retractility, whereby the 
driving pulley travels somewhat faster 
than the driven pulley. (2) Belt slip. 

Creeping of Current.— (1) A term some- 
times employed for a change in the direc- 
tion of the path of a current from a direct 
line between the points of connection with 
the source. (2) Electrification or polariza- 
tion currents in an electrolyte. (3) The 
extension of a glow or streamer discharge 
over the surface of a dielectric. 

Creosoting. — A process employed for the 
preservation of wood, such, for example, 
as telegraph poles, by injecting creosote 
into the pores of the wood. 

Crevasse. — A narrow gap or slit effected, 
or imagined, in a magnet or magnetized 
substance, for the purpose of determining 
the magnetic forces on a small needle. 

Crith. — A proposed unit of mass, or the 
weight of one litre or cubic decimetre of 
hydrogen at 0° Centigrade, and 760 mil- 
limetres barometric pressure. 

Critical Angle.— The angle of incidence at 
which a ray of light falling upon the 
surface of a body ceases to be reflected 
and is wholly absorbed or internally re- 
flected and refracted. 

Critical Current.— The current strength 
at which a certain critical result is 
reached. 

Critical-Current of Dynamo.— That 
value of the current of a dynamo at which 



Cri.] 



731 



[Cro. 



its characteristic curve begins to depart 
from a nearly straight line. 
Critical-Current of Magnetization.— 
The current strength at which a small 
increase in the magnetizing current pro- 
duces a great increase in the magnetiza- 
tion of an iron core. 

Critical-Distance of Lateral Discharge 
through an Alternative Path. — The 
distance at which a discharge will take 
place through an air space of given di- 
mensions, in preference to passing through 
a metallic circuit of comparatively small 

ohmic resistance. 

\ 

Critical Pressure of a Gas or Vapor. — 

(1) The lowest pressure at which a sub- 
stance in the liquid state cannot be par- 
tially vaporized by increase of temper- 
ature, but changes wholly into a gas. (2) 
The lowest pressure at which a gaseous 
substance when cooled is condensed to a 
liquid in the presence of its vapor. (3) 
The pressure above which no amount of 
chilling will liquefy a gaseous substance. 

Critical-Speed of Compound-Wound 
Dynamo. — The speed at which both the 
series and shunt coils of a dynamo give 
the same difference of potential when the 
full load is on the machine, as the shunt 
coil would have if used alone on open- 
circuit. (2) The speed at which a 
dynamo commences to build up its ex- 
citation. 

Critical Temperature of a Gas or 
Vapor. — (1) The temperature of a vapor 
at a given pressure above which no pres- 
sure, however great, can convert the 
vapor into liquid. (2) The temperature 
above which a vapor is essentially a per- 
manent gas. 

Critical Temperature of a Substance. — 

(1) The temperature above which no 
pressure applied to the substance in the 
gaseous form will effect liquefaction. 

(2) The temperature below which a gase- 
ous substance is a vapor, and as such cap- 
able of liquefaction by pressure. 

Critical Volume of a Gas or Vapor.— 
The volume of a substance at the critical 
temperature and pressure. 

Crookes' Dark-Space. — A dark space 
surrounding the negative electrode in a 
rarified space through which electric dis- 
charges are passing. 

Crookes' Effect.— The effect produced in 
high-vacuum tubes due to the charac- 
teristic motions possessed by heated or 
electrified molecules when in the ultra- 
gaseous or radiant state. 

Crookes' Electric Radiometer. — A ra- 
diometer in which the repulsions of the 



molecules of the residual atmosphere take 
place from electrified instead of from 
heated surfaces. 

Crookes' Layer.— The dark space or layer 
enveloping the cathode of an excited 
Crookes 1 tube. 

Crookes' Radiometer. — An apparatus 
for demonstrating the action of radiant 
matter in producing motion, from the 
effects of the reaction of a stream of 
molecules thrown off from a number of 
easily moved, unequally heated surfaces. 

Crookes' Tubes. — (1) Glass tubes contain- 
ing high vacua, provided with platinum 
leading-in wires terminating in suitably 
shaped metallic surfaces, employed in 
demonstrating the peculiarities of the 
radiant or ultragaseous condition of mat- 
ter. (2) A name frequently given to 
X-ray tubes. 

Cross. — (1) A connection or contact between 
two telegraph circuits. (2) A contact be- 
tween two conductors or circuits which 
should be insulated from each other. 

Cross- Ampere Turns. — (1) Ampere turns 
on a dynamo armature possessing a cross- 
magnetizing tendency to distort the mag- 
netic field. (2) Ampere turns which tend 
to produce a cross magnetization, at right- 
angles to that produced by the field- 
magnets. 

Cross Arm. — (1) A horizontal beam at- 
tached to a pole for the support of the 
insulators of telegraph, electric light, or 
other electric wires. (2) A telegraphic 
arm. 

Cross-Arm Bolts. — Bolts employed for 
attaching the cross-arms to a pole. 

Cross-Arm Brace. — Galvanized iron 
braces whose ends are respectively con- 
nected to the pole and the cross-arm for 
the purpose of stiffening them. 

Cross Bonding. — In an electric railway 
the bonding between the ground feeder 
and the track for the purpose of ensuring 
a good conducting return circuit. 

Cross-Connected Dynamo.— A dynamo 
the ends of whose armature coils are con- 
nected to corresponding segments all 
around the commutator. 

Cross-Connecting Board. — In a system 
of telegraphic or telephonic communica- 
tion, a board to which the line terminals 
are run, before entering the switchboard, 
so as readily to place any line in connec- 
tion with any desired section of the switch- 
board. 

Cross-Connecting Conductors. — (1) The 
conductors on a cross-connecting board 
which serve to connect the sections of a 



Cro.] 



732 



[Cry. 



switch-board with the wires leading to a 
cable. (3) The conductors which connect 
corresponding commutator segments in a 
cross-connected armature. 

Cross-Connecting Telephone Switch- 
board. — A telephone distributing board. 

Cross-Connecting Trough.— A trough 
dividing a telephone test board from a 
distributing board, formed for holding the 
joints in the cross-connections between 
them. 

Cross-Connection of Armature Wind- 
ings. — Armature windings in which the 
wires are interconnected at the corre- 
sponding segments of the commutator. 

Cross-Connection of Commutator.— 
The interconnection of the armature coils 
to corresponding commutator segments. 

Cross Current.— Current passing between 
the armatures of alternating current 
generators, or motors, operated in parallel, 
and due to differences in the phase or 
magnitude of the E. M. Fs. in the ma- 
chines. 

Cross Fire. — (1) A term employed in tel- 
ephony or telegraphy for an escape or leak- 
age of current from one line to another, 
due to defective insulation. (2) Cross talk. 

Cross, Electric— (1) A connection, gen- 
erally metallic, accidentally established 
between two conducting lines. (2) A de- 
fect in a telegraph, telephone, or other 
circuit, caused by two wires coming into 
contact by crossing each other. 

Cross Induction.— (1) An induction pro- 
duced by the armature current whose 
magnetization is at right-angles to that 
produced by the field. (2) Cross magneti- 
zation. 

Cross-Induction of Dynamo Arma- 
ture. — Cross magnetization produced by 
a dynamo armature. 

Cross Magnetization.— A magnetization 
set up by the currents circulating in the 
armature turns, which is at right-angles 
to the magnetization set up by the field 
flux. 

Cross-Over Block.— A device to permit 
the safe crossing of one wire over another 
in moulding or cleat wiring. 

Cross System. — A system of running over- 
head wires for the purpose of preventing 
mutual inductive disturbances, which con- 
sists in crossing or transposing the position 
of wires on the pole arms at suitable in- 
tervals, as distinguished from the twist 
system. 

Cross-Talk.— (1) Cross-fire conversation 
over one telephone circuit which is heard 
in neighboring telephone circuit. (2) In- 



terference between neighboring tele- 
phone circuits. 

Cross-Wire-Suspension for Arc Lamp. 
Suspension of an arc-lamp by means of 
a pulley and cord, attached to a block and 
tackle suspended from a suitably sup- 
ported cross wire. 

Crossing Cleat. — A cleat so arranged as- 
to permit the crossing of one pair of wires 
under or over another pair without con- 
tact with each other. 

Crossing Frog. — A frog sometimes em- 
ployed in place of a trolley cross-over. 

Crossing Wires.— (1) A device employed 
in telegraphic circuits whereby a faulty 
conductor is cut out of the line circuit, by 
crossing it over to a neighboring less- 
used line. (2) In telegraphy, interchang- 
ing sections of wire between two way 
stations, so as to remove a fault from a 
circuit or to rearrange a circuit passing 
through the stations. 

Crow-Foot Zinc. — A crow-foot-shaped 
zinc employed in the gravity voltaic cell. 

Crown Telephone Receiver.— A tele- 
phone receiver in which a number of 
permanent steel magnets are arranged in 
the form of a crown, all the poles of the 
same name centring at the soft-iron pole- 
piece carrying the coil, and the opposite 
coils being joined to the rim of the dia- 
phragm. 

Crucible, Electric— (1) A crucible suit- 
able for electro-metallurgical operations. 
(2) A crucible in which the heat of a vol- 
taic arc, or of electric incandescence, is 
employed, to perform difficult fusions, to 
effect the reduction of metals from their 
ores, or to form alloys. 

Crystal. — A solid body bounded by sym- 
metrically disposed plane faces. 

Crystalline Electro-Metallurgical De- 
posit. — A non-adherent, non-coherent 
film of electrolytically deposited metal. 

Crystallization.— Solidification from solu- 
tion or fusion in definite forms. 

Crystallization by Electrolytical De- 
composition. — Crystalline deposition of 
various metals by the passage, under cer- 
tain conditions, of an electric current 
through solutions of their salts. 

Crystallize. — To separate from a liquid or 
vapor in the form of a crystalline solid. 

Crystalloid. — Those portions of a mixed 
substance subjected to dialysis, that are 
capable of crystallization. 

Cryptoscope. — (1) An apparatus consist- 
ing of a fluorescent screen placed at one* 
end of a light-tight pasteboard tube, and. 



Cry.] 



733 



[Cur. 



viewed at the other end through an eye- 
piece. (2) A fluoroscope. 

Cryptoscopic Screen.— (1) The screen 
employed in cryptoscopy. (2) A fluores- 
cent screen. 

Cryptoscopy. — The art of examining the 
body by means of a cryptoscope. 

Cube Knot. — A unit of volume sometimes 
employed in calculations of insulation 
resistance of submarine cables. 

Cubic Energy. — A term sometimes em- 
ployed for voluminal energy. 

Cup Brush. — A brush suitably shaped for 
polishing the interior surface of a cup or 
other similar surface of an object that is 
to be electroplated. 

Cupric Electrolysis. — In electro-thera- 
peutic treatment, electrolysis performed 
with copper electrodes whereby a salt of 
copper is carried into the tissues under 
the anode by cataphoric action. 

Curb Key.— A telegraphic key employed 
in curb signalling. 

Curb Sender. — An automatic transmitter 
employed in submarine telegraphy, which 
is operated by a punched paper strip and 
which sends curbed signals into the cable. 

Curb Signalling. — In cable telegraphy, a 
system for reducing the effects of retarda- 
tion and increasing the speed of signal- 
ling, by following each signalling current 
with a definite sequence of reversed cur- 
rents or earthings. 

Curbed Signals.— Signals sent by means 
of a curb key. 

Curbing. — Employing curb signalling. 

Curl.— (1) The vector part of the nabla of a 
vector point-function. (2) The line inte- 
gral of a vector once around any closed 
loop, and equal to the surface integral of 
a related vector passing through the loop. 
(3) The rotation or spin of a vector point- 
function. (4) A vector which indicates by 
its direction the plane, and by its length 
the magnitude, of the maximum vector 
rate-of -change of a vector point-function 
in the neighborhood of a given point. 

Current Accumulator. — Any apparatus 
in which the strength of an electric cur- 
rent is increased by the motion past it of 
a conductor, the currents produced in 
which tend to strengthen and increase 
the current which causes the induction. 

Current Balance. — A general name given 
to a variety of ampere balance which 
gives readings in various decimals or mul- 
tiples of amperes, and which determines 
the strength of current passing, through 
its action on a movable ring or coil placed 
between two fixed rings or coils. 



Current Calorimeter.— An electric ca- 
lorimeter. 

Current Commuter.— (1) Any device that 
causes alternating currents to flow in one 
and the same direction. (2) A commu- 
tator. 

Current-Conveying Helix.— An active 
helix. 

Current Density. — (1) The current 
strength which passes in any part of a cir- 
cuit, divided by the area of cross-section 
of that part of the circuit. (2) The ratio 
of the current strength through any 
surface of section of active conductor to 
the area of that surface, assumed perpen- 
dicular to the current. 

Current Distribution.— The spreading or 
ramification of electric currents through 
a conducting mass or network. 

Current Direction-Indicator. — An in- 
strument for insertion in an arc or other 
circuit to indicate whether the proper 
direction of current is maintained. 

Current Diverter for Electric Rail- 
ways. — A term sometimes given to the 
rheostat employed in starting and regulat- 
ing a street-car motor. 

Current Efficiency of Storage Battery. 
The ratio between the total useful elec- 
tric quantity delivered by a charged stor- 
age battery to the working circuit, to the 
total electric quantity employed in charg- 
ing the battery. 

Current, Electric— (1) The quantity of 
electricity per-second which passes 
through any conductor or circuit, when 
the flow is uniform. (2) The rate at which 
a quantity of electricity flows or passes 
through a circuit. (3) The ratio, ex- 
pressed in terms of electric quantity per- 
second, existing between the electro- 
motive force causing a current and the 
resistance which opposes it. 

Current Equalizer for Storage Bat- 
tery. — A device for controlling the 
strength of the charging or discharging 
circuit of a storage battery. 

Current Filaments. — A term sometimes 
employed in place of current streamlets. 

Current Governor.— (1) A current regu- 
lator. (2) Any device, whether auto- 
matic or non-automatic, for maintaining 
constant the current strength in any 
circuit. 

Current Induction.— A term sometimes 
used for voltaic induction. 

Current Meter. — (1) Any form of current 
galvanometer. (2) An indicating amme- 
ter or recording ampere-hour meter. 



Cur.l 



734 



[Cut. 



Current Recording-Meter.— A record- 
ing ammeter. 

Current Retarder. — A term sometimes 
employed for rheostat. 

Current Reverser. — (1) A switch or other 
apparatus designed to reverse the direc- 
tion of a current. (2) A current changer. 

Current Rush. — The impulsive rush of 
current that occurs when a transformer 
is first switched on, or connected with, an 
alternating-current circuit. 

Current Sheet. — The area of active con- 
ducting surface carrying a current con- 
sidered as though the current existed as 
a material sheet. 

Current Spiral. — A conducting helix or 
spiral provided for the passage of a cur- 
rent. 

Current Streamlets. — A conception of a 
series of parallel current streams or cur- 
rent filaments flowing through a solid con- 
ductor. 

Current Strength.— (1) In a direct-cur- 
rent circuit the quotient of the total elec- 
tromotive force divided by the total re- 
sistance. (2) The time-rate-of-flow in a 
circuit expressed in amperes, or coulombs 
per second. (3) In an alternating current 
the quotient of the total electromotive 
force divided by the impedance. 

Current System of Induction Teleg- 
raphy. — A system of induction teleg- 
raphy on railroads, depending on current 
induction between a fixed circuit along 
the roadway, and a parallel circuit on the 
moving train. 

Current Teaser, Electric— A coil of 
thin wire placed on the field magnets of 
a dynamo-electric machine in addition to 
the series coils wound thereon, and con- 
nected as a shunt across the main cir- 
cuit. 

Current Transformation.— (1) The act 
of changing the strength of a current by 
changes effected in its electromotive force. 
(2) The act of changing a direct into an 
alternating current, or the reverse, or a 
uniphase-alternating current into a mul- 
tiphase-alternating current. 

Current Transformer.— A device for 
changing in one circuit the strength of 
current which flows in another. 

Current Turns. — (1) The product of the 
number of turns in a coil by the current 
flowing through them. (2) A word some- 
times used for ampere-turns. 

Current Wave. — (1) The progressive elec- 
tro-magnetic disturbance in the ether sur- 
rounding a conducting wire forming part 
of a circuit. (2) The progressive disturb- 



ance of electric flow traversing a con- 
ducting circuit, under the influence of 
a variation in its impressed electromotive 
force. 

Current Weigher.— (1) A current bal- 
ance. (2) An ammeter in which the 
electro-magnetic force of the current is 
compared with the earth's gravitational 
force on a mass. 

Currents of Motion. — A term sometimes 
employed in electro-therapeutics for the 
electric currents that are asserted to 
traverse healthy muscle or nerve tissue, 
during the sudden contraction or relaxa- 
tion of such muscle and nerve. 

Currents of Rest.— A term sometimes 
employed in electro-therapeutics for the 
electric currents that are asserted to trav- 
erse healthy muscle or nerve tissue while 
the muscles are passive. 

Curve Guy-Poles.— Anchor poles or pull- 
offs, employed in an overhead-trolley 
system, placed at a curve or turn-out, to 
which are attached the wire guys em- 
ployed to preserve the proper tension for 
the conductor at these points. 

Curve of Sines.— (1) A curve representing 
at continuous successive positions the 
successive values of the sines of a pro- 
gressively varying angle. (2) A sinusoid. 
(3) When drawn to rectangular co-ordi- 
nates, a curve successively rising above 
and falling below the axis of abscissas cor- 
responding to the sines of angles measured 
along said axis. 

Curve of Cross-Over System.— In a sys- 
tem of transposition for overhead wires, 
in order to avoid the effects of induction, 
the short bend of wire which effects the 
transposition at a pole cross-arm. 

Cushioning Chamber.— In a dead-beat 
mirror galvanometer, a chamber before 
or behind a suspended mirror, for the 
purpose of dampening the motions of the 
latter. 

Cut-in. — To introduce an electro-receptive 
device into the circuit of a source by 
completing or closing the circuit through 
it. 

Cut-in. —(1) A term sometimes employed 
for filament cut-out. (2) An automatic 
guard cut-out. 

Cut-Off. — Any device for cutting a battery 
or other electric source from a circuit, or 
from part of a circuit. 

Cut-Out. — To remove an electro-receptive 
device or loop from the circuit of an elec- 
tric source. 

Cut-Out. — (1) A device for removing an 
electro-receptive device or loop from the 



Cut.] 



'35 



[D. P 



circuit of an electric source. (2) A safety 
fuse. 

Cut-Out Board. — A board supporting a 
number of fuse cut-outs. 

Gut-Out Block. — A block containing a 
fuse wire or safet} r catch. 

Cut-Out Box. — A box containing a cut- 
out. 

Cut-Out Cabinet. — Any enclosed space 
provided in a building for the reception 
of cut-outs or fuses. 

Cut-Out Switch. — A short-circuiting 
switch by means of which an arc-light 
is cut out from its feeding circuit. 

Cutting and Holding Grapnel.— In 
submarine telegraphy, a grapnel which, 
after engaging a cable on the sea bottom, 
automatically grips the cable, and cuts it 
beyond the grip. 

Cutting Lines of Magnetic Force. — 
Passing a conductor through lines of 
magnetic force or flux, or passing mag- 
netic lines of force or flux through a con- 
ductor, so as to cut or intersect such lines 
or such flux. 

Cycle. — (1) A succession of events which 
periodically recur, reckoning from any 
stage of the disturbance to the moment 
at which that stage next occurs. (2) A 
complete recurrence of any periodic 
change. 

Cycle of Alternations.— The cycle of 
a periodically-alternating electromotive 
force, current or flux. 

Cycle of Magnetization.— -A single com- 
plete passage of any magnetic substance 
through the successive stages of a period- 
ically-recurring magnetic change. 

Cyclic. — Of or pertaining to a cycle. 

Cyclic Magnetization. — Magnetization 
produced in a magnetic substance w T hen 
subjected to periodic cyclic changes in 
the magnetizing force. 

Cyclic Magnetic Variations. — Secular 
magnetic variations occurring during 
great cycles of time. 

Cyclic Motion. — Any motion which re- 
occurs in a cycle. 



Cyclic Stability.— (1) In an alternating- 
current circuit the condition of uniform 
periodic motion in alternating quantities, 
such as pressure and current, attained 
after a definite number of cycles from the 
starting of the motion ; as distinguished 
from the variable state of motion when 
the circuit is first closed. (2) The per- 
manent state in an alternating-current 
circuit. 

Cyclometer. — An instrument for record- 
ing the number of turns completed by 
a wheel, shaft, drum, or other rotating 
device, or for indicating the distance 
traversed by its periphery. 

Cyelosis. — The existence of independent 
cycles in a diagram. 

Cyclotrope. — A word proposed for trans- 
former or converter. (Not in use.) 

Cylindrical Armature. — A term some- 
times applied to a drum armature. 

Cylindrical Carbon Electrodes.— Car- 
bon cylinders employed for the electrodes 
of arc lamps or for battery plates . 

Cylindrical Core.— (1) A cylindrical- 
shaped mass of iron employed for the 
core of a solenoid or helix. (2) A cylin- 
drical-shaped mass of soft carbon em- 
ployed in cored electrodes. 

Cylindrical Electro-Magnet.— An elec- 
tro-magnet whose core consists of a 
hollow cylinder provided with a slot 
extending parallel to its axis. 

Cylindrical Magnet.— A cylindrically 
shaped magnet. 

Cylindrical King- Armature. —A ring 
armature whose core has the shape of 
a long cylinder. 

Cylindrical Vibrator. — A weight in the 
form of a cylinder supported by a suspen- 
sion for the purpose of measuring its 
torsional rigidity. 

Cymogene. — An extremely volatile liquid 
hydrocarbon given off from crude coal-oil 
during the early stages of its distillation. 

Cystoscopy, Electric. — The examination 
of the human bladder by electric illu- 
mination. 



D 



d. — A symbol for diameter. 

D. B. Switch. — A contraction for double- 
break switch. 

D. C. — A contraction for direct current. 
D. E. M. F.— A contraction for direct- 
electromotive force. 
"D." Operator.— A term employed in 



mathematics for the operator which ef- 
fects the total differentiation of a func- 
tion with respect to time. 

D. P. Cut-Out. — A contraction for double- 
pole cut-out. 

D. P. Switch. — A contraction for double^ 
pole switch. 



D.Q.] 



736 



[Dea. 



D. Q. — In submarine telegraphy, a signal 
serving to separate the address from the 
text of the message. 

Daily Variation of Magnetic Needle. 
The diurnal variation of the magnetic 
needle. 

Damped Galvanometer.— A galvano- 
meter whose movable part — i. e., whose 
needle or coil — when moved, comes to rest 
as quickly as possible. 

Damped Magnetic Needle.— A magnetic 
needle so placed as to come quickly to 

. rest after it has been set in motion. 

Damped Vibrations. — (1) Vibrations that 
occur under circumstances in which the 
vibratory or swinging motions can be at 
once brought to rest, instead of repeatedly 
swinging to-and-fro, on the removal of the 
force causing the vibration. (2) Vibra- 

< tions of successively diminishing ampli- 
tude. 

Dampening Factor.— The property of an 
oscillatory alternating-current circuit of 
diminishing the amplitude of its oscilla- 
tions owing to the influence of electric 
resistance or of radiation. 

Damper. — (1) A metallic cylinder so ar- 
ranged as to partially or completely sur- 
round the iron core of an induction coil 
for the purpose of varying the intensity 
of the currents produced in the secondary. 
(2) A dash-pot, or similar apparatus, pro- 
vided for preventing the too sudden 
movements of a lever or other part of 
a moving device. (3) Any device em- 
ployed for damping a magnetic needle. 

Damping.— (1) The act of stopping a sudden 
vibratory motion without waiting for it 
to cease after repeated swingings to-and- 
fro. (2) The act of causing a periodically 
moving body to lose its energy of motion 
by the application of retarding forces. 

Damping Coil for Galvanometer.— 
(1 ) An auxiliary coil employed with a gal- 
vanometer for receiving transient electric 
currents from a key under the control of 
an observer, for the purpose of checking 
the motion of the needle. (2) A short-cir- 
cuited coil, on or near a movable electro- 
magnetic system, for the purpose of 
damping its oscillations by the action of 
electric currents induced therein. 

Damping, Electric. — A term sometimes 
employed for the decrease in the intensity 
of the electric oscillations produced in a 
resonant circuit by electric resistance, 
under circumstances where some of the 
higher overtones are set up in the circuit. 

Damping Magnet. — Any magnet em- 
ployed for the purpose of checking the 
motions of a moving body or magnet. 



Damping Suspension. — A suspension 
which is rendered dead-beat, or aperiodic, 
by the application of any retarding force 
or damping mechanism. 

Damping Tube.— (1) A tube fitted with a 
glass cap and placed in an instrument to 
diminish the cavity in which a movable 
system swings, and thus damp its motion. 
(2) A conducting tube attached to a 
movable system and placed in the vicin- 
ity of fixed permanent magnets, in order 
to damp the vibrations of the system. 

Damping Vessel.— A dash-pot. 

Daniell's Voltaic Cell.— A zinc-copper 
couple whose elements are immersed re- 
spectively in electrolytes of dilute sul- 
phuric acid and a saturated solution of 
copper sulphate. 

Dark Discharge.— A term applied by 
Faraday to that portion of the convective 
discharge which occurs, under certain cir- 
cumstances, in the rarefied gas of an 
exhausted chamber between the positive 
and negative electrodes. 

Dark-Light Frequencies. — Ether vibra- 
tions of the nature of light whose 
frequencies are too low to produce 
physiologically effective light. 

Dark-Segment of Aurora.— A dark or 
non-illumined portion of an aurora glory, 
or crown of auroral light. 

Dash-Pot. — A mechanical device for pre- 
venting a too sudden motion in the 
movable part of any apparatus. 

Day Load. — A load on an apparatus, 
machine, or central station, occurring 
during the daytime as distinguished from 
a night load. 

Day of Magnetic Disturbance.— A day 
during which the mean departure of the 
reading of a declinometer at any place, 
from the normal monthly value at that 
place, is at least one and one-half times 
the average. 

Daylight Color- Values. — Such values of 
luminous frequencies as correspond to 
those present in ordinary sunlight or day- 
light. 

Dead - Beat. — (1) Heavily damped. (2) 
Aperiodic. (3) Such a motion of a gal- 
vanometer needle, or other suspension 
system, in which the needle moves sharply 
from point to point and comes quickly to 
rest. 

Dead-Beat Discharge. — A non-oscilla- 
tory discharge. 

Dead-Beat Galvanometer.— (1) An aperi- 
odic galvanometer, or one whose needle 
comes quickly to rest instead of repeat- 



Dea.] 



737 



[Dee, 



edly swinging to-and-fro. (2) A heavily- 
damped galvanometer. 
Dead Beatness. — Possessing the property 
of aperiodicity. 

Dead Dipping. — Dipping in acid liquids 
for the purpose of obtaining a dead or 
unpolished surface on an electro-metal- 
lurgical coating or deposit. 

Dead Earth. — (1) A fault in a telegraphic 
or other line, in which the line is thor- 
oughly grounded or connected with earth. 
(2) A total earth. (3) An earth of inap- 
preciable or insignificant resistance. 

Dead-Ended Conductor or Wire.— A 
conductor or wire whose end is deliber- 
ately left open or insulated, as, for ex- 
ample, by being wound around an 
insulator. 

Dead Ending. — Leaving a conductor 
dead-ended. 

Dead Ground or Grounding.— Such a 
grounding as will ensure a ground of 
negligible resistance. 

Dead Man. — A support for raising a pole 
and supporting it in place while securing 
it in the ground. 

Dead Points of Motor Armature.— Any 
positions of a motor armature when at 
rest, in which the driving current cannot 
start it. 

Dead Resistance for Testing Bank. — 
(1) A resistance for a testing bank devoid 
of inductance. (2) An inductionless re- 
sistance . 

Dead Wires.— (1) Any disused wires or 
abandoned wires, generally aerial. (2) A 
term applied to that portion of the wire on a 
dynamo which produces no electromotive 
force on its movements through the field 
flux. (3) That part of the wire on a motor 
■which produces no useful effect on the 
passage through it of a driving current. 

Dead Wires of Dynamo Armature.— 
The wires on the armature of a dynamo 
or motor which produce no useful elec- 
tromotive force or resulting current on 
the movement of the armature through 
the field of the machine. 

Dead Wires on Motor Armature.— The 
wires on the armature of a motor which 
produce no useful torque on the passage 
through them of an electric current. 

Death, Electric. — Death resulting from 
the passage of an electric discharge or cur- 
rent through the human body. 

Decalescence. — An absorption of sensible 
heat that occurs at a certain time during 
the heating of a bar of steel. 

47 



Decay of Waves.— The diminution in the 
amplitude of waves due to obstruction of 
any kind. 

Deci. — A prefix for the one-tenth part. 

Deci-Ampere. — One-tenth of an ampere. 

Deci- Ampere Balance.— A balance form 
of ammeter whose scale is graduated to 
give direct readings in deci-amperes. 

Deci-Lux.— The one-tenth of a lux. 

Deci-Polar Dynamo. — A dynamo whose 
field is produced by ten magnet poles. 

Decimal Candle.— A photometric stand- 
ard equal to the twentieth part of the 
Violle platinum standard. 

Deck Cable-Lead. — Guide pulleys or 
leads, placed at suitable intervals on the 
deck of a cable ship, extending from a 
tank to the bow or stern sheaves, to aid in 
laying a submarine cable. 

Deck-Planer, Electric. — An electrically 
driven rotary cutter or planer, suitable 
for planing the deck of a ship. 

Deflection of Magnet. — The variation of 
a magnetic needle from the true geograph- 
ical North. 

Deflection Compass. — A declinometer. 

Declinometer. — A magnetic needle suita- 
bly arranged for the measurement of the 
magnetic declination or variation of any 
place. 

Decohere. — To restore or regain the nat- 
ural condition of a coherer. 

Decomposition. — The separation of a 
molecule into its constituent ions or radi- 
cals, or into its ultimate atoms. 

Decomposition, Electric. — Chemical de- 
composition effected by means of an elec- 
tric discharge or current. 

Decomposition, Electrolytic— The sep- 
aration of a molecule into its consti- 
tuent ions or radicals by the action of an 
electric current. 

Decorative Series Lamps.— Series-con- 
nected incandescent lamps employed to 
obtain decorative effects. 

De-Energize. — To deprive an electro- 
receptive device of its operating current. 

De-Energizing. — Depriving an electro- 
receptive device of its operating current. 

Deep Sea-Cable.— That portion of a sub- 
marine cable which is laid in the deep 
water, at a distance from the coast or 
shore. 

Deep - Seated Eddy - Currents. — The 
eddy currents that are set up in the mass 
of a conductor subjected to electro- 
dynamic induction, as distinguished 



Beeo] 



738 



[Dem, 



from the superficially - seated eddy-cur- 
rents. 

Deep- Water Submarine-Cable.— A deep 
sea cable. 

Defective-Loop Repeater. — (1) A device 
for employing the good wire of a defective 
loop to an office, to receive and transmit 
alternately, on a duplex, or on the com- 
mon side of a quadruplex set. (2) A re- 
peater connecting a branch office with a 
duplex or quadruplex set at a main 
office, and arranged to operate on a single 
wire of a pair or loop to said branch office 
when the other wire becomes defective. 

Deflagration. — A violent but not explo- 
sive combustion of a substance. 

Deflagration, Electric. — The fusion and 
volatilization of metallic substances by 
the passage through them of an electric 
current. 

Deflagrator. — The name given to a partic- 
ular voltaic battery of small internal 
resistance, employed, in the early history 
of the voltaic battery, for the electric de- 
flagration of metallic substances. 

Deflecting Magnet. — (1) The permanent 
magnet of a magnetometer, employed for 
deflecting a small magnetic needle sus- 
pended at a definite distance, in order to 
compare its influence with that of the 
earth's horizontal magnetic force. (2) The 
compensating magnet of a galvanometer. 

Deflection Method. — A method employed 
in electrical measurements in which, as 
distinguished from the zero method, the 
amount of the deflection produced on any 
instrument, by a given current or a given 
charge, is utilized for determining the 
value of that current or charge. 

Deflection of Cable Dynamometer.— 
(1) The sag, or distance to which a cable 
dynamometer sheave descends below the 
horizonal line corresponding to infinite 
tension. (2) The sag of a dynamometer 
sheave which increases as the strain on 
the cable diminishes. 

Deflection of Magnetic Needle.— The 
movement of a needle out of a position of 
rest, either in the earth's magnetic field, 
or in the field of another magnet, by the 
action of the flux of an electric current or 
of a magnet. 

Deformation.— (1) Any displacement of 
the particles of a solid with reference to 
one another, produced by the action of a 
stress. (2) A strain. 

Degeneration of Cell.— Such a change 
in the muscular or cellular structure of a 
cell that incapacitates it from performing- 
its ordinary functions. 



Degeneration of Energy.— A degrada- 
tion of energy. 

Deka. — A prefix signifying ten times. 

Deka- Ampere. — Ten amperes. 

Deka- Ampere Balance.— A balance-form 

of ammeter measuring tens of amperes 

(0 to 100 amperes.) 

Deliquescence. — The solution of a crys- 
talline solid arising from its absorption of 
the vapor of water from the atmosphere. 

Delivered Power. — In a system of elec- 
trical transmission, the power that is 
delivered at one end of a line as distin- 
guished from the power sent into the line 
at its other end. 

Delta Connection. — The connection of 
circuits employed in a delta triphase- 
system. 

Delta Current.— (1) The current between 
adjacent wires or terminals of a triphase- 
system. (2) The ring current. 

Delta Potential of Triphase System.— 

(1) The effective difference of potential, 
or voltmeter pressure, between adjacent 
wires or terminals of a triphase-system. 

(2) The ring potential. 

Delta Triphase-System. — A triphase 
system in which the terminal connections 
resemble the Greek letter delta, or 
triangle. 

Demagnetizable*. — Capable of being de- 
prived of magnetism. 

Demagnetization. — The act of depriving 
a magnet of its magnetism. 

Demagnetization by Successive Re- 
versals. — A process for removing the 
magnetism from a mass of steel, as in a 
watch, by subjecting it to many success- 
ive magneto-motive forces alternating 
in direction and gradually diminishing to 
zero. 

Demagnetize. — To deprive of magnetism. 

Demagnetizing.— Depriving of magnet- 
ism. 

Demagnetizing Current.— The current 
which serves to remove the magnetization 
of some magnetic device. 

Demagnetizing Lines of Flux.— Mag- 
netic flux produced by a magnetized bar 
in a direction opposite to the magnetizing 
force, and tending, therefore, to demag- 
netize the bar. 

Demand Recording-Meter.— A meter 
which registers the maximum demand 
for electric energy, usually a meter which 
registers the maximum current strength 
supplied through it, in addition to the 
total quantity of electricity delivered. 



Dem.] 



739 



[Dia. 



Demarcation Current.— A term some- 
times applied to the electric current ob- 
tained from an injured muscle. 

Density, Electric. — The quantity of free 
electricity on any unit of area of surface 
of a charged body. 

Density of Charge. — The quantity of 
electricity per-unit-of-area at any part of 
a charged surface. 

Density of Current. — The quantity of 
current that passes per-unit-of-area of 
cross-section in any part of a circuit. 

Density of Electrification.— The density 
of an electrostatic charge. 

Density of Field.— The quantity of mag- 
netic flux that passes through any field 
per-unit-of-area of cross-section. 

Dentiphone. — An audiphone. 

Dephased.— (1) Differing in phase. (2) 
Caused to differ in phase. 

Depolarization. — The act of reducing or 
removing the polarization of a voltaic 
cell or battery. 

Depolarize. — To deprive of polarization. 

Depolarizer. — The material employed in 
voltaic cells for the purpose of depolar- 
izing them. 

Depolarizing. — Depriving of polarization. 

Depolarizing Fluid or Liquid. — An 
electrolytic fluid or liquid employed in a 
voltaic cell for the purpose of preventing 
or lessening polarization. 

Depositing Cell or Vat.— Any electro- 
lytic cell in which an electro-metallur- 
gical deposit is made. 

Deposition, Electric— The deposit of a 
substance, generally a metal, by the action 
of electrolysis. 

Deprez-D' Arson val Galvanometer.— A 
form of dead-beat galvanometer. 

Derivation.— (1) A shunt or derived cir- 
cuit. (2) A leak. 

Derivative or Derived Current.— The 
current that flows through a branch or 
derived circuit. 

Derived Circuit.— (1) A branch or shunt 
circuit. (2) A derivation. 

Derived-Circuit Arc-Lamp.— The name 
sometimes employed for a differential arc- 
lamp. 

Derived Units. — Various secondary units 
obtained or derived from the fundamental 
units of length, mass, and time. 

Desk Loop. — (1) In telegraphy, a loop or 
circuit, running to a desk in a telegraph 
office, and connecting the apparatus on 
such desk with main-line apparatus at 
some other table. (2) A circuit connect- 



ing an operator at one desk with a duplex 
or quadruplex set of apparatus at another 
desk for convenience in handling the 
traffic. 

Desk Push. — An electric push attached 
to a desk for the purpose of ringing a call- 
bell, or closing some other electric circuit. 

Desk Set. — Telephone apparatus arranged 
for use on a desk. 

Destructive Distillation. — The action of 
heat on an organic substance while out of 
contact with air, resulting in the decom- 
position of the substance into simpler and 
more stable compounds. 

Detector Galvanometer.— Any rough 
form of galvanometer or galvanoscope 
employed for detecting the presence of 
electric currents. 

Detector Peg. — A peg used in connection 
with a detector galvanometer. 

Detonating Fuse.— (1) A fuse that is ex- 
ploded b} r a percussion or blow. (2) A 
percussion fuse. 

Detorsion Bar. — A bar placed in a mag- 
netic declinometer for the purpose of re- 
moving the torsion on the suspending 
thread of the magnet. 

Developed Winding. — A winding of a 
dynamo-electric machine developed or 
expanded upon a drawing or plane. 

Devil Claws. — A device employed in 
stringing overhead wires. 

Dextrorsal Helix. — A name sometimes 
applied to a dextrorsal solenoid. 

Dextrorsal Solenoid. — A solenoid whose 
winding is right-handed. 

Diacritical Current. — Such a strength of 
a magnetizing current as produces a mag- 
netization of an iron core equal to one- 
half saturation. 

Diacritical Number. — Such a number of 
ampere turns at which a given core would 
receive a magnetization equal to one- 
half saturation. 

Diacritical Point of Magnetic Satu- 
ration. — A term proposed for such a 
value of the co-efficient of magnetic satu- 
ration that its core is magnetized to ex- 
actly one-half of its possible maximum 
magnetization. 

Diagometer. — An apparatus in which an 
attempt is made to determine the chemi- 
cal composition, and consequent purity, of 
certain substances by their electrical con- 
ducting powers. 

Dial Bridge or Rheostat. — A resistance 
bridge or rheostat whose contact points 
are arranged in the shape of a dial. 



Dia.] 



740 



[Die. 



Dial Telegraph. — A general term embrac- 
ing the apparatus employed in dial teleg- 
raphy. 

Dial Telegraphy. — A system of teleg- 
raphy in which the messages are received 
by the movements of a needle over a dial 
plate. 

Dialysis. — The act of separating a liquid 
mixture into its crystalloids and colloids 
by passing the liquid through a mem- 
brane. 

Dialyzing. — Subjecting to the process of 
dialysis. 

Diamagnetic.— The property possessed by 
substances like bismuth, phosphorus, 
antimony, zinc and others, of being ap- 
parently repelled when placed between 
the poles of powerful magnets. 

Diamagnetic Permeability.— The per- 
meability to magnetic flux possessed by 
diamagnetic substances. 

Diamagnetic Polarity. — A polarity, the 
reverse of ordinary magnetic polarity, the 
existence of which was assumed to ex- 
plain the phenomena of diamagnetism. 

Diamagnetically. — In a diamagnetic 
manner. 

Diamagnetism. — A name sometimes given 
to the magnetism of diamagnetic bodies. 

Diamagnetized. — Subjected to the action 
of so-called diamagnetism. 

Diamagnetometer. — A magnetometer 
designed for the study of diamagnetism. 

Diamagnets. — Diamagnetic substances 
subjected to magnetic induction, and 
formerly called diamagnets in contra- 
distinction to ordinary or paramagnets. 

Diameter of Commutation. — (1) The 
diameter of the commutator cylinder of a 
dynamo at which the brushes are applied. 
(2) That diameter on the commutator 
cylinder of an open-circuited armature, 
which joins the points of contact of the 
collecting brushes. 

Diaphragm. — (1) A sheet of an elastic 
solid, generally circular in shape, securely 
fastened at its edges and capable of being 
set into vibration. (2) The porous wall or 
septum of an endosmometer. (3) The 
porous partition of a voltaic cell. (4) A 
disc of blackened metal provided with 
a circular aperture and employed for 
cutting off all the light from a lens except 
that falling on its central portions. 

Diaphragm Currents.— Electric currents 
produced by forcing a liquid through the 
capillary pores of a diaphragm. 

Diaphragm ofVoltaic Cell.— (1) The 
porous partition or plate of a voltaic cell. 
(2) Generally, a porous cell. 



Diaphragm Photometer.— A photometer 
which depends on the equality of the 
brightness obtained on the two halves of a 
diaphragm or screen, either by varying 
the distances of the lights from the screen 
or by varying the inclination of the 
luminous rays thereon. 

Dice-Box Insulator. — A name sometimes 
applied to a double-cone insulator. 

Dielectric. — Any substance which permits 
electrostatic induction to take place 
through its mass. 

Dielectric Absorption. — The absorption 
of a charge or current by a dielectric. 

Dielectric Capacity. — A term employed 
in the same sense as specific inductive 
capacity. 

Dielectric Circuit.— A circuit formed in 
whole or in part through a dielectric as 
opposed to a conducting circuit. 

Dielectric Constant.— A term sometimes 
employed in place of specific inductive 
capacity. 

Dielectric Current.— (1) The rate-of -in- 
crease of the polarization of a dielectric 
produced by a change in the polariza- 
tion through the circuit. (2) A displace- 
ment current. 

Dielectric Density of a Gas. — A term 
sometimes employed instead of dielectric 
strength of a gas. 

Dielectric Displacement.— (1) Electric 
displacement taking place through a die- 
lectric. (2) The electromotive intensity in 
a dielectric multiplied by 4tt and divided 
by the dielectric co-efficient. 

Dielectric Elasticity.— (1) The reciprocal 
of the dielectric co-efficient. (2) The 
measure of the electric force that must be 
exerted upon a dielectric in order to effect 
unit displacement. 

Dielectric Energy Current.— That com- 
ponent of an alternating current passing 
through a condenser which is in phase 
with the impressed E. M. F. at its termi- 
nals. 

Dielectric Hysteresis.-(l) A variety of 
molecular friction, analogous to magnetic 
hysteresis, produced in a dielectric under 
changes of electrostatic stress. (2) That 
property of a dielectric by virtue of which 
energy is consumed in reversals of electri- 
fication. 

Dielectric Hysteretic Admittance.— 

(1) In an alternating-current circuit the 
apparent component of admittance due to 
dielectric hysteresis. (2) In a condenser 
traversed by an alternating current the 
admittance, which is the geometrical sum 
of the hysteretic conductance and the hy- 



Die.] 



741 



[Dif. 



steretic susceptance, or whose reciprocal is 
the vector hy steretic impedance. 

Dielectric Hysteretic Impedance.— In 
an alternating-current circuit, the ap- 
parent component of impedance due to 
dielectric hysteresis. 

Dielectric Hysteretic Lag.— Lag in an 
alternating-current circuit due to dielec- 
tric hysteresis. 

Dielectric Medium.— Any medium ca- 
pable of acting as a dielectric. 

Dielectric Polarization.— (1) The polari- 
zation of a dielectric by means of which 
electric induction takes place. (2) Dielec- 
tric displacement. 

Dielectric Resistance. — (1) The resist- 
ance which a dielectric offers to mechan- 
ical strains produced by electrification. 
(2) The resistance of a dielectric to dis- 
placement currents. 

Dielectric Static Hysteresis. — Hystere- 
sis occurring in a dielectric under succes- 
sive electric reversals, and due to a quasi- 
electrostatic friction independent of the 
rate of reversal, as distinguished from 
dielectric viscous hysteresis which varies 
with the frequency of cyclic electric re- 
versals. 

Dielectric Strain.— (1) The strained con- 
dition of the glass or other dielectric of a 
condenser produced by the charging of 
the condenser. (2) The deformation of a 
dielectric under the influence of an elec- 
tro-magnetic stress. 

Dielectric Strength of Gas.— The elec- 
tromotive intensity a gas is capable of 
bearing without permitting a disruptive 
discharge to pass through it, and capable 
of measurement in volts per centimetre. 

Dielectric Stress. — (1) The electro-mag- 
netic force producing a deformation or 
strain in a dielectric. (2) Electromotive 
intensity. 

Dietrine. — A name given to a variety of 
insulating material. 

Difference of Potential. — That quanti- 
tative property in space by virtue of 
which work is done when a mass of any 
kind is moved from one point to another. 

Difference of Electric Potential. — 
(1) That quantitative property in space 
whereby work is done when an electric 
charge is moved therein. (2) The electric 
work done on a unit charge in an excur- 
sion between two points. 

Difference of Magnetic Potential.— 
(1) That quantitative property in space 
whereby work is done when a magnetic 
pole moves therein. (2) The magnetic 



work done on a unit magnetic pole in an 
excursion between two points. 

Difference of Tension.— A term some- 
times incorrectly employed for difference 
of potential. 

Difference of Thermal Pressure.— A 
phrase sometimes employed for the dif- 
ference of temperature between any two 
points in a conducting substance that 
is assumed to cause the flow of heat 
through that conductor from the higher 
to the lower temperature. 

Difference Theory of Muscle and 
Nerve Currents.— A theory proposed 
to explain the cause of the electric cur- 
rents in living tissues, by an alteration or 
change in the protoplasm, by injury, by 
differences of temperature, or by polari- 
zation. 

Differential Coils.— Coils that are differ- 
entially w T ound, or that act differentially. 

Differential Compound Motor. — (1) 

A compound motor in which the mag- 
neto-motive force of the working current 
is opposed to the magneto-motive force of 
the shunt excitation, for the purpose of 
maintaining the speed constant under all 
loads. (2) A com pound- wound contin- 
uous-current motor. 
Differential Electric Arc-Lamp.— A 
term formerly employed for a derived- 
circuit arc-lamp, in which the lifting 
magnet either consists of a core or sole- 
noid wound with series and shunt coils, 
or of two separate and opposed cores, one 
of which contains the series and the other 
the shunt winding. 

Differential Electric Bell.— An electric 
bell whose magnetizing coils are differ- 
entially wound. 

Differential Electro-Dynamometer.— 

(1) A double dynamometer with two mov- 
ing coils rigidly connected and oppositely 
acted on, so that the movement of the sus- 
pension system can be reduced to zero by 
electrical adjustments made wiiile the in- 
strument is under operation. (2) A dyna- 
mometer for measuring the difference 
between two electro-dynamic forces. 
Differential Electro-Magnet.— A differ- 
entially-wound electro-magnet. 

Differential Equation.— An equation 
connecting quantities into which one or 
more differential coefficients or differ- 
entials enter. 

Differential Galvanometer. — A gal- 
vanometer containing two coils, so wound 
as to tend to deflect its needle in opposite 
directions. 



Dif.] 



742 



[ML 



Differential Induction Coil.— (1) An in- 
duction coil employed in duplex and quad- 
ruplex telegraphy, having two differ- 
entially-wound primary coils, one of 
which is placed in the main line of the 
circuit, and the other in the circuit of an 
artificial line. (2) In telephony, an induc- 
tion coil which sometimes forms part of 
the equipment of a multiple switchboard 
operator. 

Differential Induetometer.— A galvano- 
metric apparatus for measuring the mo- 
mentary currents produced by the dis- 
charge of a cable. 

Differential Magnetometer.— A mag- 
netometer having a divided magnetic cir- 
cuit and a needle differentially acted upon 
by the branches. 

Differential Method of Duplex Teleg- 
raphy. — A system of duplex telegraphy 
in which the coils of the receiving and 
transmitting instruments are differenti- 
ally wound. 

Differential Method of Quadruplex 
Telegraphy. — A system of quadruplex 
telegraphy by means of a double-differ- 
ential duplex system. 

Differential Permeability.— The differ- 
ential coefficient of flux density to mag- 
netizing force in a substance undergoing 
magnetization. 

Differential Relay. — A telegraphic relay 
containing two differentially wound coils 
of wire on its magnet core. 

Differential Speed. — In an induction 
machine, the angular velocity of the field 
relatively to the rotor. 

Differential Susceptibility .—The differ- 
ential coefficient of the magnetic intensity 
to the magnetizing force in a substance 
undergoing magnetization. 

Differential Thermo-Pile.— A thermo- 
pile whose two opposite faces are exposed 
to the action of two nearly equal sources 
of heat, in order to determine accurately 
the difference in the thermal intensities 
of such sources of heat. 

Differential Voltmeter. — A voltmeter 
consisting of two separate decomposition 
cells, one placed in a, circuit of known 
resistance, and the other in a circuit 
whose resistance is to be determined. 

Differential Winding.— Such a double 
winding of magnet coils that the two 
poles produced thereby are opposed to 
each other. 

Differential Winding of Field.— (1) 
A field-magnet winding in which two ex- 
citing currents exert opposing magneto- 
motive forces. (2) A form of winding 



in which the magnetizing flux of the 
series coil is opposed by the magnetizing 
flux of the shunt coils. 

Differentially- Wound Dynamo-Elec- 
tric Machine.— A compound- w ound 
dynamo-electric machine. 

Differentially- Wound Motor.— A com- 
pound-wound motor, in which the current 
in the shunt coils opposes, in its magnet- 
izing effects, the current in the series coil, 
so that the efficient magnetizing effect 
produced is the difference between the 
magnetizing effects of the two coils. 

Differentially Wound Translator.— 
In telephony, a translator having one 
primary and two equal secondary coils, 
employed in duplex working. 

Diffraction Grating. — A plate containing 
a series of parallel linear openings, slits or 
scratches, separated by opaque or smooth 
spaces, employed for producing spectra 
by diffraction or interference. 

Diffusing Globes for Electric Lights. 
Globes so constructed as to ensure a dif- 
fusion of the light around which they are 
placed. 

Diffusion Creep. — A term sometimes used 
for the diffusion of an electric current. 

Diffusion of Electric Current.— The 
flow of an electric current in the portions 
of a conducting substance that lie outside 
the parts in the direct line between the 
points where the terminals of an electric 
source are applied, so that a difference 
exists in the density of the current at dif- 
ferent points of such substance. 

Diffusion of Electric Waves.— (1) The 
scattering of electric waves, or their 
deviation from a parallel beam. (2) The 
transmission of electric waves through a 
medium. 

Diffusion of Electro-Therapeutic Cur- 
rent. — The differences in the density of 
current in different portions of the human 
body, lying between electro-therapeutic 
electrodes. 

Diffusion of Lines of Force.— The diffu- 
sion of magnetic flux. 

Diffusion of Magnetic Flux.— The 
lateral deflection of magnetic flux from / 
the direct path between the poles that 
produce it. 

Digging Spoon. — A spoon-shaped shovel 
used in digging holes for telegraph poles. 

Dilation, Electric— Electric expansion, 
or an increase in volume, produced in a. 
body by an electric charge. 

Dilatometer. — An instrument resembling 
a thermometer, employed in measuring 
the expansion of a liquid by heat. 



Dim.] 



743 



[Dip. 



Dimensions of Electro-Magnetic 

Units. — The conventional exponential 
values of electro-magnetic units in terms 
of the fundamental units of length, mass, 
and time. 

Dimensions of Electrostatic Units. — 
The exponential values given convention- 
ally to the units of the electrostatic 
system, in terms of the fundamental 
units of length, mass, and time. 

Dimensions of Magnetic Units.— The 
exponential values given conventionally 
to the units of the magnetic system, in 
terms of length, mass, and time. 

Dimensions of Units. — The exponential 
values given conventionally to units in 
terms of length, mass, and time. 

Diminished Electric Irritability. — A 
decrease in the irritability of nervous or 
muscular tissue produced by a suitable 
electric current. 

Dimmer. — A choking coil employed in an 
alternating-current system of distribution 
for regulating the current strength pass- 
ing through incandescent lamps. 

Diode Working. — A term employed for 
the two-way mode of telegraphic working- 
established by the Delany Synchronous 
Multiplex Telegraphic System. 

Diopter. — A unit of the refracting or focal 
power of a lens. 

Dioptre. — An orthography commonly em- 
ployed for diopter. 

Dioptric. — An orthography sometimes 
employed for diopter. 

Dioptric. — Of or pertaining to dioptrics. 

Dioptric Shade.— A shade for a luminous 
source made of refractive material, which 
prevents the light from passing, in cer- 
tain directions, by reason of its refractive 
power. 

Dioptrics. — The science which treats of 
the refraction of light. 

Dioptry. — An orthography frequently em- 
ployed for diopter. 

Dip. — The inclination of a magnetic needle. 

Dip Circle. — A clipping needle provided 
with means for accurately measuring the 
angle of dip. 

Dip of Line-Wire or Conductor.— The 
sag, due to its weight, of an aerial con- 
ductor between any two of its adjacent 
supports. 

Diphase - Alternating Currents.— (1) 
Two separate alternating electric currents 
whose phase difference is a quarter of a 
cycle. (2) Two-phase currents. (3) 
Quarter-phase currents. 



Diphase- Alternating E. M. F's.— (1) Two 
separate alternating-electromotive forces 
whose phase difference is a quarter of a 
cycle. (2) Two-phase E. M. F.'s. (3) Quar- 
ter-phase E. M. F.'s. 

Diphase Alternator.— An alternator that 

produces diphase E. M. F.'s. 
Diphase Armature.— The armature of a 

diphase alternator, or diphaser. 

Diphase Armature-Winding.— Any ar- 
mature winding capable of furnishing 
diphase currents. 

Diphase Circuit. — A circuit, consisting 
either of three or four separate wires, em- 
ployed for the transmission of diphase 
currents. 

Diphase Field. — A diphase magnetic field. 

Diphase Generator.— (1) A generator 
capable of producing diphase E. M. F.'s. 
(2) A diphase alternator. 

Diphase Inter-Connected Circuit. — 
(1) A diphase circuit consisting of two 
outgoing conductors, one for each phase or 
side of the system, and a single return- 
conductor common to both. (2) A di- 
phase system in which the two diphase cir- 
cuits are not electrically separated or in- 
dependent. 

Diphase Magnetic-Field.— A magnetic 
field produced by diphase currents. 

Diphase Motor. — A motor suitable for use 
with diphase electric currents. 

Diphase Rotary-Field.— (1) A magnetic 
field produced by four or more magnet 
poles whose coils are so wound that their 
polarity not only alternates with changes 
in the direction of the current, but acts 
as though the field rotated. (2) A rotat- 
ing magnetic field produced by diphase 
currents. 

Diphase Transformer.— A polyphase 
transformer suitable for use with diphase 
currents. 

Diphase - Triphase Transformer. — A 

transformer for converting diphase into 

triphase currents. 
Diphaser. — A word sometimes used for 

diphase alternator. 
Diplex Circuit. — The circuit, including 

the line wire and apparatus, employed in 

any diplex system. 

Diplex Telegraph. — A general term em- 
bracing the apparatus employed in diplex 
telegraphy. 

Diplex Telegraphy. — Any method by 
which two telegraphic messages can be 
simultaneously sent in the same direction 
over a single wire. 



Dip.] 



744 



[Dir 



Diplex Telephony.— Any method by 
which two telephone messages can be 
simultaneously sent in the same direction 
over the same wire. 

Diplex Transmission. — The simulta- 
neous telegraphic or telephonic transmis- 
sion of two messages in the same direction 
over a single wire. 

Dipolar.— (1) Possessing two poles. (2) Bi- 
polar. 

Dipping. — (1) An electro-metallurgical 
process whereby a thin coating or depos- 
it of metal is obtained on the surface of 
another metal by dipping it in a solution 
of a readily decomposable metallic salt. 
(2) Cleansing surfaces for electro-plating, 
by immersing them in various acid 
liquors. 

Dipping Basket. — A perforated basket 
of non-corrosive material, employe'd in 
electro-plating, for the reception of 
articles that are to be cleansed by dip- 
ping. 

Dipping Hook. — A metallic hook em- 
ployed in electro-plating for holding ar- 
ticles that are to be cleansed by dipping. 

Dipping Magnetic-Needle.— (1) A mag- 
netic needle suspended so as to be free to 
move in a vertical plane only, and em- 
ployed to determine the angle of dip or 
magnetic inclination. (2) An inclination 
compass. 

Dipping Needle. — A term sometimes used 
for a dipping magnetic needle. 

Dipping Wire. — The wire employed in 
electro-metallurgy for suspending small 
articles that are to be cleansed by dip- 
ping. 

Dips. — Acid liquors employed in dipping. 

Direct-Coupled Dynamo.— A dynamo 
whose armature shaft is directly coupled 
to the driving shaft. 

Direct Coupling. — Coupling the shaft of 
a dynamo armature directly to the driv- 
ing or engine shaft. 

Direct-Current. — (1) A current whose di- 
rection is constant, as distinguished from 
an alternating current. (2) A continuous 
current. 

Direct-Current Dynamo-Electric Ma- 
chine. — Any dynamo-electric machine 
capable of furnishing direct currents. 

Direct-Current Electric Motor.— An 
electric motor driven by means of direct 
or continuous currents, as distinguished 
from a motor driven by alternating cur- 
rents. 

Direct-Current Rotary Transformer. — 
(1) A term sometimes employed for a ro- 



tating secondary generator of continuous 
currents. (2) A motor-dynamo or dyna- 
motor. 

Direct-Current Transformer.— (1) A 

transformer intended to vary the strength 
of continuous currents. (2) A direct-cur- 
rent secondary-generator. 

Direct-Driven Dynamo of Generator. 

A direct-coupled dynamo or generator. 
Direct-Deflection Method of Measur- 
ing Resistance.— A method of measur- 
ing resistance based on the deflection of 
a galvanometer in circuit with a resist- 
ance and a battery. 

Direct-Electromotive Force.— (1) An 
electromotive force acting on a circuit in 
the same direction as another electromo- 
tive force already existing in that circuit. 
(2) The electromotive force acting on any 
circuit in contra-distinction to the coun- 
ter-electromotive force set up in such cir- 
cuit. (3) A continuous-electromotive 
force as distinguished from an alternat- 
ing-electromotive force. 

Direct Excitation. — (1) The excitation of 
a muscle, resulting from the placing of an 
electrode directly on the muscle itself. 
(2) The excitation of a dynamo electric 
machine by a separate source of direct 
currents, as distinguished from its excita- 
tion by commuted currents taken from 
its own armature. 

Direct-Induced Current. — The break-in- 
duced current. 

Direct Inker. — An ink-writing Morse re- 
corder, wound for insertion in a tele- 
graphic line, as distinguished from one 
wound for a local circuit. 

Direct Lightning-Discharge. — The act- 
ual lightning discharge, as distinguished 
from the back or return-stroke or dis- 
charge. 

Direct-Reading Galvanometer.— A gal- 
vanometer in which the absolute value of 
the deflection and current strength are in- 
dicated directly, or without computation. 

Direct Sounder. — A telegraphic sounder 
wound for a line circuit and not for use in 
the local circuit of a relay. 

Direct-Reading Potentiometer.— A po- 
tentiometer which indicates directly on 
its scale the pressure measured at its ter- 
minals. 

Direct "Working of Telegraphic 
Sounder. — The working of a telegraphic 
sounder without the use of a telegraphic 
relay. 

Directed Streaming-Discharge.— A 
Tesla or high-frequency discharge which 



Dir.] 



'45 



[Dis, 



assumes the shape of a highly luminous 
cone. 

Directing Clock. — A controlling or mas- 
ter clock. 

Directing Magnet. — A controlling or com- 
pensating magnet. 

Direction of Electric Current.— A con- 
vention whereby an electric current is 
regarded as leaving a source at its positive 
pole, and re-entering it at its negative 
pole. 

Direction of Electrostatic Flux.— A 
convention whereby it is assumed that 
electrostatic flux leaves a positively 
charged body at its positive pole, and ter- 
minates on a negatively charged body. 

Direction of Lines of Force.— The direc- 
tion of magnetic or electrostatic flux. 

Direction of Magnetic Flux.— A con- 
vention whereby it is assumed that mag- 
netic flux issues from a magnet at its 
north-seeking pole, and returns to it at its 
south-seeking pole. 

Direction of Negative Rotation.— In 

the conventionally adopted system of 
kinetics, a clock-wise rotation about an 
axis as viewed from the front side of the 
clock. 
Direction of Positive Rotation.— In the 
conventionally adopted system of kinet- 
ics the counter-clockwise direction of 
rotation about an axis as viewed from 
the front face of the clock. 

Directive Tendency of Magnetic 
Needle. — The tendency of a magnetic 
needle to come to rest in the direction of 
the earth's magnetic flux. 

Disc Armature. — (1) The armature of a dy- 
namo-electric machine whose windings 
consist of flat coils supported on the sur- 
face of a disc. (2) An armature having 
the form of a disc. 

Disc Electrodes.— Disc-shaped carbon 
electrodes formerly employed in long- 
burning or all-night arc-lamps. 

Discharge.— (1) The equalization of the 
difference of potential between the ter- 
minals of a condenser or source, on their 
connection by a conductor. (2) The re- 
moval of a charge from a conductor by 
connecting the conductor to the earth or 
to another conductor. (8) The removal 
of a charge from an insulated conductor 
by means of a stream of electrified air 
particles. 

.Discharge. — To equalize differences of 
potential by connecting them by a con- 
ductor. 



Discharge Key. — A key employed to pass 
the discharge from a condenser or cable 
through a galvanometer. 

Discharge of Magnetism of Field 
Magnets. — A term sometimes employed 
for the unbuilding of a dynamo, or its 
gradual failure to produce current on the 
loss of magnetism of its field magnets. 

Discharging Rate. — The strength of the 
discharging current of a storage cell or 
battery. 

Discharge Resistance. — The resistance 
that is placed in the path or circuit of a 
discharge. 

Discharging Rod.— A jointed metallic 
rod, blunted at both ends, capable of 
adjustment as to the distance of the ends 
from each other, and provided with in- 
sulating handles, employed for the dis- 
ruptive discharge of Leyden batteries or 
condensers. 

Discharging Tongs. — A pair of discharg- 
ing rods with an insulating handle, con- 
nected together by a rivet like a pair of 
tongs, for effecting the disruptive dis- 
charge of a Leyden jar or condenser. 

Discoidal Ring- Armature. — A term 
sometimes used for disc armature. 

Discoidal Winding. — The flat-ring wind- 
ing employed in a disc armature. 

Disconnect. — (1) To break or open an elec- 
tric circuit. (2) To remove an electro- 
receptive device from a circuit. 

Disconnecting.— The act of opening or 
breaking a circuit, or of removing elec- 
tro-receptive devices therefrom . 

Disconnecting Plug.— An infinity plug. 

Disconnection. — (1) A general term des- 
ignating a variety of faults caused by the 
accidental breaking or disconnection of a 
circuit. (2) The intentional opening or 
breaking of a circuit, or the removal of an 
electro-receptive device therefrom. (3 ) A 
discontinuity in a circuit. 

Disconnector. — A key or other device for 
opening or breaking an electric circuit, or 
for removing an electro-receptive device 
therefrom. 

Discontinuity Plug. — A name sometimes 
employed for an infinity plug. 

Discriminating Lightning- Arrester. — 
The name sometimes applied to a non- 
arcing continuous-current lightning-ar- 
rester. 

Diselectriflcation.— A general term em- 
ployed for the act of causing a charged 
body to lose its electric charge. 

Disguised Electricity. — Dissimulated or 
latent electricity. 



Dis.] 



746 



[Dis. 



Disintegration of Storage Battery- 
Plate. — The gradual loosening or separa- 
tion of the active material of a storage 
battery plate from the perforations of the 
grid. 

Disjunctor. — A device employed in a sys- 
tem for the distribution of electric en- 
ergy by means of continuous currents in 
connection with condensers, for periodi- 
cally reversing the constant current sent 
over the line. 

Dispersing Pad-Eleetrode.— A thera- 
peutic pad-electrode, suitable for use with 
strong currents, applied directly to the 
body, for diffusing the therapeutic current 
through a large tract thereof. 

Dispersion Photometer. — A photometer 
in which the light to be measured is de- 
creased in intensity by a known amount, 
so as to be more readily compared with a 
standard light of much smaller intensity. 

Displacement Current.— (1) Therate-of- 
change of electric displacement. (2) An 
electric current produced in a dielectric 
by electric displacement, as opposed to a 
conduction current. 

Displacement, Electric— A displace- 
ment of electricity in a uniform non- 
crystalline dielectric when electrostatic 
flux passes through it. 

Displacement Flux.— (1) The flux of elec- 
tric displacement. (2) The surface inte- 
gral of displacement effected through the 
surface. 

Displacement Lines. — The lines along 
which displacement flux moves. 

Displacement Waves. — Waves produced 
in the ether by means of electric displace- 
ments. 

Disruptive Discharge.— A sudden and 
more or less complete discharge that 
takes place across an intervening non- 
conductor or dielectric. 

Disruptive Electric-Conduction .—The 
conduction of electric energy which ac- 
companies a disruptive discharge. 

Disruptive Strength of Dielectric— 
The strain a dielectric is capable of bear- 
ing without suffering disruption, or with- 
out permitting a disruptive discharge to 
pass through it. 

Dissipation Function. — (1) A function 
expressing the rate at which heat is 
produced by the passage of an electric 
current through a conductor. (2) A 
function, which, when differentiated 
with respect to a velocity as the inde- 
pendent variable, gives the applied 
force required to overcome the dissipa- 
tive resistance to motion. 



Dissipation of Charge.— The gradual 
but final loss of charge by leakage which 
occurs even in a well insulated conductor. 

Dissipation of Energy.— The expendi- 
ture or loss of available energy. 

Dissipativity. — The time-rate of dissipat- 
ing energy as heat per-unit-volume of a 
substance. 

Dissimulated Electricity.— (1) A term 
sometimes applied to the condition of an 
electric charge when placed near an op- 
posite charge, as in a Ley den jar or con- 
denser. (2) A bound charge. 

Dissociate. — To separate a compound sub- 
stance into its constituent parts. 

Dissociation. — The separation of a com- 
pound substance into its constituents. 

Dissonance, Electric — (1) Electrical dis- 
agreement. (2) A term employed in con- 
tradistinction to electric consonance, to 
alternating electromotive forces, fluxes 
or currents, whose phases are in opposi- 
tion. 

Dissymmetrical Alternating-Electro- 
motive Forces. — Alternating-electro- 
motive forces, in which an alternating 
semi- wave, when reversed in sign, does 
not reduplicate the preceding or suc- 
ceeding semi-wave. 

Dissymmetrical Induction of Arma- 
ture. — Any induction produced in the 
armature of a dynamo that is unequal in 
amount, in opposite or symmetrically dis- 
posed portions of the armature. 

Dissymmetrical Magnetic Field.— A 
field whose flux is not symmetrically dis- 
tributed. 

Dissymmetry of Commutation.— A 
commutation in which the neutral line 
does not coincide with the diameter of 
commutation. 

Distant Battery. — A battery employed 
in any telegraphic system at the distant 
receiving end of the line. 

Distant Station. — A term applied by a 
telegraph operator to the distant end of 
the line, in order to distinguish it from 
his own, or the home end. 

Distillation, Electric. — The distillation 
of a liquid in which the effects of heat 
are aided by the electrification of the 
liquid. 

Distorsion. — The change in the shape 
or configuration of a medium, or an en- 
tity, produced by the action of a stress 
or disturbance. 

Distorsion of Magnetic Field.— A 
change in the direction or distribution of 
the magnetic flux in the field of a dynamo 



Bis.] 



747 



[Bis. 



armature, produced by the magnetomo- 
tive force of the armature current. 
Distorsional Elasticity. — Elasticity in a 
body, due to its distorsion or deformation. 

Distorsionless Cable.— A cable that 
forms part of a distorsionless circuit. 

Distorsionless Circuit. — (1) A telegraph- 
ic circuit in which leakage and con- 
ductor resistance are so balanced as to 
leave no tailings. (2) A telegraphic cir- 
cuit in which there is no distorsion of 
signals or electric waves. 

Distributed Capacity.— The capacity of 
a circuit considered as distributed over 
its entire length, so that the circuit may 
be considered as shunted by an infinite 
number of infinitely small condensers, 
placed infinitely near together, as distin- 
guished from localized capacity, in which 
the capacity is distributed in discrete 
aggregations. 

Distributed Inductance. — Inductance 
distributed throughout the entire length 
of a circuit or portion thereof, as distin- 
guished from inductance interposed in a 
circuit in bulk at some one or more points. 

Distributed Winding of Dynamo Elec- 
tric Armature. — A winding disposed 
regularly over the surface of the armature 
as distinguished from a pole winding, or a 
winding composed of a f ew localized coils. 

Distributing Board. — (1) A term some- 
times employed in a system of telephonic 
or telegraphic communication, to a cross- 
connecting board. (2) A board at which 
the wires or cables from a telephone 
switchboard terminate and at which con- 
nections are made with the circuit wires. 
(3) An insulating board provided with 
screw connecting-pieces for readily con- 
necting branch circuits to mains in a dis- 
tributing system, with or without fuse 
cut-outs. 

Distributing Box. — (1) A box containing 
means for readily changing the connec- 
tions of distribution circuits with their 
source of supply. (2) A device by means 
of which both arc and incandescent lights 
may be simultaneously employed on the 
same constant-current circuit. (3) A 
device for cutting into or out of an arc 
circuit, at will, a group of series incan- 
descent lamps. 

Distributing Box of Conduit.— A name 
sometimes given to a man-hole of a con- 
duit. 

Distributing Brushes of Motor.— The 
brushes which rest on the commutator of 
an electric motor and carry the driving- 
current to it. 



Distributing Mains.— The mains em- 
ployed in a feeder system of parallel dis- 
tribution. 

Distributing Point.— A point, usually at 
the junction of risers and mains, or mains 
and sub-mains, where all the fuses or 
safety catches, belonging to that part of 
the system, are collected. 

Distributing Station.— (1) A station from 
which electricity is distributed. (2) A 
central station. 

Distributing Switch.— A switch for clos- 
ing a plurality of distributing circuits at 
will upon the source of supply. 

Distributing Switchboard.— (1) A mul- 
tiple switchboard. (2) A device for dis- 
tributing electricity over any of a number 
of circuits. 

Distributing Box.— A box placed at a 
distributing point for holding all the fuses 
belonging to that portion of the distribut- 
ing system. 

Distributing Box for Arc-Light Cir- 
cuits. — A device by means of which both 
arc and incandescent lights may be sim- 
ultaneously employed on the same line 
from a constant-current dynamo-electric 
machine. 

Distributing Centre. — (1) In an electrical 
distribution system a centre or sub-centre 
of distribution. (2) A ramifying point. 

Distribution of Charge.— The diffusion 
or dispersion of an electric charge over 
the surfaces of electrified bodies. 

Distribution of Electricity. — The divi- 
sion and transmission of electric energy 
by means of various combinations of elec- 
tric sources, circuits and electro-receptive 
devices, so arranged that the electricity 
generated by the sources is carried or dis- 
tributed to more or less distant electro- 
receptive devices, by means of the various 
circuits connected therewith. 

Distribution of Electricity by Alter- 
nating Currents. — A system of electric 
distribution in which the lamps, motors 
or other receptive' devices, are operated 
by means of alternating currents that 
are sent over the line or lines, in many 
cases after they have been modified by 
apparatus called transformers. 

Distribution of Electricity by Alter- 
nating Currents by Means of Con- 
densers. — A system of alternating-cur- 
rent distribution in which condensers are 
employed to transform currents of high 
potential, received from an alternating- 
current dynamo, to currents of low poten- 
tial which are fed to the lamjDs or other 
electro-receptive devices. 



Dis.] 



748 



[Diy. 



Distribution of Electricity by Corn- 
mutating Transformers.— A system of 
electric distribution in which motor gen- 
erators are used, but neither their field- 
magnets nor armatures are revolved, a 
special commutator being employed to 
change the polarity of the magnetic cir- 
cuits. 

Distribution of Electricity by Con- 
stant-Currents. — Any system of elec- 
tric distribution employing direct cur- 
rents, as distinguished from one employ- 
ing alternating currents. 

Distribution of Electricity by Con- 
stant Potential-Circuits.— A system 
of electric distribution in which the re- 
ceptive devices are placed in multiple or 
multiple-series across constant-potential 
mains. 

Distribution of Electricity by Con- 
tinuous Currents by Means of Con- 
densers. — A system of distribution in 
which a continuous current is conducted 
to certain points in a line, where a dis- 
junctor is employed to reverse it period- 
ically, the reversed currents so obtained 
being directly used to charge condensers 
in the circuit of which induction coils 
are employed. 

Distribution of Electricity by Con- 
tinuous Currents by Means of 
Transformers. — A system for the trans- 
mission of electric energy by means of 
continuous or direct currents that are sent 
over the line to suitably located stations 
where motor-dynamos are used for trans- 
formers. 

Distribution of Electricity by Motor- 
Generators. — A system of electric 
distribution in which a continuous high- 
potential current, distributed over the 
main line, is employed at the point where 
its energy is to be utilized for driving a 
motor, which in turn drives a dynamo 
whose current is employed to energize 
the electro-receptive devices. 

Distribution of Power, Electric— Any 

system in which mechanical energy is 
first converted into electro-magnetic en- 
ergy and then distributed over a line wire 
or circuit to electric motors, which again 
change the electro-magnetic energy into 
mechanical energy. 

Distributor. — A word sometimes applied 
to the distributing mains in a parallel 
system of distribution. 

District Call-Box. — A box by means of 
which an electric signal is automatically 
sent over a telegraph line and received 
by an electromagnetic device at the other 
end of the line. 



Diurnal Currents. — Earth currents 
through telegraph circuits of normal 
strength and executing diurnal cycles. 

Diurnal Inequality of Earth's Mag- 
netism. — Diurnal variations in the value 
of the earth's magnetic variation or in- 
clination. 

Diurnal Load-Factor.— (1) The ratio be- 
tween the total number of units sent out 
from a station in twenty-four hours, to 
the amount which would have been sent 
out in the same time if the plant were 
working at its maximum load for the 
whole twenty-four hours. (2) The ratio of 
daily average to daily maximum load. 

Diurnal Variation.— An approximately 
regular variation of the magnetic needle 
which occurs at different hours of the 
day. 

Divalent. — (1) Possessing an atomicity or 
valency of two. (2) Bivalent. 

Divergence.— (1) The integral of outward- 
ly directed flux over the surface of an ele- 
ment of volume divided by that volume. 
(2) The opposite of convergence. 

Divergent Flux. — (1) Flux that diverges 
or diffuses as it proceeds. (2) Flux that 
decreases in intensity along its path. 

Divergent Vector Quantity.— A vector 
point function in space having diver- 
gence. 

Diverging-Lens Photometer.— A pho- 
tometer in which the intensity of the 
light to be measured is decreased by 
means of a diverging lens. 

Diverging Magnetic Flux.— Magnetic 
flux that decreases in intensity and di- 
verges or diffuses in direction along its 
path. 

Diversity Factor. — A term proposed for 
the ratio of the average supply of electric 
power to a consumer to the maximum 
power supplied. 

Diviance. — A term proposed for resistance 
to the flow of magnetic induction. 

Divided Circuit.— (1) A branched or bifur- 
cated circuit. (2) A term sometimes 
employed for multiple circuit. 

Divided Core. — A laminated core. 

Divided Magnetic Circuit.— A mag- 
netic circuit which bifurcates or divides. 

Divided Telephone-Switchboard.— A 
multiple telephone switchboard. 

Divided Touch.— A term used in place 
of magnetization by separate touch. 

Divided Trolley Line.— A term some- 
times used for a sectional trolley line. 

Dividing Engine. — (1) A mechanical de- 
vice for dividing a thermometric, galvanos- 



Div.] 



749 



[Dou. 



metric, or other scale, into equal parts. 
(2) A device for dividing a tube or a 
scale into equal parts of a length, consist- 
ing essentially of a horizontal screw by 
means of which a carriage carrying suit- 
able marking gear can be moved along a 
parallel prismatic guide. 

Division Operator. — A railway telegraph- 
operator in charge of a telegraph division 
or section of railway telegraph. 

Doctor for Plating. — A device employed 
in electro-plating for coating surfaces 
that are too extended to be immersed at 
once in the plating bath. 

Dolly. — A polishing brush employed in 
electro-plating, consisting of a number of 
calico rings suitably clamped together 
in a wooden holder for attachment to a 
lathe. 

Domestic Telephone-Switchboard. — 
(1)A telephone switchboard located in a 
house for readily connecting different 
rooms. (2) A local telephone switchboard 
for connecting apartments in a residence. 

Door-Bell Pull, Electric. — A circuit- 
closing device attached to a bell-pull and 
operated by the ordinary motion of the 
pull. 

Door-Contact Lamp. — A contact which 
lights a lamp and permits it to remain 
lighted only while the door operating its 
circuit remains in a certain position. 

Door-Opener, Electric. — An electro- 
magnetic device for opening a door from 
a distance. 

Door Push. — A contact closed or opened 
by the opening or shutting of a door to 
give a notice of the movement at a dis- 
tance, as in a burglar-alarm system. 

Door Trigger. — A device by means of 
which notice is given of the opening or 
closing of a door or window. 

Dot-and-Dash Code. — A term sometimes 
employed for the Morse telegraphic code. 

Dotting Contact. — An electric contact 
obtained by the approach of one contact 
point towards another. 

Double Alternation.— (1) A complete 
cycle or double vibration. (2) A com- 
plete to-and-fro movement. 

Double Armature Windings. — Two 
separate armature windings applied sym- 
metrically to a core, and whose ends are 
connected respectively to alternate com- 
mutator bars. 

Double-Balance Relay. — In a closed-cur- 
rent system of alarm telegraphy, a pair 
of relays connected in series, one of which 
will close a local circuit if the main line 
current appreciably weakens, and the 



other of which will close a local circuit 
if the main line current appreciably 
strengthens. 

Double-Bar Switch.— A switch or re- 
verser consisting of a pair of parallel 
metallic bars or strips which move to- 
gether upon independent centres so as to 
make contact simultaneously upon one or 
more pairs of contacts. 

Double-Block Duplex System.— A 
system of duplex telegraphy in which a 
condenser exists in both arms of the 
duplex bridge. 

Double-Break Knife-Switch.— (1) A 
knife switch which breaks a circuit at two 
points. (2) A knife switch provided with 
a contact for both poles. 

Double-Break Switch. — A term some- 
times used for double-pole switch. 

Double-Bracket Pole.— A pole employed 
in an overhead line for the support of a 
double bracket. 

Double-Bracket Trolley Suspension. 
In a double-track trolley road, a pole pro- 
vided with two brackets, one extending 
over each track, and provided for holding 
the two trolley wires. 

Double-Block Duplex System.— A du- 
plex system on the Wheatstone bridge 
system, employing a condenser in each 
arm of the bridge. 

Double-Break Switch.— (1) A double- 
pole switch. (2) A switch which breaks 
a circuit in two places, as distinguished 
from a switch which breaks a circuit at a 
single point only. 

Double-Bronze "Wire. — A conducting 
wire possessing great tensile strength, 
provided with an aluminium-bronze core, 
and a copper-brass envelope. 

Double-Carbon Arc-Lamp. — An arc- 
lamp which will burn all night without 
recarboning, containing two sets of car- 
bon electrodes so arranged that, when one 
set is practically consumed, the current is 
automatically switched to the other set. 

Double-Circuit Dynamo.— A dynamo- 
electric machine provided with two sepa- 
rate circuits. 

Double-Conductor Cable or Wire.— A 
cable or wire provided with two separate 
insulated conductors. 

Double-Cone Insulator. — An insulator 
in which the line wire passes through and 
is supported by means of a tube consist- 
ing of two inverted, truncated cones, 
joined at their vertices. 

Double-Connector.— A form of binding 
screw suitable for readily connecting two 
wires together. 



Dou.] 



750 



[Dou, 



Double-Contact Key.— A key suitable 
•either for making two separate succes- 
sive contacts, or for closing either of two 
circuits. 

Double-Contact Push.— A push provided 
with two contacts so arranged that the 
pressure of a push opens one contact and 
closes the other. 

Double-Contact Push Button.— A push- 
button provided with two contacts. 

Double-Cord Multiple-Switchboard.— 

A multiple telephone switchboard in 
which connections are made by plugs and 
cords having two twin wires, as opposed 
to a switchboard in which single cord 
plugs are used. 

Double - Cord Switchboard. — (1) A 
switchboard employing twin-wire or 
double-conductor connections. (2) A 
switchboard in which each connection is 
established through a pair of cords, as 
distinguished from a single-cord switch- 
board. 

Double-Cup Insulator.— (1) An insulator 
consisting of two funnel-shaped cups, 
placed in an inverted position on the sup- 
porting pin, and separated from each other 
by a free air-space except at the ends 
which are connected. (2) A double-petti- 
coat insulator. 

Double-Curb. — A device for increasing 
the speed of telegraphic signalling by 
ridding the line of its charge before the 
next signal is sent, by sending more than 
one reversal of current with or without 
grounding the line, as distinguished from 
a single-curb. 

Double-Curb Signalling.— Signalling by 
means of a double curb. 

Double-Current Signalling.— (1) Signal- 
ling by means of currents that alternately 
change their direction. (2) Signalling in 
which the marking currents have one 
direction and the spacing currents the 
opposite direction. 

Double-Current Telegraphic - Work- 
ing. — Telegraphing or operating by means 
of double currents. 

Double-Current Translation.— (1) The 
automatic repetition of a telegraphic mes- 
sage by means of double currents. (2) 
Telegraphic translation employing double 
currents. 

Double-Current Translator.— A tele- 
graphic translator or repeater designed to 
operate on double-current transmission. 

Double-Current Transmitter. — A trans- 
mitting instrument employed in a system 
of telegraphy in which the direction of 
the line current is alternately changed, 



according to whether the key rests on its 
front or on its back stop. 
Double-Current Working.— A method 
of telegraphic working or transmission by 
means of double currents. 

Double-Curve Pull-Off.— A double-curve 
hanger. 

Double-Curve Trolley Hanger.— A 

hanger provided for holding an overhead 
trolley wire, supported by a lateral strain 
in opposite directions, and employed, gen- 
erally at the end of both single and double 
curves, and on intermediate points on 
double-track curves. 

Double-Curve Trolley-Suspension.— 

Suspension by means of a double-curve 
trolley hanger. 
Double-Deck Switchboard.— A switch- 
board arranged in two rows placed one 
above the other. 

Double-Dielectric Refraction.— Double 

electric refraction produced in a dielectric 
by the action of an electro-magnetic 
stress. 

Double-Duplex Block.— In submarine 
telegraphy, duplex transmission obtained 
by the aid of a condenser inserted in each 
arm of a Wheatstone's balance. 

Double-Filament Lamp.— (1) An incan- 
descent lamp, frequently employed for 
the side-light of a ship, and provided with 
two carbon filaments so arranged that 
should one break, the other will continue 
burning. (2) A twin-filament lamp. (3) 
An incandescent lamp having two fila- 
ments connected in series, and, therefore, 
requiring twice the electric pressure of an 
ordinary lamp. 

Double-Flexible Conductor.— A con- 
ductor consisting of two separate stranded 
flexible conductors, provided with an in- 
sulating covering common to both. 

Double-Fluid Electrical Hypothesis.— 

A hypothesis which endeavors to explain 
the causes of electrical phenomena by the 
assumption of the existence of two dif- 
ferent electric fluids. 
Double-Fluid Voltaic Cell.— (1) A vol- 
taic cell in which two separate fluids or 
electrolytes are employed. (2) A two-fluid 
voltaic cell. 

Double-Focus X-Ray Tube.— An X-ray 
tube, suitable for use with alternating 
electric currents, in wmich two anti- 
cathodes are employed, so arranged that 
they act as a common source of X-rays. 

Double-Hatchet Switch.— A term some- 
time? used for a double-knife switch. 



Dou.] 



751 



[Dou. 



Double-Horseshoe Field-Magnet.— A 

multiple field-magnet of a dynamo formed 
by two separate electro-magnets. 

Double Insulation. — Insulation of a con- 
ductor effected at two distinct points, so 
that if one insulation should fail the other 
will serve. 

Double-Key Tapper.— A key used in a 
system of needle telegraphy to send elec- 
tric impulses through the line in alter- 
nately opposite directions. 

Double-Liquid Voltaic Cell.— A double- 
fluid voltaic cell. 

Double-Loop. — (1) In telegraphy, any pair 
of associated loops. (2) A pair of loops 
connecting a pair of branch offices with a 
central office. 

Double-Loop Repeater.— In telegraphy, 
a pair of loops connecting a pair of branch 
offices with a central office, and so con- 
nected with a duplex set, or with the 
common side of a quadruplex set, in the 
main office, that one branch office can send 
messages on the duplexed line while the 
other office is receiving. 

Double-Magnet Dynamo-Electrie Ma- 
chine. — A term sometimes applied to a 
dynamo-electric machine, whose field 
magnets have two consequent poles. 

Double-Needle Telegraphy.— A system 
of needle telegraphy in which two sepa- 
rate and independently operated needles 
are employed on two separate circuits. 

Double-Peg. — A split peg which closes two 
separate contacts, when inserted in the 
switchboard to which it belongs. 

Double-Pen Telegraphic-Register.— A 
telegraphic register provided with two 
separate styluses or pens for recording 
the message on a paper fillet. 

Double-Petticoat Insulator. — (1) A 
double insulator, placed one within and 
beneath the other, to reduce the electric 
leakage over the surface. (2) A double- 
cup insulator. 

Double-Plug. — A double peg. 

Double-Plug Key.— A plug key made in 
two separate parts that are insulated from 
each other. 

Double-Pole Bell.— An electro-magnetic 
bell having a polarized armature which 
plays between a pair of electro-magnetic 
poles. 

Double Pole.— (1) A double telegraph 
pole. (2) Two telegraph poles placed 
side-by-side and braced together. (3) An 
H-pole. 

Double-Pole Cut-Out.— (1) A cut-out 
which provides in a single operation the 



cutting out of both the positive and the 
negative leads. (2) Two safety fuses, 
mounted on the same holder, and con- 
nected respectively to the positive and 
negative mains. 

Double-Pole Fusible Cut-Out. —A term 
sometimes used for double-pole cut-out. 

Double-Pole Safety-Fuse. — An auto- 
matic double-pole cut-out. 

Double-Pole Switch.— A switch which 
simultaneously breaks the circuit of both 
positive and negative leads. 

Double-Pole Telephone-Receiver.— A 
telephone receiver in which both poles of 
a small electro-magnet are presented to 
the diaphragm. 

Double Pull-Off.— (1) A pull-off employed 
on curves to hold a trolley wire in posi- 
tion when strain in both directions is nec- 
essary to hold it in place. (2) A double- 
curve pull-off. 

Double-Reduction. — A gear wheel veloc- 
ity reducer employing two gear wheels 
and two pinions, or oneintermediate shaft. 

Double-Reduction Car-Motor.— A car- 
motor provided with a double-reduction, 
or with one intermediate gear shaft be- 
tween the motor shaft and car wheel. 

Double-Reflection Tube. — A term some- 
times employed for a double-focus X-ray 
tube. 

Double-Refraction.— The property pos- 
sessed by certain transparent substances 
of splitting up a ray of light passed 
through them into two separate rays. 

Double-Refraction, Electric— The prop- 
erty of doubly refracting light acquired 
by some transparent substances when 
subjected to the stress of an electrostatic 
or electro-magnetic field. 

Double Ringing-Key .—In a multiple tel- 
ephone switchboard, a pair of keys form- 
ing part of an exchange operator's set, 
employed in ringing up. 

Double-Shackle Insulator.— A form of 
insulator employed in shackling a wire, 
consisting of two single-shackle insulators. 

Double-Shed Insulator. — A double-cup 
insulator. 

Double-Speaking Telegraph.— A term 
sometimes employed for the duplex tele- 
graph as employed on submarine cables. 

Double-Style Printing Apparatus.— A 
double Morse receiver employing two 
printing levers or styluses marking dots 
in parallel lines, one responding to posi- 
tive currents and representing dots, and 
the other responding to negative currents 
and representing dashes. 



Dou.] 



752 



[Dow 



Double-Successive Contact-Key. — A 

key so arranged as to successively close 
two separate circuits. 
Double Tapper Key.— A key employed 
in a system of needle telegraphy to send 
electric impulses over the line in alter- 
nately opposite directions. 

Double Telegraphic Transmission.— 

Any method of simultaneously sending 
two messages over a single line wire or 
conductor. 

Double Telegraphy.— A term sometimes 
employed for duplex telegraphic working. 

Double-Throw Switch.— (1) A switch 
capable of being thrown into either of 
two contacts or pairs of contacts. (2) A 
switch which has three positions. (3) A 
throw-over switch. 

Double-Touch. — Magnetization by double 
touch. 

Double-Transmission. — (1) The simul- 
taneous sending of two messages over a 
single wire in opposite directions. (2) Du- 
plex or contraplex telegraphy. 

Double-Transmitter for Engine Tele- 
graph. — A transmitter on board a twin- 
screw steamer for communicating orders 
electrically to the engine-room for both 
engines simultaneously. 

Double-Trolley.— Two separate trolleys 
placed on the same car, and moving over 
two separate trolley wires which form a 
metallic circuit, in any double-overhead 
system. 

Double-Trolley Line.— A metallic-circuit 
trolley line employing two trolleys, one 
connected with the positive conductor and 
the other with the negative conductor. 

Double-Trolley System for Electric 
Railroads. — An electric railroad system 
employing double trolley wires and double 
trolleys so as to provide a complete metal- 
lic circuit. 

Double-Truck Car. — A car supported on 
two separate single trucks, and employed 
with long cars for safety and ease in turn- 
ing around sharp curves. 

Double Vibration.— (1) A to-and-fro or 
complete vibration. (2) A complete cycle 
of vibratory motion. 

Double- Winding of Armature. — An 
armature winding provided with two 
separate windings or sets of coils, in which 
the separate windings are insulated from 
each other and connected to the com- 
mutator at alternate segments, so that the 
brushes rest coincidently upon segments 
that are connected with each winding, 
thus permitting each winding to furnish 
half the current strength with an attend- 



ant decrease in the inductance of each 
circuit. 

Double-Wire Circuit.— A metallic cir- 
cuit. 

Double- Wire Cleat.— A cleat for support- 
ing a pair of wires. 

Double-Wire Moulding.— A moulding 
for containing two wires, each in a sepa- 
rate groove. 

Double-Wire System for Electric- 
Light Leads. — On board ship, a system 
of electric-light wiring, in which going 
and returning conductors are provided, 
as distinguished from a single- wire system 
in which the hull of the vessel is em- 
ployed as a common return. 

Double-Wire Telephone-Switchboard. 

A switchboard in a central telephone ex- 
change, employing metallic circuits, in 
which each subscriber is connected by 
an independent double wire or metallic 
circuit. 
Double- Word.— In telegraphy, a word of 
more than the prescribed length and, 
therefore, counted and charged as two. 

Double -Wound Gramme Ring.— A 
gramme ring provided with two inde- 
pendent and symmetrically interspersed 
windings. 

Double-Wound Wire. — Wire provided 
with a double winding of cotton, silk, or 
other insulating thread. 

Doubler of Electricity . — An early form 
of continuous electrophorous. 

Doubly Re-Entrant Armature-Wind- 
ing. — (1) A winding in which the armature 
is provided with two separate windings 
or conducting paths, each of which is in- 
dependently re-entrant. (2) A double- 
wound armature, each winding of which 
is re-entrant. 

Doubly- Wound Resistance Coils.— A 

resistance coil wound, as is usual, with 
the wire doubled on itself, in order to 
minimize self-induction. 

Douche, Electric. — An electrified shower- 
bath. 

Down-Contact of Switch. — A contact 
which is made by the downward move- « 
ment of a switch. 

Down-Lines.-^In the United Kingdom of 
Great Britain and Ireland, telegraphic 
lines on the side remote from the prin- 
cipal station of the circuit, as distin- 
guished from up-lines. 

Down-Side. — In Great Britain, that side 
of a telegraphic circuit further from the 
metropolis or principal town of the cir- 
cuit, as distinguished from the up-side. 



Dra.] 



753 



[Dro, 



Drag. — In submarine cable operations, a 
haul made with a grapnel across a line of 
cable in the hope of hooking said cable. 

Drag of Magnetic Field.— A word some- 
times employed for the torque or electro- 
dynamic force produced by a magnetic 
field on an active conductor placed in it. 

Draw-Bar. — In a locomotive, the link 
or bar which connects it with its load. 

Draw-Bar Pull. — The pull delivered by a 
locomotive at its draw-bar, as distin- 
guished from the pull exerted by its motor. 

Drawbridge Frog. — A trolley frog for use 
at the point of overhead contact with a 
drawbridge wire. 

Draw Tongs. — A species of vise employed 
in connection with a light block-and- 
tackle for obtaining the required tension 
on an aerial line wire. 

Draw Vise. — (1) A device employed in 
stringing overhead wires. (2) A portable 
vise for holding and drawing up an over- 
head wire. 

Drawing-In-and-Out Conduit.— A con- 
duit provided with ducts, so as to readily 
permit the w T ires or conductors to be 
placed in the conduit or removed from 
after they have been placed therein . 

Drawing-In Box.— A flush box. 

Drifting of Needle.— (1) The failure of the 
needle of a galvanometer to remain at its 
zero point when no current is passing 
through its coils, due usually to variation 
in the condition of the magnetic needle, 
to variation in the torsion of the suspend- 
ing system, or to local or other causes. 
(2) Elastic fatigue in the suspension of a 
magnetic system. 

Drifting of Zero Point.— A term fre- 
quently employed for the shifting of the 
zero point. 

Drilling, Electric— (1) A term sometimes 
employed for the use of the voltaic arc 
in perforating a mass of metal or mineral. 
(2) Drilling by means of an electrically 
operated tool. 

Drip Loop. — A loop inclined upwards at 
the point where outside conductors enter 
a building, so that the rain-water flows 
along said loop from the building, instead 
of towards it. 

Driven Circuit of Transformer.— The 
secondary circuit of a transformer. 

Driven Coil of a Transformer.— The 
secondary coil of a transformer. 

Driven Pulley. — A pulley which receives 
its motion from a driving shaft. 

Driven Pulley of Dynamo.— The pulley 
connected with the armature shaft of a 
dynamo. 
48 



Driven Shaft.— The shaft worked by a 
belt from the driving pulley. 

Driving Circuit of Transformer.— The 
primary circuit of a transformer. 

Driving Coil of a Transformer. — The 
primary coil of a transformer. 

Driving Current of Motor. — The cur- 
rent which operates an electric motor. 

Driving E. M. F. — The impressed or 
working E. M. F. 

Driving Gear of Magneto.— The gear 
wheels connecting a magneto telephone- 
transmitter armature with the driving 
handle, whereby the speed of revolution 
of the armature is increased . 

Driving Horns. — In a smooth-cored ar- 
mature, mechanical projections for hold- 
ing the armature wires in place, and com- 
municating their electro-magnetic force 
to the armature. 

Driving Pressure. — The driving or im- 
pressed E. M. F. 

Driving Pulley. — That pulley of a ma- 
chine which is mounted on the driving 
shaft. 

Driving Pulley of Motor.— The pulley 
attached to the shaft of a motor, or the 
pulley through which a motor furnishes 
its mechanical power. 

Driving Shaft. — The shaft connected di- 
rectly with a prime mover. 

Driving Spider. — The radial arms or 
spokes connected to the armature of a dy- 
namo, and keyed to its shaft, so as to act 
as a driving wheel for the armature. 

Drop. — (1) A word frequently used for drop 
of potential, pressure, or electromotive 
force. (2) The fall of potential which 
takes place in an active conductor by 
reason of its resistance. 

Drop. — A shutter, or falling armature, of 
a drop annunciator. 

Drop Annunciator. — An electro-mag- 
netic annunciator, which, on being en- 
ergized, releases a shutter and allows the 
same to drop. 

Drop-Handle. — In single-needle teleg- 
raphy, a form of transmitter handle. 

Drop Indicator. — A drop annunciator. 

Drop of Magnetic Potential.— A fall of 
magnetic potential. 

Drop of Potential. — The fall of potential, 
equal in any part of a circuit to the pro- 
duct of the current strength and the re- 
sistance of that part of the circuit. 

Drop of Telephone Switchboard.— A 
small electro-magnetic annunciator in- 
serted in the line of each subscriber, 



Dro. 



754 



[Dup. 



whereby any current received from a sub- 
scriber attracts the armature of the elec- 
tro-magnet and releases the shutter, there- 
by indicating the number of the particu- 
lar subscriber calling. 

Drop of Voltage. — The drop or difference 
of poteptial of any part of a circuit. 

Drop Relay-Contact. — A form of relay- 
contact in which, on the passage of a cur- 
rent, the attraction of an armature releases 
a drop and thus completes a local circuit, 
which remains closed until the drop is 
reset. 

Drop-Shutter of Annunciator. — The 
drop of an electro-magnetic annunciator. 

Drop-Trolley. — A particular form of trol- 
ley wheel and pole which employs a 
swivel joint and springs forcing the trol- 
ley against the wire. 

Drop-Trolley Stand. — A support for a 
trolley pole or mast provided with a swivel 
joint and suitable springs for ensuring a 
firm pressure of the trolley wheel against 
the trolley wire. 

Drum. — A reel for holding wire or cable. 

Drum Armature. — A dynamo armature 
whose coils are wound longitudinally over 
the surface of a cylinder or drum. 

Drum Armature-Winding.— The wind- 
ing employed on a drum armature. 

Dry Battery. — (1) A number of separate 
dry voltaic cells, connected so as to act as 
a single source. (2) A dry pile. 

Dry Cable. — A dry-core cable. 

Dry Cell. — A dry voltaic cell. 

Dry-Core Cable. — A cable whose core is 
wrapped with paper or cotton which is 
not afterwards filled with paraffine, gutta- 
percha, or other insulating material, and, 
consequently, whose dielectric consists 
largely of dry air. 

Dry Distillation. — A species of destruc- 
tive distillation. 

Dry Electrode. — A therapeutic electrode 
applied in a dry state. 

Dry Front of Microscopic Objective. 

That front of a microscopic object glass 
which is turned towards the object, but 
is separated from it by a short distance or 
air gap, in contradistinction to an immer- 
sion lens. 

Dry Gelatine Cell. — A type of dry voltaic 
cell in which the fluid electrolyte is ab- 
sorbed by, or combined with, a suitable 
gelatinous substance. 

Dry Pile. — A dry battery. 

Dry Transformer. — An air-insulated 
transformer, as distinguished from an oil- 
insulated transformer. 



Dry Voltaic Cell.— (1) A misnomer for a 
voltaic cell in which the fluid electrolyte 
is held in suspension by saw-dust, gelatine, 
or other suitable material. (2) A sealed 
voltaic cell, which can, therefore, be in- 
verted without danger of spilling liquid. 

Dual Electrolysis.— A term sometimes 
employed to denote the double decom- 
position that attends the electrolysis of a 
metallic salt ; viz. that of the salt and its 
solvent. 

Dub's Laws. — A set of experimentally es- 
tablished laws relating to the tractive and 
attractive magnetic forces developed by 
electro-magnets under various conditions, 
of which the following are two : — " The 
attraction of V-shaped electro-magnets, 
with an equal number of windings, is pro- 
portional to the square of the magnetiz- 
ing current strength. " ' ' The attraction 
of V-magnets is, with equal currents, pro- 
portional to the square of the number of 
windings of the magnetizing spirals." 

Duct. — A space left in an underground 
conduit for a separate wire or cable. 

Duct of Conduit.— The space provided in 
a conduit for a conductor or cable. 

Dumb-Bell Vibrator.— An electric vi- 
brator consisting of two spheres con- 
nected by a straight conductor contain- 
ing an air-gap. 

Dummy Moulding. — A moulding not in- 
tended for the reception of a wire, but as 
part of an ornamentation, the moulding 
being symmetrically arranged on the ceil- 
ing with an electrolier as a centre, with 
only one or a few of the mouldings actu- 
ally having wires placed in them. 

Duopod. — A two-legged screw support for 
a pendant or upright. 

Duplex Balance. — The condition of a 
duplex telegraphic line, in which the 
home instruments are unaffected by the 
sending signals, and are, therefore, ready 
to respond to the received signals. 

Duplex Cable. — A cable containing two 
separate conductors placed parallel to 
each other. 

Duplex Circuit. — (1) A circuit arranged 
for duplex transmission. (2) A metallic 
circuit. 

Duplex Cut-Out. — A cut-out so arranged 
that when one bar or strip is fused or 
melted by an abnormal current, another 
can be immediately substituted for it. 

Duplex Electrolysis. — A term some- 
times used for dual electrolysis. 

Duplex Flat-Cable.— A flat laid-up cable 
containing two wires. 

Duplex Loop. — A loop or pair of wires 



Dup.] 



755 



[Dyn. 



leading to a branch office, whereby a 
branch office can be brought into con- 
nection with a duplex set placed at the 
main office, for the duplex sending and re- 
ception of messages at said branch office. 

Duplex Telegraph.— A general term 
embracing the apparatus employed in 
duplex telegraphy. 

Duplex Telegraphic Insulator. — A 
double telegraph insulator. 

Duplex Telegraphy. — A system of tel- 
egraphy whereby two messages can be 
simultaneously transmitted in opposite 
directions over a single wire. 

Duplex Telephony.— Duplex telephonic 
transmission. 

Duplex Transmission.— The sending of 
two telegraphic or telephonic messages 
simultaneously in opposite directions over 
the same wire. 

Duplex Wire. — An insulated conductor 
containing two separate parallel wires. 

Duplex Working.— Duplex transmis- 
sion. 

Duplexed-Diplex Telephony or Tel- 
egraphy. — Quadruplex telephony or tel- 
egraphy. 

Duplicate Arc. — A multiple arc contain- 
ing but two branches. 

Duration of Electric Discharge.— The 
time required to effect a complete dis- 
ruptive discharge. 

Dust Telephone - Transmitter.— (1) A 
form of microphone transmitter in which 
finely granulated carbon or carbon dust is 
contained within a suitably shaped box, 
connected with the terminals of the trans- 
mitter. (2) A granular telephone trans- 
mitter. 

Dyad. — (1) A chemical element which has 
two bonds by which it can unite or com- 
bine with other elements. (2) A biva- 
lent element. 

Dyad Atom. — An atom whose valency, 
atomicity , or combining power, is two. 

Dyeing, Electric— The application of 
electricity either to the reduction or to 
the oxidation of the salts used in dyeing. 

Dynamic Electricity. — A term some- 
times employed for current electricity, in 
contradistinction to static electricity. 
(Obsolete.) 

Dynamic Induction. — (1) A term some- 
times employed for mutual induction. 
(2) Kinetic induction. 

Dynamic Multiplier. — (1) A term some- 
times employed for a self-induction coil 
or a coil possessing self-induction. (2) A 
spark coil. 



Dynamic System of Induction Teleg- 
raphy. — A term sometimes used for the 
current system of induction telegraphy, 
as distinguished from an electrostatic 
system of induction telegraphy. 

Dynamics. — That branch of mechanics 
which treats of the action of a force in 
producing motions or pressures. 

Dynamo. — A dynamo-electric machine or 
generator. 

Dynamo Armature-Coils. — The coils 
employed on the armature of a dynamo- 
electric machine. 

Dynamo Balancing-Rheostat.— An ad- 
justable rheostat whose range is sufficient 
to balance the current of one dynamo 
against that of another, with which it is 
required to operate in parallel. 

Dynamo Battery.— The combination of 
several separate dynamos to act as a 
single electric source. 

Dynamo Brush-Holders. — Devices for 
supporting the collecting brushes of dy- 
namo-electric machines. 

Dynamo Brush-Trimmer. — A device for 
rapidly ensuring the accurate trimming 
of dynamo brushes. 

Dynamo Changing-S witch. — A switch 
designed to throw a dynamo from one 
circuit to another. 

Dynamo-Electric Generator. — A dy- 
namo-electric machine. 

Dynamo-Electric Machine.— (1) A ma- 
chine for the conversion of mechanical 
energy into electric energy, by means of 
electro-dynamic induction. (2) A dy- 
namo. 

Dynamo-Electric Machine Battery.— 
A dynamo battery. 

Dynamo or Motor Frame.— The iron 
body of a dynamo or motor, including the 
pole-pieces and standards, but excluding 
the base-plates and bearings. 

Dynamo or Motor Standards. — The sup- 
ports on which a dynamo or motor arma- 
ture rests. 

Dynamo Pole-Changer. — A pole-chang- 
ing transmitter employed in a system of 
duplex or quadruplex telegraphy. 

Dynamo Power. — The power of a motor 
to act as a generator. 

Dynamo Power of a Motor. — (1) A power 
possessed by an electric motor of produc- 
ing counter-electromotive force. (2) 
The number of volts of counter-electro- 
motive force produced by a motor per- 
revolution per-second. 



Dyn.] 



756 



LEar. 



Dynamo Regulator. — A name given to a 
form of rheostat employed in the regula- 
tion of a dynamo. 

Dynamo Resistance Box.— A form of 
rheostat employed in the regulation of 
a dynamo. 

Dynamo Terminals.— The main termi- 
nals of a dynamo. 

Dynamograph.— A term sometimes ap- 
plied to a typewriting telegraph that 
records the messages in typewritten char- 
acters, both at the receiving and trans- 
mitting ends of the line. 

Dynamograph, Electric— A device for 

electrically recording the work done by 

any machine. 
Dynamometer. — A general name given 

to a variety of apparatus for measuring 

power. 

Dynamometrie Governor. — A dyna- 
mometer employed on the shaft of an 



electric motor for the purpose of operat- 
ing a regulating apparatus. 

Dynamotor.— (1) A particular type of 
rotary transformer. (2) A motor-gener- 
ator, in which a generator and motor 
armature-winding are rotated through a 
common magnetic field. 

Dynamotor Windings.— Windings re- 
quired for the armatures of the dynamo 
and motor of a dynamotor. 

Dyne. —(1) The C. G. S. unit of force. 
(2) The force which in one second can 
impart a velocity of one centimetre-per- 
second to a mass of one gramme. 

Dyne-em. — An abbreviation proposed for 
a dyne-centimetre, the C. G. S. unit of 
work. 

Dyne: cm' 2 . — An abbreviation proposed 
for a dyne-per-square-centimetre, the C. 
G. S. unit of pressure. 

Dyne-Centimetre-Per-Second.— The C. 
G. S. unity of activity. 



E. or e. — A symbol for electromotive 
force. 

E. — A contraction sometimes used for 
earth. 

E. H. P. — A contraction for electrical 
horse-power. 

E. M. F. — A contraction for electromotive 
force. 

E. M. E. of Self-Induction.— The E. M- 
F. generated in a loop of wire during the 
filling or emptying of that loop by mag- 
netic flux from its own current. 

Ear. — (1) A metal piece supported by an 
insulator to which the trolley wire is 
fastened. (2) A trolley ear. 

Ear Piece. — A circular opening into an 
air chamber placed over the diaphragm 
of a telephone, suitably shaped to per- 
mit the ready application of the listener's 
ear. 

Earth. — (1) A fault in a telegraphic or other 
line caused by the accidental contact of 
the line with the ground or earth, or 
with some other ground-connected con- 
ductor. (2) That part of the earth or 
ground which forms a part of an electric 
circuit. 

Earth-Battery Current.— A current on 
a telegraph line caused by voltaic action 
between two dissimilar earth plates, as 
distinguished from a true earth current. 



Earth Cell. — A term frequently applied to 
a variety of voltaic cell, consisting of any 
voltaic couple buried in a comparatively 
moist stratum of earth. 

Earth Circuit. — A circuit in which the 
ground or earth forms part of the con- 
ducting path. 

Earth-Circuited Conductor. — A con- 
ductor connected to the ground or to an 
earth-connected circuit. 

Earth Coil for Magnetic Measurement. 
A coil capable of being moved about a 
fixed axis, or fixed axes, employed for 
generating a measurable E. M. F. from 
the earth's magnetic field. 

Earth Connection. — A conductor which 
establishes a connection between any 
apparatus or circuit and ground. 

Earth Currents. — Electric currents flow- 
ing through the earth, caused by the 
difference of potential of its different 
parts. 

Earth Currents of Cable.— Currents in 
a cable due to natural causes, such as 
climatic conditions or magnetic disturb- 
ances, as distinguished from the currents 
sent through the cable for the transmis- 
sion of messages. 

Earthenware Conduit. — A conduit, gen- 
erally multiduct, made of glazed earthen- 
ware. 



Ear.] 



757 



LEdi. 



Earth-Grounded Wire. — A wire one ter- 
minal of which is grounded or put to 
earth, so that the earth forms a part of 
the circuit in which it is placed. 

Earth Indicator. — An instrument suitable 
for the accurate determination of the 
magnetic inclination and the calibration 
of ballistic galvanometers. 

Earth Overlap Test. — A localization test 
for the position of a partial earth in a 
telegraph line, conducted alternately by 
observers at each end of the line, the line 
being grounded at one end while its re- 
sistance is measured at the other, and 
resistance is added to one end until the 
fault is brought to the centre of the cir- 
cuit. 

Earth Plates. — Plates of metal, buried in 
the earth or in water, connected to the 
terminals of earth wires. 

Earth Return. — That portion of a ground- 
ed circuit in which the earth forms its 
conducting path. 

Earth Strip. — In a multiple telephone 
switchboard a strip of metal, or top plate 
of a series of jacks, permanently connect- 
ed to earth through a battery, to furnish 
connections for the busy test. 

Earth-Switch for Telephone. — (1) In a 
single-cord multiple telephone-switch- 
board, a device for maintaining a ground- 
connection with the shank of a plug when 
out of use, by supporting the plug, friction 
tight, against a ground-connected bar. 
(2) A switch at a telephone switchboard 
for automatically grounding the sleeve of 
a plug when out of use. 

Earth Wires. — The wires that lead an 
earth-grounded circuit to the earth plates. 

Earth's Field.— The magnetic field pro- 
duced in any place by the earth's flux. 

Earth's Flux. — The magnetic flux pro- 
duced by the earth by virtue of its mag- 
netized condition. 

Earthed. — Connected to earth or ground. 

Earthing. — Connecting a line or conductor 
to earth or ground. 

Earthing Device.— An instrument for 
automatically making connection be- 
tween a system of wiring and the earth, 
should the potential between them rise be- 
yond a certain predetermined safe limit. 

Earthkin.— A terella. 

Easement. — A permit obtained from the 
owner of a property for the erection of 
poles or attachments for telephone, tele- 
graph, or other aerial lines. 

Ebonite.— (1) A hard, tough, black sub- 
stance, composed of India rubber and 



sulphur, possessing both high powers of in- 
sulation and high specific inductive capac- 
ity. (2) Vulcanite. 
Economic Coefficient.— The ratio be- 
tween the net electric power, or the out- 
put of a dynamo, and the gross electric 
power, or power actually converted in the 
dynamo. 

Economic Coefficient of Dynamo-Elec- 
tric Machine.— (1) The ratio between 
the electric power produced by a dyna- 
mo at its terminals, and the mechanical 
power expended in driving it. (2) A 
term sometimes employed for the ratio of 
the useful electric power at the termi- 
nals to the total electric power developed 
in the machine. 

Economy Coil.— A choking coil employed 
for the purpose of reducing the pressure 
on arc lamps fed by step-down trans- 
formers. 

Eddy Conduction-Currents.— (1) Eddy 
currents. (2) Foucault currents. 

Eddy-Current Loss. — The loss of energy 
in a dynamo, motor, transformer, or simi- 
lar apparatus, due to the presence of 
eddy currents. 

Eddy Currents.— Useless currents pro- 
duced in the pole-pieces, armature, and 
field-magnet cores of dynamos or motors, 
or in metallic masses generally, either by 
their motion through magnetic flux, oi 
by variations in the strength of electric 
currents flowing near them. 

Eddy Displacement-Currents. — Eddy 
currents produced in the mass of a di^ 
electric or insulator, by the passage 
through it of electrostatic or magnetic 
flux. 

Edgewise System. — A system of mount- 
ing central-station switchboard instru- 
ments, in which, for the purpose of econo- 
mizing space, their scales are presented 
edgeways vertically to the switchboard 
face. 

Edison Distributing-Box.— A distribut- 
ing box employed in the Edison three- 
wire system of distribution. 

Edison Effect. — An electric discharge 
which occurs between one of the termi- 
nals of the incandescent filament of an 
electric lamp and a metallic plate placed 
near but disconnected from the filament 
as soon as a certain difference of poten- 
tial is reached between the lamp terminals. 

Edison Electric-Tubes.— The under- 
ground tubes employed in the Edison 
three- wire system of distribution. 

Edison -Lalande Cell. — A zinc-copper 
couple in which the copper is covered 



Eel.] 



758 



[Eif. 



with a depolarizing layer of copper-oxide, 
and the couple immersed in an electrolyte 
of caustic soda or potash. 

Eel, Electric. — (1) An eel possessing the 
power of giving powerful electric shocks. 
(2) The gymnotus electricus. 

Effective Ampere-Turns.— (1) The re- 
sultant magnetizing force in a magnetic 
circuit. (2) The square root of the mean 
square of the ampere-turns in a periodi- 
cally-varying magnetizing force. 

Effective Conductance.— (1) The ratio in 
an alternating-current circuit of the real 
electric power,, or real activity, to the 
square of the effective pressure. (2) The 
virtual conductance of a circuit. (3) In 
an alternating-current circuit the ratio of 
the energy component of current to the 
total E. M. F. 

Effective Current-Strength.— (1) The 
strength of an alternating or sinusoidal- 
electric current, determined by its heat- 
ing effect ; or, in other words, the therm- 
ally effective current strength. (2) That 
value of the current strength of a sinusoi- 
dal or alternating current which is equal 
to the square root of the mean square 
of the instantaneous values of the current 
during one or more cycles. (3) The square 
root of the time average of the square of 
the current. 

Effective Electromotive Force.— (1) 
The difference between the direct and the 
counter-electromotive force. (2) The 
square root of the time average of the 
square of the E. M. F. (3) The virtual 
E. M. F. 

Effective M. M. F — The square root of 
the time average of the square of a peri- 
odically-alternating M. M. F. 

Effective Reactance.— (1) In an alternat- 
ing-current circuit, the ratio of the watt- 
less component of an electromotive force 
to the total current. (2) Apparent react- 
ance. 

Effective Resistance. — In an alternat- 
ing-current circuit, the ratio between the 
energy component of an electromotive 
force and the total current. 

Effective Secondary - Electromotive 
Force. — (1) The vector difference be- 
tween the direct and counter-electromo- 
tive force in the secondary of an induc- 
tion coil. (2) The E. M. F. in a secondary 
circuit expended in overcoming resist- 
ance. (3) The square root of the time aver- 
age of the square of a secondary E. M. F. 

Effective Starting-Current of Motor.— 
The indicated value of the starting cur- 
rent of a motor as observed on an am- 
meter. 



Effective Susceptance.— (1) In an alter- 
nating-current circuit, the ratio between 
the wattless component of a current and 
its total electromotive force. (2) Apparent 
susceptance. j 

Efficiency. — The ratio between an effects 
produced and the expenditure required 
to produce that effect. 

Efficiency of Voltaic Battery.— (1) The 
ratio between the actual ampere-hour out- 
put per gramme of zinc dissolved, and the 
theoretical ampere-hour output. (2) The 
ratio of the energy delivered at the ter- 
minals of a battery to the theoretically 
computed energy liberated within it elec- 
trochemically. (3) The ratio of the en- 
ergy at terminals to the total electric en- 
ergy. 

Effective Value of Periodic Current or 
E. M. F.— (1) The square root of the 
mean square of the current or E. M. F. 
extended over one or more complete cy- 
cles. (2) The virtual current or E. M. F. 

Efficiency, Electric— The useful or avail- 
able electric energy delivered by any 
source to its external circuit, divided by the 
total electrical energy within the source. 

Efficiency of Dynamo, Electric— The 
electrical output of a dynamo, divided by 
the total electric activity in its armature 
circuit. 

Efficiency of Conversion. — The ratio be- 
tween the energy present in any result 
and the energy expended in producing 
that result. 

Efficiency of Conversion of Dynamo. — 
The total electric energy developed by a 
dynamo, divided by the total mechanical 
energy required to drive the dynamo. 

Efficiency of Distribution.— The ratio 
of the units of electric quantity or elec- 
tric energy sold, or distributed to consum- 
ers from a central station, to the units 
generated in that station. 

Efficiency of Electric Lamp.— (1) The 
ratio of the luminous energy emitted by 
an incandescent lamp to the energy ab- 
sorbed by the lamp. (2) The ratio of the 

• number of candles which can be obtained 
from an electric lamp to the electric ac- 
tivity in the lamp expressed in watts. (3) 
A term in common but inaccurate use for 
the ratio of the number of watts con- 
sumed by a lamp to the number of can- 
dles it produces, expressed in watts per 
candle. 

Efficiency of Electric Motor.— (1) The 
ratio of the power delivered at a motor 
pulley to the electric power supplied at 
its terminals. (2) The ratio between the 
useful mechanical power delivered by a 



Eff.] 



759 



[Ele. 



motor and the electrical power put in to 
drive it. 

Efficiency of Radiation.— The ratio of 
the luminous activity of a luminous body 
to its radiation activity. 

Efficiency of Secondary Battery. — (1) 

The ratio of the electric quantity of dis- 
charge in ampere-hours to the electric 
quantity in a charge. (2) The ratio of the 
electric energy of discharge in watt-hours 
to the electric energy of charge. 

Efficiency of Transformer or Con- 
verter. — The ratio of the power supplied 
at the secondary terminals of a trans- 
former or converter to the power supplied 
at its primary terminals. 

Efflorescence. — (1) Pulverulence or crum- 
bling of crystalline salts, due to the loss 
of their water of crystallization on drying. 
(2) A term loosely applied to the deposi- 
tion of solid matter above the line of liquid 
on the surface of a vessel containing a va- 
porizing saline solution, by the crystalli- 
zation of the salt. 

Effluvia. — The name given to a variety of 
assumed highly tenuous imponderable 
forms of matter that were formerly be- 
lieved to be given off by electrified or 
magnetized bodies. 

Effluvium, Electric— A term employed 
in the early history of electricity for the 
supposed highly-tenuous, imponderable 
matter given off from an electrified body, 
which was assumed to be the cause of 
electric phenomena. 

Efflux. — The flow or quantity of liquid es- 
caping in a given time from an orifice in 
a containing vessel. 

Egg, Electric. — An egg-shaped vessel con- 
taining a partial vacuum through which 
an electric discharge is passed, for the 
purpose of producing luminous effects. 

Elastance. — (1) The reciprocal of the elec- 
trostatic capacity. (2) The reciprocal of 
permittance. 

Elastic. — (1) Of or pertaining to elasticity. 
(2) Possessing elasticity. 

Elasticity. — That property of a body in vir- 
tue of which its original configuration or 
form is regained, after a strain or distor- 
tion has been produced in it by the action 
of a stress. 

Elasticity, Electric— The quotient aris- 
ing from dividing the electric strain by 
the electric stress. 

Elastivity. — The reciprocal of permit- 
tivity. 



Elbow Connection. — A connection at an 
angle more or less approaching 90°. 

Elbow Connector.— A connector suitable 
for connecting conductors at an elbow. 

Electrepeter.— An old term for switch, 
key, or pole-changer. (Obsolete.) 

Electret.— (1) A name proposed for a sub- 
stance possessing natural or inherent elec- 
trization. (2) A permanently polarized 
body. 

Electric — Of or pertaining to electricity. 

Electrical. — An orthography for electric. 

Electrically. — In an electrical manner. 

Electrically Conducting.— Transferring 
electricity by electric conduction. 

Electrically Controlled Clock.— A clock 
that is controlled, either wholly or par- 
tially, by electricity. 

Electrically Discharging. —Equalizing 
differences of potential by connecting 
them with a conductor. 

Electrically Energizing.— Causing elec- 
tricity to produce any effect in an electro- 
receptive device. 

Electrically Illumined Buoy .—An elec- 
trically lighted buoy. 

Electrically Retarded.— Decreased speed 
of telegraphic signalling by means of 
electrostatic induction. 

Electrically Tuned System.— Any cir- 
cuit or system of circuits that have been 
brought into electric resonance with an- 
other circuit or system of circuits. 

Electrician. — One versed in the principles 
and applications of electricity. 

Electricity. — The name given to the un- 
known cause of electric phenomena. 

Electricity Driving-Force. — A term 
sometimes used for electromotive force. 

Electricity Meter.— (1) A coulomb meter. 

(2) A term sometimes used for electric 

meter. 
Electrics. — A term formerly applied to 

substances capable of becoming electrified 

by friction. (Obsolete.) 

Electrifiable. — Capable of being endowed 

with electric properties. 
Electrification. — The production of an 

electric charge. 

Electrified. — Endowed with an electric 
charge. 

Electrified Body.— A charged body. 

Electrify. — To endow with electric prop- 
erties. 

Electrine. — Of or pertaining to electrum 
or amber. 



Ele.] 



760 



[Ele. 



Electripherous. — An unnecessary word 
proposed for anything capable of bearing 
or transmitting electricity. 

Electrization. — Electrification. 

Electrize. — To electrify or endow with an 
electric charge. 

Electrizer. — Anything which electrifies or 
charges a body with electricity. 

Electro - Anaesthesia. — Insensibility to 
pain produced by the use of electricity. 

Electro -Ballistics. — The application of 
electricity to the determination of the 
velocity of projectiles. 

Electro-Bath. — The liquid or fluid em- 
ployed in electro-plating. 

Electro-Biological. — Pertaining to elec- 
tro-biology. 

Electro-Biologist. — One skilled in electro- 
biology. 

Electro-Biology. — That branch of electric 
science which treats of the condition of 
living animals and the effects of electric- 
ity upon them. 

Electro-Bioscopist. — One skilled in elec- 
tro-bioscopy. 

Electro-Bioscopy. — The determination of 
the existence of life or death by the pas- 
sage of electricity through the muscles 
and nerves. 

Electro-Brassing. — (1) The electrolytic 
deposition of brass from a solution con- 
taining salts of zinc and copper. (2) Coat- 
ing a surface with a layer of brass by 
electro-plating. 

Electro-Calorimetry.— The art of meas- 
uring the quantity of heat developed in 
any conductor or circuit by an electric 
current. 

Electro-Capillarity. — The science which 
treats of the mutual effects between elec- 
tricity and capillarity. 

Electro-Capillary. — Of or pertaining to 
electro-capillarity. 

Electro - Capillary Electrometer. — A 
capillary electrometer. 

Electro-Capillary Light.— A bright lighc 
obtained by the discharge of an induction 
coil through a narrow capillary tube pro- 
vided with aluminium or copper elec- 
trodes, and filled with air at ordinary 
pressures. 

Electro-Capillary Phenomena. — Elec- 
tric phenomena observed in capillary 
tubes at the contact surfaces of two 
liquids. 

Electro-Capillary Telephone.— A tele- 
phone transmitter whose operation de- 
pends on the electric currents produced 



by forcing a liquid through a bundle of 
capillary tubes, by the to-and-fro move- 
ments of the diaphragm. 
Electro-Chemical.— Of or pertaining to 
electro-chemistry. 

Electro-Chemical Accumulator.— A 

storage battery. 

Electro-Chemical Actinometer.— (1) An 
actinometer employing electrolytic ac- 
tion. (2) An electric actinometer. 

Electro-Chemical Decomposition. — 

Electrolytic decomposition. 

Electro-Chemical Filtration.— A term 
formerly employed in place of electric 
endosmose. 

Electro-Chemical Meter.— An electric 
meter in which the current passing is 
measured by the amount of electrolytic 
decomposition it effects. 

Electro-Chemical Telephone. — A name 
sometimes given to the Edison electro- 
motographic telephone. 

Electro-Chemical Series.— A list of 
chemical elements so arranged that each 
will displace from its compounds any 
element lower in the list than itself. 

Electro - Chemically. — In an electro- 
chemical manner. 

Electro - Chemist. — One skilled in the 
science of electro-chemistry. 

Electro-Chemistry.— (1) That branch of 
electric science which treats of electric 
combinations and decompositions effected 
by the electric current. (2) The science 
which treats of the relation between the 
laws of electricity and chemistry. 

Electro-Chromic Rings.— (1) A term 
sometimes applied to metallochromes. 
(2) Nobilli's rings. 

Electro-Chronographic— Of or pertain- 
ing to the electric chronograph . 

Electro-Chronometric Counter.— An 
apparatus employed in a system of elec- 
tric clocks to enable the master clock 
electrically to control or operate a num- 
ber of separate or secondary clocks. 

Electro - Coppering. — Electro - plating 
with copper. 

Electro-Crystallization.— Crystallization 
effected during electrolytic deposition. 

Electro-Culture of Plants.— Stimulating 
the growth of plants by electricity. 

Electro-Deposit. — A coating or electro- 
plating of metal. 

Electro-Depositer. — One who practises 
the art of electro-deposition. 

Electro - Deposition.— (1) The deposit, 
usually of a metallic substance, by means 



Ele/j 



761 



[Ele, 



of electrolysis. (2) Electrolytic deposi- 
tion. 

Electro-Deposits. — Electrolytic deposits. 

Electro-Diagnosis. — Diagnosis by means 
of the exaggeration or diminution of the 
reaction of the excitable tissues of the 
body when subjected to the varying in- 
fluences of electric currents. 

Electro-Diagnostic. — Of or pertaining to 
electro-diagnosis. 

Electro-Diapason. — An electro-magnet- 
ically operated tuning-fork. 

Electro-Dynamic Attraction.— The mu- 
tual attraction existing between electric 
currents, or between conductors through 
which electric currents are passing. 

Electro-Dynamic Balance. — A balance 
form of electro-dynamometer. 

Electro-Dynamic Capacity.— A term 
sometimes employed for self-induction. 

Electro-Dynamic Force.— A mechanical 
force exerted on the substance of a wire 
or conductor due to the dissymmetrical 
distribution of magnetic flux in its neigh- 
borhood. 

Electro-Dynamic Induction. — Electro- 
motive forces set up by induction in con- 
ductors which are either actually or prac- 
tically moved so as to cut magnetic flux. 

Electro-Dynamic Interrupter. — An in- 
terrupter for the primary circuit of an 
induction coil, consisting of an elastic 
wire stretched, like the w T ire of a sono- 
meter or monochord, between the poles 
of a permanent horse-shoe magnet. 

Electro-Dynamic Machinery .—Any ap- 
paratus designed for the production, 
transference, utilization, or measurement 
of energy by the medium of electricity. 

Electro-Dynamic Motor.— (1) A motor 
operated by electro-dynamic force. (2) 
An electric motor. 

Electro-Dynamic Potential.— An elec- 
tric potential produced by electro-dyna- 
mic induction. 

Electro-Dynamic Repulsion.— The mu- 
tual repulsion between two electric cir- 
cuits whose currents are flowing in op- 
posite directions. 

Electro-Dynamic Rotation.— (1) The ro- 
tation of a magnetic field produced as the 
resultant of two or more magnetic fields 
or magnetizing forces of variable inten- 
sity, acting at right angles to one another, 
whose maxima and minima do not coin- 
cide, but whose periods are the same. (2) 
Rotation produced electro-dynamically. 

Electro-Dynamic Screen. — A conduct- 
ing screen employed for intercepting the 



transmission of varying electro-magnetic 
forces. 

Electro-Dynamic Whirls.— Whirlings, 
or rotary motions produced in a cloud of 
copper oxide in a voltameter, when the 
electrolyte is traversed by a powerful 
discharge, while under the influence of 
magnetic flux. 

Electro-Dynamics. — That branch of elec- 
tric science which treats of the action of 
electric currents on one another, on 
themselves, or on magnets. 

Electro-Dynamical.— Of or pertaining to 
electro-dynamics. 

Electro-Dynamometer. — A form of gal- 
vanometer suitable for the measurement 
of electric currents. 

Electro - Dynamometer Balance. — A 
name sometimes given to a current bal- 
ance. 

Electro-Etching. — A term sometimes em- 
ployed for electric engraving. 

Electro-Extraction of Ores. — Various 
electric processes for extracting metals 
from their ores. 

Electro-Filtration.— A term sometimes 
employed for electric osmose or cata- 
phoresis. 

Electro-Genesis. — A word proposed for 
the production of electricity. (Not in 
use.) 

Eleetro-Genic. — Producing electricity. 
(Not in use.) 

Electro-Gild. — To cover with a metallic 
coating of gold by electro-plating. 

Electro-Gilder. — One who practises the 
art of electro-gilding. 

Electro-Gilding. — (1) Electric gilding. 
(2) Electro-plating with gold. 

Electro-Gilt. — Gilded by means of elec- 
tricity. 

Electro-Graphy.— Galvanography. 

Electro-Inductive Repulsion. — Repul- 
sion between bodies due either to the 
influence of electrostatically induced 
charges, or electromagnetically induced 
currents. 

Electro-Kinetic. — Of or pertaining to elec- 
tro-kinetics. 

Electro-Kinetic Energy. — Electrical 
energy that is actually engaged in doing 
work. 

Electro-Kinetic Units. — A term some- 
times used for C. G. S. electro-magnetic 
units. 

Electro-Kinetics. — A term sometimes ap- 
plied to the phenomena of electric cur- 
rents, or electricity in motion, as dis- 



Ele.] 



'62 



[Ele. 



tinguished from electrostatics, or the 
phenomena of electric charges, or elec- 
tricity at rest. 
Electro-Lithotrity . — A term proposed for 
the removal of urinary calculi by elec- 
trolysis. 

Electro-Magnet. — (1) A magnet produced 
by the passage of an electric current 
through a circuit of insulated wire. (2) A 
magnetizing coil surrounding a soft iron 
core, that is capable of being magnetized 
and demagnetized instantly on the clos- 
ing and opening of the circuit. 

Eleetro-Magnetie.— Of or pertaining to 
an electro-magnet or to electro-mag- 
netism. 

Electro-Magnetic Ammeter.— A form of 
ammeter in which a magnetic needle is 
moved against the field of an electro- 
magnet by the field of the current it is 
measuring. 

Electro-Magnetic Annunciator.— An 
electro-magnetic device for automatically 
indicating the points or places at which 
one or more electric contacts have been 
closed. 

Electro-Magnetic Attraction.— The mu- 
tual attraction existing between the un- 
like poles of electro-magnets. 

Electro-Magnetic Bell. — An electro- 
magnetically operated bell. 

Electro-Magnetic Bell-Call.— A bell-call 
operated by an electro-magnet. 

Electro-Magnetic Brake. — A brake for 
car wheels, whose braking power is 
either entirely derived from electro-mag- 
netism, or is thrown into action by elec- 
tro-magnetic devices. 

Electro-Magnetic Cam. — A form of mag- 
netic equalizer which depends for its 
operation on the lateral approach of a 
suitably shaped polar surface. 

Electro-Magnetic Capacity of Line.— 

A term sometimes used for the self-induc- 
tion or inductance of a line. 

Electro-Magnetic Cut-Out.— A cut-out 
operated by means of an electro-magnet. 

Electro-Magnetic Dental Mallet.— A 
mallet for filling teeth, the blows of which 
are struck by means of an electro-mag- 
netically driven mechanism. 

Electro-Magnetic Drill. — A drum em- 
ployed in blasting and mining operations, 
operated by means of electricity. 

Electro-Magnetic Drum.— A drum used 
in feats of legerdemain operated by 
means of an automatic electro-magnetic 
contact-breaker. 



Electro-Magnetic Engine.— An electric 
motor. 

Electro-Magnetic Explorer.— An appa- 
ratus operated by means of induced cur- 
rents, and formerly employed for the pur- 
pose of locating bullets, or other foreign 
metallic substances in the human body. 

Electro-Magnetic Eye.— (1) A term ap- 
plied to a certain form of spark micro- 
meter, employed by Hertz in his experi- 
ments on electro-magnetic radiation. 
(2) A term sometimes applied to a co- 
herer. 

Electro-Magnetic Field.— The field pro- 
duced either by an electro-magnet or by 
an electric current. 

Electro-Magnetic Flux.— Magnetic flux 
produced by means of an electro-magnet 
or by an electric current. 

Electro-Magnetic Gyroscope.— An elec- 
tro-magnetically driven gyroscope. 

Electro-Magnetic Helix. — An electro- 
magnetic solenoid. 

Electro-Magnetic Impulse.— An im- 
pulse produced in the ether surrounding a 
conductor by the action of an impulsive 
discharge, or by a pulsating field. 

Electro-Magnetic Induction.— A va- 
riety of electro-dynamic induction in 
which electric currents are produced by 
the motion either of electro-magnets, or 
electro-magnetic solenoids. 

Electro-Magnetic Inertia.— A term 
sometimes employed for the inductance 
or self-induction of a current. 

Electro-Magnetic Interference.— The 

interference of electro-magnetic waves. 
Electro-Magnetic Intermitter.— An 
electro-magnetic vibrator. 

Electro-Magnetic Medium.— Any me- 
dium in which electro-magnetic phe- 
nomena occur, or through which electro- 
magnetic waves are transmitted. 

Electro-Magnetic Meter. — An electric 
meter in which the current passing is 
measured by the electro-magnetic effects 
it produces. 

Electro-Magnetic Mine-Exploder.— A 

small magneto-electric machine employed 

in the direct firing of blasts. 
Electro-Magnetic Momentum.— T h e 

product of the inductance of a circuit and 

the current strength it carries. 
Electro-Magnetic Motor. — An electric 

motor. 
Electro-Magnetic Multiplier. — A term 

sometimes employed for Schweigger's 

multiplier. 



Ele.] 



763 



[Ele, 



Electro-Magnetic Optical-Strain.— Any 
optical strain produced by electro-mag- 
netic stress. 

Electro-Magnetic Pop-G-un.— A mag- 
netizing coil, provided with a tubular 
space for the insertion of a core much 
shorter than the length of the coil, which 
is violently projected when the coil is en- 
ergized by a current. 

Electro-Magnetic Radiation.— The radi- 
ation, from any conductor through which 
oscillatory discharges are passing, of 
electro-magnetic waves similar in all re- 
spects to those of light, save in their much 
greater wave length. 

Electro-Magnetic Repeater.— A word 
formerly employed for a form of vibrating 
contact-breaker. 

Electro-Magnetic Repulsion.— The mu- 
tual repulsion produced by two similar 
electro-magnetic poles. 

Electro-Magnetic Resonator. — A term 
sometimes applied to a Hertz spark micro- 
meter, in which electro-magnetic waves 
are produced by electric resonance. 

Electro-Magnetic Retardation.— A re- 
tardation in the magnetization or demag- 
netization of a substance. 

Electro-Magnetic Rotation.— Rotation 
obtained by electro-magnetic attractions 
and repulsions. 

Electro-Magnetic Separator.— (1) A de- 
vice for separating iron ore from the 
dross, in finely-pulverized, low-grade iron 
ores. (2) A device for magnetically re- 
moving particles of iron from brass filings 
or other non-magnetic material, and thus 
freeing such material from impurities. 

Electro-Magnetic Shunt.— (1) In a sys- 
tem of telegraphic communication, an 
electro-magnet whose coils are placed in 
a shunt circuit around the terminals of 
the receiving instrument. (2) Any shunt 
coil provided with a magnetic core. 

Electro-Magnetic Solenoid.— (1) A cy- 
lindrical coil of wire, each convolution of 
which is circular. (2) An electro-mag- 
netic helix. (3) A cylindrical current 

sheet. 

Electro-Magnetic Sorter.— An electro- 
magnetic separator. 

Electro-Magnetic Strain.— The effect 
produced by an electro-magnetic stress. 

Electro-Magnetic Stress.— The force or 
pressure in an electro-magnetic field 
which produces a strain or deformation in 
a piece of glass or other substance placed 
therein. 



Electro-Magnetic Telegraph.— A gen- 
eral term embracing the apparatus em- 
ployed in a system of electro-magnetic 
telegraphy. 

Electro-Magnetic Telegraphy.— (1) A 
system of telegraphy employing or based 
upon electro-magnetism. (2) The ordi- 
nary Morse telegraph}-. 

Electro-Magnetic Temperature-Regu- 
lator. — A temperature regulator whose 
operation is dependent on the action of 
an electro-magnet which is thrown into 
operation by the expansion or contraction 
of a solid liquid or gas. 

Electro-Magnetic Twist or Pull.— The 
torque of an electro-magnetic motor. 

Electro-Magnetic Units.— (1) A system 
of C. G. S. units employed in electro-mag- 
netic measurements. (2) Units based on 
the attractions and repulsions capable of 
being exerted between two unit magnetic 
poles at unit distance apart, or between 
a unit magnetic pole and a unit electric 
current. 

Electro-Magnetic Vibrator.— A name 
sometimes given to an automatic contact- 
breaker. 

Electro-Magnetic Waves.— Waves in the 
ether, given off from a circuit through 
which an oscillatory discharge is passing, 
or from a magnetic circuit undergoing 
variations of magnetic intensity. 

Electro-Magnetic Voltmeter.— A form 
of voltmeter in which the difference of po- 
tential is measured by the movements of a 
magnetic needle in the field of an electro- 
magnet. 

Electro-Magnetics. — That branch of elec- 
tric science which treats of the relations 
that exist between electric circuits and 
magnets. 

Electro - Magnetism. — Magnetism pro- 
duced bjr means of electric currents. 

Electro-Magnetist. — One skilled in the 
art of electro-magnetism. (Not in use.) 

Electro - Massage. — The application of 
electricity to the body during its mas- 
sage. 

Electro-Mechanical Alarm.— A mechan- 
ically operated alarm, that is started or 
set in operation by means of an electric 
current. 

Electro-Mechanical Bell. — A bell whose 
striking apparatus is mechanically oper- 
ated, when called into action by an electro- 
magnet. 

Electro - Mechanical Gong.— A gong 
struck or operated by mechanical force, 
at times which are dependent on the pas- 
sage of an electric current. 



Ele.] 



764 



[Ele, 



Electro-Mechanical Indicator.— A me- 
chanical indicator that is started or set 
into action by electricity. 

Electro-Medical. — Of or pertaining to 
electricity employed electro-therapeuti- 
cally. 

Electro-Medical Apparatus.— A general 
term for any apparatus employed in elec- 
tro-therapeutic treatment. 

Electro - Metallurgical Circuit. — An 
electric circuit employed in electro-metal- 
lurgical processes. 

Electro-Metallurgical Galvanization. 
A process of covering any conducting 
surface with a metallic coating by elec- 
trolytic deposition, such, for example, as 
the thin copper coating deposited on the 
carbon electrodes used in arc-lights. 

Electro-Metallurgical Deposit.— A me- 
tallic deposit thrown down on a conduct- 
ing surface by electrolysis. 

Electro-Metallurgical Dipping.— A pro- 
cess for obtaining an electro-metallurgi- 
cal deposit on a metallic surface by dip- 
ping it in a solution of a readily decom- 
posable metallic salt. 

Electro-Metallurgical Galvanization. 
The electro-therapeutic effects produced 
on nerves or muscles by the passage of an 
electric current. 

Electro-Metallurgy. — (1) That branch of 
electric science which relates to the elec- 
tric reduction or treatment of metals. (2) 
Electro-metallurgical processes effected 
by the agency of electricity. (3) Electro- 
plating or electro-typing. 

Electro-Motion. — Motion produced by 
electricity. 

Electro-Motor. — A term sometimes em- 
ployed for a voltaic couple. 

Electro-Muscular. — Of or pertaining to 
the influence of electricity on the mus- 
cles. 

Electro-Muscular Excitation. — In elec- 
tro-therapeutics, the galvanic or faradic 
excitation of a muscle, or its excitation 
by the continuous current from a voltaic 
battery, or by the alternating currents 
from an induction coil. 

Electro-Negative. — (1) In such a state as 
regards electricity as to be repelled by 
bodies negatively electrified, and attracted 
by those positively electrified. (2) The 
ions or radicals which appear at the anode 
or positive electrode of a decomposition 
cell. 

Electro-Negative Ions. — (1) The negative 
ions, or groups of atoms or radicals, which 
appear at the anode or positive terminal 
of a decomposition cell. (2) The anions. 



Electro-Negative Radicals.— The elec- 
tro-negative ions. 

Electro-Negatively.— In an electro-neg- 
ative manner. 

Electro-Negatives. — (1) The anions or 
electro-negative ions of a radical. (2) The 
atoms or radicals that appear at the anode, 
or positive terminal of any source, during 
electrolysis. 

Electro-Nervous Excitability. — The 
electro-therapeutic excitation of a nerve. 

Electro-Nickeling.— Electro-plating with 
nickel. 

Electro-Optics.— That branch of science 
which treats of the general relations ex- 
isting between light and electricity. 

Electro-Pathic. — Of or pertaining to elec- 
tro-pathology. 

Electro-Pathology .—Diagnosis by means 
of electricity. 

Electro-Percussion Drill.— (1) A drill 
employed for quarrying or mining in 
which a reciprocating motion for the drill 
is obtained by sending an electric current 
alternately through one or the other of a 
pair of solenoids of which the drill stock 
forms the core. (2) Any reciprocating 
drill operated electrically. 

Electro-Photometer. — An instrument for 
measuring the intensity of light by means 
of electricity. 

E 1 e c t r o-Photo-Micography .— Photo- 
graphy of the magnified images of micro- 
scopic objects illumined by the electric 
light. 

Electro-Physiological. — Of or pertain- 
ing to electro-physiology. 

Electro-Physiologist.— One skilled in 
electro-physiology. 

Electro-Physiology.— The study of elec- 
tric phenomena of living animals and 
plants. 

Electro-Plating. — The process of covering 
any conducting surface with a metal, by 
the aid of an electric current. 

Electro-Plating Bath. — A tank contain- 
ing a metallic solution in which articles 
are placed to be electro-plated. 

Electro-Pneumatic— Of or pertaining to 
the combined action of electricity and 
air pressure. 

Electro-Pneumatic Block System.— A 
block system for railroads in which the 
semaphores are operated pneumatically 
under the control of electro-magnetically 
operated valves. 

Electro-Pneumatic Signals.— Signals 
operated by diaphragms or pistons. 



Ele.] 



765 



[Ele. 



moved by compressed air, under electric 
control. 

Electro-Pneumatic Thermostat.— An 
instrument for automatically indicating 
the existence of a given temperature by 
the closing of an electric circuit, on the 
expansion or contraction of a gas. 

Electro-Polar. — Possessing electric poles. 

Electro-Positive.— (1) In such a state, as 
regards an electric charge, as to be at- 
tracted by a body negatively electrified, 
and repelled by a body positively electri- 
fied. (2) The ions or radicals which ap- 
pear at the cathode or negative electrode 
of a decomposition cell. 

Electro-Positive Ions.— The cathions or 
groups of atoms or radicals which appear 
at the cathode of a decomposition cell. 

Electro-Positively. — In an electro-posi- 
tive manner. 

Electro-Positives.— (1) The cathions or 
electro-positive ions of radicals. (2) The 
atoms or radicals that appear during elec- 
trolysis at the cathode, or negative elec- 
trode. 

Electro-Positive Radicals. — The electro- 
positive ions. 

Electro-Potential Energy. — Electric en- 
ergy possessing the power of doing work, 
but not actually doing work. 

Electro-Prognosis.— In electro-therapeu- 
tics a prognosis, or prediction of the fatal 
or non-fatal termination of a disease, from 
an electro-diagnosis based on the exagger- 
ated or diminished reactions of the ex- 
citable tissues of the body, when subjected 
to the varying influences of electric cur- 
rents. 

Elect ro-Puncturation. — Electro-punct- 
ure. 

Electro-Puncture.— The application of 
electrolysis to the treatment of aneurisms 
or diseased growths. 

Electro-Pyrometer.— An apparatus for 
the determination of temperature by the 
measurement of the electric resistance 
of a platinum wire exposed to the tem- 
perature which is to be measured. 

Electro-Receptive Devices. — (1) Vari- 
ous devices suitable for being placed in 
an electric circuit and energized by the 
passage of an electric current through 
them. (2) Translating devices. 

Electro-Reciprocating Drill.— An elec- 
tro-percussion drill. 

Electro-Refining. — Various processes for 
the electric refining of metals. 

Electro-Skiagraph. — A term proposed for 
a radiograph or X-ray picture. 



Electro-Semaphore.— A semaphore oper- 
ated by means of electricity. 

Electro-Sensibility. — An effect produced 
on a sensory nerve by its electrization. 

Electro-Siliceous Light.— An effect ob- 
tained by the discharge of a powerful 
rheostatic machine, through a glass tube 
traversed by a platinum wire, and plunged 
in salt water, the heat of the discharge 
not only melting and volatilizing the 
wire, but also raising the glass tube to 
brilliant incandescence. 

Electro-Silvering. — Covering a surface 
with an adherent coating of silver, by 
electro-plating. 

Electro-Smelting. — The separation or re- 
duction of metallic substances from their 
ores, by means of the heat developed by 
electric currents. 

Electro - Statics. — That branch of elec- 
tric science which treats of the phenomena 
and measurement of electric charges. 

Electro-Steeling.— (1) The art of covering 
copper electrodes with a thin coating of 
hardened iron. (2) Covering a printing 
surface of an electro with a thin deposit 
of copper, for the purpose of hardening it. 

Electro-Stereotype. — A word sometimes 
employed for electro-type. 

Electro-Stereotyping.— Electro-typing. 

Electro-Synthesis. — The chemical com- 
bination of electro-positive and electro- 
negative radicals under the influence of 
electricity. 

Electro-Technics. — The science which 
treats of the technical applications of elec- 
tricity and the general principles involved 
therein. 

E 1 e C tr O-Telegraphy. — Electric teleg- 
raphy. 

Electro-Therapeutic Bath. — A bath fur- 
nished with suitable electrodes for use in 
the therapeutic applications of electricity. 

Electro-Therapeutic Breeze.— An elec- 
tric breeze or convection current in air 
produced by the electrification of metallic 
points. 

Electro-Therapeutic Diffusion of Cur- 
rent. — The difference in the density of a 
current in different parts of the human 
body between electrodes applied thera- 
peutically. 

Electro-Therapeutic Dosage. — Propor- 
tioning the strength of an electro-thera- 
peutic current and the duration of its ap- 
plication to the body. 

Electro-Therapeutic Electrode. —The 
electrode mainly concerned in the electro- 



EleJ 



766 



[Ele. 



therapeutic treatment or diagnosis of 

diseased or disordered parts of the body. 

Electro - Therapeutic Electrodes. — 

Electrodes of various shapes employed in 
electro-therapeutics. 

Electro-Therapeutic Galvanization — 

In electro-therapeutics, the effects pro- 
duced on nervous or muscular tissue by 
the passage of a voltaic current. 

Electro - Therapeutic Head-Breeze. — 

A form of electric breeze or convective 
electric discharge applied to the head. 

Electro-Therapeutic Polarizing - Cur- 
rent. — The current which produces the 
phenomena of electro-tonus. 

Electro-Therapeutic Electrician. — An 

electro-therapist . 

Electro-Therapeutics.— (1) The applica- 
tion of electricity to the human body for 
the curing of disease or the improvement 
of health. (2) Electro-therapy. 

Electro-Therapeutist. — An electro-ther- 
apist. 

Electro-Therapist.— (1) One skilled in 
electro-therapy. (2) An electro-medical 
practitioner. 

Electro-Therapy. — A word sometimes 
used instead of electro-therapeutics. 

Electro-Thermal Meter. —An electric 
meter in which the current is measured 
by means of the heat generated by the 
passage of the current through a resist- 
ance. 

Electro-Thermancy . — That branch of 
electricity which treats of the effects 
produced by an electric current on the 
temperature of a thermo-electric junc- 
tion. 

Electro-Thermic. — Of or pertaining to 
the generation of heat by means of elec- 
tricity. 

Electro-Thermic Lightning- Arrester. 
A lightning arrester operated by the ex- 
pansion of a high-resistance shunt wire 
permanently connected to the circuit. 

Electro-Thermotic. — Of or pertaining to 
heat generated by electricity. 

Electro-Tinning. — Covering a substance 

with a coating of tin by electro-plating. 
Electro-Tint. — An etching obtained by 

electricity. 
Electro-Tinting. — A term proposed for a 

method of electric engraving. 
Electro-Type. — To produce a fac-simile 

by electrolytically depositing metals in 

a mould. 



Electro-Type. — A cast or impression of 
type obtained by means of electro-metal- 
lurgy. 

Electro-Type Process.— The process of 
electro-typing. 

Electro-Typic— Of or pertaining to elec- 
tro-typy. 

Electro-Typing. — Obtaining casts or 
copies of pages of type by depositing 
metals in moulds, by the agency of elec- 
tric currents. 

Electro-Typographic. — Pertaining to 
printing by means of electricity. 

Electro-Typy.— The art of producing 
electro-types. 

Electro- Vection.— A term sometimes 
employed for electric endosmose. 

Electro-Vital.— Pertaining to the rela- 
tions between electricity and vitality. 

Electrocesis. — A word proposed for curing 
disease by electricity. (Not used.) 

Electro Compound-Magnet.— A term 
formerly applied to an electro-magnet 
whose core was wound with two separate 
wires or conductors. (Obsolete. ) 

Electro Contact-Mine.— A submarine 
mine that is automatically fired on the 
completion of the current of a battery 
placed on shore, on the closing of floating 
contact points by passing vessels. 

Electrocution.— Capital punishment by 
means of electricity. 

Electrode.— (1) Either of the terminals of 
an electric source. (2) Either of the 
terminals of an electric source that are 
placed in a solution in which electrolysis 
is taking place. (3) Either of the electro- 
therapeutic terminals of an electric 
source. 

Electrodes. — The positive and negative 
terminals of an electric source, at their 
points of application to a receptive de- 
vice. 

Electrodeless Discharge.— The dis- 
charge obtained through the rarified gas 
of any vacuum tube that is unprovided 
with electrodes. 

Electrogen. — A name sometimes applied 
to the unknown cause of electricity. (Not 
in general use.) 

Electrograph. — (1) A curve produced by 
a recording electrometer. (2) A word 
sometimes used for radiograph. 

Electrographics. — (1) The science of geo- 
metrically solving electrical problems by 
graphical methods. (2) The science 
which treats of the graphical representa- 
tion of electric quantities. 



Ele.] 



'67 



[Ele. 



Electrolier. — A chandelier for holding 
electric lamps, as distinguished from a 
chandelier for holding gas burners. 

Electrolier Arm. — An electric fixture 
employed for attaching incandescent elec- 
tric lamps to gas fixtures or electroliers. 

Electrolier Cut-Out. — Any cut-out con- 
nected in the circuit of an electrolier. 

Electrolier Switch. — A switch conven- 
iently located for lighting or extin- 
guishing lamps in an electrolier. 

Electrization. — The act of being electri- 
fied, or electrifying. 

Electrologist. — An unnecessary word 
proposed for electrician. 

Electrologist. — One skilled in the science 
of electricity. (Not in general use.) 

Electrology. — That branch of science 
which treats of electricity. (Obsolete.) 

Electrolysis. —(1) Chemical decomposi- 
tion effected by means of an electric cur- 
rent. (2) The decomposition of the mol- 
ecule of an electrolyte into its ions or 
radicals. (3) Electrolytic decomposition. 

Electrolysis by Means of Alternating 
Currents. — Electrolytic decomposition 
effected, under certain circumstances, by 
alternating currents. 

Electrolysis of Salts.— The electrolytic 
decomposition of a salt into its constit- 
uent ions or radicals. 

Electrolyte. —(1) Any compound liquid 
which is separable into its constituent 
ions or radicals by the passage of elec- 
tricity through it. (2) The exciting 
liquid in a voltaic cell. 

Electrolytic. — Of or pertaining to elec- 
trolysis. 

Electrolytic Accumulator. — A word 
sometimes applied to a secondary or stor- 
age battery. 

Electrolytic Analysis.— A term some- 
times used for electric analysis. 

Electrolytic Annunciator. — An annun- 
ciator consisting of a number of separate 
electrolytic ceils, provided with a trans- 
parent cover, and so arranged that on the 
closing of the circuit of any particular 
cell by a distant push-button, a chemical 
decomposition is effected in the liquid 
of the electrolytic cell and a reddish- 
brown film formed over the surface of the 
electrode connected therewith. 

Electrolytic Assaying.— Assaying by 

means of electrolysis. ■ 
Electrolytic Bath.— An electrolytic cell. 
Electrolytic Cell.— (1) A cell or vessel 

containing an electrolyte in which elec- 



trolysis is carried on. (2) A plating cell 
or vat. 

Electrolytic Clock.— A timepiece in 
which the rotation of the clock-work is 
obtained by the rotation of a delicately 
pivoted and well balanced wheel by the 
difference in weight of its two halves im- 
mersed in an electrolytic bath, on the 
passage of an electrolyzing current. 

Electrolytic Condenser.— A condenser 
consisting of a number of iron plates im- 
mersed in a solution of carbonate of soda, 
and inserted in a branch circuit for the 
purpose of giving the current in that cir- 
cuit a lead, by increasing the capacity. 

Electrolytic Conduction.— A term some- 
times employed to indicate the passage of 
electricity through an electrolyte by 
means of charges imparted to its free 
ions or radicals. 

Electrolytic Conductivity.— The recip- 
rocal of the electrolytic resistance. 

Electrolytic Convection. — A term pro- 
posed for explaining the apparent con- 
duction of electricity by an electrolyte, 
without decomposition. 

Electrolytic Corrosion. — The corrosion 
by electrolytic action of water-pipes, gas- 
pipes, or other masses of metal, buried in 
moist earth. 

Electrolytic Coulomb-Meter.— A cou- 
lomb-meter whose operation depends on 
electrolytic decomposition. 

Electrolytic Diaphragm.— A diaphragm 
in an electro-plating bath. 

Electrolytic Decomposition. — The sep- 
aration of a molecule into its constituent 
ions or radicals by the action of an elec- 
tric current. 

Electrolytic Dissociation.— Electrolytic 
decomposition. 

Electrolytic Epilation. — The removal of 
hair by electrolysis. 

Electrolytic Etching.— (1) Etching by 
means of electrolytic corrosion. (2) A 
form of electric etching. 

Electrolytic Exchange.— Electrolysis. 

Electrolytic Generator.— A continuous- 
current dynamo-electric generator de- 
signed for supplying electricity for elec- 
trolytic purposes. 

Electrolytic Heating.— A method of elec- 
tric heating consisting in plunging the 
metal to be heated beneath the surface of 
a conducting liquid, while held in a metal 
clamp that is connected to the negative 
pole of a continuous-current source, while 
the positive pole of such source is con- 
nected to tlie metal lining of the vessel 
containing the conducting liquid. 



Ele.l 



[Ele. 



Electrolytic Hydrogen.— Electrolytical- 
ly liberated hydrogen. 

Electrolytic Meter .—An electro-chemical 
meter. 

Electrolytic Moulding.— A term some- 
times employed for electro-typing. 

Electrolytic Refining.— The refining of 
metals by electrolysis. 

Electrolytic Removal of Hair.— Elec- 
trolytic epilation. 

Electrolytic Separation. — Molecular dis- 
sociation produced by electrolysis. 

Electrolytic Synthesis.— Synthesis of a 
substance by electrolytic means. 

Electrolytic Writing. — Imprinting writ- 
ten characters on cloths or other textile 
fabrics by the electrolytic decomposition 
of a dyeing substance with which they 
are impregnated. 

Electroly tically . — In an electrolytic man- 
ner. 

Electrolyzability. — Possessing the power 
of being electrolyzed. 

Electrolyzable. — Capable of being elec- 
trolyzed or decomposed by means of elec- 
tricity. 

Electrolyzation. — The act of electroly- 
zing. 

Electroly ze. — To separate or decompose 
by means of electricity. 

Electrolyzed. — Separated or decomposed 
by means of electricity. 

Electrolyzer. — (1) One who, or that 
which, causes electrolysis. (2) An elec- 
troly zing apparatus. 

Electrolyzing. — Causing or producing 
electrolysis. 

Electrolyzing Cell.— An electrolytic cell. 

Electrolyzing Chamber.— A chamber or 
space in which electrolysis occurs. 

Electrometer. — An apparatus for measur- 
ing differences of electric potential. 

Electrometer Fatigue.— The failure of 
the needle of an electrometer to return to 
the zero point, due to the elastic fatigue 
of its suspension. 

Electrometer Gauge.— A device em- 
ployed in connection with some hetero- 
static electrometers, to ascertain whether 
the needle connected with the layer of 
acid, that acts as the inner coating of a 
Leyden-jar used in connection therewith, 
is at its normal potential. 

Electrometer- Voltmeter. — A voltmeter 
in which the differences of potential to 
be measured are employed to charge in- 
sulated conductors, the electrostatic at- 
tractions and repulsions of which result 



in the deflection of a suitably suspended 
metallic needle. 
Electrometric. — Of or pertaining to an 
electrometer. 

Electrometrical.— (1) Of or pertaining to J 
the measuring of electrical forces. (2) Of* 
or pertaining to an electrometer. 

Electromotive Arrangement or De- 
vice. — An electromotive source. 

Electromotive Force.— (1) The force 
which starts or tends to start electricity 
in motion. (2) The maximum or total 
generated difference of potential which 
exists in a circuit. 

Electromotive Force of Induction.— 

The electromotive force developed by any 
inductive action. 

Electromotive Impulse. — An impulse 
producing an impulsive rush of elec- 
tricity. 

Electromotive Intensity. — The vector 
electric force at a point, as measurable by 
the mechanical force that would be ex- 
erted upon a unit electric charge at that 
point. 

Electromotive Series.— A name some- 
times given to a contact series. 

Electromotive Source. — Any source such 
as a dynamo, or voltaic cell, capable of 
producing an electromotive force. 

Electromotograph. — An apparatus in 
which the friction of a platinum point 
against a rotating cylinder of chalk is re- 
duced by electrolytic action, consequent 
on the passage of an electric current. 

Electromotographic Telephone. — A 

loud-speaking telephone operating on the 
principle of the electromotograph. 

Electron. — (1) A word formerly used for 
amber. (2) The electric atoms whose pro- 
jection from the cathode of a high-vacu- 
um tube is supposed to constitute the 
cathode rays or streamings. (3) An alloy 
of gold and silver. 

Electronecrosic. — Pertaining to capital 
punishment by means of electricity. 

Electronecrosis. — A word proposed for 
capital punishment by means of electric- 
ity. (Not in use.) *■ 

Electronome. — A name proposed for a 
measurer of electricity. (Not in use.) 

Electropath. — One skilled in the art of 
electro-therapy. 

Electropathy. — A word sometimes em- 
ployed for electro-therapeutics. 

Electrophanic. — Pertaining to capital- 
punishment by means of electricity. 



Ele.] 



769 



[Ele. 



Electrophanical. — Pertaining to capital 
punishment by means of electricity. 

Electrophanize. — To inflict capital pun- 
ishment by means of electricity. 

Electrophany. — A word proposed for cap- 
ital punishment by means of electricity. 
(Not in use.) 

Electrophila.— A word proposed for capi- 
tal punishment by means of electricity. 
(Not in use.) 

Electrophobia. — A word proposed for un- 
necessary fear of electricity. 

Electrophone. — A word proposed for a 
carbon-contact telephone transmitter. 

Electrophor. — An orthography sometimes 
employed for electrophorous. 

Electrophoric. — Ol or pertaining to an 
electrophorous. 

Electrophoric Medium.— A word some- 
times employed for a dialectric medium. 

Electrophorous. — A simple form of elec- 
trostatic induction apparatus. 

Electropoion Liquid.— An exciting 
liquid, consisting of one part of bichro- 
mate of potash dissolved in ten parts of 
water, to which two and a half parts of 
sulphuric acid have been gradually added. 

Electroscope. — An apparatus for showing 
the presence of an electric charge, or de- 
termining its character, whether positive 
or negative, but not for measuring its 
amount or value. 

Electroscopic Gauge. — A term formerly 
applied to an early form of discharging 
gold-leaf electroscope. 

Electroscopically. — By means of an elec- 
troscope. 

Electroscopy.— The art of determining, 
by means of an electroscope, the character 
of an electric charge. 

Electrostatic— Of or pertaining to elec- 
trostatics. 

Electrostatic Attraction.— The mutual 
attraction existing between unlike elec- 
tric charges. 

Electrostatic Aurora. — Luminous phe- 
nomena attending the production of an 
electrostatic corona. 

Electrostatic Balance.— A form of bal- 
ance employed for the measurement of 
high, direct, or alternating electromotive 
forces, by the electrostatic effects pro- 
duced by their charges. 

Electrostatic Capacity.— The quantity 
of electricity which must be imparted to 
a given conductor as a charge, in order 
to raise its potential to unity, all neigh- 
boring conductors being at zero potential. 
49 



Electrostatic Capacity of a Line.— The 
power possessed by an electric line wire 
or conductor to act as a condenser. (2) The 
capacity of a line or conductor for holding 
an electric charge, as a condenser. 

Electrostatic Charge-Current of Cable. 
A momentary and violent rush of cur- 
rent that occurs on the application of an 
electromotive force to a submarine cable. 

Electrostatic Circuit. — A circuit formed 
bylines of electrostatic flux with an elec- 
tric source. 

Electrostatic Corona. — A luminous effect 
produced on the surface of a thin sheet 
of mica, or other insulating material, when 
placed between two electrodes, subjected 
to a comparatively high difference of po- 
tential. 

Electrostatic Current.— The time-rate- 
of-flow of electrostatic flux. 

Electrostatic Difference of Potential. 
The difference of potential due to elec- 
tric charges. 

Electrostatic Discharge.— A term some- 
times employed for a disruptive dis- 
charge. 

Electrostatic Field.— (1) The region of 
electrostatic influence surrounding a 
charged body. (2) A region traversed by 
electrostatic flux. 

Electrostatic Flux. — A stress in the 
ether which proceeds from a charged 
body along definite curved lines or paths. 

Electrostatic Flux-Paths.— The paths 
traversed by electrostatic flux. 

Electrostatic Force.— The force which 
produces the attractions or repulsions of 
charged bodies. 

Electrostatic Generator. — A general 
term applied to various forms of influence 
machines. 

Electrostatic Hysteresis.— (1) The en- 
ergy consumed in an alternating-electro- 
static field by the dielectric medium. (2) 
Dielectric hysteresis. 

Electrostatic Indicator. — A name some- 
times applied to an electrometer. 

Electrostatic Induction. — The induction 
of an electric charge produced in a con- 
ductor brought into an electrostatic field. 

Electrostatic Induction-Machine. — (1) 
A machine in which a small initial charge 
produces a greatly increased charge by 
its inductive action on a rapidly rotated 
disc of glass or other dielectric. (2) An 
electrostatic influence machine. 

Electrostatic Influence. — A term some- 
times used instead of electrostatic induc- 
tion. 



Ele.] 



770 



[Ele. 



Electrostatic Leakage. — The gradual dis- 
sipation of a charge due to insufficient in- 
sulation. 

Electrostatic Lines of Force. — (1) Lines 
of force produced in the neighborhood of 
a charged body, by the presence of the 
charge. (2) Lines extending in the direc- 
tion in which the force of electrostatic at- 
traction or repulsion acts. 

Electrostatic Motion.— Motion produced 
by an electrostatic field somewhat simi- 
lar to motion produced by a magnetic 
field. 

Electrostatic Motor.— (1) A motor driven 
by means of the induction of two varying 
electrostatic fields at right angles to each 
other. (2) Generally, a motor driven by 
the interaction of two or more electro- 
static fields. 

Electrostatic Optical Strain.— A strain 
or deformation produced in an optical 
medium by the stress of an electrostatic 
field. 

Electrostatic Potential.— (1) The power 
of doing electric work possessed by a unit 
quantity of positive electricity residing 
on the surface of an insulated body. (2) 
That property in space by virtue of which 
work is done when an electric charge is 
moved therein. 

Electrostatic Repulsion. —The mutual 
repulsion produced by two similar elec- 
trostatic charges. 

Electrostatic Resistance. — The resist- 
ance offered by any medium to the passage 
of an electrostatic flux or an electrostatic 
current. 

Electrostatic Retardation.— Retardation 
in signalling, on long telegraphic lines, 
due to electrostatic capacity. 

Electrostatic Screening. —Screening or 
shielding from the inductive effects of an 
electrostatic charge. 

Electrostatic Strain. — Strain produced 
by the stress of an electrostatic field. 

Electrostatic Stress.— The force or pres- 
sure in an electrostatic field which pro- 
duces electrostatic strain in any sub- 
stance placed therein. 

Electrostatic Time, Constant.— In an 
electric circuit or condenser, possessing 
capacity and resistance, the product of 
the capacity and the resistance, usually 
expressed in seconds or farad-ohms. 

Electrostatic Units. — Units based on the 
attractions or repulsions of two unit 
charges of electricity at unit distance 
apart. 

Electrothanasing.— Producing accidental 
death by means of electricity. 



Eleetrothanasis. — A word propose^ for 
accidental death produced by electricity. 
(Not in use.) 

Eleetrothanasise. — To produce accidental 
death by electricity. 

Electrothanatose. — A word proposed for 
capital punishment inflicted by means of 
electricity. (Not in use.) 

Eleetrothanatosic. — Of or pertaining to 
capital punishment by means of elec- 
tricity. 

Electrothanatosing. — A word proposed 
for execution by electricity. 

Electrotisis. — A word proposed for capital 
punishment by means of electricity. (Not 
in use.) 

Electrotome. — A term sometimes applied 
to an automatic contact-breaker which 
vibrates with sufficient rapidity to pro- 
duce a musical sound. 

Electrotonic— Of or pertaining to electro^ 
tonus. 

Electrotonic Currents.— In electro-ther- 
apeutics, a current due to the internal 
polarization of a nerve fibre between the 
conducting core of the nerve and its en- 
closing sheath. 

Electrotonic Effect.— An altered con- 
dition of excitability produced in a nerve 
when in the electrotonic state. 

Electrotonic Excitability.— The actual 
excitability of a nerve when in the elec- 
trotonic state. 

Eleetro-Tonicity. — A term sometimes 
employed for electrotonus. 

Electrotonus. — The condition of altered 
functional activity which occurs in a 
nerve when subjected to the action of an 
electric current. 

Electrozemia. — A word proposed for cap- 
ital punishment by means of electricity. 
(Not in use.) 

Electrum.— A name given by the ancients 
to various substances that could be readily 
electrified by friction. 

Element. — (1) Any kind of matter which 
cannot be decomposed into simpler mat- 
ter. (2) Matter that is formed or com- 
posed of but one kind of atoms. 

Element of Current. — A term employed 
in mathematical discussions to indicate 
a very small part of a current, for ease in 
considering its actions. 

Element of Storage Battery.— (1) A 
single set of positive and negative plates 
of a storage cell, so connected as to be 
ready for placing in the acid liquid of the 
containing jar or vessel. (2) A term some- 



Ele.] 



771 



[End, 



times applied to one of the storage cells 
of a battery. 

Element of Voltaic Cell.— Either of the 
substances forming the couple of a voltaic 
cell. 

Elements of Armature Winding.— The 
separated conductors forming the parts of 
an armature winding. 

Elementary Matter. — Matter which can- 
not be decomposed into simpler matter. 

Elevator Annunciator. — An annunciator 
connected with an elevator to indicate 
the floor from which a signal is sent. 

Elevator, Electric. — An elevator oper- 
ated by means of an electric motor. 

Elevator Switch. — A switch operated 
from an elevator for controlling the op- 
eration of the elevator motor. 

Elliptic al Rot ary-M agnetization . —The 
magnetization which exists in a diphase 
motor when two alternating-magnetic 
fluxes coexist while out of phase with 
each other. 

Elliptical Rotation. — A rotation as of a 
point on an ellipse. 

Elliptically Rotating Magnetic Field. 
(1) A magnetic field which is subject to 
elliptical rotation. (2) The rotation of 
magnetic flux produced by two diphase 
currents of unequal intensity, or of equal 
intensity, but not of 90° phase difference. 

Elongated Ring-Core.— A hollow cylin- 
drical core of comparatively great length. 

Elongation of Needle.— A phrase some- 
times used for the maximum angular 
deflection of a needle, or the maximum de- 
flection of the spot of light on a galva- 
nometer scale, when making one or more 
swings. 

Embedded Coils.— (1) Coils or windings 
placed in grooves or perforations on the 
armature of a dynamo or motor. (2) Iron- 
clad armature coils. 

Embossing Telegraphic Instrument. 
A registering telegraphic instrument in 
which the signal is recorded in embossed 
characters on a paper fillet. 

Emergency Brake.^-(i) A brake on a ve- 
hicle employed only in emergency. (2) In 
an electrically propelled vehicle a brake of 
greater power than the ordinary brake, 
and used only in emergency, as, for ex- 
ample, a reversing switch to reverse the 
direction of rotation of the motors. 

Emergency Cable.— A small, compara- 
tively inexpensive and easily handled 
cable, employed in the case of breaks in a 
pole line due to floods, railroad wrecks, 



etc., for opening up communication dur- 
ing repairs of the break. 
Emergency Crew. — A crew or gang in a 
power distribution system for service in 
case of a break-down, emergency, or fault 
on the line. 

Emergency Switch. — An accessory 
switch placed on a car controller for 
reversing the motion of a car when 
necessary. 

Electrotisic. — Pertaining to capital pun- 
ishment by means of electricity. 

Electrotising.— Inflicting capital punish- 
ment by means of electricity. 

Emissivity . — The specific radiating power 
of a surface, or its ability to emit or throw 
out radiant energy, usually expressed in 
ergs per sq. cm. 

Emissivity of Filament.— The ability of 
a filament to emit or radiate light and 
heat when traversed by an electric cur- 
rent. 

Emmetropic Eye.— The normal human 
eye, or the human eye in its normal adjust- 
ment and capability of accommodation. 

Empanelled Wires.— Wires placed inside 
mouldings, or behind panels. 

Emptied. — A term sometimes applied to a 
discharged secondary or storage battery, 
or to a discharged condenser. 

Enamelled Rheostat. — A rheostat whose 
coils consist of wires imbedded in a mass 
of enamel, in close juxtaposition to a mass 
of iron or other heat-conducting material. 

Enclosed Arc-Lamp.— An arc-lamp 
whose carbons are enclosed by a closely fit- 
ting globe, so as to maintain an atmosphere 
around the arc practically devoid of oxy- 
gon, thus diminishing the rate of con- 
sumption of the carbons. 

Enclosure of Magnetic Flux.— (^Link- 
age of magnetic flux. (2) Confining mag- 
netic flux in a ferric magnetic circuit. 

End Connections.— End windings. 

Endlessness. — The condition of a closed 
ring of uniform cross-section in which the 
magnetizing coils are wound uniformly 
all around it, and a practically endless or 
uniform magnetic field is obtained 
throughout the length of the ring. 

Endoscopic Lamp. — A lamp provided for 
the examination of a bodily cavity 
through its natural outlet. 

Endosmometer. — An apparatus for meas- 
uring the strength of endosmotic currents. 

Endosmose. — The unequal mixing of two 
different liquids or gases through the 
pores of an interposed medium. 



End.] 



772 



[Ent. 



Endosmose, Electric— (1) The unequal 
mixing of two liquids through the pores of 
an interposed septum on the passage of 
an electric current through the septum. 
(2) The transfer of liquid through an im- 
mersed septum traversed by an electric 
current. 

Endosmosis. — A word frequently employ- 
ed in place of endosmose. 

Endosmotic Equivalent. — The ratio be- 
tween the amount of water that passes 
through a porous membrane into a saline 
solution, and the amount of salt that 
passes in the opposite direction. 

Endothactic Cut-out. — A cut-out ar- 
ranged to throw a device into a circuit. 

Endothactic Switch. — A switch which is 
arranged to cut a device into a circuit. 

Endothermic. — Of or pertaining to the 
absorption of heat. 

Endothermic Reaction.— A chemical ac- 
tion attended with the absorption of heat. 

End-to-End Joint. — A term frequently 
employed in place of butt-joint. 

End Windings. — (1) End connections. 
(2) Conductors for connecting up bar 
windings at the end of an armature. 

Energetics. — That branch of mechanics 
which treats of the transfer of energy or 
of its transformation. 

Energy. — The power of doing work. 

Energy Component of Current.— (1) In 
an alternating-current circuit the com- 
ponent of current which is in phase with 
the impressed E. M. F. (2) In an alter- 
nating-current circuit, the product of the 
E. M. F. and the effective conductance. 

Energy Component of E. M. F.— (1) In 
an alternating-current circuit the com- 
ponent of E. M. F. which is in phase with 
the current. (2) In an alternating-cur- 
rent circuit, the product of the current 
and the effective resistance. 

Energy Current. — (1) A term sometimes 
used for active component of current in 
an alternating-current circuit, as dis- 
tinguished from the wattless component 
of current. (2) The product in an alter- 
nating-current circuit of the effective con- 
ductance and the E. M. F. 

Energy Efficiency of Storage Battery. 
The watt-hour efficiency. 

Energy, Electric. — The power which 
electricity possesses of doing work. 

Energy Electromotive Force.— (1) The 
energy component of E. M. F. in an alter- 
nating-current circuit. (2) The compon- 
ent of E. M. F. which is in phase with the 
current strength. 



Energy Flux.— (1) A stream of energy 
transfer. (2) A surface integral of energy 
transferred through a surface. 

Energy Meter.— A term sometimes ap- 
plied to a wattmeter. 

Energy of Motion.— A word sometimes 
used for kinetic energy. 

Energy of Position.— A word sometimes 
used for potential energy. 

Energy of Strain.— A term sometimes 
used for potential energy of deformation 
elasticity. 

Energy Resistance.— In an alternating- 
current circuit, the energy component of 
impedance. 

Energy Storage-Capacity . — The total 
amount of energy which a storage cell 
can store up expressed in watt-hours. 

Energy Transforming-Device. — Any 
device which will transform or change 
energy from one form to another. 

Engaged Test.— (1) In telephony, the busy 
test. (2) A test made by the operator at a 
central exchange to ascertain whether the 
subscriber desired is already engaged in 
telephonic communication. 

Engine. — In telephony, a name sometimes 
used for a ringer or magneto-generator. 

Engine Dynamo.— A direct-connected 
dynamo. 

Engine Plane Signal.— In a system of 
mine signalling a circuit containing a 
battery and bell at the engine house, and 
a pair of uncovered iron wires along the 
engine plane, or hoist run, for the purpose 
of giving signals to the man at the engine. 

Engine-Room Indicator. — An indicator 
placed in an engine-room. 

Engine-Room Tachometer.— A tacho- 
meter suitable for permanent attachment 
to an engine, dynamo, or other rotating 
machine situated in an engine-room. 

Engine Telegraph. — A telegraph on board 
ship for communicating orders to the 
engine-room. 

English Heat Unit.— (1) The British heat 
unit. (2) The heat necessary to raise a 
pound of water 1° F. 

Engraving, Electric— A method for elec- 
trically etching or engraving a metallic 
plate by covering it with wax, tracing 
the design on the wax so as to expose the 
metal, connecting the metal with the 
positive terminal of a battery, and placing 
it in a bath opposite another plate of metal, 
so that it will be electrically corroded on 
its exposed parts. 

Entering Current of Telegraphic Cir- 
cuit. — A term employed to designate the 



Ent.] 



773 



[Equ. 



current on a telegraphic line or conductor 
near the battery. 

Entrefer. — (1) The gap of non-magnetic 
material through which the field flux has 
to pass at the surface of the armature 
of a dynamo-electric machine, composed 
either of an air-gap or of air and copper. 
(2) The width of the non-magnetic gap, 
as distinguished from the width of the 
clearance or simple air-gap of a smooth 
cored armature. 

Entropy. — (1) In thermo-dynamics the 
non-available energy in any system. 
(Clausius and Mayer.) (2) In thermo- 
dynamics the available energy in any 
system. (Tait, Thomson, Maxwell.) 

Entropy, Electric. — A term proposed by 
Maxwell for use in thermo-electric phe- 
nomena, to include the doctrine of entropy 
in electric science. 

Environment. — The accompaniments or 
surroundings of any thing or condition. 

Eolotropic. — (1) Heterogeneous with re- 
spect to direction. (2) A medium in which 
equal stresses applied in different direction 
do not produce equal and similar strains. 

Eolotropic Dielectric— A dielectric pos- 
sessing eolotropic properties. 

Eolotropic Medium. — Any medium pos- 
sessing eolotropic properties. 

Eolotropic Wire-Grating. — An eolo- 
tropic screen employed by Hertz in his 
experiments on electric radiation. 

Eolotropism. — The possession of eolo- 
tropic properties. 

Eolotropy.-The doctrine, theory, or condi- 
tion of eolotropism. 

Epoch. — In the case of a vibrating body, 
the time or the angle reckoned from the 
point of starting to the point of maximum 
positive elongation. 

Equal Arms Electric Balance.— An 
electric Wheatstone bridge or balance em- 
ploying equal arms. 

Equal Deflection Method.— A method 
of measuring a resistance, electromotive 
force or current which consists in obtain- 
ing the same deflection on a galvanometer 
in the circuit with a given shunt. 

Equalizer. — (1) An equalizing bar. (2) A 
term employed for an equalizer wire. (3) 
A device for equalizing electric pressure 
over a system. 

Equalizer Feeder.— A feeder whose sole 
or principal purpose is to equalize the 
pressure between the ends of two or more 
other feeders, as distinguished from sup- 
plying current to feeding points. 



Equalizer Feeder-Switch. — A switch 
employed to throw a feeder equalizer in 
or out of circuit. 

Equalizer Switch. — A switch governing 
a resistance suitable for feeder regulation. 

Equalizer Wire.— (1) An equalizing bar. 
(2) A wire connecting the series windings 
of two or more compound- wound genera- 
tors operated in parallel. 

Equalizing Bar. — A bar joining the series 
coils of two parallel-connected, compound- 
wounds generators, so that any excess of 
current supplied by the armature of one 
machine must necessarily excite the 
other machine to the same extent. 

Equalizing Current. — The current pass- 
ing through an equalizing bar between 
two dynamos. 

Equalizing Dynamo. — A dynamo em- 
ployed in systems of three or five-wire 
distribution to supply one pair of mains 
which may be unduly loaded so as to 
equalize the pressure. 

Equalizing Resistance-Coils. — Resist- 
ance coils employed in a system of feeder 
regulation. 

Equalizing Wires.— (1) Two wires or con- 
ductors, one of which is employed for 
connecting the positive brushes and 
the other for connecting the negative 
brushes of compound-wound dynamos, 
when connected in parallel. (2) Wires 
connecting corresponding segments in a 
multipolar armature winding. 

Equator of Magnet.— (1) A point ap- 
proximately midsvay between the poles 
of a straight bar magnet, or nearly mid- 
way from the poles of a horse-shoe mag- 
net, if measured along the bar from each 
pole. (2) A line of neutral points on a 
magnet. 

Equatorial. — Of or pertaining to the 

equator. 
Equatorial Region of Magnet.— The 

portions of a magnet which lie near the 

magnetic equator. 
Equatorially. — In the direction of the 

equator. 

Equiangular Impedances. — Imped- 
ances which have the same angle. 

Equilibrium. — The condition of a body 
on which several forces are acting, so that 
their resultant is zero. 

Equilibrium of Radiation.— The condi- 
tion of a radiating body in which the 
radiant energy it absorbs is equal to that 
which it emits. 

Equimolecular Solutions. — Solutions 
which contain, in the same quantity of 



Equ.] 



774 



[Eth, 



the solvent, quantities of the dissolved 
substance proportional to their molecular 
weights. 

Equipotential. — Of or pertaining to an 
equality of potential. 

Equipotential Electrostatic-Surfaces. 
(1) Surfaces on or surrounding charged 
bodies, all points of which are at the same 
electric potential. (2) Electric surfaces 
perpendicular to the lines of electric 
force, over which a quantity of electricity, 
considered as being concentrated at a 
point, may be moved without doing work. 

Equipotential Magnetic-Surfaces.— 
Surfaces surrounding the poles of a mag- 
net or system of magnets, where the 
magnetic potential is the same. 

Equivalent Air-Gap. — An air-gap which 
would have the same magnetic resist- 
ance as a joint, assuming the permeabil- 
ity of the metal to be unaffected by the 
cutting. 

Equivalent Conductance. — (1) A con- 
ductance such that if inserted in a sinu- 
soidal-current circuit would absorb en- 
ergy at the same rate as the actual 
conductance in a non-sinusoidal current 
circuit. (2) Virtual conductance. (3) 
The effective conductance of an alternat- 
ing-current system or conductor. 

Equivalent Conductivity.— The mole- 
cular conductivity of a solution divided 
by the valency. 

Equivalent Impedance.— Such an im- 
pedance in a simple-harmonic-current cir- 
cuit as would, with the same effective 
current strength, absorb energy at the 
same rate as an actual impedance in a 
complex-harmonic-current circuit. 

Equivalent Reactance. — Such a react- 
ance in a simple-harmonic-current circuit 
as would permit energy to be absorbed, 
with the same effective current strength, 
at the same rate as an actual reactance 
in a complex-harmonic-current circuit. 

Equivalent Resistance.— (1) A single 
resistance which may replace a number 
of resistances in a circuit without alter- 
ing the current traversing it. (2) Such a 
resistance in a simple-harmonic-current 
circuit as would permit energy to be ab- 
sorbed, with the same effective current 
strength, at the same rate as an actual re- 
sistance in a complex-harmonic-current 
circuit. (3) The effective resistance of an 
alternating-current system or conductor. 

Equivalent Resistance and Induct- 
ance. — In an alternating-current circuit, 
or system of circuits, such a resistance 
and inductance as would, if substituted 
for the actual system, cause the same 



strength and activity of current to pass 
through the conducting leads. 

Equivalent Resistance and Reactance. 
Such a resistance and reactance in a 
simple alternating-current circuit, as 
would cause the same current both in 
magnitude and phase to flow in the main 
leads, as when a number of multiple arc 
circuits are connected to them. 

Equivalent Sinusoid. — A curve repre- 
senting a sinusoid, which, for purposes of 
analytical investigation, has been taken as 
the equivalent in power of a curve of 
pressure or current which is not sinu- 
soidal. 

Equivolt. — A term proposed for unit of 
electric energy applied especially to 
chemical decomposition. (Not in general 
use.) 

Erb's Standard Size of Electrodes. — 
Standard sizes of electrodes, generally 
adopted in electro-therapeutics. 

Erg.— (1) The C. G. S. unit of work, or 
the work done when unit C. G. S. force 
is overcome through unit C. G. S. dis- 
tance. (2) The work accomplished when 
a body is moved through a distance of 
one centimetre with the force of one 
dyne. (3) A dyne-centimetre. 

Erg-Meter. — (1) An apparatus for meas- 
uring the work of an electric current in 
ergs. (2) An energy-meter. 

Ergometer. — An erg-meter. 

Erg : s. — An abbreviation proposed for erg- 
per-second, the C. G. S. unit of power. 

Erg-Ten. — (1) A term proposed for ten mil- 
lion ergs ; 10 10 ergs, or one erg multiplied 
by 10 10 . (2) A kilo-joule. 

Error. — In telegraphy, a blunder or inac- 
curacy either of transmitted signals, as in 
sending a message, or of deciphered, re- 
transmitted, or recorded signals, as in re- 
ceiving a message. 

Escape, Electric. — (1) A partial loss of 
current to earth by imperfect insulation. 
(2) A loss of charge on an insulated con- 
ductor. 

Escapement, Electric. — An electrically 

actuated clock escapement. I 

Essential Resistance. — A term some- 
times used for internal resistance. 

Etching, Electric. — A term sometimes 
used for electric engraving. 

Ether. — The highly tenuous, elastic fluid 
that is assumed to fill all space, and by 
whose vibrations or waves, light, radiant 
heat, and electro-magnetic radiation are 
transmitted. 



Eth.] 



775 



[Exp. 



Ether Flow Vortices.— Vortices in the 
ether upon whose alleged existence is 
based a hypothesis for the explanation of 
magnetic phenomena. 

Ether Path of Reluctivity.— A concep- 
tion employed in studying the reluctivity 
of a magnetic medium which regards the 
magnetic flux as taking two multiple- 
connected paths, one the path of metallic- 
reluctivity through the mass of the sub- 
stance, and the other the path of ether- 
reluctivity, through its associated ether. 

Ether Streamings. — Streamings that are 
assumed to exist in the ether around a 
magnet, or around a charged conductor. 

Ethereal. — Of or pertaining to the ether. 

Eudiometer. — (1) A voltameter in which 
separate graduatedvessels are preparedfor 
the reception and measurement of the 
gaseous products evolved during electro- 
lysis. (2) A graduated glass tube for hold- 
ing and measuring the volume of the 
evolved gas. 

Eudiometric. — Of or pertaining to an 
eudiometer. 

Eudiometrically . — By means of an eudio- 
meter. 
Evanescent Telegraphic Signal.— Any 

telegraphic signal which is not perma- 
nently recorded. 

Evaporation. — The change from the liquid 
to the vaporous state. 

Evaporation, Electric— The formation 
of vapors on the surfaces of solid or 
liquid substances by the influence of neg- 
ative electrification. 

Even Harmonies.— In a complex harmon- 
ically-varying quantity, the harmonics 
whose frequencies are even multiples of 
the fundamental frequency. 

Ewing's Theory of Magnetism.— A 
theory of magnetism proposed by Ewing, 
based on the assumption of originally 
magnetized particles. 

Excitability of Nerve or Muscular 
Fibre, Electric— The effect produced 
by an electric current in stimulating a 
nerve of a living animal, or in producing 
an involuntary contraction of a muscle. 

Excitant. — (1) That which excites. 

(2) The electric or magnetic force which 
energizes a receptive device. 

Excitation. — (1) The production of elec- 
trification by any means. (2) The pro- 
duction of magnetism by any means. 

(3) The energizing of any electro or mag- 
neto-receptive device. (4) The produc- 
tion of the magnetic field in a dynamo 



or motor. (5) The stimulation of a 
muscle or nerve fibre. 
Exciter. — Anything which causes an ex- 
citation. 

Exciter Dynamo.— A dynamo used for 
the separate excitation of another dynamo. 

Exciter of Field.— A dynamo, or other 
electric source, employed in the separate 
excitation of the field of a dynamo. 

Exciting Ampere-Turns.— The ampere- 
turns in the field-winding of a generator 
or motor employed for the excitation of 
its field. 

Exciting Fluid or Liquid of Voltaic 
Cell. — The electrolyte of a voltaic cell. 

Execution, Electric— Inflicting capital 
punishment by electricity. 

Exhaust Fan, Electric— An electrically 
driven exhaust fan. 

Exhaust Wheel, Electric— An electri- 
cally driven rotary device for drawing or 
exhausting the air from an apartment. 

Exhausted Storage Cell.— An emptied 
storage cell. 

Exhausted Voltaic Cell.— A voltaic cell 
in a state of exhaustion. 

Exhaustion, Electric— Physiological ef- 
fects resembling those produced by sun- 
stroke, resulting from prolonged exposure 
to powerful voltaic arcs. 

Exhaustion of Primary Voltaic Cell. 

. The inability of a primary voltaic cell 
to furnish any further current, unless 
fresh electrolyte, or new positive ele- 
ments, or both, are supplied to it. 

Exhaustion of Secondary Voltaic 
Cell. — The inability of the cell to furnish 
any further current until again acted on 
by a charging current. 

Exosmosis. — The osmotic current which 
is directed towards the lower level. 

Exothactic Cut-Out. — A cut-out de- 
signed to remove a device from a circuit. 

Exothatic Switch. — A switch designed to 
cut a device out of circuit. 

Exothermic. — Of or pertaining to an exo- 
thermic reaction. 

Exothermic Reaction. — A chemical re- 
action attended by the evolution of heat. 

Expanding Magnetic Whirls.— Mag- 
netic whirls sent out from a conductor 
through which a current of gradually in- 
creasing strength is passing, or from a 
magnet whose magnetism is gradually in- 
creasing. 

Expanding of Magnetic Field.— The 
increase in the strength of a magnetic 
flux and of the region traversed by it. 



Exp.] 



776 



[Eye. 



Expansibility.— (1) The quality of being 
expansible. (2) Possessing the capacity 
for expansion. 

Expansion. — The act of increasing in 
length, surface, or volume. 

Expansion, Electric. — The increase in 
volume produced in a body by giving it 
an electric charge. 

Expansion Joint. — A joint suitable for 
tubes or pipes exposed to considerable 
changes of temperature, in which a slid- 
ing joint is provided to safely permit a 
change in length on expansion or contrac- 
tion. 

Expended Energy.— The energy em- 
ployed to produce any result. 

Exploder, Electric. — A small magneto- 
electric machine used to produce a high 
electromotive force, employed in the 
direct firing of blasts. 

Exploration of Magnetic Field. — 

Mapping out the location and density of 
a magnetic field by any suitable means. 

Explorer, Electric. — An apparatus oper- 
ated by means of induced currents for 
the purpose of locating bullets and other 
foreign metallic substances in the human 
body. 

Exploring Needle.— (1) A form of ex- 
ploring probe. (2) A magnetic needle 
employed in exploring a magnetic field. 

Explosive Distance. — A term sometimes 
employed for sparking distance. 

Extension Bell. — (1) An extension call- 
bell. (2) A call-bell situated at a distance 
from the apparatus to which it calls at- 
tention. 

Extension Call-Bell.— An additional bell 
connected with the call-bell of a telephone 
or other device, and placed in some other 
portion of a building, for the purpose of 
calling the subscriber to the instrument 
when he may be in a distant part of the 
house. 

Extension Plates for Poles.— Double 
plates forming between them a loop for 
an upper extension or branch of a guy- 
rod supporting a pole.- 

Extension Push-Button.— An auxiliary 
push-button placed at a distance from a 
main push-button. 

Extensometer. — A form of apparatus for 
measuring the elongation of a substance 
under stress. 

External Armature Generator. — A 
generator in which the armature is ex- 
ternal to the field frame. 



External Characteristic of Dynamo.— A 

curve showing the E. M. F. at the termi- 
nals of a dynamo under varying currents, 
as distinguished from an internal charac- 
teristic showing the internal E. M. F. 

External Circuit.— That part of a circuit 
with which an electric source is con- 
nected that is external to that electric 
source. 

External Magnetic Circuit. — (1) That 
portion of a magnetic circuit which lies 
outside the magnetic source. (2) That 
portion of the circuit of a magnet which 
lies outside its mass or core. 

External Magnetic Field.— That portion 
of a magnetic field which lies outside the 
body of a magnet. 

External - Secondary Resistance. — In 
the secondary circuit of a transformer, 
the resistance external to the transformer. 

Extra-Current Direct.— A term some- 
times emploj^ed for the current produced 
in the primary of a transformer on the 
breaking of its circuit. 

Extra-Current Inverse.— A term some- 
times employed for the current produced 
in the primary current of a transformer 
on the making of its circuit. 

Extra-Current Neutralizes— A device 
for reducing electro-magnetic retardation 
which consists of a shunted condenser in- 
serted in the main circuit. 

Extra Currents. — Currents produced in a 
circuit by self-induction. 

Extra-High-Potential System. — In the 

National Electric Code a potential above 
3000 volts. 

Extra-High-Potential "Wires. — Wires 
suitable for use in extra-high-potential 
systems. 

Extraneous Field.— A leakage magnetic 
field. 

Extraordinary Resistance.— A term 
sometimes used for external resistance. 
(Not in use.) 

Extra-European Message. — In Europe a 
message sent to or received from some 
point beyond the geographical limits of 
Europe. 

Extra-Polar. — Lying beyond or outside 
the poles. 

Extra-Polar Region. — In electro-thera- 
peutics, the region which lies outside or 
beyond the therapeutic electrodes. 

Eye-Piece. — The ocular of a telescope or 
microscope. 



E.] 



777 



[Fan 



F. — A symbol proposed for farad, the prac- 
tical unit of capacity. 

F. — A symbol proposed for force. 

eF. — A symbol for magnetomotive force. 
(Partly international usage.) 

/. — A symbol proposed for force. (Partly 
international usage.) 

F. M. — A contraction for field magnets. 

F. W. Gr. — A contraction for French wire 
gauge. 

Fac-Simile Telegraph. — A general term 
embracing the apparatus employed in 
fac-simile telegraphy. 

Fac-Simile Telegraphy.— (1) A system 
whereby a fac-simile or copy of a chart, 
diagram, picture, or signature, is tele- 
graphically transmitted from one station 
to another. (2) Pan-Telegraphy. 

Factor. — Each of the several quantities 
which are multiplied together to form a 
product. 

Factor of Safety.— (1) The ratio of the 
computed or measured strength of a 
structure to the maximum strength it 
will be called upon to exert. (2) An 
amount by which the breaking load or 
stress in any system must be divided in 
order to obtain the safe load or stress. (3) 
A multiple of the calculated strength re- 
quired of a structure adopted to ensure 
safety. 

Factor of Safety of Demagnetization.— 
The ratio of the demagnetizing force in 
an aero-ferric magnetic circuit corre- 
sponding to an actually existing residual 
flux density, to the actually existing 
mean demagnetizing force. 

Fahrenheit Thermornetric Scale.— The 
thermometric scale in which the length of 
the thermometer tube, between the melt- 
ing point of ice and the boiling point of 
water, is divided into 180 equal parts or 
degrees. 

Fall-Back Indicator. — A term sometimes 
employed for drop indicator. 

Fall of Potential.— The drop of poten- 
tial. 

Fall of Pressure. — The drop of pressure. 

Pall of Pressure in Active Conductor. 
The fall of pressure due to the passage 
of the current, and equal to the product 
of the current strength by the resistance. 



False.— (1) Untrue. (2) Provisionally as- 
sumed. 

False Discharge of Submarine Cable. 

An oscillatory discharge produced in a 
cable as distinguished from an aperiodic 
discharge. 

False Electric Current.— A virtual elec- 
tric current distribution which has no ac- 
tual existence, but which is assumed in 
order to comply with the conditions of 
an electro-magnetic field. 

False Electrification. — A virtual electri- 
fication having no real existence, but 
which may be assumed in order to deter- 
mine a given distribution of electro-mag- 
netic energy in a medium. 

False Magnetic Currents. — Virtual mag- 
netic currents having no real existence 
but assumed for the purpose of conform- 
ing to the requirements of a given electro- 
magnetic distribution. 

False Magnetic Poles of Earth.— A 

term proposed to designate the place or 
places on the earth which apparently act 
as magnetic poles, in addition to two true 
magnetic poles in the neighborhood of 
the earth's geographical poles. 

False Resistance. — A resistance arising 
from a counter electromotive force, and 
not directly from the dimensions of the 
circuit, or from its specific resistance. 

False Zero. — (1) A zero of a measuring in- 
strument accepted at the position it nat- 
urally assumes under the action of forces 
other than those impressed in the meas- 
urement. (2) A zero taken midway be- 
tween two unequal and opposite deflec- 
tions of a measuring instrument. (3) In 
Wheatstone-Bridge measurement, the po- 
sition of the galvanometer needle natu- 
rally assumed under the influence of E. 
M. F. in the bridge before the application 
of the testing battery. (4) In cable test- 
ing the position of the spot of light when 
the testing battery is disconnected and the 
galvanometer short-circuit key is open. 
(5) A cable zero, or zero to the existing 
current in a cable. (6) The natural zero. 

Fan Guard. — A wire guard placed around 
an electric fan, to prevent the revolving 
blades from coming in contact with sur- 
rounding objects. 

Fan Motor.— (1) An electric motor suit- 



.Far.] 



778 



[Fee. 



able for driving a fan. (2) An electric 
motor carrying a fan. 

Far-Leading Dynamo. — A motor-dyna- 
mo placed as a shunt across a pair of long 
mains, to compensate for their drop in 
voltage. 

Farad. — (1) The practical unit of electric 
capacity. (2) Such a capacity of a con- 
ductor or condenser that one coulomb of 
electricity is required to produce therein 
a difference of potential of one volt. 

Faraday Effect.— The rotation of the 
plane of polarization of a beam of plane 
polarized light on its passage along a 
magnetic field. 

Faraday's Cube. — An insulated room or 
cube covered on the inside with tin-foil, 
which, when charged on the outside, gives 
no electrical indications to an observer on 
the inside even to delicate instruments. 

Faraday's Dark Space.— The gap in the 
continuity of the luminous discharges 
that occur between the positive and nega- 
tive electrodes. 

Faraday's Disc— A metallic disc movable 
in a magnetic field on an axis parallel to 
the direction of the flux. 

Faraday's Wet.— An insulated net of cot- 
ton, gauze, or other similar conducting 
material, capable of being turned inside 
out without being thereby discharged, 
and employed for demonstrating the fact 
that the charge of an insulated conductor 
is limited to its outer surface. 

Faradic. — Of or pertaining to Faraday. 

Faradic Adapter. — A device for readily 
permitting commercial incandescent- 
light circuits to be employed for electro- 
therapeutic work, with an induction 
coil. 

Faradic Battery. — A term erroneously 
used for a faradic coil, or induction coil. 

Faradic Brush. — A brush-shaped elec- 
trode employed in the medical applica- 
tion of electricity. 

Faradic Coil. — A term sometimes used for 
a faradic machine, or medical induction 
coil. 

Faradic Current.— (1) In electro-thera- 
peutics, a current produced by an induc- 
tion coil, or magneto-electric machine. 
(2) A rapidly alternating current, as dis- 
tinguished from a direct current. 

Faradic Excitability. — Muscular or ner- 
vous excitability produced by the em- 
ployment of faradic currents. 

Faradic Excitation. — The excitement of 
muscle or nerve fibre by faradic cur- 
rents. 



Faradic Induction Apparatus.— An in- 
duction coil apparatus for producing fara- 
dic currents. 

Faradic Irritability.— Muscular contrac- 
tions produced by the action of faradic 
currents on a nerve. 

Faradic Machine.— Any machine for 
producing faradic currents. 

Faradism. — A word sometimes employed 
for faradization. 

Faradization. — In electro-therapeutics, 

the effects produced on the nerves or 

muscles by the use of faradic currents. 
Faradization of Skin.— Treatment of the 

skin by faradic currents. 
Fast Repeater.— A telegraphic repeater 

or translator especially designed for rapid 

signalling. 
Faradometer. — A term proposed for an 

instrument designed for the measurement 

of faradic currents. 
Fast-Speed Telegraphy.— Automatic or 

machine telegraphy. 
Fathom. — (1) A unit of length equal to six 

feet or two yards. (2) Approximately, the 

one-thousandth part of a nautical mile. 

Fault. — Any defect in the proper working 
of a circuit, due to ground contacts, cross 
contacts, or disconnections. 

Fault Resistance.— The resistance of a 
fault. 

Fault Searcher. — An instrument em- 
ployed in connection with a telephone or 
other sensitive current-detector, for de- 
termining the moment when a portion of 
the cable containing the fault comes on 
board ship, while the same is being picked 
up for purposes of repair. 

Feather Edge.— A strip of wood laid by 
the side of a layout of cable in a cable 
tank to protect it from the pressure of 
superincumbent flakes. 

Feed. — (1) To supply with an electric cur- 
rent. (2) To move or regulate one or 
both of the carbon electrodes in an arc- 
lamp. 

Feed-Line. — A feeder. 

Feed- Wire Insulator.— An insulator em- 
ployed for the support of a feed-wire. 

Feeder. — One of the conducting wires 
through which the" current is distributed 
to the main conductors, as distinguished 
from a conductor which supplies trans- 
lating devices directly. 

Feeder-and-Main System of Distri- 
bution. — A system for the transfer of 
electric energy in which, for the pur- 
pose of preventing too great a drop of 



Fee.] 



779 



[Fer. 



pressure on the' mains, they are connected 
at suitable points to the feeder wires, in- 
stead of to the generator or generators. 

Feeder Ammeter. — An ammeter placed 
in the circuit of a feeder, usually at a 
switchboard. 

Feeder Block. — A block containing a 
feeder cut-out. 

Feeder Box. — A distribution box supplied 
by a feeder, into which a feeder enters to 
receive its distributing connections. 

Feeder Clamp. — Any clamping device for 
connecting or fastening a feeder wire to a 
trolley wire or to a main. 

Feeder Cleat. — A clamp furnished with a 
device whereby a feeder wire may be 
readily connected to a trolley wire. 

Feeder Distribution. — A feeder - and- 
main system of distribution. 

Feeder Equalizer. — A resistance coil in- 
serted in the circuit of a feeder, with or 
without means for adjustment, for the 
purpose of equalizing the pressure at the 
feeding points. 

Feeder - Equalizer Resistance. — A 
feeder regulator. 

Feeder-Equalizer Switch. — An equa- 
lizer switch employed in feeder systems. 

Feeder for Trolley Conductor. — A wire 
or conductor of low resistance employed 
for transmitting electric pressure directly 
from the power station to some distant 
point of the trolley wire, for the purpose 
of maintaining the potential at that point. 

Feeder-Mechanism for Arc-Lamps.— 
An arc-lamp feeding mechanism. 

Feeder Panel of Switchboard.— A panel 
of a switchboard, furnished with the 
necessary switches, voltmeters, ammeters, 
and safety devices, to which the feeder 
wires are connected. 

Feeder Plug.— A metallic bolt which, 
when inserted in a trolley car in place of 
an insulated bolt, establishes connection 
between the trolley wire and a feeder 
through the span wire. 

Feeder Potential.— (1) The electric poten- 
tial of any feeder relatively to ground. (2) 
The difference of potential between any 
pair of feeder conductors. 

Feeder Regulators. — (1) Artificial re- 
sistances introduced into the circuit of 
idle feeders, so as to increase the drop of 
pressure existing in them. (2) A form of 
special transformer, whose primary is con- 
nected across the mains and its secondary 
is in series with one feeder wire, and is 
employed to produce a pressure which, 
by means of a suitable reversing switch, 



either aids or opposes the alternating pres- 
sure on the mains. (3) A term sometimes 
applied to boosters. 

Feeder Switch. — Any switch placed on a 
feeder panel that is connected with the 
separate feeders and employed for the 
purpose of connecting or disconnecting a 
generator with such feeder. 

Feeder System.— A system of distribution 
in which the service wires are connected 
by means of feeders to certain centres of 
distribution. 

Feeder Tubes.— Underground tubes pro- 
vided for the reception of the feeder wires. 

Feeders. — Wires supplying currents to 
main conductors at different points, to 
equalize their potential under load, as 
distinguished from wires supplying cur- 
rents directly to the load. 

Feeding Centre.— (1) A centre of distri- 
bution supplied by a feeder. (2) A feed- 
ing point. 

Feeding Conductors or Wires.— Feed- 
ers. 

Feeding Device or Mechanism for 
Electric Arc-Lamps. — A device for 
maintaining the carbon electrodes of an 
arc-lamp at a constant distance apart dur- 
ing their consumption. 

Feeding Point. — (1) A point of connection 
between a feeder and the mains. (2) A 
feeding centre. 

Fender. — A device placed in front of a 
street car for preventing accidental in- 
jury to pedestrians passing in front of the 
moving car. 

Ferranti Effect. — (1) An increase in the 
electromotive force or difference of po- 
tential of mains or conductors carrying- 
alternating currents, which exists towards 
the end of the same furthest from the 
terminals that are connected with the 
source. (2) A negative drop in pressure. 

Ferric Circuit. — A ferric-magnetic cir- 
cuit. 

Ferric Inductance Coil.— An inductance 
coil provided with an iron core. 

Ferric Magnetic Circuit. — A magnetic 
circuit composed wholly of iron. 

Ferric Path of Reluctivity.— That por- 
tion of the flux paths through iron or 
other magnetic material, in which the 
flux passes through the metal proper, as 
distinguished from that which is assumed 
to pass through the ether lying within 
such material. 

Ferro-Magnet. — A word sometimes em- 
ployed for an ordinary magnet made of 
paramagnetic material, as distinguished 



Fei\] 



780 



[Fil. 



from a diamagnet, or one formed of dia- 
magnetic material. 
Ferro-Magnetic. — A word sometimes em- 
ployed for paramagnetic. 

Ferro-Magnetic Substances. — Para- 
magnetic substances. 

Ferro-Magnetism.— Magnetism possessed 
by iron or other paramagnetic substances. 

Ferro-Manganese Alloys.— Various al- 
loys employed for the wires of resistance 
coils, whose electric resistance is not sen- 
sibly affected by changes of temperature. 

Fibre Suspension.— Suspension of a 
needle or other system by a fibre of un- 
spun silk, quartz or other suitable ma- 
terial. 

Fibrone. — A variety of insulating ma- 
terial. 

Fietive Layers. — Layers in a dielectric 
possessing equipotential surfaces due to 
the accumulation of charges insufficient 
to produce a constant potential within the 
dielectric, but, nevertheless, capable of 
modifying its potential. 

Fiducial Point. — (1) A fixed point or refer- 
ence point in the scale or indications of 
a galvanometer or other measuring in- 
strument. (2) A temporary zero point. 

Field. — (1) A term sometimes used for a 
magnetic field. (2) A term sometimes 
used for an electrostatic field. 

Field Coils. — The field-magnet coils of a 
dynamo-electric machine or motor. 

Field, Electric— A term sometimes used 
in place of electrostatic field. 

Field Frequency. — The frequency of 
revolution in a rotating magnetic-field. 

Field-Magnet Coils.— The magnetizing 
coils on the field magnets of a dynamo or 
motor. 

Field-Magnet Regulating Box.— (1) 
The field regulating box. (2) A resistance 
box inserted in the circuit of the field 
magnets. 

Field Magnets. — The magnets which pro- 
duce the magnetic field or flux in which 
the armature of a dynamo or motor ro- 
tates. 

Field of Force. — (1) The space traversed 
by electrostatic or magnetic flux. (2) An 
electrostatic or magnetic field. 

Field of Vortex Ring.— The field of in- 
fluence possessed by a vortex ring. 

Field Poles.— The poles of the field mag- 
nets of a dynamo or motor. 

Field-Regulating Box. — (1) A resistance 
box, inserted in series with the field mag- 
net coils, for the purpose of varying the 



strength of the magnetizing current. (2) 
A regulating box or rheostat connected 
with the field circuit of a generator, for 
the purpose of controlling its pressure. 

Field Rheostat. — A field-regulating box. 

Field Spools of Dynamo or Motor. — 
The magnetizing coils of the field-mag- 
nets of a dynamo or motor. 

Field Strength.— The magnetic intensity 
of afield. 

Field Telegraph Line.— A semi-perma- 
nent telegraph line employed in army 
telegraphy, connecting headquarters with 
the divisional generals, and such other 
stations as may be required. 

Field Windings of Induction Motor. 
Field windings so arranged as to produce 
a rotating magnetic field when supplied 
by multiphase or uniphase currents. 

Fieldless Motor.— A form of motor in 
which the torque is obtained by the mu- 
tual attraction of separate armatures. 

Figure-of-Eight Wire.— A trolley wire 
whose cross-section resembles in outline 
the figure 8. 

Figure of Merit of Galvanometer. — 
The reciprocal of the current strength re- 
quired to produce a deflection of a gal- 
vanometer needle through one division of 
the scale. 

Figures, Electric— Figures of various 
shapes produced on electrified surfaces 
by the arrangement of dust particles, or 
vapor vesicles, under the influence of elec- 
tric charges. 

Filament. — A slender thread or fibre. 

Filament of Incandescent Lamp.— The 
incandescing conductor of an incandes- 
cent electric lamp. 

Filament Shadows.— Markings produced 
on the inner surface of an incandescent 
lamp chamber by the deposition thereon 
of carbon from the filament. 

Filamentous Armature Core.— A lam- 
inated armature core formed of iron 
wire. 

Filar Micrometer. — A micrometer ocular 
in which an angular or linear distance is 
measured by the movement of a fibre 
across the field of view, under the control 
of a screw adjustment. 

Film.— (1) A thin pelicle or layer. (2) A 
name sometimes given to an electro-plat- 
ing or deposit. 

Film Cut-Out.— (1) A cut-out in which a 
film or sheet of paper, or mica, is inter- 
posed between a line plate and the earth 
plate, which, when punctured by a spark, 
short-circuits the instruments on the 



Fil.] 



781 



[Fiv, 



line. (2) A cut-out for a series incan- 
descent lamp, in which a film of paper or 
other insulator is interposed between the 
lamp terminals, so that when the filament 
breaks, the pressure rises at the termi- 
nals, and both punctures and short cir- 
cuits the film, thus cutting out the broken 
lamp. 
Film Lightning- Arrester.— A film-cut- 
out lightning-arrester. 

Filter Pump. — A pump employed for in- 
creasing the rapidity of filtration of a 
liquid by atmospheric pressure. 

Filtration. — The separation of a liquid 
from an undissolved solid or solids me- 
chanically suspended therein. 

Final Cable Test.— (1) The test made 
after a cable is laid, to ascertain if the 
electrical specifications have been met. 

Final Cable Splice.— (1) The splice in a 
cable which completes it. (2) The last 
splice. 

Finding Earth.— In telegraphy, making 
earth. 

Finishing Brushes.— In electro-plating, 
finer brushes than scratch brushes, em- 
ployed for polishing. 

Fire-Alarm Annunciator. — An annun- 
ciator used in connection with a system 
of fire alarms. 

Fire-Alarm Contact.— A contact so ar- 
ranged that an alarm is automatically 
given when a predetermined temperature 
is reached. 

Fire-Alarm Signal-Box.— A signal box 
placed in a street, or other convenient 
position, by means of which an alarm of 
fire can be sent. 

Fire-Alarm Telegraph. — A general term 
embracing the apparatus employed in 
fire-alarm telegraphy. 

Fire-Alarm Telegraphy.— A system of 
telegraphy by means of which alarms can 
be sent to a central station, or to the fire- 
engine houses in a district, from call-boxes 
placed on the line, or from automatic fire- 
alarm contacts. 

Fire Ball. — A term sometimes applied to 
globular lightning. 

Fire Cleansing.— Removing grease by the 
action of fire from articles that are to be 
electro-plated. 

Fire Extinguisher, Electric— A ther- 
mostat or mercurial contact, which auto- 
matically completes a circuit and thus 
turns on a water jet for extinguishing a 
fire, on a certain predetermined increase 
of temperature. 



Fire-Fly Radiation.— Any form of lumi- 
nous radiation containing a small propor- 
tion of non-luminous frequencies, and, in 
this respect, similar to the radiation of 
the fire-fly or glow-worm. 

Fire-G-low. — A term employed by the an- 
cients for an aurora. 

Fire Telegraph.— A fire-alarm telegraph. 

Firing Battery. — A battery employed 
in mining, in military, or in naval opera- 
tions for firing a fuse. 

Firing Filament.— (1) Subjecting suitably 
shaped carbonizable material to the car- 
bonizing process, so as to prepare it for 
use as the filament of an incandescent 
lamp. (2) Carbonizing a filament. 

Firing Rheostat.— A rheostat in the firing 
circuit of a fuse detonator. 

Fish Plate. — In a system of electric rail- 
roads, the plate connecting contiguous 
rails by bolts. 

Fished Wires. — Wires that have been in- 
troduced into ducts by the application of 
the fishing process. 

Fishes, Electric. — Various fishes, such as 
the eel and the ray, which possess the 
ability of either protecting themselves, or 
securing their prey, by giving electric 
shocks to the objects touching them. 

Fishing Box. — A term sometimes nsed 
for junction box. 

Fishing Conductors.— The process of 
threading conductors through the spaces 
left for them in floors, walls, tubes, or 
conduits by securing their ends to the 
end of a convenient length of wire and 
hauling the latter through in advance. 

Fishing Process. — The process employed 
for the fishing of wires. 

Fishing of Wires. — The process of draw- 
ing a wire into its place in a building 
through floors, walls, or ceilings by 
placing a wire in a hole at one end and 
engaging it by a hook from the other, so 
as to draw it through. 

Fiske's Electric Range-Finder.— A de- 
vice by means of which the distance of an 
object can be readily obtained. 

Fiske's Electric Range-Finder. — A de- 
vice by means of which the exact distance 
of an enemy's ship or other target can be 
readily determined. 

Fittings.— (1) — The sockets, holders, arms, 
etc., required for holding and supporting 
incandescent electric lamps. (2) Incan- 
descent light fixtures. 

Five-Point Jack. — In a multiple tele- 
phone switchboard, a jack having five 
separate contact points. 



Fiv.] 



782 



[Fie, 



Five-Point Branching Jacks.— In a mul- 
tiple telephone branching switchboard, 
five-point jacks connected in parallel to 
a subscriber's line. 

Five-Wire System.— A system, similar 
in its arrangement to the three-wire sys- 
tem, in which four series-connected dy- 
namos are suitably connected to five 
wires or conductors. 

Fixed Call-Boxes. — District call-boxes so 
arranged with burglar-alarm circuits, that 
the alarm is sent to the district station 
connected therewith. 

Fixed Electric Lamp. — A stationary in- 
candescent lamp as distinguished from a 
portable lamp. 

Fixed Resistance. — A resistance whose 
value is approximately constant, as dis- 
tinguished from a regulable resistance. 

Fixed Secondary. — The secondary of an 
induction coil that, as is common in such 
coils, is fixed, in contradistinction to a 
movable secondary. 

Fixture Cut-Out.— A cut-out or safety 
plug attached to an electric lamp. 

Fixture Electric— (1) Fittings for electric 
light. (2) A support or electrolier for one 
or more incandescent lamps rigidly fas- 
tened to a wall or ceiling. (3) Any elec- 
tric apparatus forming part of a perman- 
ent installation. 

Fixture Wire. — A class of insulated wire 
suitable for use in electric fixtures. 

Flag of Balance. — A small arm pivoted 
friction-tight upon the movable coils of 
an electro-dynamometer balance, and 
capable of adjustment for the purpose of 
obtaining a correct initial balance. 

Flag Signalling. — A system of semaphoric 
signalling in which a light flag, held in 
the hand, is waved to the left for the 
dots, and to the right for the dashes, of 
the Morse or Continental Code. 

Flake of Cable. — A single horizontal layer 
of a coiled cable. 

Flame. — A mass of imflammable gas in a 
state of combustion. 

Flaming Discharge.— The white, flam- 
ing, arc-light discharge that occurs be- 
tween the terminals of a high-frequency, 
high-potential induction coil, when the 
current through the primary is increased 
in strength beyond that required for the 
sensitive-thread discharge. 

Flaming of Carbon Arc. — An irregular 
burning of a voltaic arc, which occurs 
when the carbons are too far apart, and 
the current strength somewhat exceeds 
the normal. 



Flash Signalling.— A method of sema- 
phoric signalling by means of a lantern, 
or torch. 

Flashed Carbon Filaments. —Carbon 
filaments that have been subjected to the 
flashing process. 

Flashing. — Subjecting carbons to the 
flashing process. 

Flashing Lights.— (1) Lights employed 
in light -house illumination, that are 
periodically shaded, so as to produce an 
intermittenoe of the light, and thus to 
permit such light to be readily distin- 
guished from adjacent lights. (2) Any 
light whose intensity is periodically in- 
termitted. 

Flashing of Dynamo - Electric Ma- 
chine. — A name given to long flashing 
sparks at the commutator of a dynamo, 
due to the short-circuiting of the external 
circuit at the commutator. 

Flashing Process for Carbon Fila- 
ments. — A process for improving the 
electrical homogeneity of carbon fila- 
ments by the deposit of carbon in their 
pores and over their surfaces, by exposing 
the filaments to a gradually increasing 
electrical incandescence, while surround- 
ed by a carbonaceous gas or liquid. 

Flat Board. — A multiple telephone- 
switchboard whose surface Jies in a hor- 
izontal plane, as distinguished from a 
vertical board. 

Flat Cable. — A cable the separate con- 
ductors of which are laid up side-by-side, 
so as to form a flat-conductor. 

Flat Commutator-Segment. — A com- 
mutator segment that has, through wear 
or otherwise, acquired a flat surface. 

Flat Duplex-Cable.— A flat cable con- 
taining two separate conductors which 
are laid up side-by-side. 

Flat-Iron, Electric. — An electrically 
heated flat-iron. 



Flat-Ring Armature. — An armature 
"~ has the shape of a short cylin- 



whose core 
drical ring. 



Flats. — Those parts of commutator seg- 
ments, the surfaces of which, through wear 
or otherwise, have become lower than the 
other portions. 

Fleeting Knife of Cable Gear.— The 
adjustable guide on the drum of a cable 
machine, which leads the cable to the sur- 
face of the drum. 

Flexible. — Capable of being readily flexed 
or bent. 

Flexible Cable. — A stranded cable, or 
one which can be readily flexed or bent. 



Fie.] 



783 



[Flu, 



Flexible Conduit-System.— A system 
of conduits for underground wires, so 
constructed that the conductors or cables 
it is to contain can be introduced at any- 
time after its completion. 

Flexible Electric Heater.— An electric 
heater made of flexible material, so as to 
permit its local application to different 
parts of the body. 

Flexible Electric-Light Pendant.— 
A pendant for an incandescent lamp, 
formed by its flexible supporting conduc- 
tors. 

flexible Lamp-Cord.— (1) A flexible cord 
provided for supporting an incandescent 
lamp. (2) A flexible cord maintaining 
electric connection with a semi-portable 
incandescent lamp. 

Flexible Lead. — A conductor that is 
stranded for the purpose of obtaining 
flexibility. 

Flexible Twin-Lead. — A lead containing 
two separate parallel stranded conduc- 
tors. 

Float Dynamometer. — A dynamometer 
for measuring the mechanical activity of 
a dynamo or motor in which the machine 
is supported in a floating cradle and con- 
nected to its driver or load through a flex- 
ible coupling. 

Floor-Contact. — A contact placed on the 
floor and arranged so as to be readily 
operated by the foot. 

Floor Push.— A form of floor contact. 

Flow. — (1) The quantity of liquid escaping 
from an orifice in a given time. (2) The 
quantity of a fluid that flows past a given 
point in a given time. 

Flow, Electric— Electric current. 

Flow of Energy.— The transmission of 
energy through the medium or dielectric 
surrounding a conductor, now regarded 
as causing the current of electricity which 
was formerly assumed to flow through 
the conductor. 

Flow of Electrostatic Flux.— The trans- 
ference of electrostatic flux which con- 
stitutes, in reality, the so-called flow of 
electric current through a conductor. 

Flow of Heat.— The quantity of heat 
which passes through a thermal conductor 
when subjected to a certain difference of 
temperature. 

Flow of Magnetic Flux.— (1) The quan- 
tityof magnetic flux which passes through 
any magnetic circuit, under a given mag- 
neto-motive force, against a given mag- 
netic reluctance. (2) The time-rate of 
change of magnetic flux through a mag- 
netic circuit. 



Flow of Magnetic Induction.— The 

transmission of magnetic flux from one 
point of a magnetic circuit to another. 

Fluctuating Electromotive Force or 
Current.— An electromotive force or 
current which varies periodically in mag- 
nitude. 

Fluid. — (1) Any substance which readily 
flows. (2) A liquid or a gaseous sub- 
stance. 

Fluid Depolarizer.— A fluid substance 
employed in a voltaic cell as a depolar- 
izer. 

Fluid, Electric— Either of the assumed 
fluids which were formerly believed to be 
the cause of electric excitement. 

Fluid Insulator. — An oil insulator. 

Fluidity. — Possessing the properties of 
fluids. 

Fluorimeter.— A fluoroscope. 

Fluoresce. — To become luminous when 
exposed to radiant energy. 

Fluorescence. — The property possessed 
by certain solid and liquid substances of 
becoming luminous when exposed to 
radiant energy. 

Fluorescent.— Possessing the capability 
of fluorescing. 

Fluorescent Screen. — A screen covered 
with fluorescent materials. 

Fluorescing. — Emitting fluorescent light. 

Fluorograph, Electric. — A visible X-ray 

picture obtained on a fluorescent screen. 

Fluoroscopic Examination.— An X-ray 
examination of the human body by means 
of a fluorescent screen. 

Fluoroscopic Screen. — A screen covered 
with fluorescent material, and used in 
connection with the X-rays for fluoro- 
scopic examination. 

Fluoroscopy. — The art of examining the 
body by X-rays in connection with a 
fluoroscopic screen. 

Flush Box. — A box or space, flush with 
the surface of a roadbed, provided, in a 
system of underground wires or conduits, 
to facilitate the introduction of a con- 
ductor into the conduit, or the examina- 
tions of the conductors. 

Flush Key-Switch. — A key switch that 
is flush with, or does not project beyond, 
the surface of the wall in which it is 
placed. 

Flush of Current of Arc-Lamp. — The 
current that flows into an arc-lamp on 
starting, and which greatly exceeds in 
strength that which flows after the 
normal arc has been established. 



Elu.] 



784 



[Too. 



Plush Plate.— A plate on which flush 
push-buttons are mounted. 

Flush Push. — A push the upper surface 
of whose button or buttons are flush 
with the surface of the wall or plate in 
which it is placed. 

Flush Switch. — Any switch sunk in a 
wall, so that its plane outer surface is 
flush with the surface of the wall. 

Fluviograph, Electric— An apparatus 
for electrically registering the varying 
height of water in a tidal stream, or in 
the ocean, or, in general, for any differ- 
ences of water level. 

Flux. — (1) Magnetic or electric flux. (2) A 
surface integral of a vector quantity. 

Flux Density. — The quantity of magnetic 
flux per unit of area of normal cross- 
section. 

Flux Density per-Square-Centimetre 
or per-Square-Inch. — The quantity of 
magnetic flux passing through a circuit 
per square inch or square centimetre of 
area of normal cross-section. 

Flux of Displacement. — The surface in- 
tegral of electric displacement passing 
through a closed curve. 

Flux, Electric. — Electrostatic flux. 

Flux Horn. — A term proposed for the 
leading horn or polar edge of a generator 
which supplies the magnetic flux neces- 
sary for reversing the current in the 
armature coil under commutation. 

Flux Intensity.— (1) The density of a 
flux. (2) The surface density of a vector 
quantity at a point. 

Flux Leakage.— Any failure of flux to 
pass through its proper receptive device. 

Flux Lines of Electrostatic Force. — 

The lines or paths traversed by electro- 
static force. 

Flux of Heat. — The flow of heat per unit 
of time through a given area. 

Flux of Light.— (1) The total quantity of 
light emitted through a given area b} r a 
luminous source. (2) The total quantity 
of light emitted from a point source. 

Flux of Magnetic Induction.— The flow 
of magnetic induction. . 

Flux of Magnetism.— (1) The flow of 
magnetic induction. (2) The surface in- 
tegral of magnetic induction through a 
given surface. 

Flux Oscillations. — Oscillations in the 
intensity of electrostatic or of magnetic 
flux. 

Flux Phase. — The phase of a simple-har- 
monic magnetic flux. 



Fly or Flyer, Electric— A light wire 
wheel provided with pointed radial arms, 
which is set into rapid rotation by the 
escape of convection streams from its 
points, when connected with a charged 
body. 

Flying Break of Armature Conductor. 

A discontinuity in an armature wire that 
can only be detected when the armature 
is rotating, owing to the influence of 
centrifgual force. 

Flying Soundings.— Approximate sound- 
ings, in depths not exceeding two hundred 
fathoms, obtained without decreasing the 
speed of the ship below five or six knots 
per hour. 

Focal Length.— (1) The distance of a focus 
from a lens. (2) When not otherwise 
specified, the principal focal length of a 
lens or mirror. (3) The distance from 
the optical centre of a mirror or lens at 
which parallel rays are brought to a 
focus. 

Focometer. — An apparatus for readily de- 
termining the focus of a lens or optical 
combination. 

Focus. — A point before or back of a mir- 
ror or lens, where all the rays of light 
coming from the lens or mirror either 
meet, or seem to meet. 

Focusing. — Altering the distance between 
an object, and a lens or mirror, in order 
to obtain a sharp image of the object. 

Focusing Arc-Lamp. — An arc-lamp de- 
signed for use in connection with a re- 
flector or lens, whose mechanism feeds 
both carbons, and so permits the arc to 
be maintained at the focus of the reflector 
or lens. 

Fog, Electric — A dense fog which some- 
times occurs when there is an unusually 
large quantity of free electricity in the 
atmosphere. 

Foiled Conductor. — A term applied to a 
conductor whose insulating coating is 
covered by a thin coating or layer of tin 
foil or lead. 

Following Edges of Pole-Pieces of 
Motor. — Those edges of the pole-pieces of 
a motor which the armature is leaving. 

Following Horns of Pole-Pieces of 
Dynamo. — Those edges or terminals of 
the pole-pieces of a dynamo which the 
armature is leaving. 

Foot-Candle. — A unit of illumination: 
equal to the normal illumination pro- 
duced by a standard candle at the dis- 
tance of one foot. 

Foot-Grain. — A standard for comparing 
the resistances of wires at a given tern- 



Foo.] 



785 



[Fou. 



perature, the length of the wire being one 

foot, and its weight one grain. 
Foot-Pound.— (1) A unit of work. (2) The 

amount of work required to raise one 

pound vertically through a distance of a 

foot. 
Foot-Pound-per-Second.— (1) A unit of 

activity. (2) A rate-of-doing-work equal 

to the expenditure of one foot-pound per 

second. 
Foot-Switch. — A switch capable of being 

readily operated by the foot. 
Force. — Anything which changes or tends 

to change the condition of rest or motion 

in a body. 

Force, Electric. — The force exerted be- 
tween electrostatic charges. 

Force of Field. — The force in a magnetic 
or electric field independent of the im- 
pressed magnetic or electric force. 

Force of Flux.— The total magnetic or 
electric force in a magnetic or electric 
field, as distinguished from the impressed 
magnetic or electric forces or from the 
force of a field. 

Force Pump. — A pump provided with a 
solid piston, and employed for raising 
liquids through greater vertical heights 
than that through which such liquids 
could be raised directly by atmospheric 
pressure. 

Forced Electromagnetic Vibrations. 

Electro-magnetic vibrations that are set 
up in a system independently of its elec- 
tro-magnetic dimensions. 

Forced Vibrations.— A term employed 
for vibrations set up in a body independ- 
ently of its nature and form, and other 
than the free vibrations which the body 
would acquire, if disturbed and then left 
to itself. 

Forge, Electric— A forge in which the 
metal to be operated on is electrically 
heated. 

Fork for Trolley Wheel.— The mechan- 
ism which connects the trolley wheel to 
the trolley pole. 

Forked Circuits.— (1)A term used in teleg- 
raphy for a number of circuits that ra- 
diate from a given central point. (2) In 
telegraphy, a circuit which divides into 
two branches, thus connecting three ter- 
minal stations. 

Forked Lightning.— A variety of light- 
ning flash, in which the discharge, on 
meeting the earth or other object, divides 
into two or more branches. 

Form Factor of Alternating-Current 
Curve. — A factor equal to the square 

50 



root of the mean square divided by the true 
mean value of the alternating electro- 
motive force or current. 

Formal Inductance of Circuit.— That 
part of the counter-electromotive force of 
a circuit which depends on the form of 
the circuit. 

Formed Armature-Windings.— Arma- 
ture coils that are wrapped on a suitable 
form and afterwards placed on the arma- 
ture core. 

Formed Plates of Secondary Cell.— 
Plates that have been submitted to the 
forming process. 

Formers. — The forms employed in obtain- 
ing formed armature or other windings. 

Forming Block.— A block for holding the 
jack connections of a set or row in a mul- 
tiple telephone switchboard, for conveni- 
ence in soldering their contacts with cable 
conductors, before inserting the set in the 

.. switchboard panel. 

Forming Storage - Battery Plates. — 
Obtaining thick coatings of peroxide of 
lead and of spongy lead respectively, on 
the lead plates of a storage battery, by 
repeatedly sending the charging current 
between them in alternately opposite 
directions, while immersed in dilute sul 1 
phuric acid. 

Formulae. — Mathematical expressions for 
some general law, rule, or principle. 

Forward Induction. — An induction in 
the field of a motor or dynamo, in which 
the current in the armature coils produces 
an induction which assists the field, in 
contra-distinction to the back induction, 
which opposes the field. 

Forward Lead of Dynamo Brushes. — 

A displacement of the brushes on the 
commutator of a dynamo in the direction 
of rotation of the armature. 

Forward Pitch of Armature Winding. 
A pitch which is always directed right- 
handedly, or clockwise, when viewed from 
the commutator side. 

Forward Waves. — In a closed-current 
circuit supplied by a dynamo giving a 
harmonic-alternating electromotive force, 
the wave of induced potential that is as- 
sumed to travel through the circuit, from 
the positive pole of the dynamo to its 
negative pole. 

Foucault Currents.— (1) A name some- 
times applied to eddy currents, especially 
when in armature cores. (2) Useless cur- 
rents developed in a conducting mass, 
through which varying magnetic flux is 
moving. 



Fou.] 



786 



[Fre. 



Foucault Losses.— Losses of energy in a 
dynamo or motor, due to Foucault cur- 
rents. 

Foundation Trench.— A trench dug to 
receive the masonry employed in a foun- 
dation. 

Fountain, Electric. — A fountain oper- 
ated by electric motors, provided with a 
variety of jets that are electrically illu- 
mined by different colored lights. 

Fountain Projector. — An arc-light pro- 
jector employed in illumining the jets of 
an electric fountain. 

Four-Conductor Cord.— A flexible cord 
containing four separate insulated con- 
ductors. 

Four-Pole Switch.— (1) A switch em- 
ployed for making or breaking four con- 
tacts. (2) A switch employed to open or 
close a pair of diphase circuits. (3) A 
double double-pole switch for diphase cir- 
cuits, one double-pole switch being pro- 
vided for each circuit. • 

Fourier's Series. — A series of sines or of 
cosines of multiple arcs. 

Four-Piece Electro-Magnet. — An elec- 
tro-magnet constructed in four pieces ; 
namely, two cores, a yoke and an arma- 
ture. 

Four-Point Switch, — (1) A switch whose 
circuit can be completed through four 
points, either singly, or simultaneously. 
(2) A four-pole switch. 

Four-Pole Dynamo-Electric Machine. 

A dynamo-electric machine whose mag- 
netic field is produced by four magnet 
poles. 

Four-Speed Regulator.— A regulator 
provided with a motor by which four dif- 
ferent speeds can be obtained. 

Four-Way Splice-Box.— A splice-box 
provided with four ways or tubular con- 
duits. 

Four-Way Switch.— A four-point switch. 

Four - Wire Diphase - Circuit. — A di- 
phase circuit, employing four wires in 
contradistinction to a three-wire diphase 
circuit. 

Four- Wire System.— A system similar 
in its general arrangement to the three- 
wire system, in which three dynamos are 
connected to four wires or conductors. 

Four- Wire Transmission. — A system of 
electric transmission employing four con- 
ductors. 

Fourth State or Condition of Matter. 
The ultra-gaseous or radiant condition of 
matter. 



Fractional Distillation.— (1) A method 
adopted for the separation of two or more 
liquids in solution, by first raising the 
liquid to the boiling point of the most 
volatile liquid, and retaining that temper- 
ature until all that liquid is evaporated, 
and then raising the temperature to that 
of the next most volatile liquid, and so on 
throughout. (2) The successive separa- 
tion by distillation of liquids that volatil- 
ize at different temperatures. 

Fractional Electrolysis. — Successive 
electrolysis of different substances by 
gradually raising the E. M. F. 

Fracture of Cable. —A parting or rupt- 
ure of a submarine cable. 

Frame of Dynamo or Motor.— A dy- 
namo or motor frame. 

Franklinic Alternating E. M. F.'s. — 
Alternating - electromotive forces ob- 
tained by means of a f rictional or electro- 
static-induction machine. 

Franklinic Currents.— The currents pro- 
duced by a frictional or electrostatic-in- 
duction machine. 

Franklinic Electricity.— A term some- 
times employed in electro-therapeutics 
for the electricity produced by a frictional 
or electrostatic-induction machine. 

Franklinism.— A word sometimes em- 
ployed for franklinization. 

Franklinization.— A term employed in 
medical electricity for electrization by 
means of a frictional machine, as distin- 
guished from faradization or electrization 
by means of an induction-coil. 

Franklin's Kite.— The kite employed by 
Franklin in demonstrating the identity of 
lightning and electricity. 

Fraunhofer's Dark Lines.— Spaces in 
the otherwise continuous spectrum of the 
sun where certain frequencies are absent. 

Free Charge. — The condition of an elec- 
tric charge on a conductor isolated from 
other conductors. 

Free Ether. — A term sometimes em-- 
ployed for the ether that exists in the 
inter-planetary spaces, as distinguished 
from the inter-molecular or inter-atomic 
ether. 

Free Electricity.— (1) In the old double- 
fluid hypothesis, a term, employed for 
either the positive or the negative 
electricity when it is freed from the in- 
fluence of the other. (2) A term some- 
times employed for a charge on an insu- 
lated conductor that is isolated from 
other conductors. (3) A term sometimes 
employed for the electricity contained in 
a free charge. 



Fre.] 



787 



[Ful. 



Free Insulated. — The condition of a tele- 
graph wire when it is disconnected from 
its apparatus and left insulated. 

Free Magnet Pole. — A pole in a piece of 
iron or other paramagnetic substance 
which acts as if it existed as one magnetic 
pole only. 

Free Magnetism. — (1) In the theory of 
magnetic matter, magnetism resident 
upon the polar surface of a magnet and 
not neutralized by opposite polarity. (2) 
That portion of the imaginary magnetic 
matter of a magnet that is distributed 
over the surface of the magnet. 

Free Path. — That path of a gaseous mol- 
ecule in which it does not collide or strike 
against another molecule. 

Free Vibrations. — Vibrations dependent 
on the elasticity and shape of a body ac- 
quired when the body is acted on by a 
disturbing force and then left to itself. 

Freezing. — Congealing or assuming the 
solid state by loss of heat. 

Freezing Mixtures. — Various mixtures, 
such as salt and ice, which melt or dis- 
solve on being mixed, and thus absorb 
sensible heat from themselves, or from 
surrounding substances. 

Freezing of Shaft in Bearing.— The fix- 
ing of a shaft in its bearing by the lique- 
fication and subsequent cooling of its 
anti-friction metal. 

Freezing Point.— The point of congela- 
tion of a liquid. 

French Measures and Weights. — A 
system of measures and weights em- 
ployed generally in physical science, 
based on the metre as the unit of length, 
and the gramme as the unit of weight. 

French Standard Candle.— The bougie- 
decimale or the twentieth part of a Violle. 

Frequency of Alternation. — (1) The 
number of cycles or periods executed by 
an alternating current in unit time. 
(2) The periodicity. (3) The number of 
alternations or half-cycles executed by an 
alternating current in a second or in a 
minute. 

Frequency Setter. — In an alternating- 
current circuit having induction ma- 
chines, an alternator which supplies them 
with a definite frequency. 

Frequency Teller.— A device for deter- 
mining the frequency of an alternating 
current. 

Friable. — Easily crumbled or pulverized. 
Friction.— Resistance to the sliding or 
rolling motion of one body over another. 



Friction Brake. —(1) A Prony brake. 
(2) Any form of brake dependent for its 
operation on friction. 

Fringe of Lines of Force. — A term some- 
times used for fringe of magnetic field. 

Friction, Electric. — A term sometimes 
employed for electric resistance. 

Frictional Electric Machine.— A ma- 
chine for the development of electricity 
by friction. 

Frietiooal Electricity. — The electricity 
developed by friction. 

Frictional Torque. — (1) Torque developed 
by friction. (2) In a motor the torque 
necessary to exert on the armature in 
order to overcome its friction. 

Fringe of Magnetic Field.— The lateral 
extension or diffusion of magnetic flux 
from the edge of a pole piece whereby 
the field is not restricted to the space 
covered by the pole, but extends with 
diminishing intensity to a greater area. 

Frog. — (1) A metallic guide placed on one 
side of a single track, where a car has to 
be driven f rom one track to another, so as 
to guide the car in the required direction. 
(2) A grooved piece of metal, serving as 
a guide, at the intersection of two rails 
in a track-crossing. (3) A trolley frog. 

Front Door Pull.— A circuit-closing de- 
vice operated by a pull at a front. 

Front Stop of Key .—A stop placed on the 
front of a telegraphic key in order to re- 
strict its motion in a downward direction. 

Frost Alarm. — An electric alarm sounded 
or set in operation by means of a mechan- 
ism operated by a fall of temperature to 
or below the freezing point of water. 

Frying of Arc— The frying sound that 
accompanies a voltaic arc when the car- 
bons are too near together. 

Fulgurite.— A tube of vitrified sand be- 
lieved to be formed by a lightning dis- 
charge into the ground. 

Full Battery. — A complete battery em- 
ployed in the quadruplex system, as dis- 
tinguished from a reduced battery. 

Full Contact. — A complete contact. 

Full Load.— (1) An entire load. (2) The 
maximum load which a machine is de- 
signed to carry permanently. 

Full-Load Current. — The current of 
maximum load of a source or station. 

Full-Load Efficiency of Motor.— The 
efficiency of a motor when operating at 
full load": 

Full-Load Efficiency of Transformer. 
The efficiency of a transformer, or the 
ratio of the power yielded at secondary 



Eul.] 



788 



[Gal. 



terminals to the power absorbed at pri- 
mary terminals, when operating at full 
load. 

Pull Metallic -Contact. —A contact 
which, from its small resistance, estab- 
lishes a complete connection. 

Fuller "Voltaic Cell.— A zinc-carbon cou- 
ple immersed in a solution of electropoion 
liquid and provided with a layer of mer- 
cury around the lower part of the zinc. 

Fulminate. — A name given to a class of 
highly explosive compounds. 

Fundamental Frequency .—The nominal 
or lowest frequency of a complex har- 
monic electromotive force, flux or current. 

Fundamental Tone. — The lowest or dom- 
inant tone, or that on which the pitch of 
a musical note is dependent. 

Fundamental Units.— (1) The units of 
length, time, and mass, to which all other 
quantities can be referred. (2) Units of 
length, time, and mass, as distinguished 
from their derivations, or derived units. 

Furnace, Electric. — A furnace in which 
electrically generated heat is employed 
for effecting difficult fusions, for the 
extraction of metals from their ores, or 
for other metallurgical operations. 

Fuse Block. — A block containing a safety 
fuse or fuses. 

Fuse Board. — A board of slate, or other 
infusible material, on which the safety 



fuses in a given installation are assem- 
bled. 

Fuse Box. — (1) A box containing a safety 

fuse. (2) A box containing fuse wires. 
Fuse Carrier.— A fuse block. 

Fuse, Electric— (1) A device for elec- 
trically igniting a charge of powder, by 
the heat generated in a small strip, wire 
or mass of poorly conducting material. 
(2) A safety wire or catch. 

Fuse Holder.— A device for holding or 
protecting a safety fuse. 

Fuse Links.— Strips or plates of fusible 
metal in the form of links employed for 
safety fuses. 

Fuse Panel. — A panel in a switchboard 
provided for the support of safety fuses. 

Fuse Ribbons, Strips, or Wires.— Ma- 
terial for safety fuses in the form of rib- 
bons, strips, or wires. 

Fused Electrolytic Bath.— An electroly- 
tic bath in which the electrolyte is main- 
tained in a state of fusion during elec- 
trolysis by means of heat. 

Fusible Arrester.— A safety catch. 

Fusible Plug. — A term sometimes applied 
to a safety plug. 

Fusible Protector. — A safety fuse which 
acts as a line protector. 

Fusing Current. — A term sometimes ap- 
plied to the current which causes a fuse 
to blow or melt. 



Q 



g. — (1) An abbreviation or symbol for the 
gravitation constant, or the force with 
which the earth acts upon unit mass at any 
locality. (2) An abbreviation proposed for 
gramme, the unit of mass in physical in- 
vestigations. 

g. — In telegraphy, an abbreviation for " go 
ahead." 

g. cm 2 . — An abbreviation proposed for the 
gramme centimetre-squared, the centi- 
metre-gramme-second unit of moment of 
inertia. 

G. M. D. — A contraction for geometrical 
mean distance. 

G. M. T. — A contraction for Greenwich 
mean time, the standard time used in 
submarine telegraphy. 

G. P. — A contraction for gutta-percha. 

Gain Plate of Copper Voltameter.— The 
plate of a copper voltameter that increases 
in weight due to the deposition on it of 
metallic copper. 



Gains. — The spaces cut in the faces of tel- 
egraph poles for the support and placing 
of the cross arms. 

Galvanic Adapter. — An apparatus for 
obtaining from an electric light circuit 
feeble continuous currents such as are 
used in electro-therapeutic applications. 

Galvanic Arc. — A term sometimes used 
for a voltaic arc. (Not in general use.) 

Galvanic Battery. — An unadvisable term 
sometimes used in place of voltaic battery. 

Galvanic Cabinet.— A suitably shaped 
box provided with a voltaic battery and 
all the accessories necessary for its use in 
electro-therapy. 

Galvanic Cautery. — A term sometimes 
used in place of electric cautery. 

Galvanic Cell. — A name sometimes used 
in place of voltaic cell. 

Galvanic Chain. — A galvanic circuit. 



Gal.] 



789 



[Gal. 



Galvanic Circle. — A term sometimes used 
for galvanic circuit. 

Galvanic Circuit. — A name sometimes 
used for voltaic circuit. 

Galvanic Couple. — A name sometimes 
given to a voltaic couple. 

Galvanic Dosage. — A name sometimes 
given to electro-therapeutic dosage. 

Galvanic Electricity. — An unadvisable 
term sometimes used in place of voltaic 
electricity. 

Galvanic Etching. — A term sometimes 
used for electric engraving. 

Galvanic Excitability. — A term some- 
times used for electric excitability of nerv- 
ous or muscular fibre. 

Galvanic Induction. — A term sometimes 
used for voltaic induction. 

Galvanic Irritability. — Muscular con- 
tractions produced by the action of vol-; 
taic currents. 

Galvanic Multiplier. — A term formerly 
applied to a galvanometer. 

Galvanic Polarization.— A term some- 
times applied to the polarization of a vol- 
taic cell. 

Galvanic Ring. — A term sometimes ap- 
plied to a voltaic circuit. 

Galvanic Taste.— The sensation of taste 
produced when a voltaic current is passed 
through the tongue. 

Galvanism. — An inelegant term some- 
times employed to express the effects pro- 
duced by voltaic electricity. 

Galvanist.— One skilled in the art of gal- 
vanism. (Obsolete.) 

Galvanized.— (1) Subjected to the influ- 
ence of galvanism. (2) Covered with a 
coating of zinc by immersion in a bath of 
molten zinc. 

Galvanized Iron. — Iron coated with zinc. 

Galvanized Iron Wire. — A zinc-coated 
iron wire. 

Galvanizing. — (1) Covering iron with an 
adherent coating of zinc by dipping it 
in a bath of molten metal. (2) Subject- 
ing a nerve or muscle to the action of gal- 
vanism. 

Galvanizing Wire. — Covering wire with 
a coating of zinc by dipping it in a bath 
of molten metal. 

Galvano. — A word sometimes used in place 
of electro, either for an electro-type or for 
an article reproduced in copper by electro- 
metallurgy. 

Galvano-Caustic Loop. — (1) A loop of 
platinum wire suitably supported, so as to 
be shortened at will, and employed for re- 



moving diseased growths by drawing it, 
while heated to electric incandescence, 
through the parts to be removed. (2) An 
electric cautery. 

Galvano-Caustics. — A term sometimes 
employed for the destruction of diseased 
tissues by electrolysis. 

Galvano-Causty . — A term sometimes em- 
ployed for galvano-cautery. 

Galvano-Cautery. — An electric cautery. 

Galvano-Electric Cautery. — An electric 
cautery. 

Galvano-Faradization. — (1) In electro- 
therapeutics, the simultaneous excitation 
of a nerve or muscle, by both a voltaic and 
a faradic current. (2) A pulsating, con- 
tinuous current. 

Galvanoglyphy. — A word proposed for 
the process of producing an electro-type. 
(Not in use.) 

Galvanography .— The process of building 
up a picture in colored varnish, whose 
varying thickness gives the necessary gra- 
dations of light and shade ; subsequently 
black -leading the picture, and depositing 
a layer of copper by electro-plating, and 
employing the finished picture as an en- 
graved plate for printing. 

Galvano-Magnet. — A word sometimes 
used for electro-magnet. (Not in use.) 

Galvano-Magnetic— A word proposed 
for electro-magnetic. (Not in use.) 

Galvano-Magnetism.— A word proposed 
for electro-magnetism. (Not in use.) 

Galvanometer. — (1) An apparatus for 
measuring the strength of an electric 
current by the deflection of a magnetic 
needle. (2) A current measurer. 

Galvanometer Constant.— (1) The con- 
stant of calibration of the galvanometer 
scale. (2) The numerical factor connect- 
ing a current passing through a galvan- 
ometer with the deflection produced by- 
such current. (3) The value of one divi- 
sion of the galvanometer scale in terms of 
resistance or current strength. 

Galvanometer Shunt. — A shunt placed 
around a sensitive galvanometer in order 
to protect it from the effects of a strong 
current, or for reducing its sensibility. 

Galvanometer Switch.— A switch em- 
ployed with a dynamo balance-galvan- 
ometer. 

Galvanometer Voltmeter. — Any form 
of galvanometer arranged so as to readily 
measure a difference of potential. 

Galvanometric. — Of or pertaining to a 
galvanometer. 



Gal.] 



790 



[Gea. 



Galvanometrieal.— Of or pertaining to a 
galvanometer. 

Galvanometrically. — In the manner of a 
galvanometer. 

Galvanometry .— The determination of the 
current strength by means of a galvan- 
ometer. 

Galvano-Plastie Adhesion. — Adhesion 
to surfaces produced by a galvano-plastic 
deposit between them. 

Galvano-Plastie Bath. — A plating bath. 

Galvano-Plastie Matrix. — A mould in 
which a galvano-plastic deposit is made. 

Galvano-Plastie Soldering. — Uniting 
two metallic surfaces by a metallurgical 
deposit. 

Galvano-Plastics.— (1) A term some- 
times employed for electrotyping, or for 
producing an electrolytic deposit suffi- 
ciently thick to permit of its ready sep- 
aration from the object on which it has 
been deposited. (2) Literally, the cold 
moulding or shaping of metals by electro- 
typing. 

Galvano-Plasty. — Galvano-plastics. 

Galvano-Puneture.— A term sometimes 
used for electro-puncture. 

Galvanoseope. — (1) A galvanometer in- 
tended to show the existence of a current 
rather than to measure its strength. (1) 
A crude or simple form of galvanometer. 

Galvanoseopic Frog. — The hind legs of 
a recently killed frog, employed as an 
electroscope or galvanoseope, by sending 
electric currents from the nerves to the 
muscles. 

Galvano-Therapeutics. — An objection- 
able term sometimes employed for elec- 
tro-therapeutics. 

Galvano-Thermal Cautery — A term 
sometimes used for electric cautery. 

Galvanotonus. — A term proposed for the 
state of tetanus produced in a muscle 
that has been over-stimulated electrically. 

Galvanotropism. — Movements produced 
in living organisms by the passage of 
electricity through them. 

Gap Space. — The air-gap or entrefer. 

Gap Wire Gauge.— A form of wire gauge 
in which a gap or set of gaps is left in a 
plate of metal which may be bridged or 
rilled by the wire to be measured. 

Gas Battery. — A battery formed of gas 
cells. 

Gas-Burner, Electric.— An electric gas- 
burner that can be electrically turned on 
and lighted, or electrically lighted after 
it has been turned on by hand. 



Gas Cell. — A voltaic couple formed of 
metals in the presence of gases instead of 
solids as usual. 

Gas Engine. — An engine whose motive 
power is derived from the heat of burning 
gas. | 

Gas-Flame Photometric-Standard.— A 

gas-jet photometer. 

Gas- Jet Photometer. — A photometer in 
which the standard of light is a gas jet 
burning with or without a diaphragm at a 
definite height under standard conditions 
of volume and pressure. 

Gas-Lighting, Electric. — The electric 
ignition of a gas jet from a distance. 

Gas-Lighting Torch.— A gas-lighting ap- 
pliance, consisting of the combination of 
a portable voltaic battery and a spark 
coil. 

Gas Polarization. — A term sometimes 
employed for that form of polarization 
which is due to the collection of hydrogen 
gas on the negative plate of a voltaic 
cell. 

Gas Voltameter.— A voltameter whose 
indications are based on the volume of 
gas liberated at a fixed pressure and 
temperature. 

Gassing. — The evolution of gas from the 
plates of a secondary or storage battery. 

Gastroscope, Electric— An electric ap- 
paratus for the illumination and inspec- 
tion of the human stomach. 

Gastroscopy. — The examination of the 
stomach by the gastroscope. 

Gauge, Electric— Any form of portable 
galvanometer suitable for ordinary test- 
ing work. 

Gauss. — (1) The name proposed in 1894 by 
the American Institute of Electrical En- 
gineers for the C. G. S. unit of magnetic 
flux density. (2) A unit of intensity of 
magnetic flux, equal to oneC. G. S. unit 
of magnetic flux per-square-centimetre of 
area of normal cross-section. (3) A name 
proposed for the C. G. S. unit of magnetic 
potential or magnetomotive force by the 
British Association in 1895. 

Gaussage. — (1) The value of the magnetic 
intensity in gausses. (2) A name proposed 
for the value of the M. M. F. in gausses. 

Gauze Brushes for Dynamo or Motor. 

Dynamo or motor brushes formed of wire 

gauze, or of bundles of parallel plates 

of thin woven wire. 
Gear Clutch Arc-Lamp. — An arc-lamp 

provided with a gear clutch. 
Gearless Car Motor.— A motor whose 

speed is such as to permit it to be con- 



Gei.] 



791 



[Glo, 



nected directly, without intermediate 
gearing, on the car-wheel axle. 

G-eissler Mercurial Pump.— A mercurial 
air pump in which the exhaustion is ob- 
tained by the aid of a Torricellian vac- 
uum. 

G-eissler Tubes. — Glass tubes, provided 
with platinum electrodes passed through 
and fused into the glass, containing the 
residual atmospheres of gases at a com- 
paratively low vacuum, either with or 
without fluorescent liquids, or solids, or 
both, employed to obtain various luminous 
effects on the passage of electric dis- 
charges. 

General Alternating- Current Trans- 
former. — Any form of alternating-cur- 
rent apparatus in which secondaiy cur- 
rents are induced, such as an induction 
motor or induction generator, as well the 
ordinary transformer. 

General Faradization. — A method of 
employing the faradic current similar to 
its use in general galvanization. 

General Galvanization. — A method of 
employing an electric current therapeut- 
ically by the use of electrodes of suffi- 
cient size to direct the current practically 
through the entire body. 

Generator. — A dynamo-electric machine. 

Generator Ammeter. — An ammeter 
measuring the total current output of a 
generator. 

Generator Bus-Bars. — The bus-bars 
which receive the total generated pressure 
of a number of dynamos, or of a station. 

Generator Panels of Switchboard. — 
That panel or set of panels of a central - 
station switchboard which contains the 
generator bus-bars, and supports the gen- 
erator ammeters voltmeters and switches. 

Generator Switch. — A switch provided 
for the purpose of connecting or discon- 
necting a generator from the bus-bars. 

Generator Unit. — (1) A dynamo-electric 
generator in a central station. (2) One 
of a number of independent generating 
machines in a central station. 

Generator Voltmeter. — A voltmeter con- 
nected with the circuit of a generator, 
and employed to measure its pressure. 

Geographical Equator. — The great circle 
of the earth midway between its poles. 

Geographical Meridian. — Any great 

circle of the earth passing through its 

poles. 
Geomantic Lines of Force.— The lines 

of the earth's magnetic force. (Not in 

general use. ) 



German-Silver Alloy. — An alloy, em- 
ployed for the wires of resistance coils, 
usually consisting of fifty parts of copper, 
twenty-five of zinc and twenty-five of 
nickel. 

Gig, Electric— An electrically propelled 
gig- 

Gilb. — A name proposed for the gilbert. 

Gilbert.— (1) A name proposed for the C. 
G. S. unit of magnetomotive force. 
(2) A unit of magnetomotive force equal 
to that produced by — ^- 6 of one ampere- 
turn. 

Gilbertagc— The value of the magneto- 
motive force of a circuit expressed in 
gilberts. 

Gilding, Electric— Electro-plating with 

gold. 

Gilt Plumbago. — Powdered plumbago 
whose conducting power for electricity 
has been increased by electro- plating it 
with gold, used for rendering non-con- 
ducting surfaces electrically conducting. 

Gimbals.— Concentric rings of brass, sus- 
pended on pivots in a compass box, on 
which the compass is so supported, as to 
enable it to remain horizontal notwith- 
standing the movements of the ship. 

Girder Armature. — An armature with 
an H — or girder-shaped core. 

Girder Joint for Bail Bond.— A name 
given to a joint in steel rails consisting of 
two side-clamped girders supporting a tee- 
bar and double clamped. 

Glass-Bead Hydrometer.— A bead areo- 
meter. 

Glass Fuse. — A fuse contained in a glass 
tube with metallic ends. 

Glass Screw Insulator. — A glass in- 
sulator provided with an inside screw 
thread for attachment to the insulator 
pin. 

Globe Holder for Arc-Lamp.— A sup- 
port provided for holding the globe of an 
arc-lamp. 

Globe Net for Arc-Lamp.— A thin wire 
netting placed on the outside of an arc- 
light globe. 

Globe Strain - Insulators. — Insulators 
provided for the support of the strain 
wires in an overhead trolley system. 

Globular Lightning.— A rare form of 
lightning in which a globe of fire ap- 
pears quietly floating in the air for a 
while and then explodes with great vio- 
lence. 



Glo.] 



792 



[Gra. 



Glyphography. 

electro-type blo< 



Globular Spark. — An experimentally 
produced globular discharge obtained 
from a large condenser. 

Glow Discharge.— A form of convective 
discharge. 

Glow Illumination.— (1) A term pro- 
posed for an illumination similar to that 
of a glow-worm ; that is, luminous radia- 
tion unaccompanied by non-luminous 
radiation. (2) A term sometimes used 
for illumination by incandescent electric 
lamps. 

Glow-Lamp, Electric— (1) A lamp whose 
light is produced by glow illumination. 
(2) A term sometimes used for incandes- 
cent lamps. 

Glow-Worm Radiation.— (1) The radia- 
tion of the glow-worm or fire-fly. (2) Ra- 
diation that is practically confined 
within the limits of the visible spectrum. 

Glowing of Electric Conductor.— The 

incandescence of an electric conductor. 
Glue-Pot, Electric— An electrically heat- 
ed glue-pot. 

-The art of forming an 
•type block, whose impressions will 
produce relief outlines on a flat sur- 
face, by covering a flat copper plate 
with a suitable insulating material, cut- 
ting through the same until the copper is 
exposed, and then coating the surface 
with plumbago and electro-plating. 
Gnomon, Electric. — A term formerly ap- 
plied to a variety of pith-ball electro- 
meter. 

Gold Bath. — An electrolytic bath consist- 
ing of a readily electrolyzable solution of 
a gold salt, a gold plate acting as the 
anode and placed in the liquid opposite 
the object to be electroplated, which forms 
the cathode. 

Gold-Leaf Electroscope.— An electro- 
scope in which a pair of leaves of beaten 
gold is employed to detect the presence 
of an electric charge, or to determine its 
character, whether positive or negative. 

Gold-Plating.— Electroplating with gold. 
Gong Signalling for Railroads.— A 

system of railroad signals employing a 
code dependent on the sounds produced 
by gongs. 

Good Earth.— (1) Total or dead-earth. 
(2) An earth connection whose resistance 
is negligibly small. 

Goose-Neck Double-Pull-Off.— An in- 
sulator with a support shaped like a goose 
neck provided with two points for the 
attachment of the strain wires and em- 



ployed on curves to hold the trolley wire 
in position. 

Goose -Neck Pull -Off. —An insulator, 
with a support shaped like a goose neck, 
employed on curves to hold the trolley 
wire in position, and provided with a 
single point for the attachment of the 
strain wire. 

Governor, Electric. — A device for elec- 
trically controlling the speed of a steam 
engine, the direction of a current in a 
plating bath, the speed of an electric 
motor, the resistance of an electric cir- 
cuit, the flow of a liquid or gas into or 
from a containing vessel, or for other 
similar purposes. 

Graded Cyclic-Magnetization.— A reg- 
ularly expanding or contracting cylic 
magnetization. 

Graded Winding of Galvanometer.— 
A galvanometer winding composed of 
more than one size of insulated wire 
provided with a view to increasing the 
sensibility of the galvanometer, and in 
which the finest wire is placed nearest 
the axis of the coil. 

Gradient. — (1) The increase or decrease of 
an elevation or quantity with reference to 
some constant quantity. (2) The space- 
rate-of-change in a quantity. 

Gradient, Electric— (1) The rapidity of 
increase or decrease of the strength of an 
electromotive force or current. (2) The 
vector space-rate of descent of electric 
potential at any point. 

Graduators. — Devices, generally electro- 
magnetic, employed in systems of simul- 
taneous telegraphic and telephonic trans- 
mission over the same wire, so inserted 
in the line circuit as to gradually ob- 
tain the makes and breaks required in a 
system of telegraphic communication, 
so that they fail sensibly to influence the 
diaphragm of a telephone placed in the 
same circuit. 

Gramme. — (1) A unit of mass equal to 
15.43235 grains. (2) The mass of a cubic 
centimetre of water at the temperature 
of its maximum density. 

Gramme Armature - Winding. —The 
winding originally employed by Gramme 
on the armature of his dynamo-electric 
machine. 

Gramme Atom. — Such a number of 
grammes of any elementary substance 
as is numerically equal to the atomic 
weight of that substance. 

Gramme-Calorie. — (1) The amount of 
heat required to raise a gramme of water 
one degree Centigrade. (2) The gramme- 
degree-Centigrade. 



GraJ 



793 



[Gro. 



Gramme Equivalent. — Such a number 
of grammes of any substance as is nu- 
merically equal to the electro-chemical 
equivalent of that substance. 

Gramme Molecule. — A weight of any 
substance, taken in grammes, numerical- 
ly equal to its molecular weight. 

Gramme-Ring Transformer. — (1) A 
transformer whose primary and secondary 
coils are placed on a closed iron ring. (2) A 
transformer resembling a Gramme-ring 
armature. 

Gramaphone. — An apparatus for record- 
ing and reproducing articulate speech. 

Gramaphone Record. — A record of ar- 
ticulate speech obtained by means of a 
gramaphone. 

Granular - Carbon Telephone - Trans- 
mitter. — A dust telephone transmitter. 

Granular Telephone. — A word some- 
times used for a granular carbon tele- 
phone transmitter. 

Graphite. — A variety of soft carbon suit- 
able for writing on paper or on similar 
surfaces. 

Grapnel Toes. — The prongs of a grapnel 
employed in grappling for a submarine 
cable. 

Graphophone. — A form of apparatus for 
recording and reproducing articulate 
speech. 

Graphophone Record. — A record of ar- 
ticulate speech received on a graph- 
ophone. 

Grappling. — Recovering a sunken object, 
such as a cable, by means of a grapnel. 

Grapnel. — A device for hooking and re- 
covering a submerged object, such as a 
cable. 

Gratings. — A plate of glass or metal cov- 
ered with closely-ruled, parallel lines, 
employed for obtaining diffraction spec- 
tra. 

Gravitation. — Mutual attraction produced 
between two masses of matter by the 
force of gravity. 

Gravity. — The force which causes masses 
of matter to move or to tend to move 
towards one another. 

Gravity Ammeter. — A form of ammeter 
in which the magnetic needle is moved 
against the force of gravity by the mag- 
netic influence of the current it is measur- 
ing. 

Gravity Annunciator-Drop. — An an- 
nunciator drop which is operated by 
gravity under the influence of an electric 
current. 



Gravity-Drop Annunciator. — An an- 
nunciator whose signals are operated by 
the fall of a drop. 

Gravity-Feed Arc-Lamp. — An arc-lamp 
in which the upper or positive carbon is 
fed, or permitted to drop towards the 
negative carbon under the influence of 
gravity, on the operation of the feeding 
mechanism. 

Gravity Needle-Drop.— A needle annun- 
ciator furnished with a gravity drop. 

Gravity Voltaic Cell. —A blue-stone 
gravity cell. 

Gravity Voltmeter.— A form of volt- 
meter in which the potential difference 
is measured by the movement of a mag- 
netic needle against the pull of a weight. 

Grease-Spot Photometer.— (1) A translu- 
cent-disc photometer. (2) A Bunsen 
photometer. 

Greater Calorie. — The amount of heat 
required to raise the temperature of one 
kilogramme of water from 0° Centigrade 
to 1° Centigrade. 

Green Candle.— A standard candle em- 
ployed in connection with a screen of 
green glass in order more readily to com- 
pare the light of an arc with that of a 
standard candle. 

Grenet Voltaic Cell. — A name sometimes 
given to the bichromate cell. 

Grid Indicator.— (1) In telephony, a 
clearing indicator in which the armature 
is painted with alternate white and black 
horizontal stripes and fronted by a brass 
grid. (2) A form of telephone visual 
clearing indicator. 

Grid. — (1) A lead plate provided with per- 
forations or other irregularities of sur- 
face, and employed in storage cells for 
the support of the active material. 
(2) The support provided for the active 
material on the plate of a secondary or 
storage cell. 

Grid Plugs. — Plugs of active material, or 
of material that is readily rendered active 
by a charging current, inserted in the 
perforations of a grid for the purpose of 
decreasing the time required for the 
forming of the plates of a storage cell. 

Grip of Belt.— The hold of a belt on the 
driving pulley. 

Grothuss' Hypothesis. — A hypothesis 
proposed to account for the electrolytic 
phenomena that occur on closing the cir- 
cuit of a voltaic cell. 

Ground. — A general term for the earth 
when employed as a return conductor. 



Gro.] 



794 



[Gyr. 



Ground Circuit. — A circuit in which the 
ground forms part of the path through 
which the current passes. 

Ground Coil. — A small rheostat employed 
in duplex telegraphy at the home station , 
for the purpose of obtaining the balance 
of the line at that station. 

Ground Detector. — (1) In a system of in- 
candescent-lamp distribution, a device 
placed in a central station for indicating, 
by the brightness of a lamp, the existence 
of a ground on the system. (2) An instru- 
ment for detecting or measuring grounds 
or leaks. 

Ground Indicator.— (1) A tell-tale device 
employed on a line carrying a current, to 
' instantly indicate any fault in the insu- 
lation. (2) An apparatus for detecting a 
loss of insulation. 

Ground Plate of Lightning Arrester. 
— That plate of a comb lightning-arrester 
which is connected to the ground or earth. 

Ground-Return.— (1) A general term 
used to indicate the use of the ground or 
earth for part of an electric circuit. 
(2) The earth or ground which forms part 
of the return path of an electric circuit. 

Ground Shield of Transformer.— (1) A 

metallic plate or shield in a transformer 
separating the primary and secondary 
coils and connected to ground so as to 
protect the secondary circuit from any 
possibility of becoming crossed with the 
primary. (2) A cylinder of slotted copper 
placed between the primary and secon- 
dary windings of a transformer, so that 
there can be no accidental contact be- 
tween the high pressure and the low pres- 
sure circuits. 

Ground Wire. — The wire or conductor 

leading to or connected with the ground 

or earth in a grounded circuit. 
Grounded Circuit. — A 4 circuit, part of 

whose path is completed through the 

ground. 
Grounded Dynamo. — A dynamo whose 

circuit is accidentally or intentionally 

grounded. 

Grounding. — (1) A word sometimes em- 
ployed in electro-metallurgy for the pre- 
paratory process of burnishing. (2) Con- 
necting a circuit to earth or ground. 

Group Incandescent Switch.— A switch 
which governs a portion or group of the 
lamps on an electrolier, or in a room. 

Grouping System for Switchboard 
Circuits.- — A system of central-tele- 
phone-station distribution in which the 
subscribers are divided into a convenient 



number of groups, and each group given 
to the charge of a single operator. 

Growth of Lines of Force.— The expan- 
sion of lines of force. 

Grove's Voltaic Cell.— A zinc-platinum 
couple immersed respectively in electro- 
lytes of sulphuric and nitric acid. 

Guard Arm.— In telegraphic pole-setting, 
a short upright secured to a pole cross- 
arm so as to catch a wire should it become 
detached from the pole. 

Guard Ring of Electrometer or Con- 
denser. — A conducting ring constructed 
to form the annular extension of a plate 
or disc in an air-condenser, for the purpose 
of preventing any disturbance of electric 
flux-distribution at the edge of such disc 
or plate. 

Guard Suspension Wire.— In a trolley 
system, a wire supported on the tops 
of opposite poles for the suspension of a 
running guard wire, or guard-wires. 

Guard Wire. — A wire hung above any 
active conductor, such as a trolley wire, 
in order to prevent it from coining into 
electric contact with falling wires. 

Guard- Wire Hanger. — A hanger em- 
ployed for the suspension of a guard wire. 

Gutta-Percha. — A resinous gum obtained 
from a tropical tree, and valuable elec- 
trically for its high insulating powers and 
for its indestructibility when employed 
in submarine cables. 

Gutter of Insulator.— A channel on the 
side of an insulator, designed to carry off 
the rain water. 

Guy. — A rod, chain, rope or wire employed 
for supporting or stiffening any structure 
such as a telegraph pole. 

Guy-Rod Bands. — Bands by which a guy- 
rod is fastened to a pole. 

Guy Rods. — Metallic rods employed as 
guys. 

Guy Rope. — A rope employed as a guy. 
Guy Stubs. — (1) A stub or anchor to 

which a guy is secured. (2) The stub of 

a pole set in the earth at an angle away 

from the pole to be guyed. 
Guy Wire. — A wire employed as a guy. 
Guying. — Stiffening by means of guys. 
Guys. — Stays, suitably secured to a post or 

anchor, for the purpose of steadying an 

overhead wire system. 
Gymnoticus Electricus. — The electric 

eel. 
Gyration. — The act of turning around an 

axis. 
Gyrometer. — A rotary speed-indicator. 



Ayr.] 



795 



[Han. 



Gyroscope, Electric. — A gyroscope 
driven by an electro-magnetic motor. 

Gyrostat. — (1) A revolving flywheel de- 
signed to display gyrostatic action. (2) A 
flywheel possessing considerable moment 
of inertia, suitably supported on pivots 
within a case, so as to permit of being 
carried about, and employed to show the 



resistance which rotating bodies offer to 
changing their plane of rotation. 
Gyrostatic Action of Dynamo on Ship- 
board. — The action which occurs at the 
bearings of a dynamo running on board a 
tossing ship, whereby gyrostatic stresses 
are produced. 



H 



H. — A symbol for the horizontal intensity 
of the earth's magnetism. 

H. — A contraction for the henry or practi- 
cal unit of self induction. 

H. — A contraction for the magnetizing 
force that exists at any point ; or, gen- 
erally, for the intensity of magnetic 
force. 

H. — A symbol for field intensity. 

3-C. — A symbol proposed for magnetizing 
force. (Partly international usage.) 

h. — An abbreviation for hour, a practical 
unit of time. 

"H. B." Curves.— (1) Curves indicating 
the relations between magnetizing force 
and magnetic flux density in a magnetic 
substance. (2) A term sometimes em- 
ployed for magnetization curves. 

H.P. or gJ*C. — A contraction for horse- 
power. 

H.R. — A contraction for high resistance. 

H-Armature Core. — (1) An armature 
core in the shape of the letter H. (2) A 
girder, shuttle, or I-armature. 

H-Poles. — In telegraphy a pair of parallel 
vertical poles braced together to form one 
structure, resembling the letter H. 

Hematocrit, Electric. — An electrically 
driven device for separating the white 
blood corpuscles from the red corpuscles 
by centrifugal force. 

Half-Deflection Method.— A method of 
measuring an electromotive force, current 
or resistance, by adjusting the circuit in 
such a way as to halve the galvanometer 
deflection. 

Half-Gate. — The condition of a turbine 

when operating with the gate half open. 
Half-Hoop Magnet. — A magnet in the 

form of a semi-circle. 
Half-Load Efficiency.— The efficiency 

which a device possesses at half its full 

load. 

Half-Shade for Incandescent Lamp.— 
A reflecting shade whose outline conforms 



to that of the lamp chamber, and covers 
but half of its surface. 

Half- Wire Guard for Incandescent 
Lamp. — A wire guard which covers but 
half of an incandescent lamp. 

Hall Effect. — A transverse electromotive 
force produced by a magnetic field in 
substances undergoing electric displace- 
ment. 

Halleyan Lines. — A term sometimes used 
for isogonal lines. 

Halpine-Savage Torpedo. — A form of 
torpedo in which electricity is both the 
propelling and the directing power, and 
in which the electric source furnishing 
the propelling current is contained within 
the torpedo. 

Hand-Brake Mechanism.— A car brake 
operated by hand. 

Hand Dynamo Machines.— A hand gen- 
erator. 

Hand Generator.— (1) A hand-driven dy- 
namo. (2) A hand-driven telephone mag- 
neto generator. 

Hand-Hole of Conduit. — A box or open- 
ing, communicating with an underground 
cable, provided for readily tapping the 
cable, and of sufficient size to permit the 
introduction of the hand. 

Hand-Lighting Electric Burner.— A 
name sometimes applied to a plain pen- 
dant burner. 

Hand-Operated Alarm. — Any electric 
alarm operated by hand, as distinguished 
from an automatically operated electric 
alarm. 

Hand Regulation. — Any regulation of a 
dynamo effected by the hand, in contradis- 
tinction to automatic regulation, such as 
will preserve constant either the current 
or the potential. 

Hand Regulator. — A resistance box, 
whose separate coils can be readily placed 
in or removed from the circuit by means 
of a hand-operated switch. 

Hand Scratch-Brush.— A scratch brush 



Han.] 



796 



[Hea. 



operated by hand, as distinguished from 
one operated by means of a lathe. 

Hand-Signalling. — Telegraphic signal- 
ling by hand, as distinguished from auto- 
matic or machine signalling. 

Hand Telegraphic Transmission. — 
Manual telegraphic transmission. 

Hand Telephone.— (1) A telephone re- 
ceiver held in the hand, as distinguished 
from a head telephone receiver. (2) An 
ordinary telephone receiver. 

Hanger Board. — A form of board provided 
for the ready replacement or removal of 
an arc-lamp from a circuit. 

Hanger Cut- Out. — A cut-out switch for 
an arc lamp placed under a hanger. 

Hard-Drawn Copper Wire.— (1) Copper 
wire that is hardened by being drawn 
three or four times without annealing. 
(2) Copper wire not annealed after leaving 
the die. 

Hard Porous Cell. — A hard-baked porous 
cell, whose use in a voltaic cell renders 
its resistance comparatively high, but 
which is better able to stand the disinte- 
grating action arising from the crystalli- 
zation of saline substances present in the 
battery. 

Hardening. — Increasing the hardness of 
certain metals by heating them to a high 
temperature and then suddenly cooling. 

Hardness. — That property of a body in 
virtue of which it resists scratching or 
cutting. 

Harmonic Analyzer.— (1) A device for 
automatically resolving a complex har- 
monic into its simple-harmonic com- 
ponents. (2) A harmonic receiver. (3) A 
receiving instrument responding to a sin- 
gle harmonic frequency and which selects 
that frequency from a complex-harmonic 
current. 

Harmonic Capacity. — The capacity of a 
condenser to a charge or current received 
from a harmonically varying E. M. F. 

Harmonic Currents.— (1) Periodically al- 
ternating currents varying harmonically. 
(2) Currents which are harmonic functions 
of time. (3) Sinusoidal currents. 

Harmonic Electromotive Forces.— 
(1) Periodically alternating E. M. F.'s vary- 
ing harmonically ; or harmonic functions 
of time. (2) Sinusoidal E. M. F.'s. 

Harmonic Frequencies. — A series of 
frequencies whose values are integral 
multiples of the frequency of their 
fundamental. 

Harmonic Motion. — (1) Simple-harmonic 
motion. (2) Simple-periodic motion. 



Harmonic Receiver.— (1) The receiver em- 
ployed in systems of harmonic telegraphy, 
consisting of an electro-magnetic rod 
tuned to vibrate to a single note or rate 
only. (2) A receiver designed to respond 
to a single harmonic frequency in a com- 
plex-harmonic current. 

Harmonic Telegraph.— A general term 
embracing the apparatus employed in 
harmonic telegraphy. 

Harmonic Telegraphy. — (1) A system for 
the simultaneous transmission of a num- 
ber of separate and distinct musical 
sounds over a single wire, employed for 
simultaneously transmitting an equal 
number of telegraphic messages. (2) A 
system of telegraphy employing harmonic 
currents. 

Harmonic Vibrations. — The over-tones 
or higher vibrations into which a com- 
plex-periodic vibration may be resolved. 

Harmonies. — The higher component tones 
into which any complex tone can be re- 
solved. 

Harmonics, Electric. — Currents of higher 
frequencies into which any complex-har- 
monic current may be resolved. 

Harmonics of Current. — The harmonic 
currents into which a complex-harmonic 
current may be resolved. 

Harmonies of Sound Waves. — The over- 
tones or harmonics into which any com- 
plex tone may be resolved. 

Harmonograph. — A mechanical device 
for compounding any number of simple- 
harmonic motions of different amplitudes 
and phases. 

Harness. — (1) The head and breast equip- 
ment of an exchange operator. (2) A term 
used by telephonists. 

Harpoon, Electric. — A harpoon contain- 
ing a bomb that is electrically fired or 
exploded by the harpooner after the im- 
bedding of the harpoon. 

Harveyizing. — A method of superficially 
hardening a steel plate. 

Haulage, Electric. — Locomotion of a 
vessel or car by the agency of electricity. 

Head -Bath, Electric. — A variety of 
electric breeze applied therapeutically to 
the head of a patient. 

Head-Gear Telephone. — A telephone 
receiver held to the ear by means of a 
suitable head supporting-gear, thus leav- 
ing the hands of the operator free. 

Head-Board of Dynamo.— An insulating 
board of a dynamo-electric machine for 
the reception of terminals or switches. 

Head-Board of Motor.— A switchboard 



Hea.] 



797 



[HeL 



connected with a motor for use in start- 
ing it. 

Head Guy. — A guy attached to the top of 
a pole. 

0!ead Guying. — A method of pole guying 
for checking lateral vibrations, in which 
the top of each pole is guyed to the 
bottom of the next succeeding pole for 
a distance of several poles. 

Head-Lamp. — An electric lamp placed 
in the focus of a reflector supported on 
the head. 

Head-Light, Electric— An electric light 
placed in the focus of a parabolic reflector 
in front of an engine or car. 

Head of Liquid.— (1) The vertical distance 
from the level of a liquid in a containing 
vessel to the centre of gravity of an orifice 
placed therein. (2) Difference of liquid 
elevation or level. 

Head Receiver. — A head-gear telephone- 
receiver. 

Hearing Tubes. — Tubes connecting a 
telephone receiver with the ears of the 
listener. 

Heat. — (1) A form of energy. (2) A mode of 
motion. (3) A vibratory motion impressed 
on the molecules of matter by the action 
of any form of energy. (4) A wave mo- 
tion impressed on the universal ether by 
the action of some form of energy. 

Heat Alarm. — A temperature alarm. 

Heat Coil. — (1) A form of protector for 
switchboards or receptive apparatus gen- 
erally, consisting of a coil of fine German 
silver wire wrapped around a small me- 
tallic plug, held in its place by a drop of 
readily fusible solder, and so arranged 
that on the melting of the solder a spring 
is permitted to act so as to dead-ground 
the system. (2) A form of sneak-current 
arrester. 

Heat, Electric— The heat developed by 
the passage of an electric current through 
a conductor. 

Heat Insulator. — Any non-conductor of 
heat. 

Heat Lightning.— A variety of lightning 
flash unaccompanied by audible thunder, 
in which the disci large lights up the sur- 
faces of neighboring clouds. 

Heat Unit. — (1) The quantity of heat re- 
quired to raise a given mass of water 
through one degree of the thermo metric 
scale. (2) The calorie. 

Heat Units. — Units based on the quantity 
of heat required to raise a given mass of 
a substance, generally water, through 
one degree of the thermometric scale. 



Heater, Electric. — A device for the con- 
version of electricity into heat, employed 
for purposes of artificial heating. 

Heating Effects of Current.— The heat 
generated by the passage of an electric 
current through any circuit. 

Heavy Escape.— A term employed for a 
rapid loss of current on a telegraphic line, 
due to its accidental connection with the 
ground, as distinguished from a slight 
loss of current. 

Hedgehog Transformer or Converter. 
A name applied to a particular form of 
open-circuited iron-core transformer, in 
which a core of iron wire projects diver- 
gingly from each end of the coil. 

Heeling Error of Compass Needle. — 

The error in a ship's compass needle due 
to the induced and permanent magnet- 
ism of the ship in a vertical plane, which 
produces no influence upon the needle 
until the ship heels over, either under a 
press of canvas, or from any other cause. 

Hefher-Alteneck Amyl-Acetate Stan- 
dard. — (1) The amyl-acetate standard of 
luminous intensity. (2) A standard lamp 
of definite dimensions consuming amyl- 
acetate. 

H e f n e r- A lteneok Amyl-Acetate 
Lamp. — The lamp employed in the Hef- 
ner-Alteneck amyl-acetate standard. 

Heilmann Locomotive. — An electrically 
propelled locomotive which carries not 
only the steam plant necessary for the 
operation of the dynamo that furnishes 
its driving current, but also the motor 
propelling the truck. 

Hekto. — A prefix for one hundred. 
Hekto- Ampere. — One hundred amperes. 
Hekto-Ampere Balance. — A balance 

form of ammeter measuring hundreds of 

amperes. 
Hekto-Watt Hour.— (1) One hundred 

watt-hours. (2) A unit of work equal to 

one hundred watt-hours. 
Helical Coil. — A wire coil containing a 

number of convolutions or spirals. 

Heliograph. — (1) An instrument for tele- 
graphic communication, that operates by 
employing flashes of sunlight to repre- 
sent the dots and dashes of the Morse 
alphabet. (2) A portable instrument for 
visual telegraphic communication con- 
sisting essentially of a mirror supported so 
as to reflect a beam of sunlight to the dis- 
tant station, and means to intercept the 
beam at intervals corresponding to Morse 
code signals. 

Heliographic Transmission.— A system 



Hel.] 



798 



[Het. 



of telegraphic communication employing 
the heliograph. 

Heliography. — (1) A description of the 

. sun. (2) A term sometimes applied to the 
fixing of images in the camera obscura. 
(3) Transmitting or receiving telegraphic 
signals by means of the heliograph. 

Heliostat. — A mirror mounted on an axis 
parallel to the axis of the earth and so 
rotated by clock-work as to keep a beam 
of light reflected from its surface in a 
constant position, notwithstanding the 
rotation of the earth. 

Heliotropism. — A bending and twisting 
action produced on the growth of stalks 
and stems by their exposure to any source 
of light. 

Helix. — A word sometimes used in place 
of coil or solenoid. 

Helm Indicator. — An electrical indicator 
on board ship for indicating the position 

. at which the helm or rudder stands. 

Helmholtz's Galvanometer.— A double- 
ring tangent-galvanometer, whose two 
ring coils are parallel to each other, and 
so placed on opposite sides of the mag- 
netic needle that their magnetic field at 
the needle may be as nearly uniform as 
possible, and much more nearly uniform 
than a single-coil ring can produce. 

Hemihedral Crystal.— A crystal whose 
shape or form has been modified by the 
replacement of half of its edges or solid 
angles. 

Hemispherical Pole-Pieces. — Pole- 
pieces of a dynamo-electric machine that 
provide between them a spherical space 
for the revolution of an armature. 

Hen. — A word proposed for henry. (Not 
in use.) 

Henley's Quadrant Electroscope.— 

A form of swinging-pendulum electro- 
scope formerly employed for indicating 
powerful charges of electricity. 

Henry. — (1) The practical unit of self-in- 
duction. (2) An earth-quadrant, or 10 9 
centimetres. 

Henry's Coils. — A number of separate in- 
duction coils so connected that the cur- 
rents induced in the, secondar}' of the first 
coil, induce currents in the secondary of 
the second coil with whose primary it is 
connected in series, and so on throughout 
all the coils. 

Heptad Atom. — An atom whose valency, 
atomicity, or combining power, is seven. 

Hercules' Stone. — A name given by the 
ancients to the lodestone. 

Hermetical Seal. — A seal obtained in a 



glass vessel by the fusion of its walls, so 
as to enable it to hold either a vacuum or 
a pressure greater or less than that of the 
atmospheric pressure. 

Hertzian Waves.— (1) Electro-magnetic 
waves given off by an electro-magnet 
whose intensity is undergoing rapid pe- 
riodic variations, or by a current whose 
strength is undergoing rapid periodic 
variations. (2) Electro-magnetic waves 
given off from a circuit through which 
an oscillatory discharge is passing. 

Hertz's Axial Oscillator.— A term some- 
times employed for Hertz's linear oscil- 
lator. 

Hertz's Linear Oscillator.— A form of 
Hertz's oscillator in which a straight or 
linear conductor is employed instead of a 
plate as in the ordinary oscillator. 

Hertz's Oscillator.— A term sometimes 
employed for two insulated metallic 
plates to which are attached metallic 
rods, terminated by rounded poles or 
knobs, and separated by an air-gap or 
space through which disruptive dischar- 
ges pass. 

Hertzian Oscillations. — Hertzian waves. 

Heterochromatie Photometry. — (1) 
Photometric measurements made when 
the light chosen as a photometric standard 
emits rays whose frequencies differ from 
that of the light which is to be measured. 
(2) Photometry not restricted to light of 
one color as distinguished from mono- 
chromatic photometry. 

Heterogeneous Conductor.— (1) A con- 
ductor which does not possess the same 
power of electric conduction in all direc- 
tions. (2) A non-isotropic. conductor, or 
non-homogeneous conducting medium. 

Heterogeneous Dielectric. — A non- 
homogeneous dielectric, or one which 
possesses different powers of induction in 
different directions. 

Heteropolar Dynamo. — (1) A dynamo 
whose conductor moves successively past 
opposite magnet poles. (2) A bipolar or 
multipolar dynamo, as distinguished from 
a commutatorless dynamo. 

Heterostatic. — (1) 'Diveisely electrified. 
(2) A term employed to distinguish a form 
of electrometer in which the electrifica- 
tion is measured by determining the 
mutual influence of the attraction exerted 
by the charge to be measured, and the 
attraction of a fixed charge imparted to 
the instrument by a source independent 
of the charge to be measured. 

Heterostatic Electrometer.— (1) An 
electrometer in which the electrification 



Hex.] 



'99 



[Hig. 



to be measured is not. the only electrifica- 
tion employed. (2) An electrometer pro- 
vided with an independent charge. 

Hexad Atom. — An atom whose valency 
or atomicity is six. 

Hexode Working. — A term employed for 
a six- way mode of working by the Delany 
synchronous multiplex telegraph. 

Hick's Automatic Button Repeater.— 
A manual form of telegraphic repeater. 

High-Admittance Motor.— An alternat- 
ing-current induction motor characterized 
by high admittance. 

High Commutator Bars.— A term ap- 
plied to those commutator segments, or 
parts of commutator segments, which, 
through less wear, faulty construction, or 
looseness, are higher than the adjoining 
segments. 

High-Economy Lamp.— Any lamp of 
high efficiency. 

High Frequency. — Any frequency much 
higher than that ordinarily employed. 

High-Frequency Currents. — Currents 
produced by electromotive forces of high 
frequency. 

High-Frequency Induction Motor. — 
An induction motor operated by high- 
frequency currents. 

High - Frequency Transformer. — A 
transformer suitable for employment in 
connection with high-frequency electro- 
motive forces or pressures. 

High Insulation. — An unusually good in- 
sulation. 

High-Potential Current. — A term loose- 
ly applied for a current produced by high 
electromotive forces. 

High-Potential Insulator. — An insula- 
tor suitable for use on high-potential cir- 
cuits. 

High-Potential Push-Button.— A push 
button provided for safe use on a high- 
pressure system. 

High-Potential Switch.— A switch suit- 
able for use on high-pressure circuits. 

High-Potential System. — In the Na- 
tional Electric Code, any pressure of from 
300 to 3.000 volts. 

High-Potential Testing Transformer. 
An alternating-current transformer for 
obtaining from .an ordinary alternating- 
current circuit, a high alternating pres- 
sure suitable for testing insulation. 

High-Potential Wires. — Circuit wires 
provided with high insulation, and, there- 
fore, suitable for connection with high- 
potential sources. 



High Resistance.— A resistance for any 
circuit or apparatus, much higher than 
that ordinarily employed on such circuit 
or apparatus. 

High-Resistance Arrester.— A form of 
lightning arrester consisting of a number 
of thin metallic plates separated from one 
another by means of thin sheets of mica, 
or other refractory insulating substance. 

High-Resistance Magnet.— A term some- 
times used for a long-coil magnet of fine 
wire, possessing a high electric resistance. 

High-Resistance Telephone.— A tele- 
phone having an unusually high resist- 
ance. 

High-Pressure Incandescent Lamp. — 
An incandescent lamp provided with 
long, thin filaments whose electric resist- 
ance is high, and which, therefore, re- 
quires a comparatively high pressure for 
its operation. 

High-Reactance Motor.— An alternating- 
current induction motor possessing com- 
paratively high primary reactance. 

High-Speed Electric Motor.— (1) An or- 
dinary electric motor, as distinguished 
from a motor designed to run at a slow 
speed. (2) A motor which has its greatest 
efficiency when running at high speed. 

High-Susceptance Motor. — An alter- 
nating-current motor possessing compara- 
tively high susceptance. 

High-Tension Accumulator.— An ac- 
cumulator consisting of a number of 
series-connected secondary cells. 

High-Tension Bus. — A bus-bar supplied 
by a high pressure. 

High-Tension Cable. — A cable possessing 
high insulation and, therefore, suitable 
for bearing high electric pressures. 

High-Tension Circuit.— A circuit em- 
ployed in connection with high electric 
pressures. 

High-Tension Fuse.— A fuse for igniting 
an explosive, that is operated by the 
heating power of an electric discharge of 
high tension. 

High-Tension Switch.— A switch suit- 
able for use in high-tension circuits. 

High Vacuum. — (1) A space from which 
nearly all traces of air or residual gas have 
been removed, as distinguished from a low 
or imperfect vacuum. (2) Such a vacuum 
that the length of the mean free-path of 
the molecules of the residual atmosphere 
is equal to or exceeds the dimensions of the 
containing vessel. (3) A nearly perfect 
vacuum. 

High- Voltage Electro-Magnetic Gen- 



Hig.] 



800 



[Hor. 



erator. — An electro-magnetic generator 
arranged so as to produce a high electro- 
motive force. 

High- Voltage Incandescent Lamps. — 
Incandescent lamps constructed for more 
than the usual pressure ; usually lamps for 
more than 120 volts. 

Hissing Arc. — A voltaic arc that emits a 
hissing sound, due to its carbons being 
too near together. 

" Hitching Up." — A term sometimes em- 
ployed for boosting. 

Hittorf Effect.— The effect produced by a 
Hittorf tube. 

Hittorf Rays.— The rays emitted by a 
Hittorf tube. 

Hittorf Tubes.— Various forms of high- 
vacuum tubes employed by Hittorf in his 
researches in electrical discharges through 
high vacua. 

Hold-Off Spring. — A spring which acts to 
keep one thing away from another, in op- 
position to some force tending to keep it 
in contact with such thing. 

Hold-On Spring.— A spring which acts to 
keep one thing against or in contact with 
another, in opposition to some force tend- 
ing to pull it away from such thing. 

Holder for Incandescent Lamp.— An 
incandescent lamp-socket. 

Holder for Safety Fuse.— A support, 
generally of porcelain or other infusible 
material, employed for holding a safety 
fuse and for catching the metal when 
fused. 

Holders for Brushes of Dynamo-Elec- 
tric Machine. — Devices for holding the 
collecting brushes of a dynamo-electric 
machine. 

Holohedral Crystal. — A crystal whose 
shape or form has been modified by the 
replacement of all its edges or solid an- 
gles. 

Holophane. — A form of glass globe or 
enclosing chamber for a source of light, 
which has its external surface cast into 
lenticular ridges for the more general 
diffusion of the emerging light. 

Holophotometer. — A photometer based 
on the employment of a Bunsen screen 
with a system of mirrors, so combined as 
to avoid errors due to the movements 
which the lights undergo while being- 
compared. 

Holtz Influence Machine.— A particular 
form of electrostatic influence machine. 

Home Battery. — The battery in a sending 
station on a telegraphic line, as distin- 
guished from a distant battery. 



Home Station. — The near or sending sta- 
tion on a telegraphic line, as distinguished 
from a distant or receiving station. 

Homogeneous Conductor.— A c o n - 
ductor possessing the same resistivity 
throughout its length. 

Homogeneous Current-Distribution. — 

Such a distribution of current through a 
conductor in which there is an equal 
density of current in all parts of a nor- 
mal cross-section of the conductor. 

Homogeneous Dielectric— (1) A die- 
lectric possessing similar properties in all 
directions. (2) A uniform dielectric. 

Homogeneous Light.— (1) A light con- 
sisting practically of but a single fre- 
quency. (2) Monochromatic light. 

Homopolar Dynamo.— (1) A dynamo 
whose conductor moves continuously past 
poles of one polarity only. (2) A com- 
mutatorless dynamo. (3) A so-called 
unipolar dynamo. 

Hood for Arc Lamp.— A hood provided 
for the double purpose of protecting the 
body of an arc lamp from the weather, 
and for throwing its light in a downward 
direction. 

Hood Suspension for Arc Lamp.— A 

suspension of an arc lamp from a hanger- 
board placed inside a suitably supported 
hood. 

Hop System of Space Relations.— A 
system of space relations, employed 
by some electrical writers, which fol- 
lows the hop tendril : i. e., which consid- 
ers advance accompanied by left-hand ro- 
tation as positive ; or that a rotation is 
positive when accompanied by transla- 
tion in the manner of a female screw ; or, 
that clockwise rotation is positive when 
viewed from the front of the clock. 

Horizontal Candle Power. — (1) The 
intensity of light emitted by any source 
in a horizontal direction. (2) The lumin- 
ous intensity of a source taken in a hori- 
zontal direction, as measured in units of 
luminous intensity. 

Horizontal Component. — That portion 
of a force which acts in a horizontal 
direction. 

Horizontal Component of Earth's Mag- 
netism. — (1) That portion of the earth's 
directive force which acts in a horizontal 
direction. (2) That portion of the earth's 
magnetic force which acts to produce 
motion in a compass needle free to move 
in a horizontal plane only. 

Horizontal Force of Needle.— The hori- 
zontal component of the earth's magnetic 
force or magnetism. 



Hor 



801 



[Hug, 



Horizontal Intensity of Earth's Mag- 
netism. — (1) The horizontal component 
of the earth's magnetic intensity at any 
point. (2) The earth's horizontal mag- 
netic force upon a unit magnetic pole. 

Horizontal Intensity of Light.— (1) The 
intensity of a light measured in a horizon- 
tal direction. (2) The flux of a light con- 
tained in a small horizontal beam issuing 
from a source, divided by the solid angle 
of the beam. 

Horizontal Slit Photometer. — A form of 
spectro-photometer whose slit is horizon- 
tal, lying in a straight line joining the 
sources of light. 

Horns of Pole-Pieces of Dynamo.— 

(1) The edges or terminals of the pole-pieces , 
of a dynamo towards or from which the 
armature is carried during its rotation. 

(2) The following or leading horns of the 
pole-pieces of a dynamo. 

Horology, Electric. — That branch of 
electric science which treats of the appli- 
cation of electricity to the regulation and 
operation of electric clocks. 

Horse. — A support for a dynamo-armature 
in the process of winding it. 

Horseless Carriage. — An automobile car- 
riage. 

Horse-Power. — (1) A commercial unit of 
power, activity, or rate-of-doing-work. 
(2) A rate-of-doing-work equal to 33,000 
pounds raised one foot-per-minute, or 550 
pounds raised one foot-per-second. (3) A 
rate-of-doing-work equal to 4.562 kilo- 
grams raised one metre per minute. 

Horse-Power, Electric— Such a rate-of- 
doing electrical work as is equal to 746 
watts, or 746 volt-coulombs per second. 

Horse-Power-Hour.— (1) A unit of work 
equal to the work done by one horse- 
power acting for an hour. (2) 1,980,000 
foot-pounds. 

Horseshoe Electro-Magnet.— An elec- 
tro-magnet whose core has the shape of a 
horseshoe, or the letter U. 

Horseshoe Magnet.— A magnetized bar of 
steel or hardened iron, bent in the form 
of a horseshoe, or letter U. 

Hot Saint Elmo's Fire. — A term proposed 
by Tesla for a form of flaming brush-dis- 
charge between the secondary terminals 
of a high-frequency, high-potential induc- 
tion coil. 

Hot - Wire Ammeter. — An ammeter 
whose readings are based on the expan- 
sion of a wire due to an increase of tem- 
perature, by the passage through it of 
the current that is to be measured. 

51 



Hot- Wire Thermometer. — A thermom- 
eter whose indications are dependent on 
the expansion of a bi-metallic wire or 
spiral. 

Hot - Wire Voltmeter. — A voltmeter 
whose indications are based on the in- 
crease in the length of a metallic wire 
placed in the circuit of the electromotive 
force that is to be measured. 

Hotel Annunciator. — An annunciator 
connected with the different rooms of a 
hotel. 

House Annunciator.— An annunciator 
connected with the different rooms of a 
house. 

House Mains. — The conductors connect- 
ing the service wires with the street 
mams, in a system of multiple-incandes- 
cent lamp distribution. 

House Regulator. — An alternating-cur- 
rent apparatus foi insertion in the circuit 
of a group of lamps in a house for the 
purpose of controlling the candle-power 
of that group. 

House-Service Conductor.— In a system 
of multiple-incandescent lamp distribu- 
tion, that portion of the service wire 
which is included between the street 
mains and the cut-out within the house. 

House Telephone System.— (1) A do- 
mestic telephone system. (2) A system 
for establishing telegraphic communica- 
tion between different places in a house. 

House Wiring. — The wiring in a house 
for distributing electric currents therein. 

House Wires. — The circuit wires em- 
ployed in a house in a system of distribu- 
tion. 

Howler. — A term sometimes used for a 
loud buzzer. 

Hughes' Electro-Magnet.— (1) An elec- 
tro-magnet in which a U-shaped perma- 
nent magnet is provided with pole-pieces 
of cast iron on which only are placed the 
magnetizing coils. (2) A quick-acting 
electro-magnet whose magnetizing coils 
are placed on soft-iron pole-pieces that are 
connected with and form the prolonga- 
tion of the pole-pieces of a permanent 
horseshoe magnet. 

Hughes' Induction-Balance.— An ap- 
paratus for the detection of the presence 
of a metallic conducting substance in the 
body by the aid of induced electric cur- 
rents. 

Hughes' Theory of Magnetism.— A 
theory proposed to account for the phe- 
nomena of magnetism by the presence of 
originally magnetized particles or mole- 
cules. 



Hum. 



802 



[Hys. 



Hummer, Electric. — A word sometimes 
employed for an electric buzzer. 

Hunning's Transmitter. — The original 
form of dust telephone transmitter. 

Hunting of Parallel-Connected Alter- 
nators. — (1) Aperiodic increase and de- 
crease in the speed of alternators, when 
running under certain conditions in paral- 
lel connection as motors or dynamos. (2) 
Imperfect synchronous running. 

Hydraulic Gradient.— (1) The gradient 
representing the drop of pressure between 
the surface of a liquid in a containing 
vessel and a discharging orifice connected 
therewith. (2) The rate-of-drop of pres- 
sure in a hydraulic system of distribution. 

Hydraulic Power Dynamometer. — 
Any dynamometer suitable for measuring 
hydraulic power. 

Hydraulic Storage.— A method of 
storage of energy consisting in forcing 
water into elevated reservoirs. 

Hydraulic Transmission.— The trans- 
mission of power by means of pipes con- 
taining water under pressure. 

Hydraulics. — That branch of science 
which treats of the transmission of water 
througli pipes and the apparatus required 
for raising or moving water. 

Hydro-Carbon Treatment of Fila- 
ments. — Treatment of incandescent lamp 
filaments by means of the flashing pro- 
cess. 

Hydro-Dynamics. — That branch of nat- 
ural philosophy which treats of the con- 
ditions of rest and motion in fluid bodies. 

Hydro-Electric Bath. — An electro-thera- 
peutic bath in which one electrode is ap- 
plied to the metallic lining of the bath 
tub, and the other to the body of the pa- 
tient. 

Hydro-Electric Generator.— A term 
sometimes used for voltaic battery. 

Hydro-Electric Machine.— A term 
sometimes used for a machine in which 
electricity is developed by the friction of 
a jet of steam over a water surface. 

Hydro-Electro-Therapeutics. — Cura- 
tive processes combining electro-pathic 
and electro-therapeutic treatment. 

Hydrogen Voltmeter.— A voltmeter 
whose indications are based on the quan- 
tity of hydrogen evolved under a constant 
pressure and temperature. 

Hydro-Generator, Electric— An appa- 
ratus for the electrical development of 
the nascent hydrogen employed in the 
electrical rectification of alcohol. 

Hygrometer. — (1) An apparatus for de- 



termining the specific gravity of liquids. 
(2) An areometer. 

Hydrometric Telegraph.— A form of in- 
strument by means of which signals are 
transmitted by means of water pressure. 

Hydro-Plastics. — The art of electrically 
shaping or depositing metals in the wet, 
by electro-plating. 

Hydro-Plasty. — The art of hydro-plastics. 

Hydro-Platinum Rheostat.— A water 
rheostat furnished with platinum elec- 
trodes. 

Hydrostatic Wire-Testing Machine. 
A machine, operated by hydraulic pres- 
sure, for testing the tensile strength of 
wires. 

Hydrotasimeter, Electric. — An elec- 
trically operated apparatus designed to 
show at a distance the exact position of 
any water level. 

Hydrometer. — An apparatus for deter- 
mining the amount of moisture present 
in the atmosphere. 

Hydrometrical. — Of or pertaining to a 
hygrometer. 

Hydrometrically. — In the manner of a 
hygrometer. 

Hyperphosphorescence.— (1) A name 
applied to a variety of phosphorescence in 
which, after due stimulus, the body ex- 
hibits a persistent emission of invisible 
rays, not included in the hitherto recog- 
nized spectrum. (2) A phosphorescence 
accompanied by the emission of the 
Becquerel rays. 

Hypothesis. — A provisional assumption of 
facts or causes, the real nature of which 
is still unknown, for the purpose of study- 
ing their effects. 

Hypothetical. — Of or pertaining to a hy- 
pothesis. 

Hypsometer.— (1) An apparatus for deter- 
mining the height of a mountain or other 
elevation by ascertaining the temperature 
at which water boils on such elevation. 
(2) a hydro-barometer. 

Hypsometrical. — Of or pertaining to a 

hypsometer. 
Hypsometrically.— In the manner of a 

hypsometer. 

Hysteresial Dissipation of Energy. — 

The dissipation of energy by means of 
hysteresis. 
Hysteresis. — (1) A lagging behind of 
magnetization relatively to magnetizing 
force. (2) Apparent molecular friction 
due to magnetic changes of stress. (3) A 
retardation of the magnetizing or demag- 
netizing effects as regards the causes 



Hys.] 



803 



[Ice, 



which produce them. (4) That quality 
of a paramagnetic substance by virtue of 
which energy is dissipated on the reversal 
of its magnetization. 

Hysteresis Coefficient. — (1) The hystere- 
tic coefficient. (2) The energy dissipated 
in a cubic centimetre of magnetic ma- 
terial by a single cyclic reversal of unit 
magnetic density. 

Hysteresis Conductance. — The effec- 
tive conductance in a transformer or 
condenser due to the effects of hysteresis. 

Hysteretetic Constant.— The hysteretic 
coefficient. 

Hysteresis Loop.— The looped curve 
which forms tbe outlines of the graphic- 
ally represented hysteretic cycle to rec- 
tangular co-ordinates of magnetizing 
force and magnetic intensity or magneti- 
zation. (2) A cyclic magnetization curve, 
forming a closed loop. 

Hysteresis Losses. — Losses of useful 
energy due to hysteresis. 

Hysteresis Measurer. — An apparatus 
for conveniently estimating or measuring 
the hysteretic coefficient of a magnetic 
material. 

Hysteresis Meter.— A hysteresis meas- 
urer. 

Hysteresis Tester. — A hysteresis meas- 
urer. 

Hysteretic Activity. — Activity expended 
in producing hysteretic effects. 

Hysteretic Coefficient. — The activity in 
watts which would be expended in one 
cubic centimetre of a metal when magnet- 
ized and demagnetized to a flux density 
of one gauss at one complete cycle or 
double-reversal per second. 



Hysteretic Condensance.— In a con- 
- denser traversed by an alternating 
current, the apparent reactance of the 
condenser, due to or modified by hyster- 
esis. 

Hysteretic Conductance. — In a con- 
denser traversed by an alternating cur- 
rent, the apparent conductance of tbe 
condenser, due to or modified by hyster- 
esis. 

Hysteretic Cycle. — A cycle of complete 
magnetization and reversal. 

Hysteretic Energy Current. — The com- 
ponent of current in phase with the im- 
pressed E. M. F. at the primary terminals 
of a transformer representing the power 
expended in hysteresis. (2) The energy 
component of the exciting current of a 
transformer. 

Hysteretic Energy Electromotive 
Force. — The energy component of the 
E. M. F. of excitation in a transformer. 

Hysteretic Lag.— The lag in the magnet- 
ization of a transformer due to hysteresis. 

Hysteretic Resistance. — In a condenser 
traversed by an alternating current, the 
apparent resistance of tbe condenser due 
to or modified by hysteresis. 

Hysteretic Susceptance.— In a con- 
denser traversed by an alternating cur- 
rent, the apparent susceptance of the 
condenser, due to or modified by hys- 
teresis. 

Hysteretic Torque. — That portion of the 
torque of a dynamo-electric machine due 
to the influence of hysteresis, whereby 
mechanical work must be expended in de- 
veloping hysteretic energy as heat in the 
iron undergoing magnetic reversal. 



I. — (1) A symbol for strength of current. 
(2) A symbol for intensity of magneti- 
zation. 

9. — A symbol for intensity of magneti- 
zation. (Partly international usage.) 

I. H. P. — A contraction for indicated horse- 
power. 

I. I. — In telegraphy, a signal serving to 
separate the text of a message from tbe 
signature, or the name of the sender. 

I. R. — A contraction for India rubber. 

I. R. — A contraction sometimes employed 
for the drop in an electric circuit, equal to 
the product of tbe current in amperes by 
the resistance in ohms. 



I. S. W. G-. — A contraction for Imperial 

standard wire gauge. 
I. W. G. — A contraction for Indian wire 

gauge. 

I. 2 R. Activity.— (1) The activity expended 
in a circuit, equal to the square of the 
current strength in amperes by tbe resist- 
ance in ohms. (2) The C 2 K. activity. 

I. 2 R. Loss. — (1) Tbe loss of power in any 
circuit equal to tbe square of the current 
in amperes by the resistance in ohms. 
(2) The C 2 R. loss. 

I- Armature. — An I, or H-shaped armature. 
Ice Clearer for Trolleys. — A trolley 



Me.] 



804 



[Inini, 



wheel designed to remove aggregations of 
ice from a trolley-wire. 

Ideal Solenoid. — A solenoid consisting of 
a cylinder built up of a number of true 
circular currents, all independent of one 
another, and all of whose faces of like 
polarity are similarly directed. 

Identical-Electrode Cell.— A term some- 
times employed for a double-fluid voltaic 
cell, both of whose electrodes are formed 
of the same metal, and whose electro- 
motive forces are dependent on the col- 
lection of unlike ions around such plates. 

Idio-Electrics. — A term formerly applied 
to such bodies as amber, resin, or glass, 
which are readily electrified by friction, 
and which were then supposed to be elec- 
tric in themselves. (Obsolete.) 

Idiostatic. — Possessing one kind of elec- 
trification only. 

Idiostatic Electrometer.— An electro- 
meter in which the electrification is whol- 
ly due to the potential difference to be 
measured, as distinguished from a heter- 
ostatic electrometer, in which an auxiliary 
charge is employed from an independent 
source. 

Idle Coil. — (1) Any coil through which 
for the time no current is passing. (2) 
Any coil which is not passing through 
a magnetic field or generating an E. M. F. 

Idle Current. — A wattless current. 

Idle Current of Alternating-Current 
Dynamo. — The wattless current of an 
alternating-current circuit, as distin- 
guished from the active or working cur- 
rent. 

Idle Plug. — In a telephone switchboard, a 
plug not in use. 

Idle Poles. — Foles or electrodes in Crookes' 
tubes between which no discharge is tak- 
ing place. 

Idle Wire. — (1) Any wire through which 
either no current at all, or no useful cur- 
rent, is passing. (2) Any open-circuited 
armature wire not generating an E. M. F. 

Idle- Wire of Armature.— A term some- 
times employed in place of dead wire. 

Idle Wiro of Armature of Dynamo.— 
(1) That part of the wire on a dynamo 
armature "a which no useful electro- 
motive force is produced. (2) The dead 
wire of ar armature. 

Idle-Wire of Armature of Motor.— 
That part of the wire on the armature of 
a motor in which the field produced by 
the driving current exercises no useful 
action in driving the motor, since no 
counter-electromotive force is generated 
in it. 



Igniter. — A carbonaceous material placed 
between the free ends of a Jablochkoff 
candle, which becomes incandescent on 
the passage of the current and so enables 
the arc to be formed. 

Ignition, Electric. — The explosion of a 
powder, or the lighting of a combustible 
substance, by electrically generated heat. 

Illuminant. — Any source of light. 

Illuminated. — A somewhat inelegant or- 
thography for illumined. 

Illuminated Dial Instrument.— An in- 
strument for engine-room or central- 
station use, provided with a translucent 
dial illumined from the back to render 
the position of the pointer visible at a 
great distance. 

Illuminating Power.— The amount of 
illumination produced by any luminous 
source. 

Illumination.— The quantity of light re- 
ceived on a surface per-unit-of-area, 
either directly from a luminous source or 
indirectly by reflection and diffusion from 
surrounding objects. 

Illumined. — Lighted up or rendered vis- 
ible by means of light. 

Illumined-Dial Measuring Instru- 
ment. — A name applied to any electri- 
cal measuring instrument whose dial is 
so illumined that its scale divisions can be 
readily seen at a distance. 

Illumined Electrode.— That electrode of 
a selenium cell which on exposure to 
light develops an E. M. F. 

Illuminometer. — An instrument for 
measuring the illumination of a surface. 

Image. — The picture of an object formed 
by rays from its several points, brought 
or focused by any suitable means, either 
on the retina, or on a screen, so as to per- 
mit the image to become visible. 

Image, Electric— (1) A term sometimes 
applied to the charge produced on a 
neighboring surface by induction from a 
known charge. (2) An electrified point, 
or system of points, on one side of a sur- 
face, which would produce on the other 
side of that surface the same electrical 
action that the actual electrification of 
the surface really produces. 

Imbibition Currents. — Currents pro- 
duced in tissues by the imbibition or 
absorption of a fluid. 

Immediate False Zero.— A term em- 
ployed in "Wheatstone-bridge measure- 
ments in an observation made with ref- 
erence to that position of the galvano- 
meter needle, as zero, which is assumed, 



Imm.] 



805 



[Imp. 



or which tends to be assumed, immedi- 
ately after the application of the testing 
E. M. F. 

Immersion Front of Microscopic Ob- 
ject Glass. — That front of a high-power 
or immersion objective, to which the 
object is attached by a drop of transpar- 
ent liquid. 

Immersion G-ilding. — A gilding or elec- 
tro-plating obtained by a process of sim- 
ple immersion in a suitable solution of 
gold. 

Immersion Objective. — An object glass 
of high magnifying power. 

Impact. — A shock or collision caused by 
the meeting of two bodies when one or 
both are in motion. 

Impedance. — (1) Generally, opposition to 
current flow. (2) The sum of the ohmic 
resistance, and the spurious resistance of 
a circuit, measured in ohms. (3) In a 
simple-harmonic current circuit the 
square root of the sum of the squares of 
the resistance and reactance. (4) The 
apparent resistance of a circuit contain- 
ing both resistance and reactance. 

Impedance Circuit. — A circuit contain- 
ing impedance. 

Impedance Coils.— A term sometimes 
applied to choking coils, reactance coils, 
or economy coils. 

Impedance Factor.— The ratio of the im- 
pedance of a conductor or circuit to its 
ohmic resistance. 

Impedance Rush.— (1) The rush of cur- 
rent produced on closing an inductive 
circuit. (2) An impulsive current rush. 

Impediment.— A term proposed for the 
apparent resistance of a circuit contain- 
ing resistance, self-induction, and capac- 
ity. 

Impenetrability. — That property which 
prevents any two particles of matter 
from occupying the same space at the 
same time. 

Imperfect Earth.— Partial earth. 

Imperfect Linkage.— (1) Magnetic flux 
linkage between two coils or circuits, such 
that some linkage of one circuit is not 
associated with the other circuit. (2) 
Coils or circuits possessing mutual induc- 
tion but also possessing magnetic leakage. 

Imperfect Magnetic Circuit.— A term 
sometimes employed for a magnetic cir- 
cuit in which, from the magnetizing coils 
being placed on one part of the core 
only, the intensity of the flux is greater 
through some portions of the ferric cir- 
cuit than through others, so that some of 



the lines of induction complete their cir- 
cuits by passing through the space sur- 
rounding the core instead of through the 
core itself. 

Impermeability.— The reciprocal of the 
permeability. 

Impermeance.— The reciprocal of the per- 
msiiace. 

Imponderable.— (1) Possessing no weight. 
(2) A term formerly applied to the lumi- 
niferous or universal ether. 

Impressed. — Caused to act or forced upon. 

Impressed Electromotive Force. — 
(1) The electromotive force brought to 
act in any circuit to produce a current 
therein. (2) In an alternating-current 
circuit, the impressed electromotive force 
due to an impressed source, in contradis- 
tinction to the effective electromotive 
force, or that which is active in produc- 
ing current, or the electromotive forces 
due to, or opposed to, self or mutual induc- 
tion. (3) An applied E. M. F. as distin- 
guished from a resultant, active, or watt- 
less E. M. F. 

Impressed Field. — An electric or mag- 
netic field brought to bear upon any sub- 
stance or space as distinguished from sec- 
ondary fields thereby set up. 

Impressed Pressure. — The impressed 
electromotive force. 

Impulse. — (1) Any single or momentary 
force acting on a body. (2) The motion 
produced by a suddenly communicated 
force. 

Impulse of Couples. — The product of the 
magnitude of a couple, and the time it is 
acting. 

Impulsion Cell. — A photo-electric cell 
whose sensitiveness to light may be re- 
stored or destroyed by slight impulses 
given to the plate, either by mechanical 
blows or taps, or by electro-magnetic im- 
pulses. 

Impulsion Effect. — The restoration or 
loss of sensitiveness of a photo-electric 
cell to the action of light, produced by 
means of an impulse, such as a mechan- 
ical tap or blow, or an electro-magnetic 
impulse. 

Impulsive. — Communicated by an im- 
pulse. 

Impulsive Current-Rush in Inductive 
Circuit. — An abnormal rush of current 
which sometimes occurs when a trans- 
former is suddenly switched on to an 
active main. 

Impulsive Discharge. — A discharge pro- 
duced in conductors by suddenly created 
differences of potential. 



Imp.] 



806 



[Inc. 



Impulsive Impedance.— The impedance 
encountered by an oscillatory discharge. 

Impulsive Inductance. — The apparent 
inductance of a conductor or circuit when 
subjected to an impulsive discharge. 

Impulsive Permittance. — The apparent 
permittance of a conductor or circuit 
through which an impulsive discharge is 
passing. 

Impulsive-Rush Discharge. — An im- 
pulsive discharge. 

" In Bridge." — In multiple to a circuit, as 
distinguished from being inserted in 
series with a circuit. 

Inactive Molecules.— (1) Those molecules 
of an electrolyte which, during the pas- 
sage of an electric current, are not re- 
solved into their constituent ions, and 
which, therefore, have no effect on the 
molecular conductivity of the electrolyte. 
(2) The non-dissociated molecules of an 
electrolyte. 

Incandesce. — To glow or shine by means 
of incandescence. 

Incandescence. — The shining or glowing 
of« a substance, usually a solid, by reason 
of its elevation to a sufficiently high tem- 
perature. 

Incandescence, Electric— The shining 
or glowing of a substance, generally a 
solid, by means of heat of electric origin. 

Incandescent. — Shining or glowing with 
heat. 

Incandescent-Ball Electric Lamp.— An 
incandescent electric lamp in which the 
light is produced by a sphere or ball of 
carbon placed in an exhausted glass 
chamber and subjected to electrostatic 
waves of high frequency. 

Incandescent Bombardment-Lamp. — 
An electric lamp in which a refractory 
material is rendered incandescent by the 
molecular bombardment produced by the 
passage of an electric discharge through 
a rarefied space. 

Incandescent Circuit. — A circuit pro- 
vided for the operation of incandescent 
electric lamps. 

Incandeseent-Cut-Out.— (1) A cut-out 
suitable for use in an incandescent light 
circuit. (2) A safety-fuse cut-out. 

Incandescent Filament.— The incandes- 
cing conductor of an incandescent electric 
lamp, whether of small or of compara- 
tively large cross-section, though gener- 
ally of the former. 

Incandescent Electric Lamp. — An elec- 
tric lamp whose light is produced by the 
electric incandescence of a strip or fila- 



ment of some refractory substance, almost 
invariably carbon. 

Incandescent Electric Lighting.— 

Artificial lighting obtained by means of 
incandescent electric lamps. 

Incandescent Generator.— A dynamo- 
electric machine suitable for operating 
incandescent lamps. 

Incandescent Lamp.— An incandescent 
electric lamp. 

Incandescent Lamp-Base.— The base of 
an incandescent electric lamp. 

Incandescent Lamp-Cord.— A flexible 
lamp cord containing two separate con- 
ductors, suitable for use with a pendant 
incandescent electric lamp. 

Incandescent Lamp-Shade.— A shade 
provided for use in connection with an in- 
candescent electric lamp. 

Incandescent Lamp-Socket. —A socket 
provided for the reception of an incan- 
descent lamp. 

Incandescent Lighting. — Artificial 
lighting produced by the use of incandes- 
cent lamps. 

Incandescent Lighting Dynamo-Elec- 
tric Machine. — An incandescent gener- 
ator. 

Incandescent Mantle-Burner.— (1) A 
gauze skeleton, or mantle, employed for 
artificial illumination, made of refractory 
materials and rendered incandescent by 
the heat of aBunsen flame. (2) The man- 
tle of a Welsbach burner. 

Incandescing.— Producing light by incan- 
descence. 

Incandescing Filament. — A lamp fila- 
ment that is producing light by incandes- 
cence. 

Incandescing Lamp. — (1) An incandes- 
cent lamp that is actually producing light. 
(2) An incandescent lamp emitting light. 

Inclination Chart.— A map or chart on 
which the isoclinic lines are marked. 

Inclination Compass.— (1) A magnetic 
needle, free to move in a single vertical 
plane only, and employed for determining 
the angle of dip at any place. (2) An in- 
clinometer or dipping circle. 

Inclination Magnetometer. — An incli- 
nation compass or inclinometer. 

Inclination Map. — A map or chart on 
which isogonal lines, or lines connecting- 
places which have the same magnetic dip 
or inclination, are drawn. 

Inclination of Magnetic Needle.— (1) 
The deviation of a mechanically balanced 
magnetic needle from a horizontal posi- 
tion. (2) The dip of a magnetic needle. 



Inc] 



807 



[Iud, 



Inclinometer. — An inclination compass. 
(2) A word sometimes used for a dipping 
circle. 

Incoming Call. — A call received at an ex- 
change from a subscriber or from another 
exchange, as distinguished from an out- 
going call. 

Incoming Call Trunk Line. — A trunk 
line entering a central telephone station 
and employed for the reception of calls, 
as distinguished from an outgoing call 
trunk line upon which calls are trans- 
mitted. 

Incoming End. — The end of a junction 
telephone wire at which calls are received. 

Incoming Junction Board.— A switch- 
board at a central exchange at which in- 
coming junction wires are received and 
distributed. 

Incoming Lines. — Lines at a telephone 
exchange at which calls are received, as 
distinguished from outgoing lines. 

Incoming Signals. — The signals that are 
received at the home end of a telegraphic 
circuit. 

Incoming Wires. — Wires leading into a 
building, room, switchboard, or other de- 
vice. 

Incomplete Circuit. — An open or broken 
circuit. 

Inconductivity . — A word sometimes used 
for non-conductivity. 

Increased Electric Irritability.— Irrita- 
bi.'ity of nervous or muscular tissue pro- 
duce 1 by a much weaker electric current 
than that required to produce it in nor- 
mal tissue. 

Increment Key. — A telegraphic key so 
connected that an increase or increment 
in the line current occurs whenever the 
key is depressed, as distinguished from a 
key which opens or closes a circuit. 

Increment Key of Quadruplex Tele- 
graphic System. — A key employed to 
increase the strength of a current and so 
operate one of the distant instruments in 
a quadruplex: system, by an increase in 
the strength of the current. 

Independent Circuits. — (1) Separate cir- 
cuits or those which have no electric con- 
nection with other circuits. (2) Circuits 
in electric connection, but acting inde- 
pendently, as though insulated from each 
other. 

* 'In-Current" of Telephone Relay.— 
The current which is received by a tele- 
phone relay, for transmission to another 
circuit. 

Independent-Diphase System. — A 



phrase sometimes used for the four-wire 
diphase system. 

Indestructibility of Energy or Mat- 
ter. — A theory which assumes that 
energy or matter can never be destroyed, 
and that, consequently, when either dis- 
appears in one form or phase, it must re- 
appear in some other form or phase. 

Index of Refraction.— (1) The ratio of 
the sine of the angle of incidence to the 
sine of the angle of refraction for the 
light passing from a vacuum into a mate- 
rial medium. (2) A quantity represent- 
ing the amount of deviation of a ray of 
light from its original course, on its pas- 
sage from a standard medium, or vacuum, 
to another of different density. (3) A 
quantity representing the ratio of the 
velocity of wave-propagation in a vacuum 
to the velocity in a material medium. 
(4) In the electro-magnetic theory of light 
the geometric mean of the specific induc- 
tive capacity and the magnetic induc- 
tivity of a medium to electro-magnetic 
waves of a given frequency. 

India Rubber.— (1) A resinous substance 
obtained from the milky juices of a 
tropical tree. (2) Caoutchouc. 

Indicating Bell.— An electric bell which. 
in order to distinguish between different 
bells in the same office, is provided with 
an annunciator drop which is released by 
each bell when it rings. 

Indicating-Bell Annunciator. — An an- 
nunciator provided for an indicating bell. 

Indicating Lamp.— A lamp connected 
with a circuit, which is lighted or extin- 
guished, or the intensity of whose light 
is caused to vary, on the occurrence of a 
predetermined change in the pressure or 
resistance of the circuit. 

Indicating Push Button.— A push but- 
ton which leaves an indication of its 
having been depressed. 

Indicating Switch. — A switch provided 

with an indicator which shows whether 

. the circuit of the switch is closed or open. 

Indicator. — A term sometimes employed 
for annunciator. 

Indicator Card. — The card of a steam- 
engine indicator, on which are traced the 
curves of pressure, by means of which the 
indicated horse-power of the engine may 
be calculated. 

Indicator Dial, Electric. — In a system 
of railway block signalling by electricity, 
an electro-magnetic indicator having a 
dial which shows the condition of a sec- 
tion of railway. 

Indicator, Electric. — (1) A general term 



Ind.] 



808 



[Ind, 



applied to various devices operated by the 
deflection of a magntic needle, or the 
ringing of a bell, or by both, for indicat- 
ing, at some distant point, the condition 
of an electric circuit, the strength of cur- 
rent passing through any circuit, the 
head of water or other liquid, the pressure 
on a boiler, the temperature, the speed of 
an engine or lines of shafting, the work- 
ing of a machine, or other similar events 
or occurrences. (2) A term sometimes 
used in place of annunciator. (3) Any 
electric or magnetic signalling apparatus. 

Indicator Flap. — A light metal disk or 
cover, hinged over a self-restoring indi- 
cator, in a branching multiple telephone 
switchboard. 

Indifferent Electrode. — In electro-thera- 
peutics, the electrode that is employed to 
merely complete the circuit through the 
organ or part of the body subjected to the 
electric current, and not directly con- 
cerned in the treatment or diagnosis of 
the diseased part, and which, therefore, 
may be located at any convenient point. 

Indifferent Point. — A point in the intra- 
polar regions of a nerve, where the ane- 
lectrotonic and cathelectrotonic regions 
meet, and where the excitability is, there- 
fore, unchanged. 

Indirect Distribution. — A system of 
electric distribution in which intermedi- 
ate contrivances for the transformation 
or accumulation of electric energy are 
employed between the generator and the 
receptive devices. 

Indirect Electrolysis.— Chemical react- 
ions effected as a consequence of electro- 
lytic action, as distinguished from electro- 
lytic actions themselves. 

Indirect Excitation.— The excitation of 
a muscle obtained by placing an electrode 
on its nerve instead of directly on the 
muscle. 

Indirect Welder. — A step-down trans- 
former employed in electric welding. 

Individual Electric Motors.— A term 
sometimes employed for electric motors 
that are coupled directly to the shaft of 
each machine to be driven or operated. 

Individual Signal. — A selective signal, or 
one in which a given signal only is sound- 
ed at a distant point on a circuit with 
which more than one signal is connected. 

Individual Signalling Apparatus.— 

Signalling apparatus provided with indi- 
vidual signals. 

Individual Telephone Switchboard. — 

A single section of a multiple switch- 
board. 



Individual Transformer.— A transform- 
er employed solely for the supply of some 
particular translating device or group of 
devices, as distinguished from a trans- 
former which supplies a number of cir- 
cuits or groups. 

" In-Door " Transformer. — A trans- 
former designed for use inside a building. 

Induced. — (1) Set up or caused by induc- 
tion. (2) Not produced by metallic com- 
munication. 

Induced Atomic or Molecular Cur- 
rents. — Currents supposed to be induced 
in the atoms or molecules of a magnetiz- 
able substance when brought into mag- 
netic flux. 

Induced Circuit.— An inductive circuit. 

Induced Current.— A current produced 
by electro-dynamic induction. 

Induced Current of Transformer.— A 
term sometimes employed for the second- 
ary current of a transformer. 

Induced Direct-Current.— (1) The cur- 
rent produced in an active circuit on the 
breaking of such circuit, having the same 
direction as the active current and tend- 
ing to prolong and strengthen it. (2) The 
break-induced current. 

Induced Electromotive Forces.— E. M. 
F.'s set up by electro-dynamic induction. 

Induced Electric Surgings.— Electric 
surgings induced in neighboring conduct- 
ors by means of electric surgings, oscilla- 
tory discharges, or impulsive current- 
rushes in their vicinity. 

Induced Electrostatic Charge. — A 

charge produced by bringing a body into 
an electrostatic field. 

Induced Lightning Discharge.— (1) A 
lightning discharge produced in a sub- 
stance by induction from a neighboring 
lightning flash. (2) A back or return 
lightning stroke. 

Induced M. M. F.— (1) Any magneto- 
motive force produced by induction. (2) 
The aligned or structural magneto-motive 
force, as distinguished from the prime 
magneto-motive force. 

Induced Magnetic Flux.— Magnetic 
flux produced in any body by induction. 

Induced Reverse Currents.— (1) The 
currents induced in an active conductor 
at the moment of making or closing the 
circuit in the opposite direction to the in- 
ducing current, and, therefore, tending to 
check its flow. (2) The current induced 
in the secondary on making or breaking 
the circuit of the primary. 



Ind.] 



809 



[Ind, 



Induced Spiral or Conductor. — A term 
sometimes used for the secondary spiral or 
conductor of a transformer. 

Inducing.— Producing electromotive 
forces, currents, or fluxes, by means of in- 
duction. 

Inducing Circuit. — Any circuit which 
causes induction. 

Inducing Current of Transformer.— A 
term sometimes employed for the primary 
current of a transformer. 

Inducing Magnet. — The permanent mag- 
net of a relay. 

Inducing Spiral or Conductor. — A term 
sometimes used for the primary spiral or 
conductor of a transformer. 

Inductance. — (1) The capacity for induc- 
tion possessed by an active circuit on itself, 
or on neighboring circuits. (2) Self-in- 
duction. (3) That property, in virtue 
of which a finite electromotive force 
impressed on a circuit does not im- 
mediately generate the full current due 
to the resistance of the circuit, and 
which, when the electromotive force 
is withdrawn, requires a finite time 
for the current strength to fall to its 
zero value. (4) A property, by virtue of 
which the passage of an electric current 
is necessarily accompanied by the absorp- 
tion of electric energy in producing a 
magnetic field. (5) A constant quantity 
in a circuit at rest, and devoid of iron, de- 
pending only upon its geometrical ar- 
rangement, and usually expressed in 
henry s, or in centimetres. 

Inductance Box.— A box containing a 
number of graded inductances, and em- 
ployed for the measurement of the in- 
ductance of a circuit. 

Inductance Bridge. — An apparatus 
similar to a Wheatstone's bridge, for 
measuring the inductance of a circuit. 

Inductance Coil.— (1) An impedance, re- 
actance, or choking coil. (2) A coil placed 
in a circuit, for the purpose of prevent- 
ing an impulsive current-rush in that 
circuit, by means of the counter-electro- 
motive force developed in the coil on 
being magnetized. 

Inductance-Reactance. — The reactance 
of a self-inductive coil, as distinguished 
from the reactance of a condenser, or a 
capacity-reactance. 

Inductance-Resistance.— Reactance. 

Inductance Speed. — (1) A term proposed 
for the product of the co-efficient of self- 
induction by an angular velocity, corre- 
sponding to a simple-harmonic frequency. 
(2) In an alternating-current circuit, the 



product of an inductance and 2n times the 
frequency. 

Inductanceless.— Devoid of inductance. 

Inductanceless Circuit.— (1) A circuit 
practically devoid of inductance. (2) A 
circuit whose magnetic field is negli- 
gible, such, for example, as an ordinary 
incandescent lamp, or a double-wound re- 
sistance coil. 

Inducteous Body. — A term proposed by 
Faraday for a body in which a charge is 
induced by the action of a neighboring 
charge. 

Induction. — (1) The influence exerted by 
a charged body, or by a magnetic field, 
on neighboring bodies without apparent 
communication. (2) The influence pro- 
duced through a dielectric by the action 
of electrostatic or magnetic flux. 

Induction Alternator. — A name some- 
times given to an inductor alternator. 

Induction Booster. — An ordinary induc- 
tion motor whose field coils are in series 
with the mains, employed in an alternat- 
ing-current circuit as a booster or feeder 
regulator. 

Induction Bridge.— (1) A balance in 
which electro-magnetically induced cur- 
rents are equilibrated. (2) An induct- 
ance bridge. 

Induction Coil. — An apparatus consisting 
of two associated coils of insulated wire 
employed for the production of currents by 
mutual induction. 

Induction Factor. — In an alternating- 
current circuit the ratio of the wattless 
component of current to the total current 
strength. 

Induction-Finder. — A term sometimes 

used for a magnetic explorer. 
Induction Flux. — Total magnetic flux in 

any portion of a magnetic circuit. 

Induction Generator.— (1) A generator 
supplying currents which are received 
from the line and reinforced within its 
coils. (2) A generator which operates by 
induction from currents in a short-cir- 
cuited armature. (3) An induction-motor 
driven above synchronism. (4) An alter- 
nating-current dynamo itself incapable of 
generating currents but becoming excited 
by currents received from the line. 

Induction Killer. — Any anti-induction 
device. 

Induction Motor.— (1) An asynchronous 
alternating-current motor, in which cur- 
rents are induced in a short-circuited ele- 
ment or armature. (2) A polyphase or 
unipliase motor operating by the action 



Ind.] 



810 



[Ind. 



of a rotary magnetic field upon a short- 
circuited armature. 

Induction Multiphase-Motor.— An al- 
ternating-current induction, or asynchro- 
nous motor, operated by multiphase cur- 
rents. 

Induction Plates of Condenser.— The 
metallic plates of a condenser on which 
the charges reside. 

Induction Regulator. — A term some- 
times employed for an alternating-current 
regulator. 

Induction Resistance. — An inductive 
resistance. 

Induction Rotary. — A term sometimes 
employed for a rotary converter without 
field excitation. 

Induction Screen. — (1) A plate of metal 
placed between two adjacent electrified 
bodies, or magnetic coils, for the purpose 
of preventing or modifying the inductive 
action they exert on one another. (2) A 
conducting screen wholly or partially 
opaque to inductive action. 

Induction Telegraph.— A general term 
embracing the apparatus employed in in- 
duction telegraphy. 

Induction Telegraphy .—(1) A system for 
telegraphing, between moving trains and 
fixed stations on a railroad, by means of 
impulses transmitted by induction be- 
tween the car and a wire parallel with 
the track. (2) Wireless telegraphy. 

Induction Top. — A top consisting of a 
copper disc supported on a vertical axis, 
which, when spun before the poles of a 
steel magnet, assumes an inclined posi- 
tion, by reason of the currents produced 
therein. 

Inductional Igniting Device.— A de- 
vice for producing ignition by an induced 
electric discharge. 

Inductionless. — Devoid of induction. 

Inductionless Circuit.— A circuit devoid 
of induction. 

Inductionless Resistance. — (1) A resist- 
ance devoid of self-induction. (2) A 
double-wound resistance. 

Inductive. — Capable of producing induc- 
tion. 

Inductive Capacity of Line. — The elec- 
trostatic capacity of a line. 

Inductive Circuit. — Any circuit in which 
induction occurs. 

Inductive Connection. — A connection of 
one circuit with another by means of in- 
duction only, as distinguished from me- 
tallic connection. 

Inductive Disturbance. — Any disturb- 



ance in the operation of a telephone or 
telegraph line produced bj T induction. 
Inductive Electromotive Force. — An 

electromotive force produced by induc- 
tion. 

Inductive Interference.— Inductive dis- 
turbance on a line. 

Inductive Leak. — A leak containing in- 
ductance provided in a cable or circuit as 
distinguished from a leak containing re- 
sistance only. 

Inductive Leakance. — (1) Leakage tak- 
ing place through inductive shunts. (2) 
Leakage artificially produced in a tele- 
graph or telephone circuit through in- 
duction coils. 

Inductive Pole. — An induced pole. 

Inductive-Reactance. — Reactance due to 
self induction as distinguished from re- 
actance due to a condenser. 

Inductive Retardation.— A retardation 
in the appearance of a signal, at the dis- 
tant end of a cable or circuit, produced 
by the action of induction. 

Inductive Resistance. — (1) A resistance 
possessing self-induction. (2) The react- 
ance of a circuit. 

Inductive Resistance Regulator.— Any 
regulator suitable for altering the imped- 
ance of a circuit or conductor by varying 
its inductance. 

Inductivity. — (1) A word proposed for 
specific inductance. (2) Magnetic perme- 
ability. 

Inductivity. — (1) The magnetic perme- 
ability of a magnetic medium. (2; The 
dielectric constant of an electric medium. 

Inductively Associated Circuit.— Such 
a position of a circuit as regards another 
circuit, that any electric change in one 
circuit produces a corresponding change 
in the other circuit by induction. 

Inductize. — To subject a body to the effects 
of induction. - 

Inductometer. — An instrument capable 
of measuring inductance. 

Inductophone. — A device for obtaining 
electric communication between moving 
trains and fixed stations by means of in- 
duction currents. 

Inductor Alternator. — (1) An inductor 
dynamo for alternating currents. (2) An 
alternator in which both armature and 
field are fixed, but in which a rotating 
frame is so placed in relation to each as to 
generate E. M. F.'s in conducting loops 
or coils on the armature. 

Inductor Alternating Generator. — An 
alternator in which neither the field coils 



Ind.] 



811 



[Ins. 



nor the armature rotates, but an iron 
frame rotates in such a manner as to 
periodically fill and empty the armature 
loops with magnetic flux. 

Inductor Dynamo.— (1) A generator in 
which the field and armature coils are 
stationary, and the magnetic flux through 
them is altered by the motion of inductors 
past them. (2) A dynamo-electric gener- 
ator in which the differences of potential 
causing the currents are obtained by mag- 
netic changes in the cores of the armature 
and field coils by the movements of in- 
ductors past them. 

Inductor Generators.— Inductor alter- 
nators or dynamos. 

Inductors of Electrostatic Machine. — 
The electrified parts of an electrostatic 
influence machine, which exert inductive 
influence. 

Inductors. — The laminated masses of iron 
employed in inductor dynamos for the 
purpose of producing variations in the 
magnetic flux of the core and armature. 

Inductorium. — A name sometimes given 
to an induction coil. 

Inductoscope. — Any apparatus for de- 
tecting the presence of induction between 
two circuits. 

Inductric. — Capable of producing induc- 
tion. 

Induct ric Body. — A term proposed by 
Faraday for the body containing the in- 
ducing electric charge. 

Inefficiency of Incandescent Lamp. — 

The number of watts that have to be sup- 
plied to an incandescent lamp per-candle- 
power emitted, very commonly, but inac- 
curately, called the efficiency of the lamp. 

Inertia. — The inability of a body to change 
its condition of rest or motion until some 
force acts on it. 

Inertia, Electric. — A term sometimes 
used for electro-magnetic inertia. 

Inertia Factor. — The factor in a dynami- 
cal system in virtue of which the moving 
system possesses kinetic energy. 

Inferred Zero. — (1) A zero deduced or 
inferred from the deflection produced by 
a charge that is to be measured, by com- 
parison with the value of the deflection 
obtained by a known charge. (2) A zero 
on the scale of an instrument, too remote 
to be mechanically obtainable, but as- 
sumed as virtually existing for the pur- 
poses of calculation. 

Infinity Plug. — (1) A plug provided for 
a hoi? in a resistance box in which the 
two pieces of brass the plug connects are 
not connected by any resistance coil, and 



which, therefore, when withdrawn, leaves 
an open circuit of a practically infinite 
resistance. (2) A discontinuity plug. 

Inflection. — The bending by diffraction of 
rays of light or radiant energy on their 
passage past a sharp edge. 

Inflexible Conduit System. — A conduit 
system which will not permit the intro- 
duction or removal of its conductors, 
after the structure is completed. 

Influence. — A word sometimes used in- 
stead of electrostatic induction. 

Influence Charge.— A charge produced 
by electrostatic induction. 

Influence, Electric. — Electrostatic induc- 
tion. 

Influence Machine. — A name sometimes 
used for an electrostatic-induction ma- 
chine. 

Infra-Red Frequencies. — Frequencies 
lower or smaller in number than those of 
red light. 

Infra-Red Light. — A term applied to radi- 
ation frequencies below the reds of the 
spectrum. 

Infra-Red Spectrum. — That portion of 
the spectrum which lies below the red, or 
whose frequencies are smaller than those 
of the red. 

Initial. —Placed or occurring at the be- 
ginning. 

Initial Magnetization. — Magnetization 
originally produced or imparted. 

Injection of Telegraph Poles.— Impreg- 
nating telegraph poles with any preser- 
vative liquid. 

Injector. — An apparatus for the introduc- 
tion of a condenser or other device into an 
electric circuit at a definite moment and 
for a definite interval of time. 

Inners. — In telephony, the internal pair of 
springs of a jack. 

In-Put. — The power absorbed by any ma- 
chine in causing it to perform a certain 
amount of work. 

Inside Box-Brush. — A brush suitably 
shaped for polishing the inside of tubular 
surfaces, for the purpose of cleansing such 
surfaces so as to prepare them for electro- 
plating. 

Inside Wiring.— (1) In a system of incan- 
descent lighting, the conductors that lead 
to the interior of a house or other building 
to be lighted. (2) Any conductors placed 
inside a building. 

Inside Work. — Indoor wiring. 

Insulation, Electric. — A term sometimes 
employed for electric sun-stroke or elec- 
tric prostration. 



Ins.] 



812 



[Ins. 



Inspection Boxes.— Man-holes provided 
for the inspection of electric mains. 

Installation. — (1) A general term embrac- 
ing the entire plant and accessories re- 
quired to perform any specified work. 
(2) The act of placing, arranging or erect- 
ing a plant or apparatus. 

Installation, Electric— (1) The establish- 
ment of any electric plant. (2) A plant. 

Instantaneous. — Occurring at an instant. 

Instantaneous-Contact Method. — A 
method of determining the form of an 
alternating-current wave by making con- 
tacts with the circuit at definite instants 
in each cycle. 

Instantaneous Current. — The current 
strength taken at any given moment of 
time. 

Instantaneous Electromotive Force.— 
The value of the electromotive force taken 
at any given instant of time. 

Instantaneous Efficiency of Trans- 
former. — The efficiency of a transformer 
taken at any instant of time, as distin- 
guished from its mean efficiency, or its 
efficiency extending over a fairly consid- 
erable time. 

Instantaneous Pressure.— The instan- 
taneous electromotive force. 

Instantaneous Value of Periodic Cur- 
rent or E. M. F.— The value of a peri- 
odic current or E. M F. at any given in- 
stant of time as distinguished from an 
average or effective value. 

Instantaneous Values. — Values meas- 
ured at a given instant of time, as dis- 
tinguished from average values. 

Instrument Bars. — In a multiple tele- 
phone switchboard the conducting bars 
connected to an operator's set. 

Instrument Zero. — The true zero of an 
instrument scale, as distinguished from a 
zero selected at some other point or a 
false zero. 

Insulate. — To so insulate a body as to pre- 
vent electricity from being conducted to 
or removed from it. 

Insulated Body. — A body supported on 
or surrounded by an insulator, or non- 
conductor of electricity. 

Insulated Conductors. — Conducting 
wires provided with an insulating coating 
or covering. 

Insulated. — A term sometimes employed 
in telegraphy for a free wire, or a wire 
that is disconnected from its apparatus 
and left insulated. 

Insulated Pliers.— A pair of pliers whose 



handles are encased in insulating ma- 
terial. 

Insulated Trolley-Crossing.— A cross- 
ing placed at the intersection of two 
streets where trolley wires cross each 
other, provided with an insulating mate- 
rial to prevent the contact of the crossing 
wires. 

Insulated Turn-Buckle.— (1) A turn- 
buckle carrying a shackle insulator at one 
end. (2) A device supported by suitable 
insulators employed on overhead circuits 
for straightening the wires by increasing 
the stress on them. 

Insulated Wires.— Wires provided with 
insulating coverings or coatings. 

Insulating. — Providing with insulation. 

Insulating Bushing.— A bushing made 
of insulating material. 

Insulating Cements.— Various mixtures 
of gums, resins and other substances pos- 
sessing the ability not only of binding two 
or more substances together, but also of 
electrically insulating them from one 
another. 

Insulating Coating. — A coating or cover- 
ing of insulating material. 

Insulating Covering. — An insulating 
coating. 

Insulating Joint.— A joint in an insulat- 
ing material or covering in which the 
continuity of the insulating material is 
ensured. 

Insulating Sleeve.— A sleeve formed of 
insulating material, and provided for 
covering splices in an insulated con- 
ductor. 

Insulating Stool. — A stool provided with 
insulating supports of vulcanite, or simi- 
lar high-insulating substance, employed 
to afford a convenient insulating stand or 
support. 

Insulating Tape.— A ribbon of flexible 
material impregnated with okonite, rub- 
ber, or other similar material, and gen- 
erally containing some adhesive sub- 
stance, employed for insulating wires or 
electric conductors at joints, or other ex- 
posed places. 

Insulating Tube.— (1) A tube of insulat- 
ing material provided for covering a splice 
in an insulated conductor. (2) A tube 
of insulating material provided for slip- 
ping over an insulated conductor where it 
passes through a partition, and employed 
for preventing the abrasion of the insu- 
lating material at that point. 

Insulating Varnish.— An electric varnish 
formed of any good insulating material. 



Ins,] 



813 



[Int. 



Insulating Washer.— A washer formed 
of insulating material. 

Insulation. — Any medium or material 
that will prevent a body from gaining or 
losing light, heat, electricity, etc. 

Insulation Bracket. — A bracket of insu- 
lating material, provided with an insu- 
lator. 

Insulation Break-Down.— Any failure 
of the insulation which prevents it from 
insulating. 

Insulation, Electric. — A non-conducting 
material so placed with respect to a con- 
ductor as to prevent either the loss of its 
charge, or the leakage of its current. 

Insulation Joint. — A joint in an insu- 
lating material or covering in which con- 
tinuity is preserved both in the conducting 
and in the insulating substance. 

Insulation Lightning-Protection.— The 
protection of an instrument by means of 
an insulating lightning-protector from the 
jumping of a spark across it from layer 
to layer. 

Insulation Lightning-Protector. — A 
lightning protector by means of which a 
discharge is prevented from jumping 
across the coils of an instrument from 
layer to layer, and thus damaging its 
insulation. 

Insulation Materials. — (1) Materials 
whose resistivity is high. (2) Non-con- 
ductors. 

Insulation Resistance.— (1) The resist- 
ance existing between a conductor and 
the earth, or between two conductors 
in a circuit through insulating materials 
lying between them. (2) The resistance 
taken between a line or conductor and 
the earth through the insulators, or be- 
tween two separate wires of a cable 
through the insulating materials separ- 
ating them. (3) A term sometimes applied 
to the resistance of the insulating ma- 
terial of a covered wire or conductor. 
(4) The resistance of any insulation. 

Insulator. — Any device employed for in- 
sulating a wire or other body. 

Insulator Bracket. — A frame of wood or 
metal for holding the insulator of an 
overhead wire, and of such simple form 
as to be readily attached to a wall or 
support. 

Insulator Cap. — A cover or cap placed 
some distance above an insulator, but 
separated from it by an air space. 

Insulator Pin. — The bolt by which an 
insulator is attached to a bracket, pole- 
arm, or support. 

Intaglio. — (1) An engraving in which the 



surface is so hollowed out that an im- 
pression therefrom would give the ap- 
pearance of a bas-relief. (2) The copy of 
a coin or other similar object obtained 
in an electro. 

Intake. — A word sometimes used instead 
of input. 

Intake of Dynamo. —The mechanical 
activity which a dynamo absorbs when 
running. 

Intake of Machine.— The activity re- 
quired to operate a machine. 

Intake Wires.— The wires which feed a 
distribution box. 

Integrating Meter.— Any meter which 
leaves a record of, and sums up, or inte- 
grates, some quantity with respect to 
time. 

Integrating Wattmeter. — (1) A watt- 
hour meter, or a meter which integrates 
the power which passes through it with 
respect to time. (2) An energy meter. 

Integrator. — An apparatus for automat- 
ically performing the operation of inte- 
gration, or the continuous summing up 
of instantaneous values. 

Intensity. — (1) The surface density of a 
vector or directed quantity. (2) The de- 
gree of concentration with which a num- 
ber of forces act. 

Intensity Armature. — A term formerly 
employed for an armature with coils of 
many turns, and, consequently, of a com- 
paratively high resistance. (Obsolete.) 

Intensity Current.— A term formerly 
employed for the current produced by a 
series-connected battery. (Obsolete.) 

Intensity of Current.— (1) A term taken 
from the French language to indicate cur- 
rent strength. (2) Current density, or cur- 
rent strength per- unit-area of normal 
cross-section. 

Intensity of Field. — The strength or 
density of a magnetic field as measured 
by the quantity of magnetic flux that 
passes through it per-unit-of-area of nor- 
mal cross-section. 

Intensity of Illumination.— The quan- 
tity of light received per-unit-of-sui f ace . 

Intensity of Light. — (1) In a given direc- 
tion of emission, the ratio of the flux of 
light in a small solid angle containing 
that direction to the solid angle. (2) The 
candle-power of a light. 

Intensity of Magnetic Flux.— (1) The 
quantity of magnetic flux per-unit-of-area 
of normal cross-section. (2) The density 
of magnetic flux. 

Intensity of Magnetization. — (1) A 



Int.] 



814 



[Int. 



quantity which represents the intensity 
of magnetization produced in a sub- 
stance. (2) A quantity which represents 
the intensity with which a magnetizable 
substance is magnetized. (3) Magnetic 
moment per-unit- volume. (4) The sur- 
face density of imaginary magnetic mat- 
ter on any surface normal to the direc- 
tion of magnetization. 

Intensity of Radiation.— (1) The ratio 
existing between the amount or quantity 
of radiation, and the surface from which 
that radiation takes place. (2) The ratio 
of the flux of energy in any small solid 
angle of a beam to the solid angle. 

Interaetance. — In an induction coil oper- 
ated on a simple alternating-current 
circuit, the product of the mutual in- 
ductance and the angular velocity cor- 
responding to the frequency of the cur- 
rent, and expressible in ohms. 

Inter Air-Space. — A term sometimes 
employed for the air-space or entrefer. 

Inter- Atomic Ether.— A term sometimes 
used for the ether existing between the 
constituent atoms of the molecules. 

Inter-Connected Armature- Winding. 
(1) Such a connection of the separate 
circuits in a multipolar armature as will 
permit a single pair of brushes to be 
employed on the commutator. (2) A 
cross-connected armature. 

Inter-Connection .—The cross-connection 
of an armature. 

Inter-Crossing. — In a system of tele- 
phonic circuits, a device for avoiding the 
disturbing effects of induction, by 
alternately crossing equal sections of the 
line wires. 

Inter-Exchange "Working. — (1) Tele- 
phonic communication effected through 
the medium of more than a single ex- 
change (2) Telephone communication 
passing between two exchanges, or be- 
tween two subscribers connected there- 
with. 

Interference of Electro-Magnetic 

Waves. — Interference effects, similar to 
those produced in the case of light and 
sound, observed in electro-magnetic 
waves when two systems of waves of equal 
frequency simultaneously act, in opposed 
phases, on the same medium. 

Inter-Ferric Gap.— (1) An air-gap in an 
aero-ferric magnetic circuit between iron 
and iron. (2) The entrefer. 

Inter-Ferric Space.— An inter-ferric gap. 

Inter flange.— The distance betw-een the 
two flanges of a bobbin, measured par- 
allel to the bobbin's axis, and represent- 



ing the length of the cylindrical space 
which may be occupied by wire when the 
bobbin is wound. 

Inter-Induction. — Mutual induction. 

Interior Conduit. — (1) A conduit provided 
inside the walls of a house, or in other 
convenient spaces within a house, for the 
reception of the house wires. (2) A con- 
duit in the walls or floors of a building, 
provided for accommodating electric 
conductors. 

Interior-Conduit Junction-Box. — The 
box provided in a system of interior con- 
duits to receive the terminals of the feed- 
ers, and in which connection is made 
between the feeders and the mains, or 
the mains and branches. 

Interior-Pole Dynamo.— A dynamo hav- 
ing field poles in the interior of a cylin- 
drical or Gramme-ring armature. 

Inter-Linked Diphase-System. — A 

three-wire diphase-system. 
Inter-Linked Polyphase-System. — A 
polyphase system of conductors so inter- 
connected that one wire serves as the 
return for another, and distinguished 
from a polyphase system in which each 
phase is provided with a separate circuit. 

Inter-Locking Apparatus.— A device for 
mechanically operating railroad switches 
and semaphoric signals from a distant sig- 
nalling tower, for the purpose of indicat- 
ing the position of such switches, by 
means of a system of inter-locking levers, 
so inter-locked as to render it impossible, 
after a route has once been set and a sig- 
nal given, to clear a signal for a route 
that would conflict with the one previ- 
ously set up. 

Inter-Locking Magnet.— A magnet em- 
ployed in a system of electric railroad 
signals for crossings, whereby a gong is 
caused to ring at the crossings on the ap- 
proach of a train, and is automatically 
stopped by the same train after it has 
passed the crossing. 

Intermediate Cable.— A type of cable 
intermediate between a shore-end cable 
and a deep-sea cable. 

Intermediate Station. — Any station be- 
tween the terminal stations of a telegraph 
line. 

Intermediate Switch. — A switch em- 
ployed at an intermediate telephone 
station for communicating with either 
terminal station at will, without inter- 
rupting the line. 

Intermittent. — (1) Acting at intervals 
only. (2) Fluctuating or pulsating. 



Int.] 



815 



Lint, 



Intermittent Contact. — The occasional 
contact of a telegraphic or other line 
with other wires or conductors, by swing- 
ing, or by alternate contractions and ex- 
pansions, occasioned by changes of tem- 
perature. 

Intermittent Cross.— (1) An accidental 
contact, generally metallic, occasioned by 
wires being brought into occasional con- 
tact with- one another, or with some other 
conductor by the intermittent action of 
the wind. (2) A swinging cross. 

Intermittent Current. — A current that 
does not flow continuously, but which 
flows and ceases to flow at intervals, so 
that electricity is practically alternately 
present and absent from the circuit. 

Intermittent Currents of Wheatstone 
System. — In the Wheatstone automatic 
system the transmission of short initial 
and final currents in each signal. 

Intermittent Disconnection.— Any 
fault in a line which occurs at intervals 
or intermittently. 

Intermittent Electromotive Force. — 
An electromotive force which acts inter- 
mittently. 

Intermittent Earth. — (1) A fault in a 
telegraphic or other line in which, by the 
action of the wind, or by occasional ex- 
pansion by heat, the iine is brought 
into intermittent contact with the earth. 
(2) A swinging earth. 

Intermittent Integrating Meter. — A 
meter which does not take a reading of 
the current or power continuously, but 
at regular intervals, and then adds up 
the result. 

Intermittent System of Currents.— A 
system of currents employed in teleg- 
raphy, in which the initial and final 
currents are separated by an interval or 
insulation. 

Intermitter.— An interrupter. 

Inter-Molecular. — Between the mole- 
cules. 

Inter-Molecular Ether.— A term some- 
times used for the ether that exists be- 
tween the molecules of matter. 

Internal Armature Generator.— A gen- 
erator in which the armature is situated 
within the field-poles, as distinguished 
from a generator whose armature is exter- 
nal to the field. 

Internal Characteristic of Dynamo.— 
A curve showing the E. M. F. generated 
in a dynamo under varying excitation, as 
distinguished from the external charac- 
teristic showing the E. M. F. at terminals. 



Internal Circuit.— That part of a circuit 
which is included within the electric 
source. 

Internal Magnetic-Circuit. — A term 
sometimes employed for that part of a 
magnetic circuit which lies within the 
magnetic core. 

Internal Magnetic-Field.— That portion 
of a magnetic field produced by a magnet 
which lies within the magnetic core. 

Internal Polarization of Moist Body. — 
A polarization exhibited by such moist 
bodies as nervous or muscular fibres, 
the juicy parts of vegetables and animals, 
or in general, by all bodies possessing a 
firm structure and filled with a liquid, on 
the passage through them of a strong 
electric current. 

Internal Poles of Dynamo.— (1) The in- 
wardly projecting field poles of a dy- 
namo. (2) Magnetic field-poles internal 
to an armature. 

International Ampere.— (1) The value 
of the ampere as adopted by the Inter- 
national Congress of 1893, at Chicago. 
(2) The value of an ampere equal to the 
one-tenth of a unit of current in the C. 
G. S. system of electro-magnetic units, 
and represented with sufficient accuracy 
for practical purposes, by the unvarying 
current, which, when passed through a 
solution of nitrate of silver in water, in 
accordance with certain specifications, 
deposits silver at the rate of 0.001118 of a 
gramme-per-second. 

International Coulomb.— (1) The value 
of the coulomb as adopted by the Inter- 
national Electrical Congress of 1893, at 
Chicago. (2) The quantity of electricity 
equal to that transferred fcb rough a cir- 
cuit by a current of one International 
ampere in one second. 

International Farad.— (1) The value of 
the farad as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) The capacity of a conductor charged 
to a potential of one International volt by 
one International coulomb of electricity. 

International Henry.— (1) The value of 
the henry as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) The value of the induction in a circuit, 
when the electromotive force induced in 
the circuit is one International volt, and 
the inducing current varies at the rate of 
one ampere per second. 

International Joule.— (1) The value of 
the joule as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) A value equal to 10 7 units of work of 



Int.] 



816 



[Inv. 



the C. G. S. system and represented with 
sufficient accuracy for practical purposes 
by the energy expended in one second by 
one ampere in one International ohm. 

International Morse Code. — A term 
sometimes employed for the International 
telegraphic alphabet, as distinguished 
from the American Morse Code. 

International Ohm. — (1) The value of 
the ohm as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) A value of the ohm equal to 10 9 units 
of resistance of the C. G. S. system of 
electro-magnetic units, and represented by 
the resistance offered to an unvarying 
electric current by a column of mercury 
at the temperature of melting ice, 14.4521 
grammes in mass, of a constant cross-sec- 
tional area, and of the length of 106.3 
centimetres. 

International Telegraphic Code.— The 
International Morse Code. 

International Unit of Activity.— The 
International watt. 

International Unit of Work.— The In- 
ternational joule. 

International Volt. — (1) The value of the 
volt as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) Such an electromotive force that 
steadily applied to a conductor whose 
resistance is one International ohm, will 
produce a current of one International 
ampere, and which is represented with 
sufficient accuracy for practical use by 
42 34 of the electromotive force between 
the poles or electrodes of the voltaic cell 
known as Clark's cell, at a temperature of 
15° Cent, when prepared in accordance 
with certain specifications. 

International Watt. — (1) The value of 
the watt as adopted by the International 
Electrical Congress of 1893, at Chicago. 
(2) A value equal to 10 7 units of activity 
in the C. G. S. system, and equal to the 
work done at the rate of one joule-per- 
second. 

Inter-Node. — The space between two ad- 
jacent nodes. 

Inter-Polar. — Between the poles. 

Inter-Polar Gap. — Ah air-gap or space 
between the faces of opposing pole-pieces. 

Inter-Polar Space.— The inter-polar gap. 

Interpolated Commutator Segments. 
Blank commutator segments. 

Interrupted. — Broken or opened. 

Interrupted Current System.— A sys- 
tem of electric distribution effected by 
the aid of periodically interrupted contin- 
uous currents. 



Interrupter.— Any device for interrupt- 
ing or breaking a circuit. 

Inter-Urban Communication.— T e 1 e - 
graphic or telephonic communication be- 
tween adjacent cities. 

Inter-Urban Electric Railway. — An 
electric railway suitable for use between 
adjacent cities. 

Inter - Urban Telephony.— Telephonic 
communication carried on between adja- 
cent cities. 

Intra-Molecular. — (1) Inter-molecular, or 
between the molecules. (2) Within the 
confines of a molecule. 

Intra-Polar Electrolysis.— Electrolytic 
action taking place in the region between 
the electrodes, as distinguished from that 
which occurs in their immediate vicinity. 

Intrinsic Brilliancy of Luminous 
Source. — (1) At any point of a luminous 
surface the ratio of the luminous intensity 
along the normal to the small surface area 
from which it is emitted, (2) Luminous 
intensity per-unit-area of normal lumi- 
nous surface. 

Intrinsic Electrization.— A term pro- 
posed for permanent impressed electriza- 
tion in a substance from internal causes. 

Intrinsic Intensity of Light. — The 
quantity or flux of light emitted normally 
from a unit of surface of a luminous 
source. 

Intrinsic Magnetization. — Magnetiza- 
tion due to impressed magnetic force, as 
distinguished from magnetization due to 
electric currents. 

Intrinsic Radiation of Luminous 
Source. — (1) The radiation of a luminous 
source expressed in lumen s-per-square- 
centimetre. (2) The flux density of light 
issuing normally from a luminous source. 

Invariable Calibration of Galvano- 
meter. — In a galvanometer with absolute 
calibration, a method for preventing the 
occurrence of variations in the intensity 
of the field of a galvanometer, due to the 
neighborhood of masses of iron. 

Inverse Current. — (1) The current which 
tends to be produced by a current in its 
own circuit on making or closing the cir- 
cuit. (2) The current produced in the 
secondary of an induction coil on the mak- 
ing or completion of the circuit of the 
primary. (3) The make-induced current. 

Inverse Electromotive Force.— An elec- 
tromotive force which acts in the oppo- 
site direction to another already existing 
electromotive force. 

Inverse Secondary Current. — The 
make-induced current. 



Inr.] 



817 



[Iro, 



Inversion, Electric. — The determination 
of electric distribution over the surfaces of 
neighboring electrified conductors by the 
geometrical method of inversion. 

Invert Insulator. — An insulator support- 
ed in an inverted position. 

Inverted Arc. — An inverted arc-lamp. 

Inverted Arc-Lamp. — An electric arc- 
lamp in which the positive carbon is 
lowermost, or inverted, as compared with 
its position in the ordinary arc-lamp. 

Inverted Dynamo. — A dynamo whose 
armature bore or chamber is placed below 
the field-magnet coils. 

Inverted Induction-Coil. — A term some- 
times employed for a step-down trans- 
former. 

Invisible Electric-Contact Matting.— 
A matting or other floor covering, pro- 
vided with a series of invisible electric 
contacts, which are closed by a person 
walking over them. 

Invisible Spectrum. — That portion of the 
spectrum which is incapable of affecting 
the eye as light. 

Ionic. — Of or pertaining to the ions. 

Ions. — The groups of atoms or radicals into 
which a molecule is separated by electro- 
lytic decomposition. 

Ionic Attraction. — The mutual attrac- 
tion produced by the cathions and the 
anions. 

Ionic Conductivities. — Specific conduc- 
tivities of ions, so selected that their sums 
give molecular conductivities for any 
combination of ions. 

Ionisation. — (1) The decrease in the 
strength with which the separate atoms 
or radicals are held together in the mole- 
cules of an electrolyte. (2) A modified 
dissociation of the molecule of an elec- 
trolyte which consists in the weakening 
of the force which holds together its ions 
or radicals. 

Iron-Armored Conduit. — (1) A conduit 
provided with an exterior iron casing or 
covering. (2) A conduit in which each 
duct has an iron casing or covering. 

Iron-Clad.— Surrounded by iron. 

Iron-Clad Armature. — (l)The armature of 
a dynamo or motor, whose insulated coils 
are entirely or nearly surrounded by the 
iron of the armature core. (2) An arma- 
ture in which the conductors are buried 
in slots, grooves, or tunnels below the 
surface of the armature core. 

Iron-Clad Armature Windings.— Ar- 
mature windings that are entirely or 
nearly surrounded by iron. 

5* 



Iron-Clad Coil. — An iron-clad magnet. 
Iron - Clad Drop. — An annunciator or 

telephone drop whose electro-magnet is 

iron-clad. 

Iron-Clad Dynamo.— (1) A dynamo whose 
armature is iron -clad. (2) An iron-en- 
cased dynamo. 

Iron-Clad Electro-Magnet.— An electro- 
magnet whose magnetizing coil is almost 
entirely surrounded by iron — in some 
cases to increase its portative power, in 
others to increase its inductance, and in 
yet others to shield its magnetic varia- 
tions. 

Iron-Clad Generator.— An iron-clad dy- 
namo. 

Iron-Clad Inductance. — An inductance 
associated with a ferric or sero-f erric mag- 
netic circuit, as distinguished from an 
inductance associated with a non-ferric 
magnetic circuit, 

Iron-Clad Magnet. — (1) An electro-mag- 
net whose magnetic resistance is lowered 
by a casing of iron connected with the 
core, and provided for the passage of the 
magnetic flux. (2) An iron-clad electro- 
magnet. 

Iron-Clad Motor. — A motor whose ar- 
mature is iron-clad. (2) An iron-encased 
motor. 

Iron-Clad Rheostat.— A rheostat whose 
resistance coils are provided with an 
enamelled insulation, and imbedded in a 
mass of iron. 

Iron Core. — The mass of iron on which 

are placed the magnetizing coils of an 

electro-magnet or solenoid. 
Iron-Core Loss. — The hysteretic and Fou- 

cault losses due to the presence of an iron 

core. 

Iron Covered Cable. — A submarine 
cable provided with an iron sheathing. 

Iron-Enclosed Electro-Magnet. — An 

iron-clad electro-magnet. 

Iron-Loss in Transformer. — The loss of 
energy in a transformer due both to mag- 
netic hysteresis or magnetic friction, and 
to the setting up of eddy or Foucault 
currents in the iron. 

Iron Magnetic Circuit.— A ferric mag- 
netic circuit. 

Iron Reluctance.— (1) The reluctance in 
a magnetic circuit due to the presence of 
iron in that circuit. (2) Reluctance in 
iron. 

Iron- Work Fault of Dynamo. — A 
ground or connection between the circuit 
of a dynamo and any part of its iron 
frame. 



Irr.] 



818 



[Iso, 



Irrationality of Dispersion.— A lack of 
proportionality in the dispersions of spec- 
tra produced by different refractive media. 

Irreciprocal Conduction.— (1) Conduc- 
tion in which the magnitude of the cur- 
rent is altered when its direction is re- 
versed. (2) The electric conduction in 
an assymmetrical resistance. 

Irregular Magnetic Flux.— Magnetic 
flux which is not uniform, but is either 
converging or diverging, as distinguished 
from uniform magnetic flux. 

Irregular Variation. — Any variation of 
the magnetic needle which occurs at ir- 
regular intervals. 

Irreversible Heat.— (1) Heat produced in 
a homogeneous conductor by the passage 
of electricity through it in any direction. 
(2) In an electric circuit, the joulean heat- 
ing effect as distinguished from the 
Peltier effect. (3) In an electric circuit 
any development of heat by the current, 
which does not depend upon its direction. 

Iridescence. — Interference effects pro- 
ducing rainbow-colored tints by the re- 
fraction of light from thin, transparent, 
finely striated surfaces. 

Irritability, Electric— The irritability 
of nerves or muscles produced by an elec- 
tric current or discharge. 

Irrotational Stress. — (1) Stress unac- 
companied by rotation. (2) A stress de- 
void of curl. 

Isobarie Lines. — Isobars. 

Isobarometric Lines.— The isobarie lines. 

Isobars. — (1) Lines connecting places on 
the earth's surface which simultaneously 
have the same barometric pressure. 
(2) The isobarie lines. 

Isochasmen Curves. — Curves drawn on 
the earth's surface between zones having 
equal frequency of auroral discharges. 

Isoehronism. — Equality of time- vibration 
or motion. 

Isoehronize. — To produce equality of time- 
vibration or motion. 

Isochronizing.— Producing equality of 
time-vibration or motion. 

Isochronous Oscillations. — Isochronous 
vibrations. 

Isochronous Vibrations. — Vibrations 
or oscillations which perform their to- 
and-fro motions on either side of the 
position of rest in equal times. 

Isoclinal. — Possessing the same inclina- 
tion. 

Isoclinal Lines.— Lines connecting places 



on the earth's surface which have the 

same magnetic inclination or dip. 
Isoclinal Chart. — A map or chart on 

which isoclinal lines are marked. 
Isoclinic. — Of or pertaining to the 

isoclinals. 

Isodynamie. — Possessing equal force. 
Isodynamic Chart or Map. — A map or 

chart on which isodynamic lines are 

marked. 

Isodynamic Lines.— Lines connecting 
places which have the same total mag- 
netic intensity. 

Iso-Electric Points. — A term sometimes 
used in electro-therapeutics for points of 
equal potential. 

Isogonal. — Of or pertaining to the isogonal 

lines. 
Isogonal Chart or Map.— A chart or 

map on which the isogonal lines are 

marked. 
Isogonal Lines. — Lines connecting places 

on the earth's surface which have the 

same magnetic declination. 

Isogonic. — Of or pertaining to the isogonal 
lines. 

Isolated Electric Lighting.— Electric 
lighting in which the plant is located on 
the premises that are to be lighted, as 
distinguished from a plant located at a 
station, central either to a number of 
buildings, or to an extended area to be 
lighted. 

Isolated Plant. — An electric plant or dis- 
tribution system confined to a building 
or group of buildings as distinguished 
from a central-station system. 

Isolated-Station Telephone Switch- 
board. — A switchboard established for 
the inter-communication of a number of 
telephoners, where the distance separating 
them is considerable, or where privacy 
in the communication is essential. (2) A 
small sub-station telephone switchboard. 
(3) A domestic telephone switchboard. 

Isolatine. — A variety of insulating mate- 
rial. 

Isolating Switch for Lamps.— A short- 
circuiting switch designed to cut a lamp 
completely out of connection with a cir- 
cuit and without opening or breaking the 
circuit of other lamps. 

Isolux. — (1) A line connecting points of 
equal illumination on any illumined sur- 
face. (2) A line of equal illumination. 

Isothermal Expansion of Gas.— The ex- 
pansion of a gas whose temperature is 
maintained constant. 



ISO.] 



819 



[Joe. 



Isomorphism.— The quality of possessing 
the same crystalline form. 

Isomerism. — A state or condition of com- 
pound substances which, though identical 
in composition, yet possess entirely dif- 
ferent properties. 

Isothermal Surfaces.— Surfaces on a 
body, all points of which have the same 
temperature. 

Isothermals. — Lines connecting places on 
the earth's surface which have the same 
mean annual temperature. 

Isotropic. — Possessing equal elasticity in 
all directions. 

Isotropic Conductor.— (1) A substance 
which possesses the same powers of elec- 
tric conduction in all directions. (2) An 
electrically homogeneous conducting 
medium. 



Isotropic Dielectric— A dielectric pos- 
sessing the same powers of inductive 
capacity in all directions. 

Isotropic Medium.— A medium possess- 
ing the same properties iti all directions. 

Isotropism. — The quality of possessing 
equal elasticity in all directions. 

Isthmus Method of Magnetization.— 

A method of obtaining an exceedingly 
strong magnetization by so placing the 
body to be magnetized that it forms a 
narrow isthmus between the pole-pieces 
of a powerful electro-magnet. 

Isynchronous Vibrations.— (1) Vibra- 
tions possessing equality of time of vibra- 
tion or motion. (2) Isochronous vibra- 
tions. 



J. — A contraction proposed for joule. 

Jablochkoff Candle. — An electric arc 
light in which the two carbon electrodes 
are placed parallel to each other, and 
maintained at a constant distance apart 
by means of a strip of an insulating sub- 
stance placed between them, 

JablochkofT's Igniter.— A small strip of 
carbon or carbonaceous material that is 
readily rendered incandescent by a cur- 
rent, placed between the free ends of the 
parallel carbons of a Jablochkoff candle, 
for the formation of an arc on the passage 
of the current. 

Jack Hole. — In a telephone switchboard 
the hole leading into a jack. 

Jack Panel.— The panel of a telephone 
switchboard provided for the support of 
the jacks. 

Jack Switch. — A switch operated by 
means of a spring jack. 

Jacketed Magnet.— A term sometimes 
applied to an iron-clad magnet. 

Jacobi's Law. — The maximum activity is 
performed by an electric motor when its 
counter-electromotive force is equal to 
one-half of the impressed electromotive 
force. 

Jacobi's Unit of Current.— Such a cur- 
rent that when passed through a volta- 
meter will liberate a cubic centimetre of 
oxygen and hydrogen per second at zero 
Cent., and 760 millimetres barometric 
pressure. 

Jacobi's Unit of Resistance.— (1) The 



electric resistance of 25 feet of a certain 
copper ware weighing 345 grains. (2) The 
resistance of a copper wire one metre in 
length and one millimetre in diameter of 
cross-section. 

Jar, Electric. — A name formerly given to 
a Leyden jar. 

Jar of Secondary Cell. — The jar in 
which the electrolyte and plates of a sec- 
ondary cell are placed. 

Jaws of Switch. — The metallic clips pro- 
vided for the reception of the knife-blades 
of a switch. 

Jet Photometer. — An apparatus for de- 
termining the candle-power of an illu- 
minating gas by means of the height of a 
jet of such gas when burning under con- 
stant conditions of pressure and tempera- 
ture. 

Jewelry, Electric. — Minute incandescent 
lamps substituted for gems in articles of 
jewelry. 

Jockey Gear. — The cable gear through 
which a cable has to pass w T hen entering 
or leaving a picking-up or paying-out 
drum, and in which it passes under 
weighted wheels, called jockey wheels, 
for the purpose of maintaining a uniform 
tension of the cable upon the drum so as 
to prevent slip. 

Jockey of Relay. — A form of extension 
tongue pivoted friction-tight upon the 
tongue of a sensitive relay employed in 
submarine telegraphy. 

Jockey Wheel. — A weighted wheel riding 
over a cable on a grooved wheel in a 



Joi.] 



820 



fjun. 



cable ship for the purpose of preserving 
uniformity of tension in the cable. 

Joining-TJp. — (1) Connecting in series or 
multiple-arc. (2) Generally, connecting 
or placing in a circuit. 

Joining-Up a Wire. — Connecting a wire 
to an apparatus or circuit after it has 
been disconnected or grounded. 

Joint. — (1) The junction of two or more 
pieces or conductors. (2) The place 
where the junction of two or more pieces 
or conductors is effected. 

Joint Admittance. — The total or com- 
bined admittance of a number of separate 
admittances connected in parallel. 

Joint Conductance. — The combined con- 
ductance of a number of separate con- 
ductances connected in parallel. 

Joint-Cooling Tray. — A tray employed 
for cooling a cable core-joint by a cooling 
mixture. 

Joint Magnetomotive Force.— The re- 
sultant magnetomotive force of a number 
of simultaneously acting magnetomotive 
forces. 

Joint Reluctance. — The combined reluc- 
tance of a number of parallel-connected 
reluctances. 

Joint Reluctivity. — The reluctivity of a 
number of parallel-connected reluctivi- 
ties. 

Joint Resistance. — The combined resist- 
ance of a number of parallel-connected 
resistances. 

Joint Trough. — A trough of water or 
cooling solution in which a submarine 
cable joint is submerged for cooling. 

Jointless Conductor.— A conductor in 
a single length and without joint. 

Joulad. — A term proposed for joule. (Not 
in use.) 

Joule. — (1) A volt-coulomb or unit of 
electric energy or work. (2) The amount 
of electric work required to raise the 
potential of one coulomb of electricity 
one A T olt. (3) Ten million ergs. 

Joule Effect. — The heating effect pro- 
duced by the passage of an electric cur- 
rent through a conductor arising from 
its resistance only. 

Joulean Effect. — A word sometimes used 
for joule effect. 

Joule Meter. — (1) Any apparatus capable 
of measuring energy in joules. (2) An 
energy meter, as distinguished from a 
wattmeter. 

Joule-Per-Second.— A unit of activity, 



equal to the expenditure of one joule in 
each second. 

Joule's Cylindrical Electro-Magnet.— 

An electro-magnet provided with a hol- 
low cylindrical core. 

Joule's Equivalent. — The mechanical 
equivalent of heat. 

Joule's Law. — The heating power of a 
current is proportional to the product of 
the square of its strength and the resist- 
ance of the circuit through which it 
passes. 

Journal. — That portion of a shaft which 
revolves on a bearing. 

Journal Friction. — Friction produced by 
the rotation of a shaft on a bearing. 

Jumper. — A temporary shunt or short cir- 
cuit put around a source, lamp or receptive 
device on a series-connected circuit, to en- 
able it to be readily removed or repaired. 

Jump Spark. — A disruptive spark ob- 
tained between two opposed conducting 
surfaces, as distinguished from a spark 
obtained by or following a wiping contact. 

Jump-Spark Burner. — A term some- 
times applied to a gas burner in which the 
issuing jet is ignited by means of a high- 
tension spark obtained between two op- 
posed points. 

Junction. — In telephony, a wire or circuit 
connecting two exchanges. 

Junction Board. — In telephony, a switch- 
board at which junction wires terminate. 

Junction Box. — A moisture-proof box 
provided in a system of underground con- 
ductors to receive the terminals of the 
feeders, and in which connection is made 
between the feeders and the mains, and 
through which the current is distributed 
to the individual consumers. 

Junction Calls. — Telephonic calls arriving 
on a junction line. 

Junction Circuit. — In telephony, a line 
connecting a trunk circuit with a local 
subscriber. 

Junction Line. — (1) In telephony, a junc- 
tion. (2) A line connecting two telephone 
exchanges. 

Junction-Line Plug.— In a central tele- 
phone exchange, a plug connected with a 
junction line. 

Junction Lines. — Lines connecting two 
or more telephone exchanges, as dis- 
tinguished from subscribers' lines. 

Junction Operator. — In telephony, an 
operator at a junction board. 



J 1111. 



821 



[Key. 



Junction Surface of Voltaic Cell.— The 
contact surface between the elements of 
a voltaic cell and the electrolyte. 

Junction Wires.— Junction lines. 



Junction Working. — Inter-e xchange 

telephone working. 
Just Non-Oscillatory Discharge.— A 

discharge which is just non-oscillatory. 



K 



K. — A symbol for electrostatic capacity. 

K. — A symbol for moment of inertia. 

h. — A symbol for magnetic susceptibility. 

K. C. C. — A contraction for cathodic clos- 
ure contraction. 

K. D. C. — A contraction for cathodic dura- 
tion contraction. 

K. W. — A contraction for kilowatt. 
kg. — An abbreviation for kilogramme, a 
practical unit of mass. 

kg : cm 2 . — An abbreviation for kilo- 
gramme-per-square-centimetre, a practi- 
cal unit of pressure. 

kgm. — An abbreviation for kilogramme- 
metre, a practical unit of the moment of 
a couple or of work. 

kgm : s. — An abbreviation proposed for 
kilogramme-meter-per-second, a practical 
unit of power. 

KB. — A contraction for the total capacity 
of a telegraph or telephone wire or con- 
ductor, multiplied by its total resistance. 

KR Law. — (1) A well-recognized law that 
the limiting speed of signalling through 
a submarine cable, assuming a given re- 
ceiving and sending apparatus in uniform 
adjustment, varies inversely as the KR of 
the cable. (2) A generalization claimed 
as a law by some, but denied by most, 
which assigns the distance through which 
intelligible telephonic communication can 
be carried, to cases where the product of 
K, the capacity of the telephone circuit 
and R, its resistance, does not exceed a 
certain value. 

Kaolin. — A variety of white clay some- 
times employed for insulating purposes. 

Kapp Lines. — A term proposed for unit 
lines of magnetic force or flux. 

Karsten's Figures. — A name sometimes 
applied to electric breath figures. 

Kartavert. — A variety of insulating mate- 
rial. 

Katalysis. — An orthography sometimes 
employed for catalysis. 

Katelectrotonus. — Catelectrotonus. 

Kathelectrotonic State.— The cathelec- 
trotonic state. 



Kathelectrotonus Zone.— Cathelectro- 
tonic zone. 

Kathelectrotonus. — Cathelectrotonus. 

Kathetometer.— A cathetometer. 

Kathion. — A cathion. 

Kathodal.— Cathodal. 

Kathode. — A cathode. 

Kathodic— Cathodic. 

Kathodic Electro-Diagnostic Reac- 
tions. — Cathodic electro-diagnostic reac- 
tions. 

Kathodic Rays. — Cathodic rays. 

Kations.— Cathions. 

" Keeper " of Inductor Alternator.— A 
word sometimes employed for inductor. 

Keeper of Magnet. — A mass of soft iron 
applied to the poles of a magnet, and 
through which its magnetic flux passes. 

Kelvin. — (1) A word proposed, but not 
adopted, for a kilowatt-hour or one thous- 
and watt hours. (2) A word proposed for 
the Board of Trade unit. 

Kelvin Balance. — A form of electro-dyna- 
mometer balance designed by Lord Kelvin. 

Kerite. — A variety of insulating material. 

Kerite Tape. — A kerite-covered insulating 
tape. 

Kerr Effect. — The elliptical polarization 
of a beam of plane polarized light, pro- 
duced by its passage across an electrized 
dielectric. 

Key-Board. — Any board to which electric 
keys or switches are connected. 

Key-Board Transmitter. — The trans- 
mitter employed in a step-by-step or print- 
ing telegraph. 

Key Lamp-Socket. — A lamp-socket pro- 
vided with a key for lighting or extin- 
guishing the lamp. 

Keyless. — Devoid of a key. 

Keyless Fire- Alarm Box. — A fire-alarm 
box covered with a glass window which 
requires to be broken in order to send the 
alarm. 

Keyless Lamp-Socket.— A lamp-socket 
unprovided with a key, and whose lamp, 
therefore, requires to be lighted and ex- 
tinguished by a switch placed elsewhere. 



Key.] 



822 



[Kno, 



Keyless Wall-Socket.— A socket placed 
on a wall, provided for the reception of a. 
plug switch for the introduction of a 
lamp. 

Kick. — A recoil. 

Kick of Coil. — The discharge from an elec- 
tromagnetic coil. 

Kick of Relay. — An impulse communicat- 
ed to the tongue of a relay by a discharge 
from the line. 

Kicking Coil. — A choking coil. 

Kicks. — In telegraphy, sudden impulses of 
a mirror spot, or siphon, due to a momen- 
tary earth current or discharge. 

Kilerg. — One thousand ergs. 

Killing Wire. — (1) A method formerly ad- 
opted for removing kinks, bends and flaws 
in iron by stretching it on the line in long 
lengths. (2) A method of straightening 
wire by subjecting it to tension. (3) A 
term sometimes applied to loss of elasti- 
city of contact springs of switches, due to 
their over-heating by the current. 

Kilo. — A prefix for one thousand times. 

Kilo-Ampere. — One thousand amperes. 

Kilo-Ampere Balance. — A balance form 
of ammeter which measures thousands of 
amperes. 

Kilo-Dyne. — One thousand dynes. 

Kilo-Erg. — One thousand ergs. 

Kilo-G-auss. — One thousand gausses. 

Kilogramme. — One thousand grammes, or 
2.2046 pounds avoirdupois. 

Kilogramme-Metre. — A unit of work 
equal at Washington, D.C., to 9.81 multi- 
plied by 10 7 ergs. 

Kilo-Henry. — One thousand henrys. 

Kilo- Joule. — One thousand joules. 

Kilo-Lines. — One thousand lines of force. 

Kilometre. — One thousand metres. 

Kilometric Capacity of Cable.— The ca- 
pacity of a cable in micro-farads per kilo- 
metre. 

Kilometric Insulation of Cable.— The 
insulation of a cable measured in meg- 
ohm-kilometres, or the average insulation 
of one kilometre in megohms. 

Kilo-Volt.— One thousand volts. 

Kilo-Watt.— One thousand watts. 

Kilo- Watt-Hour. — (1) The amount of 
work equal to that performed by an activ- 
ity of one kilowatt maintained steadily 
for one hour. (2) An amount of work 
equal to 3.600,000 joules. 

Kilo-Watt Hour Meter.— A form of re- 
cording watt-meter. 

Kilo- Weber. — One thousand webers. 



Kine. — A unit of velocity, proposed by the 
British Association, equal to a centimetre- 
per-second. 

Kinematics. — That branch of science 
which treats of motion, irrespective of 
the mass moved, or of the forces which 
produce or oppose the motion. 

Kinetic Energy. — Energy producing mo- 
tion, as distinguished from potential 
energy, or energy capable of producing 
motion. 

Kinetic Induction.— Dynamic or mutual 
induction. 

Kinetic Theory of Matter. — A theory 
which assumes that the molecules of mat- 
ter are in a constant state of motion or 
vibration towards or from one another, in 
paths that lie within the spheres of their 
mutual attractions or repulsions. 

Kinetics. — That branch of dynamics 
which treats of the action of forces in 
producing or modifying motion. 

Kinetoscope. — A means for obtaining the 
effect of moving objects by means of a 
rapid succession of suitable pictures. 

Kinetograph. — (1) A term at one time 
applied to a device proposed for the simul- 
taneous reproduction of a distant stage 
and its actors under circumstances such 
that the actors can be heard at any dis- 
tance from the theatre. (2) An apparatus 
for reproducing on a screen the image of 
a moving object. 

KirchofFs Laws.— The Laws for the pres- 
sures and currents in branched or divided 
circuits. 

Kneading Tools.— Tools for shaping hot 
gutta-percha laid on a joint between gut- 
ta-percha covered wires. 

Knife-Break Switch. — A knife switch. 

Knife-Edge Suspension.— The suspen- 
sion of a needle or system on knife-edges, 
supported on steel or agate plates. 

Knife-Edge Switch. — A term sometimes 
used for knife-switch. 

Knife-Switch.— (1) A switch which is 
opened or closed by the motion of a knife 
contact between parallel contact plates. 
(2) A knife-edge switch or knife switch. 

Knob Insulator. — An insulator shaped 
like a knob and divided into two parts 
suitable for supporting a single wire when 
clamped together by its supporting 
screw. 

Knot. — (1) A nautical mile, or 6087 feet. 
(2) A length equal to one minute of arc in 
terrestrial latitude. (3) A unit of velocity 
at sea equal to one naut per hour, ob- 



Kno. 



823 



[Lam, 



tained from an observation of a knotted 
log-cord thrown overboard. 

Knot-Pound. — A standard of conductivi- 
ty of copper referred to a length of one 
knot and a conductor weight of one 
pound, and sometimes employed* in sub- 
marine telegraphy. 

Kohlrausch's Law. — In electrolytic con- 
duction, the rate of motion of each atom 
in a given liquid is independent of the 
element with which it may have been 
combined. 

Krizik's Bars or Cores.— Iron bars or 



cores of various shapes, provided for sole- 
noids, in which the distribution of the 
metal is so proportioned as to ensure a 
nearly uniform attraction or pull in dif- 
ferent positions of the solenoid. 

Kruss' Optical Scale.— A scale employed 
for measuring the height of a flame. 

Kyanized. — Subjected to the kyanizing 
process. 

Kyanizing. — A process employed for the 
preservation of wooden telegraph poles, 
or railroad ties or sleepers, by injecting a 
solution of corrosive sublimate into the 
pores of the wood. 



Ij. — A symbol for coefficient of inductance. 

L. — A contraction for length. 

L. — A symbol for the coefficient of induc- 
tance or self-induction. (Partly inter- 
national notation.) 

L m . — A symbol proposed for coefficient of 
mutuaWnduction, or mutual inductance. 

L s . — A symbol proposed for coefficient of 
self-induction, or self-inductance. 

Labile Galvanization.— A term employed 
in electro-therapeutics, in contra-distinc- 
tion to stabile galvanization, to designate 
the method of applying the current by 
keeping one electrode at rest, in firm con- 
tact with one part of the body, and con- 
necting the other electrode to a sponge 
which is moved over the parts of the 
body that are to be treated. 

Lag.— (1) Falling behind. (2) To fall be- 
hind. 

Lag of Motor Brushes. — A movement of 
the brushes of a motor to a position on 
the commutator, in the opposite direction 
to its rotation, in order to obtain freedom 
from sparking. 

Lag of Resultant Flux.— The displace- 
ment in phase of the magnetic flux in an 
induction motor behind the impressed 
magneto-motive force. 

Lagging Electromotive Force.— An 
eleptromotive force or component of elec- 
tromotive force lagging behind a current 
or flux. 

Lagging Current.— A periodic current 
lagging behind the impressed electromo- 
tive force which produces it. 

Lagging of Current. — An alternating 
current which is retarded in phase be- 
hind the pressure which produces it. 

Lagging of Magnetization.— (1) A re- 



tardation in the magnetization as com- 
pared with the magnetizing electromotive 
force. (2) A cyclic retardation of mag- 
netization in a transformer due to hys- 
teresis. 

Lambert's Discharge Key.— A highly 
insulated form of double-contact key, 
used in testing. 

Lamellar. — Composed of parallel plates or 
laminae. 

Lamellar Distribution of Magnetism. 

(1) The distribution of magnetism in 
magnetic shells. (2) Such a distribution 
of magnetism in a thin plate that the 
magnetized particles are arranged with 
their greatest lengths in the direction of 
the thickness of the plate, so that all the 
poles are situated at or near the faces of 
the plate, and, consequently, the extent 
of such polar surfaces is great when com- 
pared with the thickness of the plate. 

Lamellar Magnet.— A magnet whose 
magnetism is characterized by lamellar 
distribution, 

Laminated. — Built up or composed of 
laminae. 

Laminated Core.— An iron core that has 
been sub-divided in planes parallel to its 
magnetic flux-paths, in order to avoid the 
injurious production of Foucault or eddy 
currents. 

Laminated Magnet. — A magnet provided 
with a laminated core. 

Laminating. — Sub-dividing into laminae. 

Lamination. — The sub-division of an iron 
core into laminae. 

Lamination of Armature Core.— The 
sub-division of the iron core of a dynamo 
or motor armature into a number of in- 



Lam.] 



824 



[Lam. 



sulated parallel strips or plates, for the 
purpose of avoiding eddy currents. 
Lamination of Conductors.— (1) The 
division of a conductor into a number of 
parallel strands or wires, for the purpose 
either of lessening the eddy currents pro- 
duced in its mass, or for reducing the 
skin effect when alternating currents are 
employed. (2) A stranded conductor. 

Lamp Adapter.— (1) A device which 
permits an electric lamp to replace an or- 
dinary gas burner on a gas bracket or 
chandelier. (2) A device which permits 
an electric lamp base of one manufacturer 
to be readily inserted in the socket of an- 
other manufacturer. 

Lamp Base. — The portion of an incandes- 
cent lamp chamber through which the 
leading-in wires are passed, provided with 
two metallic plates or parts, suitably in- 
sulated from one another, and electrically 
connected to the ends of the leading-in 
wires. 

Lamp Bracket, Electric— A device 
similar to that employed for a gas burner, 
suitable for the support of an incandes- 
cent lamp. 

Lamp Bulb. — The chamber or globe in 
which the filament of an incandescent 
lamp is placed. 

Lamp Cap. — The base of an incandescent 
lamp. 

Lamp Chamber.— The bulb of an incan- 
descent lamp. 

Lamp Circuit. — A circuit containing an 
electric lamp or lamps. 

Lamp Clamp. — A suitable grip for hold- 
ing the rod that supports the electrode of 
an arc-lamp. 

Lamp Contacts. — Metallic plates or rings 
placed in an incandescent lamp base, and 
connected to the terminals of the filament. 

Lamp Cord. — A flexible cord containing 
two separately insulated wires suitable 
for use in connection with an incandescent 
lamp. 

Lamp Cut-Out. — (1) A device so arranged 
as to automatically cut a series-con- 
nected arc-lamp out of the circuit, as soon 
as the carbons are entirely consumed. 
(2) A safety catch or safety fuse con- 
nected with the circuit of a multiple-con- 
nected incandescent lamp. 

Lamp Dimmer.— A reactive coil, em- 
ployed on an alternating circuit for the 
purpose of varying the intensity of incan- 
descent lights connected with such 
circuit. 

Lamp Efficiency.— (1) Commonly, but 



illogically. the watts consumed by a lamp 
per candle-power delivered. (2) More 
nearly correctly, the reciprocal of this ; or 
the number of candles obtained from an 
incandescent lamp per w T att supplied to 
it. t 

Lamp Feet. — (1) In a conducting loop, cir- 
cuit, or system, the product of the number 
of lamps supplied and the distance at 
which they are supplied ; each lamp being 
multiplied by its distance, and the sum of 
such products being taken. (2) A quan- 
tity sometimes used in computing dis- 
tribution systems of electric lighting. 

Lamp Filament.— The filament of an in- 
candescent lamp. 

Lamp Fittings.— (1) Thesockets, holders, 
brackets, etc., required for holding, or 
supporting, incandescent electric lamps. 
(2) Lamp fixtures. 

Lamp Frame.— The frame of an arc-lamp 
provided for the support of the feeding 
mechanism, globe, etc. 

Lamp Hanger.— A device provided for 
the suspension of an arc-lamp. 

Lamp Hood. — A hood employed to protect 
an arc-lamp from rain or snow, and gen- 
erally so arranged as to throw its light in 
a downward direction. 

Lamp-Hour.— (1) Such a service of 
electric current as is required to main- 
tain one electric lamp during one hour. 
(2) Such a quantity of electricity, or of 
electric energy, as will maintain one 
standard lamp in normal operation for 
one hour. 

Lamp Indicator. — (1) An apparatus em- 
ployed in a central station to indicate the 
presence of the proper voltage, or poten- 
tial difference, on the mains. (2) A 
lamp employed on a telephone switch- 
board to indicate when the subscriber is 
calling, or when he has rung off. (3) A 
pilot lamp. (4) Any indicating apparatus 
employing an electric lamp as signalling 
device. 

Lamp Pendant. — A flexible cord em- 
ployed for the support of a pendant 
lamp. 

Lamp Pillar. — (1) A pillar supporting one 
or more lamps. (2) A lamp post. 

Lamp Posts. — Posts provided for the sup- 
port of lamps. 

Lamp Protector. — A lamp hood, cover or 
guard. 

Lamp Receptacle.— (1) A lamp socket 
or holder. (2) A receptacle for a flex- 
ible connection leading to a lamp. 

Lamp Rod,— (1) The rod provided in an 



Lam.] 



825 



[Law, 



ordinary arc-lamp for the support of the 
positive carbon. (2) In a focussing 
lamp, the rods provided for the support 
of the two carbons. 

Lamp Socket. — A support provided for 
the reception of an incandescent lamp, so 
arranged that the introduction of the 
lamp therein, automatically connects the 
lamp terminals with the terminals of the 
supply wires. 

Lamp-Socket Rheostat. — A regulable re- 
sistance placed in the socket of an incan- 
descent lamp for the purpose of altering 
the quantity of light it emits. 

Lamp -Socket Switch.— (1) A switch 
placed in the socket of an incandescent 
lamp, provided for lighting and extin- 
guishing the lamp. (2) A lamp-socket ke}\ 

Lamp Switches. — Switches placed in the 
circuit of a group of incandescent lamps, 
either in the branches, or in the mains, 
for the purpose of simultaneously lighting 
or extinguishing a number of lamps. 

Land Line. — (1) A telegraph line on land, 
either aerial or buried, as distinguished 
from a submarine cable. (2) An aerial 
telegraph line. (3) That portion of a sub- 

« marine-cable circuit which extends over 
the land. 

Lantern Lamp. — An incandescent lamp 
provided with a lantern-shaped chamber 
surrounding the lamp chamber. 

Lantern Projector.— A focussing arc-lamp 
employed in connection with a projecting 
apparatus. 

Lap Joint. — (1) The joint effected by over- 
lapping short portions near the ends of 
the things to be joined, and securing 
them to each other while in that posi- 
tion. (2) A joint between the ends of two 
conducting w T ires in which the two ends 
after being laid together, side by side, are 
lapped firmly together by a piece of separ- 
ate wire. 

Lap-Joint for Wires. — A joint between 
two wires, made by over-lapping their 
ends and subsequently soldering. 

Lap Winding. — A winding for a drum 
armature, in which the successive con- 
ducting loops are arranged on the surface 
of the armature over-lapping one an- 
other. 

Large Calorie. — (1) A term sometimes used 
for the great calorie. (2) A kilogramme- 
degree-centigrade. (3) One thousand 
lesser calories. 

Latent. — Hidden, concealed. 

Latent Electricity. — A term formerly 
applied to bound electricity. 

Lateral. — An offset from a conduit system 



for connecting services with the con- 
ductors of a conduit. 

Lateral Bracket. — A form of bracket for 
running wires from corner to corner of 
buildings, and for supporting an insulator 
in an upright position. 

Lateral Discharge.— (1) A Leyden-jar or 
other impulsive discharge occurring be- 
tween parts of the circuit not in the 
direct path of the main discharge. (2) A 
discharge occurring through an alterna- 
tive path. 

Lateral Induction. — (1) Induction occur- 
ring between closely -approached portions 
of a circuit, through which an impulsive 
discharge is passing. (2) The induction 
produced by an impulsive discharge as 
manifested in a lateral discharge. 

Lateral Magnetic-Leakage. — (1) The 
failure of magnetc flux to pass in ap- 
proximately parallel paths through a bar 
of iron or other magnetizable material, 
which has come to rest in a field in which 
it is free to move. (2) The escape of 
magnetic flux from the sides of a bar 
magnet, or other similar magnet, instead 
of from the poles at its ends. 

Lattice Pole. — A form of structural-iron 
pole designed for the support of overhead 
wires or conductors, made in the form of 
a light, strong lattice. 

Lattice Work of Pole.— A composite 
pole whose upper portion consists of 
structural lattice work, employed in cases 
where the stresses produced on the top of 
the pole are excessive by reason of the 
weight of the cables, or the number of 
lines or aerial wires supported thereon. 

Launch, Electric. — A launch whose mo- 
tive power is electric. 

Law. — (1) In physics, any relation existing 
between natural phenomena and their 
causes. (2) The invariable manner in 
which physical causes produce their 
effects. (3) Any observed relation of 
sequences in the universe. 

Law of Electro-Chemical Equiva- 
lence. — The amount of electrolytic libera- 
tion produced by an electric current 
passed through various chemical sub- 
stances is proportional to the chemical 
equivalent of each substance, that is, to 
its atomic weight divided by its valency. 

Law of Illumination. — The illumination 
produced by a single-point source of light, 
varies inversely as the square of the dis- 
tance from that source. 

Law of Ohm. — (1) The law of non-varying 
current strength in a circuit not subject 
to variation. (2) Ohm's law. 



Law.] 



826 



[Lea. 



Law of Volta.— (1) The law of contact 
series. (2) Volta's law. 

Laws of Becquerel. — Laws for the mag- 
neto-optic rotation of the plane of polari- 
zation. 

Laws of Coulomb.— Laws for the force 
of attraction and repulsion existing be- 
tween charged bodies, or between neigh- 
boring magnet poles. 

Laws of Faraday. — Laws of electrolytic 
decomposition. 

Laws of Joule. — Laws expressing the de- 
velopment of heat in a circuit by an 
electric current. 

Laws of Reflection.— (1). The angle of in- 
cidence is equal to the angle of reflection. 
(2) Both the incident and the reflected 
rays lie in the same plane. 

Lay. — The helical disposition of wires in a 
strand or sheath, in which each wire 
makes a complete revolution about the 
axis. 

Lay Torpedo. — A moving torpedo, in 
which the motive power is either carbonic 
acid gas or compressed air, and the guid- 
ing power electricity. 

Layer. — A name sometimes applied to an 
electro-plating deposit. 

Lay-Out of Cable in Tank.— (1) The 

starting of a new flake in coiling a cable 
in a tank, by proceeding from the eye at 
the end of the finished flake, directly out- 
ward to the edge of the tank. (2) That 
part of a cable which connects the inside 
of one flake with the outside of the suc- 
ceeding flake in a cable tank. 

Laying-Up Cables. — Placing or disposing 
separate cables or conductors in a bunched 
cable. 

Lead. — (1) An insulated conductor leading 
to or from an electric source. (2) In 
telegraphy, an insulated conductor leading 
to an instrument, battery, circuit, or star 
tion. (3) In a multiple or parallel-con- 
nected circuit, a conductor or main con- 
nected to the positive terminal of the 
source. (4) In a system of electric distri- 
bution, an insulated conductor leading to 
a main, feeder, source, station, testing 
apparatus, or device. (5) A connecting 
wire. 

Lead Accumulator. — An accumulator or 
storage cell which has been formed from 
two plates of lead immersed in dilute 
sulphuric acid. 

Lead Burning. — Effecting a metallic 
junction between two lead plates or strips 
Iby partially fusing them together. 

Lead-Covered Conductors.— Insulated 
conductors sheathed in lead. 



Lead-Encased Cable. — A cable provided 
with a sheathing or coating of lead on its 
external surface. 

Lead of Brushes of Dynamo-Electric 
Generator. — An angular deviation from 
the normal position, forwards, or in the 
direction of rotation of the armature, 
which is given to the brushes on the 
commutator, in order to obtain sparkless 
commutation. 

Lead of Current. — An advance in the 
phase of an alternating current beyond 
that of the electromotive force producing 
the current. 

Lead of Motor Brushes.— The angular 
displacement from the normal position 
in the direction contrary to that of the 
rotation of the armature, which it is 
necessary to give the brushes on an elec- 
tric motor, when its load is increased, in 
order to obtain freedom from sparking. 

Lead Scoring Tool.— A tool for readily 
scoring the surface of a lead-covered 
cable, for the purpose of obtaining a clean 
surface preparatory to making a joint. 

Lead Sheathing. — The coating of lead 
placed on the outside of a lead-covered 
cable. 

Lead Sleeve. — A lead tube provided for 
making a joint in a lead-covered cable. 

Lead-Tin Alloys. — Alloys of lead and tin, 
of low melting point, employed for safety 
fuses. 

Lead Tree. — An arborescent deposit of 
lead obtained by the electrolysis of a solu- 
tion of a lead salt. 

Lead Voltameter. — A voltameter consist- 
ing of lead electrodes immersed in a dilute 
solution of sulphuric acid and water. 

Leaded Cable. — A cable provided with a 
lead sheathing. 

Leading Current. — An alternating-cur- 
rent wave or component, in advance of 
the electromotive force producing it. 

Leading Edge of Pole-Pieces of Arma- 
ture. — Those edges or terminals of the 
field-magnet pole-pieces which the arma- 
ture is approaching in its rotation. 

Leading Horn of Pole-Pieces of Dy- 
namo. — Those edges or terminals of the 
field-magnet pole-pieces towards which 
the armature of a" dynamo-electric ma- 
chine is carried during its rotation. 

Leading-In Insulator.— The insulator 
provided for the support of the wires 
leading into a building from an aerial cir- 
cuit. 

Leading-In Tube.— (1) A tube of insulat- 
ing material provided for the reception 



Lea.] 



)2t 



[Let. 



of the leading-in wires in a building. 
(2) An insulating tube. 

Leading-In Wires.— (1) The wires that 
pass from an aerial circuit into a house or 
building. (2) The wires or conductors 
which lead the current through an in- 
candescent electric lamp; i.e., into and 
out of a lamp. (3) Wires leading a cir- 
'cuit into a house, room, box, or apparatus. 

Leading Pole of Dynamo or Motor. — 
The pole of a dynamo or motor approached 
by points on the surface of the revolving 
armature which lie between the poles at 
any instant. 

Leading-Up "Wires. — Wires employed 
for raising an aerial cable to the cable 
hangers. 

Leads. — (1) In a system of parallel distri- 
bution, the conductors connected to the 
positive and negative terminals of a 
source. (2) Generally, the conductors in 
any system of electric distribution. (3) 
Conductors which lead the current to or 
from any source, circuit or device. (4) 
In electric testing the insulating conduc- 
tors leading the testing current to the cir- 
cuit or conductor tested. 

Leak. — (1) Any loss or escape by leaking. 
(2) The point or place where a leak occurs. 

Leakage. — A loss or escape by leaking. 

Leakage Conductance.— Insulation con- 
ductance, or the reciprocal of the insula- 
tion resistance. 

Leakage Conductor.— (1) A conductor 
placed on a telegraphic circuit for the 
purpose of preventing the disturbing ef- 
fects of leakage into a neighboring line 
by providing a direct path for such leak- 
age to the earth. (2) A conductor placed 
on a telegraphic line for the purpose of 
lessening the retardation of the line by 
assisting in its discharge. 

Leakage Current of Primary.— (1) The 
magnetizing current which flows into the 
primary circuit of a transformer when 
the secondary circuit is open (2) A cur- 
rent employed in magnetizing only, as 
distinguished from a current usefully 
transformed. 

Leakage Current of Transformer.— (1) 

The current which flows into the primary 
circuit of a transformer when the secon- 
dary circuit is opened. (2) The mag- 
netizing current. 

Leakage Drop.— The drop produced in a 
circuit by leakage. 

Leakage, Electric— The gradual dissipa- 
tion of a charge or current due to insuf- 
ficient insulation. 



Leakage Factor. — In a dynamo-electric 
machine, the ratio of the total flux, which 
passes through the field-magnet cores of 
a dynamo or motor, to the total useful flux 
passing from them through the armature. 

Leakage Flux.— (1) That portion of the 
field flux which does not pass through the 
armature of a dynamo or motor, and 
which, therefore, produces no useful ef- 
fect. (2) The stray flux, or that from 
which no useful effect is obtained. 

Leakage Indicator.— (1) A magnetic ex- 
plorer. (2) An electric testing apparatus 
for revealing the presence of leakage in 
any circuit or system. 

Leakage Interference. — Interference be- 
tween two or more circuits due to their 
mutual leakage. 

Leakage Magnetic Resistance.— The re- 
luctance to leakage magnetic flux. 

Leakage Method of Measuring Insu- 
lation. — A method of measuring the in- 
sulation of a conductor or condenser by 
determining the rate at which it loses 
charge by leakage. 

Leakage Paths. — The paths traversed by 
leakage magnetic flux. 

Leakance. — A term proposed for leakage- 
conductance in a circuit. 

Leclanche's Voltaic Cell. — A zinc-car- 
bon couple whose elements are used in 
connection with a solution of sal-ammo- 
niac, and a quantity of finely divided 
black oxide of manganese surrounding 
the carbon. 

Lecture Galvanometer.— A form of gal- 
vanometer suitable for showing the 
movements of a galvanometer needle to 
an audience at a considerable distance 
from the instrument. 

Left-Hand Trolley-Frog.— A trolley- 
frog so arranged as to switcli a car to the 
left. 

Left-Hand Trolley-Switch.— A switch 
arranged to divert a car to the left of a 
main line. 

Left-Handed Armature-Windings. — 
Armature windings applied to the core 
in a left-handed or sinistrorsal helix. 

Left-Handed Dynamo. — A dynamo 
which runs left-handedly, or counter- 
clockwise, when regarded from the pulley 
end. 

Left-Handed Helix.— (1) A left-handed 
solenoid. (2) A helix wound left-hand- 
edly, or counter-clockwise. 

Left-Handed Motor. — A motor which 
runs left-handedly. or counter-clockwise, 
when regarded from the pulley end. 



Lef.] 



828 



[Ley. 



Left-Handed Rotation. — A rotation in a 
positive or counter-clockwise direction. 

Left - Handed Solenoid.— A solenoid 
whose winding is left-handed, or counter- 
clockwise. 

Left-Handed Spiral.— A left-handed 
helix. 

Left-Handed Winding.— The winding of 
a solenoid or helix in a counter-clockwise 
direction. 

Leg. — In a system of telephonic exchange, 
where a ground-return is used, a single 
wire ; or, where a metallic circuit is em- 
ployed, two wires, provided for connect- 
ing the subscriber with the main switch- 
board, so that any subscriber may be 
placed directly in circuit with two or 
more other subscribers. 

Leg Key. — A Morse telegraphic key having 
long screw in its base for passing through 
a table. 

Leg of Circuit.— (1) A branch of a bifur- 
cated or divided circuit. (2) A loop or 
offset in a series circuit. 

Leg of Electro-Magnet.— One of the 
cores of an electro-magnet. 

Legal Earth Quadrant. — (1) A practical 
unit of inductance as defined by the Elec- 
trical Congress of 1884, at Paris, and as 
distinguished from the true earth quad- 
rant. (2) The legal quadrant. 

Legal Ohm. — (1) An ohm whose value is 
in accordance with the definition of the 
Electrical Congress of 1884, in Paris. (2) 
The resistance of a uniform column of 
mercury one square millimetre in area 
of cross-section, and 106 centimetres in 
length, at the temperature of 0° Cent., or 
32° Fahr. (3) The concrete standard ohm 
as defined by the Electrical Congress of 
1884, at Paris, as distinguished either from 
the B. A. ohm, the true ohm, or the In- 
ternational ohm. 

Legal Quadrant. — (1) The legal earth 
quadrant. (2) The unit of self-induction 
based upon the definitions of the Electrical 
Congress of 1884, in Paris. 

Legged. — Placed in a circuit by means of 
a leg. 

Legging Key-Board.— A key-board em- 
ployed for the purpose of legging an oper- 
ator into a circuit containing two or more 
subscribers. 

Legless Key. — (1) A name sometimes given 
to a Morse telegraphic key provided with 
a flat base. (2) A self-closing key. 

Length of Spark. — The air distance trav- 
ersed by a disruptive discharge. 

Lenard Effect. — The effect produced by 



the Lenard Rays, in causing fluorescence, 
and in passing through some substances 
that are opaque to light. 

Lenard Rays.— The peculiar radiation 
emitted from that external portion of a 
Lenard tube that is directly opposite the 
cathode. 

Lenard Tube. — A form of high-vacuum 
tube provided with an aluminium plate, 
hermetically sealed in that portion of the 
wall of the tube lying directly opposite 
the cathode, and employed for producing 
Lenard rays. 

Lens. — A medium, transparent to radiant 
energy, provided with a curved face or 
faces, and employed to bring a beam or 
pencil of light to a single point or focus. 

Lens Lamp. — A.n incandescent lamp pro- 
vided with a small lens hermetically fixed 
in a portion of its wall, opposite a suitably 
placed reflector. 

Lens-Mirror Projector. — A form of pro- 
jector whose operation is dependent on 
the combined action of a mirror and a lens. 

Lenz's Laws. — Laws for determining the 
direction of currents produced by electro- 
dynamic induction. 

Lesser Calorie. — (1) The small calorie. 
(2) The therm. (3) The water-gramme- 
degree-centigrade. 

Letter-Box, Electric— A device that 
announces the deposit of a letter in a box 
by the ringing of a bell, or by the moving 
of a needle or index. 

Letter Printing Instrument. — A type- 
printing telegraphic instrument. 

Level, Electric. — An equipotential elec- 
tric surface. 

Level of Earth, Electric— A term some- 
times employed for the potential of the 
earth . 

Lever Brake for Car. — A form of car 
brake operated by means of a brake 
handle. 

Lever Hook. — (1) The hook in an auto- 
matic telephone switch on which a tele- 
phone receiver is hung when not in use. 
(2) A contact lever provided with a hook 
for supporting a telephone. 

Lever Switch. — (1) A switch mounted 
upon a fulcrum axis like a lever. (2) A 
switch operated by the movements of a 
lever. (3) A telephone switch of a multi- 
ple telej:>hone switch-board, operated by 
a lever. 

Ley den- Jar. — A condenser in the form of 
a jar, in which the metallic coatings are 
placed opposite each other respectively on 
the outside and inside of the jar. 



Ley.] 



829 



[Lim, 



Leyden-Jar Battery. — The combination 
of a number of separate Leyden jars so as 
to act as a single jar. 

Leyden-Jar Discharge.— (1) The dis- 
ruptive discharge produced by a Leyden 
jar. (2) A name sometimes given to an 
oscillatory discharge. 

Ley die Resistance. — A term proposed for 
the resistance offered by various metallic 
circuits to condenser discharges. 

Lichtenberg's Dust-Figures.— Figures 
obtained by writing on a sheet of shellac 
with the knob of a charged Leyden jar, 
and then sprinkling over the sheet, dried, 
powdered sulphur and red lead, which 
have been previously mixed together and 
are thereby rendered respectively nega- 
tive and positive. 

Lichtenberg's Electric Figures.— A 
term sometimes applied to Lichtenberg's 
dust-figures. 

Life Curve of Incandescent Electric 
Lamp. — A curve in which the life of an 
incandescent electric lamp is represented 
by means of abscissae and ordinates that 
are respectively equal to the life in hours 
and the candle-power at constant pressure, 
or the pressure at constant candle-power. 

Life of Electric Incandescent Lamp.— 
The number of hours that an incandes- 
cent electric lamp will continue to fur- 
nish a good commercial light when oper- 
ated at normal pressure. 

Lift, Electric— An electrically operated 
lift or elevator. 

Light. — (1) That particular form of radiant 
energy by means of which objects are 
rendered visible. (2) The flow or flux of 
light emitted from a luminous source. 

Light Bath, Electric— A form of electro- 
therapeutic bath in which the patient is 
exposed to the radiation of a number of 
incandescent lamps. 

Light Cell. — A term sometimes employed 
for a photo-electric cell. 

Light, Electric— Light produced by the 
action of electric energy. 

Light Escape. — A partial ground or 
earth. 

Light-House Illumination, Electric. — 

The application of the electric arc-light 
to light-houses. 

Light Indicator of Railroad Signal. — 
A device by means of which an indica- 
tion is given electrically, at a distance, as 
to whether a signal lamp is lighted or not. 

Light Load of Machine.— A partial load, 
or a load which is small by comparison 
with the capacity of the machine. 



Light Cable, Electric— A cable em- 
ployed for furnishing the current required 
for the maintenance of electric lights. 

Lighting Circuits „— Any electric circuit 
for the distribution of light. 

Lightning. — A spark or discharge that 
results from the disruptive discharge of a 
cloud to the ground, or to a neighboring 
cloud. 

Lightning Arrester. — A device by means 
of which the apparatus placed in any 
electric circuit is protected from the de- 
structive effects of a flash or discharge of 
lightning. 

Lightning - Arrester Board. — The 
board to which the lightning arresters of 
a system of telephonic or telegraphic 
communication are connected. 

Lightning-Arrester Earth.— The earth 
provided for the grounding of the earth- 
plate of a lightning arrester. 

Lightning Bolt. — A lightning flaeh or dis- 
charge. 

Lightning Conductor.— A lightning rod. 

Lightning Deviator. — A term sometimes 
used for lightning arrester. 

Lightning Discharger. — A term some- 
times used for lightning protector. 

Lightning Flash.— A lightning discharge. 

Lightning Guard. — A term sometimes 
used for lightning rod. 

Lightning Jar. — A Ley den- jar whose 
coatings consist of metallic filings in the 
gaps between which an irregular series 
of sparks, somewhat resembling a light- 
ning flash, appear on the discharge of the 
jar. 

Lightning Rod. — A rod, strap, wire, or 
stranded cable, of good conducting mate- 
rial, placed on the outside of a house or 
other structure, in order to protect it 
from the effects of a lightning discharge. 

Lightning Rods for Ships.— A system of 
rods or conductors designed to afford 
electric protection for vessels at sea. 

Lightning Stroke. — (1) A disruptive dis- 
charge occurring between two oppositely 
charged clouds, or between a cloud and 
the earth. (2) A lightning flash. 

Lightning Tube. — A fulgurite. 

Lime Light. — A source of light obtained 
by the incandescence of a cylinder of 
lime under the influence of the oxy-hy- 
drogen blow-pipe. 

Limit Switch. — A small automatic switch 
on an electric streetcar, connected in series 
with the brake discs, and so arranged as 
to be capable of cutting out the fields of 



Lim.] 



830 



[Lin. 



both motors when the braeking current is 
excessive. 

Limiting Distance of Speech..— (1) The 
length of circuit, or the distance to which 
a circuit may be carried in a straight line, 
at which telephonic conversation is just 
practicable. (2) The limiting length of 
line to which telephonic speech can be 
carried successfully, depending upon the 
electric conditions of the circuit, and the 
nature of the apparatus employed. 

Limiting Speed of Cable.— The speed 
to which the transmission of signals 
through a cable is limited, by reason of its 
electrostatic capacity and resistance. 

Limiting Stop.— A stop set so as to limit 
the motion of an electrically vibrating or 
oscillating bar to any pre-determined 
extent. 

Limiting Temperature-Elevation .—A 
temperature elevation of any apparatus 
which is not to be exceeded during its 
prolonged operation. 

Line. — Generally, a wire or conductor 
connecting any distant points or stations. 

Line Adjuster. — An instrument employed 
for overcoming the effects of leakage on 
the adjustment of the relays in a tele- 
graphic circuit. 

Line Arrester. — The lightning arrester 
connected to a line or circuit. 

Line Circuit. — (1) The wires or other 
conductors in the main line of a tele- 
graphic or other circuit. (2) A trans- 
mission circuit for electric energy. 

Line Crosses. — Electric crosses occurring 
on lines. 

Line Crossing. — (1) The place where two 
overhead trolley conductors cross each 
other. (2) A metallic plate uniting the 
ends of trolley wires, wiiere one wire 
crosses another. 

Line Cross-Over.— (1) A trolley crossing. 
(2) A trolley cross-over. 

Line Drop. — In a telephone switchboard, 
an electro-magnetic drop connected to a 
line. 

Line Dynamometer. — A dynamometer 
employed during the erection of an over- 
head line, in order to determine whether 
it has been pulled up to its proper tension. 

Line Insulator. — An insulator employed 
for the support of an aerial line. 

Line Integral. — A continuous summing 
up of some instantaneous quantity exe- 
cuted or conducted along a continuous 
line. 

Line Jacks. — In a telephone switchboard, 
a jack connected to a line. 



Line of Least Sparking. The diameter 

of sparkless commutation. 
Line Peg. — A peg or plug in a switchboard 

connecting the line with translating 

devices or with another line. 

Line-Pressure Compensator.— A device 
for attachment to a voltmeter in an alter- 
nating-current system, whereby the volt- 
meter indications are compensated for 
the drop of pressure in the feeder, and 
are such as would be obtained if the 
instrument were directly connected to 
the mains. 

Line Reactance. — The reactance of a line 
conductor. 

Line Section of Electric Railroad.— 

Any part of a trolley, or other railroad 
line, so insulated from other parts as to 
permit of the separate control of its sup- 
ply of electric power. 

Line Selector. — A wire selector. 

Line Wire. — In telegraphy, the wire that 
connects the different stations with one 
another. 

Line-Wire Tier. — A tie wire of soft 
copper or soft iron employed for holding 
the line wire to the insulator. 

Lines of Electric-Displacement.— Lines 
of electric flux, along w T hich electric dis- 
placement takes place. 

Lines of Electric-Induction.— The lines 
along which electric induction takes 
place. 

Lines of Electrostatic-Flux.— The lines 
along which electrostatic flux passes. 

Lines of Electrostatic-Force.— (1) Lines 
of force produced in the neighborhood of 
a charged body by the presence of the 
charge. (2) Lines extending in the direc- 
tion in which the force of electrostatic 
attraction or repulsion acts. 

Lines of Inductive- Action.— Lines of 
electrostatic force. 

Lines of Magnetic-Force.— (1) Lines in 
which magnetic force acts. (2) Lines 
extending in the direction in which the 
force of magnetic attraction or repulsion 
acts. 

Lines of Magnetic-Induction.— (1) Mag- 
netic flux-paths. (2) The lines in which 
magnetic induction proceeds, 

Lines of Magnetization.— (1) A term 
sometimes applied for lines of magnetic 
induction. (2) A term sometimes applied 
to those portions of the lines of magnetic 
force which lie within the magnetized 
substance. 

Lineants. — A term proposed as a unit of 
magnetic flux in place of webers, and 



Lin.] 



831 



[Loc, 



equal to the pressants divided by the 
resistants, or to the magneto-motive force 
divided by the reluctance. (Not used.) 

Linear Capacity. — The quotient of the 
capacity of a line or conductor by its 
length. 

Linear Capacity of Cable. — The electro- 
static capacity of a cable per-unit-of- 
length. 

Linear Coefficient of Expansion.— The 
increase in a unit length of a substance 
when subjected to unit difference of tem- 
perature. 

Linear Density, Electric— The amount 
of electrification per unit of length. 

Linear Density of Charge. — The density 
of charge per-unit-of -length. 

Linear Insulation. — The product of the 
total insulation of a line by its length. 

Linear Insulation of Cable. — The prod- 
uct of the insulation resistance of a cable 
by its length. 

Linear Spectrum. — A spectrum consist- 
ing of a few isolated frequencies. 

Line-Man. — One who puts up and repairs 
line circuits, and attends to the receptive 
devices connected therewith. 

Link-Fuse. — A link-shaped leaden plate, 
provided with suitable ends for connection 
with the copper fuse-wire terminals. 

Link-Fuse Cut-Out. — A cut-out employ- 
ing a link-fuse. 

Linkages. — In a coil traversed by a cur- 
rent, the sum of the magnetic flux due to 
that current linked with the coil, obtained 
by considering the quantity of flux linked 
with each turn, separately and succes- 
sively, and adding the fluxes so obtained. 

Linked Magnetic and Electric Cir- 
cuits. — A phrase sometimes employed to 
represent the interlinked condition of 
magnetic and electric circuits. " 

Liquid Compass. — A form of ship's com- 
pass in which the compass-needle is sus- 
pended, not only by the usual gimbals, but 
is also so arranged that its oscillations are 
checked by a surrounding liquid. 

Liquid Flow. — The quantity of liquid 
that escapes from an orifice, or passes 
through any cross-section of a pipe or 
channel, in a given time. 

Liquid-Level Alarm, Electric— A de- 
vice for electrically sending an alarm 
when a liquid level differs materially 
from a given level. 

Liquid Resistance Load.— An artificial 
load for a dynamo consisting of a mass 
of liquid interposed between suitable 
electrodes. 



Liquid Thermostat.— A thermostat 
whose operation depends on the expan- 
sion of a liquid. 

Liquefaction. — The conversion of a solid 
into a liquid by the addition of heat, or 
of a gas into a liquid, either by the removal 
of heat, or by the combined influence of 
low temperature and pressure. 

Listening Cam. — In a telephone system a 
metallic cam or lever-key by means of 
which an operator readily places her tele- 
phone in circuit with a subscriber. 

Listening Key. — In a telephone switch- 
board, a listening cam. 

Lithanode. — Highly conducting lead per- 
oxide in a solid form suitably prepared for 
the plate of a storage cell. 

Line Trolley-Crossing.— (1) The point or 
plate where two trolley wires cross each 
other at a street crossing. (2) A line 
crossing. 

Live Wire. — (1) A wire through which 
current is passing. (2) A wire connected 
with an electric pressure or source. 

Liverpool Repeater. — A name given to 
a form of telephone repeating induction 
coil in which the iron core is constructed 
of thin wires bent around over the coils, 
so as to overlap at the ends, and form a 
complete magnetic circuit. 

Load. — The work thrown on any machine. 

Load-Diagram of Station.— A curve 
which represents the output of a station 
for a given time, say for the twenty-four 
hours of the day. 

Load-Factor. — The ratio of the average 
to the maximum load. 

Load of Dynamo. — The current delivered 
by a dynamo. 

Load-Panel. — The panel of a centm',- 
station switchboard provided with appa- 
ratus for indicating the total station-load. 

Loadstone. — An objectionable orthogra- 
phy sometimes employed for lodestone. 

Local Action of Dynamo-Electric Ma- 
chine. — The loss of energy in a dynamo 
by the establishment of eddy currents in 
its pole-pieces, cores, or other conducting 
masses. 

Local Action of Voltaic Cell.— An irreg- 
ular consumption of the zinc, or positive 
element of a voltaic cell, bj- the fluid or 
electrolyte when the circuit is opened or 
broken, as well as when it is closed or in 
regular action. 

Local Battery. — A voltaic battery thrown 
into or out of action by a relay and em- 
ployed at a station on a telegraphic line, 



Loc] 



832 



[Lon, 



to operate a sounder, or a registering or 
recording apparatus, at that point only. 
Local Battery Circuit. — The circuit in a 
telegraphic system in which is placed the 
local battery, as distinguished from the 
main battery. 

Local Calls. — At a central telephone ex- 
change, a call received from a subscriber 
connected directly therewith, as distin- 
guished from a call received from another 
exchange. 

Local Currents. — A term sometimes used 
for eddy currents. 

Local Faradization.— A method of thera- 
peutically applying the voltaic current, 
similar in general to that employed in 
local galvanization. 

Local Galvanization.— The application 
of galvanization to portions of the body 
only, in contradistinction to general gal- 
vanization. 

Local Jack. — In a multiple telephone 
switchboard, an answering jack corre- 
sponding to a local line drop, or a jack 
separated from the main body of the 
switchboard and set in a local row for the 
convenience of the operator in answering 
calls. 

Localization of Faults. — Determining 
the position of a fault on a telegraphic line 
or cable by electrical tests applied at one 
or both ends. 

Localization Test.— A test of a faulty cir- 
cuit made to determine the position of 
the fault. 

Localized Capacity.— Capacity inserted 
in a circuit in one or more condensers, as 
distinguished from distributed capacity, 
ur that which is present throughout the 
entire circuit. 

Localized Inductance. — Inductance in- 
serted in a circuit at one or more points, 
as distinguished from distributed induct- 
ance which is present throughout the 
entire circuit. 

Localized Vector.— (1) A vector function 
of space. (2) A vector point-function. 
(3) A vector quantity which is a property 
of every point of a region. 

Locally Inter-Connected Switchboard. 
A switchboard sub-divided into sections, 
each provided with auxiliary jacks which 
are interconnected among the different 
sections. 

Lock, Electric. — A lock that is automati- 
cally released by the aid of a distant push- 
button. 

Locomotive, Electric— (1) A locomotor 
whose motive power is electricity. (2) An 
electrically-driven locomotive engine. 



Locomotive Head-Light, Electric— An 

electric light placed in the focus of a par- 
abolic reflector in front of a locomotive 
engine. 
Locomotor. — A travelling motor, as dis-[ 
tinguished from a stationary motor. | 

Locomotor, Electric. — An electrically 
driven locomotor. 

Lodestone. — A name given to a piece of 
naturally magnetized iron ore. 

Lodge's Standard Voltaic Cell. — A 

standard form of Daniell's cell. 

Log, Electric. — An electric device for 
measuring the speed of, or the distance 
traversed by, a vessel. 

Logarithm. — The exponent, or the power 
to which it is necessary to raise a fixed 
number called the base, in order to pro- 
duce a given number. 

Logarithmic — Of or pertaining to a loga- 
rithm. 

Logarithmic Curve. — A curve in which 
the rate of increase or decrease of the or- 
dinate is proportional to the ordinate it- 
self. 

Logarithmic Decrement of Galvano- 
meter. — (1) In a series of galvanometer 
swings or deflections, the ratio of any 
pair of successive amplitudes. (2) The 
ratio of any two successive total swings 
or deflections of a galvanometer needle. 

Logging Motor, Electric — (1) An elec- 
tric locomotor employed for hauling logs. 
(2) A form of telpher motor moving over 
a cable way, usually over a swamp, for 
hauling logs out of the same. 

Long- Arc System of Electric Lighting. 
A system of arc lighting employing long 
arcs and, consequently, high electro-mo- 
tive forces. 

Long-Closed Circuit. — A series circuit in 
which all the devices are included as dis- 
tinguished from a series circuit in which 
some of the electro-receptive devices are 
cut-out. 

Long-Coil Magnet. — (1) An electro-mag- 
net whose magnetizing coil consists of 
many turns of fine wire. (2) A high- 
resistance magnet. 

Long-Connection Armature-Winding. 
Such a connection of a two-circuit arma- 
ture winding that in each circuit electro- 
motive forces are produced by field poles 
of one polarity only. 

Long Connection of Two-Circuit 
Gramme- Windings. — A form of 
Gramme winding in which the two cir- 
cuits from brush to brush consist of con- 
ductors that are influenced by only one- 
half the poles. 



Lon.] 



833 



[Loo, 



Long-Core Electro-Magnet.— An electro- 
magnet with a long core. 

Long-Distance Carbon Telephone 
Transmitter. — A form of microphonic 
telephone transmitter suitable for use on 
long-distance circuits. 

Long-Distance Telephone Cabinet.— 
An approximately sound-tight cabinet 
employed for convenience and secrecy in 
telephonic communication. 

Long-Distance Transmission. —Trans- 
mission of electric energy over fairly con- 
siderable distances. 

Long End of Quadruplex Battery. — 
The end of a quadruplex battery that is 
further from the point of intermediate 
connection than the short end. 

Long-Range Electrometer. — An electro- 
meter the range of whose scale is compar- 
atively long. 

Long-Shunt Compound- Winding.— A 
compound winding of a dynamo-electric 
machine in which the shunt coil is con- 
nected directly, or through resistance, 
with the terminals of the machine, as dis- 
tinguished from a short-shunt compound- 
winding. 

Long-Shunt Compound-Wound Dy- 
namo-Electric Machine. — A com- 
pound-wound dynamo, in which the 
shunt-field magnet coils form a shunt to 
the binding posts of the machine. 

Longitudinal Magnetization.— Such a 
magnetization of a bar or rod, that its 
separate magnetic particles are arranged 
with their axes lying in the direction of 
the length of the bar. 

Longitudinal Vibrations. — Vibrations 
set up in an elastic medium in the direc- 
tion of propagation or transmission, as dis- 
tinguished from transverse vibrations 
which occur at right angles to the direc- 
tion of propagation. 

Loom, Electric. — An electrically operated 
loom , in which the Jacquard cards of the 
ordinary loom are replaced by simple per- 
forated metal plates, whose perf orations 
correspond to those in the Jacquard cards. 

Loop Bracket. — (1) A insulating bracket 
from which a conducting loop can con- 
veniently be run so as to include a source 
or translating device. (2) A bracket for 
holding two insulators and wires, such as 
might form a loop. 

Loop-Break. — A device for introducing a 
loop in a break made at any part of a cir- 
cuit. 

Loop-Circuit. — (1) A term sometimes ap- 
plied to a circuit in parallel or multiple- 
arc. (2) A metallic circuit. (3) A circuit 

53 



having two wires, one out-going and the 
other returning, as distinguished from an 
earth-return circuit. 

Loop Cut-Out. — A cut-out placed in a 
loop. 

Loop, Electric— A portion of a main cir- 
cuit consisting of a wire going out from 
one side of a break in the main circuit and 
returning to the other side of the break. 

Loop-Mile.— (1) A mile of going and 
return, conductor in a loop circuit. (2) A 
mile of double conductor. (3) A double 
mile of conductor. (4) A distance of one 
mile traversed by a pair of conductors. 

Loop or Spreader Bracket.— A bracket 
used on cross-arms for taking off loops 
that are to be carried to service wires, 
branch mains, or transformers. 

Loop Switch. — A switch for opening or 
closing a loop, or for throwing a loop into 
or out of a main circuit. (2) A switch 
for connecting a branch office with a du- 
plex or quadruplex switch at a main of- 
fice, so that the branch office assumes 
control of one set of apparatus ; i. e., 
sends and receives messages on the duplex 
or quadruplex system. 

Loop System of Distribution.— A system 
of distribution employed in the early his- 
tory of electric lighting, in which each of 
a number of lamps was furnished with cur- 
rent through a single machine by means 
of a separate and independent loop or cir- 
cuit connected with the terminals of such 
machine. 

Loop-System of Parallel Distribution. 
A system of parallel distribution in 
which a pair of mains is connected to a 
generator in a manner designed tv eqv al- 
ize the drop of pressure ; one main being 
connected at the home end directly to 
the generator, and the other being con- 
nected at its distant end to the gei 
through a separate wire. 

Loop Test. — A localization test for a fault 
in a loop of two telegraphic wires, or in a 
complete metallic circuit. 

Loop Winding. — A term sometimes used 
for lap- winding. 

Loop- Winding of Alternator.— (1) Coil 
winding. (2) An alternator armature- 
winding in which the wire is laid on the 
surface of the armature core in loops or 
coils. 

Loops of Force. — A term sometimes ap- 
plied for lines of force. 

Loops of Induction. — A term sometimes 
applied for lines of magnetic induction. 

Loops of Mutua*L-In duct ion. — Loops or 
lines of induction produced in any cir- 



Loo.] 



834 



[Lum. 



cuit by variations in the intensity of the 
current flowing in a neighboring circuit. 
Looping-In. — A term sometimes employed 
for a method adopted in grounded tele- 
phone or telegraph circuits for connect- 
ing several instruments in series in a loop 
in that circuit, so that any conversation 
must be transmitted through all the in- 
struments which happen to be in the cir- 
cuit between the parties connected. 

Loss Plate of Voltameter.— (1) That plate 
of a voltameter from which the metal 
is electrolytically dissolved during the 
passage of the current. (2) The plate con- 
nected with the anode or positive ter- 
minal. 

Loose Carbon Transmitter.— (1) A tele- 
phone transmitter employing loose car- 
bon or carbon dust. (2) A dust telephone 
transmitter. 

Loose Contact. — A contact effected by 
two or more surfaces that rest loosely on 
one another, or by means of their weight 
only. 

Loose-Handle Switch.— A form of switch 
in which the handle after it has been 
moved a short distance falls into a new 
position of equilibrium. 

Loss of Continuity. — A disconnection or 
interruption of a circuit. 

Loud-Speaking Telephone.— (1) A name 
given to any telephone characterized by 
the intensity of the sounds produced by 
its receiver. ' (2) A name sometimes given 
to the electro-motographic telephone. 

Loudness. — That quality of a sound which 
depends on the amplitude of its vibra- 
tions. 

Lo^v -Frequency.— (1) A frequency of but 
comparatively few alternations per sec- 
ond. (2) Any frequency lower than that 
usually employed. 

Low-Frequency Trans forme r.— A 
transformer designed for operation on a 
low-frequency circuit. 

Low-Potential Current. — A term some- 
times used for a current on a low-pressure 
circuit. 

Low-Potential System. — In the National 
Electric Code, a system having a pressure 
less than 300 volts. 

Low Pressure. — A comparatively small 
pressure or electromotive force. 

Low-Pressure Circuit. — A circuit de- 
signed for use in connection with low 
electric pressure. 

Low-Pressure Incandescent Lamp. — 
An incandescent lamp 1 whose filament is 
short and thick, and, consequently, of 



low electric resistance suited for a low 
pressure. 

Low-Resistance Magnet. — A magnet 
wound with low-resistance magnetizing 
coils. 

Low-Speed Electric Motor.— An elec- 
tric motor designed to run normally at 
low speeds. 

Low Tension. — A term sometimes used 
for low pressure. 

Low-Tension Bus. — In a central station 
any bus-bar connected with a low-tension 
generator. 

Low-Tension Electric Fuse.— A fuse 
that is ignited by heating a wire to in- 
candescence by the passage of an electric 
current of low pressure, as distinguished 
from a high-tension fuse. 

Low-Tension Switch. — A switch de- 
signed for use on low-tension circuits. 

Low Vacuum. — (1) A vacuum in which 
the mean-free-path of the molecules of 
the residual gas is small as compared with 
the dimensions of the containing vessel. 
(2) A space from which only a portion of 
the air or residual gas has been removed. 

Loxodograph. — An apparatus for elec- 
trically recording on paper the actual 
course of a ship, by the combined action 
of magnetism and photography. 

Lubricating.— Reducing friction by 
means of lubrication. 

Lubrication. — The reduction of friction 
between surfaces, by rendering them 
slippery. 

Luces. — A plural of lux. 

Lumen. — (1) A unit of flux-of-light equal 
to the light received by a square metre of 
spherical surface, from a point source of 
unit intensity, placed at the centre of a 
sphere one metre in radius. (2) The flux 
of light through a steradian from a point 
source, whose intensity is one pyr. (3) A 
pyr-steradian. 

Lumen-Meter. — An instrument for meas- 
uring the flux of light. 

Lumen-Second. — A rad. 

Lumination. — A term proposed for il- 
lumination. (Not in use.) 

Luminescence. — A limited power for 
emitting light possessed by certain bodies 
which have previously acquired potential 
energy by exposure to light or radiant 
energy. 

Luminescence Lamp. — (1) A fluorescent 
lamp. (2) A lamp rendered luminescent 
by bombardment. (3) An X-ray lamp. 
(4) A vacuum-tube lamp. 



Lum.] 



835 



[Mac, 



Luminiferous. — Bearing or carrying 

light. 
Luminosity. — A term sometimes used for 

the brightness of a source. 
Luminous Absorption.— The absorption 

of luminous energy in its passage through 

bodies. 
Luminous Efficiency.— The ratio which 

the luminous radiation emitted by a source 

bears to the total radiant energy emitted 

by such source in a given time. 

Luminous Flux. — A phrase sometimes 
employed for flow of light. 

Luminous Frequencies.— Physiological- 
ly effective frequencies, or those capable 
of producing the sensation of light. 

Luminous Heat. — Heat radiation accom- 
panied by or containing physiologically 
effective frequencies. 

Luminous Intensity. — The amount of 
visible radiation emitted from a luminous 
source per-unit-of-area of surface. 

Luminous Interference. — Interference 
produced by light waves of the same 
frequency when out of phase with each 
other. 

Luminous Radiation. — Radiation capa- 
ble of affecting the eye. 

Lummer-Brodhun Screen.— A form of 
photometric screen requiring the use of 



but one eye, thus eliminating any errors 
due to the varying sensibility of the two 
eyes, each of the two sources of light 
that are being compared illumining its 
own field only, and these two fields 
being presented to the eye as a disc and 
circle respectively, the latter surround- 
ing the former, and yet having a sharp 
line of separation from it. 

Lunar-Inequality of Earth's Magnetic 
Variation. — Small changes in the value 
of the magnetic variation or inclination, 
dependent on the position of the moon 
as regards the magnetic meridian. 

Lunar-Inequality of Earth's Magnet- 
ism. — Small variations in the value of 
the earth's magnetic elements dependent 
on the position of the moon as regards 
the magnetic meridian. 

Lux.— (1) A unit of illumination equal to 
the light received on each square metre of 
the interior of a sphere whose radius is 
one metre, from a bougie-decimale placed 
at its centre. (2) An illumination equal 
to a lumen-per-square-metre. (3) The 
normal illumination produced by one 
carcel at a distance of a metre. 

Lux-Second. — (1) The time-illumination 
of one lux during one second. (2) A unit 
of time-illumination employed in photo- 
graphy. (3) A phot. 



M 



M. — A contraction sometimes employed to 

express a pressure of the millionth of an 

atmosphere. 
m. — A symbol for magnetic moment. 
m. — A symbol for strength of magnetic 

pole. 
m. — An abbreviation for metre, a practical 

unit of length. 
m. — An abbreviation for minute, a practical 

unit of time. 
(i. — A symbol for magnetic permeability or 

inductivity. (International notation.) 
fi. — A symbol for micron, the millionth of a 

metre, or one thousandth of a millimetre. 

jifj.. — A symbol for bicron, the millionth of 
a millimetre, or thousandth of a micron. 

m 2 . — An abbreviation for square metre, a 
practical unit of surface. 

m 3 . — An abbreviation for cubic metre, a 
practical unit of volume. 

m.a. — A contraction for milli-ampere. 



m : s. — An abbreviation proposed for metre- 
per-second, a practical unit of velocity. 

m : s 2 . — An abbreviation proposed for 
metre-per-second-per-second, a unit of 
acceleration. 

mm. — A contraction for millimetre. 

t 

M. Current. — A term proposed for mean 
current. 

M. M. F. — A contraction for magneto- 
motive force. 

M. P. — A contraction for man-power. 

M. P. H. — A contraction sometimes em- 
ployed in railroad work for miles-per- 
hour. 

M. S. Current. — A term proposed for 
mean-square-current. 

Mac or Mack.— A term at one time pro- 
posed for the practical unit of self-induct- 
ance, after Maxwell. 

Machine* Seal of Lamp Chamber.— A 
hermetical seal effected mechanically be- 



Mac] 



836 



[Mag. 



tween the glass support of an incandes- 
cent lamp and the walls of the lamp 
chamber. 
Machine Telegraphic Transmission.— 
High-speed telegraphic transmission ef- 
fected by means of an automatic tele- 
graphic transmitter. 

Machine Telegraphy.— Automatic or 
high-speed telegraphy. 

Machine Tool, Electric— An electrically 
driven machine tool. 

Made Circuit. — A completed circuit. 

Magazine Fuse. — A safety fuse contain- 
ing a number of spare fuses, so arranged 
as to readily permit the replacement of 
the fuse when blown, either automatic- 
ally, or by hand. 

Magic Pane. — A condenser formed of a 
sheet of glass, covered on one side with 
pieces of tin-foil, with small spaces left 
between them disposed in some design on 
the glass, which design becomes lumin- 
ous on the discharge of the condenser. 

Magne-Crystallic Action.— A term pro- 
posed by Faraday to express differences 
in the action of magnetism on crystalline 
bodies in different directions. 

Magne-Crystallic Force.— The force 
which produces magne-crystallic actions. 

Magne-Electric Induction.— A variety 
of electro-dynamic induction in which 
electric currents are produced by the 
motion of permanent magnets past con- 
ductors, or of conductors past permanent 
magnets. 

Magnes Stone. — An old name for mag- 
netite or for a natural magnet. 

Magnet. — (1) Any body producing mag- 
netic flux. (2) A body possessing the 
power of attracting the unlike pole of an- 
other magnet, or of repelling the like 
pole, or of inducing magnetism in mag- 
netizable bodies. 

Magnet Coil. — A coil of insulated wire 
surrounding the core of an electro-mag- 
net, through which the magnetizing cur- 
rent is passed. 

Magnet Cores. — Bars or cylinders of iron 
on which the magnetizing coils of wire 
are placed. 

Magnet Operation.— The use of a magnet 
for the purpose of removing particles of 
iron from the eye. 

Magnetic or Magnetical.— Of or pertain- 
ing to a magnet. 

Magnetic A-B-C-Instrument.— A step- 
by-step dial telegraph instrument employ- 
ing magneto-induced currents. ' 

Magnetic Adherence.— Adhesion be- 



tween surfaces, due to their mutual mag- 
netic attractions. 

Magnetic Aelotropy.— A difference in 
the magnetic susceptibility of a mass of 
iron in different directions. 

Magnetic Air-Circuit.— That portion of 
a magnetic circuit which passes wholly 
through air. 

Magnetic Air-G-ap. — Any gap in an aero- 
ferric magnetic circuit filled with air. 

Magnetic Alternator. — A magneto-alter- 
nator. 

Magnetic Atmosphere.— (1) A term for- 
merly employed for a space filled with 
the assumed magnetic effluvia. (2) A 
magnetic field. 

Magnetic Attraction.— The mutual at- 
traction exerted between unlike magnetic 
poles. 

Magnetic Axis.— (1) The line along which 
a magnetic needle, free to move, but 
which has come to rest in a magnetic 
field, can be turned without changing the 
direction in which it comes to rest. (2) 
The line connecting the poles of a bar 
magnet or needle. 

Magnetic Axis of Straight Needle.— 

A straight line drawn through a mag- 
netic needle joining its poles. 

Magnetic Azimuth.— (1) The arc inter- 
cepted on the horizon, between a mag- 
netic meridian and a great circle passing 
through the observed body. (2) A mag- 
netic bearing. 

Magnetic Battery.— The combination of 
a number of separate magnets so as to be 
capable of acting as a single magnet. 

Magnetic Bearing.— The horizontal angle 
included between a horizontal line from 
an observer's eye to an object and the 
observer's magnetic meridian. 

Magnetic Bearing Compass. — A com- 
pass provided with means for taking bear- 
ings. 

Magnetic Belting.— A method of driving 
machinery in which the belt is provided 
at frequent intervals with strips of sheet 
iron riveted to it perpendicularly to its 
length and the iron driving pulley mag- 
netized, so that the magnetic attraction 
increases the friction or grip on the pulley. 

Magnetic Blow-Out.— (1) A device for 
extinguishing an arc by an electro-mag- 
net. (2) A device employed for extin- 
guishing an arc formed between the con- 
tact pieces of a street-car controller, or 
other similar device, by means of the flux 
produced by an electro-magnet which is 
placed in the circuit of the current pro- 
ducing the arc. 



Mag.] 



837 



[Mag. 



Magnetic Blow-Out Lightning-Ar- 
rester. — A lightning arrester in which 
the arc, when formed, is blown out by 
the action of the flux of an electro-mag- 
net placed in the circuit of the arc. 

Magnetic Bridge..— An apparatus for 
measuring magnetic resistance, similar 
in principle to Wheatstone's electric 
bridge. 

Magnetic Centre of Gravity.— A con- 
ception respecting the existence of a 
point from which the magnetic flux pro- 
ducing a magnet pole issues, similar to 
the conception of a centre of gravity in 
an unequally loaded plane. 

Magnetic Circuit. — The path through 
which magnetic flux passes. 

Magnetic Circuit-Breaker.— A circuit 
breaker operated by means of an electro- 
magnet. 

Magnetic Circuit-Closer. — A circuit 
closer operated by means of an electro- 
magnet. 

Magnetic Closed-Circuit.— A ferro-mag- 
netic circuit. 

Magnetic Clutch.— (1) A form of clutch 
in which magnetic attraction is substi- 
tuted for ordinary mechanical force, to 
obtain the friction required in the clutch. 
(2) A clutch operated, electro-magnetic- 
ally. 

Magnetic Coereivity.— A term some- 
times used for coercive force. 

Magnetic Compensator. — A device for 
neutralizing the effects produced by the 
local magnetism of a ship on a magnetic 
needle. 

Magnetic Concentration.— The separa- 
tion of the useful ore from the dross in 
low-grade ores, by the use of an electro- 
magnetic separator. 

Magnetic Conduction - Current.— (1) 
Time-rate of increase of magnetic flux 
through a boundary. (2) Time-rate of 
flow of magnetism. 

Magnetic Conductivity. — Magnetic per- 

. meability. 

Magnetic Connection.— (1) A term some- 
times employed for inductive connection. 
(2) The connection of one circuit with 
another by means of inter-linked mag- 
netic flux. 

Magnetic Control of Galvanometer 
Needle. — The alteration in the sensibility 
of a galvanometer needle effected by 
means of a compensating magnet. 

Magnetic Couple. — The couple which 
turns or tends to turn a magnetic needle, 
placed in the earth's field, into the plane 
of the magnetic meridian. 



Magnetic Creeping. — A term used for 
a gradual increase in the magnetization , 
following a sudden increase in magnet- 
izing force. 

Magnetic Cross-Flux of Transformer. 
A magnetic flux across the direction of 
main or working flux and representing 
magnetic leakage. 

Magnetic Current. — The time-rate of in- 
crease of magnetic flux through a sur- 
face. 

Magnetic Curve-Tracer. — An instru- 
ment for graphically recording the varia- 
tions of magnetic intensity in a mass of 
iron subjected to cyclic variations of mag- 
netizing force. 

Magnetic Curves. — (1) Curved lines ex- 
tending in the direction of the flux-paths 
of a magnetic field, obtained by gently 
tapping a sheet of paper or glass sprinkled 
with iron filings and held in the field. (2) 
Magnetic figures. 

Magnetic Cycle. — A cycle of magnetiza- 
tion. 

Magnetic Day of Disturbance.— A day 
of magnetic disturbance. 

Magnetic Declination. — The variation of 
a magnetic needle from the true geo- 
graphical north. 

Magnetic Deep-Sea Thermometer.— A 
deep-sea thermometer containing small 
steel maximum and minimum limit 
markers which are reset by a permanent 
magnet. 

Magnetic Density.— The strength of 
magnetism as measured by the amount of 
magnetic flux which passes through unit 
area of normal cross-section. (2) Inten- 
sity of magnetic induction. 

Magnetic Deviation. — (1) The local mag- 
netic variation due to the presence o 
iron in the vicinity, as distinguished from 
the true magnetic variation 
ity considered. (2) On board ship, that 
part of the total magnetic variation due 
to iron in or on board the ship. 

Magnetic Diffusion. — Magnetic leakage. 

Magnetic Dip. — (1) The deviation of a 
freely suspended magnetic needle from a 
true horizontal position. (2) The mag- 
netic inclination. 

Magnetic Discontinuity.— The more or 
less marked change in the permeability 
of a magnetic circuit produced by any 
joint in such circuit. 

Magnetic Displacement.— (1) An imag- 
inary stress in the ether when subjected 
to magnetization and corresponding to 
electric displacement in electrostatics. 
(2) Magnetic induction . 



Mag.] 



838 



[Mag. 



Magnetic Dissymmetry.— (1) A lack of 
uniformity of the magnetic flux in a 
magnetic circuit, or in portions of that 
circuit. (2) A lack of uniformity pro- 
duced in the flux through the armature 
core of a dynamo or motor during its op- 
eration. 

Magnetic Disturbance.— A term some- 
times employed for temporary variations 
in the intensity of the earth's magnetism. 

Magnetic Divining Rod. — A small dip- 
ping needle employed for the purpose of 
locating approximately the position of 
beds of iron ore. 

Magnetic Effluvia.— (1) A term employed 
in the early history of magnetism for 
assumed imponderable effluvia which 
were supposed to be given off by magnets. 
(2) Magnetic flux. 

Magnetic Elements of a Place.— The 
values of the magnetic intensity, the 
magnetic declination or variation, and 
the magnetic inclination or dip of any 
place. 

Magnetic Equalizer. — A device for 
equalizing the otherwise unequal force 
exerted between a magnet pole and its 
armature at varying distances. 

Magnetic Equator. — (1) The line con- 
necting places on the earth's surface where 
a magnetic needle remains horizontal, 
when suspended so as to be free to move in 
a vertical as well as in a horizontal plane, 
(2) An irregular line passing around the 
earth, approximately midway between 
its magnetic poles. 

Magnetic Excitation. — Magnetization. 

Magnetic Explorer.— (1) A small flat 
coil of insulated wire, used, in connection 
with the circuit of a galvanometer or 
telephone, to determine the position and 
extent of the magnetic leakage of a 
dynamo, or other similar apparatus. (2) A 
search coil so connected to a ballistic 
galvanometer that its movements through 
magnetic flux will be indicated by the 
galvanometer. 

Magnetic Fatigue.— An increase in the 
hysteretic coefficient of iron due to an 
assumed fatigue after many cyclic re- 
versals. 

Magnetic Fatigue of Transformer. — 
(1) An increase in the hysteretic loss of a 
transformer with time. (2) The ageing 
of a transformer core. 

Magnetic Field.— (1) The region of mag- 
netic influence surrounding the poles of 
a magnet. (2) The space or region trav- 
ersed by magnetic flux. (3) A space 
traversed by magnetic flux in which a 



magnet needle, free to move, will assume 
a definite position. 

Magnetic Figures.— A name sometimes 
applied to the groupings of iron filings 
obtained when a sheet of paper or glass, 
sprinkled with filings, is so held in a mag- 
netic field as to permit the filings to be 
grouped or arranged under the influence 
of the magnetic flux. 

Magnetic Filament. — A polarized line or 
chain of ultimate magnetic particles. 

Magnetic Flow. — A term sometimes em- 
ployed for magnetic flux. 

Magnetic Fluids. — A term formerly em- 
ployed for the assumed fluids which were 
believed to be the cause of magnetic 
phenomena. 

Magnetic Austral Fluid.— The assumed 
magnetic fluid existing at the south pole 
of any magnet. 

Magnetic Boreal Fluid. — The assumed 
magnetic fluid existing at the north pole 
of any magnet. 

Magnetic Flux.— (1) The streamings that 
issue from and return to the poles of a 
magnet. (2) The total number of lines 
of magnetic force in any magnetic field. 
(3) The magnetic flow that passes through 
any magnetic circuit. 

Magnetic Flux-Density.— The quantity 
of magnetic flux in any part of a mag- 
netic circuit per-unit-of-area of normal 
cross-section. 

Magnetic Flux-Intensity.— The density 
of magnetic flux. 

Magnetic Flux-Paths. — Paths taken by 
magnetic flux in any magnetic circuit. 

Magnetic Force. — The force which causes 
the attractions and repulsions of mag- 
netic poles. 

Magnetic Friction. — A term sometimes 
used for magnetic hysteresis. 

Magnetic Fringe at Edge of Dynamo 
Pole-Pieces.— The lateral dispersion or 

• diffusion of magnetic flux through the 
air space which produces an apparent 
fringe of magnetic flux in the air sur- 
rounding the poles. 

Magnetic Gearing. — A form of friction > 
gearing employing magnetic adhesion. 

Magnetic Generator.— A magneto-elec- 
tric generator. 

Magnetic Helix.— A magnetizing coil. 

Magnetic Hysteresis.— (1) Apparent mo- 
lecular friction due to magnetic change 
of stress. (2) A lagging of magnetization 
behind the magnetic force producing it. 
(3) That quality of a magnetic substance 



Mag.] 



839 



[Mag. 



in virtue of which energy is absorbed on 
the reversal of its magnetization. 

Magnetic Image. — The analogue in mag- 
netism of an electric image in electro- 
statics. 

Magnetic Impermeability. — A term 
sometimes used for magnetic reluctivity. 

Magnetic Inclination. — (1) The angular 
deviation from a horizontal position of 
a freely suspended magnetic needle. 

(2) Magnetic dip. 

Magnetic Induction. — (1) In air, the 
density of magnetic force ; in iron or 
other magnetic material the sum of the 
prime flux, or magnetic force, and the 
magnetic flux thereby produced in the 
iron. (2) Total magnetic flux-density. 

(3) The production of magnetism in a 
magnetizable substance on its being 
brought into magnetic flux. 

Magnetic Inertia. — The inability of a 
magnetic core to instantly lose or acquire 
magnetism. 

Magnetic Intensity.— (1) Magnetic flux- 
density. (2) The quantity of magnetic 
flux per-unit-of-area of normal cross-sec- 
tion. (3) Magnetic induction. 

Magnetic Joint. — A joint effected be- 
tween contiguous pieces of iron forming 
portions of a magnetic circuit. 

Magnetic Lag. — (1) Magnetic viscosity 
manifested by the sluggishness with 
which a magnetizing force produces its 
magnetizing effects in a mass of iron. 
(2) The tendency of an iron core to resist, 
and, therefore, to retard its magnetiza- 
tion. (3) Hysteresis in iron. 

Magnetic Lag Motor. — A form of motor 
whose torque depends on magnetic lag or 
hysteresis. 

Magnetic Latitude. — (1) The meridional 
angular distance of a place north or south 
of the magnetic equator. (2) The lati- 
tude as deduced from the magnetic dip. 

Magnetic Leakage. — (1) A useless disper- 
sion of magnetic flux of a dynamo or 
motor by its failure to pass through the 
armature. (2) Any useless dispersion of 
magnetic flux by its failure to pass 
through a magneto-receptive device 
placed in the magnetic circuit. 

Magnetic Leakage Factor. — The ratio 
of the total flux generated in a magnetic 
circuit to the quantity usefully passing 
through an armature or magneto-recep- 
tive device. 

Magnetic Lightning- Arrester.— (1) An 
electro-magnetic blow-out lightning-ar- 
rester. (2) Any lightning-arrester em- 
ploying an electro-magnet. 



Magnetic Limbs. — (1) Magnetic cores. 
(2) Magnetic arms. 

Magnetic Limit. —A term sometimes em- 
ployed for the temperature at which a 
magnetic substance loses its magnetism 
on exposure to heat. 

Magnetic Line-Protector. — An electro- 
magnetic device placed on a telegraphic 
or other line for the purpose of protect- 
ing its instruments from lightning dis- 
charges. 

Magnetic Lines of Force.— (1) Lines of 
magnetic force. (2) Flux paths. (3) The 
lines along which a free magnetic pole 
would be urged. 

Magnetic Magazine. — A term sometimes 
employed for a compound magnet. (Ob- 
solete.) 

Magnetic Mass.— The quantity of mag- 
netism or imaginary magnetic matter 
resident on a polar surface. 

Magnetic Memory.— (1) That deviation 
of a magnetic condition of a magnetic 
substance from the complete response to 
an impressed magnetic force which is a 
function of antecedent magnetic states. 
(2) A term proposed for magnetic reten- 
tivity. (3) The ' power possessed by a 
magnetic substance, in virtue of hyster- 
esis, to retain in any magnetic state, the 
history of antecedent states. 

Magnetic Meridian. — (1) The great circle 
which passes through a place and through 
the poles of a magnetic needle at that 
place, when in a position of rest under the 
free influence of the earth's magnetism. 
(2) The terrestrial great circle coinciding 
in plane with the direction of the earth's 
local magnetic force. 

Magnetic Moment. — (1) The product of 
the strength of one of the poles of a i 
net into the distance between ^hem. 
(2) The sum of the two fore 
directive couple of a magnet multiplied by 
half the perpendicular distance between 
the directions of these forces. (3) The 
length of a magnet multiplied by the in- 
tensity of one of its poles. 

Magnetic Needle. — (1) A magnetized 
steel needle, or thin straight strip or rod. 
(2) A straight bar of magnetized steel, 
supported at or above its centre of grav- 
ity, and free to move in a horizontal 
plane only, in a vertical plane only, or in 
both. 

Magnetic North. — That point of the hori- 
zon which is indicated by the north-seek- 
ing pole of a magnet. 

Magnetic Observatory. — An observatory 
in which observations are made of the 



Mag.] 



840 



[Mag. 



variations in the direction and intensity 
of the earth's magnetic field. 

Magnetic Oscillation. — A magnetic vi- 
bration, or to-and-fro variation. 

Magnetic Output.— The product of the 
magnetic flux produced by any source and 
its magneto-motive force. 

Magnetic Parallels. — Lines connecting 
places on the earth's surface at right 
angles to the isogonal lines, or lines of 
equal declination or variation. 

Magnetic Permeability.— (1) Conductiv- 
ity for magnetic flux. (2) The ratio be- 
tween the magnetic induction produced 
in a magnetic substance, and the magnet- 
izing force producing such magnetic in- 
duction. 

Magnetic Permeance.— Magnetic perme- 
ability. 
Magnetic Permeation. — The passage of 

magnetic flux through any permeable 

substance. 
Magnetic Perturbations. — Abnormal 

magnetic variations, or disturbances. 
Magnetic Phantom. —A term sometimes 

employed for magnetic figures. 
Magnetic Points of Convergence.— The 

magnetic paths of the earth around which 

the isogonic lines are drawn. 
Magnetic Polar-Area. — The active area 

of the pole-pieces of a magnet. 

Magnetic Polar-Intensity.— The intens- 
ity of the magnetic flux produced at the 
pole-pieces of a magnet. 

Magnetic Polarization. — That condition 
of a magnetizable substance when it is 
subjected to polarization. 

Magnetic Polar-Surface.— The magnetic 
polar area. 

Magnetic Polarity. — Polarity acquired 
by a magnetizable substance when 
brought into magnetic flux. 

Magnetic Poles. — Those parts of a mag- 
netic source from or at which the flux 
emerges or enters. 

Magnetic Potential.— (1) That property 
of any space by virtue of which magnetic 
work is done when a magnet pole is 
moved therein. (2) The amount of work 
required to bring up a unit north-seeking 
magnetic pole from an infinite distance 
to a given point in a magnetic field. 
(3) The line integral of magnetic force on 
a unit pole in coming from an infinite 
distance to the point considered. 

Magnetic Proof-Piece. — A magnetized 
ellipsoidal or square rod employed for as- 
certaining the distribution of magnetism 



over a magnet by the force required to 
detach the same. 

Magnetic Proof-Plane.— A small coil of 
wire placed in the circuit of a delicate 
galvanometer, and used for exploring a 
magnetic field. 

Magnetic Reactance. — In an alternating- 
current circuit the reactance of a coil as 
distinguished from the reactance of a 
condenser. 

Magnetic Reluctance.— The resistance 
offered by a medium to the passage 
through it of magnetic flux. 

Magnetic Eemanenee— The magnetic 
flux-density left in iron or other magnetic 
substance after the removal of a mag- 
netizing force. 

Magnetic Repulsion. — Mutual repulsion 
exerted between two similar magnet 
poles. 

Magnetic Resistance.— A term formerly 
used for magnetic reluctance. 

Magnetic Resistivity.— (1) Magnetic re- 
luctivity. (2) The reluctance of a medium 
referred to the reluctance offered between 
parallel faces of a unit cube. (3) The 
magnetic analogue of electric resistivity. 

Magnetic Retardation. — A retardation 
in the magnetization or demagnetization 
of a substance due to magnetic lag. 

Magnetic Retentiveness.— A name some- 
times applied to magnetic refentivity. 

Magnetic Retentivity.— (1) The resist- 
ance a body offers to change of mag- 
netization. (2) Hysteretic retention of 
magnetism when the magnetizing force 
is changed or wholly withdrawn. (3) 
That quality of iron or other magnetic 
substance in virtue of which it retains its 
magnetic flux after the withdrawal of the 
magnetizing force. (4) Magnetic rema- 
nence. 

Magnetic Ringer.— A magnetic call-bell. 

Magnetic Rotary - Polarization. — (1) 
Rotary polarization of a beam of plane 
polarized light, produced by its passage 
through magnetic flux. (2) Magneto- 
optic rotation. 

Magnetic Safety Factor.— The factor of 
safety of demagnetization. 

Magnetic Saturation. — (1) The maximum 
magnetization which can be imparted to 
a magnetic substance. (2) The condition 
of iron, or other magnetic substance, when 
its intensity of magnetization is so great 
that it fails to be further magnetized by 
any magnetizing force, however great. 

Magnetic Screen. — (1) A hollow box 
whose sides are made of thick iron placed 



Mag.] 



841 



[Mag. 



around a magnet or other body, so as 
to shield its interior from a magnetic 
field external to the box. (2) A magnetic 
shield. 

Magnetic Screening. — Preventing mag- 
netic induction from taking place by in- 
terposing either a thick iron plate, or a plate 
of good conducting material, between 
the body producing the magnetic field and 
the body to be magnetically screened. 

Magnetic Self-induction.— (1) Electro- 
magnetic self-induction. (2) The power 
possessed by a magnet of inducing an op- 
posite polarity in its own particles. (3) Self- 
demagnetizing power in a magnet. 

Magnetic Sense. — A name sometimes ap- 
plied to the assumed sense by means of 
which magnetic influences are claimed to 
be perceived. 

Magnetic Shade. — A term sometimes used 
for a magnetic screen. 

Magnetic Shells. — Sheets or layers con- 
sisting of magnetic particles in each of 
which all the north poles are situated in 
one of the flat surfaces of the layer, and 
all the south poles in the opposite surface. 

Magnetic Shield for Watches.— A hol- 
low case of iron in which a watch is per- 
manently kept in order to partially shield 
it from the influence of external magnetic 
flux. 

Magnetic Shunt. — An additional path of 
magnetic material provided in a magnetic 
circuit for the passage of magnetic flux. 

Magnetic Shunt-Circuit.— An additional 
or branch circuit through which some of 
the flux is diverted from the main mag- 
netic circuit. 

Magnetic Shunt-Transformer.— (1) A 
transformer provided with a magnetic 
shunt of regulable value, for the purpose 
of regulation. (2) A transformer situated 
in a magnetic shunt. 

Magnetic-Siren Telephone-Call. — A 
magnetophone employed as a telephone 
call. 

Magnetic Solenoid. — A spiral coil of wire. 
which acts like a magnet when an electric 
current is sent through it. 

Magnetic Sounds. — Faint clicks heard on 
the magnetization and demagnetization 
of a readily magnetizable substance. 

Magnetic Source.— Anything capable of 
producing magnetic flux. 

Magnetic Spectrum. — (1) A term some- 
times employed in place of magnetic 
figures or a magnetic field. (2) The suc- 
cession of bright and dark fluorescent 
bands produced upon a suitable screen in 



a Crookes tube when the cathode rays 
are deflected by magnetic flux. 

Magnetic Spin. — A term sometimes em- 
ployed for magnetic field. 

Magnetic Spiral. — A magnetizing spiral 
or helix. 

Magnetic Sticking of Armature.— The 
magnetic adhesion of the armature to the 
magnet poles under the influence of hys- 
teresis. 

Magnetic Storm. — (1) Any unusually 
marked irregularity occurring in the dis- 
tribution of the earth's magnetism result- 
ing in a variation in the value of its mag- 
netic elements. (2) A comparatively 
violent and widespread temporary pertur- 
bation of the earth's magnetic elements in 
some way associated with solar disturb- 
ances and electric earth currents. 

Magnetic Strain.— The result of subject- 
ing any medium to magnetic stress or 
magnetic flux. 

Magnetic Stream-Lines.— (1) Magnetic 
flux-paths. (2) Lines of magnetic flux. 
(3) The curved paths along which a free 
magnetic pole would be urged in different 
parts of the field. 

Magnetic Stress. — (1) The mechanical 
stress exerted by the attraction of magnet- 
ized bodies. (2) That property of flux 
which produces magnetic strain or mag- 
netic phenomena in bodies subjected to its 
influence. 

Magnetic Susceptibility.— (1) The ratio 
existing between the induced magnetiza- 
tion and the magnetizing force producing 
such magnetization. (2) The intensity of 
magnetism divided by the magnetic force. 

Magnetic Telephone. — (1) A name some- 
times given to an electro-magnetic tele- 
phone. (2) A magneto telephone. 

Magnetic Telephone-Transmitter or 
Receiver. — A magneto-telephone-trans- 
mitter or receiver. 

Magnetic Theodolite. — An apparatus for 
measuring the declination or variation of 
the magnetic needle at any place. 

Magnetic Tick. — (1) A metallic click heard 
on the magnetization and demagnetiza- 
tion of a bar of iron or steel. (2) The Page 
effect. 

Magnetic Time-Constant. — In an electric 
circuit or conductor, the ratio of the 
inductance to the resistance, usually ex- 
pressed in henry s per ohm, or seconds. 

Magnetic Traction. — (1) Tractive or sup- 
porting power exerted by a magnet. 
(2) Hauling or carrying effected magneti- 
cally. 



Mag.] 



842 



[Mag. 



Magnetic Unit Pole.— An imaginary free 
magnetic pole situated at a point, of such 
strength that it would act with a force of 
a dyne on a similar unit pole distant from 
it one centimetre. 

Magnetic Units. — (1) Units based on the 
force exerted between magnet poles. 
(2) Units employed in dealing with mag- 
nets and magnetic phenomena. (3) The 
magnetic system of C. G. S. electro- 
magnetic units, as distinguished from the 
electrostatic system. 

Magnetic-Vane Ammeter. — An am- 
meter in which the strength of a magnetic 
field produced by the current that is to be 
measured is determined by the repulsion 
exerted between a fixed and a movable 
iron vane placed inside the field and 
magnetized thereby. 

Magnetic-Vane Voltmeter. — A volt- 
meter in which the potential difference is 
measured by the repulsion exerted be- 
tween a fixed and a movable vane of soft 
iron placed within the field of the mag- 
netizing coil. 

Magnetic Variations. — Variations in the 
value of the magnetic elements of a place. 

Magnetic Variation-Transit.— An ap- 
paratus for measuring the magnetic decli- 
nation or variation at any place. 

Magnetic Variometer. — An instrument 
for comparing the horizontal component 
of the earth's magnetism at different 
localities. 

Magnetic Viscosity. — A property of iron 
or other paramagnetic substance in virtue 
of which a certain time is required before 
a given magnetizing force can produce 
its full effects. 

Magnetic Voltmeter— (1) An instrument 
in which the magnetic field of a current 
proportional to the difference of potential 
to be measured deflects a movable needle 
against the action of the field of a magnet. 
(2) A voltmeter employing a permanent 
magnet. 

Magnetic Vortices. — Imaginary vortices 
in the ether postulated to account for 
magnetic phenomena. 

Magnetics. — A word sometimes used for 
that branch of science which treats of the 
laws and phenomena of magnetism. 

Magnetician. — A word proposed for one 
skilled in the science of magnetism. 

Magnetification. — The production of 
magnetism in any body. 

Magnetine. — A word formerly applied for 
the assumed principle of magnetism ; i.e., 
the imponderable, hypothetical fluid to 



the presence of which magnetic pheno- 
mena were believed to be due. 

Magnetisation. — An orthography some- 
times used for magnetization, and in 
similar words where the z is replaced by s. 

Magnetish. — Possessing the property of 
magnetism to a limited degree. (Very 
rarely used.) 

Magnetism.— (1) That property or condi- 
tion of matter which accompanies the 
production of magnetic flux. (2) Mag- 
netic.flux or streamings. (3) That branch 
of science which treats of the nature and 
properties of magnets and of magnetic 
flux. 

Magnetism of Rotation.— A conception 
at one time entertained that revolving 
bodies became magnetized, as a deduction 
from Arago's experiment. 

Magnetist. — A magnetician. (Seldom 
used.) 

Magnetite. — A name given to mineral 

magnetic oxide of iron. 
Magnetizability. — Possessing the ability 

of becoming magnetized. 

Magnetizable. — Capable of being mag- 
netized. 

Magnetization.— The act of imparting or 
acquiring magnetization. 

Magnetization by Double-Touch. — 

A magnetization effected by placing two 
magnets with their opposite poles to- 
gether on the middle of the bar to be 
magnetized, moving them to one end of 
the bar, then moving them over the sur- 
face of the bar to the other end, and 
continuing these to-and-fro movements a 
number of times, observing to stop in the 
middle of the bar, and when the mag- 
netizing magnets are moving in the oppo- 
site direction to that in which they began 
to move. 

Magnetization by Separate-Touch. — 
Magnetization obtained by placing two 
magnetizing bars with their opposite 
poles at the middle of the bar to be mag- 
netized, drawing them away from each 
other towards its ends, returning them 
through the air to the middle of the 
magnet, and repeating this a number of 
times. 

Magnetization by Touch.— The produc- 
tion of magnetic poles in a magnetizable 
substance by touching it with a magnet. 

Magnetization Curves. — Curves which 
graphically represent the relation of a 
magnetizing force to the intensity of 
magnetization or to the magnetic flux. 

Magnetization Cycle.— (1) A cycle of 
magnetization. (2) A succession of mag- 



Mag.] 



843 



[Mag. 



netic states which terminate in the 
original state. 
Magnetize. — To endow with the property 

of magnetism. 

Magnetized. — Endowed with the property 
of magnetism. 

Magnetizee. — A word proposed to desig- 
nate a person who believes he is placed 
under the power of animal magnetism. 

Magnetizer. — (1) One who, or that which, 
magnetises. (2) A word proposed to desig- 
nate a person who claims that he can 
place another under the power of his 
animal magnetism. 

Magnetizing. — Endowing a body with 
magnetic qualities. 

Magnetizing Ampere-Turns. — The am- 
pere-turns of a magnetizing coil. 

Magnetizing Currents.— Currents that 
are employed in producing magnetization. 

Magnetizing Flux.— Flux which is in- 
tended to magnetize a body, or to keep it 
magnetized, as distinguished from mag- 
netic flux which performs any other 
functions. 

Magnetizing Force. — (1) The vector 
space- rate of descent of magnetic poten- 
tial. (2) The prime flux-density impressed 
upon a body, and which may induce 
magnetism in the same. (3) The force at 
any point with which a unit magnetic 
pole would be acted on. (4) The impressed 
flux-density of a field as distinguished 
from the total flux-density. 

Magnetizing Helix. — A magnetizing 
spiral or solenoid. 

Magnetizing Spiral. — A magnetizing 
helix or solenoid. 

Magnetizing Turn. — A single turn in a 
magnetizing coil. 

Magneto. — (1) A magneto-generator. 
(2) A small magneto-electric dynamo 
machine. 

Magneto- Alternator. — An alternator 
whose field flux is produced by perma- 
nent magnets. 

Magneto-Blasting Machine. — A mag- 
neto-electric machine employed for gen- 
erating the currents used in electric 
blasting. 

Magneto Call-Bell.— A call-bell operated 
by a magneto-electric machine. 

Magneto-Chemical Cell. — A cell, the 
voltaic couple of which consists of two 
magnetized steel bars, whose north and 
south poles are respectively immersed in 
a solution of oxalic acid. 

Magnetod. — A name employed by Reich- 



enbach for the assumed force or principle 

of animal magnetism." 
Magneto-Dynamic Force. — The force 

exerted between magnets, or between 

magnets and electric currents. 
Magneto-Dynamics. — That branch of 

dynamics which treats of the influence of 

magnet poles on one another. 
Magneto - Electric Alternating Ma- 
chine. — A magneto-alternator. 
Magneto-Electric Bell.— An electric bell 

whose actuating current is obtained from 

a magneto-electric machine. 

Magneto-Electric Brake.— (1) A device 
for checking the swing of a galvanometer 
consisting of means for sending slight 
inverse currents through the coils of the 
galvanometer. (2) An electro-magnetio 
brake. 

Magneto-Electric Call-Bell. — A call- 
bell operated by a magneto-electric ma- 
chine. 

Magneto-Electric Dynamo.—A dynamo' 
electric machine whose field magnets are 
formed of permanent magnets. 

Magneto-Electric Faradic- Apparatus. 
A small magneto-electric machine em- 
ployed in electro-therapeutics for produc- 
ing faradic currents. 

Magneto-Electric Force.— A theoreti- 
cally-assumed mechanical force exerted 
between a magnetic current and an elec- 
tric field, corresponding to the electro- 
magnetic force known to be exerted be- 
tween an electric current and a magnetic 
field. 

Magneto-Electric Generator.— A mag- 
neto-generator. 

Magneto-Electric Induction. — A va- 
riety of electro-dynamic induction in 
which electric currents are produced by 
the motion of permanent magnets past 
conductors, or of conductors past perma- 
nent magnets. 

Magneto-Electric Key.— A telegraphic 
key so arranged that a coil of wire on an 
armature connected with a key lever, 
through the movements of the key to- 
wards and from the poles of a permanent 
magnet, produces currents that are sent 
into the line. 

Magneto-Electric Machine.— A mag- 
neto-generator. 

Magneto-Electrical Medical Appara- 
tus. — A small magneto-alternator em- 
ployed in medical electricity for the pro- 
duction of alternating or pulsating cur- 
rents. 

Magneto-Electric Multiplier.— An early 
form of induction coil employed by Page. 



Mag.] 



844 



[Mai. 



Magneto-Electricity. — (1) Electricity 
produced by the motion of magnets past 
conductors or of conductors past magnets. 
(2) Electricity produced by magneto- 
electric induction. 

Magneto-Generator.— A dynamo-electric 
machine whose field flux is obtained from 
permanent magnets. 

Magnetogram. — Any automatic record 
obtained by means of a magnetic instru- 
ment. 

Magnetograph. — A permanent record ob- 
tained by the action of a self-recording 
magnetometer. 

Magneto-Induction Key.— A magneto- 
electric telegraph transmitter so arranged 
that the movements of a key produce the 
electric currents that are sent into the 
line. 

Magneto-Inductor.— An inductor con- 
sisting of a permanent magnet as distin- 
guished from an inductor consisting of 
an electro-magnet. 

Magneto-Inductive Capacity. — A term 
sometimes employed for magnetic per- 
meability. 

Magneto Instrument. — (1) A name for- 
merly applied to a magneto machine. 
(2) In telegraphy, a name sometimes em- 
ployed for a machine operating or oper- 
ated by magnetically-induced currents. 

Magnetology . — (1) A name sometimes ap- 
plied to the science of magnetism. (Not 
in general use.) (2) That branch of 
science which treats of magnetism. (Very 
seldom used.) 

Magnetometer. — (1) An apparatus for the 
measurement of magnetic force. (2) Any 
apparatus for measuring the elements of 
the earth's magnetic force. 

VEagnetometrie. — Of or pertaining to a 

magnetometer. 
Magnetometry. — That branch of science 

which treats of the measurement of the 

strength of magnetic fields. 
Magneto-Motive.— Producing magnetic 

effects. 

Magneto-Motive Force.— (1) The force 
which produces magnetic flux. (2) The 
force that moves or tends to move mag- 
netic flux. 

Magneto-Motive Intensity. — A term 
sometimes used for the slope of magneto- 
motive force. 

Magneto-Motor. — (1) A term formerly ap- 
plied to a voltaic battery coupled in par- 
allel. (2) A motor whose field is pro- 
duced by permanent magnets. 

Magneto-Optic Rotation.— A rotation of 



the plane of polarization of a beam of 
plane polarized light on its passage 
through a transparent medium, when 
placed in a strong magnetic field in the 
direction of the beam. 

Magnetophone.— A species of magnetic 
siren with which sounds are produced in 
a telephone by the periodic currents pro- 
duced in its coils by the rotation of a per- 
forated metallic disc in a magnetic field. 

Magneto-Pointer.— A dial of a printing 
telegraph. 

Magneto-Polar. — Possessing magnetic 
polarity. 

Magneto-Receptive Device.— A device 
that is capable' of being energized when 
placed in magnetic flux. 

Magnetoscope. — Any apparatus for the 
detection of the presence of magnetism, 
but not for measuring it. 

Magneto-Signals.— Any signals operated 
by a magneto-electric machine. 

Magneto-Static Ammeter.— An ammeter 
whose magnet is acted on by a uniform 
field of force with two coils, while at- 
tracted by two systems of powerful per- 
manent magnets. 

Magneto-Static Current-Meter. — A 

magneto-static ammeter. 
Magneto-Static Screening.— Screening 

from the inductive effects of a stationary 

magnetic field. 

Magneto-Statics. — The science which 
treats of magnetic forces at rest. 

Magneto-Tapper.— (1) A term sometimes 
employed for a magneto-key. (2) Aeon- 
tact key which closes the circuit of a 
magneto. 

Magneto-Telephone Transmitter.— A 

telephone transmitter formed of a power- 
ful compound magnet provided with a 
coil of insulated wire supported in front 
of one of its poles, and an iron core form- 
ing the pole-piece of the magnet. 

Magneto-Therapy. — Alleged electro- 
therapeutic effects produced by the ap- 
plication of magnets to the human body. 

Magnet Wire. — Insulated wire suitable 
for winding magnets and usually cotton- 
covered. 

Magpie Cable. — A name given to a form 
of telephone cable in which the wires or 
conductors are arranged in double pairs. 

Main Battery. — The battery employed in 
telegraphic systems for sending the signals 
over the main line, as distinguished from 
a battery employed for any other work. 

Main-Battery Circuit.— (1) A term some- 
times used for line circuit. (2) The cir- 



Mai.] 



845 



[Man. 



cuit of the main battery in any conduct- 
ing system. 

Main-Circuit Fuse.— A safety fuse pro- 
vided for the protection of the main cir- 
cuit. 

Main-Circuit Switch. — A switch inserted 
in a main circuit. 

Main Cut-Out. — Any cut-out placed in 
the circuit of a main. 

Main Feeder.— (1) The feeder to which 
the standard pressure-indicator is con- 
nected, and whose pressure controls the 
pressure at the ends of all the other 
feeders. (2) A standard feeder. (3) A 
principal feeder supplying a group of sub- 
feeders. 

Main Fuse. — A main-circuit fuse. 

Main-Line-Cireuit Switch.. — A main 
switch. 

Main-Line Cut-Out. — A main cut-out. 

Main-Line Relay. — A relay suitable for 
use in connection with a main telegraphic 
line. 

Main-Line Sounder. — A sounder suitable 
for use in connection with a main tele- 
graphic line. 

Main Switch. — (1) A switch connected 
with the electric mains. (2) A principal 
switch controlling a group of subsidiary 
switches. (3) A main-line-circuit switch. 

Main Telegraphic-Circuit.— The princi- 
pal or line telegraphic circuit. 

Main Telegraphic-Current.— The cur- 
rent employed on a main telegraphic line 
or circuit. 

Main Terminals of Machine.— (1) The 
principal terminals of a machine. (2) The 
terminals connected with the external cir- 
ci of a machine. 

Main-to -Dynamo Bonding.— A phrase 
employed for a method of bonding the 
v. Ls ia an electric car system, in which 
the bonding is between a positive water 
main, or buried metallic system, and the 
n terminal of the dynamo. 

Ma in- to -Track Bonding.— A phrase em- 
p .■* for a method of bonding of the rails 
i; an electric car system in which the 
bonding is between a positive water main 
and a negative track. 

Main-Trunk Telephone-Line.— (1) A 
main telephone line connecting two cities 
and usually erected with considerable 
care, as to conducting power, insulation, 
i I freedom from electrical disturbance, 
to serve as a general link of com- 
munication either for communication be- 
tween" those cities, or for communication 
through those cities. (2) A term used in 



contradistinction to a local telephone line 
connecting two stations. 

Main Tubes. — The tubes in an under- 
ground system, provided for the mains. 

Main Voltmeter.— (1) A voltmeter in a 
central station connected with the mains. 
(2) A principal or standard voltmeter. 

Main Wire.— (1) Wire used in or intended 
for electric mains. (2) Wire constituting 
part of an electric main. (3) The prin- 
cipal electric conductor in a distribution 
or conducting system. 

Mains. — (1) In a parallel system of distri- 
bution the parallel conductors carrying 
the main current, and to which translat- 
ing devices are connected. (2) In a sys- 
tem of parallel distribution, the principal 
conductors which extend from the risers, 
or service wires, along the corridors or 
passages along the floor to be lighted. 

Mains of Electric Railroads. —The 
mains from which the driving current is 
supplied to the cars. 

Make. — To complete or close a circuit. 

Make-and-Break.— The operation of al- 
ternately completing and opening a cir- 
cuit. 

Make-Induced Current.— (1) The cur- 
rent produced by self-induction on the 
making or closing of a circuit. (2) The 
current produced by mutual induction in 
the secondary of an induction coil or 
transformer, on the making or comple- 
tion of the circuit of the primary. 

Making Earth. — In telegraphy, ground- 
ing. 

Making the Primary.— Closing the cir- 
cuit of the primary. 

Making-Up Batteries. — Joining voltaic 
cells in series or in parallel. 

Manganin. — A high-resistivity metal of 
very low resistivity temperature-coeffi- 
cient. 

Mangin Projector. — A special form of 
search-light projector. 

Mangin Reflector. — A special form of 
dioptric reflector employed in connection 
with the Mangin projector, consisting of 
a circular glass reflector, silvered at the 
back, and whose inner and outer or front 
and back surfaces are botli spherical. 

Manganin Resistance. — A resistance 
made of manganin wires, strips, or sheets. 

Man-Hole Compartment of Conduit. 
A man-hole provided in a conduit for 
affording access to the same. 

Man-Hole of Conduit.— An opening com- 
municating from the surface of the road- 



Man.] 



846 



Mas, 



bed with an underground conduit, of suf- 
ficient size to admit a man. 

Manometer. — An apparatus for measur- 
ing the tension or pressure of gases. 

Manometrie. — Of or pertaining to a mano- 
meter. 

Man-Power. — A unit of power equal to 
the one-tenth of a horse-power, or about 
75 watts. 

Manual Alarm, — A fire alarm operated 
by hand-power. 

Manual Igniting Device.— (1) A pen- 
dent electric gas-lighting burner. (2) An 
electric gas igniter operated by hand. 
(3) A manual mine exploder. 

Manual Repeater.— A telegraphic re- 
peater which is controlled or operated by 
hand, as distinguished from an automatic 
repeater. 

Manual Telegraphic Transmission.— 
Transmission by hand, as distinguished 
from automatic or machine transmission. 

Manual Translation.— The translation, 
especially in submarine telegraphy, of a 
message from one circuit to another, by 
an operator who transmits to the second 
circuit, direct from signals received on the 
first, without writing down or transcrib- 
ing the messages. 

Marconi Rays. — Electro-magnetic waves 
employed in the Marconi system of wire- 
less telegraphy. 

Marconi "Waves. — Electromagnetic 
waves employed in the Marconi system 
of wireless telegraphy. 

Margin of Relay Adjustment.— The 
range of alteration permissible in the ad- 
justment of the armature of a relay with- 
out interfering with the working of the 
instrument. 

Marine Galvanometer.— (1) A form of 
Thomson reflecting galvanometer, heavily 
encased in iron, devised for use on steam- 
ships where the motion of magnetized 
masses of iron would seriously disturb 
the reading of ordinary instruments. 
(2) Any form of galvanometer suitable 
for use on board ship. 

Marine Junction-Eos:.— A water-tight 
junction box for effecting junctions be- 
tween mains, or mains and branches, on 
board ship. 

Marine Lamp-Socket.— A form of spring 
socket for flexibly supporting an incan- 
descent lamp on board ship. 

Marine Search-Light or Lamp.— An 
electric search-light suitable for use at 
sea. 

Marine Switch. — A water-tight switch in 



an incandescent lamp, fixture, or circuit, 
on board ship. 

Marine Voltmeter.— A form of voltmeter 
suitable for use on a ship. 

Mariner's Compass.— (1) A compass 
mounted in such a manner as to be service- 
able on board ship. (2) A name often ap- 
plied to an azimuth compass. 

Mark Buoy. — In submarine cable work, a 
buoy moored to the bottom of the sea by a 
mushroom anchor, and placed to mark 
a certain position, as distinguished from 
a cable buoy which is moored to the end 
of a cable. 

Marked End of Magnet.— A name for- 
merly applied to the north-seeking pole of 
a magnet. 

Marked Pole of Magnet.— A term some- 
times applied to the north-seeking pole 
of a magnet. 

Markers.— Colored flags or signal lights, 
usually green, displayed in systems of 
block railroad-signalling, in order to avoid 
accident from the train breaking in two. 

Marking Current.— The current em- 
ployed in automatic telegraphy to produce 
the dots and dashes of the Morse alphabet, 
as distinguished from the spacing current 
or that employed to leave spaces between 
such characters. 

Marking Disc. — In a Morse ink-writer, 
the rotating inking disc, which marks the 
signals. 

Mass. — The quantity of matter contained 

in a body. 
Mass Attraction. — The mutual attraction 

exerted between masses of matter. 

Mass Specific-Resistance.— (1) Specific 
resistance referred to unit mass instead of 
unit volume. (2) The resistance taken be- 
tween the ends of a cylindrical wire of 
definite length, usually one metre, con- 
taining a mass, usually a gramme. (3) 
The resistance of a metre-gramme. 

Massage. — The treatment of the bod b] 
kneading, rubbing or friction, for the 
purpose of effecting changes in its general 
nutrition. 

Mass, Electric. —A mathematic; 

tion for quantities of electricity which are 
so distributed as to produce electrostatic 
forces in conformity with the laws of 
gravitational forces, and, therefore, cor- 
responding to material masses. 

Mass Specific Resistance.— (1) The re- 
sistance of a known mass of a material ; 
namely, one gramme, in the form of a 
circular sectioned wire one meti n 
length. (2) The resistance of a ioot-grain. 



Mas.] 



847 



[Mea. 



Mast- Arm for Arc-Lamp.— A movable 
arm or bracket provided at the top of a 
pole for the support of a lamp arranged 
for the ready lowering of the lamp for 
re-car boning. 

Mast Compass. — A compass secured to the 
mast of a ship, at an elevation sufficient 
to considerably reduce the component of 
local attraction from the ship's magnetiza- 
tion. 

Master Clock. — A central or controlling 
clock employed in a system of electric 
time distribution, from which time is 
transmitted to the secondary clocks in its 
circuit. 

Mate of Wire in Twisted Pair.— (1) One 
of the wires of a twisted pair. (2) The 
conjugate member of a wire in a twisted 
pair. 

Matt. — (1) A word employed in electro- 
plating to designate the appearance pre- 
sented by an electro-plating of silver in 
which the deposit is interlaced and closely 
massed together. (2) A fused mass of im- 
pure copper employed as the raw material 
in electrolytic refinement. 

Matter. — Anything which occupies space 
in three dimensions and prevents other 
matter from simultaneously occupying 
the same space. 

Matter, Electric— A term formerly ap- 
plied to the matter which was believed to 
constitute the effluvia formerly assumed 
to pass off from an electrified body. 

Matteucci's Muscular Pile.— A pile 
formed by arranging a series of muscles 
so that their exterior and interior surfaces 
are alternately connected. 

Matthiessen's Metre-Gramme-Stand- 
ard. — (1) A standard of resistivity or con- 
ductivity in metallic wires. (2) The re- 
sistance of a wire one metre in length, 
and of such a diameter as would cause the 
wire to weigh one gramme. (3) Accord- 
ing to the American Institute of Electrical 
Engineers Committee, the standard estab- 
lished by Matthiessen for a metre-gramme 
of soft copper, 0.1417 international ohm at 
0° C, or 0.1501 international ohm at 15° C. 

Matthiessen's Mile-S tandar d.— A 
standard of resistance equal to the resist- 
ance of one mile of pure copper wire one- 
sixteenth of an inch in diameter, at 15.5° 
Cent. (No longer used.) 

Matthiessen's Unit of Resistance. — 
Matthiessen's mile-standard . 

Maturing of Call. — In a system of tele- 
phony where a number of calls have been 
received at an exchange and recorded for 



execution in order, the time at which any 
particular call is reached in its order. 

Maximum. — (1) Possessing the greatest 
value. (2) In a continuous succession of 
values, a value greater than that which 
precedes or follows it. 

Maximum Activity of Motor.— (1) The 
activity of a motor when working at its 
greatest possible rate, or the activity when 
the useful work done is equal to half the 
energy expended. (2) The full-load ac- 
tivity of a motor. (3) The maximum 
available activity of a motor. 

Maximum Efficiency of Transformer. 
The highest efficiency obtainable from a 
transformer. 

Maximum Horizontal Intensity of 
Light. — The greatest intensity of light 
emitted by a source in a horizontal direc- 
tion. 

Maximum Magnetization.— A term 
sometimes used for magnetic saturation. 

Maximum Negative-Elongation. — The 
position of a vibrating body when it is at 
the extremity of its path on the negative 
side. 

Maximum Positive-Elongation.— The 
position of a vibrating body when it is at 
the extremity of its path on the positive 
side. 

Maximum Starting-Current of Motor. 
The highest value the starting current 
of a motor attains. 

Maximum Traction Truck.— A form of 
double car-truck. 

Maxwell's Electro-Magnetic Theory 
of Light. — (1) A hypothesis for the cause 
of light based on the relations existing 
between the phenomena of light and 
those of electro-magnetism. (2) A hy- 
pothesis that regards light as a purely 
electro-magnetic phenomenon. 

Mclntire's Parallel-Sleeve-Telegraph- 
ie Joint. — A joint for telegraphic or other 
wires, in which the ends to be joined are 
slipped into sleeves or parallel tubes, which 
are afterwards filled with solder. 

Mean. — (1) Average. (2) A quantity hav- 
ing an intermediate value between others. 

Mean Annual Station-Current.— The 
average current delivered by a station 
throughout the year. 

Mean Current.— (1) The time average of 
a current strength. (2) In an alternating- 
current circuit, the time average of a cur- 
rent strength without regard to sign or 
direction. 

Mean Electromotive Force.— (1) The 
average electromotive force. (2) In an 



Mea.] 



848 



[Med. 



alternating-current circuit, the time aver- 
age of the E. M. F. without regard to sign 
or direction. 

Mean Horizontal Intensity of Light.— 
The average intensity of light in a hori- 
zontal plane containing the source. 

Mean Illumination.— The average illu- 
mination. 

Mean Load-Current. — The average load- 
current. 
Mean Spherical Candle-Power.— (1) An 

average candle-power numerically equal 
to the total quantity of light emitted by 
a point source divided by 12.566. (2) The 
average candle-power of a source taken 
at all points of the surface of a sphere. 

Mean Spherical Intensity of Light.— 
The mean spherical candle-power. 

Mean Quadratic Current.— A term pro- 
posed for the effective strength of an 
alternating current. 

Mean Thermal Capacity for Heat.— The 
average capacity for heat. 

Measurement of Resistance.— The de- 
termination of the value of an electric 
resistance by any suitable means. 

Measurements, Electric— Determina- 
tions of the values of the electromotive 
force, resistance, current, capacity, 
energy, etc., in any electric circuit or 
instrument. 

Measuring Current. — (1) The current by 
which an electrical measurement is made. 
(2) A testing current. 

Mechanical Air Pump.— A mechanical 
device for exhausting or removing the air 
from any vessel. 

Mechanical Characteristic of Motor.— 
A term sometimes employed for the curve 
of the torque and speed of a motor as co- 
ordinates. 

Mechanical Circuit-Closer. — (1) Any 
circuit-closer not operated electrically. 
(2) An automatic circuit-closer not oper- 
ated electrically. 

Mechanical Closer. — A mechanical cir- 
cuit-closer. 

Mechanical Cut-Out — (1) Any cut-out 
not operated electrically. (2) An auto- 
matic cut-out not operated electrically. 

Mechanical Depolarizer of Voltaic 
Cell. — A method for removing the gas 
collected on the negative plate of a voltaic 
cell by the mechanical agitation of the 
liquid. 

Mechanical Equivalent of Heat.— The 
amount of mechanical energy converted 
into heat that would be required to raise 
the temperature of a unit mass of water 



one degree of the thermometric scale. 

(2) The quantity of energy mechanically 

equivalent to one heat unit. 
Mechanical Equivalent of Light.— The 

quantity of energy contained in one unit 

of light. 
Mechanical Frictions of Dynamo.— 

The journal, brush and air frictions of a 

dynamo. 

Mechanical Magnet Lightning - Ar- 
rester. — A mechanical device operated 
by an electro-magnet for the extinguish- 
ment of the arc established by a light- 
ning flash. 

Mechanical Mine. — A submarine mine 
that is fired when struck by a passing 
ship through the action of some contriv- 
ance contained within the torpedo itself, 
and having no connection whatever with 
the shore. 

Mechanical Recording Meter.— A me- 
chanically operated recording meter. 

Mechanical Seal. — A mechanically made 
seal of the chamber of an incandescent 
lamp. 

Mechanical Telegraph.— Any form of 
telegraphy by which communication is 
established by mechanical means. 

Mechanical Telegraphic Interrupter. 
A form of mechanical telegraphic 
sounder for learners, where no battery is 
required. 

Mechanical Telephone.— A wire or 
string telephone, operated by longitudinal 
vibrations transmitted through a wire or 
string. 

Mechanical Throwback - Indicator. — 

An annunciator drop provided with a 
drop that is mechanically replaced. 

Mechanical Torpedo.— A torpedo that 
is exploded by percussion against any 
obstacle. 

Mechanical Vibrator. — (1) A mechani- 
cally operated contact-breaker. (2) A 
mechanical means for obtaining the ejec- 
tion of the ink from the siphon in a siphon 
recorder. 

Mechanical "Work. — (1) The product of a 
force by the distance through which the 
force acts. (2) The expenditure of energy 
required for any change in the configura- 
tion of a material system. 

Medical Battery.— A medical induction 
coil. 

Medical Electrician. — An electro-thera- 
pist. 

Medical Induetion-Coil. — An induction 
coil used for medical purposes. 

Medical Magneto-Electric Apparatus. 



Meg.] 



849 



[Met. 



A term applied to small magneto-electric 
machines employed in electro-therapeutics 
for the production of uncommuted or far- 
adic currents. 

Meg or Mega. — A prefix for one million 
times. 

Mega-Dyne. — One million dynes. 

Mega-Joule. — One million joules. 

Mega-Lines. — One million lines. 

Megalascope, Electric. — An apparatus 
for the medical exploration of the cavi- 
ties of the body. 

Mega- Volt. — One million volts. 

Mega- Weber. — One million webers. 

Megerg. — One million ergs. 

Megohm. — One million ohms. 

Megohm Box. — A resistance box contain- 
ing a resistance or resistances equal to a 
megohm. 

Megohm Galvanometer.— A galvano- 
meter which gives unit deflection through 
a resistance of one megohm in circuit 
with one volt. 

Megohm Mile. — A unit of linear insula- 
tion resistance equal in value to the pro- 
duct of a megohm by a mile, and such as 
is possessed by a mile of wire, the insula- 
tion of which is one megohm. 

Melting Points of Metals.— Tempera- 
tures at which metals fuse. 

Membrane Diffusion.— Osmose. 

Membrane Telephone-Receiver.— An 
early form of telephone receiver whose 
diaphragm was formed of a sheet of gold- 
beater's skin. 

Mercurial Air-Pump.— (1) A device for 
obtaining a high vacuum by the use of 
mercury. (2) The Geissler or Sprengel 
mercury pumps. 

Mercurial Connection.— A form of read- 
ily adjustable connection obtained by 
providing the poles of one piece of appa- 
ratus with cups or cavities filled with 
mercury, in which the terminals of anoth- 
er piece of apparatus are dipped, in order 
readily to place them in circuit with each 
other. 

Mercurial Contact.— An electric contact 
effected through the medium of mercury. 

Mercurial Phosphorescence.— A term 
formerly employed for the light produced 
by the motion of a column of mercury in 
an exhausted tube. 

Mercurial Temperature - Alarm.— An 
instrument for automatically telegraph- 
ing an alarm by means of a mercurial 
contact, on a pre-determined change of 
temperature. 
54 



Mercurial Thermostat.— A thermostat 
operating by the expansion of a mercury 
column. 

Mercury Break.— A form of circuit 
breaker operated by the removal of a con- 
ductor from a mercurial surface. 

Mercurial Commutation.— A change in 
the direction of a current obtained by 
means of a mercurial connection. 

Mercury Cup.— A cup partly filled with 
mercury employed as a mercurial contact. 

Mercury Gauge. — A vacuum or pressure 
gauge whose indications are dependent 
on the height of a mercury column. 

Mercury Piezometer.— An instrument 
employed in cable work for measuring 
the depth of the ocean, by recording the 
pressure at the lowest point reached by 
the sounding lead, and used as a check 
upon the length of sounding line. 

Mercury Switchboard.— A switchboard 
in which connections are effected by mer- 
curial contacts. 

Mercury Tube.— (1) A sealed glass tube 
containing mercury arranged to emit 
fluorescent light when agitated. (2) A 
resistance formed of a thread of mercury 
contained in a tube. 

Meridional. — Of or pertaining to a meri- 
dian. 

Mesh Grouping of Polyphase Circuit. 
A triangular or delta-connection of three- 
phase coils as distinguished from a star 
connection. 

Message Wire. — A line or wire employed 
in block sj'stems for railroads extending 
along the road and used for local tele- 
graphic business. 

Messenger Call-Box. — A district call- 
box. 

Messenger Rope. — (1) In cable-work a 
rope drive for operating a drum or winch 
at a distance. (2) A rope supporting 
guide sheaves. 

Messenger Strand.— A strand in a mes- 
senger wire. 

Messenger Wire of Aerial Cable.— The 
supporting wire or rope from which the 
cable clips employed in the suspension of 
an aerial cable are supported. 

Metal-Cased Blake Transmitter.— A 
form of telephone transmitter provided 
with a metallic covering. 

Metallic. — Of or pertaining to a metal. 

Metallic Arc. — An arc formed between 
metallic electrodes. 

Metallic Circuit. — A circuit which is 
metallic throughout, in contradistinction 
to an earth-return circuit. 



Met.] 



850 



[Met, 



Metallic-Circuit Plug.— In a telephone 
switchboard, a plug which makes contact 
both at its tip and at its sleeve, so as to 
close a double or metallic circuit con- 
nected therewith by a twin cord. 

Metallic Coating.— An electrolytically 
deposited coating of metal. 

Metallic Connection. — Connection by 
means of a metallic conductor. 

Metallic Conducting Joint. — A joint in 
a conductor in which a continuity of con- 
ducting power is secured. 

Metallic Conduction. — The conduction 
of electricity through a metal, in contra- 
distinction to its conduction through an 
electrolyte. 

Metallic Conductor. — A conductor 
formed of a metal. 

Metallic Contact.— (1) A contact of a 
metallic conductor obtained by bringing 
it into firm connection with another 
metallic conductor. (2) Contact between 
metal and metal. 

Metallic Contact of Cable.— A complete 
contact between the copper conductor of a 
submarine cable and its metallic sheath. 

Metallic Cross. — A fault due to the actual 
contact between two or more wires or 
conductors, so that the current from one 
line passes to another. 

Metallic Electric Conduction.— (1) A 
conduction of electric energy by means 
of metallic substances. (2) Metallic con- 
duction. 

Metallic Electrodes. — Variously shaped 
pieces of metal employed for electro- 
therapeutic electrodes. 

Metallic Electrolysis.— A form of cata- 
phoretic medication in which a metallic 
electrode, connected to the positive pole 
of a continuous-current source, is 
brought into contact with the part to be 
treated, while the negative pole is applied 
to some other part of the body, and the 
metallic salt formed by electrolysis at the 
anode is cataphoretically driven into the 
tissues beneath the electrode. 

Metallic Filament. — A metallic wire em- 
ployed as a filament of an incandescent 
lamp. 

Metallic Reluctivity.— (1) The reluc- 
tivity of a metallic substance. (2) In a 
magnetic substance the reluctivity of the 
substance as considered independently of 
the reluctivity of the ether in its mass. 

Metallic Resistance.— A term some- 
times applied to the resistance of wires 
or conductors, in contradistinction to 
the resistance of insulating materials. . 



Metallic Resistivity.— The resistivity of 

a metallic substance. 
Metallic Solution.— A solution of a 

metallic salt. 

Metallization. — Rendering a non-conduct- 
ing surface electrically conducting by 
covering it with a metallic coating so as 
to enable it to be readily electro-plated. 

Metallizing.— Subjecting to the process of 
metallization. 

Metallo-Chromes.— (1) A name some- 
times given to Nobili's rings. (2) Pris- 
matic colors which appear when a salt of 
lead, such as an oxide, is electrolyzed 
under certain circumstances. 

Metallurgy.— That branch of science 
which treats of the reduction or treat- 
ment of metallic ores or metals. 

Metamerism.— (1) A variety of isomerism. 
(2) The quality possessed by some chem- 
ical substances, differing in their proper- 
ties, although similar in their quantita- 
tive composition, owing to a difference of 
molecular construction or arrangement of 
atoms in the molecule. (3) A term used 
in distinction to polymerism. 

Meteorites. — Fragmentary solids that 
when attracted to the earth become in- 
candescent on their passage through its 
atmosphere. 

Meteorograph, Electric— An appa- 
ratus for automatically registering by 
electricity various meteorological values 
such as the indications of a barometer or 
thermometer, the direction and velocity 
of the wind, the value of the rain-fall, 
etc. 

Meteorology. — That branch of physics 
which treats of the phenomena of the 
atmosphere. 

Meteorology, Electric. — That branch 
of physics which treats of the electric 
phenomena of the atmosphere. 

Meter, Electric. — Any apparatus for meas- 
uring commercially the quantity of elec- 
tricity that passes in a given time through 
a consumption circuit. 

Meter-Motor. — (1) A small motor em- 
ployed in operating an electric meter. 
(2) A meter comprising a small motor. 

Meter Sealing Tool. — A tool for stamping 
a leaden seal which prevents the unin- 
dicated opening of a meter by an un- 
authorized person. 

Method of Recoil.— A method of measur- 
ing a discharge through a ballistic gal- 
vanometer by reversing the direction of 
its swing. 

Method of Slow Discharge.— An insu- 



Met.] 



851 



[Mic. 



lation test for a telegraphic line, based on 
the rate at which a charge leaks out 
when the conductor is left insulated. 

Methven Carburetter.— A device employ- 
ed in connection with a Methven screen, 
consisting of troughs of fine wire gauze 
filled with gasoline, so that the gas pas- 
sing through becomes charged with the 
vapor. 

Methven's Screen. — A vertical rectangu- 
lar metallic screen used in connection with 
a standard Argand burner as a photomet- 
ric standard. 

Metre. — A unit of length equal, approxi- 
mately, to one ten-millionth part of a 
quadrant of a meridian of the earth taken 
through Paris ; or, approximately, to 
39.37 inches, 

Metre-Bridge. — A slide form of Wheat- 
stone's bridge in which the slide wire is 
one metre in length. 

Metre-Candle. — (1) The illumination pro- 
duced by a standard candle at the distance 
of one metre. (2) A unit of illumination. 

Metre-Gramme.— (1) A unit of resistance 
equal to that of the resistance of a wire 
one metre in length weighing one 
gramme. (2) A standard of comparison 
of resistivit3 r or conductivity. (3) Mat- 
thiessen's metre-gramme standard of 
copper wire, which for soft copper wire, 
according to the committee of the Ameri- 
can Institute of Electrical Engineers, is 
0.1501 International ohm at 15° C. 

Metre-Millimetre. — A resistance stan- 
dard, consisting of a length of wire or 
other conductor, one metre long and 
having a diameter of one millimetre. 

Metric Factors.— The factors employed 
for the conversion of the metric system 
units into those of other systems. 

Metric Horse-Power.— A unit of power 
in which the rate-of-doing-work is equal 
to 75 kilogramme-metres per second. 

Metric System of Weights and Meas- 
ures. — A system of weights and meas- 
ures based on the metre and the 
gramme. 

Mho. — (1) The practical unit of conduct- 
ance. (2) Such a conductance as is equal 
to the reciprocal of one ohm. (3) A unit 
of electric conductance of the value of 
10" 9 absolute units. 

Mho-Box. — A conductance box, or box 
containing adjustable conductance, 
graduated in mhos. 

Mhometer. — An instrument for measur- 
ing the value of a conductance in mhos. 

Mica. — (1) A refractory, mineral substance 
employed as an insulator. (2) A double 



ilicate of alumina or magnesia and 
potash or soda. 
Micanite. — A variety of insulating 
material made from and built up of small 
mica sheets bound together by some in- 
sulating cement. 

Micro. — A prefix for the one-millionth. 

Micro-Ampere.— The millionth of an am- 
pere. 

Micro- Coulomb. — The millionth of a 
coulomb. 

Micro-Farad.— The millionth of a farad. 

Micro- Gilb. — A contraction for micro- 
gilbert. 

Micro-Gilbert.— The millionth of a gilbert. 

Micro Glow-Lamp. — A miniature incan- 
descent lamp. 

Micro-Graphophone.— A modification of 
the phonograph, in which a number of 
separate non-metallic diaphragms are 
caused to act on a single diaphragm, for 
the purpose of obtaining stronger vibra- 
tions of the same. 

Micrometer Caliper. — A micrometer wire 
gauge. 

Micrometer Eye-Piece.— An eye-piece of 
a telescope, microscope or other optical 
apparatus provided with a micrometer. 

Micrometer Microscope. — A microscope 
provided with a micrometer eyepiece. 

Micrometer Wire-Gauge. — A sensitive 
form of wire gauge, usually constructed 
with a fine thread screw, having a gradu- 
ated head for close measurements of wire 
diameters. 

Micron. — A unit of length equal to the 
millionth part of a meter. 

Microhm. — The millionth of an ohm. 

Microphone. — A form of contact tele- 
phone-transmitter employed in connec- 
tion with a telephone for rendering faint 
or distant sounds distinctly audible. 

Microphone Induction-Coil. — An in- 
duction coil employed in connection with 
a microphonic telephone transmitter. 

Microphone Relay. — A device for auto- 
matically repeating a telephonic message 
over another wire. 

Microphonic. — Of or pertaining to the 
microphone. 

Microphonic Contact.— A loose contact 
capable of being employed for a telephone 
transmitter. 

Microscope. — An optical instrument for 
the examination of objects too minute 
to be seen by the unaided eye. 

Microscopic— (1) Of or pertaining to the 



Mic] 



852 



[Mix, 



microscope. (2) Of very minute dimen- 
sions. 

Microscopy. — The art of microscopic ex- 
amination. 

Micro-Seismograph.— An electric appa- 
ratus for graphically recording the direc- 
tion and intensity of faint earthquake 
shocks or earth tremors. 

Micro - Tasimeter. — An apparatus in- 
vented by Edison for measuring minute 
differences of temperature, or of moisture, 
by the resulting differences of pressure 
upon a carbon button. 

Micro-Telephone. — (1) A convenient 
form of writing table-set telephone used 
by some exchange operators in quiet ex- 
changes, or in busy exchanges, at night. 
(2) A form of combined transmitter and 
receiver. (3) A small semi-portable tele- 
phone set. 

Micro-Volt. — The one-millionth of a volt. 

Migration of Ions. — A term employed to 
express the movement of the ions in an 
electrolyte undergoing electrolysis. 

Migration Values of Ions. — The veloci- 
ties of the ions. 

Mil. — A unit of length used in measuring 
the diameter of wires equal to the one- 
thousandth of an inch. 

Milammeter. — A milli-ammeter. 

Mild Steel.— A term employed for soft 
steel. 

Mil-Foot. — (1) A resistance standard con- 
sisting of a foot of wire, or other con- 
ducting material, one mil in diameter. 
(2) A standard of comparison of resistiv- 
ity or conductivity of wires. 

Milli. — A prefix for the one-thousandth 
part. 

Milli- Ammeter. — A milli-ampere meter. 

Milli-Ampere. — The thousandth of an 
ampere. 

Milli-Ampere Meter. — An ampere meter 
graduated to read in milli-amperes. 

Milli-Calorie.— (1) The thousandth of a 
calorie. (2) The small calorie. 

Milli-Oersted. — The thousandth of an 
oersted. 

Milli-Volt.— The thousandth of a volt. 

Mimosa Sensitiva. — A sensitive plant 
whose leaves fold or shut up, either when 
touched, or when traversed by electric 
currents. 

Mine Explorer, Electric. — A small 
magneto-electric generator employed in 
the direct firing of blasts. 

Miniature Incandescent Lamp. — A 
very small incandescent lamp, suitable for 



decorative, microscopic, dental or surgical 
purposes. 

Mining, Electric. — The application of 
electricity to mining. 

Mining Locomotive, Electric. — An elec- 
tric locomotive employed in mining opera- 
tions. 

Minotto's Voltaic Cell.— A form of Dan- 
iells' cell employing a flat copper plate at 
the bottom of the cell beneath a mass of 
copper sulphate crystals, the cell being 
then filled with wet sand, or wet sawdust, 
on which rests the zinc plate. 

Minus Charge. — A negative charge. 

Miophone. — An apparatus, based on the 
use of the microphone, employed for the 
medical examination of the muscles. 

Mirror Galvanometer. — A galvanometer 
whose readings are obtained by the move- 
ments of a spot of light reflected from 
a mirror attached to the needle or its sus- 
pension system. 

Mirror Magnetometer. — A magneto- 
meter whose needle or suspension system 
is provided with a mirror. 

Mirror Receiver in Cable Telegraphy. 
In cable telegraphy, a mirror galvano- 
meter employed as a receiver. 

Mirror Receiving-Instrument.— (1) A 

receiving signalling instrument employed 
in submarine telegraphy, whose needle or 
suspension system is provided with a 
mirror. (2) A mirror galvanometer mod- 
ified for use in telegraphing. 

Mirror Speaking - Instrument. — A 

mirror receiving-instrument. 

Mixed Charge Test for Capacity.— A 
test employed for determining the capac- 
ity of a submarine cable, in which an 
unknown capacity is charged to one po- 
tential, a known capacity is charged to 
an opposite potential, and the two charges 
are then mixed with the object of neutral- 
ization. 

Mixed Circuit. — (1) In telephony, a circuit 
partly metallic and partly earth-circuited. 
(2) A term sometimes applied to the com- 
bination of a series and a multiple circuit. 

Mixed-Circuit Board.— (1) A telephone 
switchboard arranged for the reception 
and inter-connection of metallic circuits 
and ground-return circuits. (2) A mixed- 
circuit switchboard. 

Mixed-Circuit Switchboard.— A tele- 
phone switchboard connected with mixed 
circuits or circuits of which some are 
metallic and others are provided with 
ground return. 

Mixed Distribution.— (1) A distribution 



Mix.] 



853 



[MoL 



of electric energy which combines both 
series and parallel distribution. (2) 
Series-parallel or parallel-series distribu- 
tion. 
Mixing Key. — The key employed in simul- 
taneously charging a cable and a con- 
denser for producing the mixed charge 
employed in the mixed-charge test for 
capacity. 

Mixture Photometer. — A photometer 
combining the principles of the compensa- 
tion and the polarization photometer. 

Moderate-Speed Generator. — A gener- 
ator designed to be run at a moderate 
speed, as distinguished from a slow-speed 
generator. 

Moderate-Speed Motor.— A motor de- 
signed to work at a moderate speed, as 
distinguished from a slow-speed motor. 

Modulus of Elasticity.— (1) The ratio of 
the simple stress required to produce a 
small elongation or compression in a rod 
of unit area of normal cross-section, to 
the proportionate change of length pro- 
duced. (2) Young's modulus. 

Moist Electrode. — A therapeutic elec- 
trode moistened with water or some other 
liquid. 

Moist Voltaic Cell.— A form of the so- 
called dry voltaic cell. 

Moisture-Proof Insulation.— (1 ) Water- 
proof insulation. (2) A type of insulation 
which is not strictly water-proof, but 
which is capable of being immersed for 
a short time without suffering serious loss 
of insulation. 

Molar Attraction. — (1) Mass attraction, 
as distinguished from molecular attrac- 
tion or cohesion. (2) Gravitation. 

Molar Vibration of Telephone Dia- 
phragm. — The mass vibration of a tele- 
phone diaphragm, as distinguished from 
molecular vibration. 

Molecular. — Of or pertaining to the mole- 
cules. 

Molecular Accommodation. — A re- 
arrangement of the molecules of a para- 
magnetic substance resulting, by constant 
repetition, in a decrease in the hysteretic 
friction in cyclic magnetization. 

Molecular Agitation. — Rapid mechanical 
vibration given to a mass of iron for the 
purpose of reducing its magnetic hyster- 
esis. 

Molecular Attraction.— (1) The mutual 
attraction existing between neighboring 
molecules. (2) Cohesion or adhesion. 

Molecular Bombardment.— (1) The col- 
lisions which occur between neighboring 



molecules, and which are accentuated and 
accelerated by heat. (2) The forcible rec- 
tilinear projection from the negative 
electrode of the residual gaseous molecules 
in an exhausted vessel, on the heating of 
the same, or on the passage through it of 
an electric discharge. 
Molecular Chain. — A polarized chain of 
molecules that is assumed by Grothuss' 
hypothesis to exist in an electrolyte during 
its electrolytic decomposition, or in a vol- 
taic cell on the closing of the circuit. 

Molecular Conductance.— The conduct- 
ance offered by a mass of an electrolyte 
equal to its molecular weight in grammes, 
when contained in an insulating vessel 
furnished with two opposite parallel con- 
ducting sides or faces, distant one centi- 
metre apart. 

Molecular Conductivity of Electro- 
lyte. — (1) The conductance possessed by 
one gramme-molecule of an electrolyte 
when placed between electrodes one 
centimetre apart. (2) A term sometimes 
used for molecular conductance. 

Molecular Configuration.— A term for 
the molecular groupings or the relative 
position of the molecules in a magnetizable 
substance. 

Molecular Currents.— (1) A term some- 
times employed for Amperian currents. 
(2) Atomic currents. 

Molecular Decomposition.— Decomposi- 
tion of a molecule. 

Molecular Dissociation.— (1) Molecular 
decomposition. (2) The disruption of 
molecules into ions, or atoms. 

Molecular Encounter.— A collision be- 
tween two molecules of a gaseous sub- 
stance that takes place during the to-and- 
fro movements they describe in accord- 
ance with the kinetic theory of gases. 

Molecular Heat. — The number of calories 
of heat required to raise one gramme- 
molecule of a substance one degree Cen- 
tigrade. 

Molecular Kinetics.— The kinetics of the 
molecules. 

Molecular Magnetomotive Forces.— 
(1) The magnetomotive forces inherently 
possessed by the molecules. (2) The 
aligned or structural-magnetomotive 
force as distinguished from the prime 
magnetomotive force. 

Molecular Magnetism.— (1) The mag- 
netism resulting from molecular magneto- 
motive forces. (2) The inherent magnetic 
flux in a molecule of a magnetic substance. 

Molecular Magnetization. — The in- 



Mol.] 



854 



[Mon. 



herent magnetization possessed by the 
molecules. 

Molecular Magnets. — The inherently 
magnetized molecules. 

Molecular Oscillations. — To-and-fro 
movements or oscillations of the mole- 
cules. 

Molecular Range. — The distance at which 
the molecules of matter continue to exert 
a sensible attraction on one another. 

Molecular Repulsion.— The mutual re- 
pulsion existing between molecules arising 
from their kinetic energy. 

Molecular Resistance. — (1) The resistance 
offered by a mass of an electrolyte equal 
to its molecular weight in grammes, when 
contained in an insulating vessel having 
two opposite parallel conducting faces 
distant one centimetre apart. (2) The re- 
sistance of one gramme-molecule of an 
electrolyte when brought between two 
electrodes one centimetre apart. 

Molecular Rigidity.— The resistance 
offered by the molecules of a substance 
to rotation or displacement. 

Molecular Shadows. — The comparatively 
dark spaces on those portions of the walls 
of a Crookes tube, which have been pro- 
tected by molecular bombardment by 
suitably interposed screens. 

Molecular Streams. — Eectilinearly di- 
rected streams of molecules, thrown off 
from the cathode of a high- vacuum tube, 
under the influence of heat or electric 
discharges. 

Muscular Theory of Muscle and 
Nerve Currents. — A theory which re- 
gards every muscle or nerve fibre as 
formed of a number of series-connected 
electromotive molecules surrounded by a 
neutral conducting fluid. 

Molecular Transfer of Heat.— The 
transfer of heat by means of molecular 
vibrations. 

Molecular Vibration of Telephone 
Diaphragm. — The molecular vibration 
of a telephone diaphragm under the in- 
fluence of the changes in the magnetiza- 
tion of the telephone magnet, as distin- 
guished from its molar vibration. 

Monochromatic Photometry.— (1) The 
photometry of monochromatic lights. 
(2) Photometry in which the spectra or the 
compositions of the lights to be compared 
are similar. 

Molecular Voltaic-Couple.— A voltaic 
couple formed of the atoms or radicals of 
a molecule. 

Molecular Vortices. — The vortices in the 
ether which, according to a particular 



theory, are assumed to constitute the 
molecules, atoms or ultimate particles of 
matter. 

Molecule.— (1) The smallest quantity of a 
compound substance that can exist as such. 
(2) A group of atoms whose chemical bonds j 
or affinities are completely satisfied. 

Molten-Platinum Lamp.— The violle or 
molten platinum standard. 

Molten-Platinum Standard of Light. — 

(1) The violle. (2) The practical standard 
of white light adopted at the Electrical 
Congress of Paris, in 1884, and defined as 
the total quantity of light emitted by a 
square centimetre of molten platinum at 
the temperature of its solidification. 

Moment.— (1) Torque. (2) The product of 
any quantity, directed with respect to an 
axis, and the perpendicular distance of its 
direction from that axis. 

Moment of a Couple.— (1) The torque or 
effective power of a couple. (2) The in- 
tensity of one of the forces in a couple, 
multiplied by the perpendicular distance 
between the direction of the forces. 

Moment of a Magnet.— The polar length 
of a magnet multiplied by the intensity 
of magnetism of one of its poles. ' 

Momentary Current.— (1) A current that 
continues flowing but for a short time. 

(2) A current of brief duration. 

Momentum. — (1) The product of the mass 
of a moving body by its velocity. (2) 
Quantity of motion in a system. 

Monad Atom. — An atom whose valency 
or atomicity is one. 

Monovalent. — (1) Possessing a valency or 
atomicity of one. (2) Univalent, or mono- 
valent. 

Monoehord. — A sonometer. 

Monocular. — An eye-piece or glass, pro- 
vided for a single eye. 

Monophotal Arc-Light Regulator.— 
A term sometimes employed for an elec- 
tric arc-lamp in which the whole current 
passes through the arc-regulating mech- 
anism, and which is usually operated 
singly in circuit with a dynamo. 

Monocycler. — A monocyclic generator. * 

Monocyclic. — Of or pertaining to a mono- 
cycler, or to a monocyclic system. 

Monocyclic Alternator.— A monocyclic 
generator. 

Monocyclic Armature.— The armature 
of a monocyclic generator, provided with 
two sets of windings, one of which con- 
stitutes the main winding and corresponds 
to that of an ordinary uniphaser, while 



Mon.] 



855 



[Mot, 



the second is of smaller cross-section and 
fewer turns, and is connected to the centre 
of the main winding in diphase relation 
to it. 
Monocyclic Circuit.— The circuit of a 
monocyclic generator. 

Monocyclic Generator.— A form of 
polyphase generator provided with a mo- 
nocyclic armature. 

Monocyclic Motor. — A. form of induc- 
tion motor suitable for use on monocyclic 
circuits. 

Monocyclic System.— (1) A system of 
alternating-current distribution suitable 
for electric lighting with the additional 
capability of operating triphase induction 
motors. (2) A system for the distribution 
of alternating currents employing three 
wires, between two of which an ordinary 
Uniphase pressure is maintained, while 
between either of them and the third, 
there is a diphased pressure. 

Monogenic Charge.— A name proposed 
for such a distribution of an electric 
charge in which the sign of the surface 
density is everywhere the same. 

Monophase Generator.— An alternator 
producing uniphase or monophase cur- 
rents. 

Monophase Motor. — A uniphase motor. 

Mooring Chain.— A chain employed for 
the mooring of a cable buoy. 

Mopped. — Subjected to the action of a pol- 
ishing mop. 

Mordey Effect. — A decrease in the value 
of the hysteresis in the iron of a dynamo 
armature at full load. 

Morse Alphabet. — The Morse telegraphic 
alphabet. 

Morse Code. — The Morse telegraphic al- 
phabet. 

Morse Embosser. — A Morse register. 

Morse Ink- Writer. — The name some- 
times given to a Morse inker. 

Morse Inker. — A form of telegraphic ink- 
writer printing signals in the Morse code. 

Morse Push. — A term sometimes employed 
for a double-contact push. 

Morse Recorder.— An apparatus for au- 
tomatically recording the dots and dashes 
of the Morse telegraphic dispatch, on a 
fillet of paper drawn under an indenting 
or marking point on a striking lever con- 
nected with the armature of an electro- 
magnet, as distinguished from a Morse 
inker. 

Morse Register. — A Morse recorder. 

Morse System of Telegraphy.— A sys- 



tem of telegraphy in which makes and 
breaks, occurring at intervals corre- 
sponding to the dots and dashes of the 
Morse alphabet, are received by an electro- 
magnetic sounder, or other receiver. 

Morse Tapper.— A form of telegraphic 
key provided with two contacts, one in 
front, and another on the back, so arranged 
that the depression of the key makes one 
contact and breaks the other. 

Morse Writer.— A form of telegraphic 
Morse ink-writer. 

Morse Telegraphic- Alphabet.— Various 

groupings of clots and dashes or deflec- 
tions of a needle to the right and left, em- 
ployed for representing the letters of the 
alphabet or other signs. 

Morse Telegraphic-Sounder. — An elec- 
tro-magnet, the movements of whose ar- 
mature lever produce the audible sounds 
corresponding to the dots and dashes of 
the Morse code. 

Motional Electric Force.— The electric 
force induced by the motion of magnetic 
flux, or of the medium supporting the 
flux. 

Motional Magnetic Flux. — Magnetic 
flux produced by the motion of an elec- 
trostatic charge, or of electrostatic flux. 

Motorneer. — A word proposed for motor- 
man. (Not in general use.) 

Motor Armature.— The armature of an 
electric motor. 

Motor Car, Electric — An electrically 
propelled car. 

Motor Circuit. — A circuit containing an 
electric motor. 

Motor-Controlling Rheostat.— A rheo- 
stat connected with a motor, and em- 
ployed for starting the motor or for 
regulating its speed. 

Motor Cut-Out. — A cut-out provided in 
the circuit of a motor for the purpose of 
throwing it out of circuit. 

Motor -Dynamo. — (1) An electrically 
driven motor, rigidly connected to the 
armature of a dynamo, and employed for 
transforming or changing the pressure of 
a direct-current circuit. (2) The combi- 
nation, in a continuous-current generator 
of a motor and a dynamo, in separate 
structures, mechanically connected to 
form a single machine or structure. 

Motor-Electromotive Force.— A term 
proposed for the counter-electromotive 
force of a motor. 

Motor, Electric. — A device for transform- 
ing electric power into mechanical power. 

Motor-Generator. — (1) A motor coupled 



Mot.] 



856 



[Mul 



to a generator. (2) A motor-dynamo. 
(3) A form of secondary generator. 

Motorman. — The man who operates a 
trolley car. 

Motor-Meter. — (1) An electric meter whose 
operations depend on the movements of 
an electric motor. (2) A meter con- 
nected with the supply circuit of an elec- 
tric motor. 

Motor Slip. — The deviation of an induc- 
tion motor from synchronous speed, or 
the proportional loss of synchronous speed 
due to load and losses of energy. 

Motor Standards. — The supports for the 
bearing of an electric motor. 

Motor Starter.— A term proposed for a 
motor starting-rheostat. 

Motor Starting-Box.— A box containing 
a starting rheostat or controller. 

Motor Starting-Rheostat.— An adjusta- 
ble rheostat provided for preventing an 
abnormal rush of current through a shunt- 
wound motor, on the starting of the same. 

Motor Suspension. — The suspension pro- 
vided for the electric motors on a street- 
car truck. 

Motor Switch.— A switch provided for 

the control of a motor. 
Motor Telegraph Printing System. 

A printing telegraph system in which 
two motors, one at the transmitting, and 
one at the receiving end of the line, are 
maintained in synchronous rotation. 

Motor Torque.— The rotary effort de- 
veloped by an electric motor. 

Motor-Transformer.— (1) A transformer 
or secondary generator operated by a 
motor. (2) A motor-generator, dynamo- 
tor, or rotary-transformer. (3) A dyn- 
amo-electric machine having two arma- 
ture windings, one to receive current as a 
motor, and the other to deliver current to 
a secondary circuit as a generator. 

Motor Truck.— The truck of an electric 
car provided with supports for the sus- 
pension of an electric motor or motors. 

Motoring at Brushes. — A term proposed 
for flashing at the brushes of a motor. 

Moulded Carbons. — Artificial carbons 
made by moulding mixtures of carbona- 
ceous substances under pressure. 

Moulded Filaments.— The formation of 
an incandescent filament by moulding a 
suitable carbonaceous paste by hydraulic 
pressure. 

Moulded Mica.— An insulating substance 
consisting of finely divided mica, made 
into a paste with some fused insulating 



material, and moulded into the desired 
shape before cooling. 
Moulding "Wiring. — Electric conductors 
or wires that are held in place on the 
walls or ceiling of a room by means of 
suitably-shaped mouldings. 

Mouldings, Electric. — Mouldings of 
dried non-conducting wood, provided 
with longitudinal grooves for the recep- 
tion and support of insulated wires. 

Mounted Filament. — The filament of an 
incandescent lamp placed on its support, 
ready for introduction into the lamp 
chamber. 

Mounting of Filament.— Providing the 
filament and leading-in wires of an incan- 
descent lamp with a suitable glass sup- 
port ready for introduction into the 
chamber of an incandescent lamp, and 
its hermetical sealing therein. 

Mouse-Mill Dynamo.— A form of dyna- 
mo-electric machine employed to drive a 
replenisher or influence machine. 

Mouse-Mill Machine. — A form of induc- 
tion machine employed as a replenisher 
or high-tension source. 

Mouth-Pieces. — Circular openings into 
air chambers, placed over the diaphragms 
of telephones, phonographs, gramophones, 
or graphophones, to permit the ready 
application of the mouth in speaking, 
so as to set the diaphragm in vibration. 

Movable.— Capable of being moved. 

Movable Secondary.— The secondary of 
an induction coil, which, instead of being 
fixed, as in most coils, is movable. 

Multi - Cellular Electrostatic Volt- 
meter. — An electrostatic voltmeter in 
which a series of fixed and movable plates 
are employed, instead of the single pair of 
plates of the quadrant electrometer. 

Multi-Circuit Arc-Dynamo.— A dynamo 
whose armature is provided with several 
circuits designed to avoid too high an 
electromotive force on any single circuit. 

Multi-Circuit Arc-Light Generator.— 
(1) An arc-light generator designed to 
supply, several series-connected arc-cir- 
cuits, as distinguished from a generator 
designed to supply a single circuit. (2) A 
multi-circuit arc dynamo. 

Multi-Coil Alternating- Current Ar- 
mature-Winding. — An alternator arma- 
ture-winding containing on its surface 
more than one coil or group of conduc- 
tors per pole of the field frame, as distin- 
guished from a uni-coil winding. 

Multi-Conductor Cable.— A cable pro- 
vided with a plurality of conducting 
circuits. 



Mul.] 



857 



[Mul. 



Mul ti- Duct Conduit.— A conduit con- 
taining a plurality of ducts. 

Multi-Periodic Current.— (1) A current 
composed of a number of associated com- 
ponent currents of different frequencies. 
(2) A complex-harmonic current. 

Multiphase. — Containing more than a 
single ^hase. 

Multiphase Alternating-Currents.— A 
number of separate alternating currents 
which differ in phase by a fixed amount. 

Multiphase Alternator.— An alternator 
capable of producing multiphase cur- 
rents. 

Multiphase Apparatus.— A general term 
for multiphase alternators, motors, or 
other receptive apparatus, suitable for 
use on multiphase circuits. 

Multiphase Circuits.— The circuits em- 
ployed in a system of multiphase distri- 
bution. 

Multiphase Dynamo. — A multiphase 
alternator. 

Multiphase Generator. — A multiphase 
alternator. 

Multiphase Induction-Motor. — An in- 
duction motor suitable for use in con- 
nection with multiphase currents, and 
operated by rotating magnetic fields. 

Multiphase Synchronous-Motor. — A 
synchronous alternating-current motor 
supplied with multiphase currents as dis- 
tinguished from an asynchronous or in- 
duction multiphase motor. 

Multiphase System. — A system for the 
distribution of energy by multiphase cur- 
rents. 

Multiphaser. — A multiphase alternator. 

Multiple-Arc Circuit.— A term often 
used for multiple circuit. 

Multiple- Arc-Connected Electro-Re- 
ceptive Devices.— Electro-receptive de- 
vices connected with the driving circuit 
in multiple arc. 

Multiple- Arc-Connected Sources. — A 
battery of multiple-connected sources. 

Multiple- Arc-Connected Translating 
Devices. — Multiple-arc connected elec- 
tro-receptive devices. 

Multiple- Arc Resistance Box.— A re- 
sistance box whose resistances are capable 
of being inter-connected in multiple arc. 

Multiple Armature-Windings. — (1 ) A 
term sometimes used for multiple-circuit 
armature- win dings. (2) A term some- 
times used for multiple- wound armature 
windings. 

Multiple Cable. — A cable containing 



more than a single conducting wire or 
circuit. 

Multiple Cable-Core. — A cable contain- 
ing more than a single conducting wire 
or core. 

Multiple Call-Box. — A call-box capable 
of automatically transmitting a number 
of different calls. 

Multiple Circuit. — A circuit in which a 
number of separate sources or separate 
receptive devices, or both, have all their 
positive poles connected to a single posi- 
tive lead or conductor, and all their neg- 
ative poles connected to a single negative 
lead or conductor. 

Multiple - Circuit Multiple - Wound 
Armature. — An armature providing a 
plurality of circuits between the brushes, 
and also a plurality of independent wind- 
ings connected to symmetrically inter- 
spersed independent commutator bars. 

Multiple Circuit Winding of Arma- 
ture. — Such a winding as provides a mult- 
iplicity of circuits in parallel through an 
armature. 

Multiple Conduit.— A conduit provided 
with a number of separate ducts. 

Multiple - Connected. — Connected in 
multiple-arc. 

Multiple-Connected Battery.— A bat- 
tery wmose separate cells are connected 
in multiple-arc. 

Multiple - Connected Electro - Recep- 
tive Devices. — Multiple-arc-connected 
translating devices. 

Multiple- Arc-Connected Sources. — A 
number of separate sources connected in 
multiple-arc, so as to act as a single 
source. 

Multiple Connection. — Connection in 
parallel or in multiple-arc. 

Multiple-Contact Carbon Telephone 
Transmitter. — (1) A telephone trans- 
mitter provided with a number of sep- 
arate contacts. (2) A dust telephone 
transmitter. 

Multiple Converter. — A multiple trans- 
former. 

Multiple Electric Gas-Lighting. — A 
system of electric gas-lighting in which 
a number of gas jets are ignited by high 
electromotive force discharges obtained 
from a Ruhmkorff coil or static induction 
machine. 

Multiple Electrode Telephone. — A 
telephone transmitter possessing a plural- 
ity of active contacts. 

Multiple Electrolysis.— Electrolysis pro- 



MuL] 



858 



[MuL 



ducing or accompanied by secondary 
chemical reactions. 
Multiple - Harmonic Telegraph. — A 
general term embracing the apparatus 
employed in multiple-harmonic teleg- 
raphy. 

Multiple - Harmonic Telegraphy.— A 

system for the simultaneous transmission 
of a number of separate and distinct mus- 
ical notes over a single wire, which 
separate notes are utilized for the simul- 
taneous transmission of an equal number 
of independent telegraphic messages. 

Multiple Jacks. — The reduplicating jacks 
of a multiple telephone switchboard. 

Multiple Lightning Flash. — Several 
lightning flashes apparently coming from 
the same cloud, 

Multiple-Pair Brush-Eoeker. —A term 
sometimes used for multiple-pair brush- 
yoke. 

Multiple-Pair Brush-Yoke.— A device 
for holding a number of pairs of brushes 
on the commutator, so that they can all be 
simultaneously moved or rotated thereon. 

Multiple-Parallel Circuit. — A term 
sometimes employed for a multiple of 
parallel circuits. 

Multiple Quadruplex. — A system of re- 
peating from more than one quadruplex 
circuit to a branch office, or repeating 
from one quadruplex circuit to another. 

Multiple Resonance.— The partial re- 
sonance of a primary conductor devoid of 
a definite period of oscillation, and, there- 
fore, capable of performing all possible 
oscillations lying within wide limits. 

Multiple Rheostat. — A form of rheostat 
whose resistances are capable of being 
thrown into a circuit in multiple, so that 
the carrying capacity increases as the re- 
sistance is decreased. 

Multiple Running.— The operation of 
generators in parallel. 

Multiple-Series. — A multiple connection 
of series groups. 

Multiple-Series Circuit. — A circuit in 
which a number of separate sources, or 
receptive devices, or both, are connected 
in a number of separate groups in series, 
and these separate groups subsequently 
connected in multiple. 

Multiple-Series Condenser.— (1) An ar- 
rangement of groups of condensers in 
series, which groups are connected in 
multiple. (2) A condenser divided into 
parts capable of being connected either 
in multiple, or in series, or in both. 
Multiple-Series-Connected Receptive 
or Translating Devices.— A number of 



receptive or translating devices connected 
in multiple-series. 

Multiple-Series-Connected Sources.— 

A number of separate electric sources so 
connected in multiple-series, as to be 
capable of acting as a single source. 

Multiple-Series Connection.— Connec- 
tion in multiple-series. 

Multiple Switch.— A switch provided 
with a number of separate contact plates 
for controlling a plurality of circuits. 

Multiple Switchboard.— A switchboard 
to which the numerous circuits employed 
in systems of telegraphy, telephony, an- 
nunciators, or electric light and power 
circuits, are connected. 

Multiple-Tablet Switchboard.— A 

switchboard provided with a number of 
separate tablets or panels. 

Multiple Telegraphic - Repeater.— A 
telegraphic repeater which repeats from 
one circuit to two or more Morse circuits. 

Multiple Telegraphy.— A system for the 
simultaneous telegraphic transmission 
over the same wire of more than a single 
message in the same direction. 

Multiple Telephone Receiver.— (1) A 
telephone receiver in a multiple tele- 
phone circuit. (2) A composite tele- 
phone receiver. 

Multiple Telephone Switchboard.— A 

switchboard consisting in reality of a 
number of separate switchboards, each 
provided with separate operators and 
bearing transmitter keys, switches and 
generators, employed when the number 
of subscribers connected with the switch- 
board exceed a number such as can be 
handled by a single switchboard. 

Multiple Telephony.— The simultaneous 
transmission over the same wire of a num- 
ber of separate telephonic despatches, in 
the same direction. 

Multiple Transformer.— (1) Any form of 
transformer the coils or circuits of which 
are connected in multiple. (2) The or- 
dinary alternating-current transformer 
connected across a supply circuit, as dis- 
tinguished from a series transformer. 

Multiple Transmission.— The simulta- 
neous sending of two or more messages 
over a single conductor in the same direc- 
tion. 

Multiple Unit System of Railway 
Traction. — A system of electric railways 
in which each traction unit is provided 
with its own independent motors, in such 
a manner that all the units may be oper- 
ated collectively from a single point. 



Mul.] 



859 



[Mus. 



Multiple Valued Function.— A func- 
tion which has more than one value for a 
single value of its variable. 

Multiple Wheel Printing Telegraph. 
A printing telegraph instrument pro- 
vided with a plurality of printing wheels. 

Multiple Windings.— Independent wind- 
ings symmetrically disposed upon the 
same armature, insulated from each other, 
but brought to different segments of the 
commutator. 

Multiple-Wound Multiple-Circuit 
Armature. — A multipolar armature 
having a plurality of windings, and each 
winding having a plurality of circuits 
between the brushes. 

Multiple-Wound Two- Circuit Arma- 
ture-Windings. — A multipolar arma- 
ture having a plurality of windings, each 
winding having two circuits between the 
brushes. 

Multiple Working of Dynamo-Elec- 
tric Machines. — A term sometimes used 
for parallel working of dynamo electric 
machines. 

Multiples. — The jacks in the various sec- 
tions of a multiple-telephone switchboard, 
which are connected to the same line or 
subscriber. 

Multiplex Telegraph. — A general term 
embracing the apparatus employed in 
multiplex telegraphy. 

Multiplex Telegraphy.— (1) A system of 
telegraphy for the simultaneous transmis- 
sion in opposite directions of more than 
two separate messages over a single wire 
from each end. (2) A term sometimes used 
for multiple telephony or simultaneous 
transmission of more than one message 
in the same direction over a single wire. 

Multiplex Telephony. — A system of tele- 
phony for the simultaneous transmission 
in opposite directions of more than two 
separate messages over a single wire from 
each end. 

Multiplex Working.— Multiplex trans- 
mission. 

Multiplicator. — A term sometimes used 
for multiplier. 

Multiply. — In a multiple telephone switch- 
board to reduplicate or to repeat at each 
section of the switchboard. 

Multiply Re-Entrant Armature-Wind- 
ing.— An armature-winding provided 
with a plurality of separate conducting 
paths or windings, each of which is in- 
dependently re-entrant. 

Multiplying Power of Shunt.— A quan- 
tity by which the current flowing through 



a galvanometer or other device provided 
with a shunt, must be multiplied, in order 
to give the total current. 
Multi-Point Secondary.— A secondary 
coil arranged so that it can be readily 
tapped at different points. 

Multipolar Armature.— An armature 
suitable for use in a multipolar field. 

Multipolar - Drum Armature - Wind- 
ings. — Windings of a drum armature 
suitable for a multipolar field ; i. e. pro- 
ducing more than two poles on the arma- 
ture surface. 

Multipolar Dynamo. — A dynamo pro- 
vided with a multipolar field. 

Multipolar Electric Bath.— An electro- 
therapeutic bath in which more than two 
electrodes are employed. 

Multipolar Field.— A field produced by 
more than two separate magnet poles. 

Multipolar Generator.— A multipolar 
dynamo. 

Multipolar Motor. — A motor whose field- 
magnets contain more than two separate 
magnet poles. 

Multipolar Railway - Generator.— A 
generator having a multipolar field, em- 
ployed for furnishing current to trolley 
cars. 

Multipolar-Ring Armature- Winding. 
The winding of a ring armature adapted 
to a multipolar field. 

Multipolar Winding. — A winding suit- 
able for use in multipolar generators or 
motors. 

Multi-Slot Armature - Winding. — A 

multi-coil armature winding. 

Multi-Slot Alternating-Current Iron- 
Clad- Armature. — An iron-clad arma- 
ture having more than one slot per field 
pole and furnishing alternating currents. 

Municipal Series Circuit. — A series cir- 
cuit employed for the distribution of in- 
candescent lights and suitable for lighting 
streets. 

Municipal System of Incandescent 
Electric Lighting. — A system for the 
distribution of incandescent electric 
lights, in which the separate lamps are 
connected to the circuit in series, each 
lamp being provided with a film or other 
automatic cut-out. 

Muscle Currents. — In electro-therapeu- 
tics the electric currents flowing through 
a muscle during its stimulation or ac- 
tivity. 

Muscular Pile. — Matteucci's muscular 
pile. 



Mus.] 



860 



[Nat. 



Mushroom Anchor.— An anchor resem- 
bling a mushroom in form and used for 
mooring buoys in submarine cable- work, 
so as to resist dragging along the sea-bot- 
tom and yet avoid becoming tightly en- 
gaged in rocks. 

Mushroom Deposit on Negative Car- 
toon. — A flat deposit of graphitic carbon 
of a mushroom shape, that forms on the 
negative carbon of an enclosed arc-lamp. 

Musket, Electric. — A gun whose charge 
is ignited by a platinum wire rendered 
incandescent by the action of a battery 
placed in the stock of the gun. 

Mutual Flux of Transformer.— The 
magnetic flux which passes through both 
coils in a transformer as distinguished 
from magnetic flux which may traverse 
one coil, when excited to the exclusion of 
the other. 



Mutual Inductance.— (1) The coefficient 
of mutual induction between two con- 
ductors. (2) The flux linkages in one 
circuit due to unit current in the other. 

Mutual Induction.— (1) Induction pro- 
duced on each other by two neighboring 
circuits through the mutual inter-con- 
nection of their magnetic fluxes. (2) In- 
duction produced in neighboring 
charged conductors by the inter-connec- 
tion of their electrostatic fluxes. 

Myograph. — An instrument for measur- 
ing nervous sensibility. 

Myopia. — Near-sightedness. 

Myopic. — Of or pertaining to near-sighted- 
ness. 

Myria. — A prefix for ten thousand times. 



N 



N. — A symbol for the whole number of lines 
of magnetic flux or induction in any mag- 
netic circuit. 

N. — In submarine telegraphy, a code signal 
at the end of a message to indicate that 
there are no more messages to follow. 

N. — A contraction for north-seeking mag- 
netic pole. 

n. — (1) A symbol employed for frequency. 
(2) A contraction for a number. 

N. H. P. — A contraction for nominal horse- 
power. 

Name Plate. — A plate fastened to a 
dynamo-electric machine and bearing the 
name of the maker and other particulars 
such as the speed, power, weight, pres- 
sure, and current of the machine. 

Narrow-G-auge Street-Railway Mo- 
tor. — A street-railway car motor of less 
breadth than usual, suitable for use on 
narrow-gauge tracks. 

Nasal Electrode.— An electrode suitable 
for introduction into the nostril for its 
therapeutic treatment. 

Nascent State. — A term used in chemistry 
to express the state or condition of an 
elementary atom or radical when just 
liberated from chemical combination, 
when it possesses chemical affinities or 
attractions more energetic than after- 
wards. 

Natural Current from Fault in Cable. 
The feeble current originating from the 
voltaic couple formed at a break or fault 
in a cable. 



Natural Currents.— A term sometimes 

applied to earth currents. 
Natural-Draught Transformer.— (1) An 

alternating-current transformer in which 
an air-space is left between the primary 
and secondary coils, through which a con- 
vection current of air passes on the heat- 
ing of the coils. (2) A transformer cooled 
by radiation and convection, as distin- 
guished from an air-transformer. 

Natural Electret.— A body whose mole- 
cules are inherently electrized, as distin- 
guished from a body whose molecules be- 
come electrized by induction. 

Natural Law. — (1) A law of nature. 
(2) An observed co-relation of phenomena 
such that when one phenomenon or group 
of phenomena occurs in a certain definite 
way, another phenomenon or group of 
phenomena invariably follows. 

Natural Magnet. — The name sometimes 
given to a lodestone. 

Natural Period.— (1) The time in which 
a cyclic phenomenon naturally completes 
itself. (2) The time of complete free os- 
cillation of a vibrating substance or con- 
dition, when not subjected to external 
restraint. 

Natural Resultant Fault.— In any cir- 
cuit, a fault which is the electrical equiv- 
alent in position and magnitude of all the 
actual small faults or leakages which may 
be present in that circuit. 

Natural Unit of Electricity.— (1) A 
term sometimes used in place of an atomic 



Nat.] 



861 



[Neg. 



charge of electricity. (2) The quantity of 
electricity carried by a single monad atom 
of any elementary substance. 

Natural Unit of Quantity of Electric- 
ity. — The quantity of electricity pos- 
sessed as a charge by any elementary 
monad atom. 

Naut. — A nautical mile. 

Nautical Mile. — (1) A knot or naut, or a 
distance of 6,087 feet ; or nearly 1.15 stat- 
ute miles. (2) The ^leT^h of the earth's 
equatorial circumference, or J^tti of a de- 
gree of longitude at the equator. 

Nautical Telegraphy. — Telegraphy con- 
ducted at sea or over the sea, either be- 
tween different vessels or on board a 
single vessel, 

Near-Sightedness.— (1) Inability to see 
objects distinctly unless they are com- 
paratively near the eye. (2) Myopia. 

Nebula. — A misty appearance in the 
heavens often resolved by a telescope in- 
to clusters of innumerable stars. 

Needle. — A word frequently used for a 
magnetic needle. 

Needle Annunciator.— An annunciator 
whose indications are obtained by the 
movements of a needle, instead of by the 
fall of a drop, 

Needle Electrode. — A needle-shaped 
therapeutic-electrode employed for elec- 
trolytic treatment. 

Needle Instrument.— A single-needle 
instrument. 

Needle of Oscillation.— A small mag- 
netic needle employed for measuring the 
intensity of a magnetic field by the num- 
ber of oscillations it makes in a given 
time when disturbed from its position of 
rest in such field. 

Needle System of Telegraphy.— A sys- 
tem of telegraphy in which the letters of 
the alphabet and numerals are indicated 
by the to-and-fro movements of a mag- 
netic needle. 

Needle Telegraph. — A general term em- 
bracing the apparatus employed in needle 
telegraphy. 

Needle Telegraphy. — The needle system 
of telegraphy. 

Negative Brush of Dynamo. — The brush 
connected with the negative terminal of 
a dynamo. 

Negative Brush of Motor.— The brush 
connected with the negative terminal of 
the driving source. 

Negative Bus-Bars. — The negative om- 
nibus bars. 



Negative Charge.— (1) According to the 
double-fluid hypothesis, a charge of nega- 
tive electricity. (2) According to the 
single-fluid hypothesis, any deficit of an 
assumed electric fluid. (3) An electric 
charge of the same character as that pro- 
duced on silk when rubbed by glass. 

Negative Conductor.— The conductor 
connected to the negative terminal of an 
electric source. 

Negative Currents.— In telegraphy, a 
term applied to the currents sent over a 
line from the negative pole of the battery. 

Negative Direction of Electrical Con- 
vection of Heat. — A direction in which 
heat is transmitted by electric convection, 
through an unequally heated conductor 
opposite to that of an electric current. 

Negative Direction of Simple-Har- 
monic Motion. — Simple-harmonic mo- 
tion in which the generating circle is 
moved over in the negative direction. 

Negative Electricity.— (1) One of the 
phases of electric excitement. (2) The 
kind of electric charge produced on resin 
when rubbed with cotton. 

Negative Electromotive Force.— Such 
an E. M. F. as is produced at the free pole 
of a battery or other source whose posi- 
tive pole is grounded. 

Negative Electrification. — (1) The 
charging of a body with negative electric- 
ity. (2) A negative charge. 

Negative Electrode. — The electrode con- 
nected with the negative terminal of a 
source. 

Negative Element of Electrolyte.— 

(1) The element which in electrolysis ap- 
pears at the positive electrode. (2) The 
cathion. 

Negative Element of Voltaic Cell.— 

(1) That element of a voltaic couple 
which is not acted on by the electrolyte. 

(2) The element which forms the positive 
pole of the cell above the surface of the 
electrolyte. 

Negative Feeders. — The feeders con- 
necting the negative mains with the 
negative poles of the generators. 

Negative Fluid. — (1) A specific fluid 
which was formerly believed by the ad- 
vocates of the double-fluid electric 
hypothesis to be the cause of negative 
excitement. (2) A deficit of an assumed 
single electric fluid. 

Negative Inductance. — A capacitance. 

Negative Lightning. — A name given to 
a variety of lightning discharge whose 
existence is apparent in some photo- 



ffeg.] 



862 



[Neu, 



graphic negatives of lightning flashes, 
as black branches coming out from the 
main-lightning stem. 

Negative Omnibus-Bar.— The bus-bar 
connected to the negative terminals of 
the generators. 

Negative Phase of Electro tonus.— A 
decrease in the electromotive force of a 
nerve, produced by sending an electric 
current through the nerve in the opposite 
direction to the nerve current. 

Negative Plate of Storage Cell.— (1) 
That plate of a storage cell which is con- 
verted into or partly covered with a coat- 
ing of spongy lead by the action of the 
current. (2) That plate of a storage cell 
which is connected with the negative 
terminal of the charging source, and 
which is, therefore, the negative pole of 
the cell on discharging. 

Negative Plate of Voltaic Cell.— (1) 
The electro-negative element of a voltaic 
couple. (2) That element of a voltaic 
couple which is negative in the electro- 
lyte of the cell. (3) That portion of the 
plate of a voltaic cell above the liquid, 
which becomes the positive pole of the 
cell. 

Negative Pole of Receptive Device.— 
That pole of a receptive device which is 
connected to the negative pole of a 
source. 

Negative Pole of Source.— That pole of 
an electric source through which the 
current is assumed to enter, or flow back 
into the source, after having passed 
through the circuit connected to the 
source. 

Negative Potential. — (1) A potential such 
as determines a tendency of electricity to 
flow towards it from the earth or from 
any point of positive potential. (2) Gen- 
erally, the lower potential or lower level. 
(3) That property of a point in space by 
virtue of which electric work is done by 
the movement of a small positive charge 
to that point from an infinite distance. 

Negative Rays.— The molecular streams 
given off at the negative electrode or 
cathode of an induction tube, on the pas- 
sage of electric discharges through the 
tube. 

Negative Resistance.— A property of a 
circuit or conductor containing an E. M. 
F. , whereby a current flowing through the 
conductor rises in pressure instead of 
falling. 

Negative Rotation. — Right-handed or 
clockwise rotation, as viewed from in 
ront of the clock. 



Negative Side of Circuit.— (1) The side 
of a circuit opposite to the positive sides. 
(2) That side of a circuit bent in the form 
of a circle, from which, if an observer 
stood with his head in the negative region, 
he would see the current pass around him 
clockwise, or right-handedly. (3) The 
side of a circuit connected with the 
negative pole of the source. 

Negative Spark.— The spark produced 
by the discharge of a negatively charged 
conductor. 

Negative Terminal.— (1) The terminal 
of a voltaic cell connected with the posi- 
tive plate or element. (2) The terminal 
of a source connected with the negative 
pole. (3) The terminal of a translating 
device connected with the negative pole 
of the source. 

Negative Wire.— (1) A wire charged, or 
intended to be charged, negatively. (2) 
A wire connected with the negative pole 
of a source. (3) A wire of negative 
potential. 

Negatively Excited.— Endowed with a 
negative charge. 

Net Efficiency .—The final or ultimate 
efficiency of a series of machines or 
translating devices, through which en- 
ergy, or any other quantity, has to suc- 
cessively pass, as distinguished from the 
separate efficiency of each machine or 
device. 

Netted Globe. — A globe surrounding an 
arc-lamp and provided with an external 
netting. 

Netting Wire. — A wire net- work-shield 
inclosing the globe of an arc-lamp, both 
to protect it from mechanical injury and 
to prevent glass from falling in case of 
fracture. 

Network of Conductors.— A term ap- 
plied to a number of interconnected con- 
ductors which may resemble a net in ap- 
pearance. 

Network of Currents. — A term some- 
times applied to a number of shunts or 
derived circuits, or to the currents which 
flow in a network of conductors. 

Neutral Armature. — A non-polarized 
armature. 

Neutral Ampere-Meter.— An ampere- 
meter connected with the neutral bus-bar 
in a three-wire system of distribution. 

Neutral Conductor.— The neutral wire 
in a three-wire system. 

Neutral Feeder. — In a three- wire system, 
a feeder connected with the neutral bus- 
bar. 



Neu.] 



863 



[Nip. 



Neutral-Line of Magnet.— The equator 
of a magnet. 

Neutral-Line of Commutator Cylin- 
der. — A line on the commutator cylin- 
der of a dynamo connecting the neutral 
points or points of zero potential. 

Neutral-Line of Dynamo Armature.— 

(1) A line passing through the armature, 
s^ymmetrieally disposed as regards its 
entering and emerging flux. (2) A line of 
zero polarity. 

Neutral Omnibus-Bar, or Bus-Bar. — 
In a three-wire system of distribution, 
the bus-bar connected with the neutral 
dynamo terminals, or the terminals unit- 
ing the positive and negative dynamos. 

Neutral Point. — A term sometimes em- 
ployed in electro-therapeutics for indiffer- 
ent point. 

Neutral Points of Magnet.— (1) Points 
approximately midway between the poles 
of a magnet. (2) Points of zero polarity. 

Neutral Points of Dynamo-Electric 
Machine. — (1) Two points situated on 
the commutator cylinder at opposite ends 
of its diameter at which the collecting 
brushes must rest in order to obtain 
sparkless commutation. (2) Points of zero 
potential on a commutator. 

Neutral Points of Thermo-Eleetrie 
Diagram. — (1) The points on a thermo- 
electric diagram where the lines repre- 
senting the thermo-electric powers of any 
two metals cross each other. (2) A mean 
temperature for any two metals in a 
thermo-electric series, at which, if their 
two junctions are slightly over or slightly 
under the mean temperature, the one 
as much above as the other is below, no 
effective electromotive force is developed. 

Neutral Relay-Armature.— (1) A relay 
armature consisting of a piece of soft iron 
which closes a local circuit whenever its 
electro-magnet receives an impulse over 
the main line. (2) A normally unmag- 
netized relay armature. 

Neutral Section of Magnet. — A section 
passing through the neutral line or equa- 
tor of a magnet. 

Neutral Salt. — A salt possessing neither 
acid nor basic properties. 

Neutral Solution.— A solution of neutral 
salt. 

Neutral Wire. — (1) In a three-wire system 
of electric distribution the wire con- 
nected to the neutral dynamo-terminal. 

(2) The balance wire of a three- wire 
system. 

Neutral- Wire Ampere-Meter.— An am- 



pere meter placed in the circuit of a 
neutral wire, in a three-wire system, for 
the purpose of showing the excess of cur- 
rent passing over one side of the system 
as compared with the other side, when a 
balance between the two is no longer 
maintained. 
Neutral Zone of Charged Insulated 
Conductor.— That portion of an insu- 
lated conductor, charged by electrostatic 
induction, which lies approximately mid- 
way between its positive and negative 
end. 

Neutral Zone of Magnet.— A term some- 
times employed for equator of magnet. 

Neutralization.— The act or quality of 
rendering neutral, as in the discharge of 
an electrified body. 

New Ohm. — A term sometimes used for 
the international ohm. 

Nib on Carbon Electrode.— A term 
sometimes employed for the graphitic 
deposit on one side of the negative carbon, 
when the arc has been maintained be- 
tween the sides of two parallel carbon 
electrodes. 

Nickel Bath.— An electrolytic bath con- 
taining a readily electrolyzable salt of 
nickel, a plate of nickel acting as the 
anode of the battery, and placed in a 
liquid near the object to be coated, which 
forms the cathode. 

Nickel Facing of Electro-Type. — A 
thin electro-plating of nickel deposited on 
the surface of an electro-type for the pur- 
pose of hardening it. 

Nickel Plating.— Electro-plating with 
nickel. 

Niello- Work. — An enamelling process in 
which a pattern is traced upon a bright 
silver surface with a silver sulphide, or 
with mixtures of lead, copper and silver 
sulphide, artificially prepared, and which 
is afterwards fixed, by heating to the 
fusion point. 

Nigger. — A term sometimes employed for 
a fault in any electric apparatus or sys- 
tem. 

Night-Bell.— In a hotel or telephone ex- 
change, a bell switched into connection 
with a shunted circuit of an annunciator 
case, and intended, by its constant ring- 
ing, to call the attention of the night 
operator to the falling of a drop. 

Night-Switch for Telephone.— A switch 
so arranged that, when turned to the on- 
position, any or all of the drops will, on 
falling, ring a bell, and thus call the atten- 
tion of the operator. 

Nipple of Negative Carbon.— A tiny 



No.] 



864 



[Non 



projection of graphitic carbon, deposited 
during the maintenance of the arc, on 
the surface of the negative carbon oppo- 
site the crater of the positive carbon. 

No. 1 Side of Quadruplex System.— 
That side of the quadruplex system which 
is employed in operating the polar duplex 
system. 

No. 2 Side of Quadruplex System.— 
That side of a quadruplex system which 
contains the increment key and neutral 
relay. 

Nobili's Rings.— Metallo-chromes. 

Nodal Point.— A point in a vibrating 
string or wire free from vibration. 

Node. — A nodal point. 

Nodes, Electric— (1) Points in a circuit 
or conductor through which electric 
oscillations are passing, which possess 
a constant value of potential, while the 
potential at the internode alternates be- 
tween two fixed limits. (2) Points in a 
conductor where the strength of the in- 
duced oscillatory current is equal to zero. 

Nodular Electro - Metallurgical De- 
posit. — A coherent electro-metallurgical 
deposit, of irregular outline, which occurs 
whenever the current density falls below 
its normal value. 

Noise. — (1) Any discordant assemblage of 
musical tones. (2) Any sound of too short 
duration to permit its pitch to be readily 
distinguished. 

Noisy Arc. — A voltaic arc whose mainte- 
nance is attended by frying, hissing or 
spluttering sounds. 

Nominal Candle-Power.— A term some- 
times applied to the candle-power of a 
luminous source taken in a favorable 
direction. 

Non-Arcing Arrester.— A non-arcing 
lightning arrester. 

Non-Arcing Fuse. — A fuse wire formed 
of non-arcing metal, which, therefore, 
blows without the formation of a voltaic 
arc. 

Non-Arcing Metal. — An alloy formed of 
mixtures of a certain , group of metals, 
which, under certain conditions, will not 
permit the maintenance of an alternating- 
current arc between them. 

Non- Arcing-Metal Lightning- Arrest- 
er. — A lightning arrester employing 
electrodes of non-arcing metals. 

Non-Arcing Metals. — Metals forming 
non-conducting oxides such that an 
alternating-current arc is interrupted 
between them under certain conditions. 



Non-Automatic Repeater.— A manual 
repeater. 

Non-Automatic Variable Resistance. 
A resistance, the value of which is regu- 
lated by hand. 

Non-Conductor. — Any substance whose 
conductivity is low, or whose electric re- 
sistance is great. 

Non-Coperiodic. — (1) Non-synchronous. 
(2) Devoid of coperiodicity. (3) Not 
isochronous. (4) Having a period differ- 
ing from the period considered. 

Non-Coperiodic Electromotive Forces, 
Currents and Fluxes. — Electromotive 
forces, currents, or fluxes that are of dif- 
ferent periods or frequencies. 

Non-Electrics. — A term formerly applied 
to substances like the metals or other 
good conductors, which appeared not to 
be capable of electrification by friction. 

Non-Ferric— Devoid of iron. 

Non-Ferric Inductance. — (1) The in- 
ductance possessed by a circuit which 
does not contain, or is not magnetically 
associated with, iron. (2) The inductance 
of a coil with a non-magnetic core. 

Non-Ferric Inductance-Coil.— An in- 
ductance coil devoid of iron. 

Non-Ferric Magnetic Circuit.— (1) A 
magnetic circuit devoid of iron. (2) A mag- 
netic circuit containing only air, wood, 
copper or other non-magnetic materials. 

Non-Homogeneous Current-Distribu- 
tion. — (1) A distribution of current pass- 
ing through a conductor, in which there 
is an unequal density of current over any 
cross section of the conductor. (2) The 
skin effect. 

Non-Illumined Electrode.— That elec- 
trode of a selenium cell which is pro- 
tected from the direct action of light. 

Non-inductive Load.— (1) An induction- 
less load. (2) A load consisting of .re- 
sistance. 

Non-Interfering Fire Telegraph.— A 
system of fire-alarm telegraphy in -which 
two calls, simultaneously delivered, are 
incapable of interfering with each other. 

Non-Interfering Street Signal Box.— 
A street signal box connected with a cen- 
tral station for the delivery of an alarm, 
in such a manner that two signals given 
at the same time from two different boxes 
will not interfere with each other. 

Non-inductive Resistance.— A resist- 
ance devoid of self-induction. 

Non-Isotropic Expansion.— A property 
possessed by some crystalline substance of 
unequal expansion along different axes. 



Non.] 



865 



[Nos, 



Non-Luminous Radiation. — Radiation 
incapable of affecting the eye. 

Non-Luminous Heat Radiation.— (1) 
Heat radiation devoid of frequencies ca- 
pable of exciting or producing the sensa- 
tion of light. (2) Heat radiation devoid 
of luminous frequencies. 

Non-Magnetic Steel. — Certain alloys of 
iron, such as manganese steel, or nickel 
steel, that are practically devoid of the 
ability of being magnetized. 

Non-Multiple Telephone Switch- 
board. — (1) A telephone switchboard 
which is either not so large as to have 
rendered reduplication necessary, or 
which operates upon a system in which 
reduplication is dispensed with. (2) A 
single telephone-switchboard. 

Non-Oscillatory. — (1) Not characterized 
by oscillations. (2) Maintaining the same 
direction of motion throughout. 

Non-Oscillatory Charge.— A charge ob- 
tained by means of non-oscillatory electro- 
motive forces or currents, 

Non-Oscillatory Charging.— Charging 
uniformly by currents which are always 
of the same direction, as opposed to charg- 
ing with oscillations in which the currents 
alternate. 

Non-Oscillatory Current.— (1) A cur- 
rent that is devoid of periodic oscillation. 
(2) A uniform current. 

Non-Oscillatory Discharge.— A steady 
discharge, or one characterized by free- 
dom from periodic oscillation. 

Non-Oscillatory Intermittent - Cur- 
rent. — A current which is intermittent, 
but always in the same direction, as dis- 
tinguished from an oscillatory current 
whose direction alternates. 

Non-Overlapping Winding of Alter- 
nator. — A winding in which the coils 
are mechanically separate and do not 
overlap. 

Non-Periodic Alternating-Current.— 
An alternating current whose intensity 
varies non-periodically. 

Non-Periodically Varying - Current. 
A continuous current whose strength is 
subject to non-periodical oscillations. 

Non-Polar Transformer.— A term some- 
times used for a closed iron-circuit trans- 
former. 

Non-Polarizable.— Incapable of polariza- 
tion. 

Non-Polarizable Electrodes.— Electro- 
therapeutic electrodes constructed so as 
to avoid the effects of polarization. 

Non-Polarized Armature.— An arma- 
55 



ture of soft iron which is attracted to- 
wards the poles of an electro-magnet on 
the completion of the circuit, no matter 
in what direction the current passes 
through the coils. 

Non-Reactive Circuit. — A circuit which 
possesses neither inductance nor capacity, 
and, therefore, has ohmic resistance only. 

Non-Sinusoidal Currents.— Alternating 
currents that are not of the true sinusoi- 
dal type. 

Non-Synchronous Motor.— (1) An asyn- 
chronous motor. (2) An alternating-cur- 
rent motor capable of starting at any 
load. (3) An induction motor. (4) An 
alternating-current motor which is not 
compelled to run in synchronism with its 
driving current. 

Non-Uniform Magnetic Flux.— Mag- 
netic flux whose density varies in differ- 
ent portions of the magnetic circuit. 

Non-Vibrating Filament Lamp.— An 
incandescent lamp with an anchored fila- 
ment. 

Normal. — (1) Perpendicular to. (2) In 
accordance with rule. (3) Regular. 

Normal Current. — The current strength 
at which a system or apparatus is de- 
signed to be operated. 

Normal Earth-Current.— The usual earth 
current. 

Normal Magnetic-Day.— A day during 
which the values of the earth's magnetic 
elements do not vary greatly from their 
mean value. 

Normal Voltage. — The voltage at which 
a system or apparatus is designed to be 
operated. 

Normal Voltaic-Arc. — A voltaic arc 
whose characteristic properties are those 
possessed by the ordinary arc. 

North Magnetic Pole.— That pole of a 
magnetic needle which points approxi- 
mately to the earth's geographical north. 

North-Seeking Magnetic Pole.— (1) The 
north magnetic pole. (2) That pole of a 
magnet which turns towards and approx- 
imately points to the north geographical 
pole of the earth. 

Northern Lights. — (1) Luminous sheets, 
columns, arches or pillars of pale, flash- 
ing light, generally of a reddish color, 
seen in the northern heavens. (2) The 
aurora borealis. 

Nose Suspension of Motor.— The sus- 
pension of a motor in a car truck by a 
projecting hook or nose from above, as 
distinguished from a suspension by a bar 
and spring from beneath. 



Nul.] 



866 



[Ohm, 



Null or Zero Method.— (1) Any method 
employed in electrical measurements in 
which the values are determined by bal- 
ancing against them equal similar values, 
and ascertaining such equality not by the 
deflection of the needle, but by the ab- 
sence of such deflection. (2) Any method 
of measurement in which the criterion is 
no indication on the instrument em- 
ployed, as distinguished from a method 



depending upon the amounts or quantita- 
tive values of such indications. 
Null Point.— (1) Such a point on a micro- 
meter circuit that when joined or con- 
nected with the secondary circuit of an 
induction coil, the sparks in the micro- 
meter circuit are either very greatly de- 
creased, or are entirely absent. (2) A 
nodal point. 



o 



O. — An abbreviation for ohm, the practical 
unit of resistance. 

O. K. — A telegraphic signal of acquiescence 
meaning "all right," and said to be a 
perversion of the initial letters of the 
phrase " all correct." 

S2. — A contraction for megohm. 

o). — A contraction for ohm. 

o). — A symbol sometimes employed for an- 
gular velocity. 

O. cm. — An abbreviation proposed for 
ohm-centimetre, a standard of resistivity 
or conductivity. 

Oblique Induction.— In the air gap of a 
dynamo, magnetic induction which is 
deflected from the perpendicular to the 
polar surface by armature reaction. 

Obscure Heat. — Non-luminous heat. 

Observation Mine. — A variety of sub- 
marine mine that is fired from a distant 
point when an enemy's vessel is observed 
to be within its destructive area. 

Obtuse Angle. — Any angle whose value 
is greater than 90°. 

Occluded-G-as Process. — A process for 
the removal of the residual atmosphere 
from a vacuum tube, or from the cham- 
ber of an incandescent electric lamp, 
consisting in heating the same to a high 
temperature while connected with the 
pumps, before sealing off. 

Occlusion of G-as. — The absorption or 
condensation of a gas in the pores or on 
the surfaces of various, substances. 

Ocean Cable. — A submarine cable. 

Octo-Polar Dynamo.— A multi-polar dy- 
namo whose field has eight poles. 

Octo-Polar Field.— A field produced by 
the flux of eight separate magnet poles. 

Od. — The name given by Reichenbach to 
the assumed force which he claimed to 
be the cause of animal magnetism. 

Odd Harmonics.— In a complex harmon- 
ically varying quantity, the harmonics 



whose frequencies are odd multiples of 
the fundamental frequency. 

Odorscope. — An apparatus in which the 
determination of an odor was attempted 
, by the measurement of the effect its vapor 
or effluvia produced on a contact resist- 
ance. 

Odylic. — Of or pertaining to the od force. 

Odylic Rays. — Rays accompanying the 
od force, which, according to Reichen- 
bach, were emitted from magnet poles, 
and various other bodies, and were capa- 
ble of producing faint luminous sensa- 
tions in people sufficiently sensitive to 
their influence. 

Oersted. — (1) The name proposed for the 
C. G. S. unit of magnetic reluctance. 
(2) The reluctance offered to the passage 
of magnetic flux by a cubic centimetre of 
air when measured between parallel faces. 

Off Position of S witch.— (1) That posi- 
tion of a switch in which it throws a 
device or a portion of a circuit off from 
the working circuit. (2) The break posi- 
tion of a switch. 

Office Cable. —(1) A cable of insulated 
wires suitable for indoor office- work. 
(2) A cable leading to a telegraph office. 

Office Loop. — (1) In telegraphy, a loop, or 
two wires running to an office. (2) In 
telegraphy, a loop or pair of wires running 
from a circuit in an office to some desk in 
the same office, as distinguished from a 
loop running to some distant point. 

Offset. — A side connection, or lateral, taken 
from a conduit or cable for connection to 
a service. 

Ohm. — (1) The practical unit of electric 
resistance. (2) Such a resistance as would 
limit the flow of electrichty under an 
electromotive force of one volt, to a cur- 
rent of one ampere, or one-coulomb-per- 
second. (3) A value equal to 10 9 or 
1,000,000,000 absolute electro-magnetic 
units. (4) A value which is represented 



Ohm.] 



867 



[Ope. 



conventionally in C. G. S. units by a veloc- 
ity of 10 9 or 1,000,000,000 centimetres per 
second. 

Ohmage. — The value of an electric resist- 
ance expressed in ohms. 

Ohmie. — (1) Of or pertaining to the ohm. 
(2) Having the nature of an electric re- 
sistance. 

Ohmic Drop. — The drop in pressure due 
the ohmic resistance. 

Ohmic Resistance. — (1) The true resist- 
ance of a conductor due to its dimensions 
and conductivity, as distinguished from 
the spurious resistance produced by 
counter-electromotive force. (2) A re- 
sistance such as would be measurable in 
ohms bj r the usual methods of continuous- 
current measurement. 

Ohm-Meter. — A commercial galvanome- 
ter employed for practically measuring, 
by the deflections of a magnetic needle, 
the resistance of any part of a circuit to 
which it is connected, and through which 
a current flows. 

Ohm Mile. — (1) A standard of conductivity 
of wires one mile in length and having a 
resistance of one ohm at a standard tem- 
perature. (2) The product of the weight 
of a mile of wire and its resistance in 
ohms at a given temperature. (3) Such 
a mass of a substance, at a standard tem- 
perature, as would enable a uniform wire 
of that substance, one mile in length, to 
offer a resistance of one ohm. 

Ohm's Law. — The strength of a continuous 
electric current in any circuit is directly 
proportional to the electromotive force 
acting on that circuit, and inversely pro- 
portional to the resistance of the circuit. 

Oil-Cooled Transformer. — A trans- 
former that is cooJed by means of oil. 

Oil Cup. — A cup filled with lubricating 
oil, so supported that its oil is slowly fed 
to a shaft and bearing, or in general, to 
the rubbing parts of a machine. 

Oil Guard.— (1) A guard of sheet metal sup- 
ported so as to catch any drops of oil that 
may be thrown upon its surface, and thus 
protect any person or apparatus. (2) A 
guard placed over a direct-driven dynamo, 
to prevent oil from being thrown on it 
by the revolving engine. 

Oil-Insulated. — Insulated by means of oil. 

Oil Insulator. — A fluid insulator con- 
taining oil. 

Oil Insulator for Storage Battery .—An 
oil insulator provided for the support of 
a storage battery. 

Oil Paper.— An insulating material con- 



sisting of paper that has been soaked in 
an insulating oil. 

Oil Transformer. — (1) A transformer im- 
mersed in oil in order to ensure and 
maintain high insulation. (2) An oil- 
insulated transformer. 

Okonite. — A variety of insulating material. 

Olivette Box. — A box containing an arc- 
lamp provided with an aperture closed by 
colored glass, and employed for the pur- 
pose of obtaining a uniform field of color 
over a large surface, such as a stage scene. 

Omnibus Bars.— (1) Heavy bars of cop- 
per connected directly to the poles of a 
dynamo in a central station, and, there- 
fore, receiving their entire current. 
(2) Main conductors common to two or 
more dynamos in an electrical generating 
plant. 

Omnibus Wires. — A word sometimes 
used for bus-bars. 

On Position of Switch.— (1) That posi- 
tion of a switch in which it throws a de- 
vice, or portion of a circuit, on to a work- 
ing circuit. (2) The make position of a 
switch. 

One-Coil Transformer.— A word some- 
times employed for auto-transformer. 

One-Fluid Voltaic Cell.— A name some- 
times given to a single-fluid voltaic cell. 

One-Layer Armature- Winding.— (1) An 
armature winding consisting of but a 
single layer of wire. (2) A winding 
which, although it may consist of several 
layers, would be possible of application 
in a single layer, as distinguished from a 
two-layer armature which must be laid 
in two layers. 

One-Metal Cell. — An identical electrode 
cell. (2) A cell in which both elements 
are composed of one metal. 

One-Way Door-Trigger. — A door-trigger 
which operates on the opening of the door 
only. 

Opacity. — Possessing the property of non- 
transparency to radiation. 

Open-Arc. — A non-enclosed voltaic arc. 

Open-Box Conduit. — A conduit consist- 
ing of an open box of wood placed in a 
trench and closed with a wooden cover, 
after the introduction of the cable. 

Open Car- Wheel. — A form of car-wheel 
in which the space between the flange 
and the axle is provided with symmetri- 
cal perforations. 

Open Circuit. — A broken circuit, or a cir- 
cuit whose conducting continuity is 
broken. 

Open-Circuit Battery. — A* voltaic bat- 



Ope.] 



868 



[Ope. 



tery which is normally on open circuit, 
and which is used continuously on closed 
circuit only for comparatively small por- 
tions of time. 

Open-Circuit Burglar-Alarm. — A bur- 
glar alarm whose battery is normally on 
open circuit, and is brought into action 
on the closing of such circuit as a door, 
window, or other point. 

Open-Circuit Current of Transformer. 
A term sometimes employed for the leak- 
age current of a transformer. 

Open-Circuit Electric Oscillations.— 
Electric oscillations produced in open cir- 
cuits by the presence of electric surgings 
in neighboring circuits. 

Open-Circuit Induction.— The induction 
produced in an open circuit by means of 
electric surgings in neighboring circuits. 

Open-Circuit of Triphase Connections. 

The star-connection of triphase circuits. 

Open-Circuit Single-Current Signal- 
ling. — A system of single-current signal- 
ling in which the sending batteries placed 
at each station are in circuit during sig- 
nalling only. 

Open-Circuit Thermostat.— A thermo- 
stat maintained normally on an open-cir- 
cuit. 

Open-Circuit Transformer.— (1) A trans- 
former whose magnetic circuit is partly 
completed through air. (2) An aero-fer- 
ric-circuit transformer. 

Open-Circuit Voltaic Cell.— A voltaic 
cell that cannot be kept on closed circuit 
with a comparatively small resistance, 
for any considerable time, without seri- 
ous polarization. 

Open-Circuit Voltmeter.— (1) A volt- 
meter in which the points of a circuit 
where the potential difference is to be 
measured, are connected with an open- 
circuit to give indications by means of 
the charges so produced. (2) An electro- 
meter-voltmeter. 

Open-Circuited.— Provided with an open 
or broken circuit. 

Open-Circuited Conductor.— (1) A con- 
ductor not forming a closed circuit. (2) 
A conductor not closed on itself, and 
whose metallic continuity, therefore, is 
not complete, but through which an 
oscillatory discharge is capable of passing. 

Open - Circuited Discharge. — A dis- 
charge taking place through a circuit 
whose metallic continuity is incomplete. 

Open-Circuited Oscillation.— An elec- 
tric oscillation or surging taking place in 
an open-circuited conductor. 



Open-Circuit Thermostat.— A thermo- 
stat maintained normally on an open-cir- 
cuit. 

Open - Circuited Transformer. — An 
aero-ferric-circuit transformer. 

Open-Coil Armature. — An armature, 
some of whose coils are on open-circuit 
during a portion of the rotation of the 
armature. 

Open-Coil Armature-Windings.— The 
windings of an open-coil dynamo arma- 
ture. . 

Open - Coil Disc Dynamo - Electric 
Machine. — (1) A disc- wound dynamo- 
electric machine whose armature coils are 
open-circuited during part of each revo- 
lution. (2) An open-coil dynamo-elec- 
tric machine, the armature of which is 
disc shaped. 

Open - Coil Drum Dynamo - Electric 
Machine. — An open-coil dynamo-electric 
machine, the armature of which is drum- 
wound. 

Open-Coil Dynamo.— A dynamo pro- 
vided with an open-coil armature. 

Open - Coil Ring Dynamo - Electric 
Machine. — An open-coil dynamo-electric 
machine, the armature of which is ring- 
wound. 

Open - Iron - Circuit Converter. — An 

open-iron-circuit transformer. 

Open-Iron-Circuit Transformer.— An 
aero-ferric transformer. 

Open-Iron-Magnetic Circuit.— An aero- 
ferric magnetic circuit. 

Open Magnetic Core.— Any iron core 
which forms a portion of an aero-ferric 
circuit. 

Open Trolley-Car. — A trolley-car open 
on the sides and ends. 

Open-Wire Symmetrical Twist. — A 
system of stringing aerial telephone wires, 
so as to avoid cross talk, in which all the 
wires on a pole are helically twisted right- 
handedly along the line, one step being 
taken at each successive pole. 

Open Wiring.— (1) Wiring that has been 
purposely left exposed to view. (2) Wir- 
ing supported on cleats or insulators as 
distinguished from channelled, panelled, 
or covered wiring. 

Open Work. — Open wiring. 

Opening a Circuit.— Breaking a circuit. 

Opening Shock.— The physiological shock 
produced on opening or breaking an elec- 
tric circuit containing self-induction. 

Operator's Head Telephone.— A head- 
gear telephone. 



Ope. 



869 



[Osc. 



Operator's Position. — The space or posi- 
tion allotted to each operator in front of 
a multiple telephone switchboard. 

Operator's Set. — A telephone set at a 
central station employed by the operator. 

Operator's Shelf. — A shelf at, on, or 
above a multiple telephone switchboard 
for supporting the apparatus used by the 
operators. 

Ophthalmoscope. — An apparatus for ex- 
amining the living retina. 

Ophthalmoscopic. — Of or pertaining to 
the ophthalmoscope. 

Opposed Electromotive Forces.— Elec- 
tromotive forces that are opposed either 
to each other or to some other already 
existing electro-motive force. 

Opposed Magnetomotive Forces. — 
Magnetomotive forces that are opposed 
either to each other, or to some other al- 
ready existing magnetomotive force. 

Optic Angle. — The angle contained be- 
tween the optical centres of both eyes at 
any point to which they maybe directed. 

Optic Axis. — (1) The right line passing 
through the eye, so that the eye is sym- 
metrical on all of its sides. (2) The axis 
of symmetry of a crystal. (3) The prin- 
cipal axis of the eye, or its axis of figure. 

Optic Nerve. — The nerve of vision. 

Optics. — That branch of physics which 
treats of the properties and phenomena of 
light. 

Optical Bench. — A graduated support em- 
ployed for varying the distance between 
fixed and movable optical appliances. 

Optical Efficiency of Light.— The ratio 
between the obscure and the luminous 
radiation. 

Optical Galvanometer. — A galvanometer 
whose indications are based on the mag- 
netic rotary power of liquids. 

Optical Strain. — A deformation produced 
in a plate of glass, or other transparent 
medium, by the action of a stress, attended 
by a change in some of the optical prop- 
erties of such medium. 

Optical Telegraph. — A name sometimes 
applied to a semaphore. 

Oral Annunciator. — An electric annun- 
ciator that is operated by a puff of breath 
transmitted through an ordinary speak- 
ing tube. 

Ordinary Jacks. — In a multiple tele- 
phone-switchboard, the reduplicated jacks 
of each subscriber appearing successively 
in each section, as distinguished from the 
local or answering jack, which appears 
at a single panel. 



Ordinary Lines. — The lines used for con- 
versation in a call-wire system of tel- 
ephony, as distinguished from the wires 
employed for calling. 

Ordinate. — In graphics, a distance taken 
on a line called the axis of ordinates 

Ordinary Relay. — A non-polarized relay. 

Organ, Electric. — A wind organ in which 
the escape of air into the different pipes 
is electrically controlled, or propelled. 

Orientation of Magnetic Needle.— The 
coming to rest of a magnetic needle in 
the direction of the earth's magnetic flux. 

Originating Call.— The call of the sub- 
scriber who asks to be connected with 
some other subscriber, as distinguished 
from any other call which may follow in 
the process of securing connection. 

Originating Operator. — In telephonic 
communication passing through more 
than one exchange, the operator who is 
nearest to the calling subscriber, and con- 
sequently the operator who first delivered 
the call, as distinguished from other oper- 
ators whose assistance may have been 
called in. 

Oscillating Current.— (1) An oscillatory 
current. (2) A periodically alternating 
current usually of diminishing ampli- 
tude. 

Oscillating-Current Transformer. — A 
transformer operated by an oscillating 
current. 

Oscillating Discharge. — An oscillatory 
discharge. 

Oscillating Needle. — A needle of oscilla- 
tion. 

Oscillation. — A to-and-f ro motion or vibra- 
tion. 

Oscillation of a Function.— The differ- 
ence between the greatest and the least 
values which a function assumes in a 
given interval. 

Oscillations, Electric. — (1) The series of 
partial intermittent discharges of which 
the apparent instantaneous disruptive dis- 
charge of a Leyden jar, through a small 
resistance, consists. (2) Free electric 
vibrations of a disturbed electric system . 
(3) Electric surgings. 

Oscillator. — Any device for producing 
oscillations. 

Oscillator, Electric— A device for pro- 
ducing electric currents of a constant 
period, independently of variations in its 
driving force. 

Oscillatory. — Vibratoiy, or characterized 
by periodic to-and-fro movements. 

Oscillatory Charging. — Charging by 



Osc] 



870 



[Out. 



means of an oscillatory electromotive 
force or current. 

Oscillatory Current.— A current which 
oscillates or performs periodic vibrations 
usually of diminishing amplitude. 

Oscillatory Discharge.— (1) An appar- 
ently instantaneous discharge of a Leyden 
jar or condenser, which in reality consists 
of a number of successive discharges. (2) 
A discharge which periodically decreases 
by a series of oscillations. 

Oscillatory Dynamo. — A dynamo whose 
armature coils have electromotive forces 
generated in them by a vibratory or oscil- 
latory motion through a magnetic field, 
instead of the usual rotary motion. 

Oscillatory Electric Displacement. — A 
displacement of an oscillatory character 
produced in a dielectric. 

Oscillatory Electric Inductance.— Os- 
cillatory inductance. 

Oscillatory Electromotive Force.— A 
rapidly periodic electromotive force, 
usually rapidly diminishing in amplitude. 

Oscillatory Generator.— An oscillatory 
dynamo. 

Oscillatory Inductance.— Inductance in 
the circuit of electric oscillations. 

Oscillatory Induction.— A name some- 
times applied to open-circuit induction. 

Oscillatory Intermittent Currents.— 
Intermittent currents which are oscillat- 
ory in character, such as the oscillatory 
discharges of a static machine. 

Oscillograph. — (1) An instrument for re- 
cording rapid variations of an electrical 
current or pressure, usually consisting of 
a combination of a suitable form of gal- 
vanometer with a photographic recording 
apparatus. (2) A cathode-ray tube in 
which the cathode rays are deflected by 
the application of a magnetic field. 

Osmometer. — An apparatus for measuring 
osmose. 

Osmose. — An unequal mixing of liquids of 
different densities through the pores of a 
separating medium. 

Osmose, Electric— The unequal differ- 
ence of diffusion between two liquids 
placed on opposite sides of a diaphragm, 
produced by the passage of an electric 
current through the diaphragm. 

Osmosis. — A term sometimes used for 
osmose. 

Osmotic. — Of or pertaining to osmose. 

Osmotic Pressure.— (1) The pressure pro- 
duced by osmose. (2) The virtual gas- 
eous pressure of a dissolved substance. 

Osmotic Pressure.— (1) Pressure produced 



by osmose. (2) Pressure in a solution 
due to the presence of a dissolved sub- 
stance. 

Osteotome, Electric. — An electrically 
propelled circular saw employed in the 
surgical cutting of bones. 

Outboard Bearing.— (1) A journal bearing 
projecting beyond the base frame of a 
machine for giving adequate support to a 
long or heavy shaft. (2) A separate 
journal bearing supported outside the 
frame of a machine. 

Outboard Bearing of Dynamo-Electric 
Machine. — (1) A bearing projecting be- 
yond the base frame of a dynamo-electric 
machine for the purpose of adequately 
supporting the rotor. (2) A bearing for 
the shaft of a dynamo rotor supported 
independently of the base of the dynamo. 

" Out-Current " of Telephone Belay. 
The current which is sent out by a tele- 
phone relay or repeater. 

"Out-Door" Transformer.— A trans- 
former placed outside a building on the 
sides of its walls, or on suitably selected 
posts. 

Outers. — (1) The outside conductors of a 
three-wire system as distinguished from 
the neutral conductor. (2) In telephony, 
the external pair of springs of a telephone 
jack. 

Outgoing Call. — A call issued from an ex- 
change, as distinguished from an incom- 
ing call. 

Outgoing-Call Trunk-Line.— A trunk 
line terminating at a central telephone 
station and conveying calls which are 
transmitted from the station, as distin- 
guished from an incoming call line on 
which such calls are received. 

Outgoing Current. — The current sent out 
over a line from a station as distinguished 
from the received current, or the return- 
ing current. 

Outgoing End. — The end of a junction 
telephone wire at which calls are trans- 
mitted. 

Outgoing Lines. — (1) Lines in a tele- 
phone exchange on which calls are for- 
warded or transmitted, as distinguished, 
from incoming lines. (2) Outgoing 
wires. 

Outgoing Side of Telephone Switch- 
board. — (1) The side of a switchboard at 
which the conductors leave it. (2) The 
side of a switchboard to which calls are 
transferred or from which calls are trans- 
mitted. 

Outgoing Signals.— Signals sent out over 



Out.] 



871 



[Ove. 



a telegraphic line by the outgoing cur- 
rents. 

Outgoing Wires. — Wires by means of 
which the current is led out from a gen- 
erator or station. 

Outlet. — (1) A place where branch wires 
come out in a wall or ceiling for connec- 
tion to a switch, lamp or other device. 
(2) In a system of incandescent-lamp dis- 
tribution, the places in a building where 
the fixtures or lamps are attached. 

Outlet Block. — (1) A fuse block placed at 
or near an outlet. (2) A block containing 
an outlet fuse wire. 

Outlet Box. — A box placed at or near an 
outlet for the ready making or changing 
of electric connections with the outlet 
conductors. 

Outlet Insulator. — Any insulator em- 
ployed at an outlet. 

Output. — The useful energy or activity 
given out by any machine. 

Output of Dynamo-Electric Machine. 
(1) The electric power of the current 
developed by a dynamo-electric generator 
or transformer, at its delivery terminals 
expressed in volt-amperes, watts, or kilo- 
watts. (2) The available mechanical 
power developed by a motor, or the power 
delivered at its pulley or shaft. 

Output Wires. — Wires connected with a 
distribution box which take their supply 
from the box. 

Outrigger. — An arm horizontally fastened 
to a pole for the purpose of trussing it. 

Outrigger for Arc-Lamp. — A device for 
suspending an electric arc-lamp so as to 
cause it to stand out from the wall of a 
building. 

Outrigger Torpedo.— A pole or spar tor- 
pedo. 

Outside Wiring. — (1) Any wiring for a 
circuit outside of a house or other build- 
ing. (2) Out-door wiring. 

Outside Work. — Out-of-door wiring. 

Over-Compounded. — Such a compound- 
ing of a dynamo-electric machine as pro- 
duces under an increase of load an increase 
of voltage at its terminals. 

Over-Compounded Dynamo.— A dy- 
namo in which the magneto-motive force 
of its series coils not only compensates 
for the drop in the armature, but also for 
the drop in a conductor leading from the 
generators to the motors or translating 
devices, thus permitting the external 
conductors to be regarded electrically as 
forming an extension of the armature 
winding, and thus permitting the genera- 



tor to deliver a constant pressure at its 
final terminals at the motor or device. 
Overflow of Ley den Jar.— A term 
sometimes employed for the discharge of 
a Leyden jar by a disruptive discharge 
around its edge. 

Overhead Conductor.— An aerial con- 
ductor. 

Overhead Feeders.— Aerial feeders, as 
distinguished from buried or under- 
ground feeders. 

Overhead Lines.— A term applied to 
aerial telegraph, telephone, electric light 
or power lines, that run overhead, in con- 
tradistinction to similar underground 
lines. 

Overhead Mains.— Any system of aerial 
mains. 

Overhead Switch.— (1) A switch con- 
trolling an overhead circuit. (2) A can- 
opy switch. (3) A switch placed over- 
head. (4) A switch placed above a motor- 
man on a car so as to be within his reach. 

Overhead Trolley-System.— (1) An aerial 
trolley wire system. (2) A system of 
electric-street-car propulsion in which the 
required current is taken from an over- 
head trolley-wire. 

Overhead Trolley- Wire. — An ordinary 
aerial trolley wire. 

Overhead Trolley. — A trolley employed 
in an overhead trolley-system. 

Overhead Wires. — Aerial wires. 

Overland Telegraph. — Any telegraphic 
circuit provided with aerial conductors, 
as distinguished from a submarine or an 
underground telegraph . 

Overlap Test. — A localization test for a 
single fault in a single telegraph line, by 
observing the resistance from each end 
and deducting therefrom half of the 
amount by which the sum of these resist- 
ances overlap the total conductor resist- 
ance of the line, to determine the posi- 
tion occupied by the fault. 

Overlap Splice. — A splice of a rope or 
cable in which the strands of one part 
overlap the parts of the other, as distin- 
guished from a splice in which the strands 
of both parts interlace. 

Overlapping Block System.— An elec- 
trically operated block system in which 
the signals automatically delivered by a 
train occupying one section, appear at a 
considerable distance behind the train on 
the preceding section. 

Overlapping Winding of Alternator 
Armature. — A winding in which the 
successive coils overlap, as distinguished 



Ove.] 



872 



[Pac, 



from a winding in which successive coils 
are mechanically separated. 

Overload. — (1) Any load whose value ex- 
ceeds that of the normal. (2) An exces- 
sive load. 

Overload of Electric Motor.— (1) A 
load greater than that which an electric 
motor can carry with its greatest effi- 
ciency of operation. (2) Any load which 
causes injurious heating of a motor. (3) 
Any load exceeding the full load for 
which a motor is designed. 

Overload Storage-Battery Switch.— 
A switch placed in a discharging circuit 
of a storage battery, arranged so as to 
automatically break the circuit of the 
battery should the discharge become ex- 
cessive. 

Overload Switch. — A switch designed to 
automatically open a circuit upon the 
occurrence of an overload. 

Over-Load Switch of Accumulator.— 
(1) A switch inserted in the circuit of a 
storage battery which automatically 
opens or introduces resistance into the 
circuit when the current becomes exces- 
sive. (2) An overload storage-battery 
switch. 

Overloaded Conductor.— A conductor 
carrying any electric current heavier 
than the normal current for which it was 
intended. 

Over-Maximal Contraction. — An in- 
crease in the electric stimulation of a 
motor nerve beyond the point where an 
apparent maximum stimulus has been 
reached. 

Ove r-R u n n i n g of Incandescent 
Lamps. — The operation of incandescent 
lamps at a pressure above the normal. 

Over-Running Trolley. — An overhead 
trolley, as distinguished from an under- 
ground trolley. 



" Overshoot."— To err in compensation 
by exceeding in adjustment, so as to over- 
pass the limit. 

Overtone Currents.— Electric currents 
of harmonic frequencies accompanying a 
fundamental periodic current. 

Overtones. — Additional faint tones of 
higher frequency than the fundamental, 
and some multiple thereof, associated 
with the fundamental and tending to give 
it its characteristic quality. 

Overtones, Electric— Electric upper har- 
monics or rates of alternation higher than 
the fundamental rate. 

Overtype Dynamo.— A dynamo-electric 
machine whose armature bore or cham- 
ber is placed above the field-magnet coils 
instead of below them. 

Overtype Magnet.— A form of horseshoe 
bi-polar electro-magnet, standing verti- 
cally over the armature between its poles. 

Over-Winding of Series Motor.— A 
series motor whose series-field winding is 
unduly strong. 

Over-Wound Motor Field.— (1) A motor 
field so wound that its full strength is 
nearly attained with considerably less 
than the normal current. (2) A term 
sometimes employed for an over-com- 
pounded motor field. 

Oyster Fitting. — A form of incandescent 
lamp-fitting employed on board a ship for 
water-tight bulkheads which cannot be 
pierced. 

Ozite. — A form of insulating material. 

Ozokerite. — A form of insulating material. 

Ozone. — An allotropic modification of oxy- 
gen which possesses more powerful oxy- 
dizing properties than ordinary oxygen, 
and formed by electric discharges in air. 

Ozonizer. — An apparatus for producing 
ozone by means of electric discharges. 



P. — A symbol for power. 

P. — A symbol for electric power. 

P. — A symbol proposed for pressure. 

#. — A symbol for quantity of magnetic flux. 

P. C. — A contraction for primary current. 

P. D. or p. d. — A contraction frequently 
employed for potential difference. 

P. P. D. — A contraction for primary po- 
tential difference. 

Pacinotti Projections.— Eadial projec- 



tions or teeth, in an armature core, so ex- 
tending from the central shaft as to form 
slots, pockets or armature chambers, for 
the reception of the armature coils. 

Pacinotti Ring. — A ring-shaped arma- 
ture-core provided with projections em- 
ployed by Pacinotti to receive the arma- 
ture windings in his generator. 

Pacinotti Teeth. — A term sometimes used 
for Pacinotti projections. 

Packing of Telephone Dust Transmit- 



Pag.] 



873 



[Par. 



ter. — The partial cohering of the parti- 
cles of granulated carbon in a dust trans- 
mitter into a solid cake, thus seriously in- 
juring the delicacy of the apparatus. 

Page Effect. — Faint sounds produced 
when a piece of iron is rapidly magnet- 
ized and demagnetized. 

Palladium. — A metal of the platinum 
group. 

Palladium Alloys. — Various alloys of 
palladium with other metals, some of 
which are entirely devoid of paramag- 
netic properties, and are, therefore, em- 
ployed for the hair-springs of watches, in 
order to render them free from the dis- 
turbing influence of strong magnetic 
fields. 

Palette Combination Wire-Gauge. — A 
wire-gauge measurer consisting of a 
graduated cam pivoted in a frame hook, 
so that the wire to be measured is gripped 
between the hook and cam. 

Pan-Cake Armature-Coil. — A flat arma- 
ture coil applied to and secured upon the 
surface of an armature. 

Panel Board. — A switchboard which is 
not prepared in one piece, but which is 
constructed and connected in panels. 

Panel Feeder. — The feeder connected 
with the bus-bars of any particular panel 
on a switchboard. 

Panel Fuse. — A fuse placed in the circuit 
of a particular panel on a switchboard. 

Panel of Switchboard.— One of the sep- 
arate vertical sub-sections of a composite- 
ly constructed switchboard. 

Panel Pressure.— The pressure which is 
maintained at a particular switchboard 
panel. 

Panel Reflector. — A reflector composed 
of strips or panels of silvered glass, or 
other good reflecting material. 

Panelled Conductors. — Conductors 
placed in mouldings. 

Panelled Wire. — Wire placed inside 
mouldings or panels. 

Pan-Telegraphy. — Fac-simile or auto- 
matic telegraphy. 

Pan-Telephone. — A name proposed for a 
certain sensitive form of telephone. 

Paper Cable. — (1) A paper-insulated cable. 
(2) A cable in which paper is the solid 
insulator employed. 

Paper Carbons. — Incandescent lamp fila- 
ments formed of carbonized paper. 

Paper Condenser. — A condenser in which 
sheets of paper covered by some good in- 
sulating material are employed as a 
dielectric. 



Paper Cut-Out. — A term sometimes used 
for film cut-out. 

Paper-Film Cut-Out.— A paper or film 
cut-out. 

Paper Insulation.— Insulation obtained 
by paper. 

Paper Perforator.— An apparatus em- 
ployed in automatic telegraphy for punch- 
ing in a strip of paper, the circular or 
elongated spaces that produce the dots 
and dashes of the Morse alphabet. 

Paper Telephone Cable.— A paper-insu- 
lated telephone cable. 

Parabolic. — Of or pertaining to a parabola. 

Parabola. — A conic section formed by the 
intersection of a right cone by a plane 
parallel to any side. 

Parabolic Reflector.— (1) A reflector or 
mirror the surface of which is a parabo- 
loid, or such as would be obtained by the 
revolution of a parabola around its axis. 
(2) A reflector employed in connection 
with electro-magnetic radiation of which 
the section perpendicular to the long axis 
has the form of a parabola, the focus of 
which is occupied by the electric oscil- 
lator. 

Paradox. — (1) Something which seems to 
contradict the ordinary laws of nature, 
but which is in reality the expression 
of such law. (2) A seeming inconsistency, 
or self-contradiction. 

Paraffine. — A solid hydro-carbon possess- 
ing high insulating powers. 

Paraffined Wire.— Wire wrapped or 
braided with some textile material and 
afterwards coated with paraffine. 

Paraffining. — Coating or covering with 
paraffine. 

Paragrele. — A French term for a light- 
ning rod, intended to protect a field 
against the destructive action of hail. 

Parallax. — The apparent displacement of 
the position of an object, relatively to 
points in front or behind it, due to a dif- 
ference in the point of view. 

Parallax Error. — An error in reading the 
position of a pointer on a scale due to par- 
allax. 

Parallel Arc-Circuit.— A word sometimes 
used for multiple circuit. 

Parallel Circuit. — A term sometimes used 
for multiple circuit. 

Parallel Conical Conductors.— A sys- 
tem of conical conductors, or of conduc- 
tors successively diminishing in diameter, 
employed in parallel distribution. 

Parallel Connected Sources.— A num- 
ber of separate sources connected in 



Par.] 



874 



[Par. 



parallel, so as to be capable of acting as a 
single source. 

Parallel-Connected Triphasers.— Two 

or more triphasers connected in parallel 
to a common set of triphase bus-bars or 
mains. 

Parallel-Connections of Alternators.— 
A number of alternators connected to 
a single pair of leads or bus-bars in paral- 
lel or multiple-arc. 

Parallel Coupling.— A term sometimes 
employed for the parallel connection of 
alternators. 

Parallel Distribution.— A distribution 
of electric energy in which the receptive 
devices are arranged between one or more 
pairs of parallel conductors, extending 
to the limits of the system. 

Parallel Feeding.— (1) Furnishing the 
current required for the operation of a 
number of receptive devices connected 
in parallel. (2) Multiple-arc distribution 
in which a pair of mains is supplied at 
one end as distinguished from an anti- 
parallel system. 

Parallel-Series. — A term sometimes ap- 
plied to a multiple-series connection. 

Parallel Transformer.— (1) A trans- 
former connected with a parallel-system 
of distribution. (2) A transformer that 
is connected to mains in parallel. (3) A 
transformer whose secondary coils are 
connected in parallel. 

Parallel Tree-Circuit.— A system of 
parallel distribution in which the dis- 
tributing mains diverge and ramify from 
a common centre or central station, di- 
minishing in size as they proceed. 

Parallel-Wire Stretcher.— A clamping 
tool for gripping and stretching wire. 

Parallel-Working of Dynamo-Electric 
Machines. — The working of two or more 
dynamos in parallel. 

Parallelogram of Forces.— A parallo- 
gram whose sides represent in length and 
direction the intensity and direction of two 
co-acting forces, and whose intermediate 
diagonal represents the resultant force. 

Paramagnet. — ( 1 ) A magnet produced by 
iron or other magnetic substance. (2) A 
ferromagnet. 

Paramagnetic— (1) Possessing the proper- 
ties ordinarily recognized as magnetic. 
(2) Possessing the power of concentrat- 
ing lines of magnetic force. (3) Ferro- 
magnetic. 

Paramagnetic Permeability. — Perme- 
ability to magnetic force. 

Paramagnetic Polarity.— Magnetic po- 



larity, or the polarity possessed by para- 
magnetic substances. 

Paramagnetically.— In a paramagnetic 
manner. 

Paramagnetism. — The magnetism of 
paramagnetic substances. 

Parasitical Currents.— A name some- 
times applied to eddy currents. 

Paratonnere.— A French term for light- 
ning rod, sometimes employed in English 
technical works. 

Parcel of Wire. — A word sometimes em- 
ployed for any quantity of manufactured 
wire presented at one time and in one 
piece for examination or testing. 

Parchmentized-Thread Filament.— A 
filament for an incandescent lamp made 
from the carbonization of parchmentized 
thread. 

Parchmentizing Process. — A process for 
converting cellulose thread into artificial 
parchment by treating it with dilute sul- 
phuric acid. 

Partial Contact.— (1) A high-resistance 
or imperfect contact between two tele- 
graphic lines or circuits. (2) An incom- 
plete contact. 

Partial Disconnection.— (1) A partial 
discontinuity. (2) A loss of complete 
metallic connection. (3) An imperfect 
metallic contact. 

Partial Earth.— The fault in a telegraphic 
or other line in which the line is in par- 
tial connection with the earth. 

Partial Fault.— In telegraphy or tele- 
phony, a fault due to an imperfect ground- 
contact, a cross-contact or a disconnec- 
tion, as distinguished from a complete 
fault or one that interrupts communica- 
tion. 

Partial Reaction of Degeneration. — 

That form of alteration to electric stim- 
ulation in which the nerves show no ab- 
normal reaction to electric stimulation, 
while the muscles, when directly stimu- 
lated by a constant current, exhibit the 
reaction of degeneration. 

Partial Vacuum. — An incomplete vac- 
uum. 

Partially Overlapping Winding of 
Alternator Armature. — A winding in 
which some of the coils overlap each 
other and some of the coils do not over- 
lap. 

Parting of Cable. — A complete rupture 
or breaking of a submarine cable. 

Party Lines for Telephone Service.— 
(1) Lines which connect several sub- 
scribers in one circuit, as opposed to lines 



Par.] 



875 



[Pen, 



devoted to a single subscriber. (2) Lines 
connecting permanently together several 
telephonic stations, as distinguished from 
lines connecting each telephone station 
through an exchange. 

Partz Gravity Cell. — A zinc-carbon 
couple employed with electrolytes of sul- 
phate of magnesia or common salt, and 
sulpho-chromic salt, in which the liquids 
are kept apart by their difference of 
density. 

Passive Resistance. — A term sometimes 
used for ohmic resistance. 

Passive State. — A condition of a metallic 
substance in which it may be placed in 
liquids that would ordinarily combine 
with it, without being attacked or cor- 
roded. 

Paste Joint for Lamp Filament.— A 
form of joint between the leading-in 
wires and the ends of the lamp filament 
obtained by the employment of a moist 
hydro-carbon paste which is subsequently 
carbonized. 

Pasted Secondary Cell.— A secondary 
cell in which the active material is applied 
to the surface of the grid or support in 
the form of a paint, paste, or cement. 

Path of Magnetic Leakage. — A side 
path taken by deviating magnetic flux, 
as distinguished from the main path of 
usefully employed flux. 

Patrol Alarm-Box. — In a system of sig- 
nal telegraphy or telephony, a box from 
which a call, communication, or alarm 
can be given by a patrol. 

Paying-Out. — The operation of passing 
submarine cable out of the ship while 
laying it. 

Paying-Out Drum. — A drum employed 
in laying a submarine cable and over 
which the cable takes several turns, 
whereby, by means of brakes, tension may 
be applied to the cable as it leaves. 

Paying-Out Leg. — In a bight of cable at 
the bows of a cable ship, that side or leg 
which is paid out, as distinguished from 
the side or leg which is held stationary or 
picked up. 

" Pea " Lamp. — A term sometimes given 
to a particular form of miniature incande- 
scent lamp. 

Peaked Type of Periodically-Alter- 
nating Electromotive Force. —A type 
of electromotive force whose curve of 
graphical representation has a peaked 
shape, as opposed to a smooth or a flat 
shape. 

Pear Push. — A pear-shaped push-contact, 



usually provided with a flexible cord 
pendant. 

Pedestal of Armature. — A supporting 

pillar for an armature bearing. 
Peg-Circuit.— A circuit that is opened 

or closed by means of metallic pegs. 
Peg-Switch.— (1) A switch that is opened 

or closed by means of a peg. (2) A pin 

switch. 

Peg-Switchboard.— A switchboard whose 
circuits are capable of being variously 
inter-connected by means of peg switches. 

Peltier Effect.— The heating effect pro- 
duced by the passage of an electric cur- 
rent across a thermo-electric junction, or 
surface of contact between two different 
metals, as distinguished from a Joulean 
effect or heat due to resistance merely. 

Peltier's Cross.— A cross, made by placing 
two plates of dissimilar metals in contact 
at right-angles to each other, employed 
for the study of the Peltier effect. 

Pen Carriage. — The carriage in an elec- 
tric chronograph which carries the pen 
and moves over the sheet of paper on 
which the record is made. 

Pen, Electric. — A device for manifold 
copying, in which a sheet of paper is made 
into a stencil by minute perforations ob- 
tained from a needle driven by a small 
electric motor, the stencil being after- 
wards employed in connection with an 
ink roller for the production of any re- 
quired number of copies. 

Pencil Microphone. — A carbon micro- 
phone in which the loose carbon is in the 
form of one or more pencils. 

Pendant Argand. — An Argand burner so 
arranged as to be lighted or extinguished 
by the pulling of a pendant. 

Pendant Cord. — A flexible conductor pro- 
vided for conveying the current to a 
pendant lamp or push. 

Pendant, Electric. — A hanging fixture 
provided witli a socket for the support 
either of an incandescent lamp, or of a 
contact. 

Pendant Electric-Lamp. — An incandes- 
cent lamp supported on a pendant cord. 

Pendant Pull-Switch. — A switch which 
is operated by pulling upon a pendant 
cord or loop. 

Pendant Socket. — An attachment pro- 
vided witli a chain or chains for turning 
on or off a lamp not readily accessible. 

Pendulum Annunciator.— (1) An an- 
nunciator whose indicating arm consists 
of a pendulous or swinging arm which, 
when at rest, assumes a vertical position, 



Pen.] 



576 



[Per, 



and which is moved to the right or left 
by the action of the current. (2) A 
swinging annunciator. 
Pendulum, Electric— (1) A pendulum 
so arranged that its to-and-fro motions 
send electric impulses over a line, either 
by making or breaking contacts. (2) An 
electric tuning fork whose to-and-fro 
movements are maintained by electric 
impulses. 

Pendulum Indicator. — A term sometimes 
employed for a pendulum annunciator. 

Pendulum Myograph. — An electric 
pendulum employed for physiological 
and chronographic purposes. 

Pendulum Selector. — In a system of se- 
lective telephony, a pendulum which is 
adjusted to vibrate at different rates and 
thereby actuate the call-bell of some par- 
ticular station selectively. 

Pendulum Signaller. — A pendulum 
armed with a contact maker for closing 
a circuit and transmitting signals. 

Pentad Atom. — An atom whose valency 
or atomicity is five. 

Pentane Standard. — A standard source 
of light obtained from the burning of 
pentane, and used in photometric meas- 
urements in place of a Methven screen. 

Penthode Working.— A five-way mode 
of telegraphic working obtained by the 
use of the Delany synchronous multi- 
plex telegraph. 

Penumbra. — A region of partial shadow 
surrounding the umbra or complete 
shadow, obtained when the source of 
light causing the shadow has an appreci- 
able area. 

Percentage Conductivity .—The conduc- 
tivity of a wire expressed in percentage 
of the conductivity of Mathiessen's 
standard. 

Percentage Conductivity of Wire.— 
(1) The conductivity of a wire in terms of 
the conductivity of pure copper. (2) The 
conductivity of a particular copper wire 
compared with the conductivity of a 
standard wire of the same dimensions. 
(3) The conductivity of a wire referred 
to Matthiessen's standard of conductivity 
for copper. 

Perfect Linkage. — Linkage of magnetic 
flux between two associated coils or cir- 
cuits unaccompanied by magnetic leak- 
age, or such that all of the flux is linked 
with all the turns of each circuit. 

Perforated Armature. — An armature 
provided with perforations for the in- 
sertion of the coils. 



Perforated Core-Discs. —The separate 
core discs of a laminated armature core 
provided with perforations for the in- 
sertion of armature wires. 

Perforator.— (1) A paper perforator. (2) In 
automatic telegraphy, an apparatus for 
perforating paper. 

Perforator Mallet.— A mallet used with 
a perforator for striking its keys. 

Perforator Slip.— The slip of paper pre- 
pared for use in a perforator. 

Period. — (1) The interval of time between 
two successive passages of a vibration 
through a given point of its path taken in 
the same direction. (2) The time occu- 
pied in performing a complete cycle. 

Period of Open-Circuit Oscillation. — 
The time in which the oscillation set up 
in an open circuit by electric resonance 
requires to make one complete to-and-fro 
motion. 

Period of Simple-Harmonic Motion. — 

The interval of time which elapses be- 
tween two successive passages of a moving 
particle over the same point in the same 
direction. 

Period of Vibration.— The time occupied 

in executing one complete vibration or 

motion to-and-fro. 
Periodic. — Of or pertaining to a period. 
Periodic Alternating Electromotive 

Force. — An electromotive force whose 

direction periodically varies. 

Periodic Current.— (1) A current whose 
strength and direction periodically vary. 
(2) A simple harmonic or sinusoidal cur- 
rent. (3) A periodically alternating cur- 
rent. 

Periodic Discharge.— (1) An electric dis- 
charge which periodically changes its 
direction. (2) An alternating discharge.- 

Periodic Governor.— A form of governor 
for an electric motor, in which the cur- 
rent is automatically cut off for a certain 
portion of each revolution. 

Periodic Motion. — A term sometimes em- 
ployed for simple-periodic motion. 

Periodically Alternating Discharge.— 
An alternating discharge. 

Periodically Decreasing Discharge. — 
An oscillatory discharge whose successive 
oscillations decrease in intensity. 

Periodicity.— (1) The number of periods 
executed per second by a periodically 
alternating quantity. (2) The number of 
cycles executed in unit time by an alter- 
nating current. (3) The frequency of an 
alternating current. 

Periodicity of Alternation. — (1) The 



Per.] 



877 



[Per 



number of alternations per second. (2) 
The frequency. (3) The number of alter- 
nations executed per second or per minute. 
Periodicity of Auroras, Magnetic 
Storms, and Sunspots.— Coincidences 
between the occurrence of auroras, mag- 
netic storms and sun-spots. 

Peripheral Speed. — The speed of a point 
on the circumference of a rotating cylin- 
der or wheel. 

Peripheral Velocity.— (1) The rate of 
linear peripheral speed. (2) The tan- 
gential velocity at a periphery. 

Periphratic Region.— A region which 
encloses other regions within itself. 

Peripolar Zone. — The zone or region sur- 
rounding the polar zone on the body of 
a patient undergoing electro-therapeutic 
treatment. 

Periscopic Eye-Piece of Microscope. 
An eye-piece consisting of a triple eye- 
lens and a single field-lens, possessing a 
very large and flat field. 

Permanency, Electric. — The property 
possessed by most metallic substances, 
while in a solid state, of retaining a con- 
stant electric conducting power at the 
same temperature. 

Permanent Charge by Induction— An 
induced charge permanently communi- 
cated to a conductor, as distinguished 
from a temporarily induced charge. 

Permanent Currents of Wheatstone 
System.— (1) In the Wheatstone auto- 
matic system the use of a signalling cur- 
rent during the whole period in which a 
signal is transmitted. (2) The continued 
application of current in one or other 
direction on the line. 

Permanent Current Telephone Work- 
ing. — A system of telephony employing 
a constant normal strength of current 
on the line. 

Permanent Electret.— A body whose 
molecules are permanently and inherently 
electrized, as distinguished from a body 
whose molecules are only inherently elec- 
trized while under the influence of some 
change of state. 

Permanent Intensity of Magnetiza- 
tion. — A term employed for the intensity 
of a permanent magnetism produced in 
hard steel, as distinguished from the 
magnetization produced temporarily in 
soft iron. 

Permanent Laminated -Magnet.— A 
term sometimes employed in place of 
compound-magnet. 

Permanent Magnet. — A name sometimes 



given to a magnet composed of hardened 
steel, whose magnetic retentivity is high. 

Permanent-Magnet Voltmeter.— A 
form of voltmeter in which difference 
of potential is measured by the movement 
of a magnetic needle under the combined 
action of a coil and a permanent magnet, 
against the pull of a spring. 

Permanent Magnetism.— M agnetism 
possessed by permanent magnets. 

Permanent Magnetization.— (1) A term 
employed for the magnetization produced 
in a mass of steel or hardened iron when 
brought into a magnetic field. (2) The 
magnetization of a permanent magnet. 

Permanent Magneto-Motive Force.— 
The magneto-motive force of a permanent 
magnet. 

Permanent State of Charge on Tele- 
graphic Line.— (1) The condition of the 
charge on a telegraphic line during the 
time the current passing is at full strength 
in all parts. (2) The charge in a telegraph 
line when insulated at one end and con- 
nected to an E. M. F. at the other. 

Permanent System of Currents.— (1) A 
term sometimes used in telegraphy to 
represent the current sent into a line by 
a double-current kej T . (2) In a Wheat- 
stone's automatic telegraph system the use 
of double currents, whereby a current is 
always flowing on the line. 

Permanent Telegraphic Line.— A term 
employed for a telegraphic line that is in- 
tended to remain in use for an indefinite 
time, in contra distinction to a semi-per- 
manent line which is only designed for 
use during a comparatively limited time. 

Permanent Telegraphic Signals.— Tele- 
graphic signals that are permanently re- 
corded as distinguished from transient or 
unrecorded signals. 

Permeability Bridge.— A device for 
measuring the magnetic permeability of 
a medium, operating on the principle of 
a Wheatstone bridge. 

Permeability Curve.— A curve repre- 
senting the permeability of a magnetic 
substance. 

Permeameter. — An apparatus for deter- 
mining magnetic permeabilities by the 
measurement of the tractive force re- 
quired to detach a mass of soft iron 
having a plane surface, from a magnetic 
pole whose magnetic flux passes perpen- 
dicularly through the surface. 

Permeance, Magnetic. — (1) The recipro- 
cal of magnetic reluctance. (2) The con- 
ductance of a medium to magnetic flux. 

Permeating. — (1) The passage of mag' 



Per.] 



878 



[Pha. 



netic flux through a magnetizable sub- 
stance, or of electrostatic flux through a 
dielectric. (2) Intimately traversing the 
depths of a medium. 

Permeation. — The passage of magnetic 
flux through any permeable substance. 

Permissive Block-System for Rail- 
roads. — A block-system in which two or 
more trains are, under certain conditions, 
permitted to occupy the same block sim- 
ultaneously. 

Permissivity. — A word frequently used 
for permittivity. 

Permittance. — (1) Electrostatic capacity. 
(2) The capability of a condenser or di- 
electric to hold a charge. 

Permittivity. — (1) Specific permittance. 
(2) The dielectric constant. 

Perpendicular. — (1) At right angles to. 
(2) A line at right angles to one or more 
other lines. 

Persistence of Energy. — The indestruc- 
tibility of energy. 

Personal Equation.— A constant obser- 
vational error peculiar to an observer, and 
depending upon his psychological condi- 
tion. 

Perviability. — A word proposed for per- 
meability to electrostatic flux. 

Perviance. — (1) Conductance to electric 
lines of force. (2) The reciprocal of divi- 
ance. 

Petticoat Insulator.— (1) An insulator 
provided with a petticoat, or deep internal 
groove, around its lower extremity, or 
stalk. (2) A line-wire vertical insulator 
"provided with an insulating inverted cup 
having a form resembling a petticoat. (3) 
An ordinary telegraph or telephone single- 
cup insulator. 

Pflugers Law. — A given tract of nerve is 
stimulated by the appearance of cathelec- 
trotonus and the disappearance of anelec- 
trotonus, but not by the disappearance of 
cathelectrotonus and the appearance of 
anelectrotonus. 

Phantom Circuit. — (1) Any of the addi- 
tional circuits established on a telegra- 
phic line by means of any variety of mul- 
tiplex telegraphy. (2) An imaginary cir- 
cuit virtually created by multiplexing a 
telegraph circuit. 

Phantom Streams. — A term sometimes 
applied to a variety of the Tesla streaming 
discharge. 

Phantom Wires.— (1) A term sometimes 
applied to the virtual additional circuits 
or wires obtained in any single wire or 
conductor by the use of any multiplex 



telegraphic system. (2) Phantom cir- 
cuits. 

Phase. — The fractional part of a period, 
which lias elapsed since a vibrating body 
last passed through the extreme point of 
its path in the positive direction. 

Phase Angle. — The angle of phase, in 
a simple-harmonic motion, or the angular 
distance through which the corresponding 
circularly moving point has passed from 
the point of last maximum positive elonga- 
tion. 

Phase Detector. — A device for determin- 
ing the phase of an alternating current, 
electromotive force, or flux. 

Phase Diagram. — A diagram representing 
the magnitude and relative phase position 
of electric pressures or currents. 

Phase-Difference Measurer.— A device 
for measuring difference of phase, be- 
tween any periodically alternating quan- 
tities. 

Phase Indicator.— (1) A device for indi- 
cating when the pressure of an alternator 
is in phase and synchronism with the 
pressure of the circuit with which it is 
to be connected. (2) A term sometimes 
employed for a synchronizer. 

Phase Meter. — A phase-difference meas- 
urer. 

Phase Modification.— The alteration of 
the phase of any periodically alternating 
quantity. 

Phase of Simple-Harmonic Motion.— 
The angle through which the correspond- 
ing circularly moving point has moved 
from the point of maximum positive elon- 
gation. 

Phase of Vibration.— (1) The position 
of the particles in motion in a wave or 
vibration at any instant of time during 
the wave period, as compared with their 
mean position. (2) The phase angle of 
vibration considered as simple-harmonic 
motion. 

Phase Regulation. — The regulation of the 
phase or phases of alternating currents 
or E. M. F.'s. 

Phase-Splitter. — (1) Any apparatus which 
so acts upon an incoming alternating cur- 
rent that the same current goes out in 
different branches as a plurality of cur- 
rents differing in phase. (2) A device for 
producing a difference of phase between ' 
two currents, so as to enable a single-phase 
induction-motor to be self -starting. (3) A 
device for making an alternating current 
split into two or more dephased compo- 
nents. 

Phase Splitting. — The quality or opera- 



Pha.] 



[Pho. 



tion of causing a single alternating cur- 
rent to split into a plurality of relatively 
dephased components. 

Phase Transformation.— A change of 
phase obtained by a transformer whereby 
two-phase currents may be transformed 
into three-phase currents, or vice-versa. 

Phase-Windings.— The separate wind- 
ings on the armature of a polyphase 
motor. 

Phasing Current. — The current produced 
between two dynamos when thrown into 
parallel, which arises from their being 
either not perfectly in phase, or not per- 
fectly equal in pressure, or both. 

Phasing or Wattless-Component.— A 
component of alternating current, 90° out 
of phase with respect to a pressure, and, 
therefore, indifferent to it in respect to 
energy. 

Phasing Transformer.— (1) A trans- 
former capable of effecting a change of 
phase. (2) A transformer for the supply 
of multiphase secondary-currents from 
uniphase primary-currents, or, vice-versa. 

Phelp's Stock Printer. — A form of print- 
ing telegraph employed in sending stock 
quotations telegraphically. 

Phenakistoscope. — An optical toy de- 
pending on the persistence of a retinal 
image, in which the appearance of life is 
obtained from a succession of suitable 
pictures that are caused to rapidly pass 
before the eye. 

Phenomenon. — Any event observed or 
known to occur in nature. 

Pherope. — A name sometimes applied to a 
telephote. 

Philosopher's Egg. — A name given to 
the ovoid or egg-shaped mass of light, that 
appears when a convective discharge is 
taken between two electrodes in a partial 
vacuum. 

Phonautograph. — An apparatus for the 
automatic production of the visible trac- 
ings of the vibrations produced by any 
sounds. 

Phone. — (1) A contraction frequently em- 
ployed for telephone. (2) A message sent 
by telephone. 

Phone. — To send a message by telephone. 

Phoned. — Communicated by telephone. 

Phonic Wheel. — A wheel maintained in 
synchronous rotation by timed electric 
impulses sent over a telegraphic line, and 
employed in the Delany synchronous 
multiplex telegraph system. 

Phoning. — Communicating by telephone. 

Phonogram. — A term proposed for a de- 



spatch transmitted by means of a tele- 
phone. 

Phonograph.— An apparatus for the re- 
cording and reproduction of articulate 
speech, or of sounds of any character, at 
any time after their occurrence, and for a 
number of times. 

Phonograph Record.— A record obtained 
by means of a phonograph. 

Phonographic— Of or pertaining to the 
phonograph. 

Phonophore.— A modified form of har- 
monic telegraph. 

Phonoplex. — A general term embracing 
the apparatus employed in phonoplex 
telegraphy. 

Phonoplex Telegraphic-Receiver.— A 

special form of telephone receiver em- 
ployed in phonoplex telegraphy, which 
responds to brief current impulses but 
not to prolonged impulses. 

Phonoplex Telegraphy. — A system of 
double telegraphic transmission, in which 
telephonic currents, superposed on the 
ordinary Morse currents, actuate a modi- 
fied telephonic receiver, and thus permit 
the simultaneous transmission of two 
separate messages over a single wire 
without interference. 

Phonoplex Transmission.— Double tele- 
graphic transmission obtained by the 
superposition of telephonic and Morse 
currents. 

Phonozenograph. — An instrument de- 
vised to indicate the direction of a distant 
sound. 

Phosphoresce. — To emit phosphorescent 
light. 

Phosphorescence. — The power of emit- 
ting light, or becoming luminous by 
simple exposure to radiant energy. 

Phosphorescence, Electric. — Phosphor- 
escence caused in a substance by the 
passage of an electric discharge. 

Phosphorescent. — Possessing the quality 
of phosphorescence. 

Phosphorescent Glow. — A phosphores- 
cent light emitted by the residual atmos- 
phere of a vacuum tube several seconds 
after an electric discharge has ceased to 
pass through it. 

Phosphorescent Lamp. — A lamp whose 
light is obtained by means of the phos- 
phorescent effects attending electrical 
discharges through a rarified space. 

Phosphorescing. — Emitting phosphor- 
escent light. 

Phosphoroscope. — An apparatus for 



Pho.] 



880 



[Pho. 



measuring the phosphorescent power of 
any substance. 

Phot. — (1) A unit of time-illumination, or 
the total illumination produced by one 
lux for one second of time. (2) The lux- 
second. 

Photo-Chemical. — Relating to photo- 
chemistry. 

Photo -Chemical Effect.— Chemical ef- 
fects produced by the action of radiant 
energy. 

Photo-Chemistry. — The chemistry of the 
effects of radiant energy. 

Photo-Chronograph. — An electric instru- 
ment for automatically recording the 
transit of a star across the meridian. 

Photo-Electric. — Pertaining to the com- 
bined action of light and electricity. 

Photo-Electric Alarm. — (1) An alarm 
operated by means of a photo-electric cell. 
(2) A selenium cell proposed for use in 
connection with the circuit of an electric 
source and suitable electro-receptive de- 
vices, so as to cause the sounding of an 
alarm on the exposure of one of the faces 
of the cell to light. 

Photo-Electric Battery. — Several pho- 
to-electric cells so combined as to be 
capable of acting as a single source. 

Photo-Electric Cell. — A cell capable of 
producing difference of potential when its 
opposite faces are unequally exposed to 
radiant energy. 

Photo-Electric Impulsion-Cell. — A 
photo-electric cell whose sensitiveness to 
light may be restored by slight impulses, 
such as mechanical blows or taps, or by 
electro-magnetic impulses. 

Photo-Electricity . — Difference of electric 
potential produced by the action of light. 

Photo-Electromotive Force.— An elec- 
tro-motive force produced by the action 
of light. 

Photo-Engraving . — Engraving effected 
by the agency of light. 

Photo-Fluoroscopy.— The photography 
of the image obtained on a fluoroscopic 
screen. 

Photographic Meter. — An electric meter 
producing a photographical record. 

Photographic Negative .—A photo- 
graphic picture whose lights and shadows 
are reversed with reference to the 
original. 

Photographic Positive. — A photographic 
picture whose lights and shadows corres- 
pond to those in the natural object. 

Photometer. — An apparatus for measur- 
ing the intensity of the light emitted by 
any luminous source. 



Photometer Bar. — A graduated horizon- 
tal bar designed to carry a photometer 
screen and to indicate by the distance of 
the screen from the sources of light, the 
relative intensities of the lights com- 
pared. 

Photometer Bench. — A photometer bar, 
with or without accessory photometric 
apparatus. 

Photometer Box.— A' 3 darkened box in 
which is placed the photometer screen or 
disc. 

Photometer Disc— The photometer 
screen. 

Photometer, Electric. — An electric in- 
strument for measuring the intensity of 
light or illumination. 

Photometer Gallery.— A name some- 
times given to a photometric bench. 

Photometer Screen. — An opaque or trans- 
lucent screen, employed in a photometer 
for measuring the intensity of light, and 
which receives v the two illuminations to 
be compared. 

Photometric. — Of or pertaining to a pho- 
tometer. 

Photometric - Surface of Luminous 
Source. — A surface formed by the locus 
of points at the ends of lines, obtained by 
laying off lines in various directions pas- 
sing through the luminous source, whose 
lengths measure the intensity of the rays 
emitted in these directions. 

Photometrically. — In a photometric man- 
ner. 

Photo-Micrography.— The photography 
of microscopic objects. 

Photo-Micrography, Electric— The art 
of photographing microscopic images by 
means of the electric light. 

Photophone. — An instrument for the tele- 
phonic transmission of articulate speech 
along a ray of light instead of along a 
conducting wire. 

Photophone Transmitter.— The trans- 
mitter employed in radiophony, in con- 
nection with the photophone. 

Photophore. — An apparatus in which the 
light of a small incandescent lamp is em- 
ployed for purposes of medical explora- 
tion. 

Photosphere. — The luminous envelope 
which surrounds the sun, and which is the 
source of its luminous radiation. 

Photo-Telegraphy.— (1) Telegraphic com- 
munication carried on by means of light. 
(2) Heliography. (3) Radiophony. 

Photo-Voltaic Cell.— A photo-electric 
cell. 



Pho.] 



881 



[Pis. 



Photo- Voltaic Effect.— A change in the 
resistance of selenium or other substance 
produced by its exposure to light. 

Physical Change. — Any change in matter 
resulting from a re-arrangement of its 
molecular groupings, without the forma- 
tion of new molecules, as distinguished 
from a chemical change. 

Physical Equator.— The geographical 
equator. 

Physical Phosphorescence.— Phosphor- 
escence produced in matter by the impact 
of light waves, resulting in a vibratory 
motion of the molecules, of a rapidity suf- 
ficient to cause them to emit light. 

Physical. — (1) Of or pertaining to nature. 
(2) Natural. 

Physiological. — Of or pertaining to phy- 
siology. 

Physiological Coefficient of Illumina- 
tion. — The illuminating value of one watt 
of activity at frequencies within visible 
limits of the spectrum. 

Physiological Rheoscope. — A sensitive 
nerve-muscle preparation employed to 
determine the presence of an electric cur- 
rent. 

Physiologically. — In a physiological man- 
ner. 

Physiologically - Effective Flux of 
Light. — The physiologically-effective il- 
lumination received by any surface. 

Physiologically-Effective Radiation. 
That portion of the radiation which con- 
sists of physiologically active or luminous 
frequencies. 

Physiology, Electro.— The study of the 
electric phenomena of living animals and 
plants. 

Piano, Electric— A piano whose strings 
are struck by hammers actuated by 
means of electro-magnets. 

Picking-Up Gear. — The gear provided in 
a cable ship for the recovery of a sub- 
merged cable. 

Pickle. — An acid solution in which metal- 
lic objects are dipped in order to thor- 
oughly cleanse their surfaces before being 
electro-plated. 

Piece of Wire.— A single length of wire 
without a joint or splice of any descrip- 
tion. 

Pierced-Core Armature.— A perforated 
armature core. 

Piezo-Electricity .— Electrification pro- 
duced in certain crystalline substances by 
pressure. 

Piezometer. — An apparatus for determin- 
ing the compressibility of a liquid. 

56 



Pike Pole. — A straight pole armed at one 
end with a metal point or pike, for use in 
setting up telegraph poles. 

Pile. — (1) A word frequently used for voltaic 
or thermo-electric pile, though more fre- 
quently for the former. (2) A voltaic or 
thermo-electric battery. 

Pilot Brush. — A small accessory brush 
placed on the commutator cylinder for 
the purpose of determining the variations 
in the electromotive force produced in 
various segments. 

Pilot-House Controlling-Gear.— Gear 
placed in the pilot house for the control 
of a search-light projector. 

Pilot Lamp. — (1) A lamp connected across 
the terminals of a dynamo to show roughly 
the pressure which it is producing. (2) A 
lamp placed in a central station, generally 
on the dynamo itself, to indicate the dif- 
ference of potential at the dynamo ter- 
minals by means of the intensity of the 
emitted light. 

Pilot Motor. — (1) A small motor which 
goes ahead of and serves to set in opera- 
tion a larger or working motor. (2) A 
small motor whose sole duty is to actuate 
contacts for controlling the operation of 
a large motor. 

Pilot Transformer. — A small transformer 
placed at any desired portion of a line in 
order to determine its pressure. 

Pilot Wires. — (1) The wires leading di- 
rectly to the generating station from dif- 
ferent parts of the mains, in order to de- 
termine the difference of potential at 
such parts. (2) Wires provided for con- 
nection to a pilot lamp, or other device 
for indicating the maintenance of normal 
pressure. 

Pins. — Wooden pegs for supporting pole 
line insulators. 

Pin Plug. — A plug consisting of a single 
metallic pin with or without an insulat- 
ing head, for bridging a discontinuity in 
a resistance box or switchboard. 

Pipe Conduit. — A conduit formed of suit- 
ably prepared metallic pipes surrounded 
either on the interior or the exterior with 
a cementing compound. 

Pipe Pole. — (1) A pole for aerial wires, 
formed of iron pipes, usually in lengths or 
sections of tapering diameter. (2) A pole 
of iron or steel in tubular form. 

Pipette. — A glass tube suitable for holding 
and removing small quantities of liquid 
for analytical or other purposes. 

Piston Manometer. — A manometer 
whose operation is dependent on the prin- 
ciple of hydraulic pressure. 



Pit.] 



882 



[Pla. 



Pitch. — (1) The frequency of vibration of 
a musical tone. (2) The frequency of an 
electrically produced tone. (3) The dis- 
tance between successive corresponding 
points of symmetry in a mechanical sys- 
tem, such as of screw threads or propeller 
blades. (4) The distance between succes- 
sive corresponding conductors on a dyna- 
mo armature. (5) In an armature wind- 
ing divided into coils or segments, the 
number of coils through which advance 
must be made in making end connections 
between. the coils. 

Pitch Line. — (1) A circle upon the periph- 
ery of which the pitch is measured. 
(2) A circle drawn around the external 
surface of an armature through the mid- 
dle of the length of the inductors placed 
thereon. 

Pitch of Poles. — The distance measured 
along the pitch line between the centres 
either of a pair of poles of opposite sign, 
or of a pair of poles of the same sign. 

Pitch of Windings. — (1) In alternators, 
usually the distance measured along the 
pitch line between the centres of a pair of 
successive poles of opposite sign ; or, in 
some alternators, half this distance. (2) 
In a continuous-current armature, the 
pitch. 

Pitch-Ratio of Alternator.— The ratio of 
the width of a pole-piece, or an armature 
coil, to the pitch of the machine, or dis- 
tance between successive field-pole cen- 
tres as measured on the pitch line. 

Pith. — A light cellular substance that 
forms the central portions of the stalls of 
certain plants. 

Pith Balls. — Two balls of pith, suspended 
from an insulated conductor by conduct- 
ing threads of cotton, or other semi-con- 
ducting substance, and employed for 
showing the presence of a charge on the 
same by their mutual repulsion. 

Pith-Ball Electroscope. — An electro- 
scope whose indications are obtained by 
the attractions or repulsions of pith balls. 

Pivot Suspension. — Suspension of a 
needle by means of a jewelled cup and a 
metallic pivot. 

Pivotal Trolley.— A trolley stand in 
which the pole is supported on a pivot, so 
as to be capable of rotation, for the pur- 
pose of reversing the direction. 

Plain-Pendant Argand Electric Burn- 
er. — A plain-pendant electric burner 
suitable for lighting an Argand gas 
burner. 

Plain-Pendant Electric Burner.— A gas 
burner provided with a pendant for the 



purpose of lighting the gas by means of a 
spark, after the gas has been turned on 
by hand. 

Plaited Electrode Accumulator.— A 

form of storage cell or accumulator, in 
which the electrodes consist of plaited 
strips or ribbons of lead. 

Plane Angle. — (1) An angle contained 
between two straight lines. (2) An angle 
lying in a plane. 

Plane of Polarization of Light.— (1) The 
plane of incidence in a ray of light polar- 
ized by reflection. (2) A plane perpen- 
dicular to the plane of vibration of plane 
polarized light. • 

Plane Vector. — A quantity which pos- 
sesses not only magnitude but also direc- 
tion in a single plane. 

Planimeter. — An instrument for auto- 
matically integrating the areas of plane 
curves, around the contour of which a 
fiducial point on the instrument is carried. 

Piano-Concave. — Flat on one side and 
concave on the other. 

Piano-Convex. — Flat on one side and con- 
vex on the other. 

Plant. — An installation. 

Plant Efficiency.— (1) The efficiency of a 
plant or electric installation. (2) The ef- 
ficiency of a plant as distinguished from 
the distribution system which it operates, 
or by which it may be operated. 

Plant Efficiency of Motor.— The effi- 
ciency of a motor, as distinguished from 
the efficiency of the system with which 
it is connected. 

Plant Electricity. — Electricity produced 
by plants during their growth. 

Plastic. — Possessing the property of plas- 
ticity. 

Plastic-Circuit Microphone.— A micro- 
phone which operates by varying the re- 
sistance of a plastic circuit. 

Plastic Rail-Bond. —In street-railway 
systems, a rail-bond in which contact is 
secured with the rail-ends by sodium 
amalgam, or other conducting material 
applied in a plastic condition . 

Plasticity.— (1) The property of readily 
changing form irncler continuous stress. 
(2) The property of possessing small re- 
sistance to distortional stress. 

Plate Condenser.— (1) A condenser, the 
metallic coatings of which are placed on 
suitably supported dielectric plates. (2) A 
condenser made up of one or more pairs of 
conducting plates separated by a plate or 
plates of non-conducting material. 



Pla.] 



883 



[Pill. 



Plated. — Electro-plated, or covered with 
an electro-metallurgical coating. 

Platform Controller. — An electrical car- 
controller placed on the platform of a car 
for the purpose of starting, stopping and 
regulating the speed of the car. 

Platform Coupling. — An electric coup- 
ling connecting two cars and placed on 
or beneath the platform of the cars. 

Platinating. — Covering a conducting sur- 
face electrolytically with platinum. 

Plating. — A word frequently used for elec- 
tro-plating. 

Plating Balance. — An automatic device 
for disconnecting the current from an 
article to be plated , as soon as a certain 
increase in weight has been reached. 

Plating Dynamo. — A dynamo employed 
for furnishing the current required for a 
plating process. 

Plating Trough. — A term sometimes em- 
ployed for plating bath. 

Platinoid. — An alloy consisting of German 
silver with one or two per cent, of metal- 
lic tungsten, whose electric resistivity is 
only slightly affected by changes of tem- 
perature. 

Platinum. — A heavy, refractory and not 
readily oxydizable metal of a tin-white 
color. 

Platinum Alloy.— An alloy of platinum, 
commonly a platinum-silver alloy. 

Platinum Black. — Finely divided plati- 
num that possesses in a marked degree 
the power of absorbing or occluding 
gases. 

Platinum Fuse.— A thin platinum wire 
rendered incandescent by the passage of 
an electric current, and employed for the 
ignition of a charge of powder. 

Platinum-Iridium Alloy.— An alloy of 
platinum and iridium employed for the 
manufacture of wire sometimes used in 
resistance coils on account of its low tem- 
perature coefficient of resistivity. 

Platinum Lamp.— (1) A lamp whose in- 
candescent filament is formed of a plati- 
num wire. (2) A lamp of molten plati- 
num. (3) A violle. 

Platinum- Silver Alloy. — A name usually 
applied to a particular alloy of one part 
of platinum and two parts of silver, pos- 
sessing a low temperature-coefficient of 
resistivity. 

Platinum Standard Light. — (1) The 
luminous intensity emitted perpendicu- 
larly by a surface of platinum one square 
centimetre in area, at its temperature of 
fusion. (2) The Violle standard. 



Platinum Sulphuric Acid Voltameter. 

A platinum voltameter. 

Platinum Voltameter.— (1) A voltameter 
employing platinum electrodes. (2) A 
voltameter furnished with platinum elec- 
trodes immersed in a dilute solution of 
sulphuric acid and water. 

Platining. — (1) Covering a surface elec- 
trolytically with platinum. (2) Platinum 
plating ; or, electro-plating with plati- 
num. 

Platinizing.— (1) Obtaining a platinum 
coating of a conducting surface by simple 
immersion in a solution of a platinum salt. 
(2) Platining. 

Platymeter. — An instrument employed 
for comparing the capacity of two con- 
densers, or the specific inductive capaci- 
ties of two dielectrics. 

Plow. — A term sometimes employed for 
the sliding contact and its support that is 
pushed before a car, along the trolley 
conductors in an underground trolley 
system. 

Plow, Electric. — An electrically propelled 
plow employed in agriculture. 

Pliicker Tube. — A modification of a 
Geissler tube employed for studying the 
stratification of the light, and the pecul- 
iarities of the space adjoining the nega- 
tive electrode. 

Plug. — (1) A suitably-shaped metallic key 
provided with an insulating handle and 
employed for closing or making contacts. 
(2) An incompetent telegraph operator. 

Plug Cut-Out. — A cut-out employing 
fuse-plugs. 

Plug Hole. — The hole provided in a plug 
switch for the introduction of a plug. 

Plug Key. — A key-shaped plug. 

Plug Operator. — A term of contempt 
sometimes applied to an inefficient tele- 
graphic operator. 

Plug Resistances. — (1) A number of separ- 
ate resistances that can be introduced into 
a circuit by unplugging. (2) The resist- 
ances of the ordinary resistance box. 

Plug Sleeve. — The contact cylinder on 
the surface of a telephone-switchboard 
plug. 

Plug Switch. — A switch operated by the 
insertion of a metallic plug between two 
insulated metallic segments connected to 
a circuit, and separated by air-spaces for 
the reception of the plug key. 

Plug Switchboard. — A switchboard 
whose various circuits are inter-connected 
by means of plug keys. 

Plugging.— (1) Completing a circuit by 



Pill.] 



884 



[Pol. 



means of plugs. (2) In a telephone 
switchboard, the operation of making 
the connections by inserting plugs in the 
proper jacks. 

Plumbago. — (1) An allotropic modifica- 
tion of carbon. (2) Graphite. 

Plunge Battery. — The couples of a vol- 
taic battery so supported on a horizontal 
bar as to be capable of being simultane- 
ously placed in or removed from the ex 
citing liquid. 

Plunger Door-Contact.— A form of elec- 
tric contact for doors in which the closing 
of the door forces in a small plunger 
against the tension of a spring, thereby 
either making or breaking an electric 
alarm circuit. 

Plunger Floor - Contact.— A form of 
plunger contact suitable for being placed 
on the floor and operated by the foot. 

Plunger Switch.— A switch, the operat- 
ing lever cylinder of which passes through 
a bushing in a switchboard, so as to make 
and break contacts at the back of the 
switchboard. 

Plus Charge. — A positive charge. 

Pneumatic. — Of or pertaining to pneuma- 
tics. 

Pneumatic Car-Brake Mechanism.— A 
car-brake operated by air-pressure. 

Pneumatic Perforator. — A paper perfor- 
ator operated by compressed air. 

Pneumatic Rodding.— A method of in- 
troducing a cable or wire into the duct of 
a conduit by the movement of a dart 
driven through the duct by air pressure. 

Pneumatic Telegraph. — A form of in- 
strument for transmitting signals by 
means of air pressure. 

Pneumatic Transmission. — Transmis- 
sion of objects or of power, effected by 
means of compressed air. 

Pneumatics. — That branch of plrysics 
which treats of the properties of gases 
either at rest or in motion. 

Pocket Galvanometer.— A galvanometer 
suitable for carrying in the pocket. 

Pocket G-auge, Electric. — A rough form 
of pocket galvanometer. 

Pocket Telegraphic-Relay.— A relay 
sufficiently small to be readily carried in 
the pocket. 

Pockets in Inside Wiring System.— 
Hollow spaces provided in the walls, 
floors or ceilings of a building for draw- 
ing wires in, for making connections, or 
for inserting safety devices. 

PoggendorfF's Voltaic Cell.— The name 
sometimes given to the Grenet cell. 



Point Discharge. — A term sometimes ap- 
plied to a convective discharge. 

Point of Origin. — (1) In graphics, the 
point where the axes of co-ordinates start. 
(2) The point at which a curve starts. 

Points on Lightning Rod.— Points of 
unoxydizable metal placed on lightning 
rods to effect the quiet discharge of a 
cloud by convection streams. 

Points of Compass. — (1) The thirty-two 
points into which the edge or periphery 
of a compass card is divided. (2) The 
rhumbs of a compass. 

Polar. — Of or pertaining to a pole. 

Pointer Telegraph.— A term sometimes 
used for a dial telegraph. 

Polar Aurora.— A general term for the 
Northern or Southern light. 

Polar Bore of Field Frame. — The bore 
or cylindrical hollow space excavated in 
a field frame for the reception of an ar- 
mature. 

Polar Duplex.— A system of differential 
duplex-telegraphy employing polar-re- 
ceiving relays. 

Polar Duplex-Telegraphy. --Telegraphic 
communication obtained by means of a 
differential duplex in which the current 
flowing from the home battery to line is 
reversed when the home key is depressed. 

Polar Electrolysis.- (1) A form of elec- 
trolysis attended by destruction of the 
tissues. (2) Galvano- Caustics. 

Polar Relay. — In telegraphy, a relay hav- 
ing a normally polarized armature, as 
distinguished from a neutral relay, in 
which the armature is normally in neu- 
tral magnetic condition. 

Polar Surface of Magnet.— (1) The sur- 
faces of one or both poles of a magnet. 
(2) A surface of magnetic material from 
which or into which magnetic flux 
passes. 

Polar Tips.— The free ends of the field- 
magnet pole-pieces of a dynamo-electric 
machine. 

Polar Transformer. — A term sometimes 
employed for an open-circuit transformer. 

Polar Variation Diagram.— A diagram 
drawn to polar co-ordinates and represent- 
ing some relation between periodically 
varying quantities. 

Polar Zone.— The zone or region in the 
human body surrounding a therapeutic 
electrode. 

Polariscope, Electric. — An electric ap- 
paratus for polarizing electro-magnetic 
waves and for revealing the presence of 
polarization. 



Pol.] 



885 



[Pol. 



Polarity.— (1) The possession of poles, or 
of opposite properties, at opposite ends. 
(2) The condition of electric or magnetic 
differentiation between properties of elec- 
tric or magnetic flux depending on and 
inherent in the direction of such flux. 

Polarity Indicator. — Any device for de- 
termining the direction of a current or 
the polarity of a magnet. 

Polarization Battery.— A term some- 
times employed for a secondary or storage 
battery. 

Polarization Current. — In electro-thera- 
peutics the constant current which, when 
passed through a nerve, produces therein 
the electro-tonic state. 

Polarization Current from Fault in 
Cable. — A current due to the polarization 
of a fault or break in a cable under the 
action of a testing current. 

Polarization, Electric.--(l) In dielectrics, 
the condition of being subjected to elec- 
trification. (2) In dielectrics, the condi- 
tion of containing or restoring a residual 
charge. (3) In electrolysis, the condi- 
tion of having free ions liberated at the 
electrodes, whereby a C. E. M. F. is set up. 

Polarization Fault-Current of Cable.— 
A current produced in a cable due to the 
counter-electromotive force set up in a 
fault under the action of a signalling, 
testing, or natural current. 

Polarization of Dielectric. — (1) A molec- 
ular strain produced in the dielectric of 
a Leyden jar, or other condenser, by the 
attraction of the electric charges on its 
opposite faces, or by electrostatic stress. 
(2) A term sometimes employed for elec- 
tric displacement. 

Polarization of Electrolyte. — An as- 
sumed formation of molecular groups or 
chains in which the poles of all the mole- 
cules of any chain are turned in the same 
direction, that is with their positive poles 
facing the negative plate, and their nega- 
tive poles facing the positi ve plate. 

Polarization of Light. — The condition of 
a ray of light in which the vibrations of 
the ether by which the light is propagat- 
ed are all limited to a single plane, the 
plane perpendicular to which is called the 
plane of polarization. 

Polarization of Voltaic Cell.— The col- 
lection of a gas. generally hydrogen, on 
the surface of the negative element of a 
voltaic cell. 

Polarization Battery. — A term some- 
times used for secondary or storage bat- 
tery. 

Polarization Photometer.— A photo- 



meter in which the illumination of the 
stronger of two luminous sources to be 
compared is reduced by polarization. 
Polarized Armature. — An armature 
which possesses a polarity independently 
of that imparted by the working cur- 
rent. 

Polarized Bell. — An electro-magnetic 
bell provided with a polarized armature. 

Polarized Indicator.— Any electro-mag- 
netic indicator employing a polarized 
armature. 

Polarized Ink-Recorder.— An ink-re- 
corder employing a polarized armature. 

Polarized Radiation. — Any radiation 
whose waves are polarized, or restricted 
to a particular plane of vibration. 

Polarized Relay.— (1) A telegraphic re- 
lay provided with a permanently magnet- 
ized armature in place of the ordinary 
soft-iron armature. (2) A polar relay. 
(3) A non-polarized or neutral relay, as 
distinguished from a polarized relay. 

Polarized Ring-Off Drop.— A ring-off 
drop in a telephone switchboard having 
a polarized armature. 

Polarized Sounder. — A telegraphic 
sounder employing a polarized armature. 

Polarizing Current. — A current which 
produces polarization. 

Polarizing Spectro-Photometer. — A 

spectro-photometer employing a polari- 
scope. 

Pole Armature. — (1) An armature whose 
coils are wound on separate poles that 
project from the periphery of a disc, 
drum, or ring armature. (2) An armature 
having polar projections. 

Pole Bands. — Metallic bands placed 
around a pole for the purpose of support- 
ing guy-rods or brackets. 

Pole - Changing and Interrupting 
Electrode Handle. — A handle provided 
for the ready insertion of the electro- 
therapeutic electrodes, containing means 
for interrupting or changing the direction 
of the current. 

Pole Changer.— (1) A switch or key for 
reversing the direction of a current. 
(2) A reverser. (3) A generator of alter- 
nating currents at a telephone exchange, 
consisting of an electro-magnetically 
driven pendulum which periodically re- 
verses a call battery. 

Pole-Changing Key.— (1) A pole changer. 

(2) A key wdiich effects a reversal. 
Pole-Changing Switch. — A switch em- 

ployed for changing the direction of the 

current in any circuit. 



Pol.] 



886 



[Pol. 



Pole Clamp. — An iron clamp on a pole 
employed for the support of span wires or 
brackets. 

Pole Climbers.— Devices employed by 
line-men for climbing wooden telegraphic 
poles. 

Pole Clip.— A pole clamp. 

Pole Counter. — A hand-operated register- 
ing device employed for counting tele- 
graph or other poles. 

Pole Guys. — A guy employed for the stif- 
fening of a pole. 

Pole Hood. — A hood or cover placed at 
the top of a pole. 

Pole Indicator. — Any device for readily 
determining the polarity of a pole, of a 
magnet, or of an electric source. 

Pole-Pieces of Dynamo or Motor.— 
A mass of iron or steel connected with the 
poles of the field-magnets of a dynamo 
or motor, and shaped to conform to the 
outline or contour of the armature. 

Pole Platform.— A platform, capable of 
supporting one or more men, placed on a 
terminal pole, and provided with a cable 
box for the purpose of affording a ready 
means of inspecting and arranging the 
conductors in the box. 

Pole Roof. — A metallic cap or roof of a 
telegraph or telephone pole. 

Pole Shoe. — A plate of iron or steel 
mounted on, and forming the pole-piece 
of a field magnet, and sometimes used 
for supporting a field coil. 

Pole Steps. — Steps permanently fastened 
to a wooden or iron pole to facilitate 
climbing. 

Pole Support for Arc-Lamps.— A sup- 
port placed on the top or end of a pole for 
the reception of an arc-lamp. 

Pole Tips. — A name sometimes employed 
for the horns of a dynamo field pole. 

Pole Top. — A fixture for the top of an 
aerial pole provided with a number of 
arms and insulators for the support of 
additional aerial circuits. 

Poles of Condenser.— The terminals of a 
condenser. 

Poles of Magnetic Intensity. — The 

earth's magnetic poles as determined by 
means of observations of magnetic inten- 
sity. 

Poles of Magnetic Verticity.— The 
earth's magnetic poles as determined by 
means of a dipping needle. 

Poling Boards.— Short rough boards laid 
vertically against the sides of an excava- 
tion, in packed soil, and kept in place by 
cross struts. 



Polishing Bob.— A disc of tough wood 
provided on its edge with a ring or rim of 
leather or hide, on which finely divided 
emery is placed, employed, when mounted 
on a shaft and put in rapid rotation, for , 
polishing articles so as to prepare them i 
for electro-plating. 

Polishing Mop.— A disc formed of circu- 
lar pieces of calico, felt, or other similar 
soft material, mounted on a shaft and em- 
ployed, when put in rapid rotation, for- 
polishing surfaces for electro-plating. 

Polycyclic System.— A multiphase sys- 
tem. 

Polymerism. — A species of isomerism in 
which chemical compounds of the same 
proportional constitution, as determined 
by analysis, have different properties, due 
to having different numbers of atoms in 
their molecules. 

Polymorphic Instrument.— A term 
sometimes used for a polymorphic ma- 
chine. 

Polymorphic Machine.— An apparatus 
capable of effecting the transformation of 
alternating-currents from one species to 
another. 

Polyphasal Coupling of Magnetic Cir- 
cuits. — The inter-linking of magnetic 
circuits traversed by polyphase magnetic 
fluxes. 

Polyphase. — Possessing more than a single 
phase. 

Polyphase Alternator.— An alternator 
capable of supplying polyphase currents. 

Polyphase Apparatus.— Apparatus oper- 
ated by polyphase currents. 

Polyphase Armature.— An armature so 
wound as either to produce polyphase cur- 
rents, or to be operated by such currents. 

Polyphase Armature-Windings. — 
Windings of polyphase generators. 

Polyphase Asynchronous Motor.— (1) 
An asynchronous motor operated by mul- 
tiphase currents. (2) A multiphase in- 
duction motor. 

Polyphase Choking-Coil.— (1) A choking 
coil in a polyphase system. (2) A chok- 
ing coil operated by polyphase currents. , 

Polyphase Circuits. — The circuits em- 
ployed in polyphase-current distribution. 

Polyphase Currents.— Currents differing 
in phase from one another by a definite 
amount, and suitable for the operation of 
polyphase motors or similar apparatus. 

Polyphase Dynamo.— A polyphase gen- 
erator. 
Polyphase Generator.— An alternator 



Pol.] 



887 



[Pos. 



which delivers two or more alternating 
currents definitely differing in phase. 

Polyphase Inductor - Alternator.— An 
inductor alternator suitable for producing 
polyphase currents. 

Polyphase Inductor-Generator.— (1) A 
polyphase generator of the inductor type 
in 'which no conductor or winding is 
rotated. (2) A polyphase inductor-alter- 
nator. 

Polyphase Motor. — A motor operated by 
means of polyphase currents. 

Polyphase Power. — Power transmitted 
by means of polyphase currents. 

Polyphase Rotary - Converter.— A ro- 
tary converter operated by or producing 
polyphase currents. 

Polyphase Switchboard. — A switch- 
board suitable for controlling polyphase 
circuits. 

Polyphase Synchronous - Motor.— A 
synchronous motor operated by polyphase 
currents. 

Polyphase Transformer. — A transform- 
er suitable for use in connection with 
polyphase circuits. 

Polyphase Transmission. —Transmis- 
sion of power by means of polyphase 
currents. 

Polyphase Working.— A general term 
employed to express the application of 
polyphase currents. 

Polyphased Alternating-Currents.— A 
term employed for polyphase currents. 

Polyphaser. — (1) A term sometimes em- 
ployed for a polyphase alternator, or 
generator. (2) A multiphaser. 

Polyphotal Arc-Light Regulator.— A 
regulator for arc-lamps suitable for use 
in a number of series-connected arc 
lamps. 

Poncelet. — A name proposed for a unit of 
activity equal to 100 kilogramme-metres 
per second ; or, approximately, one kilo- 
watt. 

Pondermotive Force.— The . force re- 
quired for the movement of gross matter. 

Pony Insulators. — A name given to a par- 
ticular type of glass telegraph insulator. 

Pony Telegraphic Relay.— A name ap- 
plied to a particular form of telegraphic 
relay. 

Porcelain. — A variety of insulating sub- 
stance, made from kaolin. 

Porcelain Insulator. — Any insulator of 
porcelain for supporting a wire. 

Porcelain Wire-Tube.— A porcelain tube 



employed for passing an electric wire 
through a partition. 

Porosity. — A property of matter in virtue 
of which spaces or pores are left between 
its constituent atoms and molecules. 

Porous Cell. — A jar of unglazed earthen- 
ware employed in a double-fluid voltaic 
cell to mechanically separate the two 
electrolytes. 

Porous Cup.— A porous cell. 

Porous Insulation. — An insulating ma- 
terial containing air or other gas. 

Porous Jar or Pot.— A porous cell. 

Porret's Phenomenon. — An increase in 
the diameter of a nerve fibre in the neigh- 
borhood of the positive pole, when trav- 
ersed by a voltaic current. 

Portable Conductors.— Flexible cords 
containing insulated wires suitable for 
use with portable lamps, motors, or other 
devices. 

Portable Electrometer. — A form of read- 
ily transportable Thomson electrometer. 

Portable Igniting Device.— (1) A porta- 
ble electric mine-exploder. (2) A porta- 
ble electric gas-igniter. 

Portable-Lamp Guard.— A guard pro- 
vided for the protection of a portable 
lamp. 

Portable Tachometer.— A portable speed 
indicator. 

Portative Power of Magnet. — The lift- 
ing or sustaining power of a magnet. 

Portelectric. — (1) An electric carrier. (2) 
A system of electric transportation by 
means of the successive attractions of a 
number of hollow helices of insulated 
wire on a moving iron core. 

Portrait, Electric. — A portrait formed on 
paper by the electric volatilization of gold 
or other metal. 

Position-Finder, Electric— An electric 
device by means of which the position of a 
distant object can be determined. 

Positive Brush of Dynamo.— The brush 
of a dynamo out from which flows the 
current generated in the armature. 

Positive Brush of Motor. — The brush 
connected to the positive terminal qf a 
driving source. 

Positive Carbon. — That carbon of a vol- 
taic arc out from which the current flows 
into the arc. 

Positive Charge. — (1) According to the 
double-fluid hypothesis, a charge of posi- 
tive electricity. (2) According to the 
single-fluid hypothesis, any excess of an 
assumed electric fluid. (3) A charge of 
electricity having a positive potential. 



Pos.] 



888 



[Pot, 



Positive Currents.— A term employed in 
telegraphy for currents sent over a line 
from the positive pole of a battery. 

Positive-Direction of Lines of Mag- 
netic Force. — The direction in which a 
free north-seeking pole would move along 
the lines of force when placed in a mag- 
netic field. 

Positive - Direction of Simple - Har- 
monic Motion.— The motion which a 
body moving with simple-harmonic mo- 
tion has, when its corresponding circularly 
moving point moves counter-clockwise. 

Positive-Direction of Electric Con- 
vection of Heat. — A direction in which 
heat is transmitted through an unequally 
heated conductor by electric convection 
during the passage of electricity through 
the conductor, the same as that of the 
current. 

Positive-Direction Round a Circuit.— 
In a plane circuit looked at from the posi- 
tive side, a direction opposed to that of 
the hands of a clock. 

Positive-Direction Through a Circuit. 
In a plane circuit carrying a positive cur- 
rent, a direction through the circuit simi- 
lar to that of the advance of a corkscrew 
which is twisted round in the direction 
of the current. 

Positive Electricity.— (1) One of the 
phases of electric excitement. (2) That 
kind of electric charge produced on cot- 
ton when rubbed against resin. 

Positive Electrification. — (1) The charge 
of a body with positive electricity. (2) A 
positive charge. (3) An electrification of 
positive potential. 

Positive Electrode. — The electrode con- 
nected with the positive pole of an elec- 
tric source. 

Positive Electromotive Force.— An 
E. M. F. which will communicate a posi- 
tive charge. 

Positive Feeders. — The feeders that are 
connected with the positive terminal of 
a dynamo. 

Positive Fluid.— (1) The specific fluid that 
was formerly believed by the adherents 
of the double-fluid electric hypothesis to 
be the cause of electric excitement. (2) 
The surplusage of an assumed single 
electric fluid. 

Positive Lead. — In a system of parallel 
distribution, a lead connected with the 
positive generator-terminal, or with the 
positive bus-bars. 

Positive Omnibus-Bars. — The bus-bars 
that are connected with the positive ter- 
minal of a dynamo. 



Positive Phase of Electrotonus.— An 

increase in the electromotive force of a 
nerve produced by sending a current 
through the nerve in the same direction 
as the nerve current. 
Positive Plate of Storage Cell.— (1) That 
plate of a storage cell which is converted 
into, or covered by, a layer of lead peroxide 
by the action of the charging current. 
(2) That plate of a storage cell which is 
connected with the positive terminal of a 
charging source, and which is, therefore, 
the positive pole of the cell on dis- 
charging. 

Positive Plate of Voltaic Cell.— (1) The 
electro-positive element of a voltaic 
couple. (2) That element of a voltaic 
couple which is positive in the electrolyte 
of the cell. (3) The plate which forms 
above the surface of the electrolyte, the 
negative pole of the cell. 

Positive Pole. — That pole of an electric 
source out of which the current is as- 
sumed to flow. 

Positive Potential.— (1) That potential in 
a circuit external to a source from which 
the electric current flows. (2) The higher 
potential or higher electric level. 

Positive Rotation. — Left-handed or coun- 
ter-clockwise rotation. 

Positive Side of Circuit.— That side of a 
circuit bent in the form of a circle in 
which, if an observer stood with his head 
in the positive region, he would see the 
current pass around him counter-clock- 
wise. 

Positive Spark.— A spark produced by 
the disruptive discharge of a positively 
charged conductor. 

Positive Terminal.— The terminal con- 
nected with the positive pole of a source. 

Positive Wire. — The wire connected with 
the positive pole of a source. 

Positively Excited.— Charged with posi- 
tive electricity. 

Pot Operator. — (1) The operator which is 
the double inverse of the curl operator. 
(2) The operator which acting upon a 
point function in space produces its vector 
potential. 

Potash Brush. — A brush employed in 
cleansing, by the use of a caustic solution, 
surfaces which are to be electro-plated. 

Potential Dynamometer. — An electro- 
dynamometer suitably arranged for the 
measurement of electric potential differ- 
ences. 

Potential, Electric— (1) The power of 
doing electric work. (2) Electric level. 



Pot.] 



889 



[Pra. 



Potential Energy.— (1) Stored energy. 

(2) Potency or capability of doing work. 

(3) Energy possessing the power or potency 
of doing work, but not actually perform- 
ing such work. 

Potential Function. — A point function 
of space, whose space differentiation 
gives a vector point-function. 

Potential Galvanometer. — A term some- 
times applied to a voltmeter. 

Potential Gradient.— (1) The rate-of-fall 
of potential at a point. (2) A line repre- 
senting the fall of potential in a circuit. 

Potential Indicator. — An apparatus for 
indicating potential difference. 

Potential of Conductors. — (1) The rela- 
tion existing between the quantity of 
electricity in a conductor and its ca- 
pacity. (2) That property of a conductor 
whereby electric work is done when an 
electric charge is moved towards it. 

Potential Receptacle. — A receptacle in 
a switchboard, wall, cover, base, or other 
device, for receiving a plug connected to 
a potential-indicator, or voltmeter. 

Potentiometer. — An apparatus for the 
galvanometric measurement of electro- 
motive forces, or differences of potential, 
by a zero method, and by relation to a 
standard E. M. F. 

Potentiometer Voltmeter. — A voltmeter 
operating on the potentiometer principle 
and employing a standard voltaic cell as 
its basis of measurement. 

Potentiometer Wire.— A graduated wire 
employed in a potentiometer for the pur- 
pose of securing proportionate linear re- 
sistances and thereby proportional poten- 
tial differences. 

Pounds-Per-Mile-Ohm. — (1) A standard 
of conductivity of telegraph or telephone 
wires. (2) The weight of a uniform wire 
offering one ohm per mile at standard 
temperature. 

Poundal.— (1) The weight of a pound, or 
the earth's attraction upon the mass of a 
pound of matter, at any terrestrial locality. 
(2) A gravitational unit of force. 

Power. — (1) Rate-of-doing-work, express- 
ible in watts, joules-per-second, foot- 
pounds-per-hour, etc. (2) Activity. 

Power Cable. — A cable employed for the 
electric transmission of power. 

Power Circuits. — Circuits employed for 
the electric transmission of power. 

Power Coefficient. — (1) In an alternat- 
ing-current circuit, the ratio of the 
power component of electromotive force 
to the power component of current. (2) 



The apparent resistance of an alternating- 
current circuit. 

Power Cylinder. — The commutating 
cylinder of a street-car controller as dis- 
tinguished from the reversing cylinder. 

Power, Electric. — Power developed by 
means of electricity. 

Power Electromotive Force.— A term 
sometimes employed for that component 
of the E. M. F. acting in the same direc- 
tion with the current, or in phase with it, 
and expended in overcoming effective or 
ohmic resistance. 

Power Factor.— The ratio of the true 
watts to the apparent volt-amperes in an 
alternating-current conductor, circuit, or 
device. 

Power-Factor of Transformer.— The 
ratio of the true watts absorbed by a 
transformer under a given load to the ap- 
parent watts absorbed. 

Power Generator. — A generator of alter- 
nating currents at a central telephone ex- 
change. 

Power-House. — A house provided with 
the plant necessary for the production of 
the electric power required in a system 
of electric distribution. 

Power Measurer, Electric. — A watt- 
meter. 

Power Meter. — A wattmeter. 

Power of Periodic Currents.— With- 
simple-harmonic currents, the product of 
effective current strength, the driving 
effective pressure, and the cosine of the 
difference of phase between them. 

Power-Wire of Monocyclic System. 
The wire or circuit of a monocyclic sys- 
tem employed for supplying currents for 
the operation of triphase electric motors. 

Poynting's Law. — At any point in space, 
electro-magnetic energy moves perpen- 
dicularly to the plane containing the lines 
of electric force and the lines of magnetic 
force, and the amount of energy per second 
crossing the unit area of this plane is 
equal to the product of the intensities of 
the two forces, multiplied by the sine of 
the angle between them, and divided by 

Practical Current. — A term sometimes 
employed for the effective current in an 
alternating-current circuit. 

Practical Solenoid. — A name applied to 
an ordinary solenoid, in order to distin- 
guish it from an ideal solenoid. 

Practical Unit of Inductance.— (1) A 
unit of length equal to the earth's quad- 
rant, or 10 9 centimetres. (2) The henry. 



Pra.] 



890 



[Pl-i. 



Practical Unit of Magneto-Motive 
Force. — A value of magneto-motive force 
equal to 47r multiplied by an ampere of one 
turn, or equal to one-tenth of an absolute 
unit of M. M. F. 

Practical Unit of Self-induction.— A 
term frequently used for the practical 
unit of inductance. 

Practical Units. — Definitely related mul- 
tiples or sub-multiples of the absolute or 
centimetre-gramme-second units. . 

Preamble. — In telegraphy, the opening 
words of a despatch containing the names 
of the sending and delivery stations, the 
number of words in the message, the 
code time, and other service instructions, 
as distinguished from the text of the mes- 
sage. 

Prefix. — In telegraphy, a code letter or 
group of letters prefixed to a message to 
indicate its nature or relative importance. 

Prepayment Meter. — A device whereby 
a certain electric service is given by 
means of an electric penny-in-the-slot ap- 
paratus. 

Presbyopic— Far-sighted. 

Press Button. — A push-button. 

Press Message. — (1) A message directed 
to a newspaper or daily publication. (2) 
A news message. 

Press Telegram. — A press message. 

•Pressant. — A name proposed for a unit of 
magneto-motive force. 

Pressel. — (1) A press switch or push con- 
nected to the end of a flexible pendant 
conductor. (2) A pendant press-button. 

Pressure, Electric. — A term sometimes 
employed for difference of potential, or 
electromotive force. 

Pressure Equalizer. — (1) An automatic 
device employed in connection with a 
storage battery to maintain a uniform 
pressure at its terminals under different 
loads. (2) A regulating device employed 
in a system of electric distribution for 
maintaining the pressure uniform. 

Pressure Indicator. — Any device for in- 
dicating the electric pressure in a circuit. 

Pressure Panel of Switchboard.— That 
panel in a switchboard which contains 
apparatus for measuring the mean electric 
pressure in the power house. 

Pressure Recording-Gauge.— Any form 
of recording voltmeter. 

Pressure Wires. — Small insulated copper 
conductors, employed in a system of un- 
derground street mains, extending from 
points of junction between the feeders 
and the mains to the central station, to 



indicate in the central station the pres- 
sure supplied to the mains. 

Pricking Wires. — A method sometimes 
adopted for locating a wire, by connect- 
ing a battery with one pole to earth and 
the other pole to the wire sought for, by 
means of a brad-awl or needle inserted 
through the gutta-percha insulating ma- 
terial. 

Primary Admittance. — The admittance 
of the primary coil or coils of an alternat- 
ing-current transformer or induction ma- 
chine. 

Primary Ampere-Turns.— The ampere- 
turns in the primary coil of a transformer. 

Primary Battery. — The combination of a 
number of separate primary cells to form 
a single electric source. 

Primary Cell. — A term sometimes em- 
ployed for a voltaic cell. 

Primary Coil of Transformer.— (1) That 
coil of an induction coil or transformer 
on which the primary electromotive force 
is impressed. (2) The driving coil of a 
transformer. (3) The coil which receives 
energy prior to transformation. 

Primary Currents.— Currents flowing in 
a primary circuit, as distinguished from 
cnrrents flowing in a secondary circuit. 

Primary Cut-Out. — A cut-out placed in 
the primary circuit of a transformer. 

Primary Electric Clock. — A term some- 
times employed in place of controlling or 
master clock. 

Primary Electric Heater.— A term pro- 
posed for the main electric heater in a 
building. 

Primary Electromotive Force.— The 
electromotive force applied to the pri- 
mary coil of a transformer. 

Primary Element of Induction Motor. 
The element connected with the line or 
lines, as distinguished from the element 
closed upon itself. 

Primary Fuse Box. — A fuse box placed 
in the primary circuit of an induction 
coil or transformer. 

Primary Impedance. — (1) The imped- 
ance of the primary coil of a transformer, 
or of an induction machine. (2) The 
impedance of the primary coil of a trans- 
former, or of an induction machine, in- 
dependent of the reactance of mutual 
inductance, or the C. E. M. F. of mutual 
linkage. 

Primary Plate of Condenser. — That 
plate of a condensing transformer in 
which the inducing charge is placed in 
order to induce a charge of different 
potential in the secondary plate. 



Pri.] 



891 



[Pro, 



Primary Spiral of Induction Coil.— The 
primary of an induction coil or trans- 
former. 

Prime Conductor.— The positive conduc- 
tor of a frictional electric or electrostatic 
machine. 

Prime Flux-Density. — The magnetic 
density of the prime magnetic flux in a 
ferric circuit. 

Prime Magneto-Motive Force.— The 
magneto-motive force due to the magnet- 
izing current in a ferric circuit. 

Prime Magnetic Flux. — (1) A term em- 
ployed for the flux produced in a ferric 
circuit by the prime magneto-motive 
force, as distinguished from the induced, 
aligned, or structural magneto-motive 
force. (2) Magnetizing force as distin- 
guished from magnetic induction. 

Prime Motor. — A prime mover. 

Prime Mover. — A motor which drives the 
secondary motors or movers. 

Primordial Atoms. — The atoms or com- 
pounds into which it has been assumed 
that the so-called elementary atoms of 
ordinary matter are broken up by means 
of the cathode rays. 

Principal Circuit. — A main circuit as dis- 
tinguished from a derivation circuit. 

Principal Current. — A main current as 
distinguished from a derivation current. 

Principal Telegraphic Circuit.— A term 
sometimes used for the main circuit. 

Principal Telegraphic Current.— A 
term sometimes employed for the main 
current. 

Printing Telegraphy. — A system of teleg- 
raphy in which the messages received 
are printed on a paper fillet. 

Prism Error of Compass. — The error in 
a magnetic bearing due to an inaccurate 
setting of the prism relatively to the com- 
pass card. 

Probable Error of an Observation.— A 
magnitude of accidental error in the re- 
peated observation of a quantity, such 
that it is just as probable that the real 
accidental error is greater as that it is less 
than this magnitude. 

Probe, Electric. — A metallic conductor 
inserted in the body of a patient in order 
to ascertain the position of a bullet or 
other foreign metallic substance. 

Process of Carbonization. — Means for 
carbonizing carbonizable material. 

Production of Cold by Electricity.— 
The absorption of energy, and consequent 
reduction of temperature at a thermo- 
electric junction, by the passage of an 



electric current in a certain direction 
across such junction. 

Production of Electricity by Light. — 
The production of electric difference of 
potential by the action of light. 

Prognosis, Electric. — A prognosis or pre- 
diction of the fatal or non-fatal termina- 
tion of a disease from an electric diagno- 
sis, based on the exaggerated or dimin- 
ished reactions of the excitable tissues of 
the body, when subjected to the varying 
influences of electric currents. 

Progression of Magnetic Flux.— In a 
polyphase motor, the circular motion of 
the magnetic flux around the field or 
armature. 

Projecting Power of Magnet.— (1) The 
range within which a magnet produces 
sensible attraction or repulsion. (2) The 
power of an electro-magnet to repel a 
suitably placed armature. 

Projection Arc-Lamp. — An arc-lamp 
suitable for use in a projector or search- 
light. 

Projector, Electric— A projector or 
search-light provided with an electric arc- 
light at its focus. 

Projection Armatures. — Slotted arma- 
tures in which the width of the slot is suf- 
ficiently great to leave a distinct projec- 
tion in the armature surface as distin- 
guished from tunnel armatures in which 
the slot is very narrow. 

Prony Brake. — A mechanical device for 
measuring the power of a driving shaft 
by the application of a brake to the periph- 
ery of a wheel firmly keyed on the shaft. 

Proof-Plane. — A small insulated conduc- 
tor employed to take and carry electric 
charges from the surfaces of insulated 
charged conductors. 

Proportional Coils. — Pairs of resistance 
coils, generally of 10, 100 and 1,000 ohms 
each, forming the proportional arms of 
a balance or bridge, and. employed in the 
box or commercial form of Wheatstone's 
bridge. 

Proportionate Arms.— The two resist- 
ances or arms of an electric bridge, whose 
relative or proportionate resistances only 
are required to be known, in order to de- 
termine in connection with a known re- 
sistance, the value of an unknown resist- 
tance placed in the remaining arm of the 
bridge. 

Proposed Definition for 2,000 Candle- 
Power Arc. — <1) Such an arc as will re- 
quire at ordinary pressures 450 watts ac- 
tivity to maintain it. (2) A 450- watt arc. 



Pro.] 



892 



[Pum, 



Propulsion, Electric— A general term 
for driving by electric power. 

Prostration, Electric— Physiological ex- 
haustion or prostration, resembling that 
produced by sun-stroke, resulting from 
exposure to an unusually powerful arc. 

Protecting Battery. — In submarine cable 
telegraphy, a battery permanently con- 
nected to a faulty cable through a high re- 
sistance, for the purpose of sending a 
negative current through the fault in 
order to keep the exposed surface of the 
conductor free from corrosion salts. 

Protection of Houses, Ships or Build- 
ings, Electric — Means for protection 
from the destructive effects of a lightning 
discharge, consisting essentially in the 
use either of lightning-rods or of an en- 
closing conducting shell. 

Protection of Metals, Electric— The 
protection of a metal from corrosion by 
placing it in connection with another 
metal, which, when exposed to the cor- 
roding liquid, vapor or gas, will form 
with the surrounding liquid the positive 
element of a voltaic couple and will, 
therefore, alone be corroded. 

Protection of Ship's Sheathing, Elec- 
tric — Attaching pieces of zinc to the 
copper sheathing of a ship for the purpose 
of preventing the corrosion of the copper 
by the water. 

Protective Action.— (1) The electric pro- 
tection of metals. (2) The protection of 
structures from lightning by lightning 
protectors. 

Protective Sheath. — A device attached 
to a transformer or converter, consisting 
of a copper strip or plate connected to 
the earth and interposed between the 
primary and secondary windings, to pre- 
vent any connection from taking place 
between the high-potential primary and 
the low-potential secondary circuit. 

Protective Throw. — A term proposed for 
the protection afforded by a magnetic 
field to paramagnetic metals exposed to 
chemical action. 

Protoplasm.— Bioplasm. 

Psyehrometer. — A form of recording hy- 
grometer. 

Public Supply Instruments. — Electric 
meters designed for registering the cur- 
rent or energy supplied to a consumer. 

Pull. — A contact-maker similar in general 
construction to a push-button, but oper- 
ated by a pull instead of by a push. 

Pull Contact.— Any contact that is ef- 
fected by the movement of a pendant or 
pull. 



Pulley. — A wheel placed on a shaft for the 
driving of the same by means of a belt. 

Pull-Off. — (1) An insulator employed on 
curves to hold the trolley wire in proper 
position. (2) A steel wire attached to a 
trolley wire through an insulator, and 
employed to pull the trolley wire into 
position over a curve in the track. 

Pull-Off Pole.— A pole provided for the 
suspension of a pull-off wire, or wires. 

Pulsating Current. — A pulsatory current. 

Pulsating Electromotive Force.— An 
electromotive force whose direction is 
pulsatory. 

Pulsating Motor.— A motor employing a 
reciprocating movement in its armature 
as opposed to the ordinary rotary motion. 

Pulsation.— (1) A quantity of the nature 
of an angular velocity, equal to 2 tt mul- 
tiplied by the frequency of the oscillation, 
or to 2 tt divided by the duration of a 
single period. (2) In a simple-harmonic 
current circuit, the angular velocity of 
the corresponding circularly moving 
point. 

Pulsation, Electric— An electric pulse 
or oscillation. 

Pulsation of Reactance. — Variations 
periodically occurring in the apparent 
reactance of an alternating-current cir- 
cuit or machine. 

Pulsation of Resistance. — Periodic vari- 
ations in the apparent resistance of an 
alternating-current circuit or apparatus. 

Pulsatory Continuous-Current. — A 
current whose direction remains constant, 
but whose intensity is subject to steady 
changes. 

Pulsatory Electromotive Force.— An 
electromotive force whose value is sub- 
ject to pulsatory changes. 

Pulsatory Magnetic-Field. — A field 
whose strength pulsates in such a man- 
ner as to induce oscillatory currents in 
neighboring circuits. 

Pulsatory Magnetism.— Magnetism pro- 
duced by pulsatory currents. 

Pulse, Electric. — (1) An electric oscilla- 
tion. (2) A momentary flow of electricity 
through a conductor which gradually 
varies from zero value to the maximum, 
and then to zero value again, like a pulse 
or vibration in an elastic medium. 

Pumping of Alternating-Current Dy- 
namo. — A pulsation in the motion of a 
synchronously-running altern atin g-cur- 
rent generator or motor, due to imperfect 
synchronism. 

Pumping of Electric Lights.— A term 



Pun.] 



893 



[Pyr. 



sometimes applied to a pulsatory or peri- 
odic increase or decrease in the brilliancy 
of lights. 

Punched - Clip Switch.— A form of 
switch in which the clips are punched out 
of sheet metal. 

Puncher. — In automatic telegraphy, a per- 
forator. 

Punning of Telegraph Pole.— The proc- 
ess of packing the earth around the base 
of a telegraph pole. 

Pupillary Photometer.— A photometer 
whose operation is dependent on the 
diminution of the diameter of the pupil 
of the eye with the intensity of the light 
striking the eye. 

Pure Spectrum. — A single spectrum or 
distribution of luminous frequencies as 
distinguished from a spectrum which is 
formed by the superposition of a number 
of spectra slightly displaced with refer- 
ence to one another. 

Push. — A term sometimes applied to a 
push button. 

Push Box. — A box provided for the recep- 
tion of the mechanism of a push button 
or push. 

Push Button. — A device for closing an 
electric circuit by the movement of a 
button. 

Push-Button Rattler.— (1) A device con- 
nected with a push-button to show that a 
bell connected at a distant point in the cir- 
cuit of the button rings when the button 
is pressed. (2) A push-button combined 
with an electro-magnetic vibrator. 

Push-Button Socket.— A socket provided 
with a push-button for the closing of a 
circuit. 

Push-Button Socket-Key. — An incan- 
descent lamp-socket so provided with a 
push-button key as to permit the lamp to 
be readily lighted or extinguished by the 
same hand that holds it. 

Push-Button Switch. — A switch oper- 
ated by a push-button. 

Push Contact. — A name sometimes ap- 
plied to a push button. 

Putting Straight.— The operation of re- 
storing the normal condition of wires 
which have been crossed at two way 
stations. 

Pyknometer. — A term sometimes used 



for a specific gravity bottle, employed in 
determining the specific gravity of a 
liquid. 

Pyr. — (1) A bougie-decimale. (2) A pro- 
posed unit of luminous intensity equal to 
the one-twentieth of the Violle standard. 
(3) A proposed name for the one-twen- 
tieth of the Violle standard. 

Pyrheliometer. — An apparatus for meas- 
uring the energy of solar radiation. 

Pyro-Electric. — Pertaining to pyro-elec- 
tricity. 

Pyro-Electric Crystal.— Any crystalline 
substance capable of producing pyro- 
electric phenomena on being unequally 
heated. 

Pyro-Electricity. — Electricity produced 
in certain crystalline bodies by their un- 
equal heating or cooling. 

Pyrogravure. — A process for the decora- 
tion of wood, copper, or glass, by the burn- 
ing action of an electrically or otherwise 
heated tool. 

Pyro-Magnetic. — Of or pertaining to 
pyro-magnetism. 

Pyro-Magnetic Electric Device.— Any 
device operated by or employing pyro- 
magnetism. 

Pyro-Magnetic Generator or Dynamo. 
An apparatus for producing electricity 
directly from the heat derived from 
burning fuel. 

Pyro-Magnetic Motor. — A motor con- 
sisting of an armature formed of a disc 
or ring of thin steel, which is set in mo- 
tion when unequally heated, by reason of 
the difference in the coercive force so 
produced. 

Pyro-Magnetism. — A term sometimes 
applied to the phenomena of the com- 
bined effects of magnetism and heat. 

Pyrometer. — An instrument for deter- 
mining temperatures higher than those 
which can be readily measured by ther- 
mometers. 

Pyrometer, Electric. — A device for de- 
termining the temperature of a body by 
the measurement of the electric resist- 
ance of a platinum wire exposed to the 
heat to be measured. 

Pyr-Steradian.— (1) The flux of light cor- 
responding to the luminous intensity of 
one pyr extending over the solid angle of 
one steradian. (2) A term sometimes 
used for lumen. 



Q.] 



894 



[Qua. 



Q or q. — A contraction for electric quantity. 

Quad. — (1) A contraction for quadruplex 
telegraphy. (2) An abbreviation some- 
times employed for the quadrant or the 
unit of self -inductance. 

Quad-Meter. — (1) A secohm meter. (2) 
An instrument for measuring inductance. 

Quadrant. — A term proposed for the earth 
quadrant or practical unit of self-induc- 
tion, now officially recognized as the 
henry. (2) The length of the arc, from 
the pole to the equator, on a terrestrial 
meridian circle extending through Paris, 
or very nearly 10,000 kilometers. 

Quadrant Electrometer. — An electro- 
meter in which an electrostatic charge is 
measured by the attractive and repulsive 
force exerted by four plates or quadrants 
on a light needle of aluminium suspended 
between them. 

Quadrantal Deviation of Mariner's 
Compass. — (1) The deviation of a mag- 
netic needle due to the induced mag- 
netism in the iron of a ship acting as a 
mass of soft iron, and not as a permanent 
magnet. (2) The deviation of a compass 
needle on board ship which changes sign 
once in each quadrant. 

Quadrantal Error. — The quadrantal de- 
viation of a mariner's compass as dis- 
tinguished from either the semicircular or 
the heeling error. 

Quadrature. — A term applied to express 
the fact that one simple-harmonic quan- 
tity lags 90° behind another. 

Quadruplex Circuit. — A circuit em- 
ployed in quadruplex telegraphy. 

Quadruplex Connector. — Any connec- 
tor suitable for connecting the four ends 
of four wires. 

Quadripolar Dynamo or G-enerator. — 
A multipolar dynamo having four poles 
in its field frame, or four magnetic cir- 
cuits through its armature. 

Quadripolar Field.— A field produced by 
four separate magnet poles. 

Quadruplex. — Of or pertaining to quad- 
ruplex telegraphy. 

Quadruplex Balance. — The balance ob- 
tained in a quadruplex circuit in order to 
permit quadruplex transmission. 

Quadruplex Circuit. — Any single circuit 
over which four separate messages can 
be simultaneously transmitted, two in one 



direction and the remaining two in the 
opposite direction. 

Quadruplex Telegraph. — A general 
term embracing the apparatus employed 
in quadruplex telegraphy. 

Quadruplex Telegraphy .—A system for 
the simultaneous transmission of four 
messages over a single wire, two in one 
direction, and two in the opposite direc- 
tion. 

Quadruplex Telephony.— The simulta- 
neous transmission of four telephonic 
messages, two in one direction and the re- 
maining two in the opposite direction. 

Quadruplex Transmission. — Tele- 
graphic or telephonic transmission ef- 
fected by means of a quadruplex system. 

Quadruplex Working. — Operating a 
telegraph or telephone line by quadruplex 
apparatus. 

Quadruplex Re-Entrant Armature 
Winding. — An armature provided with 
four independent conducting paths or 
windings, each of which is independently 
re-entrant. 

Qualitative Analysis. — A chemical an- 
alysis which merely ascertains the kinds 
of elementary substances present. 

Quality of Musical Sound.— (1) That 
property of a musical note which enables 
it to be distinguished from another which 
possesses the same wave length and am- 
plitude ; i. e., the same pitch and loudness. 
(2) The timbre of sound. 

Quality of Radiation.— The character of 
radiation in regard to the frequency and 
amplitude of the vibration it contains. 

Quantitative Analysis.— Chemical an- 
alysis which ascertains the different pro- 
portions in which the component sub- 
stances enter into a compound substance. 

Quantity Armature. — An old term for an 
armature wound with a few coils and of 
comparatively low resistance. 

Quantity Connection for Condensers. 
A term formerly employed for the mul- 
tiple connection of a number of con- 
densers. 

Quantity Current. — An old term for a 
current produced by a voltaic battery con- 
nected in multiple-arc. 

Quantity Efficiency of Storage Bat- 
tery. — (1) The ratio of the number of 
ampere-hours taken out of a storage bat- 



Qua.] 



895 



[Raa. 



tery to the number of ampere-hours put 
in the battery in charging it. (2) The 
ampere-hour efficiency. 

Quantity, Electric. — The amount of elec- 
tricity present in any current or charge. 

Quantity Meter, Electric— A coulomb 
meter. 

Quantity of Light.— (1) Flux of light. 
(2) The product of the luminous intensity 
and the solid angle through which it is 
emitted. 

Quantivalence. — A general term for the 
combining capacity of the elements. 

Quarter-Load Efficiency of Trans- 
former. — The efficiency of a transformer 
at quarter-load. 

Quarter-Period. — The time in which a 
vibrating body, or alternating quantity, 
completes one quarter of its cycle. 

Quarter - Phase. — The condition of di- 
phase relationship or the separation of 
two alternating quantities by a quarter 
period. 

Quarter-Phase Armature. — A polyphase 
armature which will produce quarter- 
phase currents. 

Quarter-Phase Armature-Winding. — 

Such a winding of a polyphase armature 
as will permit it to produce quarter-phase 
currents. 

Quarter-Phase Bar- Winding for Ar- 
mature. — A form of bar winding em- 
ployed in the armature of a quarter-phase 
generator. 

Quarter-Phase System. — A two-phase 
system of alternating-current distribution 
employing two currents dephased by a 
quarter period. 

Quartz Fibre. — A suspension fibre ob- 
tained by drawing a thread from a fused 
crystal of quartz. 

Quasi-Resonance. — (1) Imperfect reso- 
nance. (2) The production of resonance in 
a primary alternating-current circuit by 



the adjustment of a secondary circuit or 
circuits. 

Quega. — A prefix for a quintillion, or 10 16 . 

Quegohm. — A quintillion ohms, or a thou- 
sand million megohms. 

Quick. — To cover with an adherent film of 
mercury. 

Quick-Break. — A break of a circuit ob- 
tained by means of a quick-break switch. 

Quick-Break Switch. — A switch by 
means of which a circuit may be rapidly 
broken. 

Quickened. — A term employed in electro- 
plating for a surface which has been pro- 
vided for the reception of a deposit of 
silver by dipping the article in a quicken- 
ing liquid. 

Quickening Liquid. — A term sometimes 
applied to the quickening solution. 

Quickening Process.— A process em- 
ployed in quickening. 

Quickening Solution. — A solution of a 
salt of mercury in which objects to be 
electro-plated are dipped after cleansing, 
just before being placed in a plating 
bath. 

Quicking. — Subjecting to the quicking 
process. 

Quicking Solution.— A quickening solu- 
tion. 

Quiet Arc. — A noiseless arc. 

Quiet Commutation. — Commutation de- 
void of sparking. 

Quiet Discharge. — A name given to a 
convective discharge in order to distin- 
guish it from a noisy disruptive discharge. 

Quintuple Harmonic. — A harmonic of 
five times the frequency of the funda- 
mental. 

Quivering of Magnetic Field.— The pul- 
sation of magnetic flux either under the 
leading pole-piece of a generator, or the 
trailing pole-piece of a motor, due to the 
successive commutations of the advan- 
cing armature coils. 



R. — A contraction for ohmic resistance. 

It. — A symbol proposed for magnetic resist- 
tance or reluctance. 

r. — A symbol for radius. 

p. — A symbol for specific electric resistance 
or resistivity. 

R. M. S. Current.— (1) A term proposed 



for the square root of the mean square of 

the current. (2) The effective current. 
R. P. M. — An abbreviation for revolutions 

per minute. 
R. Q. — In submarine telegraphy, a request 

for repetition of a doubtful word, phrase, 

or sentence. 
Raad. — A name formerly given by the 

Arabians to the torpedo or electric ray. 



Eae.J 



896 



[Rad. 



Raceway. — A continuous space provided 
in a conduit for the insertion or removal 
of a conductor or conductors. 

Racing of Dynamo. — A general term for 
any excessive speed produced in a dynamo- 
electric machine by the sudden removal of 
its load, as by the breaking of a belt. 

Racing of Motor. — An increase in the 
speed of an electric motor when the load 
is suddenly removed. 

Rack-Rail-Incline Electric Railway.— 
A means adopted for the passage of a 
trolley or other car over a steep grade by 
the use of a rack rail to be operated by 
the ordinary incline system where the 
line is too long. 

Racking of Armature Conductors.— A 
term sometimes applied to a sudden drag 
exerted on the armature conductors of a 
dynamo or motor during operation. 

Rad. — (1) A unit quantity of time-flux of 
light. (2) A lumen-second or one lumen, 
maintained during one second. (3) A 
name proposed for the lumen-second. 

Radial Armature. — A term sometimes 
used for pole armature. 

Radial Current.— A term proposed for a 
current which radiates from a centre. 

Radial Photometer. — A photometer 
whose bench is movable about a vertical 
axis, so as to be readily turned into any 
azimuth, and employed to determine the 
intensity of the light emitted by a lum- 
inous source in various directions. 

Radial Truck. — A triple-truck support for 
a car-body, in which the car is supported 
on the centres of the end trucks in such a 
manner that they may swivel freely, 
carrying the middle truck between them. 

Radially-Laminated Armature. — An 
armature core whose iron consists of thin 
discs suitably supported on the shaft. 

Radian. — (1) A unit angle. (2) An angle 
whose circular arc is equal in length to 
its radius ; or. approximately, 57° 17' 45". 

Radian-per-Second.— A unit of angular 
velocity of a rotating body. 

Radiant Efficiency.— The ratio of the 
light-giving radiation to the total radia- 
tion. 

Radiant Energy. — Energy transferred or 
charged on the universal ether. 

Radiant Matter.— (1) That condition of 
the gaseous matter that constitutes the 
residual atmosphere of high vacua. (2) 
Ultra-gaseous matter. 

Radiant Vector. — A vector point-func- 
tion which represents the rate and direc- 



tion at and in which energy is being trans- 
ferred in space. 

Radiophonic Transmission.— (1) Trans- 
mission by means of a photophone. (2) 
Transmission of articulate speech along 
rays of light. 

Radiate. — (1) To transfer energy by means 
of waves. (2) To issue radially, or by 
rectilinear divergence, from a common 
centre. 

Radiating. — (1) Transferring energy by 
means of waves. (2) Issuing radially. 

Radiation. — (1) A transference of energy 
by means of waves. (2) Issuing radially 
from a common centre. 

Radiation Constant. — The amount of 
heat lost by radiation in unit time when 
the temperature of the radiating body is 
one degree of the thermometric scale 
above that of the surrounding air. 

Radiation, Electric— (1) The transfer- 
ence of electric energy by means of elec- 
tro-magnetic waves set up in the surround- 
ing ether. (2) That property of a rapidly 
oscillating or alternating-current circuit 
by virtue of which energy is expended 
by the circuit in the form of electro-mag- 
netic waves. 

Radiation Meter. — (1) An instrument 
for measuring radiation. (2) A meter 
employed for the measurement of the 
radiation emitted by an electric oscilla- 
tion, whose operation is dependent on the 
elongation produced in a stretched wire 
by the heat developed therein by cur- 
rents induced by the rapidly oscillating 
field of force- 
Radiation of Electricity .—The radiation 
of electric energy by means of electro- 
magnetic waves. 

Radiation of Magnetic Flux.— (1) The 
passage of magnetic flux out of the north- 
seeking pole of a magnet or solenoid. (2) 
The issue of magnetic flux from a mag- 
netic pole in approximately radial paths. 

Radiator, Electric. — (1) An electric 
heater so placed as to radiate its heat into 
a room or other space to be heated. (2) An 
electric circuit which radiates or produces 
electro-magnetic oscillations or waves. 

Radicals. — (1) Unsaturated atoms or groups 
of atoms, in which one or more of the 
bonds are left open or free. (2) Ions. 

Radiograph. — The word now generally 
employed for a picture taken by means of 
X-rays. 

Radiography.— (1) The process of taking- 
radiographs, or X-ray pictures. (2) X-ray 
photography. 



Bad.] 



[Rat. 



Radiometer. — (1) A word frequently em- 
ployed for the Crookes radiometer. (2) 
An instrument in which the rotation of 
a light set of vanes is produced in an 
ultragaseous space, by radiant energy. 

Radio-Micrometer.— An electric appara- 
tus for measuring the intensity of radiant 
heat. 

Radiophone. — A name sometimes given 
to a photophone. 

Radiophonic. — Of or pertaining to the 
radiophone. 

Radiophonic Sounds. — Sounds resulting 
from the direct action of radiation on cer- 
tain bodies. 

Radiophony. — The production of sound 
by a body capable of absorbing radiant 
energy, when an intermittent beam of 
heat or light falls on it. 

Radius of G-yration.— In a rotating body, 
a radial distance from the centre of rota- 
tion at which, if the entire mass of the 
body were collected, its moment of inertia 
would remain the same. 

Rail-Bond, Electric. — Any device where- 
by the ends of contiguous rails are placed 
in good electrical contact with one 
another, so that the resistance of the rails. 
employed as a portion of the return- 
circuit, may be as small as possible. 

Rail Bonding. — Connecting rails by elec- 
tric bonds, for the purpose of effecting in- 
timate electric contact between them. 

Rail Joint. — A rail bond. 

Railroad, Electric. — A railroad or rail- 
way on which the cars are driven or pro- 
pelled by means of electric motors placed 
on the cars, or on locomotives. 

Railroad Switchboard. — A switchboard 
employed in a railroad power-house, to 
which the generator and feeder terminals 
are attached. 

Railway Circuit. — A circuit for operating 
an electric railway. 

Railway Current-Controller. — (1) A 
term formerly given to a form of switch- 
board employed for controlling the output 
of an electric power-house. (2) A rail- 
road motor-controller for starting and 
stopping the cars, and for varying their 
speed. 

Railway, Electric. — An electric railroad. 

Railway Generator. — A dynamo-electric 
machine which develops the current em- 
ployed in systems of electric railways. 

Railway Line-Crossing.— (1) Means pro- 
vided for supporting the separate trolley 
wires at places where two or more wires 
cross one another. ffS\ A trolley crossing. 

57 



Railway Line-Section. — One of the in- 
dependent divisions into which the trolley 
wire and its feeder system are divided by 
means of section insulators, for the pur- 
pose of preventing an accidental ground 
at one point from interrupting the traffic 
over a considerable portion of the road. 

Railway Motor. — An electric motor em- 
ployed for the propulsion of an electric 
street or trolley car. 

Railway Power-Generator. — A term 
sometimes used for railway generator. 

Railway Return Circuit.— (1) A term 
frequently employed for the ground-re- 
turn of a trolley system. (2) The return 
circuit, generally a grounded circuit, em- 
ployed in trolley systems. 

Railway Return-Wire.— (1) A copper 
wire employed for the purpose of aiding 
and re-inforcing the ground-return, so as 
to decrease the wasteful expenditure of en- 
ergy due to the poor quality of the rail 
and track, with its numerous joints, as a 
conductor. (2) A term sometimes em- 
ployed for a railway return-circuit. 

Railway Section-Insulators. —Insulators 
employed for the purpose of dividing the 
trolley wire or line into a number of inde- 
pendent sections. 

Railway Turn-Out.— (1) In a single-track 
road, an extra track provided to permit 
the passage of a car in the opposite direc- 
tion. (2) A local section of track into 
which a car can be run, so as to leave the 
main line clear. 

Range Finder, Electric— Fiske's electric 
range finder. 

Range Indicating System.— On war- 
ships a telegraphic indicating-system for 
announcing, at any or all of the guns, the 
range or distance of the target as signalled 
from the range finder. 

Ratchet -Pendant Argand Electric 
Gas-Burner.— A ratchet-pendant electric 
burner adapted for lighting an Argand 
gas burner. 

Ratchet-Pendant Electric Gas-Burner. 
A gas burner in which one pull on a 
pendant turns on the gas and ignites it by 
means of an electric spark from a spark 
coil, and the next pull turns it off. 

Ratchet - Pendant Electric ■ Candle 
Burner. — A pendant for both lighting 
and extinguishing a candle gas-jet. 

Rate-of-Doing-Work.— (1) Activity. (2) 
Power. 

Rated Candle - Power. — A nominal 
candle-power. 

Ratio Arms of Bridge.— A name some- 



Rat.] 



898 



[Rea, 



times given to the proportionate arms of 
a bridge. 

Ratio of Conversion. — A term sometimes 
employed instead of ratio of transforma- 
tion. 

Ratio of Transformation.— The ratio be- 
tween the electromotive force produced 
at the secondary terminals of an induc- 
tion coil, or transformer, and the electro- 
motive force impressed on the primary 
terminals. 

Ray. — (1) A term sometimes employed for 
a single line of light or other form of radi- 
ant energy, as distinguished from a pen- 
cil of rays or a beam. (2) A line of radiant 
energy flux. 

Ray, Electric. — (1) A species of fish 
which possesses the power of producing 
electricity. (2) A single line of electric 
flux-energy. 

Rayleigh's Current- Weigher.— A form 
of electro-dynamometer balance. 

Rayleigh's Form of Clark's Standard 
Voltaic Cell. — A modified form of 
Clark's standard voltaic cell. 

Reactance. — (1) The inductance of a coil 
or circuit multiplied by the angular ve- 
locity of the sinusoidal current passing 
through it. (2) A quantity whose square 
added to the square of the resistance 
gives the square of the impedance, in 
a simple-harmonic current circuit. 

Reactance Factor.— The ratio of the re- 
actance of a coil, conductor, or circuit, 
to its ohmic resistance. 

Reactance of Condenser. — (1) The recip- 
rocal of the product of the capacity of a 
condenser, and the angular velocity of 
the simple-harmonic pressure with which 
it may be connected. (2) A quantity 
which divided into the alternating-cur- 
rent pressure at condenser terminals, 
gives the current strength in the con- 
denser. 

Reactance of Mutual Inductance.— In 
an alternating-current circuit, the prod- 
uct of a mutual inductance and the an- 
gular velocity. 

Reacting Inductive Electromotive 
Force of Primary Circuit.— (1) The C. 
E. M. F. of self-induction in a primary 
alternating-current circuit. (2) The C. 

E. M. F. of mutual-induction in a primary 
alternating-current circuit, or the C. E. M. 

F. due to current in the secondary circuit. 
Reaction. — In electro-therapeutics, mus- 
cular contractions following the closing 
or opening of an electric circuit through 
the nerves or muscles. 

Reaction Coil.— (1) A magnetizing coil 



' surrounded by a conducting covering or 
sheathing which opposes the passage of 
rapidly alternating currents less when 
directly over the magnetizing coil than 
when a short distance from it. (2) A 
choking coil. 

Reaction Machine. — An induction ma- 
chine. 

Reaction Motor. — An induction motor. 

Reaction of Degeneration. — An altera- 
tion in the behavior of nerves and muscles 
under electric stimulation, due to disease. 

Reaction of Exhaustion.— A condition 
of nervous or muscular irritability to 
electric excitation, when a certain reac- 
tion produced by a given current strength 
cannot be reproduced without an increase 
in current strength. 

Reaction Principle of Dynamo-Elec- 
tric Machine. — The mutual interaction 
between the current generated in the 
armature coils and the field coils of a con- 
tinuous-current dynamo-electric machine, 
each strengthening the other until the 
full-working current which the machine 
is capable of developing is produced. 

Reaction Telephone.— An electro-mag- 
netic telephone in which the currents in- 
duced in a coil of fine wire attached to 
the diaphragm are passed through the 
coils of an electro-magnet, each thus re- 
acting on and strengthening the other. 

Reaction Time.— The time required for 
the effects of an electric current to pass 
from a nerve to a muscle. 

Reaction-Wheel, Electric. — A wheel 
driven by the reaction of a convective 
discharge. 

Reactive Circuit. — A circuit containing 
either inductance or capacity alone, or 
both inductance and capacity. 

Reactive Coil. — A reaction coil. 

Reactive Drop. — The drop in a circuit or 
conductor due to its reactance, as dis- 
tinguished from the drop due to its ohmic 
resistance. 

Reactive Effect. —The choking effect of 
reactance in an alternating-current cir- 
cuit. 

Reactive Electromotive Force.— In an 
alternating-current circuit, that com- 
ponent of the electromotive force that is 
in quadrature with the current and is 
employed in balancing the C. E. M. F. of 
inductance. 

Reading Microscope.— A form of micro- 
scope employed for the measurement of 
very small distances. 

Reading Telescope. — A telescope em- 



Rea.] 



899 



[Rec. 



ployed in electric measurements for read- 
ing the deflections of a galvanometer. 
Real Cable. — In duplex submarine cable- 
telegraphy the actual cable, as distin- 
guished from the artificial cable. 

Real Efficiency of Storage Battery.— 
(1) The ratio of the number of watt-hours 
taken out of a storage battery to the 
number of watt-hours put into the bat- 
tery in charging it. (2) The energy effi- 
ciency, or watt-hour efficiency, of a stor- 
age battery, as distinguished from its 
quantity efficiency, or ampere-hour effi- 
ciency. 

Real Hall Effect. — A transverse electro- 
motive force produced by magnetic flux 
through conductors conveying electric 
currents in a manner somewhat similar 
to that iu which the Faraday effect is 
produced. 

Real Image. — (1) An image formed by 
rays of light that actually meet in the 
various visible points, as distinguished 
from a virtual image. (2) An image 
which is capable of being received on a 
screen. 

Rebabbitting. — The operation of replac- 
ing the Babbitt metal in the b earings of 
a machine. 

Recalescence. — A property possessed by 
a bar or a mass of cooling incandescent 
steel, of again becoming incandescent 
after having cooled sufficiently to no 
longer emit luminous heat. 

Recalibration. — A new calibration of an 
instrument. 

Received Current. — A term used in teleg- 
raphy to distinguish the currents that 
come in over a line from a distant station, 
from those that are sent out to a distant 
station . 

Receiver. — A name sometimes given to a 
receiving instrument of a gramophone, 
graphophone, telephone, or telegraph in- 
strument. 

Receiver Magnet. — A receiving magnet. 

Receiving End of Line. — That end of a 
line at which the currents arrive, as dis- 
tinguished from the end at which they 
are sent out. 

Receiving Leg of Telegraphic Loop. 
The wire of a telegraphic loop upon 
which messages are received, as distin- 
guished from the sending leg. 

Receiving Magnet.— (1) A name some- 
times given to the relay of a telegraphic 
system. (2) In general, any magnet used 
directly in the receiving apparatus at the 
receiving end of a telegraph or telephone 
line. 



Receiving Signaller. — (1) A receiving 
operator. (2) An operator engaged in re- 
ceiving a telegraphic message. 

Receiving Transformer.— A transformer 
at the receiving end of a circuit. 

Receptacle. — In incandescent lighting a 
permanent device for receiving an at- 
tachment plug. 

Receptive Device.— (1) A translating de- 
vice. (2) In electrotechnics, a magneto- 
or electro-receptive device. (3) A device 
for receiving energy and utilizing or 
transforming it. 

Reciprocal. — The quotient arising from 
dividing an}- quantity into unity. 

Reciprocating Motor. — A motor with a 
reciprocating action, or with a motion 
alternately in opposite directions, as dis- 
tinguished from a rotary motor. 

Reciprocal Vectors.— Two vectors whose 
product is equal to the numeric unity. 

Recoil Circuit.— A term sometimes ap- 
plied to the circuit that lies in the alter- 
native path of a discharge. 

Recoil Kick of Disruptive Discharge. 

A kick or reaction produced by a disrup- 
tive discharge. 
Recorder. — A word sometimes used for 

either a telegraphic recorder, or a siphon 

recorder. 
Recorder Ammeter. — An ammeter whose 

indications are permanently recorded. 
Recorder Battery. — The local battery 

supplying the magnets, or mouse-mill, of 

a siphon recorder. 

Recorder Circuit. — The circuit of a 
siphon recorder. 

Recorder Coil. — The receiving coil of a 
siphon recorder. 

Recorder Magnets. — The magnets which 
supply the magnetic flux in which moves 
the receiving coil of a siphon recorder. 

Recorder Shunt. — A shunt of low resist- 
ance placed across the terminals of the 
coil of a siphon-recorder during sending. 

Recorder Signals.— Signals received on a 
siphon recorder by the projection of ink 
upon a movingstripof paper from a small 
glass siphon connected with the receiving 
coil. 

Recorder Slip. — The strip of paper re- 
cording, or prepared for recording, siphon- 
recorder signals. 

Recorder Switch. — The switch employed 
in connection with a siphon recorder for 
changing from sending to receiving con- 
nections. 

Recorder - Vibrator. — An electronic- 



Rec] 



900 



[Red 



chanical vibrator for forcing an inter- 
mittent flow of ink from the siphon of a 
recorder on to a band of paper moving 
beneath it. 

Recording Compass. — A compass so ar- 
ranged as to record the directions of 
the needle, and to sound an alarm in case 
the course of the vessel deviates any pre- 
determined number of degrees. 

Recording Drum. — A cylindrical drum 
covered by a sheet or strip of paper on 
which a chronographic or other record is 
made. 

Recording Meter. — Any form of electric 
meter that records its indications. 

Recording Voltmeter. — A voltmeter 
whose indications are permanently re- 
corded. 

Recording Wattmeter. — (1) A recording- 
form of wattmeter. (2) A dial watt-hour 
or kilowatt-hour meter. 

"Recovery" of Condenser. — The con- 
dition of a condenser whose dielectric has 
regained its neutral condition after having 
been strained by a charge. 

Rectal Electrode. — An electrode suita- 
ble for the treatment of the rectum. 

Rectangular Curve. — A curve whose out- 
line approximates or conforms to a rec- 
tangular siiape. 

Rectangular Type of Periodically Al- 
ternating Electromotive Force. — An 
electromotive force whose variations of 
strength are represented by a curve of 
rectangular outline. 

Rectangular Variation - Diagram.— A 
diagram drawn to rectangular co-ordi- 
nates, and representing the variation of 
any quantity or quantities. 

Rectification of Alcohol, Electric— A 

process whereby the bad taste and odor 
of alcohol, due to the presence of alde- 
hydes, are removed by the electrical con- 
version of the aldehydes into true alcohol 
through the addition of hydrogen atoms. 

Rectified. — Commuted, or caused to take 
one and the same direction. 

Rectified Currents. — Commuted cur- 
rents. 

Rectifier. — A name sometimes given to a 
commutator. 

Rectilinear Co-Ordinates. — Co-ordi- 
nates measured from two rectilinear axes 
intersecting in the plane of delineation 
at a point called the origin. 

Rectilinear Current. — A current flowing 
through a straight or rectilinear portion 
of a circuit. 



Rectifying Commutator.— A term some- 
times applied to a commutator which 
commutes alternating into direct cur- 
rents. 

Red Candle. — A photometric candle em- 
ployed in connection with a red glass 
screen, for the purpose of enabling the 
unpracticed eye to more readily compare 
it with the source whose intensity is to be 
measured. 

Red Heat. — The temperature at which a 
body begins to glow or to emit red rays 
of light. 

Red Hot. — Possessing the temperature of 
red heat. 

"Red" Magnetism.— A name formerly 
applied to the magnetism at the north 
pole of a magnet, as distinguished from 
the so-called ''blue" magnetism at the 
south pole. 

Redressed. — A word sometimes employed 
for commuted. 

Redressed Currents. — Commuted cur- 
rents. 

Reduced Battery. — A portion only of a 
main-line battery employed in quadruplex 
telegraphy. 

Reduced Deflection Method. — A 
method of measuring electromotive force, 
resistance or current, by determinations 
based upon an observed reduction in 
current strength, and resulting deflection 
of a galvanometer in the circuit. 

Reducing Clamp for Underground 
Tubing. — A clamp at a coupling box 
clasping an underground tube, of such 
dimensions as to permit of a change in 
the diameter of the next succeeding tube. 

Reducing Coupling. — A flexible coupling 
connecting two conductors of different 
diameters. 

Reducing Switch.— A switch so con- 
nected with a circuit as to bring a reduced 
or lowered pressure upon a sub-circuit. 

Reducteur Resistance for Volt-Meter. 

(1) A coil of known resistance as com- 
pared with the resistance of the coils of 
a voltmeter, that is connected with them 
in series for the purpose of increasing the 
range of the instrument. (2) A multi- 
plying coil, or multiplier of a voltmeter. 

Reducteur Shunt for Ammeter. — (1) 
A shunt coil connected in multiple with 
the coils of an ammeter for the purpose 
of changing the value of its readings. 

(2) A multiplier. 

Reduction Eactor of Galvanometer.— 

The ratio between the horizontal inten- 
sity of the field of a galvanometer and 
the galvanometer constant. 



Red.] 



901 



[Reg. 



Reduction Gear.— Gear employed on a 
street-car for suitably reducing the speed 
of the car below that of the motor which 
drives it. 

Reed Interrupter. — A form of automatic 
make-and-break contact, operated by the 
vibrations of a reed. 

Reel Insulator. — An insulator resembling 
a reel in shape, and suitable for use in 
connection with an engine plane signal 
system. 

Re-Enforcement of Sound. — An increase 
in the intensity of sound by the use of 
sounding boards, resonators, or reflectors. 

Re-Entrancy.— The intersection of a curve 
by itself. 

Re-Entrancy of Armature Winding. — 
The condition or property of an armature 
winding, by virtue of which the conduct- 
ing path through the armature repeats 
itself or re-enters itself. 

Re-Entrant Armature- Windings.— Ar- 
mature windings, which, when followed 
in either direction, lead back to the start- 
ing point. 

Refining, Electric. — The refining of 
metals by the application of electrolysis. 

Reflect. — To throw off from a surface ac- 
cording to the laws of reflection, as of 
waves in an elastic medium. 

Reflecting. — Throwing off from a surface 
in accordance with the laws of reflection. 

Reflecting Galvanometer. — A term 
sometimes applied to a mirror galvano- 
meter. 

Reflection. — The throwing back of abod}- 
or wave from a surface at an angle equal 
to that at which it strikes the surface. 

Reflection of Electro-Magnetic Waves. 
The reflection of electro-magnetic 
waves that occurs from the surfaces of 
certain substances placed in the path of 
the waves. 

Reflector.— A reflecting surface suitably 
shaped to reflect rays of light in any de- 
sired direction. 

Reflector Bracket. — A bracket for sup- 
porting two insulators and for holding 
the support of a street lamp, with or with- 
out a reflector. 

Reflector Search-Light. — A search-light 
consisting of a focussing lamp placed at 
the focus of a suitable reflector. 

Reflector Shade.— A shade surrounding 
an arc-lamp, a portion of whose surface 
is covered with reflecting material. 

Refract. — To change the direction of 
waves in any elastic media in accordance 
with the laws of refraction. 



Refracting. — Changing the direction of 
waves in elastic media in accordance 
with the laws of refraction. 

Refraction.— The bending of a ray of light, 
heat, or electro-magnetism, at the inter- 
face of any two transparent media, whose 
elasticity and density differ. 

Refractive Energy.— A value equal to the 
index of refraction minus unity. 

Refractory. — (1) Possessing the power of 
resisting fusion by heat. (2) 'Fusible only 
at extraordinarily high temperatures. 

Refreshing Action of Current.— The 
restoration, after fatigue, of muscular 
and nervous excitability obtained by the 
action of voltaic alternatives. 

Regenerable Cell.— A regenerative cell. 

Regenerated Cell.— A cell which has had 
its ability for producing current restored 
by a charging process. 

Regenerative Armature.— A word pro- 
posed for the armature of a dynamo that 
is capable of producing its own magnetic 
field-flux, when commuted with a back- 
ward lead. 

Regenerative Cell.— (1) A name some- 
times given to an early form of of storage 
cell. (2) Any cell which can have its 
energy restored by the action of a charg- 
ing current. 

Regional Magnetic Disturbances. — A 
term proposed for magnetic disturbances 
that are apparently confined to limited 
regions of the earth's surface. 

Register. — A word frequently employed 
for any registering apparatus. 

Registering Apparatus, Electric— De- 
vices for obtaining permanent records by 
electrical means. 

Registering Declination-Magnetome- 
ter. — A magnetometer employed for au- 
tomatically registering the magnetic de- 
clination. 

Registering Electrometer.— An electro- 
meter whose indications are automatically 
registered. 

Registering Photometer.— (1) A photo- 
meter which registers not the photometric 
but the actinic or chemica 1 action of light. 
(2) A recording photometer. 

Regulating Box.— (1) A rheostat inserted 
in the field circuit of a generator or 
motor for regulating the current passing 
through the field-magnet coils. (2) A 
rheostat. 

Regulating Cell for Storage Battery. — 
A counter-electromotive force cell. 

Regulating Lamp-Socket.-(l) A lamp 
socket containing a device controlled by 



Beg.] 



902 



[Rem, 



a key or switch for regulating the degree 
of incandescence of the filament. (2) A 
general term for any form of lamp socket 
which will permit the light to be econo- 
mically turned down or lowered in in- 
tensity. 

Regulating Wires.— Adjusting the ten- 
sion of overhead line wires. 

Regulation of Dynamo.— Such an ad- 
justment of a dynamo as will preserve 
constant either its current or its pres- 
sure. 

Regulation of Motor. — Such an adjust- 
ment of a motor as will preserve constant 
its speed, or its torque, or both. 

Regulator for Dynamo. — Any device by 
means of which the regulation of a dy- 
namo is effected. 

Regulator for Motor.— Any device by 
means of which the regulation of a motor 
is effected. 

Regulator Magnet.— (1) A magnet whose 
function is to automatically effect any 
desired regulation. (2) In a system of 
automatic constant-current dynamo-reg- 
ulation, the magnet by the movements of 
whose armature the commutator brushes 
are automatically shifted to such posi- 
tions on the commutator as will main- 
tain the current practically constant, 
despite changes in the resistance of the 
circuit external to the machine. 

Reguline Electro-Metallurgical De- 
posit. — A flexible, adherent and strongly 
coherent film of electrolytically deposited 
metal. 

Rejuvenation of Luminescence. — Re- 
imparting, by exposure to light or other 
suitable means, the power of lumines- 
cence to a substance after it has lost this 
power. 

Relative Inductivity.— The ratio of the 
inductivity of a medium to the induc- 
tivity of vacuum. 

Relative Permittivity.— The ratio of the 
permittivity of a medium to the permit- 
tivity of vacuum. 

Relaxation Distance. — The distance in 
which an electro-magnetic wave travel- 
ling along the surface of a conductor, 
diminishes in amplitude in a ratio whose 
Naperian logarithm is unity. 

Relaxation Time. — The time during 
which a logarithmically diminishing 
quantity diminishes in a ratio whose Na- 
perian logarithm is unity. 

Relay. — In telegraphy, an electro-magnet 
provided with contact points placed on a 
delicately supported armature, the move- 



ments of which open or close a local re- 
ceiver circuit. 

Relay Bell. — An electric bell in which a 
relay magnet is employed to switch a 
local battery into the circuit of the bell. 

Relay Contact.— (1) A term frequently 
applied to a form of electro-magnetic in- 
strument by means of which a local cir- 
cuit is completed on the passage of a cur- 
rent. (2) The contact point of a relay. 

Relay Magnet.— (1) A term sometimes 
given to a relay. (2) The permanent 
magnet of a polarized relay. (3) The 
electro-magnet of a relay. 

Relief Lamp. — (1) An incandescent lamp 
whose socket is provided with a spring 
cut-out, so arranged that on the breaking 
of the lamp the circuit is automatically 
closed. (2) An incandescent lamp held in 
reserve for insertion in a series system to 
take the place of a lamp that has been 
cut out. 

Relief Operators. — In telegraphy or tele- 
phony, operators coming on duty to re- 
lieve the operators at work. 

Relief Photometer.— The name given to 
a class of photometers in which the two 
divisions of the screen are not placed in 
the same plane but at right angles to each 
other, the quality of the illumination 
being readily determined since the whole 
screen then appears as a single plane il- 
lumined surface, in which the edge of a 
dihedral angle of the screen is no longer 
perceptible. 

Relievo. — (1) The opposite of intaglio. (2) 
A stone, electro, or other solid body, in 
which a figure is so represented that its 
outlines project or stand out from the 
surface. 

Reluctance. — (1) A term applied to mag- 
netic resistance. (2) In a magnetic cir- 
cuit the ratio of the M. M. F. to the total 
magnetic flux. 

Reluctancy. — A term proposed for re- 
luctivity. 

Reluctivity — The specific magnetic re- 
sistance of a medium. 

Reluctivity Constants. — The constants 
which, when applied according to a form- 
ula to the magnetic force or magnetic 
flux density in iron or steel, give the re- 
luctivity of the iron or steel. 

Remaining Sockets. — The sockets of a 
multiple telephone switchboard in circuit 
with any particular socket. 

Remanence. — (1) Magnetic retentivity. 
(2) The property of magnetic substances 
to retain part of their magnetism owing 
to hysteresis. (3) The magnetic flux 



Rem. 



903 



[Bes. 



density in a magnetic substance when 
the magnetic force is reduced to zero. 

Remanent Flux. — Remanent magnetism. 

Remanent Magnetism.— A phrase some- 
times used in place of residual mag- 
netism. 

Remanent Polarization. — (1) A term 
proposed to describe the condition' of a 
voltameter when a certain number of 
discharges having traversed it, all in the 
same direction, and a series of discharges 
exactly equal to the preceding have been 
established in the opposite direction, the 
currents of polarization are less in- 
tense in the second than in the first. (2) 
Residual polarization of immersed elec- 
trodes after a passage of the current. 

Removable Key-Switch. — A plug 
switch. 

Removable Pole-Step. — A pole step cap- 
able of being inserted into and removed 
from a socket for the equipment of a line- 
man, to enable a lineman to reach the 
permanent steps. 

Renovation of Secondary or Storage 
Cell. — The recharging of a run-down or 
discharged storage cell. 

Renter. — A term sometimes used for sub- 
scriber. 

Reofore. — A rheophore. 

Repair-Wagon for Trolley Line.— A 
wagon provided with a tower or telescopic 
support employed for the repair of trolley 
lines. 

Repeater. — The name sometimes given to 
a telegraphic repeater, or translator. 

Repeating Relay.— (1) A relay employed 
in a repeater. (2) The relay in a tele- 
graph circuit which repeats the signals 
into another circuit. 

Repeating Sounder. — A telegraphic 
sounder which repeats a telegraphic 
despatch into another circuit. 

Repeating Telegraphic Station.— A 
station situated at some intermediate 
point on a long telegraphic line which is 
divided into sections, where the currents 
received on one section are passed 
through a repeater by means of which 
they are sent on or repeated into the other 
section. 

Repeating Telephone Coil.— An induc- 
tion coil provided with two windings, 
usually of an equal number of turns, each 
winding being connected to a telephone 
circuit, so that the two circuits are placed 
in intimate inductive association. 

Replenisher. — A static influence machine 
employed for charging a quadrant elec- 
trometer or other electrostatic device. 



Repulsion, Electric— The mutual driv- 
ing apart, or tendency to mutually drive 
apart, which exists between two similarly 
charged bodies, or between two similar 
electric charges. 

Repulsion Electrometer. — An electro- 
meter in which the differences of poten- 
tial are measured by means of the repul- 
sion existing between two similarly 
charged bodies. 

Repulsion Motor.— (1) An electric motor 
deriving its power from the repulsion be- 
tween electric charges. (2) An alternat- 
ing-current motor deriving its power 
from the repulsion between electric cur- 
rents. (3) An alternating-current motor 
in which the armature is provided with 
temporarily short-circuited windings by 
means of a commutator and brushes. 

Reserve-Cell Switch. — A switch em- 
ployed in a storage-battery installation 
for the purpose of maintaining the pres- 
sure of discharge by introducing reserve 
cells into the circuit. 

Residual Atmosphere. — The traces of 
air or other gas remaining in a space 
which has been nearly exhausted of its 
gaseous contents by a pump or other 
means. 

Residual Charge. — The charge remain- 
ing in a Leyden jar after it has been dis- 
ruptively discharged. 

Residual Flux. — Residual magnetic 
flux. 

Residual Magnetic-Flux.— (1) Rema- 
nence. (2) Magnetic flux remaining in a 
magnetic circuit by virtue of hysteresis 
after the withdrawal of the magnetizing 
force. 

Residual Magnetism.— (1) The magnet- 
ism remaining in a core of an electro- 
magnet on the opening of the magnetiz- 
ing circuit. (2) The small amount of 
magnetism retained by soft iron when re- 
moved from any magnetic flux. 

Residue, Electric. — A term proposed for 
residual charge. 

Resilience. — (1) A word sometimes em- 
ployed for elasticity. (2) The work done 
in deforming a bar up to the elastic 
limit. 

Resin. — A general term applied to a 
variety of dried juices of vegetable 
origin. 

Resinous Electricity.— A term formerly 
employed in place of negative electri- 
city. 

Resinous Electrification. — A name for- 
merly applied to an electrification pro- 
duced in resin by its friction. 



Res.] 



904 



[Res. 



Resistance. — (1) A word sometimes used 
for electric resistance. (2) Obstruction 
to flow. (3) Obstruction to force. 

Resistance Balance. — A duplex or quad- 
ruplex balance adjusted for the resistance 
of a line by means of a rheostat. 

Resistance Balance of Duplex System. 

(1) A balance obtained in a duplex system 
by inserting in the artificial line a resist- 
ance corresponding to that of the sum 
of the resistances of the main-line wire, 
the distant relays, and the distant battery. 

(2) A balance of resistance in duplex tele- 
graphy as opposed to a balance of capac- 
ity. 

Resistance Board. — A general term for a 
board on which resistances are so placed 
as to be capable of ready adjustment, con- 
nection, introduction, or removal from a 
circuit. 

Resistance Box. — A term employed for a 
box containing graduated resistance coils. 

Resistance Bridge.— A name frequently 
employed for a Wheatstone's resistance 
balance. 

Resistance Bridge-Box. — A box form of 
Wheatstone's bridge. 

Resistance Coefficient. — The resistance 
factor. 

Resistance Coil. — (1) A coil of wire, strip, 
or conductor, possessing electric resist- 
ance. (2) A coil of wire, of known elec- 
tric resistance, employed for measuring 
an unknown electric resistance. 

Resistance Column. — A name given to a 
particular form of resistance coil or 
rheostat. 

Resistance Conductivity.— The resist- 
ance offered by a substance to electric 
conduction, or to the passage of electricity 
through its mass. 

Resistance, Electric— (1) The ratio be- 
tween the electromotive force of a circuit 
and the current that passes therein. (2) 
The reciprocal of electric conductance. 

Resistance Factor. — The coefficient of 
frictional resistance to the movements of 
a suspended or oscillatory system. 

Resistance Losses. — (1) Losses in any 
system for the transmission or the trans- 
ference of energy occasioned by friction. 
(2) Losses in an electrical distribution 
system due to resistance. 

Resistance of Human Body, Electric. 
The ohmic resistance which the human 
body offers to the passage of an electric 
discharge or current. 

Resistance of Human Skin, Electric. 
The ohmic resistance of the skin. 



Resistance of Liquid, Electric— The 
ohmic resistance of a mass of liquid. 

Resistance of Telegraphic Leak. — The 
resistance offered by a leak in a tele- 
graphic line or circuit. 

Resistance of Voltaic Arc. — Eesistance 
offered by a voltaic arc to the passage of 
a current. 

Resistance Slide. — (1) A rheostat in which 
the separate resistances or coils are placed 
in or removed from a circuit by means of 
a sliding contact or key. (2) Apparatus 
employed in telegraphy for charging a 
conductor to a given fraction of the max- 
imum potential of a battery, so as to adjust 
its charge in order to balance the vary- 
ing charge of the cable. (3) A set of coils 
by which a potential difference applied to 
the terminals is virtually divided into 
10,000 parts, so that any ratio may be in- 
stantly selected. 

Resistance Thermometer, Electric— A 
thermometer whose indications are based 
on the change in the electric resistance of 
a metallic substance with changes of 
temperature. 

Resistance to Shearing. — The quotient 
of the shearing stress by the shear pro- 
duced. 

Resistants. — Bodies possessing the power 
of resistance. 

Resister. — A name sometimes given to a 
float or buoy connected with a cable while 
it is being paid out, in order to diminish 
the risk of injury from tension. 

Resisting Torque.— (1) The torque which 
it is necessary to give to a motor in order 
to enable it to move. (2) The torque of 
retarding or opposing forces. 

Resistive. — (1) Possessing the property of 
resistance. (2) Offering resistance. 

Resistivity. — (1) The specific resistance of 
a substance referred to the resistance of 
a cube of unit volume. (2) Specific re- 
sistance, or the inverse of specific con- 
ductivity. (3) A quantity in the C. G. S. 
electro-magnetic system represented di- 
mensionally in square centimetres per 
second. 

Resolution of Force.— The separation of 
a single force acting with a given inten- 
sity in a given direction, into a number of 
separate forces acting in other directions. 

Resonance. — (1) In a simple-harmonic cur- 
rent, circuit, or branch, containing botii 
inductance and capacity, the neutraliza- 
tion or annulment of inductance-reactance 
by capacity-reactance, whereby the imped- 
ance of the circuit or branch is reduced to 
the ohmic resistance. (2) In an alternat- 



Res.] 



005 



[Ret, 



ing-current circuit, or branch, containing 
localized inductance and capacity, the re- 
enforcement of condenser pressure, in- 
ductance pressure, or current strength, 
due to the mutual neutralization or oppo- 
sition of inductance and capacity-react- 
ances. (3) In an alternating-current 
circuit, or branch, the attunement of a 
circuit containing a condenser to the same 
natural undamped frequency of oscil- 
lation as the frequency of impressed E. M. 
F. whereby the circuit responds to this 
frequency more than to any other. (4) In 
an alternating-current circuit, or branch, 
the annulment of inductance-reactance by 
capacity-reactance, whereby the imped- 
ance of the circuit or branch is not only 
reduced to its ohmic resistance, but its 
current is in phase with its impressed 
E. M. F. (5) In a secondary alternating- 
current circuit containing localized in- 
ductance and reactance, the attunement 
of the natural undamped frequency of 
oscillation to the frequency of the pres- 
sure impressed upon the primary circuit, 
whereby the secondary impedance is re- 
duced to its ohmic resistance, the second- 
ary current is a maximum for any given 
primary current strength, and the second- 
ary current is in phase with the induced 
secondary E. M. F. 
Resonant Capacity. — The capacity of a 
resonant circuit, or such a capacity as 
will render an alternating-current circuit 
resonant. 

Hesonant Circuit.— (1) A circuit whose 
dimensions are such as to bring it into 
resonance with a neighboring circuit. 
(2) A circuit containing distributed in- 
ductance and capacity, in which resonant 
effects are thereby produced. 

Hesonant Inductance. — The inductance 
of a resonant circuit, or the inductance 
which will render it resonant. 

Hesonant Rise of Potential.— A rise of 
potential in a circuit due to its resonance. 

Resonator, Electric. — (1) An open-cir- 
cuited conductor whose dimensions are 
such that electro-magnetic waves or 
pulses are propagated through it at the 
same rate as they are taking place in a 
neighboring circuit, and which, conse- 
quently, has electro-magnetic pulses set up 
sympathetically in it by resonance. (2) A 
circuit tuned to oscillate in synchronism 
with another oscillating or alternating 
circuit. 

Rest.— (1) Freedom from motion. (2) The 
condition of a body in which it maintains 
an unchanged relative position with re- 
spect to neighboring bodies. 



Restoring-Coil Battery.— In a telephone 
exchange the battery which operates the 
self-restoring annunciators. 

Restoring-Coil Circuit.— In a telephone 
switchboard, the local circuit of the coil 
of a self-restoring annunciator. 

Restored Cell. — A charged storage cell. 

Resultant. — In mechanics, a single force 
that represents in direction and intensity 
the effects of two or more separate forces. 

Resultant Fault. — The apparent position 
and magnitude of a fault in a cable due 
to the resultant of all its leakage, or faults 
compounded by the rules of parallel 
forces, or as represented by finding the 
centre of gravity of an unequally loaded 
rod. 

Resultant Induction. — The magnetic 
induction in an armature of a dynamo or 
other magnetized body which is the re- 
sultant of several components of magnetic 
induction. 

Resultant Magnetic Field.— A single 
magnetic field produced by two or more 
co-existing magnetic fields. 

Resultant Magnetic Field of Dynamo. 
The magnetic field which is the result 
of both the field due to the field magnets 
and to the current passing through the 
armature coils. 

Resultant Magnetic Pole.— A term 
sometimes employed for a consequent 
pole. 

Resultant Reactance.— The total react- 
ance in a circuit or conductor. 

Resuscitating Power of Secondary or 
Storage Cell. — The ability possessed by 
a storage cell to regain its normal condi- 
tion under the influence of the charging 
current. 

Retardance. — In a telephone circuit, a 
quantity alleged to represent the limita- 
tion of the circuit in regard to the trans- 
mission of speech, and equal to the prod- 
uct of the total capacity of the line and 
the total ohmic resistance. 

Retarding Coil. — A choking coil. 

Retarding Disc— A copper disc supported 
on a rotating shaft so placed as to cut 
magnetic flux, and be thereby retarded 
in its speed of rotation. 

Retardation. — A decrease in the speed of 
telegraphic signalling caused by distrib- 
uted electrostatic induction and resist- 
ance. 

Retardation Coil. — (1) A term sometimes 
used for choking coil. (2) An induction 
coil. (3) A retarding coil. 

Retardation, Electric. — A retardation in 



Ret.] 



906 



[Rev 



the starting or stopping of an electric 
current due to self-induction. 

Retarded Quadrature.— In a simple- 
harmonic-current circuit the condition of 
lagging in quadrature, or of phase differ- 
ence amounting to 90° in lag. 

Retentiveness. — Possessing the property 
of retentivity. 

Retentivity. — Possessing the power of re- 
taining magnetization or of resisting de- 
magnetization. 

Retort Carbon. — Carbon obtained from 
a deposit on the interior of a gas retort, 
and formerly used for the production of 
arc-light carbons. 

Return-Call Annunciator.— An annun- 
ciator connected with an answering call- 
box for showing that a call sent out has 
been received at the central station. 

Return Charge.— (1) A charge produced 
by an oscillatory return or back stroke of 
lightning. (2) A charge produced induc- 
tively by a lightning discharge. 

Return Circuit. — That part of a circuit 
by which an electric current returns to 
the source. 

Return Conductor. — The return wire. 

Return Current. — In telegraphy the elec- 
trostatic discharge from a cable or under- 
ground wire. 

Return Current. — The discharge current 
from a telegraph line passing to ground 
at the sending end. 

Return Feeders. — (1) The feeders through 
which a current returns to a central sta- 
tion. (2) Negative feeders. (3) The 
feeders connected with the track in a 
trolley system. (4) Ground feeders. 

Return Feeders for Railway Circuits. 
Copper conductors employed in rail- 
way circuits for re-enforcing ground-re- 
turn circuits, and usually insulated. 

Return Ground. — (1) That part of the 
ground employed as a return. (2) The 
ground-return. 

Return-Signal Call-Box. — An answer- 
ing call-box. 

Return Stroke of Lightning. — An 
electric discharge induced by the direct 
discharge of a lightning flash, as distin- 
guished from the direct discharge itself. 

Return-Track Feeder. — A feeder in a 
trolley system connected to the track. 

Return Wire. — The wire or conductor by 
means of which the current returns to 
the electric source after having passed 
through the electro-receptive devices. 

Returns. — In a system of distribution, 
those conductors through which the cur- 



rent flows back from the electro-receptive 
devices to the sources. 

Reversal. — (1) A change in direction. 
(2) A semi- wave. 

Reversal of Phase.— A change in the 
phase of a current due either to the re- 
versal of the current or of the conductor 
in which it is produced. 

Reversals. — In telegraphy, alternate-cur- 
rent signals transmitted for the purpose 
of adjustment or for clearing the line of 
a charge. 

Reverse - Current Working. — Teleg- 
raphic transmission by means of reverse 
currents, or double currents. 

Reverse Currents.— (1) A name some- 
times applied to alternating currents. 
(2) A name sometimes applied to double- 
currents. 

Reverse-Induced Current.— (1) The cur- 
rent induced by a current in its own cir- 
cuit at the moment of making or closing 
the circuit. (2) The current induced in a 
secondary circuit on making or clos- 
ing a primary circuit. 

Reverser. — Any device for reversing or 
changing the direction of a current. 

Reverser Bars.— The commutator con- 
nection employed in Sayer's armature 
winding which carries the current during 
the short time that the corresponding 
sections are passing under the brushes. 

Reversible Bridge. — A bridge or balance 
so arranged that the proportionate coils 
can be readily interchanged, thus per- 
mitting the bridge coils to be readily 
tested by reversing. 

Reversible Electric Motor. — (1 ) A mo- 
tor whose direction of motion is readily 
reversed. (2) A motor which is so ar- 
ranged as to be readily operated as a gen- 
erator. 

Reversible Heat. — The heat produced in 
a heterogeneous conductor by the passage 
through it of an electric current. 

Reversible Heating Effect of Elec- 
tricity. — A term sometimes employed in 
place of the Peltier effect. 

Reversible Regenerative Armature.— 
A regenerative armature that is capable 
of generating electromotive forces when 
the direction of its rotation is reversed. 

Reversibility of Dynamo.— The ability 
of a dynamo to operate as a motor when 
traversed by an electric current. 

Reversing. — Changing any direction to its 
opposite. 

Reversing a Current.— Changing the di- 
rection of a current. 



Rev.] 



90: 



[Rib. 



Reversing Cell. — A voltaic cell whose 
couple and electrolyte are contained in a 
hermetically closed vessel so arranged 
that when the cell is placed in one posi- 
tion the electrolyte does not touch the 
couple, and when reversed the electrolyte 
surrounds the couple. 

Reversing Oontrolling-Box. — A motor 
controlling-box which enables the direc- 
tion of rotation of the motor to be re- 
versed. 

Reversing Cylinder. — (1) The cylinder in 
a motor-controlling apparatus carrying 
the reversing contacts. (2) The contact 
cylinder of a reversing switch. 

Reversing-Gear of Electric Motor.— 
Apparatus for obtaining a reversal in the 
direction of rotation of a motor. 

Reversing-Handle of Car Controller.— 
(1) A switch handle placed on a car con- 
troller for the purpose of changing its 
direction of motion. (2) The handle of 
an emergency switch in a street-car con- 
troller. 

Reversing Key. — (1) A key inserted in 
the circuit of a galvanometer for obtain- 
ing deflections of the needle on either side 
of the galvanometer scale. (2) A key 
which serves to reverse the current sup- 
plied to a circuit. 

Reversing Key of Quadruplex Tele- 
graphic System. — The key in a quadru- 
plex system which reverses the direction 
of the current and so operates one of the 
distant instruments. 

Reversing Magnetic-Field.— That por- 
tion of the field of a dynamo produced b} r 
the field-magnet coils, in which the cur- 
rents flowing in the armature coils are 
stopped or reversed after the coil has 
passed its theoretical position of neu- 
trality. 

Reversing Switch.— A switch employed 
in reversing a circuit or current. 

Revolving Primary of Induction 
Motor. — (1) A rotor primary. (2) In an 
induction motor, a revolving element 
connected with the line. 

Revolving System.— The twist system of 
erecting telegraph or telephone wires, so 
as to avoid induction. 

Rheocord. — A word formerly employed 
for rheostat. (Obsolete.) 

Rheometer. — A word formerly employed 
for any device for measuring the strength 
of a current. (Obsolete.) 

Rheomotor. — A word formerly employed 
to designate any electric source. (Obso- 
lete.) 

Rheophore.— A word formerly employed 



to indicate a portion of a circuit convey- 
ing a current and capable of deflecting a 
magnetic needle placed near it. (Obso- 
lete.) 

Rheoscope. — A word formerly employed 
in place of galvanoscope. (Obsolete.) 

Rheoscopic Limb. — A word sometimes 
employed for a physiological rheoscope, 
such as the galvanoscopic frog. 

Rheostat. — An adjustable resistance. 

Rheostat Frame. — A perforated frame or 
casing in which the separate resistances 
of a rheostat are placed. 

Rheostat Handle of Car-Controller. — 
The main switch of a car-controller. 

Rheostat Panel. — A panel in any switch- 
board to which the rheostat circuits are 
connected. 

Rheostatic Machine. — A machine de- 
vised by Plante in which continuous static 
effects of considerable intensity are ob- 
tained by charging a number of con- 
densers from storage cells connected in 
multiple-arc, and then discharging the 
condensers in series. 

Rheotome. — A word formerly employed 

for interrupter. (Obsolete. ) 
Rheotometer.— A compound bridge and 

rheostat. 

Rheotrope. — A word formerly employed 
for commutator or current reverser. 

Rhigolene. — A highly volatile hydro-car- 
bon obtained during the distillation of 
coal-oil, and sometimes employed in the 
flashing treatment of incandescent lamp 
filaments. 

Rhumbs of Compass.— The points of a 
mariner's compass. 

Ribbed Armature-Core.— A cylindrical 
armature core provided with longitudinal 
projections or ribs which serve as grooves 
for the reception of the armature coils. 

Ribbon Conductor.— A flat, ribbon- 
shaped conductor. 

Ribbon Copper. — A copper strip or rib- 
bon-shaped copper conductor. 

Ribbon Core. — A form of laminated core 

made by iron ribbons. 
Ribbon Fuse. — A fuse in the shape of a 

ribbon. 

Ribbon Induction-Coil. — An induction- 
coil whose primary and secondary circuits 
are formed of metallic ribbons instead of 
wires. 

Ribbon Vibrator.— An electro-magnetic 
contact-breaker consisting of a horizontal 
steel ribbon, the rate of vibration of 



Rig. 



908 



[Rin. 



which can be varied by varying its ten- 
sion. 

Right - Angled Trolley - Crossing. —A 
trolley crossing placed at a point where 
two streets intersect at right angles. . 

Right-Hand Trolley-Prog.— A trolley 
frog used at a point where a branched 
trolley wire leaves the main line on the 
right hand in the direction of advance. 

Right-Hand Trolley-Switch.— A term 
sometimes used for a right-hand trolley 
frog. 

Right-Handed Armature Winding.— 
An armature winding applied to the core 
in a right-handed or dextrorsal helix. 

Right-Handed Dynamo.— A dynamo 
whose proper direction of rotation is 
right-handed regarded from the pulley 
end. 

Right-Handed Helix.— (1) A right- 
handed solenoid. (2) A helix wound 
right-handedly when regarded from either 
end. 

Right-Handed Motor.— A motor ar- 
ranged to run right-handedly or clock- 
wise when regarded from the pulley end. 

Right-Handed Rotation.— ( 1) A direction 
of rotation which is the same as that of 
the hands of a watch, when one looks 
directly at the face of the watch. (2) Neg- 
ative rotation. 

Right-Handed Solenoid.— A dextrorsal 
solenoid or one whose winding is right- 
handed. 

Right-Handed Spiral.— A term some- 
times used for right-handed solenoid. 

Right-Handed Winding.— A winding 
applied in a right-handed direction. ■ 

Ring Armature. — An armature provided 
with a ring-shaped core. 

Ring- Armature Core. — A ring-shaped 
armature core. 

Ring Clutch. — A form of clutch employed 
for gripping the lamp rod of an arc-lamp 
when slightly moved from a horizontal 
position. 

Ring Clutch for Arc-Lamp.— A ring- 
shaped clutch embracing the lamp rod, 
which grips or holds the rod when tilted 
or inclined, but permits it to fall when in 
a horizontal position. 

Ring-Connected Armature. — An arma- 
ture provided with ring connections. 

Ring-Connected Generator.— A gener- 
ator provided with an armature winding, 
in which corresponding points are con- 
nected to ring conductors for the purpose 
of equalizing the magnetic flux and the 
current distribution around the armature. 



Ring Connections of Armature — Con- 
ductors in the form of rings in a multi- 
polar armature to each of which are con- 
nected corresponding points of the arma- 
ture winding for the purpose of equaliz- 
ing the current and magnetic flux in the 
machine. 

Ring Core. — A ring-armature core. 

Ring Current of Triphase System.— 
The current flowing between adjacent 
wires or terminals of a triphase system. 

Ring Magnet.— A uniformly magnetized 
rod bent into a closed ring. 

Ring Mam.— A ring-shaped distributing 
main. 

Ring-Off. — A term employed for a signal 
sent by a telephone correspondent when 
the conversation is finished. 

Ring-Off Drop.— (1) A telephone drop re- 
leased by a ring-off signal. (2) A drop 
placed at a central telephone station, and 
operated by a subscriber when he rings 
off or hangs up his telephone. 

Ring-Off Signal. — A signal given by a 
subscriber at the close of his conversation, 
to inform the central station that the 
connection may be discontinued. 

Ring-Off Telephone-Indicator. — Any 
indicator on a telephone switchboard that 
is operated by a ring-off signal. 

Ring Potential of Triphase System.— 

The effective difference of potential or 
voltmeter pressure between adjacent 
lines or terminals of a triphase system. 

Ring-Up.— (1) In telephony, to actuate the 
call-bell of a subscriber wanted. (2) To 
call up an operator at an exchange or a 
distant subscriber. 

Ring Windings. — Windings suitable for 
use in a ring-wound armature. 

Ring - Wound Armature. — An arma- 
ture consisting of a ring core with coils of 
wire wound thereon. 

Ringer. — A telephone magnet. 

Ringer Coils. — The coils or winding of a 
telephone magneto. 

Ringer Magnet. — A permanent magnet 
employed in a telephone magneto or 
ringer. 

Ringing Keys. — In a telephone switch- 
board, keys for closing a generator upon 
a subscriber's circuit to ring his bell. 

Ringing Key. — In a telephone switch- 
board, a key employed to ring up a sub- 
scriber. 

Ringing • Key -Bars. — In a telephone 
switchboard, metallic bars connecting the 
ringing keys with the instrument bars 
and generator. 



Bin.] 



909 



[Roo. 



Rings, Electric. — A term sometimes used 
instead of Nobili's rings. 

Ripple Marks, Electric— Wave marks 
produced in a fine powder by a neighbor- 
ing Ley den- jar discharge. 

Risers. — (1) Supply wires which lead the 
current from the service wires to the dif- 
ferent floors of a building. (2) The supply 
wires which rise to the various floors, as 
distinguished from floor mains, submains, 
or branches, which run along each floor. 

River Cable. — (1) A cable suitable for use 
in a river. (2) A form of sub-aqueous 
cable. 

Riveted Rail way- Joint. —A rail- bond in 
which the connection between two con- 
tiguous rails is obtained by riveting spe- 
cially heavy fish-plates to each end of the 
rail. 

Riveting Apparatus. Electric— A rivet- 
ing apparatus employing electrically gen- 
erated heat. 

Roaring of Arc — A roaring sound attend- 
ing the formation of a powerful voltaic 
arc when the carbons are too near to- 
gether. 

Rock-Drill, Electric— An electrically 
operated rock-drill. 

Rocker Arm. — An arm on which the 
brushes of a dynamo or motor are mount- 
ed for the purpose of shifting their posi- 
tion on the commutator. 

Rocker-Arm Circle. — The frame of a 
dynamo-electric machine which supports 
the brush arms and is capable of adjust- 
ment in angular position. 

Rocking Switch. — An automatic throw- 
over switch. 

Rod Clamp. — A clamp employed in the 
lamp-rod of an arc-lamp. 

Rod Clutch. — The clutch employed for 
gripping an arc-lamp rod. 

Rod Switch. — A switch provided for 
lighting and extinguishing a lamp, so ar- 
ranged that it can readily be pushed to its 
off or on position by means of a rod. 

Rodding a Conduit.— The process of in- 
troducing a drawing-in wire through the 
ducts of an underground conduit by 
pushing a number of short sections of 
jointed rods through such ducts. 

Roentgen Effects.— The peculiar effects 
produced by Roentgen or X-rays. 

Roentgen Ether Waves.— A term some- 
times employed for Rontgen rays. 

Roentgen Radiograph. —A word pro- 
posed for radiograph. 



Roentgen-Ray Picture.— A word pro- 
posed for radiograph. 

Roentgen-Ray Screen.— ( 1 ) A screen cov- 
ered with fluorescent material intended 
to receive a visible Roentgen picture. 
(2) A fluoroscopic screen. 

Roentgen Ray Transformer.— An alter- 
nating-current transformer suitable for 
operating a Roentgen ray tube. 

Roentgen-Ray Tube.— A vacuum tube 
for the production of Roentgen rays, or 
X-rays. 

Roentgen Rays. — A peculiar radiation 
emitted in the neighborhood of that por- 
tion of a high vacuum tube on which the 
cathode rays fall. 

Roentgen Shadow Print. — A radio- 
graph. 

Roentgen Streams. —(1) Roentgen or 
X-rays. (2) A term applied to the Roent- 
gen rays, by those who regard them 
as consisting of actual streams of matter 
thrown off, either from the cathode, or 
from the residual atmosphere of the 
vacuum tube. 

Roentgen Tube. — Any high-vacuum tube 
capable of producing Roentgen rays. 

Roentgengram.— A t word proposed for 
radiograph. 

Roentgengraph. — A word proposed for 
radiograph. 

Roget's Spiral. — (1) A spiral, helix or 
solenoid, freely suspended at its upper 
end so that its lower end shall dip in a 
mercury surface, which when traversed 
by a sufficiently powerful current will 
break its own circuit by the attraction 
produced by its adjacent convolutions 
when by its weight it will complete the 
circuit, and thus be alternately opened 
and closed. (2) A form of automatic con- 
tact-breaker. 

Roman Vitriol.— A name formerly applied 
to blue-stone or copper sulphate. 

Rontgram. — A word proposed for radio- 
graph. 

Rontgraph. — A word proposed for radio- 
graph. 

Rontgraphy . — A word proposed for radio- 
graphy. 

Roof Box of Push. — A term sometimes 
employed for the upper covering of the 
box of a push-button. 

Roof Bracket.— fl) An insulator bracket, 
either straight or offset for attachment to 
a roof. (2) A form of house fixture pro- 
vided for the support of overhead wires. 

Roof Standard.— A form of house fixture 
provided for overhead wires. 



Boo.] 



910 



fRub. 



Room Call, Electric— Any device placed 
in the room of a hotel for the purpose of 
automatically sending calls to the office. 

Rope Transmission. — Transmission of 
power by means of ropes or cables. 

Rosette. — (1) An ornamental plate pro- 
vided with service wires and placed in a 
wall or ceiling for the ready attachment 
of an electric lamp or electrolier. (2) A 
word sometimes used in place of ceiling 
rose. 

Rosette Cut-Out. — A rosette for an elec- 
trolier, provided with a cut-out. 

Rotary Converter. — A secondary gener- 
ator for transforming alternating into 
continuous currents or vice-versd, con- 
sisting of an alternating-current machine 
whose armature winding is connected 
with a commutator ; or of a continuous- 
current machine, whose armature is 
tapped at symmetrical points and con- 
nected to collector rings ; so that, when 
the armature runs it is an alternator on 
one side and a direct current machine on 
the other. (2) A rotary transformer. 

Rotary Current.— (1) A name applied to 
any system of polyphase currents which 
are capable of producing a rotary field. 
(2) A rotating-current distribution. 

Rotary-Current Transformer. — A 
transformer capable of being operated by 
a rotary current. 

Rotary Electric Field.— A rotary elec- 
trostatic field. 

Rotary Electro-Type. — (1) A term some- 
times used for a turtle-back. (2) Any 
electro-type with a curved surface suit- 
able for printing in a cylinder press. 

Rotary-Field Induction-Motor. — An 
induction motor operated by a rotary 
field. 

Rotary -Field Motor.— A rotary-field in- 
duction-motor. 

Rotary Induction Transformer. — A 

rotary-current transformer. 

Rotary-Magnetic Field.— (1) A field 
produced by a rotary current. (2) A mag- 
netic field in which a set of magnet 
poles is produced, whose successive posi- 
tions are such that a rotation of the field 
is effected. 

Rotary -Magnetic Polarization. — The 
rotation of the plane of polarization of a 
beam of plane-polarized light, consequent 
on its passage through a medium sub- 
jected to the stress of a magnetic field. 

Rotary Magnetism. — The magnetism 
produced by a rotary magnetic field. 

Rotary-Phase Alternating-Currents. 

Rotary-phase currents. 



Rotary-Phase Currents.— A term some- 
times employed for a rotating electric 
current distribution. 

Rotary -Phase Dynamo.— A term some- 
times employed for a rotating-current 
dynamo. 

Rotary Transformer. — (1) A term gener- 
ally employed for the combination of a 
motor and generator in one machine 
having a single armature-winding trav- 
ersed both by alternating and continuous 
currents. (2) A secondary generator for 
transforming from alternating to contin- 
uous currents or vice-versd. (3) A rotary 
converter. 

Rotating Brushes of Dynamo.— (1) Ro- 
tating discs of metal employed in place of 
the ordinary brushes for carrying off the 
current from the armature of a dynamo. 
(2) Brushes revolved around the periphery 
of a commutator. 

Rotating Current.— (1) A term applied 
to the current which results by combining 
a number of alternating currents, whose 
phases are definitely displaced with re- 
spect to one another. (2) A polyphase or 
multiphase current. 

Rotating-Current Field. — A magnetic 
field produced by a rotating current. 

Rotating-Current Motor. — A motor 
operated by a rotating current. 

Rotating-Current Transformer.— A ro- 
tary-current transformer. 

Rotating Transformer.— (1) A rotary 
transformer. (2) An induction motor. 

Rotating Vector. — A line or vector 
quantity which rotates about a fixed 
point. 

Rotometer. — A form of cyclometer at- 
tached to a drum for measuring the 
amount of cable passing over the drum in 
picking up or paying out a submarine 
cable. 

Rotor. — That portion of a dynamo-electric 
machine which rotates. 

Rotor Armature. — An armature which 
rotates. 

Rotor Circuit. — The circuit of a rotor. 

Rotor Coils. — The coils placed on a rotor. 

Rotor Currents. — The currents produced 
in the rotor coils. 

Rotor Field. — The field of a rotor. 

Round Wire-Gauge.— A. wire gauge con- 
sisting of a circular plate provided on its 
circumference with slots of various sizes. 

Rubber of Electric Machine. — That 
portion of a frictional machine which 
produces the electricity by rubbing against 
a disc or plate. 



Rub. 



911 



[Saf. 



Rubber Tape. — A form of adhesive, in- 
sulating tape made of rubber. 

Rubbing Contact.— A contact effected 
by means of a rubbing motion. 

Rubbing Contact Key.— A key provided 
with a rubbing contact. 

Ruhmkorff Coil.— (1) An early form of 
induction coil or step-up transformer. 
(2) An induction coil having an iron-wire 
core, and a fine wire secondary coil of 
many turns for the production of power- 
ful induced E. M. F.'s, usually excited 
from a battery or continuous - current 
source through a suitable current breaker. 

RuhmkorfF Commutator. — A com- 
mutator employed in a Ruhmkorff coil 
for reversing the direction of the current 
through the primary. 

Rumble. — A barrel, or hollow box, rotated 
by mechanical power, in which small 
articles are prepared for electro-plating 
by the polishing obtained by their attrition 
against one another, or against hard ob- 
jects placed therein. 

Run-Down Cell. — An exhausted cell. 

Running-Board. — A device employed in 
the construction of a heavy overhead line, 



consisting in placing a number of reels 
of wire, usually ten or more, on a spindle, 
and arranging a piece of wood as a cross- 
arm to which ten or more wires are at- 
tached, harnessing horses to the cross- 
piece, and then dragging the running 
board away as the wires are paid out 
from the reels, and passing them over 
their appropriate cross-arms, where they 
are at once secured to the insulators by 
line-men. 

Running Guard- Wire.— A wire provided 
in a system of aerial trolley circuits, ex- 
tending parallel to and immediately above 
the trolley wire, intended to intercept any 
wire falling on the line from above. 

Running Position of Street-Car Con- 
troller. — A position of the switch-handle 
of a street-car controller at which current 
is supplied to the car-motors and they are 
kept in rotation, as distinguished from a 
position in which the current is cut-off. 

Running Rope. — A rope attached to the 
running-board employed in the stringing 
of aerial wires. 

Running Torque of Motor.— The torque 
exerted by a motor while running, as 
distinguished from the starting torque. 



S. — A contraction proposed for surface. 

S. — A contraction proposed for second. 

S. — An abbreviation for second, the C. G. S. 
unit of time. 

S. C. — A contraction for secondary current. 

S. Gr. — In submarine telegraphy, the prefix 
for a service message, or a message relat- 
ing to the business of the company only. 

i?. H. M. — A contraction for simple-har- 
monic motion. 

S. P. D. — A contractive for secondary pot- 
ential difference. 

S.N. Code. — A contraction for single- 
needle code. 

S. N. Telegraphic-Instrument.— A con- 
traction employed for single-needle tele- 
graphic instrument. 

S. P. Cut-Out. — A contraction for single- 
pole cut-out. 

S. R. G-. — A contraction for standard rail- 
road gauge or 4'.8£". 

S. W. G-. — A contraction for the British 
standard wire gauge. 

S. W. G. — A contraction for Stubb's wire 
gauge. 



Saddle Bracket.— A bracket holding an 
insulator and fastened to the top of a tele- 
graph or telephone pole. 

Safe Alarm. — An electro-magnetic alarm 
connected with a safe and designed to 
give notice of an attempt to force the same. 

Safe Carrying Capacity of a Conduc- 
tor. — The maximum electric current a 
conductor will carry without becoming 
unduly heated. 

Safety Catch. — A safety fuse. 

Safety-Catch Holder.— A holder for a 
safety fuse. 

Safety Cut-Out.— A safety fuse. 

Safety Device. — Any device by means of 
which a circuit is automatically opened 
or short-circuited when the current pass- 
ing through it exceeds certain pre-deter- 
mined limits. 

Safety Device for Arc-Lamps or Series 
Circuit. — Any mechanical device which 
automatically provides a path for a cur- 
rent around a lamp, or other faulty re- 
ceptive device in a series circuit, and thus 
prevents the opening of the entire circuit 
on the failure of such device. 



Saf. 



912 



[Sea* 



Safety Device for Multiple Circuit.— 

(1) A safety fuse. (2) A fuse wire or strip. 
(3) Any device for protecting a branch 
circuit, instrument or conductor from an 
excessive current. 

Safety Factor of Transformer. — The 
ratio of the voltage with which a trans- 
former has been tested, to the voltage at 
which it is operated. 

Safety Fuse. — A wire, bar, plate or strip 
of readily fusible metal, capable of con- 
ducting, without fusing, the current or- 
dinarily employed on the circuit, but 
which fuses and thus automatically 
breaks the circuit on the passage of an 
abnormally strong current. 

Safety Fuse-Block.— A block provided 
for the reception of a safety fuse. 

Safety Lamp, Electric— (1) An incan- 
descent lamp, provided with thoroughly 
insulated leads, employed in mines or other 
similar places, where the explosive effects 
of readily ignited substances are to be 
feared. (2) A portable electric incandes- 
cent lamp and battery for use in mines 
where explosive gases may be found. 

Safety Link. — A link-shaped safety-fuse. 

Safety Plug.— (1) A safety fuse. (2) An 
insulating screw-plug containing a safety 
fuse, which by its insertion in a suitably 
prepared socket, automatically closes the 
circuit through such fuse. 

Safety Strip. — A strip of fusible metal 
employed as a safety fuse. 

Sag of Conductor or Line "Wire.— The 
dip of an aerial wire or conductor, be- 
tween two adjacent supports, due to its 
weight. 

Sag Error. — (1) Any error in installing an 
aerial wire due to insufficient allowance 
for sag with change of temperature. (2) 
Any error in computing the length of an 
aerial wire due to insufficient allowance 
for sag. 

Saint Elmo's Fire.— Tongues of faintly 
luminous flame which sometimes appear 
on the pointed ends of earth-connected 
bodies, such as the tops of church stee- 
ples, or the masts of ships. 

Salient Magnetic Poles. — A term some- 
times applied to the single poles located 
at the extremities of an anomalous mag- 
net, in order to distinguish them from 
the double or consequent poles formed by 
the juxta-position of two similar mag- 
netic poles. 

Salimeter. — A form of hydrometer suit- 
able for measuring the density of a saline 
solution. 

Saline Creeping. — The formation, by efflo- 



rescence, of salts on the walls of a solid 
immersed in a saline solution. 

Saline Solution.— A solution of a salt in 
a liquid. 

Sand-Barrel Setting for Pole.— A stout 
barrel or cask, placed in the bottom of 
an excavation in a loose, sandy soil, as a 
pole foundation in which the butt of the 
pole is placed, and a firm loam or clay 
tightly packed into the barrel around the 
pole. 

Sand-Box for Electric Car.— A box em- 
ployed for holding sand, so arranged as 
to distribute it over a track as desired, 
for the purpose of increasing the friction. 

Sanding Device.— A device employed for 
sprinkling sand over a car-track. 

Sandy Electro-Metallurgical Deposit. 
A non-coherent electro-metallurgical de- 
posit, which occurs when the current 
density exceeds its normal value. 

Sash Lines. — Ropes employed in raising 
telegraph poles to the vertical position. 

Saturated Solution. — A solution in 
which as much of the solid has been dis- 
solved as the solvent will take at a given 
temperature. 

Saturating Flux.— The flux required to 
produce magnetic saturation in any cir- 
cuit. 

Saw, Electric— An electrically operated 
saw. 

Saw - Tooth Lightning - Arrester. — A 
name sometimes applied to a comb light- 
ning-arrester. 

Sayers Armature Winding.— An arma- 
ture winding provided with additional 
coils called commutator coils which are 
subjected to the influence of an auxiliary 
pole and which are introduced into the 
main circuit to obtain sparkless commu- 
tation. 

Scalar. — The name given to a quantity 
which has no directive property, or which 
has numerical magnitude only, such as 
temperature, or energy, as distinguished 
from a vector quantity. 

Scalar Potential. — A potential possessing 
magnitude and sign without direction, as 
distinguished from a vector potential 
which possesses both direction and mag- 
nitude. 

Scale Zero. — (1) An instrument zero. (2) 
A zero selected at the zero mark of a scale. 

Scarf Joint of Conductors.— A joint be- 
tween the ends of conductors in which 
the ends are prepared by filing them diag- 
onally, so that when laid together and 
soldered, the joint is cylindrical in shape, 



Sch. 



913 



[Sec. 



presents no rough edge, and, unlike a 
butt joint, extends over an appreciable 
length. 

Sch.iseoph.one. — An electro - mechanical 
appliance for detecting flaws or internal 
defects in rails or other metallic masses. 

Schweigger's Multiplier. — A name 
formerly given to a coil consisting of a 
number of turns of insulated wire, pro- 
vided for the purpose of increasing the 
strength of the magnetic field produced 
by an electric current, and so increasing 
the amount of its deflecting power on a 
magnetic needle. 

Sciagraph. — A word proposed for radio- 
graph. 

Sciagraphic Print. — A word sometimes 
used for radiograph. 

Sciagraphy.— A word proposed for radi- 
ography. 

Scintillating Jar.— A Leyden jar whose 
coatings, instead of being formed of con- 
tinuous sheets of tin-foil, are formed of 
small pieces, placed at regular intervals 
on the glass or dielectric, so as to leave a 
small space between them. 

Scratch Brush. — A brush made of wires, 
or of stiff bristles, employed for cleansing 
the surfaces of metallic objects before sub- 
jecting them to the electro-plating proc- 
ess. 

Scratch Brushing. — Cleansing the sur- 
faces of articles to be electro-plated by 
friction with a scratch brush. 

Screen, Electric. — A closed conductor 
placed over a body in order to protect or 
screen it from the effects of external 
electro-static fields. 

Screening. — Protecting a body from the 
effect of an electrostatic or electro-mag- 
netic field by means of a screen. 

Screening Effect of Eddy Currents.— 
A term sometimes used for the effect pro- 
duced by eddy currents in a solid mass of 
iron or steel, of shielding the interior of 
the mass from an externally applied 
alternating magnetic field. 

Screw Block-Fuse.— (1) A form of plug 
cut-out. (2) A sc lew-plug in a receptacle 
or block containing a fuse. 

Screw Cleat. — A cleat provided with a 
screw for its ready attachment to wood- 
work. 

Sea Cell Test.— In a sub-marine system of 
electric torpedoes, a circuit test by means 
of a single voltaic cell in which sea water 
is the electrolyte. 

Sea Telegraphy.— (1) Submarine Teleg" 
58 



raphy. (2) Telegraphy carried on at 
sea either between neighboring vessels or 
between different parts of the same ves- 
sel. 

Seal of Meter. — A leaden seal placed on a 
meter, after it has been properly installed, 
for preventing its being tampered with. 

Sealing-In of Filament. — Effecting a 
hermetical seal between the support of 
the filament of an incandescent lamp and 
the lamp chamber in which it is placed. 

Sealing-Off of Lamp Chamber.— Her- 
metically closing a lamp chamber while 
it is connected with the pumps, by the 
fusing of the glass. 

Sealing Tools. — Tools employed for place 
ing a seal on a meter. 

Sealing Wires.— Wires employed for 
forming part of the seal of a meter. 

Search-Light, Electric. — A focussing 
arc light placed in front of a reflector 
or lens, for the purpose of obtaining an 
approximately parallel beam of light for 
lighting the surrounding space. 

Searching Coil. — A term sometimes ap- 
plied to an exploring coil. 

Secohm. — (1) The practical unit of self- 
induction, or of inductance. (2) A length 
equal by definition to that of an earth 
quadrant, or very nearly 10 9 centimetres. 

(3) A henry. 

Secohmmeter. — An apparatus for measur- 
ing the self -inductance, the mutual in- 
ductance, or the capacity of conductors. 

Secondary.— A word frequently employed 
for the secondary coil of a transformer or 
induction coil. 

Secondary Accumulator. — A storage- 
cell accumulator. 

Secondary Ampere-Turns. — Ampere- 
turns in the secondary of a transformer 
or induction coil. 

Secondary Admittance. — The admit- 
tance of a secondary circuit. 

Secondary Battery. — A word frequently 

used for storage battery. 
Secondary Cell. — A word frequently used 

for storage cell. 

Secondary Clock. — Any clock in a system 
of time telegraphy that is controlled by 
a master clock. 

Secondary Coil of Transformer. — 
(1) The coil of a transformer into which 
energy is transferred from the primary 
line and primary coil. (2) Thesecondary 
winding of a transformer or induction 
coil. (3) The driven coil of a transformer. 

(4) The coil in the external circuit of 



Sec] 



914 



[Sec, 



which there is no directly impressed E. 
M. F. 

Secondary Currents.— (1) The currents 
produced in the secondary of a trans- 
former. (2) The currents produced by 
secondary batteries. (3) Currents in any 
secondary circuit. 

Secondary Electromotive Forces.— A 
name sometimes given to the electromo- 
tive forces produced by a secondary cell 
or battery. 

Secondary Element of Induction 
Motor. — Those portions of an induc- 
tion motor, closed upon themselves, in 
which currents are induced. 

Secondary Frequency of Induction 
Motor. — The frequency of the alternat- 
ing currents induced in the secondary 
circuits of an induction motor, compris- 
ing only a small fraction of the frequency 
in the primary circuit or circuits. 

Secondary Fuse-Box. — A fuse box placed 
in the secondary circuit of a transformer 
or induction coil. 

Secondary Generator.— (1) A generator 
which is not a prime source of energy, 
but receives its energy from some other 
electrical circuit either at some anteced- 
ent period, as in the case of a storage cell, 
or coincidently, as in the case of a trans- 
former. (2) A term sometimes employed 
for transformer. 

Secondary Generator. — A device em- 
ployed in alternating-current circuits for 
obtaining the working pressure on one 
circuit by induction from a neighboring 
circuit. 

Secondary Impressed Electromotive 
Force. — The E. M. F. impressed upon a 
secondary circuit, as distinguished from 
the E. M. F. that is active in producing 
current, or the E. M. F. exerted in over- 
coming self-induction. 

Secondary Impedance. — In a secondary 
circuit, the impedance, either of part, or 
of all of the circuit. 

Secondary Movers.— The driven shafts 
or machines, as distinguished from the 
driving shafts or machines. 

Secondary Plate of Condenser.— That 
plate of a condenser in which a charge is 
induced by the presence of a charge on 
the opposite plate. 

Secondary Primary. — A winding on an 
induction coil intermediate between the 
secondary and primary windings, ar- 
ranged with the aid of revolving contacts 
to serve, in each cycle, first as a secondary, 
and next as a primary winding, for the 
purpose of reducing the sparking at the 



contact wheel of the primary coil when 
excited from an incandescent-lighting 
continuous-current circuit . 

Secondary Resistance.— The resistance 
of a secondary coil or circuit . 

Secondary Spiral of Induction Coil. — 
A term sometimes employed for the sec- 
ondary winding of an induction coil. 

Secondary Standard of Light.— Any 
standard of photometric intensity of light 
that is not a fundamental standard, but 
which is used as an intermediary to, or 
with reference to, a fundamental stand- 
ard. 

Secret Telephone System.— A domestic 
telephone system arranged so that tele- 
phonic communication can be obtained 
between any two stations without being 
overheard by a person at any other sta- 
tion, and without the aid of an attendant 
or exchange. 

Secretion Current.— A current following 
electric stimulation of the secretory 
nerves. 

Section.— (1) Apart. (2) A cutting plane. 

(3) A graphical representation of the ap- 
pearance that is, or would be, presented by 
a body when exposed at a cutting plane. 

(4) In a trolley system, a portion or length 
of trolley conductor insulated from ad- 
jacent portions. 

Section Box. — In a trolley system, a box 
containing the connection to a section 
and the switch by which it is connected 
to a feeder. 

Section Circuit-Breaker.— A magnetic 
circuit-breaker controlling a trolley-wire 
section. 

Section of Multiple Switchboard.— A 
complete division or reduplicating unit of 
a switchboard, in which, every jack ap- 
pears once. 

Section of Switchboard.— A term some- 
times used for a panel or a part of a 
ijanel of a switchboard. 

Section Insulator. — An insulator in a 
trolley-wire system, which electrically 
disconnects one trolley section from an- 
other. 

Sectional Feeding-Point. — In a street- 
railway system, a point where a feeder 
connects with a section of trolley wire or 
main-supply conductor. 

Sectional Plating. — Plating an article 
with a greater thickness of metal at cer- 
tain points than at the rest of the surface. 

Sectional Plating-Frame.— A frame em- 
ployed for holding an object to be electro- 
plated so that it shall receive a greater 



Sec] 



915 



[Sel. 



depth of deposit on certain portions of its 
surface than elsewhere. 

Sectional Trolley-Line.— A system of 
trolley wires divided into sections. 

Sectioned Coils for Magnet.— (1) A term 
employed for a method of winding a 
magnetizing coil, in separate compart- 
ments. (2) Dividing a winding space 
into short axial sections, and filling each 
with wire. 

Secular. — Of or pertaining to cycles of 
time. 

Section Switch. — In a system of railway 
or power-distribution, a switch control- 
ling and supplying a section. 

Secular Variation. — A variation in the 
magnetic declination, which occurs at 
cycles or great intervals of time, as op- 
posed to diurnal or annual variations. 

Seebeck Effect. — A term sometimes em- 
ployed for thermo-electric effect. 

See-Sawing. — A term employed to char- 
acterize the condition of two parallel-con- 
nected alternators when they do not syn- 
chronize properly. 

See-Sawing of Parallel-Connected 
Generators. — (1) A term sometimes ap- 
plied to the hunting of generators. (2) 
Imperfect synchronism between gener- 
ators. 

Segment Switch.— A switch in which a 
pivoted strip or lever moves over the arc 
of a circle divided into insulating seg- 
ments. 

Segmental Core-Disc. — A dynamo core- 
disc which, instead of being made in one 
piece, is formed of suitable joined seg- 
ments. 

Seismic Photo-Chronograph. — A chro- 
nograph that photographically records 
seismic disturbances. 

Seismograph, Electric— An apparatus 
for electrically recording the direction 
and intensity of earthquake shocks. 

Selectance. — The property by virtue of 
which resonant electric circuits respond 
more to one frequency of alternating cur- 
rent than to another. 

Selective Absorption.— The absorption 
of a particular or selected character of the 
waves of sound, light, heat or electricity. 

Selective Consonance.— That property 
of a consonant alternating-current circuit 
by virtue of which it responds more to 
one frequency than to another. 

Selective Emission. — Selective radia- 
tion. 
Selective Opacity .—(1) Opacity limited to 



certain frequencies only. (2) Selectivity 
as regards transparency. 

Selective Radiation. — (1) Radiation 
limited to certain frequencies. (2) Selec- 
tivity as regards radiation. 

Selective Resonance. — The property of a 
resonant circuit which renders it selective 
to a definite frequency of alternating 
current. 

Selective Signal.— (1) A term sometimes 
employed for an individual signal. (2) 
A signal which affects one only of a 
plurality of translating devices connected 
to a circuit. 

Selective-Signal Pendulum.— A system 
of selective signalling in which the re- 
ceiving bells respond each to a single 
alternating-current frequency, and the 
transmitting frequency is adjusted cor- 
respondingly by altering the virtual 
length of a pendulum swinging in the 
transmitter. 

Selective Signalling - Apparatus. — A 
term sometimes employed for individual 
signalling-apparatus. 

Selectivity .—(1) The capability for devel- 
oping selective action. (2) The degree 
of capability for effecting selection. 

Selenium. —A comparatively rare element, 
generally found associated with sulphur, 
the electric resistance of which is affected 
by light. 

Selenium Battery. — A number of sepa- 
rate selenium cells connected so as to 
form a single cell or battery. 

Selenium Cell. — A cell consisting of a 
mass of selenium fused in between two 
conducting wires or electrodes of platin- 
ized silver, or other suitable metal. 

Selenium Eye. — A rough model of the 
human eye in which a selenium resist- 
ance takes the place of a retina and two 
slides the place of the eyelids. 

Selenium Photometer.— (1) A photo- 
meter in which the intensity of the light is 
estimated by the comparison of the 
changes in the resistance of a selenium 
resistance, successively exposed under 
.similar conditions to the light to be 
measured and to a standard light. (2) A 
photometer employing the photo-electric 
properties of selenium. 

Selenium Resistance.— A mass of sele- 
nium employed as a resistance, whose 
value varies with the variations in the in- 
tensity of the light to which it is exposed. 

Self-Acting Make-and-Break.— A term 
sometimes employed for an automatic 
make-and-break. 

Self- Aligning-Bearings.— Journal bear- 



Sel.] 



916 



[Sel, 



ings so constructed and adjusted as to 
permit of a slight angular range of move- 
ment in order to conform to the surface of 
the shaft. 

Self-Gleaning Contact Key.— A. name 
sometimes given to a key provided with a 
rubbing contact. 

Self-Closing Telegraphic Key.— A tele- 
graphic key provided with an automatic 
switch in its knob, so that pressing the 
key opens the switch, and releasing' the 
key automatically closes the switch. 

Self-Compounding Polyphase Gen- 
erator. — A polyphase generator whose 
field magnets are compound-wound, and 
which supplies the series winding with 
currents conclusively or inductively as- 
j sociated with those in the line. 

Self-Contained Engine or Machine.— 

An engine or machine all of whose work- 
ing parts are within the said engine or 
machine. 

Self-Cooling Transformer.— (1) A trans- 
former which maintains its temperature 
within the necessary safe limits by natural 
radiation and conduction, without the use 
of any external cooling apparatus. (2) 
An oil or air-insulated transformer in 
which no forced circulation of the air or 
oil is employed. 

Self-Demagnetizing Force. — The force 
exerted by a permanent bar magnet tend- 
ing to demagnetize itself, owing to the 
passage of some of its flux back through 
the bar in the opposite direction to the 
magnetiz 
the steel. 

Self-Excitation.— An excitation of the 
field magnets of a generator obtained 
by leading a portion or all of its own cur- 
rent through its field coils, as distin- 
guished from separate excitation. 

Self-Excited. — Excited by means of its 
own current. 

Self-Excited Alternator. — An alternator 
whose fields are self -excited. 

Self-Excited Dynamo. — A dynamo 
whose field is self -excited. 

Self-Excited Series-Wound Contin- 
uous-Current Generator. — A contin- 
uous-current generator having a series- 
w r ound field which is excited by the cur- 
rent supplied from the armature of the 
generator. 

Self-Excited Shunt-Wound Contin- 
uous-Current Generator.— A contin- 
uous-current generator having a shunt- 
wound field which is excited by a small 
part of the current supplied by the arma- 



ture and diverted from the external cir- 
cuit for that purpose. 

Self-Induced Current.— A current in- 
duced in a circuit, on the opening or 
closing of the circuit, by changes in its 
own strength. 

Self-induction. — Induction produced in 
a circuit by the induction of the current 
on itself at the moment of starting or 
stopping the current therein. 

Self-induction Coil. — (1) A coil of wire 
possessing self-induction. (2) A choking 
coil. 

Self-Locking Annunciator Drop. — 
A name sometimes given to a self-restor- 
ing telephone drop. 

Self-Locking Pole Ratchet.— A ratchet- 
winder for raising and lowering an arc- 
lamp on a pole, and provided with a self- 
locking attachment. 

Self-Oiling Bearings. — (1) Bearings pro- 
vided with automatic oilers. (2) Bear- 
ings which lubricate themselves when 
the shaft is rotating. . 

Self-Oiling Journal. — A journal pro- 
vided with automatic oilers. 

Self-Polarizing Relay.— A relay provided 
not only w T ith the ordinary set of magnet- 
izing coils, but also with an additional 
magnetizing coil for the magnetization of 
its tongue, so that the magnetism of the 
tongue is reversed when the current re- 
verses. 

Self-Recording Magnetometer. — A 
magnetometer which is capable of con- 
tinuously recording the daily and hourly 
variations of the earth's magnetic field. 

Self-Registering Tachometer. — A ta- 
chometer that provides a permanent re- 
cord of the varying speed of the machine 
to which it is connected. 

Self-Registering Wire-Gauge. — A ware- 
gauge arranged so as to register the dia- 
meter of the wire to be measured. 

Self-Regulating Dynamo.— A self-regu- 
lating generator. 

Self-Regulating Generator.— A gener- 
ator so wound as to automatically main- 
tain either a constant-current in the cir- 
cuit, or a constant difference of potential 
between its terminals, despite changes in 
the resistance of its load. 

Self-Regulating X-Ray Tube.— An X- 

ray tube provided with an automatic 
means of adjusting the degree of vacuum, 
and, therefore, the electric pressure at 
its terminals. 
Self-Regulation. — Any form of automatic 
regulation. 



SeL] 



91' 



[Sen, 



Self-Restoring Annunciator Drop.— 
An annunciator drop so arranged as to be 
capable of replacing itself, thus dispens- 
ing with a manual replacement. 

Self-Restoring Indicator.— (1) An in- 
dicator which will automatically resume 
its proper position. (2) A self -restoring 
drop or annunciator. 

Self- Starting Alternating - Current 
Motor. — (1) An alternating-current mo- 
tor which is capable of starting at any 
normal load. (2) A non-synchronous 
motor. 

Self-Starting Synchronous Motor.— 

An alternating-current synchronous mo- 
tor which is in any way enabled to be 
self-starting when connected with the 
mains. 

Self-Winding Clock. — A clock that is 
automatically wound at regular intervals 
by the action of a small electro-magnetic 
motor, contained within the clock, and 
operated by one or more voltaic cells con- 
cealed in the case of the clock. 

Semaphore. — A variety of visual signal 
apparatus employed in railroad block sys- 
tems. 

Semaphore Arm. — A movable arm of a 
signal apparatus employed in block sys- 
tems for railroads, for the purpose of in- 
dicating the condition of the road as re- 
gards other trains. 

Semaphore Indicator. — (1) An annunci- 
ator in which a gravity drop or shutter is 
caused to fall by the action of an electric 
cuirent, thus exposing a number or other 
signal back of the drop or shutter. (2) 
An indicator employed in a semaphoric 
signalling apparatus. (3) The movable 
shutter or drop employed in a semaphore. 

Semaphoric Electroscope. — A name 
sometimes given to a particular form of 
quadrant electroscope. 

Semi-Circular. — Of or pertaining to a 
semi-circle or half a circle. 

Semi-Circular Deviation of Mariner's 
Compass. — A term employed in contra- 
distinction to the quadrantal deviation 
for the deviation of a magnetic needle, 
due to the permanent magnetism of the 
ship, having its resultant in a horizontal 
plane, and changing sign twice in a 
complete revolution of the ship. 

Semi - Circular Error of Compass 
Needle. — The semi-circular deviation of 
the mariner's compass. 

Semi-Conductor. — A name applied to a 
group of bodies whose conducting power 
is, roughly, midway between that of good 
conductors and insulators. 



Semi-Incandescent Electric Lamp.— 
An electric lamp in which the light is due 
to the combined effects of an electric arc 
and of incandescence. 

Semi-Period.— (1) A half period. (2) The 
time occupied by a reversal or alterna- 
tion. 

Semi - Permanent Telegraph Line.— 

In military telegraphy, a line interme- 
diate in character and method of con- 
struction between a permanent line and a 
temporary line. 

Semi-Permeable Septum.— A septum 
which will permit the passage through it 
of a solvent, but not of the dissolved sub- 
stance. 

Sending End of Line.— The end of a 
telegraphic line from which the signals 
are sent. 

Sending Leg of Telegraphic Loop. — 
The wire of a telegraphic loop upon which 
messages are sent, as distinguished from 
the receiving leg. 

Sending Signaller. — The operator on a 
telegraphic line who is sending the sig- 
nals as distinguished from one at the 
other end who is receiving them. 

Sense of Magnetic Force. — A word some- 
times used for direction of magnetic 
force. 

Sensibility of Galvanometer.— (1) The 
readiness and degree to which the needle 
of a galvanometer will respond to the pas- 
sage .of an electric current through its 
coils. (2) The reciprocal of the current 
required to produce a definite small angu- 
lar deflection. (3) The deflection pro- 
duced by a definite small current strength. 
(4) The figure of merit of a galvanometer. 

Sensitive Flame. — A flame which alters its 
shape or size on the sounding of notes 
possessing the same frequency as that 
which it is capable of producing. 

Sensitive Discharge. — A thin, thread-like 
discharge that occurs between the termi- 
nals of a high-frequency induction coil. 

Sensitive Telephone. — A telephone that 
is able to properly respond to currents 
smaller than those ordinarily employed 
in telephone apparatus. 

Sensitive Tube. — A coherer. 

Sensitiveness of Wheatstone's Bal- 
ance. — The minimum change in the 
measured resistance which, under the con- 
ditions of the test and with the apparatus 
employed, is capable of either being de- 
tected, or of producing the unit of scale 
deflection in the galvanometer. 

Sent Current. — The current employed in 
transmitting a signal. 



Sep.] 



918 



[Sei\ 



Separable Conducting Cord Tip.— A 

telephone plug arranged for ready con- 
nection with, or disconnection from, a 
flexible conducting cord. 
Separable Iron Core. — An iron core 
which can be removed from the appara- 
tus in which it is used. 

Separate-Circuit Dynamo.— (1) A term 
sometimes employed for a self-exciting 
dynamo in which a special or separate 
armature circuit is connected to the fields. 
(2) A dynamo capable of supplying a plur- 
ality of separate circuits. 

Separate-Circuit Motor.— A term some- 
times applied to a motor whose armature 
is provided with two windings having two 
separate commutators, the main one be- 
ing supplied with the driving current. 

Separate-Coil Alternator.— An alterna- 
tor whose field magnets are excited by 
means of current taken from the coils of 
the armature after it has been commuted. 

Separate-Coil Dynamo-Electric Ma- 
chine. — A term sometimes used for a sep- 
arate-coil alternator. 

Separate-Coil Machine.— (1) A machine 
in which the armature coils are mechani- 
cally separated from each other, as dis- 
tinguished from a machine in which the 
coils are interlaced. (2; A djmamo-elec- 
tric machine in the armature of which 
there exists a separate coil or winding for 
the special purpose of exciting the field 
magnets. 

Separate Excitation. — The excitation of 
the field magnets produced by a source 
external to the machine. 

Separate Touch. — A phrase sometimes 
employed for magnetization by separate 
touch. 

Separately -Excited Alternator. — An 
alternator whose field magnets are sep- 
arately excited. 

Separately-Excited Dynamo-Electric 
Machine. — A dynamo-electric machine 
whose field coils are separately excited. 

Separately-Excited Field.— The field of 
a dynamo that receives its magnetizing 
current from a source outside or separate 
from the dynamo. 

Separator. — A corrugated and perforated 
insulating sheet of ebonite or other simi- 
lar substance, shaped so as to conform to 
the outlines of the plates of a storage bat- 
tery, and placed between them at suitable 
intervals in such a manner as to prevent 
their short-circuiting, but without imped- 
ing the free circulation of the liquid. 

Septum. — The porous partition of an en- 
dosmometer. 



Series and Magneto Dynamo-Electric 
Machine. — A compound-wound dynamo 
in which the armature circuit of a mag- 
neto-electric machine is connected with 
and excites the fine winding on the field 
magnets. 

Series-and-Separately -Excited Dyna- 
mo-Electric Machine.— A compound- 
wound dynamo whose field-magnet cores 
are wound with two separate circuits, one 
connected in series with the field magnets 
and the external circuit, and the other 
with some source by means of which it is 
separately excited. 

Series - and - Shunt - Wound Dynamo- 
Electric Machine, — A compound- 
wound dynamo whose field magnets are 
wound with two separate coils, one in 
series with the armature and the external 
circuit, and the other in shunt with the 
armature. 

Series-Arc Cut-Out.— A device for auto- 
matically providing a short-circuit past a 
faulty lamp in a series-connected circuit, 
so that the failure of a lamp to operate 
may not interfere with the operation of 
the rest of the lamps. 

Series Board. — A series-connected multi- 
ple telephone switchboard. 

Series Circuit. — A circuit in which the 
separate sources or separate electro-recep- 
tive devices, or both, are so placed that 
the current produced in it or passed 
through it passes successively through the 
entire circuit from the first to the last. 

Series-Connected Battery.— A battery 
of series-connected cells. 

Series-Connected Incandescent 
Lamps. — A number of lamps connected 
to a circuit in series and provided with a 
film or other similar cut-out, to prevent 
the failure of a single lamp from extm - 
guishing all the rest. 

Series-Connected Electro-Receptive 
Devices. — A number of electro- receptive 
devices connected to a circuit in series. 

Series-Connected Sources.— A number 
of separate sources so connected in series 
as to act as a single source. 

Series-Connected Translating Devices. 
A term sometimes used for series-con- 
nected electro-receptive devices. 

Series-Connected Voltaic Cells. — A 
number of voltaic cells so connected in 
series as to be capable of acting as a single 
source or battery. 

Series Connection. — Such a connection 
of a number of separate electric sources 
or electro-receptive devices or circuits 



Ser.] 



919 



[Ser 



that th'e current passes successively from 
the first to the last in the circuit. 

Series-Connection for Condensers.— 
The connection of a number of condensers 
in series. 

Series-Connection of Alternators. —The 
connection of two or more alternators in 
series. 

Series Converter.— A series transformer. 

Series Distribution. — A distribution of 
electric energy in which the receptive 
devices are placed one after another in 
succession upon a single conductor, ex- 
tending throughout the entire circuit 
from pole to pole. 

Series Dynamo. — A series-wound dynamo. 

Series Field-Terminals of Motor.— The 
terminals of a compound-wound motor 
which are connected to the ends of a series 
field-winding. 

Series Grouping of Armature Con- 
ductors. — (1) A two-circuit multipolar 
winding. (2) A winding for a multipo- 
lar armature in which only two paths 
are provided for the current between the 
brushes. 

Series Incandescent Lamp.— An incan- 
descent lamp suitable for use in a series 
circuit. 

Series Incandescent Lighting System. 
A system of incandescent lighting in 
which the lamps are connected in series, 
as distinguished from a multiple system 
in which they are connected in parallel. 

Series Motor.— (1) A motor suitable for use 
in a series circuit. (2) A series-wound 
motor. 

Series-Multiple. — A series-multiple con- 
nection. 

Series-Multiple Car-Controller. — A 
controller provided for starting and stop- 
ping a double motor car, for varying its 
speed, or the torque of its motors, by con- 
necting the motors either in series or in 
parallel with or without resistances. 

Series-Multiple Circuit. — A compound 
circuit in which a number of separate 
sources, or separate electro-receptive 
devices, or both, are connected in a 
number of separate groups in multiple 
arc, and these separate groups sub- 
sequently connected in series. 

Series-Multiple-Connected Electro- 
Receptive Devices. — A connected sys- 
tem in which a number of separate elec- 
tro-receptive devices are joined in parallel 
in separate groups, and all of these groups 
subsequently connected in series. 

Series-Multiple-Connected Sources.— 
The connection of a number of separate 



electric sources so as to form a single 
source, in which the separate sources are 
connected in a number of separate mul- 
tiple groups or circuits, and these groups 
or circuits separately connected together 
in series. 

Series-Multiple-Connected Translat- 
ing Devices. — Series-multiple-connected 
electro-receptive devices. 

Series-Multiple Connection.— Such a 
connection of a number of separate electro- 
receptive devices that the devices are 
placed in multiple groups or circuits and 
these separate groups afterwards con- 
nected with one another in series. 

Series-Multiple Switchboard.— A tele- 
phone switchboard, in which a subscriber's 
jacks are connected in series, while plug 
connections are made in parallel or across 
the circuit. 

Series-Parallel Controller. — A series- 
multiple car-controller. 

Series Tranformer.— A term sometimes 
applied to a converter whose primary coil 
is connected in series with the primary 
coils of other similar transformers in the 
primary circuit. 

Series Turns of Dynamo - Electric 
Machine. — The magnetizing field-mag- 
net coils of a dynamo that are connected 
in series with the armature circuit. 

Series Winding. — A winding of a dynamo 
electric machine in which a single set of 
magnetizing coils are placed on the field- 
magnet cores and connected in series with 
the armature and the external circuit. 

Series-Wound Dynamo-Electric Ma- 
chine. — A dynamo-electric machine in 
which the field circuit and the external 
circuit are connected in series with the 
armature circuit, so that the armature 
current passes through the field winding 
into the external circuit. 

Series- Working of Dynamo-Electric 
Machines. — Such a coupling of several 
dynamo-electric machines as will deliver 
in series the current supplied by them. 

Series-Wound Field. — The field of a dyn- 
amo in which the armature current passes 
through the magnetizing coil. 

Series-Wound Laminated Synchro- 
nous Motor. — A series-wound syncho- 
nous motor provided with a laminated 
core. 

Series-Wound Motor .—A motor provided 
with a series-wound field. 

Serrated Lightning Arrester.— A term 
sometimes applied to a saw-tooth light- 
ning arrester. 



Sei\] 



920 



[She, 



Service. — A conductor or set of conductors 
supplying electric energy from electric 
mains to the premises of a consumer. 

Service Block.— (1) A block connected 
with service wires. (2) A block for sup- 
porting and connecting service wires. 

Service Conductors. — Service wires. 

Service Line.— (1) A service wire. (2) 
In telephony, a line or circuit connecting 
a switchboard, with a subscriber. 

Service Tube.— A tube provided for the 
introduction of service wires. 

Service Wires.— (1) The wires which lead 
into a building and which are connected to 
the supply mains or supply circuit. (2) 
The wires through which service is given 
to a consumer. (3) Delivery wires. 

Serving Mallet.— A tool employed for 
placing the tarred yarn serving on a cable 
splice. 

Serving of Cable.— The bedding of tape, 
yarn, jute or compound, in a cable as dis- 
tinguished from the core or the sheathing. 

Serving Tool.— A tool employed in placing 
the serving on a cable. 

Seven-Point Jacks.— In a multiple tele- 
phone switchboard, jacks having each 
seven different points of contact. 

Sextant. — An optical device consisting of 
a fixed and movable mirror, employed for 
measuring the angular distance between 
any two objects. 

Sextaplex Telegraph.— A general term 
embracing the apparatus used in sex- 
taplex telegraphy. 

Sextaplex Telegraphy.— A system of 
telegraphy whereby six distinct messages 
can be simultaneously transmitted over 
the same line, three in one direction and 
three in the opposite direction. 

Sextaplex Transmission.— Transmitting 
intelligence by means of sextaplex teleg- 
raphy. 

Sextipolar. — Possessing six poles. 

Sextipolar Dynamo.— A dynamo posses- 
sing a sextipolar field. 

Sextipolar Field.— A field produced by 
six magnet poles. 

Sextuple Telegraph. — A general term for 
the appratus employed in sextuple teleg- 
raphy. 

Sextuple Telegraphy.— A system of 
telegraphic communication in which six 
separate messages are simultaneously sent 
over a line in the same direction. 

Sextuple Transmission. — The transmis- 
sion of intelligence by sextuple teleg- 
raphy. 



Sextuply Re-Entrant. — An armature 
provided with six separate conducting 
paths or windings, eacli of wmich is inde- 
pendently re-entrant. 

Shackle Insulator.— A term applied to 
any form of insulator used for shackling 
a wire, as distinguished from an insulator 
which merely supports a wire. 

Shackling a Wire.— (1) Inserting an insu- 
lator between the two ends of a cut wire. 
(2) Securing the end of a telegraph or 
telephone wire to a shackle. 

Shaded.— (1) Cut off or screened from the 
effects of an electro-static or magnetic 
field. (2) Screened. 

Shaded-Pole Motor.— An alternating- 
current motor in which the rotary effort 
is obtained by placing short circuited 
coils on a portion of the polar faces. 

Shade-Holder. — A ring or circle clamped 
to the socket of an incandescent lamp for 
supporting a shade. 

Shading Coil of Alternating-Current 
Motor. — A conducting coil or loop cover- 
ing part of one or more poles in an alter- 
nating-current motor, for the purpose of 
retarding the magnetic flux through that 
portion of the pole, and thereby exerting 
a tangential drag on the armature. 

Shadow, Electric. — A term sometimes 
used for molecular shadow. 

Shadowgram. — A term sometimes used 
for radiograph. (Not in general use.) 

Shadowgraph. — A word frequently used 
for radiograph. 

Shadow Photometer.— A photometer in 
which the intensity of the light to be 
measured is estimated by a comparison of 
the distance at which it and the standard 
light produce shadows of the same inten- 
sity. 

Shallow- Water Submarine Cable.— A 

submarine cable intended for use in shal- 
low water, where the cable is apt to be 
injured by friction against a rocky bot- 
tom, and therefore provided with heavier 
armor than a deep-sea cable. 

Shear. — A strain consisting of an extension 
in one direction combined with an equal 
compression perpendicular thereto. 

Shearing Stress.— A stress producing a 
shear. 

Sheathing of Cable.— The armor or pro- 
tecting covering employed for surround- 
ing the core of a cable. 

Sheathing Wires.— The metallic wires 
which form the armor of a submarine 
cable. 



She.] 



921 



[Slio. 



Shed of Insulator.— A petticoat or in- 
verted cone of a telegraph insulator. 

Sheer. — The curve which the line of ports 
or the deck of a ship presents to the eye, 
when observed from one side. 

Sheet Lightning. — A variety of lightning 
flash, unaccompanied by thunder audible 
to an observer, in which the surfaces of 
clouds are illumined. 

Shell of Arc-Lanip. — The outside casing 
of an arc-lamp. 

Shell of Commutator.— A term some- 
times employed for the commutator form, 
separated from its shaft. 

Shell of Fixture.— A light ornamental 
metallic casing covering some part of an 
electrolier. 

Shell Transformer.— (1) A transformer 
whose primary and secondary coils are 
laid on each other, and the iron core is 
then wound through and over them, so as 
to completely enclose them. (2) A form 
of iron-clad transformer. 

Shellac. — A resinous substance obtained 
from the roots and branches of certain 
tropical plants, which possesses high insu- 
lating powers, and high specific inductive 
capacity. 

Shifting Magnetic Field.— (1) A magnet- 
ic field whose lines of magnetic force are 
changing position with respect to the 
axis of the magnet pole from which they 
emanate. (2) A rotary magnetic field. 

Shifting of Phase of Alternating Cur- 
rent. — In an alternating-current circuit 
the changes in the phase relation of cur- 
rent strength to impressed E. M. F. de- 
pending upon variations in the frequency 
or in the impedance. 

Shifting of Spot of Light.— Any move- 
ment of a spot of light on a scale causing 
that spot to move away from its true zero 
position, produced by causes other than 
those acting during the proper operation 
of the instrument. 

Shifting Zero. — (1) A zero that changes or 
shifts its position. (2) A false zero in 
measuring instruments. 

Ship Dynamometer. — A dynamometer 
employed on board a cable ship for the 
purpose of indicating the strain on a 
grappling rope or on a cable. 

Ship Return-Circuit System.— A name 
applied to a single- wire system or form of 
circuit in which the hull of the ship forms 
the return wire. 

Shock. — (1) Objectively, a concussion or 
blow. (2) Subjectively, a violent nervous 
stimulus. 



Shock, Electric. — A physiological shock 
produced in an animal by an electric dis- 
charge. 

Shoe of Contact for Street Railway.— 
The metallic contact piece which rubs 
against a surface rail or conduit rail in a 
street railway system. 

Shoe Plug. — A form of sliding contact- 
plug for insertion in a jack of a telephone 
switchboard. 

Shore-End of Telegraphic Cable.— (1) 
A shallow- water section of submarine 
cable. (2) The end of a submarine cable 
landed on a shore. 

Short Arc System of Electric Light- 
ing. — A system of electric lighting in 
which short voltaic arcs are maintained 
between carbon electrodes. 

Short Circuit.— (1) A shunt or by-path of 
negligible or comparati vefy small resist- 
ance, placed around any part of an 
electric circuit through which so much of 
the current passes as to virtually cut out 
the parts of the circuit to which it acts as 
a shunt. (2) An accidental direct con- 
nection between the mains or main ter- 
minals of a dynamo or system producing 
a heavy overload of current. (3) To cut 
out of circuit by a short conductor. (4) 
To accidentally produce a short circuit. 

Short-Circuit-Key. — A key which in its 
normal position short-circuits a galvan- 
ometer, or other device with which it is 
connected. 

Short-Circuited.— (1 ) Placed on a short- 
circuit. (2) Cut out by means of a short- 
circuit. 

Short-Circuited Conductor.— A con- 
ductor which has a short-circuit estab- 
lished past it. 

Short Circuiting.— (1) Cutting out of 
circuit by means of a short-circuit. (2) 
Establishing a direct connection between 
the terminals of a source or device, or 
between mains connected to them. 

Short-Circuiting a Dynamo-Electric 
Machine. — (1) Cutting out the external 
circuit of a dynamo by means of a short- 
circuit. (2) Connecting the poles or ter- 
minals of a dynamo by a circuit of negli- 
gibly small resistance. (3) Greatly over- 
loading a constant-potential machine, and 
underloading a constant-current ma- 
chine. 

Short-Circuiting Plug.— (1)A plug which 
when inserted in its receptacle short cir- 
cuits the device connected therewith. 
(2) A plug employed in short-circuiting a 
coil or other resistance. 

Short-Closed Circuit.— In a series dis- 



Sho.] 



922 



[Shu, 



tribution circuit, the condition of having 
short-circuited devices, as distinguished 
from a long-closed circuit from which all 
short circuits have been removed. 

Short-Coil Magnet.— A magnet whose 
magnetizing coil consists of a few turns 
of short thick wire. 

Short Connection of Two-Circuit 
G r a m m e-W indin g.— A form of 
Gramme winding in which the circuits 
from brush to brush consist of conduc- 
tors influenced by all the poles, so that the 
E. M. F.'s generated in the two circuits 
are necessarily equal. 

Short-Connection Two-Circuit Arma- 
ture Winding. — (1) Such a two-circuit 
winding that in each circuit between the 
brushes electromotive forces are induced 
by each and all the poles of the field 
frame. (2) Such a type of two-circuit 
winding as connects coils together lying 
in adjacent fields. 

Short-Core Electro-Magnet.— An elec- 
tro-magnet provided with a short core. 

Short-End of Quadruplex Battery. — 

The end of a quadruplex battery, the 
smaller portion of which is always in 
circuit, as opposed to the end of the extra 
battery thrown in circuit by the depres- 
sion of the increment key. 

Short-Shunt Compound-Winding.— A 

compound winding of a dynamo-electric 
machine in which the shunt coil is connect- 
ed directly, or through resistance, with 
the armature brushes, as distinguished 
from a long-shunt compound-winding. 

Short-Shunt Compound-Wound Dy- 
namo - Electric Machine. — A com- 
pound-wound dynamo whose field-magnet 
coils form a shunt to the armature only, 
as distinguished from a shunt to the 
armature and series coils combined. 

Short-Sightedness.— (1) The condition of 
the eye in which distinct images are 
formed of those objects only which are 
near to the eye. (2) Myopia. (3) The 
condition of sight pertaining to an elon- 
gated eyeball. 

Short Timber. — A term applied to 
timber that has been improperly subjected 
to preservative processes, and has thereby 
been rendered brittle. 

Short Wire Repeater.— A repeater be- 
tween a duplex or quadruplex and a 
branch office wire. 

Shower-Bath, Electric— A device for 
carrying an electric charge to the body of 
a patient by the falling water. 

Shunt. — An additional, or by-path estab- 



lished for the passage of an electric cur- 
rent or discharge. 
Shunt. — To establish an additional, or by- 
path for the passage of an electric current 
or discharge. 

Shunt - and - Separately - Excited Dy- 
namo - Electric Machine.— A com- 
pound-wound dynamo in which the field 
is excited both by means of a shunt to the 
armature circuit, and by a current pro- 
duced by a separate source. 

Shunt Bell, Electric— An electric bell 
whose magnetizing coils are connected to 
the line wire in shunt. 

Shunt Breaking Resistance. —A re- 
sistance for insertion in the field of a 
shunt dynamo, before breaking its circuit, 
to prevent the production of a dangerously 
powerful induced pressure. 

Shunt - Circuit.— (1) A derived circuit. 

(2) A branch or additional circuit, pro- 
vided in any part of a circuit, through 
which the current branches or divides, 
part flowing in the original circuit and 
part through the new branch or shunt. 

(3) A circuit for diverting or shunting a 
portion of the current. 

Shunt Coil. — A coil placed in a shunt 
circuit. 

Shunt Dynamo. — A shunt- wound dy- 
namo-electric machine. 

Shunt-Field Terminals of Motor.— The 
terminals of the shunt field coils of an 
electric motor. 

Shunt for Ammeter. — (1) A shunt coil con- 
nection in multiple with the coils of an 
ammeter for the purpose of changing the 
value of the readings. (2) A reducteur. 

Shunt Spool. — A spool or coil of insulated 
wire placed in a shunt circuit. 

Shunt Street-Car Motor. — A shunt- 
wound car motor. 

Shunt Ratio. — (1) The ratio existing 
between a shunt and the circuit it shunts. 
(2) The ratio existing between the total 
current strength and the current strength 
in the branch to which the shunt is ap- 
plied. 

Shunt Rheostat. — A rheostat placed in a 
shunt-circuit. 

Shunt Turns of Dynamo.— The ampere 
turns in the shunt circuit of a shunt- 
wound or compound-wound dynamo. 

Shunt Winding. — A term sometimes em- 
ployed for the shunt field coils on a shunt- 
wound dynamo or motor. 

Shunt- Wound Dynamo-Electric Ma- 
chine. — A dynamo - electric machine 
whose field-magnet coils are placed in 



Shu. 



923 



[Sie. 



shunt with the armature circuit, so that 
only a portion of the current generated 
passes through the field-magnet coils, but 
all the difference of potential of the 
armature acts at the terminals of the 
field circuit. 

Shunt-Wound Field.— The field of a 
dynamo in which the field-magnet coils 
are placed in shunt with the armature 
and external circuit. 

Shunt-Wound Motor. — A motor whose 
field-magnet coils are placed in shunt to 
the armature circuit. 

Shunted.— Provided with a shunt. 

Shunting. — Providing with a shunt. 

Shunting Air-Gap. — (1) An air-gap in a 
circuit placed around a galvanometer or 
other instrument, for the purpose of pro- 
tecting it from the effects of a powerful 
disruptive discharge. (2) An air-gap 
shunt in a magnetic circuit. 

Shutter Apparatus. — In a system of 
visual telegraphy, an apparatus for sud- 
denly displaying and obscuring a light 
by means of hand-controlled shutters. 

Shutter Indicator Armature.— The ar- 
mature of an electro-magnet so arranged 
that when released it displays an in- 
dicator on an annunciator. 

Shuttle Armature.— (1) A variety of 
drum armature in which a single coil of 
wire is wound in an H-shaped groove 
formed in a bobbin-shaped core. (2) The 
old form of Siemens' armature. 

Shuttle-Wound Armature. — An ar- 
mature whose coils are placed on its core 
by first winding the wire on a shuttle and 
passing the same through the opening or 
gap provided for the coil. 

Side A of Quadruplex Table.— That 
side of a quadruplex system which is 
worked by means of reversed currents. 

Side B of Quadruplex Table.— That side 
of a quadruplex system which is worked 
by means of strengthened currents. 

Side-Bar Suspension of Motor. — In a 
street railway car truck, a method of sup- 
porting the motors which consists in em- 
ploying a pair of bars or light girders 
mounted on springs parallel to the side 
frames and supporting the motors from 
these bars. 

Side Bracket. — A particular form of 
single insulator bracket. 

Side Commutator. — The commutator of 
a dynamo-electric machine placed on the 
side of the revolving armature. 

Side Current. — A term applied by Hertz 
to the current produced in the side cir- 
cuit of a micrometer. 



Side Flash. — A sparking or lateral dis- 
charge taking place from the sides of a 
conductor through which an impulsive 
rush of electricity is passing. 

Side-Lights, Electric— Red or green 
lanterns placed on permanent fixtures on 
either side of a ship. 

Side of Three-Wire System.— (1) A term 
applied to the positive or negative con- 
ductors or leads in the three-wire system 
of distribution. (2) The positive or the 
negative half of a three- wire system. 

Side Pole. — A trolley-wire pole mounted 
at the side of a track as distinguished from 
a central pole. 

Side Pole Line.— An aerial line supported 
from poles placed on the side of a street 
or road, as distinguished from a centre 
pole line or from one supported from 
poles placed in the centre of the street or 
road. 

Side-Pole Trolley-Line Construction. 

A method for the suspension of aerial 
trolley lines in which the trolley and feed 
wires are suspended from poles placed on 
one side of the street or road. 

Side Suspension of Motor.— A side-bar 
suspension of a motor in a truck. 

Side Telegraphic Repeater.— A tele- 
graphic repeater which operates adja- 
cent circuits from a main line. 

Sides of Three- Wire System.— (1) The 
portions of a three-wire s} T stem which have 
respectively positive and negative poten- 
tials. (2) The positive and negative por- 
tions of a three-wire system. 

Siderial.— Of or pertaining to the stars. 

Sidero-Magnetic— A term proposed for 
ferro-magnetic. 

Siemens Armature Electro-Magnetic 
Bell. — A form of electro-magnetic bell, 
the movements of whose armature are 
obtained by the reversal of polarity that 
occurs when alternating currents are 
passed through a single-coil Siemens ar- 
mature. 

Siemens Differential Voltameter. — 
A form of voltameter employed by 
Siemens for determining the resistance 
of the platinum spiral used in his electro- 
pyrometer. 

Siemens Electro - Dynamometer. — A 
form of galvanometer employed for the 
measurement of electric currents. 

Siemens Electro-Pyrometer.— An ap- 
paratus for the determination of temper- 
ature by the measurement of the electric 
resistance of a platinum wire exposed to 
the source of heat, the temperature of 
which is to be measured. 



Sic] 



924 



[Sim. 



Siemens-Halske Voltaic Cell.— A zinc- 
copper couple whose elements are em- 
ployed with dilate sulphuric acid and a 
saturated solution of copper sulphate re- 
spectively. 

Siemens Water Pyrometer.— A pyro- 
meter employed for determining the tem- 
perature of a furnace or other intense 
source of heat, by the increase in the tem- 
perature of a known weight of w T ater to 
which a metal cylinder of a given weight 
has been put, after exposure for a given 
time to the source of heat to be measured. 

Signal Arm. — A semaphore arm. 

Signal-Service System for Electric 
Railroad. — A system of electric signals 
used on railroads for ascertaining the 
condition of the road, sending instruc- 
tions to engineers, and conveying intelli- 
gence generally from stations along the 
road to running trains. 

Sight-Feeding Oiler. — A glass oil-cup 
which permits the visible feeding of lu- 
bricating oil to the journal bearings. 

Signature. — In telegraphy, a name of the 
sender of a message as it appears upon the 
same. 

Silence Telephone Cabinet.— A long- 
distance telephone cabinet. 

Silent. — A switch device for preventing 
the action of an electric alarm by short- 
circuiting it. 

Silent Discharge. — A name sometimes 
given to a convective discharge, in order 
to distinguish it from the more noisy dis- 
ruptive discharge. 

Silhougraph. — A word proposed for ra- 
diograph. 

Silver Bath. — An electrolytic bath con- 
taining a readily electrolyzable salt of sil- 
ver, and a plate of silver acting as the 
anode, placed in the liquid near the 
object to be coated which forms the 
cathode. 

Silver Chloride Voltaic Cell.— A zinc- 
silver couple immersed in electrolytes of 
sal-ammoniac or common salt, and silver 
chloride, respectively. 

Silver-Palladium Alloy.— An alloy of 
silver with palladium and other metals, 
employed for the hair-springs, escape- 
ments and balance-wheels of watches, on 
account of its non-magnetic properties. 

Silver Plating. — Covering the surfaces of 
the baser metals with an adherent coating 
of silver by the electric current. 

Silver Voltameter.— A voltameter in 
which the quantity of electricity passing is 
determined by the weight of silver depos- 
ited. 



Silvered Plumbago.— Powdered plum- 
bago covered with metallic silver, for use 
in the metallization of objects to be elec- 
tro-plated. 

Silurus Electricus.— The electric eel. 

Similars. — Conductors in the secondary 
winding of an induction machine which 
are similar to each other in respect to 
the magnitude of their induced electro- 
motive forces at any instant, and sym- 
metrically disposed relatively to the ro- 
tating poles. 

Simple Alternating-Currents.— (1) Sin- 
usoidal-alternating currents. (2) Simple- 
harmonic currents. 

Simple Arc— A voltaic arc formed be- 
tween two electrodes. 

Simple Circuit.— A term sometimes em- 
ployed for a circuit containing a single 
electric source and a single electro-recep- 
tive device. 

Simple Electric Candle Burner.— A 

plain-pendant electric burner. 

Simple-Harmonic Currents.— (1) Cur- 
rents whose flow is variable both in 
strength and duration, and in which the 
quantity of electricity passing by any sec- 
tion of conductor may be represented by 
a simple-harmonic curve. (2) A current 
of such a nature that the continuous va- 
riation of the flow of electricity past any 
area of cross-section of the conductor, or 
the continuous variations in electromotive 
force, may be expressed by a simple-har- 
monic curve. 

Simple-Harmonic Curve.— The curve 
which results when a simple-harmonic 
motion in one line is compounded with 
uniform motion in a straight line at right 
angles thereto. 

Simple-Harmonic Electromotive 
Forces. — Electromotive forces which 
vary in such a manner as to produce 
simple-harmonic currents ; or, electromo- 
tive forces whose variations can be cor- 
rectly represented by a simple-harmonic 
curve. 

Simple-Harmonic Motion.— (1) Motion 
which repeats itself at regular intervals 
in one line, taking place backwards or 
forwards, and which is the orthogonal 
projection of the path of a point moving 
uniformly in a plane circle upon a diame- 
ter of the circle. (2) Motion which is a 
simple-periodic function of the time. (3) 
Simple-periodic motion. 

Simple-Harmonic Variation.— A varia- 
tion of current or electromotive force 
which takes place in accordance with 
simple-harmonic Jaw. 



Sim.] 



925 



[Sin. 



Simple Immersion..— A term sometimes 
employed for an electrolytic deposit ob- 
tained by merely dipping a metal in a so- 
lution of a metallic salt. 

Simple Magnet. — A simple magnetized bar. 

Simple Magnetic Shell. — A magnetic 
shell whose strength is everywhere the 
same. 

Simple -Periodic Currents. — A term 
sometimes used for simple-harmonic cur- 
rents. 

Simple-Periodic Curve.— A simple-har- 
monic curve. 

Simple-Periodic Electromotive Force. 
A simple-harmonic electromotive force. 

Simple-Periodic Motion.— Simple-har- 
monic motion. 

S i m p 1 e-Periodic Variation.— Simple- 
harmonic variation. 

Simple Radical.— (1) An unsaturated 
atom with its bond or bonds free. (2) A 
single unsaturated atom, as distinguished 
from an unsaturated group of atoms. 

Simple Rigidity. — (1) In an isotropic 
body the ratio of shearing stress to the 
resulting shear. (2) Resistance to shear- 
ing. (3) In an isotropic body the edges 
of a unit cube to which tangential shear- 
ing stresses are applied, the ratio of the 
tangential force to the angular distortion 
effected in the cube. 

Simple Shunt. — A coil arranged as a 
shunt, and unprovided with an iron core. 

Simple-Sine Motion. — A term sometimes 
employed for simple-harmonic motion. 

Simple Voltaic Cell. — A term sometimes 
used for a single-fluid cell. 

Simplex Telegraph.— A general term 
embracing the apparatus employed in 
simplex telegraphy. 

Simplex Telegraphy .—A system of teleg- 
raphy in which a single message only can 
be sent over the line wire. 

Simplex Working. — (1) Transmitting 
messages by simplex telegraphy. (2) A 
word sometimes employed for simple 
telegraphic transmission: 

Sims-Edison Torpedo.— A special form 
of torpedo in which electricity is both the 
propelling and directing power, but the 
electric source is situated outside the tor- 
pedo, and is connected with the same by 
a light cable. 

Sine Galvanometer.— A galvanometer 
whose deflecting coil is placed in a verti- 
cal plane movable about a vertical axis, 
so that it can be made to follow the mag- 
netic needle in its deflections. 

Sine Law. — (1) A law of magnitude de- 



fined by the sines of angles. (2) A mag- 
nitude which follows the sines of succes- 
sive angles. 

Single Brush-Rocker Arm.— A device 
by means of which a single pair of brushes 
are so situated on a dynamo or motor as 
to be capable of being readily shifted into 
the desired position on the commutator 
cylinder. 

Single-Brush Yoke. — A term sometimes 
used for single brush-rocker arm. 

Single-Circuit. — An undivided circuit. 

Single-Contact Carbon Telephone.— 
A form of microphonic telephone trans- 
mitter, in which a single contact is em- 
ployed. 

Single-Contact Key.— Any key which 
makes a single contact only. 

Single-Cord Multiple-T elephone 
Switchboard. — (1) A multiple telephone 
switchboard employing a single conduct- 
ing cord in establishing connections. 
(2) A multiple-telephone switchboard in 
which the circuits are all ground-return- 
circuits, and the subscribers' jacks are all 
connected in series. 

Single-Cord Switchboard.— (1) A tele- 
phone switchboard in which an inter-con- 
nection between two subscribers is ef- 
fected through a single cord. (2) A tele- 
phone switchboard in which each line 
terminates in a plug. 

Single-Cord Telephone Switchboard. 
A telephone switchboard employing 
single conducting cords. 

Single-Cup Insulator. — An insulator 
consisting of a single inverted cup. 

Single Curb. — A device for increasing the 
speed of telegraphic signalling by ridding 
the line of its previous charge by means 
of a single reversed current sent through 
it after each signal, before connecting to 
the ground, as distinguished from a 
double curb in which a succession of two 
reversed currents follow each signal. 

Single-Curb Signalling.— Signalling by 
means of a single curb. 

Single-Current Signalling.— Signalling 
by means of makes or breaks in the cir- 
cuit of a single current. 

Single-Current Closed-Circuited Sig- 
nalling. — A method of telegraphic sig- 
nalling in which the line circuit is nor- 
mally closed, being only broken by the 
sending operator, while the current in the 
circuit has only one direction. 

Single-Current Key.— A key employed 
in single-current signalling. 

Single-Current Open-Circuit Signal- 



Sin,] 



926 



[Sin, 



ling. — A method of telegraphic signalling 
in which the main-line batteries are fixed 
at each station, and are in circuit only 
when signalling. 

Single-Current Telegraphic Working. 
A term sometimes used for single-current 
signalling. 

Single-Current Translator.— A tele- 
graphic translator suitable for use in 
single-current working. 

Single-Curve Suspension.— (1) A sus- 
pension suitable for the support of a trol- 
ley wire at a single curve in the line, or 
single-track curve. (2) A form of suspen- 
sion having a single curved holder or 
support. 

Single-Curve Trolley Hanger.— (1) A 
hanger supporting a single curve wire or 
single-track curve wire. (2) A trolley 
hanger supported by a single curved 
holder. 

Single-Curve Trolley-Suspension.— 
(1) Suspension of a trolley wire by a single- 
curve trolley-hanger. (2) A single-track 
trolley-suspension at a curve in the track. 

Single-Coil Field Dynamo.— A dynamo 
whose magnetic field is obtained from a 
single magnetizing coil. 

Single Field-Coil Multipolar Dynamo. 

A multipolar dynamo having a single 
field coil on a single core provided with a 
plurality of polar projections. 

Single-Fluid. — Pertaining to the single- 
fluid hypothesis of electricity or magnet- 
ism. 

Single -Fluid Hypothesis of Elec- 
tricity. — A hypothesis which endeavors 
to explain the cause of electrical phenom- 
ena by the assumption of the existence of 
a single electric fluid. 

Single-Fluid Voltaic Cell. — A voltaic 
cell in which but a single fluid or electro- 
lyte is used. 

Single-Focus X-Ray Tube. — An X-ray 
tube suitable for use in connection with 
pulsatory currents, and provided with a 
single deflecting plate or anticathode op- 
posite the cathode. 

Single-Line Repeater. — In telegraphy, a 
repeater from a single circuit into an- 
other. 

Single-Liquid Voltaic Cell.— A single- 
fluid voltaic cell. 

Single-Loop Armature. — An armature 
consisting of a closed conducting circuit 
containing a single loop, so placed as to 
be capable of revolving in a magnetic 
field, as to cut its magnetic flux. 

Single-Magnet Dynamo-Electric Ma- 



chine. — A term sometimes used for a 
single field-coil dynamo. 
Single-Needle Telegraphy.— A system 
of telegraphy in which the transmitted 
signals are received by the movements of 
a vertical needle suitably suspended be- 
fore a dial. 

Single-Pair Brush-Rocker.— A term 
sometimes used for single-pair brush yoke. 

Single-Pair Brush Yoke.— A device for 
so holding a single pair of collecting 
brushes of a dynamo-electric machine 
that they can be readily moved or rotated 
on the commutator cylinder. 

Single-Pair Yoke.— A single-pair brush 
yoke. 

Single Peg. — A peg provided with but a 
single contact. 

Single Phase.— (1) Uniphase. (2) Mono- 
phase. (3) Pertaining to ordinary alter- 
nating currents in a simple alternating- 
current system as distinguished from 
multiphase currents. 

Single-Phase Alternating Current. — 
A uniphase alternating current. 

Single-Phase Alternator.— An alter- 
nator capable of producing simple or 
single-phase currents. 

Single-Phase Armature Windings. — 
Windings employed on the armature of a 
single-phase alternator. 

Single-Phase Armature Windings. — 
Armature windings of single-phase gen- 
erators. 

Single-Phase Asynchronous Motor. — 
A single-phase alternating-current motor 
capable of running otherwise than in 
synchronism with the current supplied to 
it from the circuit. 

Single-Phase Bar - Armature Wind- 
ings. — Such a bar armature winding of 
an alternator as is capable of producing 
single-phase currents. 

Single-Phase Dynamo.— A single-phase 
alternator. 

Single-Phase Generator. — A single- 
phase alternator. 

Single-Phase Motor. — A uniphase 
motor. 

Single-Phase Induction Motor.— An 
induction motor operated by uniphase 
currents. 

Single-Phase Induction Motor.— An in- 
duction motor operated or intended to be 
operated on a single-phase alternating- 
current circuit. 

Single-Phase Synchronous Motor.— A 
synchronous motor capable of being oper- 
ated by uniphase currents. 



Sin.] 



927 



[Sin. 



Single-Phase Transformer.— A transfor- 
mer suitable for supplying or transform- 
ing single -phase currents. 

Single-Phase Winding.— A single-phase 
armature winding. 

Single-Phaser.— (1) An alternating-cur- 
rent generator of single-phase currents. 
(2) A uniphaser. 

Single-Pole Cut-Out.— A cut-out by 
means of which the circuit is broken or 
cut in one of the two leads only. 

Single-Pole Safety-Fuse.— A single pole 
cut-out operated by a safety fuse. 

Single-Pole Switch.— A switch which 
opens or closes a circuit at one of its 
leads only. 

Single-Pole Telephone Receiver.— (1) 
A bar-magnet telephone with a coil on 
one end of the bar. (2) A telephone re- 
ceiver in which only one magnetic pole is 
presented to the diaphragm, as distin- 
guished from a receiver in which a pair of 
poles, each surrounded by a coil, is pre- 
sented to the diaphragm. 

Single-Pole Telephone Switch. — A 
single-pole switch employed on a tele- 
phone circuit. 

Single Pull-Off.— (1) A trolley pull-off 
supported on a single-curve holder. (2) 
A single-curve pull-off. (3) A trolley 
pull-off on a single-track curve. 

Single-Reduction.— (1) Having but a 
single gear wheel for reducing speed. 
(2) A gearing in which but a single re- 
duction of speed takes place as opposed 
to a double gearing in which two separate 
reductions are effected. 

Single-Reduction Street-Car Motor.— 
A street-car motor which requires a 
single reduction gear connected with the 
car axle to reduce the motion of the car 
axle as opposed to a motor geared with 
the car axle through two successive gear 
wheels and therefore one intermediate 
shaft. 

Single-Reflection Tube.— A term some- 
times applied to an X-ray tube contain- 
ing but a single deflecting plate or. anti- 
cathode. 

Single-Shackle Insulator.— (1) A form 
of insulator employed in shackling a 
single wire. (2) A form of single shackle 
to which two wires can be fastened at 
different points and left insulated. 

Single-Shed Insulator. — An insulator 
provided with a single inverted cup. 

Single-Stroke Electric Bell.— An elec- 
tric bell that gives a single stroke only for 
each closure of the circuit. 



Single-Throw Switch. — A switch having 
but two positions, one for opening, and the 
other for closing the circuit it controls, 
as distinguished from a double-throw 
switch. 

Single-Touch. — A phrase sometimes em- 
ployed for magnetization by single 
touch. 

Single-Track Bracket Trolley-Suspen- 
sion. — A form of single-track trolley- 
wire suspension, in which a bracket is 
supported from a pole placed on one side 
of the street. 

Single-Trolley System. — A trolley 
system in which a single conducting 
over-head wire is employed, the track 
and ground being used for a return. 

Single-Trolley System Electric-Rail- 
road. — An electric railroad operated by a 
single trolley. 

Single-Truck Car.— A car whose body is 
supported on a single truck. 

Single-Valued Function. — A function 
which has only a single value for each 
value of the variable. 

Single- Wire Cable.— A cable whose core 
contains a single conducting wire only. 

Single-Wire Circuit. — A term sometimes 
used for a grounded circuit. 

Single- Wire Line. — A term sometimes 
used for a single-wire circuit. 

Single -Wire Multiple Telephone 
Switchboard.— (1) A single-cord mul- 
tiple telephone switchboard. (2) A 
switchboard connecting ground-return 
subscribers' lines, the jacks of which are 
all in series in each line. 

Single- Wire Spring- Jack. —A spring- 
jack suitable for use in a single-wire 
switchboard. 

Single -Wire Switchboard. — (1) A 

switchboard devoted to the connections 
of a single line with various sets of appa- 
ratus. (2) A telephone switchboard con- 
nected to ground-return circuits. 

Single -Wire System for Electric 
Light Leads. — A term sometimes em- 
ployed for a ground-return electric light 
circuit. 

Single-Wire Telephone Switchboard. 
A form of telephone switchboard connect- 
ing ground-return circuits. 

S i ng 1 e-Wound Gramme Ring. — A 
Gramme ring provided with a single 
winding, the number of whose coils is a 
multiple of the number of poles, and the 
number of whose commutator segments 
is equal to the number of poles. 

Single-Wound Multiple-Circuit Mul- 



Sin.] 



928 



[Ski. 



tipolar Drum- Armature. — A drum 
armature wound for a multipolar field in 
a single winding and affording a plur- 
ality of paths or circuits between its 
brushes. 

Single-Wound Two-Circuit Drum- 
Armature. — A drum armature, wound 
for a multipolar field, with a single wind- 
ing and affording two conducting paths 
or circuits between the brushes. 

Single-Wound Two-Circuit Multipo- 
lar Ring-Armature. — A ring armature 
wound for a multipolar field, with a single 
winding, which affords but two conduct- 
ing paths or circuits between the brushes. 

Single-Wound Wire.— Wire wound or 
covered with a single layer of insulating 
material. 

Singly Re-Entrant Armature- Wind- 
ing. — (1) A single- winding which re-en- 
ters itself. (2) An armature provided 
with a single-winding which is re-entrant. 

Singular Polarization.— A term applied 
to the polarization of a voltaic cell when 
the depolarizing current is many times 
stronger than the primary current. 

Sinistrorsal Helix. — A sinistrorsal sole- 
noid. 

Sinistrorsal Solenoid. — A solenoid whose 

winding is left-handed. 
Sinuous Current. — A term sometimes 

applied to a current flowing through a 

sinuous conductor. 
Sinusoid. — A name frequently given to a 

curve of sines. 

Sinusoidal. — Of or pertaining to a sinu- 
soid. 

Sinusoidal Alternating Electromotive 
Forces. — (1) Alternating electromotive 
forces whose variations in strength 
are correctly represented by a sinusoidal 
curve. (2) Simple-harmonic E. M. F.'s. 
(3) E. M. F.'s which are simple-harmonic 
functions of time. 

Sinusoidal Alternator.— An alternator 
capable of producing sinusoidal electro- 
motive forces. 

Sinusoidal Currents. — Simple-periodic 
currents whose strengths are correctly 
represented by sinusoids. 

Sinusoidal-Current Circuit. — A circuit 
conveying sinusoidal currents. 

Sinusoidal Curve. — (1) A curve of sines. 
(2) A sinusoid. (3) A curve which to 
rectangular co-ordinates has an ordinate 
at each point proportionate to the sine of 
an angle proportionate to the abscissa. 

Sinusoidal Flux.— A flux which varies 



sinusoidally or according to a simple- 
harmonic law. 
Sinusoidal Generator.— A sinusoidal al- 
ternator or generator capable of deliver- 
ing a simple-harmonic E. M. F. 

Sinusoidal Magnetic Flux.— A sinu- 
soidally varying flux. 

Sinusoidal Magnetomotive Force.— 

A magnetomotive force varying sinu- 
soidally. 
Sinusoidal "Variation. — Such a variation 
of an electromotive force, current, or flux, 
as may be correctly represented by a sin- 
usoid/ 

Sinusoider. — A name sometimes given to 
a sinusoidal alternator. 

Siphon, Electric— A siphon in which 
the stoppage of the flow of the liquid due 
to the gradual accumulation of air, is 
prevented by electrical means. 

Siphon Recorder.— An apparatus for re- 
cording in ink on a strip of paper a mes- 
sage received over a cable by means of a 
jet of ink thrown out from a fine glass 
tube supported on a fine wire. 

Siphon-Recorder Vibrator.— A device 
employed in a siphon recorder to obtain 
the vibrations required for the ejection 
of the ink from the siphon by mechanical 
means instead of by electrical means. 

Siphon Writing. — A record obtained by 
means of a siphon recorder. 

Siren. — An acoustic apparatus employed 
for measuring the frequency of sound 
waves. 

Six-Pole Dynamo-Electric Machine. — 

A sextipolar dynamo. 
Six- Wire System. — A system of distribu- 
tion similar in general to the three-wire 
system, in which five dynamos are con- 
nected to six conductors or leads. 

Six- Wire Triphase System.— A system 
for the production of triphase currents, 
in three separate circuits, each having two 
wires. 

Skew Adjustment of Carbons in Are- 
Lamps. — The adjustment of the carbons 
of an arc lamp by means of which the 
positive carbon is placed a short distance 
in front of, but out of the vertical line 
with the negative carbon. 

Skiagraph. — A word proposed for radio- 
graph. (Not in general use.) 

Skiasmogram. — A word proposed for 
radiograph. (Not in use.) 

Skidding of Car Wheels.— A term ex- 
pressing the sliding of the wheels of a car 
in place of their proper rolling motion. 



Ski.] 



929 



[Slo. 



Skin Currents. — A term applied to rapid- 
ly alternating currents which are limited 
to the surface of a conductor. 

Skin Electromotive Force.— The E. M. 
F. which is active in producing the skin 
effect in a conductor. 

Skin Effect.— The tendency of rapidly 
alternating currents to avoid the central 
portions of solid conductors and flow, for 
the greater part, through the superficial 
portions. 

Skipping of Pointer of Telegraph In- 
strument. — In a dial telegraph, the fail- 
ure of the dial to point to the letter in- 
tended, and caused by its skipping one or 
more of the letters. 

Skodogram. — A term proposed for 
radiograph. (Not in use.) 

Skotograph. — A term proposed for radio- 
graph. (Not in use.) 

Slack.— Excess. 

Slack Cable. — Extra cable, or cable paid 
out in excess of the distance covered, 
in order to permit of the subsequent re- 
covery of the cable without undue strain, 
and also to allow of its accommodating 
itself to irregularities in the contour of 
the sea-bottom. 

Sled. — A sliding contact drawn after a 
moving railroad car through the slotted 
conduit containing the wires or conduc- 
tors from which the driving current is 
taken. 

Sleeve Joint. — A junction of the ends of 
conducting wires obtained by passing 
them through tubes, and subsequently 
twisting and soldering. 

Sleeve of Plug. — A conducting cylinder 
upon a telephone plug, making contact 
with the barrel or socket of a telephone 
jack. 

Slide Bridge. — A bridge whose propor- 
tionate arms are formed of a single thin 
wire, of uniform diameter and of compar- 
atively high resistance, of some material 
whose temperature coefficient is low. 

Slide Contact Piece, — A contact piece in 
which the circuit is completed by means 
of a sliding or wiping joint. 

Slide Form of Electric Bridge.— A slide 
bridge. 

Slide Resistance. — (1) A rheostat whose 
separate resistances or coils are placed in 
or removed from a circuit by means of a 
sliding contact. (2) An apparatus em- 
ployed in telegraphy consisting of a pair 
of slide rheostats actually subdivided into 
100 parts each, but forming jointly a 
rheostat virtually subdivided into 10.000 
parts. 

59 



Slide Switchboard.— A telephone switch- 
board in which the connections are made 
by sliding contacts. 

Slide Wire. — A wire of uniform diameter 
employed in Wheatstone's electric bridge 
for the proportionate arms of the bridge. 

Sliding Bed-Plate.— A bed-plate of a 
belt-driven dynamo, motor, or other sim- 
ilar apparatus, provided with means for 
moving it, so as to tighten the belt. 

Sliding Contact. — A contact connected 
with one part of a circuit that closes or 
completes that circuit by being slid over 
a conductor connected with another part 
of such circuit. 

Sliding Contact-Key. — A key employed 
in the slide form of Wheatstone's bridge 
to make contact with the sliding wire. 

Sliding Joint. — An expansion joint. 

Slings. — Bright copper wires employed for 
hanging an object to be electro-plated to 
the negative rod in the depositing vessel. 

Slinging Wires. — Erecting wires on 
aerial poles. 

Slip. — To release a buoy, rope, anchor etc., 
in cable work. 

Slip of Induction Motor.— The propor- 
tional difference between the speed of the 
rotary magnetic field which drives the 
motor and the speed of the rotor. 

Slip of Rotor. — The proportional differ- 
ence between the speed of a rotary 
magnetic field and the speed of the rotor. 

Slip Thimble. — In cable work, a device for 
readily disengaging a buoy from the side 
of a vessel or from its buoy rope. 

Slippage. — The ratio, subtracted from 
unity, of the speed of a rotor divided by 
the speed of a rotatory magnetic field. 

Slipping of Belt. — The loss of speed of a 
revolving belt on its pulley due to slip- 
ping. 

Slope of Magneto-Motive Force.— A 
term sometimes used for magnetizing 
force. 

Slope of Potential. — A phrase sometimes 
used for drop of potential. 

Slots on Armature Core. — Slots or 
grooves provided in an armature core for 
the reception of the armature coils. 

Slot- Wound Armature.— (1) An arma- 
ture in which the windings are buried in 
slots. (2) An ironclad armature. 

Slotted Armature. — (1) An armature pro- 
vided with slots or grooves for the recep- 
tion of the wires. (2) An iron-clad arma- 
ture. 

Slotted Armature-Core. — An armature 
core provided with longitudinal grooves. 



Slo.] 



930 



[Sof. 



Slotted Conduit. — An underground con- 
duit provided with a slot extending to 
the surface of the road-bed, through 
which a travelling conductor can carry 
off the current from one or more con- 
ductors supported in the conduit. 

Slow-Speed Electric Motor.— (1) An 
electric motor which is capable of efficient 
operation at a comparatively slow speed. 
(2) A motor designed to run at a com- 
paratively slow speed. 

Slow-Speed Generator.— A generator 
designed to be run at a slow speed. 

Sluggish Magnet.— A magnet that ac- 
quires or loses its magnetism sluggishly. 
mashing Point of Incandescent 
Electric Lamp.— Such a period in the 
life of an incandescent lamp which has 
become blackened, when it will be more 
economical to break the lamp, or remove 
it from the circuit and replace it by a 
new one, than to continue its operation. 

Smee Voltaic Cell.— A zinc-silver couple 
employed in connection with an electro- 
lyte of dilute sulphuric acid. 

Smelting of Phosphorus, Electric— 
The electric separation of phosphorus from 
any of its compounds. 

Smooth-Body Generator.— A dynamo or 
generator provided with a smooth-core 
armature. 

Smooth -Core Armature.— (1) An ar- 
mature which presents a continuously 
smooth cylindrical surface before the ar- 
mature coils are wound on it. (2) A sur- 
face-wound armature as distinguished 
from an iron-clad armature. 

Snap Switch. — A switch in which the 
transfer of the contact points from one 
position to another is accomplished by a 
quick motion obtained by the operation 
of a spring. 

Snap Welding of Rails.— A welding- 
joint for a rail bond in which the rails are 
clamped at their short projections, the 
ends heated as rapidly as possible and 
then firmly squeezed together when the 
welding temperature has been reached. 

Snapper. — A device in a sounding-lead 
consisting of a pair of metallic jaws which 
are open when the lead is lowered but 
which automatically close when the sea 
bottom is reached, for the purpose of 
securing samples of the sea bottom. 

Snapper Sounder. — A mechanical device 
for producing, by the flexure of a spring, 
sounds corresponding to Morse characters 
as heard from a Morse sounder. 

Sneak Current.— (1) A relatively weak 
current accidentally introduced into a 



telephonic or telegraphic circuit, which 
would do no immediate harm, but which 
continuing to circulate in a bell or annun- 
ciator coil would generate enough heat 
in a comparatively short time to burn it 
out. (2) A current of sufficient strength 
to be dangerous if maintained, but insuf- 
ficiently strong to melt the usual safety 
fuses. 

Sneak-Current Arrester. — A sneak-cur- 
rent protector or coil. 

Sneak-Current Coil. — A coil of German- 
silver wire inserted in a telephone circuit 
to become sufficiently heated by a sneak- 
current, or current of dangerous strength, 
to melt a drop of fusible metal placed 
within it, and thereby cut the telephone 
apparatus out of circuit. 

Sneak-Current Protector.— A form of 
protector in which a fine fusible wire is 
inserted between the end of a line and the 
instruments. 

Snow-Sweeper, Electric— A form of 
snow-sweeper operated by means of an 
electric motor. 

Soakage. — A term sometimes employed 
for residual charge. 

Soaking-In. — A term sometimes employed 
for the gradual penetration of an electric 
charge through a dielectric. 

Soaking-Out. — A term sometimes em- 
ployed by telegraphers to represent the 
gradual discharge which occurs after 
the first discharge when a charged cable 
conductor is put to earth. 

Socket. — (1) In a telephone switchboard a 
jack or receptacle for a plug. (&) The 
barrel of a jack, as distinguished from the 
contact of the jack placed behind the 
barrel. 

Socket-Base. — A lamp base provided with 
means for ready introduction into a lamp 
socket. 

Socket for Electric Lamp. — A support 
for the reception of an incandescent 
lamp. 

Socket Key. — A key provided in a lamp 
socket for lighting or extinguishing the 
lamp. 

Socket Lamp. — A lamp provided with a 
socket. 

Socket Switch. — A socket key. 

Soft-Drawn Copper Wire. — Copper wire 
that is softened by annealing after being 
drawn. 

Soft Porous Cell. — A soft baked porous 
cell, whose use in a voltaic cell renders its 
internal resistance comparatively low. 

Softness. — That property of a body in 



Sol.] 



931 



[Sou. 



virtue of which it is readily scratched, or 
its molecules displaced. 

Solar Telegraph.— A name sometimes ap- 
plied to a heliograph. 

Solarization. — A term used in photogra- 
phy for the eifect produced by exposure 
to the sun. 

Solder Ear. — An ear or hanger in a trolley 
system to which the trolley is secured by 
solder. 

Soldering, Electric. — A process for ob- 
taining metallic joints, in which electri- 
cally generated heat is employed to melt 
the solder. 

Soldering Flux.— Any chemical suitable 
for use in connection with solder to cleanse 
the surfaces of the articles to be soldered. 

Soldering Furnace. — A portable furnace 
for melting solder and heating soldering 
irons. 

Solenoid. — (1) A cylindrical coil of wire 
whose convolutions are circular. (2) An 
electro-magnetic helix. (3) Theoretically, 
a series of coaxial conducting circles 
placed side by side. 

Solenoid Core.— A core, usually of soft 
iron, placed within a solenoid and mag- 
netized by the magnetic flux of the mag- 
netizing current. 

Solenoid Galvanometer. — A galvano- 
meter whose needle consists of a solenoid 
core. 

Solenoidal. — Of or pertaining to a solenoid. 

Solenoidal Blow-Out.— A magnetic 
blow-out in which the magnet is a solenoid 
devoid of an iron core. 

Solenoidal Distribution.— A space dis- 
tribution of a vector quantity devoid of 
convergence. 

Solenoidal Distribution of Magnetism. 
A term, sometimes applied to such a dis- 
tribution of magnetism in a bar that its 
particles are arranged with their poles in 
the direction of the length of the bar, the 
ends of which are of opposite magnetic 
polarities, and the extent of whose surface 
is small as compared with the length of 
the bar. 

Solenoidal Magnet.— A magnet possess- 
ing a solenoidal distribution of magnetism. 

Solid Angle. — (1) The opening between 
three or more planes at their point of 
common intersection. (2) The area of a 
portion of spherical surface of unit radius 
as traced by a central radius vector which 
traces the outline of the solid angle. 

Solid Arc-Light Carbons.— (1) Carbon 
electrodes for arc lights unprovided with 
a core of softer carbon. (2) A carbon 



which is of uniform composition through- 
out as distinguished from a cored carbon. 

Solid-Back Telephone Transmitter.— 
A term applied to a form of microphone 
transmitter, largely employed in long- 
distance telephony. 

Solid Carbons. — Solid arc-light carbons. 

Solid Conduit.— A conduit in which the 
insulating material is cast or placed around 
the wires or conductors so that they can- 
not be removed from the conduit with- 
out breaking. 

Solid Depolarizer. — Any solid substance 
employed in connection with the negative 
plate of a voltaic cell for the purpose of 
effecting its depolarization. 

-Solid Thermostat. — A thermostat whose 
operation depends on the expansion of a 
solid, or on the unequal expansion of two 
different solids. 

Solid Wires. — Any conductor formed of 
a single wire, as distinguished from a 
stranded conductor, or one formed of a 
number of parallel wires. 

Soluble Electrodes. — Electrodes em- 
ployed in metallic electrolysis, made of 
copper, iron or other metals which are 
converted into metallic salts during elec- 
trolysis. 

Solution. — A liquid in which a solid, gas 
or another liquid is dissolved. 

Sonometer. — A single wire stretched at 
its ends, provided with a movable bridge 
for the purpose of determining the rela- 
tion existing between the frequencies of 
the successive tones of any gamut. 

Sonometer Interrupter.— A term some- 
times employed in place of electro-dyna- 
mic interrupter. 

Sonorescence. — A word proposed for the 
sounds produced when a piece of vulcan- 
ite, or other solid substance, is exposed to 
a rapid succession of flashes of light. 

Sonorous. — Sounding or producing sound. 

Soot Cell. — In radiophony. a name some- 
times given to a carbon cell. 

Sound. — (1) The sensation produced on the 
brain through the ear by the vibrations 
of a sonorous body. (2) The sound waves 
that are capable of producing a sensation 
of sound on the brain through the ear. 

Sound Error. — In telegraphy, an error 
made by mistaking the sound of a signal, 
syllable, word or phrase, as distinguished 
from an error made by mistaking the 
sight of a written character or word. 

Sound Wc.vos. — AYaves produced in the 
air or other elastic medium by the vibra- 
tions of a sonorous body. 



Son.] 



932 



[Spa. 



Sounder Resonator.— (1) A name some- 
times given to a sounder surrounded by a 
resonant case, for the purpose of increas- 
ing the intensity of its sound by reso- 
nance. (2) A box-sounding relay. 

Sounding Board. — An elastic board em- 
ployed in a stringed musical instrument 
for the purpose of increasing the intensity 
of the sounds by resonance. 

Sounding Relay.— A box-sounding relay. 

Sounding Tube. — A tube employed in a 
deep-sea sounding-lead for the purpose of 
securing a sample of the sea bottom. 

Source, Electric. — Any arrangement ca- 
pable of maintaining a difference of po- 
tential or electromotive force. 

Southern Light. — The aurora australis. 

South Magnetic Pole.— (1) That pole of 
a magnetic needle which points approxi- 
mately to the earth's geographical south. 
(2) The south-seeking pole of a magnetic 
needle. 

South-Seeking Magnetic Pole. — The 
south magnetic pole. 

Spacer. — In a double-current Morse trans- 
lator, an electro-magnet in the local cir- 
cuit, sending zinc, negative, or spacing 
currents on the circuit to which the cur- 
rent is being delivered. 

Spacing Battery. — A battery in double- 
current telegraphy employed to send spac- 
ing currents. 

Spacing Current. — (1) The current em- 
ployed in automatic telegraphy for the 
purpose of leaving a space on the record- 
ing paper, as distinguished from the 
marking current, or the current that is 
intended to record a dot or dash on the 
paper. (2) In double-current telegraphy, 
the currents in one direction which effect 
and correspond to spaces as distinguished 
from those in the other direction which 
effect and correspond to marks or signals. 

Spacing of Armature Conductors.— The 
pitch of an armature winding. 

Span Cable- Way. — An overhead cable 
suspended from poles, and intended for 
supporting an electric locomotor in a sys- 
tem of electric haulage or telpherage. 

Span Guard-Wire. — A wire strung across 
the street over a trolley wire for the pur- 
pose of preventing a wire from falling on 
the trolley wire, as distinguished from 
running guard wires which overhang and 
follow a trolley wire along the street. 

Span Wires. — Wires tightly stretched 
across a street from pole to pole, for the 
purpose of supporting trolley wires. 

Span- Wire Hangers. — The hangers which 



suspend the trolley wires from the span 
wires. 

Span-Wire Trolley Line Construction. 

A method for the suspension of an aerial 
trolley line, in which the trolley and feed 
wires are suspended from span wires sup- 
ported on poles placed opposite to one 
another on each side of the street or road. 

Spanish Spoon. — A name given to a form 
of shovel employed for lifting soil out of 
a hole in the ground excavated for a tele- 
graph pole. 

Spar Torpedo.— A torpedo attached to 
the end of a spar and designed to be ex- 
ploded by percussion against the side of 
an enemy's vessel when thrust against it. 

"Spare" Machine.— An extra dynamo, 
motor or other machine reserved in an in- 
stallation for use in case of accidental 
break down. 

Spark Arrester. — A device for preventing 
an arc lamp from scattering sparks or 
particles of incandescent carbon. 

Spark Chronograph.— A form of electric 
chronograph in which the record is made 
of the time of a certain event by means 
of a spark from a Ruhmkorff or spark 
coil. 

Spark Coil. — A coil of insulated wire con- 
nected with the main circuit in a system 
of electric gas lighting, whose extra spark 
produced on breaking the circuit is em- 
ployed for electrically igniting gas jets. 

Spark Discharge.— (1) An electric dis- 
charge effected by a spark. (2) A dis- 
ruptive discharge. 

Spark, Electric. — A term sometimes ap- 
plied to a disruptive discharge. (2) The 
phenomena produced by a disruptive dis- 
charge in the air-space or gap through 
which the discharge passes. 

Spark G-ap. — (1) The air-space or gap 
through which a disruptive discharge 
passes. (2) A gap forming part of a cir- 
cuit between two opposing conductors 
and filled with air or other dielectric, 
across which a spark passes when a cer- 
tain difference of potential has been 
reached. 

Spark Micrometer.— A spark gap capable 
of delicate adjustment and measurement. 

Spark Tube. — A high- vacuum tube across 
which the spark from an induction coil 
will not pass, if the vacuum is sufficiently 
high. 

Sparking. — Discharging by means of dis- 
ruptive sparks. 

Sparking Discharge.— A disruptive dis- 
charge. 



Spa.] 



933 



[Spe< 



Sparking Distance. — The distance 
through which electric sparks will pass 
across an intervening air-gap. 

Sparking of Dynamo-Electric Ma- 
chine. — An irregular and injurious oper- 
ation of a dynamo attended with sparks 
at its collecting brushes. 

Sparking Terminals. — (1) The terminals 
of a spark-gap. (2) The points or ends of 
a spark-gap. 

Sparkless Commutation. — Commuta- 
tion of a dynamo accomplished without 
sparking at the brushes. 

Spasmodic Governor. — A name given to 
a form of governor for electric motors, in 
which the current is automatically cut 
off in proportion as the work is cut off. 

Speaking Battery. — In telegraphy or 
telephony, the battery employed for 
speaking or signalling. 

Speaking Key. — (1) In telegraphy, a key 
employed in speaking. (2) A signalling 
key as distinguished from a testing key. 

Speaking Mirror. — A simple form of 
mirror galvanometer employed in cable 
telegraphy for the reception of the cur- 
rent impulses or signals. 

Speaking Mirror Plug. — A closed tube 
or plug for insertion into a speaking mir- 
ror instrument, and containing a sus- 
pended mirror and magnet. 

Speaking Switch. — In telegraphy, a 
switch employed in speaking or signalling. 

•Speaking Telegraph.— A term sometimes 
employed for the telephone. 

Speaking Telegraphy.— A term some- 
times employed for telephony. 

Speaking-Tube Annunciator.— An oral 
annunciator. 

Speaking-Tube Mouth-Piece Alarm, 
Electric. — A mouth-piece for a speaking- 
tube, so arranged that the movement of 
a pivoted plate covering the mouth-piece 
automatically rings an electric bell at the 
other end of the tube. 

Speaking-Tube Telephone System.— A 
name sometimes employed for a system 
of telephone communication by means of 
which a number of offices can be con- 
nected without the use of a central switch- 
board. 

Speaking Wire. — In a system of tele- 
phony, a wire connecting two exchanges 
for the purpose of communicating instruc- 
tions between operators, as distinguished 
from a wire through which a subscriber 
may be connected. 

Specific Capacity. — Specific inductive 
capacity. 



Specific Conductance.— A term some- 
times used for specific conductivity. 
Specific Conduction Resistance. — 

(1) Resistivity. (2) A term sometimes 
used for specific resistance. 

Specific Conductivity.— (1) The partic- 
ular conductivity of a substance for elec- 
tricity. (2) The specific or particular re- 
sistance of a given length and area of 
cross-section of a substance, as compared 
with the same length and area of cross- 
section of some standard substance. 
(3) Conductivity with reference to Mat- 
thiessen's standard conductivity. 

Specific Dielectric Capacity. — A term 
sometimes employed in place of specific 
inductive capacity. 

Specific Energy. — (1) Volumetric energy. 

(2) Energy per unit of volume. 
Specific Gravity. — The weight of a given 

volume of a substance, as compared with 
an equal volume of some standard sub- 
stance, such as water. 

Specific Heat. — The capacity of a sub- 
stance for heat, as compared with an 
equal quantity of some other substance 
taken as unity. 

Specific Heat of Electricity.— A term 
proposed to indicate the analogies exist- 
ing between the absorption and emission 
of heat in purely thermal phenomena, 
and the absorption and emission of heat 
in thermo-electric phenomena. 

Specific Hysteretic Dissipation. — 

(1) The loss of energy by hysteresis in a 
particular substance, per unit of volume. 

(2) The hysteretic loss of energy in a sub- 
stance under given conditions compared 
with the similar loss in a standard sub- 
stance. 

Specific Inductive Capacity.— (1) The 
ability of a dielectric to permit induction 
to take place through its mass as compar- 
ed with the ability possessed by a vacuous 
space of the same dimensions, under pre- 
cisely the same conditions. (2) The rela- 
tive power of bodies for transmitting elec- 
trostatic stresses and strains, analogous 
to permeability in metals. (3) The ratio 
of the capacity of a condenser whose coat- 
ings are separated by a dielectric of a 
given substance, to the capacity of a 
similar condenser whose plates are sep- 
arated by a vacuum . (4) The ratio of the 
permittivity of a substance to the permit- 
tivity of vacuum. 

Specific Magnetic Capacity. — (1) A 
term sometimes employed in the sense of 
magnetic permeability. (2) A word em- 
ployed for conductibility for magnetic 



Spe.] 



934 



[Spe. 



flux, in the same sense that specific capac- 
ity is conductibility for electrostatic flux. 

Specific Magnetic Conductivity.— The 
specific or particular permeability of a 
substance to magnetic flux. 

Specific Magnetic Induetivity .— A term 
sometimes used for specific magnetic con- 
ductivity. 

Specific Magnetic Reluctance. — A 
term sometimes used for specific magnetic 
resistance. 

Specific Magnetic Resistance.— A term 
sometimes used for reluctivity. 

Specific Magnetism. — A term proposed 
for the quotient of the magnetic moment 
of a magnet by its mass. 

Specific Molecular Conductivity. — 
Molecular conductivity as referred to that 
of some standard substance. 

Specific Reluctance. — A term sometimes 
used for reluctivity. 

Specific Resistance.— (1) The particular 
resistance a substance offers to the pas- 
sage of electricity through it, compared 
with the resistance of some standard sub- 
stance. (2) In absolute measurements, the 
resistance in absolute units between op- 
posed faces of a centimetre cube of a 
given substance. (3) In the practical 
system, the above resistance in ohms. (4) 
Resistivity, expressed in electro-magnetic 
absolute units as square-centimetres per 
second. 

Specific Resistance of Liquid. — 
(1) The resistance of a given length and 
area of cross-section of any liquid as com- 
pared with the resistance of an equal 
length and cross-section of pure copper 
or other standard conductor. (2) Resis- 
tivity of a liquid. 

Spectrograph. — A word proposed for 
radiograph. 

Spectrophone. — An instrument employed 
for the exploration of the ultra- red por- 
tion of the spectrum. 

Speetro-Photometer. — (1) A form of 
photometer suitable for measuring the 
relative intensities of lights of different 
qualities. (2) A photometer which com- 
pares luminous intensities in successive 
portions of spectra, frequency by fre- 
quency. (3) A spectroscope so arranged 
as to readily permit of the comparison as to 
brightness, "wave-length by wave-length, 
of rays from two different luminous 
sources. 

Spectro-Photometric. — Of or pertaining 
to the spectro-photometer. 

Spectro-Photometry. — Photometry by 
means of the spectro-photometer. 



Spectroscope. — An optical instrument for 
determining the composition of a body 
by the character of the light it emits, as 
determined by its component frequencies. 

Spectroscopic. — Of or pertaining to the 
spectrum. 

Spectrum. — A band of multicolored light 
or radiant energy of different frequencies, 
obtained by dispersion in a prism or by a 
diffraction grating. 

Speed Constant.— In submarine telegra- 
phy, a constant quantity which divided 
by the product of the capacity and resist- 
ance of a cable gives the working speed 
of the cable in letters per minute. 

Speed Counter.— Any apparatus for deter- 
mining the number of revolutions of a 
shaft. 

Speed and Direction Indicator. — A 

telegraph on board ship for indicating the 
speed of revolution of the propeller shaft 
and the direction of its movement. 

Speed Indicator. — A form of speed 
counter. 

Speed of Rotation. — (1) The number of 
revolutions per second, per minute, hour 
or unit of time generally. (2) The dis- 
tance passed over in a given time by the 
circumference of a rotating wheel or 
pulley. (3) The angular velocity of rota- 
tion in degrees or radians per unit of 
time. 

Speed Recorder.— (1) An apparatus for 
recording the instantaneous values of the 
speed of any machine. (2) An instru- 
ment for both indicating and recording 
the speed of a trolley car from moment 
to moment. 

Speeding. — (1) Varying the number of 
revolutions per second. (2) Increasing a 
speed of rotation. 

Speeding of Dynamo.— Varying the 
speed of a dynamo, for the purpose of ob- 
taining the proper speed required to oper- 
ate an electro-receptive device placed in 
its circuit. 

Spelter. — A name sometimes given to com- 
mercial zinc. 

Spent Acid. — A battery or other acid that 
has, through use, become too weak for 
efficient action. 

Spent Liquor. — Any liquor such as that 
used in an acid or other bath, that has 
through use become too weak for efficient 
action . 

Spewing of Cable Core.— The mechani- 
cal derangement of a cable, whereby the 
sheathing opens and the core appears on 
the surface. 



Spli.] 



935 



[Sl>li. 



Spherical Aberration.— A defect where- 
by a lens or mirror with spherical faces 
fails to produce in its images the correct 
outlines of objects, owing to the fact that 
the curvature of one or both of its faces 
should slightly depart from the true 
spherical form in order to produce a true 
image. 

Spherical Ar mature. — An armature for 
a dynamo, the coils of which are wound 
on a spherical iron core. 

Spherical Bougie Decimale.— (1) A unit 
of luminous flux equal to that which 
would be produced by a point source 
having an intensity of one bougie deci- 
male in all directions. (2) A luminous 
flux equal to 12.566 lumens. 

Spherical Candle-Power.— (1) The total 
flux of light emitted by a luminous source 
divided by 12.566. (2) The candle-power of 
a point-source, which emits with uniform 
intensity in all directions, as much light 
as does an actual lamp. (3) The average 
candle-power of a luminous source taken 
in all directions, or considered over the 
entire surface of an enveloping sphere. 

Spherical Candle-Power Measurer.— 
An instrument for measuring, or ena- 
bling to be measured, the mean spherical 
candle-power of a source of light from a 
single observation. 

Spherical Candle-Power Photometer. 

(1) A photometer designed to measure 
the mean spherical candle-power of a 
lamp. (2) A photometer designed to 
measure the mean spherical candle-power 
of a luminous source from a single ob- 
servation. 

Spherical Harmonics. — Homogeneous 
functions of rectilinear space-co-ordinates 
which satisfy Laplace's equation. 

Spherical Strain Insulator. — An insu- 
lator for a guy-wire or trolley pull-off, 
spherical in form. 

Spherometer. — An apparatus for readily 
measuring the curvature of a sphere. 

Sphygmogram. — A record made by a 
sphygmograph. 

Sphygmograph. — An instrument for re- 
cording the movements of the pulse, usu- 
ally of the radial artery at the wrist. 

Sphygmograph, Electric. — An instru- 
ment for electrically recording the pecul- 
iarities of the pulse. 

Sphygmophone. — An apparatus employ- 
ing a microphone for the medical exam- 
ination of the pulse. 

Sphygmoscope. — An apparatus for de- 
tecting, but not recording, the peculiari- 
ties of the pulse. 



Spider. — A radial bracket or support for 
supporting an armature or machine on a 
revolving shaft. 

Spider Arm. — One of the projections of a 
spider support. 

Spin. — (1) The curl of a vector point- 
function. (2) Rotation. (3) Vorticity. 

Spiral. — (1) A helix. (2) A word some- 
times employed in electricity and mag- 
netism for an open conducting coil. 

Spiral Accumulator. — An accumulator 
whose plates consist of two parallel plates 
of lead insulated from each other and 
rolled into a close spiral. 

Spiral Loop System of Parallel Distri- 
bution. — A modified form of loop system 
for parallel distribution. 

Spiral Loop System of Distribution. — 
A name given to a variety of parallel 
distribution adopted for obtaining a com- 
paratively uniform distribution of poten- 
tial, in which the parallel conductors are 
extended in the arcs of spirals from the 
generating station throughout the district 
to be served, both spirals extending from 
one pole of the generator nearly to the 
other pole. 

Spiral Winding. — A solenoidal winding. 

Spiralled Fours of Cable.— A defect in 
the winding of a telephone cable, in which 
any four wires are so wound about the 
core that one pair is not on the average 
midway between the other pair, so that 
cross-talk is sure to result. 

Splice Bar. — A fish plate employed for 
connecting together the ends of a rail. 

Splice Box. — A box provided for holding 
splice joints and loops so arranged as to 
be readily accessible for examination , re- 
arrangement, cross-connection, etc. 

Splicing. — Connecting the sheathings of 
the two ends of a cable at a joint. 

Splicing Ear. — (1) A trolley ear for uniting 
the ends of a trolley wire. (2) A splicing 
suspension ear. 

Splicing Mallet. — A mallet used in a sub- 
marine cable splice for laying on a serv- 
ing of yarn under tension. 

Splicing Sleeve. — A tube of conducting 
material employed for covering a splice 
in a conducting wire. 

Splicing Suspension Ear. — A metal 
piece suitably supported on an insulator 
and provided in a system of overhead 
trolley wires for connecting two separate 
ends of the trolley line. 

Splicing Tool. — A tool employed in 
making a cable splice, for forcing the 
sheave wires around the cable in their 



Spli.] 



936 



[Spr. 



proper spiral position corresponding to 
that which they have on other parts of 
the cable. 

Splicing Tube. — A name sometimes given 
to a connector employed in making a 
joint in a trolley wire. 

Split Battery.— A voltaic battery connect- 
ed in series and having one of its middle- 
plates connected to the ground. 

Split Condenser.— (1) A condenser so ar- 
ranged that its different sections can be 
readily inter-connected in the same cir- 
cuit or employed in different circuits as 
may be required. (2) A subdivided con- 
denser. 

Split Current.— (1) A divided current. 
(2) A current tapped from a main tele- 
graph wire. 

Split Dynamometer.— A dynamometer 
employed in connection with alternating 
currents provided with two coils, so ar- 
ranged that separate currents of the same 
frequency can be passed independently 
through each. 

Split Lead-Tee.— A T-shaped lead tube 
that is split for readily covering a joint at 
a branch in a cable. 

Split Phase.— A difference produced be- 
tween the phases of two or more alter- 
nating currents into which a uniphase 
alternating current has divided. 

Split-Phase Motor.— (1) A multiphase 
motor operated from a uniphase alternat- 
ing-current circuit by the introduction of 
a phase-splitting device. (2) A multiphase 
motor in which the multiphase currents 
are locally produced from a single-phase 
circuit. 

Split-Pin Plug. — A plug having two 
halves or two sleeves insulated from each 
other, employed for readily introducing a 
loop into a circuit. 

Split-Ring Magnet.— A ring-core magnet 
provided with an air-gap. 

Split-Secondary of Induction Coil.— 

The secondary of an induction coil which 
is divided into two equal portions. 

Spluttering of Arc. — A spluttering sound 
attending the formation of a voltaic arc. 

Spokes of Armature Core.— Radial pro- 
jections on a spider in an armature core, 
on which coils are sometimes wound. 

Sponge Electrode. — A therapeutic elec- 
trode provided with a sponge. 

Spontaneous Electricity.— A term for- 
merly employed for the electricity pro- 
duced by the melting of sulphur. 

Spot. — The reflected image or luminous 



patch of light on a mirror galvanometer 
scale. 
Spotty Filament.— The filament of an 
incandescent lamp possessing such local 
variations in resistance that when ren- 
dered luminous by the passage of the cur- 
rent, it possesses points of unequal brill- 
iancy. 

Spreader Bracket.— A name sometimes 
given to a loop bracket. 

Spreader for Arc Wires.— A form of 
loop bracket employed on arc circuits. 

Spreading of Magnetic Field.— A term 
sometimes employed for divergence of a 
magnetic field. 

Sprengel Mercury Pump.— A mercurial 
air pump in which the vacuum is obtained 
by means of the fall of a stream of 
mercury through a tube in such a manner 
as to entangle portions or bubbles of 
residual air. 

Spring Ammeter. — A form of ammeter 
in which a magnetic core or needle is 
moved against the action of a spring by 
the field of the current it is measuring. 

Spring Clips of Switch.— Spring jaws of 
a switch which grasp the blade or blades 
in the closed position. 

Spring Contact.— (1) A contact which 
either opens or closes under the action of 
a spring. (2) A spring-supported contact, 
connected with one part of a circuit, that 
completes the circuit on being moved so 
as to touch another contact connected 
with the other part of the circuit. (3) A 
circuit-closing or circuit- opening device 
normally maintained in one position and 
condition by the action of a spring. 

Spring Dynamometer.— A dynamometer 
whose operation is dependent on the 
action of a spring. 

Spring Jack. — A form of spring contact 
provided with a hole for the insertion of 
a plug. 

Spring- Jack Cut-Out. — A cut-out operat- 
ed by a spring jack. 

Spring-Jack Telephone Switchboard. 
A form of telephone switchboard pro- 
vided with calling drops, clearing out 
drops, and spring jacks, so arranged as to 
readily enable a number of subscribers to 
be placed in inter-communication. 

Spring Manometer.— A manometer 
whose operation is dependent on the de- 
formation of an elastic solid. 

Spring Relay-Contact. — A form of relay 
contact which is interrupted by the action 
of a spring as soon as the circuit is 
broken. 



SprJ 



937 



[Sta. 



Spring-Snag Lever-Switch.— A form of 
switch operated by a spring snap lever. 

Spring - Suspended Street -Rail way- 
Motor. — A street-railway car motor sus- 
pended from the car truck by means of 
springs. 

Spring Voltmeter.— A form of voltmeter 
in which the potential difference is 
measured by the movement of a magnetic 
needle, coil, or core, against the pull of a 
spring. 

Spurious Hall Effect. — An apparent 
transverse electromotive force in conduc- 
tors carrying electric currents in magnet- 
ic fields, by changes, produced by magnet- 
ism, in the conductivity of the metals 
and the consequent production of local 
disturbances in the electrical flow, thus 
resulting in an apparent transverse elec- 
tromotive force. 

Spurious Resistance.— A false or ap- 
parent resistance arising, from the devel- 
opment of a counter-electromotive force. 

Square Conductor. — A form of power 
conductor with rectilinear cross-section. 

Square Mil. — (1) A unit of area employed 
in measuring the areas of cross-section of 
wires, equal to .000001 square inch. 
(2) A unit of area equal to 1.2732 circular 
mils. 

" Squeeze." — In electro-typing the im- 
pression obtained by subjecting a type, or 
woodcut, to a plate or mass or soft wax. 

Squeezer. — A device for testing the duc- 
tility of a wire, consisting in a receptacle, 
somewhat resembling a lemon squeezer, 
in which the wire is placed and clamped 
and the device opened and closed until 
the wire breaks. 

Squirted Filament.— A filament for an 
incandescent lamp made by the carboni- 
zation of a carbonaceous paste, that is 
shaped by being squirted by pressure 
through a suitably shaped die hole. 

Stabile Galvanization. — A terra em- 
ployed in electro-therapeutics in which 
the current is caused to pass continuously 
and steadily through the portions of the 
body undergoing galvanization. 

Stable Equilibrium. — (1) The equilib- 
rium of a body supported on a base, such 
that in order to overturn it, its centre of 
gravity must be raised. (2) The equilib- 
rium of a body so supported that any 
small displacement raises its centre of 
gravity. 

Stable Period of Circuit. — (1) That 
condition of a circuit in which the cur- 
rent passing through it has reached its 



full strength, and is no longer undergoing 
variations. (2) The permanent state. 

Stage Regulator. — A controller of incan- 
descent lamps in a theatre, placed near 
the stage, whereby they may be lighted, 
extinguished, or dimmed. 

Staggered Armature. — An armature in 
which the conductors do not lie on its 
surface in a direction parallel to the axis 
of rotation, but cross its surface diag- 
onally. 4 

Staggering of Dynamo Brushes.— A 
term sometimes applied to the position of 
the brushes on a commutator cylinder, in 
which one brush is placed slightly in ad- 
vance of the other, so as to wear the 
commutator surface smoothly, and pre- 
vent the formation of grooves. 

Stalk of Insulator. — The support or inner 
metal cylinder of an aerial line insulator. 

Standard. — A metallic pole supported on 
the roof of a house for carrying overhead 
wires. 

Standard Candle.— (1) A candle of defi- 
nite composition, which, when burned at 
the rate of two grains per minute, will 
produce a light of a definite and fixed 
brightness. _ (2) A legal standard of light 
in Great Britain. 

Standard Cell. — A standard voltaic cell. 

Standard Clock.— A clock employed for 
the comparison of other clocks. 

Standard Coil. — A standard resistance 
coil. 

Standard Compass.— A compass on board 
ship which is used as a standard and by 
which other compasses may be checked 
or compared. 

Standard Cross-Arms.— Wooden cross- 
arms of standard dimensions for support- 
ing aerial wires on poles. 

Standard Earth - Quadrant. — (1) A 
length approximately equal to 10,000 
kilometres. (2) One quarter of the merid- 
ian circle of the earth taken through Paris. 
(3) A standard unit of inductance. 

Standard Feeder.— A term sometimes 
applied to a principal feeder, operated at 
standard pressure. 

Standard Luminous Intensity. — 
(1) Any unit of luminous intensity em- 
ployed as a standard. (2) A luminous 
intensity of one violle, bougie-decimale, 
Hefner- Alteneck, carcel, British standard 
candle, etc. 

Standard Megohm.— A resistance equal 
to one million ohms, employed as a 
standard. 

Standard Ohm. — A length of wire having 



Sta.] 



938 



[Sta. 



a resistance of the value of one ohm, em- 
ployed in standardizing resistance coils. 

Standard Quadrant.— (1) The standard 
earth quadrant. (2) A standard induct- 
ance equal to one quadrant. 

Standard Besistance.— A known resist-- 
ance used for comparison with, or deter- 
mination of, an unknown resistance. 

Standard Resistance Coil.— A coil whose 
resistance is that of a standard ohm or 
some multiple or sub-mul tiple thereof. 

Standard Telephone Switchboard.— 
A name applied to a form of multiple 
switchboard commonly employed in the 
United States. 

Standard Time.— Mean solar time used 
in telegraphy, and referred either to the 
meridian of Greenwich, or to some other 
meridian west of Greenwich, an exact 
number of hours. 

Standard Voltaic Cell.— A voltaic cell 
whose electromotive force is practically 
constant, and which can, therefore, be 
used as a standard in the measurement of 
an unknown electromotive force. 

Standard "Wire Gauge.— A wire gauge 
adopted by the National Telephone Ex- 
change Association and the National 
Electric Light Association of America. 

Standards.— (1) Telegraphic or telephonic 
supports placed on the roof of a building 
for the purpose of supporting the wires or 
conductors. (2) A general term for a 
resistance coil, voltaic cell or other stand- 
ard employed for purposes of comparison. 
(3) A term applied to the support of the 
bearings of a dynamo or motor. 

Standardized Resistance Coil.— A coil 
whose resistance has been carefully ob- 
tained by comparison with a standard. 

Standardizing a Voltaic Cell.— Deter- 
mining the exact value of the electromo- 
tive force of a voltaic cell, in order to 
permit it to be used as a standard in ob- 
taining the electromotive force of any 
electric source. 

Standing Torque. — Starting torque. 

Star Current in Polyphase System. — 
(1) A current between any line or terminal 
of a polyphase system and the neutral 
point. (2) The current in any branch of 
a star polyphase system. 

Star Grouping of Polyphase Circuits. 
A method of grouping a triphase circuit 
consisting of making a common junction 
at one point and branching them star- 
wise. 

Star Potential in Polyphase System. — 
The effective difference of potential or 



voltmeter pressure between any line or 
terminal of a polyphase system and the 
neutral point. 

Star Triphase- Winding.— A connection 
of three triphase windings in which all 
three are connected together at a common 
point or junction point, and the three 
free ends connected to the terminals. 

Star Triphaser. — A triphaser possessing 
a star triphase winding. 

Starting Box. — A name sometimes applied 
to a starting resistance. 

Starting Box for Electric Motor.— A 
resistance provided for starting an elec- 
tric motor. 

Starting Box of Shunt-Wound Motor. 
A box provided with a rheostat of variable 
resistance, introduced into the armature 
circuit of a shunt-wound motor for the 
purpose of preventing the rush of current 
made on first connecting the motor with 
the driving-circuit. 

Starting Coil of Motor.— A coil employed 
as a starting resistance for an electric 
motor. 

Starting Current of Motor.— The cur- 
rent traversing the coils of a motor at 
its moment of starting. 

Starting Motor for Synchronous 
Motor. — A small electric motor some- 
times employed for bringing the arma- 
ture of a synchronous single-phase motor 
up to its proper speed before connecting 
it with the driving-current circuit. 

Starting Position of Street- Car Con- 
troller. — (1) The position of a street-car 
controller switch at which the current is 
cut off from the motors. (2) The position 
of a street-car controller switch, at which 
the current is first admitted to the motors 
when starting. 

Starting Besistance. — A resistance em- 
ployed in the starting box for an electric 
motor. 

Starting Bhecstat.— Coils of wire mount- 
ed in a suitable manner, and so connected 
as to be successively placed in the circuit 
of a motor while it is being started. 

Starting Torque of Motor.— (1) The 
torque required in starting a motor. (2) 
The torque developed by a motor in start- 
ing. 

Static Balance. — A duplex or quadruplex 
balance adjusted for the capacity of a line 
by the use of a condenser. 

Static Balance of Duplex System. — 
(1) The capacity balance of a duplex sys- 
tem as distinguished from the resistance 
balance. (2) A balance for charging and 



Sta.] 



939 



[Sta 



discharging as distinguished from a bal- 
ance for steady currents. 

Static Breeze. — An electric breeze ob- 
tained by a convective discharge or an 
electrostatic discharge. 

Static Compensating Condenser.— A 
condenser employed in the artificial line 
of duplex or quadruplex telegraphy. 

Static Compensator. — A condenser em- 
ployed for compensating the electro-static 
capacity of a line in the duplex system. 

Static Discharge. — A name sometimes 
given to a disruptive discharge. 

Static Electricity. — A term applied to 
electricity produced by friction. 

Static Electro-Motor.— An electro-motor 
operated by the repulsion of electric 
charges. 

Static Energy.— (1) A term used to ex- 
press the energy possessed by a body at 
rest, resulting from its position as regards 
other bodies, in contradistinction to ki- 
netic energy, or the energy possessed by a 
body whose atoms, molecules and masses 
are "in actual motion. (2) Potential en- 
ergy. 

Static Hysteresis.— (1) A term sometimes 
applied to that quality in iron or other 
paramagnetic substance, by virtue of 
which energy is dissipated during every 
reversal in its magnetization, in contra- 
distinction to viscous hysteresis. (2) Elec- 
trostatic dielectric hysteresis. 

Static Induction. — A term sometimes 
employed for electrostatic induction. 

Static Insulation. — A term employed in 
electro-therapeutics for a method of treat- 
ment by convection streams or discharges, 
in which the patient is seated on an insu- 
lated stool connected to one pole or elec- 
trode of an influence machine, while the 
other pole or electrode is connected to the 
ground. 

Static Magnetic Induction. —The in- 
duction which takes place in the field of 
a magnet whose flux is stationary as re- 
gards the body in which the induction is 
occurring. 

Static Shock.— (1) A term employed in 
electro-therapeutics for a mode of apply- 
ing Franklinic currents or discharges by 
placing the patient on an insulating stool 
and applying one pole of a static machine 
provided with small condensers or Leyden 
jars, while the other pole is connected to 
the body of the patient. (2) An electro- 
static shock. 

Static System of Induction Teleg- 
raphy. — A system of induction teleg- 
raphy depending on static induction be- 



tween the sending and the receiving in- 
strument. 

Static Time Constant.— The electrostatic 
time constant of a circuit. 

Static Transformer.— A term sometimes 
employed for an ordinary transformer, 
to distinguish it from a rotary trans- 
former. 

Static Voltmeter.— (1) A voltmeter oper- 
ating by electrostatic action, as opposed 
to a voltmeter operating electro-magneti- 
cally. (2) A voltmeter in which the mov- 
ing system is displaced by electrostatic 
forces. (3) A voltmeter of the electro- 
scope or electrometer type. 

Statics. — (1) That branch of science which 
treats of the relations that must exist be- 
tween the points of application of forces 
and their direction and intensity, in order 
that equilibrium may result. (2) The 
science of forces at rest. 

Station Circuit - Breaker.— A circuit- 
breaker in a central station. 

Station Indicator.— (1) A name some- 
times given to a station voltmeter. (2) 
Any indicator situated at a central station. 

Station Load.— The total load existing on 
a central station at any time. 

Station Load-Curve. — A curve repre- 
senting the station load at different 
times. 

Station Panel.— (1) A panel in a central- 
station switchboard. (2) A load panel in 
a central-station switchboard showing the 
total load of the station. (3) A panel in 
a central-station switchboard connecting 
a feeder running to some other station or 
sub-station. 

Station Recording-Wattmeter. — A 
wattmeter suitable for use in a central 
station for recording the energy delivered 
bv the station . 

Station Switch. — (1) A switch in a sta- 
tion. (2) A switch for connecting an 
auxiliary station to a system. (3) A 
switch supplying an auxiliary station. 
(4) A switch for connecting the lighting 
or other local wires in a central station to 
the system of distribution. 

Station Transformer. — (1) A transform- 
er placed in a central station. (2) A 
transformer which supplies a load in a 
station. (3) A transformer intended to 
supply current to lamps and potential 
indicators on the switchboard in the 
station. 

Stationary Transformers.— A word 
sometimes applied to ordinary alternat- 
ing-current transformers, in contradis- 
tinction to rotary transformers. 



Sta.] 



940 



[Ste. 



Stationary Electric Motor. — An electric 
motor that is fixed to the floor or ground, 
in contradistinction to a travelling or 
locomotor. 

Stationary Fare-Register for Street 
Car. — A register placed permanently in 
a car, for the purpose of recording the 
fare received by a conductor. 

Stationary Floor-Key.— A name some- 
times applied to a floor push. 

Stationary Hook of Telephone. — A 
fixed hook provided for holding a tele- 
phone. 

Stationary Motor.— A motor that is fixed 
in place, in contradistinction to a loco- 
motor. 

Stationary Secondary of Induction 
Motor. — An induction motor whose sec- 
ondary coils form the stator. 

Stationary Tachometer.— Any tacho- 
meter employed for indicating the num- 
ber of revolutions per minute of a shaft 
in a stationary rotating machine. 

Stationary Torpedo.— A term sometimes 
employed for a submarine mine. 

Stator. — That part of a dynamo or motor, 
whether the armature or the field, which 
remains at rest or stands still during the 
operation of the machine, as distinguished 
from the rotor or part which rotates. 

Stator Armature. — (1) An armature of a 
dynamo or motor that remains at rest 
during the operation of the machine. 
(2) An immovable element of a machine 
which is also its armature. 

Stator Circuit.— The circuit of the stator 
coils. 

Stator Coils. — The coils placed on the sta- 
tor of a dynamo or motor. 

Stator Currents. — Currents that flow in 
the stator of a dynamo or motor. 

Stator Field. — A field of a dynamo or mo- 
tor that remains at rest during operation. 

Statute Mile. — A length employed in 
Great Britain equal, by statute, to 5280 
feet. 

Stauroscope. — A form of polariscope for 
investigating the effects of polarized light 
on crystals. 

Stay-Eye Clip. — An iron band rigidly 
clamped to roof beams or other strong 
supports and carrying an iron ring for the 
attachment of a stay-rod. 

Stay Rod. — A rod of iron or steel, used to 
stay or support a telegraph or telephone 
pole. 

Stay Tightner. — A swivel for taking up 
slack in a stay. 



Steady Current.— A current whose 
strength does not vary from time to time. 

Steam Dynamo.— (1) A name applied to 
a steam-turbine dynamo. (2) A dynamo 
direct-connected to a steam engine. 

Steam Governor, Electric. — A device 
used in connection with a valve to so 
electrically regulate the supply of steam 
to an engine that the engine shall be 
driven at such a speed as will maintain 
either a constant current, or constant 
potential. 

Steam-Turbine Dynamo.— A high-speed 
dynamo whose armature is driven by 
means of a steam turbine. 

Steaming Lights, Electric— A term 
sometimes applied to the side lights of a 
ship. 

Steam's Relay Shunt.— A shunt em- 
ployed in the differential method of du- 
plex telegraphy to short-circuit the relay 
and then permit the line current to be cut 
off directly after it has completed its work 
in closing the local circuit. 

Steel Facing of Electro-Type.— A thin 
electrolytic deposit of iron placed on the 
surface of an electro-type for the purpose 
of hardening it. 

Steel- Yard Ammeter.— A form of am- 
meter in which the strength of a current 
is measured by means of the electro-mag- 
netic forces applied to one extremity of a 
steel-yard lever, provided with sliding 
weights for balancing these forces. 

Steeps. — A word sometimes employed in 
electro-plating for dips or dipping liquids 
or solutions. 

Steering Compass. — A compass employed 
for the steering of a ship. 

Steering, Electric. — Steering effected 
electrically. 

Steering Telegraph. — A telegraph on 
board ship for communicating steering 
orders from some point such as the bridge 
or conning tower. 

Steno-Telegraphy. — A system of tele- 
graphy in which the sounds of a word are 
represented by characters instead of by 
letters. 

Step-by-Step Annunciator. — An an- 
nunciator operated on the step-by-step 
principle. 

Step-by-Step Telegraphy,— (1) A sys- 
tem of telegraph}^ in which the signals 
are registered by the movements of a 
needle over a dial on which the letters of 
the alphabet are marked. (2) Dial teleg- 
raphy. 



Ste.] 



941 



[Sto. 



Step-Down Converter.— A step-down 
transformer. 

Step-Down Transformer.— (1) A trans- 
former in which a small current of com- 
paratively great difference of potential is 
converted into a large current of com- 
paratively small difference of potential. 
(2) An inverted Ruhmkorff induction coil. 

Step-Up Converter.— A step-up trans- 
former. 

Step-Up Transformer.— A transformer 
in which a large current of comparatively 
small difference of potential is converted 
into a small current of comparatively 
great difference of potential. 

Steradian.— (1) A unit of solid angle. (2) 
The solid angle subtended at the centre 
of a sphere of unit radius by a unit of 
spherical area, or unit of surface on the 
sphere. 

Stereopticon. — A lantern apparatus for 
projecting on a screen a stereoscopic 
picture. 

Stereoscope. — An optical apparatus for 
obtaining from two photographic pic- 
tures, taken in slightly different positions, 
pictures correctly representing solid ob- 
jects. 

Stereoscopic. — Of or pertaining to a ster- 
eoscope. 

Stereotype. — A fac-simile or duplication 
of a page of movable types or of engrav- 
ings, effected by obtaining a moulding of 
the original in some suitable material, and 
then immersing the mould in melted type 
metal. 

Sterilization, Electric— Sterilizing a so- 
lution by depriving it, by means of elec- 
tric currents, of whatever germs it may 
contain. 

Stern Sheave. — (1) A large sheave on the 
stern of a cable-ship for paying out cable. 
(2) Any sheave at the stern of a boat or 
vessel used in paying out cable. 

Stethoscope. — An instrument for ascer- 
taining the condition of the organs of cir- 
culation and respiration by the sounds 
they produce. 

Sticking. — (1) A name given by teleg- 
raphers to the failure of a relay arma- 
ture to leave the magnet pole and break 
contact on the cessation of the current. 
(2) Undue adhesion between the contacts 
of a relay. 

Sticking of Magnetic Armature.— The 
adherence of the armature of any electro- 
magnet to its poles after the current has 
ceased to pass through the magnetizing 
coils. 



" Stiff Field."— A magnetic field of com- 
paratively high density. 

Stilography.— A modified form of glyph- 
ography. 

Stimulus of Nerve, Electric— The effect 
which electricity produces by its passage 
through a nerve. 

Stock Ticker.— A step-by-step printing 
telegraphic instrument, employed in 
transmitting stock quotations to brokers' 
offices from stock exchanges. 

Stock-Ticker Service.— A term em- 
ployed for the transmission of stock quo- 
tations from stock exchanges to sub- 
scribers. 

Stoneware Dipping-Bowl.— A perfo- 
rated bowl made of stoneware, in which 
articles are placed that are to be subjected 
to the dipping process in electro-metal- 
lurgy. 

Stoneware Dipping-Basket.— A stone- 
ware dipping bowl. 

Stopped-Off.— Subjected to the stopping- 
off process. 

Stopper Incandescent Lamp.— An in- 
candescent lamp in which the mounted 
filament, instead of being hermetically 
sealed in the lamp chamber, is placed 
therein by means of a tightly fitting 
stopper. 

Stopper Lamp. — A stopper incandescent 
lamp. 

Stopping-Off.— A process employed in 
electro-plating, in which a metallic article, 
already electro-plated over its entire sur- 
face, is electro-plated with another metal 
over certain parts only. 

Stopping-Off Process.— A process em- 
ployed in electro-plating by means of 
which an article which is to be electro- 
plated on portions of its surface only with 
one metal, and on other portions with 
another metal, is first completely covered 
by an electro-plating of the cheaper metal, 
and then stopped-off by covering, with a 
coating of non-conducting varnish, such 
portions only of its surface as are not to 
receive the deposit of the more precious 
metal. 

Stopping-Ofi Varnish.— A varnish used 
in electro-plating to cover portions which 
are not to receive the metallic coating. 

Stopping-Out Process.— A process em- 
ployed in electro-typing, by means of 
which those parts of an electro-type 
mould that are not to be copied in the 
electro-type are covered with clean hot 
wax. 

Storage Accumulator. — A term some- 
times used for storage battery. 



Sto.] 



942 



[Str. 



Storage Battery. — A number of separate 
storage cells connected so as to form a 
single electric source. 

Storage-Battery Car.— An electric car 
which carries the storage battery em- 
ployed for its propulsion. 

Storage-Battery Meter.— A meter con- 
nected with a storage battery for the pur- 
pose of indicating the electric quantity, 
or energy, left in the same. 

Storage-Battery Traction. — Electric car 
traction obtained by means of storage 
batteries. 

Storage Capacity. — The capacity of a 
storage battery, as measured in ampere- 
hours. 

Storage Cell. — (1) Two relatively inert 
plates of metals or metallic compounds 
immersed in an electrolyte incapable of 
acting on them until after an electric cur- 
rent has been passed through the liquid 
from one plate to the other, and has thus 
changed their chemical relations. (2) 
One of the cells required to form a sec- 
ondary battery. (8) A term sometimes 
given to the jar containing a single cell. 

Storage-Cell Tester. — A convenient form 
of electrode provided for ready attach- 
ment to the individual cells of a storage 
battery, for the purpose of ascertaining 
their electromotive forces from time to 
time. 

Storage of Electricity .—A term improp- 
erly employed to indicate such a storage 
of energy as will enable it to directly re- 
produce electric energy. 

Storage of Energy. — The change from 
any form of kinetic energy to any form 
of potential energy. 

Storm, Electric. — (1) Any unusual con- 
dition of the atmosphere as regards the 
quantity or distribution of its free elec- 
tricity. (2) A thunder storm. 

Stove-Plate, Electric— An electrically 

heated stove-plate. 
Straggling Flux.— Leakage flux. 
Straight Connector.— A connector for 

coupling two wires in the same straight 

line. 
Straight- Filament Incandescent 

Lamp. — An incandescent lamp provided 

with a straight filament. 
Straight-Line Insulator. — An insulator 

employed for a trolley line, where the 

conductor is supported by transverse 

wires from poles placed on either side of 

the roadway. 
Straight-Line Suspension . — Suspension 

by means of a straight-line trolley hanger. 



Straight-Line Trolley Hanger.— A trol- 
ley hanger employed on a straight trolley 
line, suitably supported by a span wire so 
as to have a vertical strain only. 

Straightaway Bunched Cable. — A 
bunched cable, the separate conductors 
of which are placed in successive layers, 
and extend in the direction of the length 
of the cable without any twisting, as dis- 
tinguished from a helically wound cable. 

Strain. — The deformation produced by the 
action of a stress. 

Stranded Conductor.— A conductor 
formed of a number of smaller interlaced 
or twisted conductors, either for the pur- 
pose of reducing self-induction, or eddy 
currents, or for increasing its flexibility. 

Stranded Core.— A core whose conductor 
is stranded, as opposed to a core whose 
conductor is a solid wire. 

Stranded Feeder Conductor.— A feeder 
conductor formed of stranded wires. 

Stranded Line.— A line formed of a 
stranded conductor. 

Stranding of Conductor. — Forming a 
conductor of a number of separate con- 
ductors or strands. 

Strap Coppers. — Copper conductors 
formed of bars or straps, employed in con- 
nection with a bar-armature winding. 

Strap-Driven.— A term sometimes em- 
ployed for belt-driven. 

Strap Key. — A key made from an elastic 
strip or strap of metal. 

Strap Switch. — A switch made from a 
strip or strap of metal. 

Straps and Climbers. — A device em- 
ployed by line-men for climbing wooden 
telegraph poles. 

Stratham's Electric Fuse.— A form of 
fuse in which the ignition is effected by 
an electric spark. 

Stratification Tube. — A vacuum tube 
whose residual atmosphere displays alter- 
nate dark and light strise, or stratifications, 
on the passage through it of an induction- 
coil discharge. 

Stratified. — Arranged in separate layers 
or strata. 

Stratified Discharge. — The alternate 
light and dark spaces assumed by the dis- 
charge of an induction coil through a 
partially exhausted gas. 

Stray Chain. — In submarine cable-work, 
a length of chain which attaches the end 
of a buoyed cable to the mushroom anchor 
mooring chain. 

Stray Currents. — A term sometimes used 
for eddy currents. 



Str.] 



943 



[St] 



Stray Field. — (1) Leakage magnetic flux. 
(2) That portion of a magnetic field which 
does not pass through an armature or 
other magneto-receptive device. 

Stray Flux.— The flux of a stray field. 

Stray Power. — That portion of the power 
applied to drive a machine which is lost 
by various frictions. 

Stream-Lines of Escaping Fluid.— 
Lines which show the actual paths of the 
particles of an escaping fluid. 

Streamers. — Pillars or parallel flashing- 
columns of light frequently seen during 
the prevalence of an aurora. 

Streaming Discharge.— A form assumed 
by a flaming discharge between the sec- 
ondary terminals of an induction coil, 
when the frequencies of the alternations 
increase beyond a certain limit, and the 
potential is consequently increased. 

Streamings.— (1) A term sometimes em- 
ployed for electrostatic or electro-mag- 
netic flux. (2) X-ray streamings. 

Street Call-Point in Fire Telegraphy. 
Any point in a street where an alarm 
call-box is placed. 

Street- C!ar Controller. — (1) An electric 
switching apparatus contained in a box 
placed on the platform of an electric 
street-car, and employed to control the 
speed of the car. (2) A car-controller. 

Street-Car Lamp. — An incandescent lamp 
provided with an anchored filament, suit- 
able for use in a street-car. 

Street-Car Motor. — A motor employed 
for the propulsion of a trolley car. 

Street-Car Recording Watt-Meter.— A 
wattmeter designed for use on a street- 
car for registering the amount of electric 
energy delivered to a car in a given time. 

Street Load-Diagram.— A diagram show- 
ing the electric load on each street of any 
particular district of electric supply. 

Street Mains. — In any system of electric 
distribution, the conductors extending 
through the streets from junction box to 
junction box, through which the current 
is distributed from the feeders, and from 
which service wires are taken. 

Street Railway, Electric,— (1) Any elec- 
trically propelled street railway. (2) The 
ordinary trolley system of electric car 
propulsion. 

Street Service. — (1) In a system of in- 
candescent-lamp distribution that portion 
of the circuit which is included between 
a main and the service cut-out. (2) That 
portion of service conductors which lies 
outside of the building served. (3) In a 



system of electric distribution including 
street lighting, service wires supplying 
street lamps. 
Strength of Current.— (1) A general term 
for tiie magnitude of the current in a cir- 
cuit. (2) Amperage. 

Strength of Magnetic Field. — The mag- 
netic force acting on a free unit magnetic 
pole placed in any magnetic field. 

Strength of Magnetism. — A term some- 
times used for intensity of magnetization. 

Stress. — The pressure, pull or other force, 
producing a deformation or strain. 

Stress Flux. — (1) A general term for the 
flux producing any stress. (2) The sur- 
face integral of stress passing through a 
surface. 

Stretching Insulator. — An insulator of 
extra mechanical strength provided with 
means for carrying a short extra length 
of wire, twisted around a stem such that 
the excess can be employed for making a 
joint, or for other purposes. 

Striae, Electric— Parallel streaked bands, 
consisting of alternate light and dark 
spaces, produced in low-vacuum tubes by 
an electric discharge through them. 

Striking. — Subjecting an article to the 
action of a striking bath. 

Striking an Arc. — Separating the carbon 
electrodes for the formation of an arc be- 
tween them. 

Striking Bath. — A bath containing less 
silver and a greater proportion of free 
cyanide, employed in silver plating, for 
obtaining an almost instantaneous deposit 
of silver before subjecting the object to 
the regular plating bath. 

Striking Distance. — A term sometimes 
employed for sparking distance, or the 
distance through which a disruptive dis- 
charge will pass. 

Striking Mechanism of Arc Lamp.— 
The mechanism employed in an arc-lamp 
to separate the carbons on the establish- 
ment of the arc. 

Stringing Wires. — Placing aerial wires on 
poles or other supports. 

Strip Commutator. — A commutator 
formed of plates or flat strips as opposed 
to a commutator whose segments are 
strips placed edgewise. 

Strip Fuse. — A name sometimes applied 
to a safety strip. 

Strip Resistance. — A resistance formed 
of strip or strap conductors. 

Stripping. — Dissolving the metal coating 
from a silver, gold or other plated article. 



Str.] 



944 



[Sub. 



Stripping Bath.— A bath employed for 
removing an electro-plating of gold, silver 
or other metal, either by simple dipping 
or by electric action. 

Stripping Liquid. — (1) The liquid em- 
ployed in a stripping bath. (2) The 
liquid employed to remove the coating of 
one metal from the surface of another 
■without affecting the other metal. 

Stroboscope. — An instrument employed 
in the study of periodic motion. 

Stroboscopic. — Of or pertaining to the 
stroboscope. 

Stroboscopic Disc— A disc employed in 
a stroboscope. 

Strong-Current Arrester.— Any form of 
arrester suitable for protecting a line 
from a strong current produced by ac- 
cidental contact with a trolley, power or 
lamp circuit. 

Struck. — A word employed in electro-plat- 
ing to characterize a surface that has been 
covered with a film of electrolytically de- 
posited silver or nickel, by being placed 
in a bath and exposed for a few moments 
to the action of a strong current. 

Structural Carbon. — A term applied to a 
carbon lamp-filament obtained by the car- 
bonization of any structural carbonizable 
material such as bamboo. 

Structural Magnetic Flux.— (1) Mag- 
netic flux produced by the alignment of 
the individual molecular magnets in iron, 
steel or other magnetic substance. (2) 
Magnetic flux produced by means of a 
structural magneto-motive force. (3) 
Magnetic flux produced by iron or other 
magnetic metal as opposed to flux pro- 
duced by electric currents. 

Structural Magneto-Motive Force.— 

(1) A name sometimes given to an aligned 
or induced magneto-motive force, in order 
to distinguish it from the prime magneto- 
motive force. (2) A magneto-motive 
force produced by aligning or structurally 
arranging the molecular magneto-motive 
forces inherent in iron, steel, or other 
magnetic substance. 
Structureless Carbons.-— A term some- 
times applied to carbon filaments that are 
obtained by the carbonization of a struct- 
ureless material, such as tamadine or 
celluloid. 

Struts for Telegraph Poles.— Inclined 
wooden or iron props applied to telegraph 
poles in order to resist thrusts or pressures. 

Sturgeon's Wheel. — A name sometimes 
applied to Barlow's wheel. 

Sub- Aqueous. —Under water. 

Sub- Aqueous Cable.— (1) A cable em- 



ployed for use under water, generally 
under fresh water, as in crossing a river. 
(2) A river cable as distinguished from a 
sea cable. 
Sub-Branch. — A term sometimes em- 
ployed for a branch taken out of or tapped 
from a branch. 

Sub-Centre Transformer. — A trans- 
former placed at, and supplying secondary 
circuits radiating from, a sub-centre of 
distribution. 

S u b-D ivided Conducto r.— (1) A 

stranded conductor. (2) A compositely 
formed conductor. (3) A multiple-wire 
conductor. 

Sub-Divided Transformer.— (1) A trans- 
former having subdivisions in its primary 
or secondary coils. (2) A transformer 
having a sub-divided magnetic circuit. 

Sub-Exchange for Telephones. — A 
local exchange in connection with a cen- 
tral exchange. 

Sub-Mains. — (1) Conductors which branch 
off from the mains. (2) Mains which are 
themselves branches of mains. 

Sub-Marine.— Under the sea. 

Sub-Marine Boat, Electric— A boat 
capable of being propelled and steered 
while under water. 

Sub-Marine Board.— (1) A complete set 
of sub-marine cable telegraphic instru- 
ments mounted on a board. (2) A sub- 
marine cable testing board. 

Sub-Marine Cable.— A cable designed for 
use under water, generally under the 
ocean. 

Sub-Marine Finder. — A form of induc- 
tion balance proposed for the location of 
torpedoes, anchors, iron ships or other 
metallic submerged articles. 

Sub-Marine Fuse. — A fuse employed for 
the ignition of a sub-marine mine. 

Sub-Marine Key. — A key suitable for use 
in sub-marine telegraphy. 

Sub-Marine Mine.— A mass of gun-cot- 
ton or other explosive material contained 
in a water-tight vessel and placed under 
water so as to explode on the passage of 
an enemy's vessel over it. 

Sub-Marine Search Light.— An incan- 
descent light employed for sub-marine 
exploration. 

Sub-Marine Sentry .—A device sometimes 
employed in sub-marine cable work for 
indicating the presence of very shallow 
water, and consisting of a water kite 
which is below the vessel and which rises 
to the surface when it strikes the sea-bot- 
tom. 



Sub.] 



945 



[Sup. 



Sub-Marine Telegraph.— A general term 
for the apparatus employed in sub-marine 
telegraphy. 

Sub-Marine Telegraphy.— (1) A system 
of telegraphy in which the line wire con- 
sists of a sub-marine cable. (2) A system 
of telegraphy across oceans. 

Sub-Marine Telephony. — Telephony 
carried on by means of sub-marine cables. 

Sub-Permanent Magnetism.— A term 
sometimes employed for the character 
of the magnetism in an iron ship, as dis- 
tinguished from that of a magnetized steel 
bar, and as indicating that the perman- 
ence in the magnetism of the former is 
not as marked as in that of the latter. 

Subscriber's Indicator. — In a telephone 
switchboard, the indicator or drop con- 
nected in a subscriber's circuit and oper- 
ated by his call. 

Subsidiary Distributing Board.— A dis- 
tributing board auxiliary to a multiple 
telephone switchboard, and from which 
the subscribers' lines are portioned to the 
local spring jacks for the various opera- 
tors, in order to equally distribute their 
work. 

Sub-Station. — An auxiliary station. 

Sub-Station Accumulator. — An accum- 
ulator employed at sub-stations, or aux- 
iliary centres of distribution. 

Sub-Station Transformer. — A trans- 
former employed at an auxiliary station 
or sub-station. 

Substitute Primary Coil.— (1) A secon- 
dary-primary coil. (2) An intermediate 
coil in a transformer which alternately 
takes the part of a secondary and primary. 

Substitution Method.— A method of 
measuring resistances, currents, electro- 
motive forces, etc., by removing them 
from a circuit and replacing them by a 
known or adjustable corresponding resist- 
ance, current or electromotive force. 

Subterranean. — Under the earth. 

Subterranean Mine. — An underground 
mass of gunpowder, or gun-cotton or 
other high explosive, placed in suitable 
vessels for protection against moisture, 
provided with an electrically connected 
fuse, which is either exploded automati- 
cally on the movement of an enemy over 
it, or by a distant operator. 

Sub-Transformer Station.— In a system 
of electric distribution by alternating cur- 
rents, an auxiliary station at which trans- 
formers are placed for local secondary dis- 
tribution . 

Sub-Trunk Telephone Line.— (1) An 
6o 



auxiliary trunk telephone line. (2) A 
trunk line connecting telephone ex- 
changes and used for making connections 
with trunk lines. 

Suburban Communication. —Tele- 
phonic or telegraphic communication be- 
tween the suburbs and central portions of 
a city. 

Suburban Electric Railway.— An elec- 
tric railway connecting the centre of a 
city with the suburbs. 

Subway, Electric. — An accessible under- 
ground way or passage provided for the 
reception of electric-light wires or cables. 

Successive-Contact Key.— Any form of 
key employed to make two or more suc- 
cessive contacts. 

Sugg. — A name sometimes given to a stand- 
ard British candle. 

Sulphatmg. — A name applied to one of the 
sources of loss in the operation of a stor- 
age cell, by means of the formation of an 
inert coating of lead sulphate on the sur- 
face of the battery plates. 

Summer Lightning. — A name sometimes 
given to heat lightning. 

Sunflower Commutator.— (1) A com- 
mutator resembling a sunflower in ap- 
pearance. (2) A form of flat or disc com- 
mutator. 

Sun-Light Color- Values. — Such lumin- 
ous frequencies in a source of artificial 
light as will give to its light the same 
effects as are produced by sunlight. 

Sunshine. — The luminous radiant energy 
emitted by the sun. 

Sun-Spot Disturbance. — Any disturb- 
ance due to, attributed to, or accompany- 
ing, the presence of spots on the sun. 

Sun-Spots. — Dark spaces, varying in num- 
ber and position, which appear on the sur- 
face of the sun. 

Sun-Stroke, Electric— (1) Electric pros- 
tration produced by exposure to the light 
of an electric arc. (2) Physiological ef- 
fects similar to those produced by ex- 
posure to the sun, experienced by those 
exposed for a long time to the intense light 
and heat of the voltaic arc. 

Sun Telegraph. — A name sometimes ap- 
plied to the heliograph. 

Sunk Winding. — (1) A name sometimes 
employed for an iron-clad winding. (2) 
A winding sunk below the surface of an 
armature or other device. 

Superficial Eddy-Currents. — Eddy cur- 
rents produced in conducting substances 
that are limited to the outer layers 
thereof. 



Sup,] 



946 



[Sus. 



Superficial Field. — A field produced by 
the super-position of two or more sep- 
arate fields. 

Superposed Magnetism.— A term ap- 
plied to a magnetism impressed on an 
already magnetized substance. 

Super-Saturation. — A condition of a 
solution which has been allowed to cool, 
while out of contact with air, below its 
point of crystallization or solidification. 

Super-Saturation of Solution. — The 
condition assumed by a warmed saturated 
solution of a salt when placed in a closed 
vessel out of contact with the air. and al- 
lowed to cool, without being shaken. 

Supervising Operators.— In telephony, 
or telegraphy, operators whose duty it is 
to supervise the work of other operators. 

Supplement of Angle.— What an angle 
needs to bring its value to 180°. 

Supplementary Dynamo.— A word 
sometimes used for a booster dynamo. 

Supply Conductors. — (1) A term some- 
times applied to the sub-mains in a system 
of incandescent light distribution. (2) 
Conductors which convey electric energy. 

Supply Mains. — A term sometimes ap- 
plied to the mains in a system of incan- 
descent light or power distribution. 

Supply Meter, Electric. — A meter which 
indicates or measures the electricity or 
electric energy supplied to a given cus- 
tomer or machine. 

Supply Unit. — A name proposed for the 
Board of Trade unit. 

Support Plate of Storage Cell.— A term 
sometimes employed for the grid of a 
storage cell. 

Surface Action. — Any action limited to 
a surface. 

Surface Contact of Street-Railway 
Car. — A contact, flush with the surface 
of a street, and intended for use in con- 
nection with the electric propulsion of a 
street-railway car. 

Surface Contact-Resistance between 
Metal and Liquid.— The resistance in- 
troduced into a primary or secondary cell 
at the contact between the metal and 
liquid. 

Surface Contact Street Railway Sys- 
tem. — A system of street-railway pro- 
pulsion employing surface contacts. 

Surface Density.— The quantity of elec- 
tricity-per-unit-of-area at any point on a 
charged surface. 

Surface-Efficiency of Filament.— (1) 

The efficacy of a particular character of 
surface for luminous radiation. (2) The 



luminous efficiency of a particular charac- 
ter of surface in a filament. 

Surface Integral.— (1) The sum of all 

the products of a point function and its 
associated element of area, lying on a 
surface, when the elements are all in- 
definitely small. (2) The integral of a 
quantity taken over a surface. 

Surface Integral of Magnetic Induc- 
tion. — The total magnetic flux passing 
through a surface. 

Surface Magnetization.— In the distri- 
bution of imaginary magnetic matter, 
the magnetism residing on a surface, or 
the so-called free magnetism. 

Surface-Wound Armature.— (1) An ar- 
mature wound on its surface, as distin- 
guished from an iron-clad armature. (2) 
An armature in which the conductors lie 
over the surface of the core, instead of 
being placed in grooves or slots formed 
therein. 

Surfusion. — A word sometimes employed 
for super-saturation. 

Surgical Lamp. — A lamp employed in 
surgical exploration, examination, or oper- 
ation. 

Surging Circuit. — Any circuit through 
which a surging discharge is passing. 

Surging Discharge.— (1) A discharge ac- 
companied by electric surgings. (2) An 
oscillatory discharge. 

Surgings, Electric— (1) Electric oscilla- 
tions set up in a conductor that is under- 
going rapid discharging, or in neighbor- 
ing conductors that are being rapidly 
charged and discharged. (2) Electric 
oscillations, direct or induced. 

Susceptance. — In an alternating-current 
circuit, branch, or conductor, the quan- 
tity whose square added to the square of 
the conductance is equal to the square of 
the admittance. 

Susceptibility. — A word sometimes used 
for magnetic susceptibility. 

Suspended Cable-Way. — A modification 
of the telpherage system, in which a car- 
riage provided with one or more grooved 
wheels is electrically driven over a sus- 
pended cable. 

Suspended-Coil Galvanometer.— Any 

form of galvanometer in which the cur- 
rent passing is measured by the move- 
ments of a suspended coil. 

Suspended Trolley-Way.— (1) A sus- 
pended cable- way. (2) A form of tele- 
pherage system. 

Suspender. — A word sometimes used for 
a cable suspender. 



Sus.] 



947 



[Swt 



Suspender for Telephone Cable.— (1) 
A word sometimes employed for cable 
hanger. (2) A hook or support for a 
telephone cable. 

Suspending Hook for Telephone 
Cable. — A cable hanger. 

Suspending Wire of Aerial Cable.— (1) 
The wire from which an aerial cable is 
strung or suspended. (2) A messenger 
wire. 

Suspension. — (1) The mechanism for sus- 
pending a thing, with or without the 
thing suspended. (2) The means employed 
in suspending any system, such as a 
needle, a pendulum, or a car motor. 

Suspension for Car-Motor.— The means 
employed for supporting a car-motor on 
a car truck. 

Sustained Currents, Electromotive 
Forces or Fluxes. — Any electromotive 
force, current or flux, whose effect is con- 
tinued, as distinguished from one whose 
effect is temporary. 

Swage. — A particular form of anvil on 
which highly heated metallic plates are 
shaped by hammering them into forms 
the same as that of the anvil on which 
they are placed. 

Swage. — To fashion heated metallic plates 
by hammering them into the form of the 
anvil on which they are supported. 

Swaging. — Fashioning highly heated me- 
tallic plates into any desired form by ham- 
mering, while on suitable dies. 

Swaging, Electric. — Forming or shaping 
of metallic plates by hammering them 
against suitable anvils or dies while soft- 
ened by electric heat. 

Sweating. — A term employed for the proc- 
ess of soldering together the ends of 
electric-light cables. 

dwelling Current. — In electro-thera- 
peutics, a current that begins weak and 
is then periodically made stronger and 
weaker. 

Swelling Faradic-Currents.— A term 
employed in electro-therapeutics for 
Faradic currents that are caused to grad- 
ually increase in strength and then to 
gradually decrease to zero strength. 

Sweep. — (1) In submarine cable work, a 
drag. (2) In submarine cable work, a 
haul made with a grapnel across a line of 
cable. 

Sweeper, Electric— A term employed 
for an electrically-driven sweeper. 

Sweeping-Out Charge.— A phrase em- 
ployed in double-current signalling for 
freeing the line from a charge produced in 



sending one signal, by reversing the di- 
rection of the current through the line 
before sending the next signal. 

Swinging Annunciator. — A pendulum 
annunciator. 

Swinging Cross. — A term sometimes 
given to an intermittent cross. 

Swinging Earth.— A name sometimes 
given to an intermittent earth. 

Swinging Voltmeter.— A voltmeter 
mounted upon a swinging bracket of a 
switchboard, so as to be capable of being- 
read from any direction. 

Swiss Commutator Switchboard.— A 
switchboard having cross-bars after the 
type of a Swiss commutator. 

Switch.— (1) Any device for readily open- 
ing or closing an electric circuit. (2) In 
telephony, a name sometimes given to a 
switchboard. 

Switch-Bell.— (1) A bell switch. (2) A 
combination of a bell and switch. 

Switch Blade. — A conducting strip or 
knife-blade of a switch. 

Switch-Board. — (1) A board, base, slab or 
frame of insulating material, upon which 
are supported conducting bars, pieces, 
frames or masses, with or without switches 
and instruments, for the ready establish- 
ment of electrical connections between 
circuits connected therewith. (2) A board 
carrying switches and instruments for 
controlling a distribution system and the 
generators connected therewith. (3) A 
board provided with a switch or switches 
by means of which electric circuits con- 
nected therewith may be opened, closed 
or interchanged. (4) In a central station 
for telegraphy, telephony, light or power 
distribution, the electric controlling me- 
chanism. 

Switch Cord. — An insulated conducting 
cord connected w T ith a switch. 

Switch-Board Arrester. — A device in- 
tended for use on switchboards, consist- 
ing either of some form of lightning ar- 
rester or of a sneak-current arrester. 

Switch-Board Bolt. — A bolt for mechan- 
ically fastening apparatus to a switch- 
board or the panels of a switchboard to a 
frame. 

Switch-Board Bracket. — A bracket on a 
switchboard for supporting an incandes- 
cent lamp or other device. 

Switch-Board Cable.— Any cable con- 
nected with a switchboard. 

Switchboard Fittings.— A general term 
embracing the connectors, set screws, 
wire-holders or bus-bar connections, em- 



SwL] 



948 



[Syn. 



ployed in placing the different apparatus 
on a switchboard. 
Switch-Board Protector.— (1) A pro- 
tector provided with a suitable electro- 
magnetic safety device, or with a fuse wire 
or safety catch, placed at cable heads, at 
the junction between aerial-land and un- 
derground lines, for the purpose of pro- 
tecting the cable from a too powerful 
electric discharge or current. (2) Any 
lightning, or circuit protector, placed on 
a switchboard. 

Switchboard Transformers.— Trans- 
formers on an alternating-current switch- 
board for locally supplying alternating- 
currents of reduced pressure. 

Switch-Board Wattmeter. — A wattme- 
ter placed on a switchboard to determine 
the out-put, or the intake, of some circuit 
connected therewith. 

Switch-Box. — Any box containing one or 
more switches. 

Switch-Finger. — A contact-finger, or pro- 
jecting metallic contact on the cylinder 
of a street-car controlling-switch, or on 
similar apparatus. 

Switch-Handle, Electric— In electric 
railway block-signalling, a miniature rail- 
way electric switch handle for closing 
and opening an electric circuit. 

Switch Hole. — A hole provided in a 
switch key for the insertion of a plug. 

Switch Hook. — (1) An automatic tele- 
phone hook. (2) A hook which serves 
the purpose of a switch. 

Switch Jack. — A spring jack. 

Switch Pin. — A metallic pin or plug pro- 
vided for insertion in a switchboard. 

Switch Room. — The room or hall in a 
central telephone exchange in which a 
switchboard is placed. 

Switch Spring 1 . — A spring placed in a 
switch for its mechanical operation, or for 
securing electric connection. 

Switched-In. — Thrown into a circuit by 
means of a switch. 

Switched-Out. — Removed from a circuit 
by means of a switch. 

Swivel Clevis. — A device consisting es- 
sentially of a nut and bolt, by means of 
which any slack in a guy-rod may be taken 
up. 

Symmetrical Alternating Current.— 

Any alternating current whose successive 
semi-periods, waves, or alternations pos- 
sess opposite but equal values, or corre- 
spond in all respects save in direction. 
Symmetrical Alternating Electro- 
motive Forces. — Electromotive forces 



whose successive semi- waves or alterna- 
tions possess equal but opposite values, or 
correspond in all respects save in direc- 
tion. 

Symmetrical Induction of Armature. 

— (1) An induction produced by the sim- 
ultaneous passage of the same quantity 
of magnetic flux through adjoining 
halves of the armature. (2) A sym- 
metrical magnetization in an armature. 

Symmetrical Magnetic Field.— A field 
whose magnetic flux is symmetrically 
distributed. 

Symmetrical Polyphase System. — 
A polyphase system symmetrically ar- 
ranged in regard to conductors, pressures, 
currents and loads. 

Sympathetic Electric Vibrations. — 
(1) Electric vibrations produced in a cir- 
cuit by the electro-magnetic waves given 
off by a neighboring circuit. (2) Electric 
vibrations that are produced by reso- 
nance. 

Sympathetic Generator.— An induction 
generator. 

Sympathetic Vibrations. — Vibrations 
set up in bodies, and having the same 
frequency as that produced by the excit- 
ing body. 

Syrnphonance. — A word proposed in place 
of resonance. 

Synchronism. — (1) Unison of frequencies 
in alternating-current systems or appara- 
tus. (2) The simultaneous occurrence of 
any two events. (3) Generally, the co- 
periodicity and co-phase of two periodi- 
cally recurring events. (4) The coinci- 
dence in cyclic recurrence of two or more 
periodic variables, without regard to am- 
plitude. 

Synchronizable. — Capable of being syn- 
chronized. 

Synchronize.— (1) To cause to occur or 
act simultaneously. (2) To bring two 
alternating-current machines into unison 
or co-periodicity, and into practical coin- 
cidence of phase, so that they may be con- 
nected together. 

Synchronized. — Caused to occur or act 
simultaneously. 

Synchronizer. — (1) Anything causing or 
tending to cause synchronism. (2) A 
phase indicator. (3) A device for indi- 
cating when synchronism is attained be- 
tween alternators that are to be connect- 
ed in parallel. 

Synchronizing Dynamo-Electric Ma- 
chines. — Adjusting the frequencies and 
phases of two alternating-current dyna- 



Synj 



949 



[Tai, 



mos so as to permit of their being coupled 
or joined in parallel. 

Synchronizing Torque.— The torque of 
an alternating-current generator or motor 
armature tending to bring it into syn- 
chronism with some other armature oper- 
ated with it. 

Synchronograph. — A name given to a 
record obtained by a polarizing photo- 
electric apparatus. 

Synchronous.— (1) Occurring simulta- 
neously in point of time. (2) Generally, 
co-periodic and co-phasal, as distin- 
guished from isochronous, which connotes 
agreement in period only. 

Synchronous Generator.— A generator 
of alternating currents, operating or 
capable of operating in synchronism with 
another generator. 

Synchronous Motor. — A form of alter- 
nating-current motor which requires to be 
brought into step with the driving cur- 
rent before it will properly operate. 

Synchronous Multiphase Motor. — 
A multiphase motor designed to operate 
in isochronism with the generator or gen- 
erators connected with it. 

Synchronous Multiplex Telegraph. — 
A general term for the apparatus em- 
ployed in synchronous multiplex teleg- 
graphy. 



Synchronous Multiplex Telegraphy.— 

A system of simultaneous telegraphic 
transmission in which a number of mes- 
sages, either all in the same direction, or 
part in one and the remainder in the op- 
posite direction, can be simultaneously 
transmitted over a single line wire. 

Synchronous Reactance.— (1) The ap- 
parent reactance of a synchronous motor 
armature under working conditions 
(2) The combined apparent reactance of 
self-induction and armature reactance of 
a synchronous motor armature under 
working conditions. 

Synchronous Speed.— The speed of a 
motor or generator at which it is in syn- 
chronism with the current in the system 
to which it is connected. 

Synchronous Vibrations.— Vibrations 
produced by two or more separate sys- 
tems that exactly coincide, both in fre- 
quency and in phase. 

Synthesis. — (1) Indirect analysis or the 
formation of a chemical substance by the 
combination of its constituent parts. 
(2) The building-up or combination of 
atoms into molecules. 

System of Electric Lighting.— (1) A 
term sometimes applied to an electric 
light installation. (2) An electric light 
plant. 



t. — A symbol employed for time. 

t : m. — An abbreviation for turns-per-min- 
ute, a practical unit of angular velocity. 

T. P. Switch. — A contraction for triple- 
pole switch. 

T-Connector. — A connector provided for 
connecting a wire with two branch wires, 
and resembling the letter T in shape. 

T-Shaped Spark.— A variety of three- 
branched spark obtained by the discharge 
of a Leyden jar through a peculiar form 
of induction coil. 

Table-Key. — A key placed on the table of 
a telephone exchange for effecting the 
connections with an operator. 

Table Push. — A push-button connected 
with a table for ease in ringing a call-bell. 

Table Switch. — A switch on the table of 
a telephone switchboard. 

Tablet Board. — A switchboard divided 
into panels or tablets. 

Tablet Check. — In telegraphy, a tabulat- 
ed form upon which messages sent and 



received are checked off for the purpose 
of recording the traffic and ensuring 
against the loss of a message. 

Tachograph. — An apparatus for recording 
the number of revolutions per minute of 
a machine or shaft. 

Tachometer. — (1) An apparatus for indi- 
cating at any moment on a dial the num- 
ber of revolutions per minute of a shaft 
or machine with which it is connected. 
(2) A speed indicator. 

Tachyphore. — (1) A name proposed for a 
system of electric transportation in which 
a carriage formed of magnetic material is 
propelled by the sucking action of sole- 
noids placed along the tracks, and ener- 
gized in succession during the passage of 
the car. (2) A port-electric system. 

Tail Light. — A light displayed at the rear 
of a train, in order to avoid rear-end col- 
lisions. 

Tail of Mercury.— An elongation or tail, 
of grayish color, due to the presence ci 



Tai.] 



950 



[Tea. 



oxides, left behind a drop of impure mer- 
cury, when moved over smooth surface. 

Tailings. — (1) In telegraphy, residual dis- 
charges from the line through the receiv- 
ing instrument, following each signal, and 
thus tending to make the signals run to- 
gether. (2) Residual or return charges or 
currents in the transmission of electro- 
magnetic waves through a dielectric. 

Talantoscope. — A low-vacuum tube em- 
ployed in connection with a Hertzian os- 
cillator to determine when it is sending 
forth waves, and when it is under the in- 
fluence of undirectional discharges and 
is not sending forth waves. 

Talking Circuit. — In telephony, a circuit 
employed by a subscriber during conver- 
sion, as distinguished from a calling cir- 
cuit. 

Tamadine. — A modified form of tri-nitro 
cellulose, employed, when cut into suit- 
able shapes and subsequently carbonized, 
for the filaments of incandescent lamps. 

Tangent. — (1) One of the trigonometrical 
f unctions. (2) In a right-angled triangle 
formed by a radius-vector, base, and per- 
pendicular, the ratio of the perpendicular 
to the base. 

Tangent and Sine Galvanometer.— A 
galvanometer furnished with two mag- 
netic needles of different lengths, the 
small one being used for tangent meas- 
urements, and the long one for sine 
measurements of current strength. 

Tangent Galvanometer.— An instrument 
in which the deflecting coil consists of a 
coil of wire within which is placed a 
needle, supported at the centre of the 
coil, and very short by comparison with 
the diameter of the coil. 

Tangent Scale. — A scale designed for use 
with a tangent galvanometer on which 
the values of the tangents are directly 
marked, instead of degrees of the circle 
as ordinarily, thus avoiding the necessity 
of finding from tables, tangents corre- 
sponding to the degrees. 

Tangentially - Laminated Armature 
Core. — An armature core consisting of a 
closely-coiled ribbon of sheet iron. 

Tank-Heater, Electric— A form of elec- 
tric heater for heating liquids, consisting 
essentially of a heating coil immersed in 
a liquid contained in a tank. 

Tanning, Electric— The application of 
electric currents to the tanning of leather. 

Tap. — (1) A conductor attached as a shunt 
to a larger conductor. (2) A derived 
circuit for carrying off a share of the 
main current. (3) A wire taken from the 



junction between the short and long sec- 
tions of a quadruplex battery. 

Tap Wire in Quadruplex Telegraphy. 
The intermediate wire or conductor in a 
system of quadruplex telegraphy, which 
divides the battery into two unequal 
parts, called respectively the long side 
and the short side. 

Tap Wires. — The wires or conductors em- 
ployed in trolley systems to carry the 
current from the feeders or mains at a 
pole to a near point on the trolley wire. 

Taped Conductor. — A taped wire. 

Taped Wire. — (1) A conducting wire cov- 
ered with an insulating material in the 
shape of a tape. (2) A wire covered with 
an insulating material and subsequently 
taped. 

Tapered Mains. — Mains in the tree sys- 
tem whose diameters diminish in succes- 
sive sections. 

Taping. — (1) Covering a wire or a joint 
with an insulating tape. (2) A covering 
of tape applied to a cable sheathing. 

Tapers. — Wires tapering in diameter for 
the purpose of effecting a splice between 
two different types of submarine cables. 

Tapper Bell. — A single-stroke electric 
bell provided with a suitable key for sig- 
nalling purposes. 

Tapper Key.— A term sometimes em- 
ployed in place of a Morse tapper. 

Tapper Signal. — In a system of mining 
signals, signals sent or received by means 
of tapper bells. 

Tapping a Circuit.— Introducing a loop 
or branch in a telegraphic or telephonic 
circuit, for the purpose of intercepting 
the messages sent over the circuit. 

Taps. — A general term employed, in a sys- 
tem of incandescent lamp distribution, 
for branches or sub-branches that are 
carried from the mains into the rooms of 
a building or to the fixtures in the halls. 

Target, Electric. — A target in which the 
point struck by the ball is automatically 
registered by means of electric devices. 

Tasimeter. — An apparatus designed by 
Edison for the purpose of detecting 
minute heat changes by variations in the 
resistance of a soft-carbon disc, resulting 
from changes of pressure due to the ex- 
pansion of a substance exposed to the 
heat to be measured. 

Teaser. — An electric current teaser. 

Teaser, Electric. — (1) A coil of fine 
wire placed on the field magnets of a 
dynamo in a shunt across the main cir- 
cuit, in addition to the field magnet series 



Tea.] 



951 



[Tel. 



coil. (2) A series coil placed on a field 
magnet, in addition to a regular shunt 
field, for the purpose of preliminary ex- 
citation. 

Teaser Winding. — An additional coil 
wound on the armature of a monocyclic 
generator of smaller cross-section and 
fewer turns than the main winding, one 
end of which is connected at the centre 
of the main winding, and the other to a 
collecting ring. 

Tee Box for Underground Cables or 
Conductors. — A box, shaped like a letter 
T, and containing a joint or joints between 
a main line and an offset, branch, lateral, 
or service conductor. 

Tee Connector. — A T-shaped connector 
employed for readily connecting a wire 
at right angles to another wire. 

Teeth of Armature.— Polar projections 
or ridges on the surface of an armature- 
core, between which lie the armature 
windings or conductors. 

Tele-Anemograph. — A device for record- 
ing the indications of an anemograph at 
a distance. 

Tel-Autogram. — A recorded message ob- 
tained by means of a tel-autograph. 

Tel-Autograph. — A telegraphic system 
for the fac-simile reproduction of writing 
at a distance. 

Tele-Autograph. — An orthography some- 
times employed for tel-autograph. 

Tele-Barograph. — A device for recording 
the indications of a barometer at a dis- 
tance. 

Tele-Barometer, Electric. — An electric 
recording barometer, for indicating and 
recording barometric pressures at a dis- 
tance. 

Telegram. — Any despatch received by 
means of a telegraph. 

Telegraph. — (1) A general name for the 
instrument or combination of instru- 
ments employed for conveying a commu- 
nication or despatch to a distance by 
means other than that of the unassisted 
voice. (2) A general term for any appa- 
ratus employed in telegraphy. 

Telegraph. — To transmit a message by 
means of a telegraph. 

Telegraph Circuit.— (1) An electric cir- 
cuit employed in telegraphy. (2) An in- 
sulated line apparatus at one or more tele- 
graph stations and a ground return cir- 
cuit. 

Telegraph, Electric— A general term 
for any apparatus employed in electric 
telegraphy. 



Telegraph Line-Adjuster.— A general 
term given to apparatus by means of 
which the adjustment of a telegraph line 
is facilitated. 

Telegraph Loop.— A pair of wires ex- 
tending from a telegraphic station to a 
branch office. 

Telegraph Posts.— A term sometimes 
employed for telegraph poles. 

Telegrapher. — A telegraphic operator. 

Telegrapher's Cramp.— An affection of 
the hand of a telegrapher, due to con- 
tinuous excessive use of the same muscles, 
somewhat similar to the disease known as 
writer's cramp. 

Telegraphic— Of or pertaining to a tele- 
graph. 

Telegraphic Alarm.— An alarm bell for 
calling the attention of an operator to a 
telegraphic instrument when the latter is 
of the non-acoustic or needle type. 

Telegraphic Alphabet.— The code em- 
ployed for letters and other characters in 
telegraphy. 

Telegraphic Arm.— A cross-arm placed 
on a telegraphic pole for the support of 
the insulators. 

Telegraphic Box-Sounder.— A sounder 
whose receiving magnets are enclosed in 
a hollow box, for the purpose of increas- 
ing the intensity of the sound by reso- 
nance. 

Telegraphic Bracket.— A support or 
cross-piece placed on a telegraph pole, 
tree, wall or roof, for the support of a 
telegraphic line-insulator. 

Telegraphic Cable.— A cable designed 
to establish telegraphic communication 
between different points. 

Telegraphic Clock.— A name sometimes 
applied to a master clock. 

Telegraphic Code.— The pre-arranged 
system of signals employed in any system 
of telegraphy. 

Telegraphic Cross- Arm.— A term some- 
times employed for telegraphic arm. 

Telegraphic Dial.— A dial board contain- 
ing letters of the alphabet and figures, 
employed in dial telegraphy. 

Telegraphic Dynamo. — A dynamo em- 
ployed for generating the currents used 
in telegraphic transmission. 

Telegraphic Earth-Circuit.— That por- 
tion of a telegraphic circuit which is com- 
pleted through the earth or ground. 

Telegraphic Embosser. — An apparatus 
for recording a telegraphic message on a 
paper strip in raised or embossed char- 
acters. 



Tel J 



952 



[Tel, 



Telegraphic Fixtures.— A term gener- 
ally limited to the various supports pro- 
vided for the attachment of telegraphic 
wires. 

Telegraphic Ground-Circuit. — An earth 
circuit used in any system of telegraphy. 

Telegraphic House-Top Fixtures.— 
Telegraphic fixtures placed on the roofs 
of buildings for the support of the lines. 

Telegraphic Ink- Writer.— (1) A device 
employed for recording the dots and 
dashes of a telegraphic message in ink on 
a strip of paper. (2) A Morse inker. 

Telegraphic Insulator. — An insulator 
employed on telegraphic lines. 

Telegraphic Interrupter.— (1) A device 
for making and breaking a circuit at a 
definite rate. (2) A telegraphic key, or 
other analogous device. 

Telegraphic Interruption.— (1) Any 
fault in a line or apparatus which pre- 
vents telegraphic transmission. (2) A 
term sometimes employed in telegraphy 
for faults in general. (3) A break or 
total stoppage of signals in a submarine 
cable. 

Telegraphic Joint. — A permanent con- 
tact or junction between the ends of two 
electric conductors. 

Telegraphic Key. — The key employed 
for sending over the line the successive 
makes-and-breaks corresponding to the 
dots and dashes of the Morse alphabet, or 
to the deflections of the needle in a needle 
telegraph. 

Telegraphic Line. — A conducting circuit 
employed in any telegraphic system for 
the transmission of electric impulses or 
currents. 

Telegraphic Line-Circuit.— The conduc- 
tor or line connecting different tele- 
graphic stations. 

Telegraphic Needle.— A needle em- 
ployed in telegraphy to represent by its 
movements to the right or left, respec- 
tively, the dots and dashes of the Morse 
alphabet. 

Telegraphic Paper-Winder.— An appa- 
ratus for winding or coiling the paper 
fillet used on a telegraphic register. 

Telegraphic Photography. — A term 
sometimes used for means whereby an 
image of a photographic object may be 
telegraphically transmitted to a distant 
station. 

Telegraphic Pocket-Relay.— A form of 
telegraphic relay of such small dimen- 
sions as to permit it to be readily carried 
in the pocket. 



Telegraphic Polar -Relay. — A tele- 
graphic relay provided with a polarized 
armature. 

Telegraphic Pole. — A wooden or iron 
pole provided with suitable insulators for 
the support of an overhead telegraphic 
line or lines. 

Telegraphic Register.— (1) An apparatus 
employed at the receiving end of a tele- 
graphic line for the purpose of obtaining 
a permanent record of the telegraphic 
despatch. (2) A Morse register. 

Telegraphic Registering Apparatus. 

(1) A name sometimes given to a tele- 
graphic recorder. (2) A Morse register. 

Telegraphic Repeater.— (1) Any telegra- 
phic device whereby the relay, sounder or 
registering apparatus is caused to repeat 
into another circuit the signals received. 

(2) An apparatus for maintaining telegra- 
phic communication between two circuits 
not in conductive connection. 

Telegraphic Saddle.— A bracket of spe- 
cial shape, placed astride, on the top of 
a telegraph pole, for the support of an 
insulator. 

Telegraphic Splice.— A sheath connec- 
tion made between two cable ends, and 
overlying a joint. 

Telegraphic Stay-Rods.— Guy rods sup- 
porting telegraph poles. 

Telegraphic Stock-Printer.— A form of 
printing telegraph employed for printing 
on a strip of paper the quotations of stocks, 
received from a stock exchange. 

Telegraphic Switchboard.— (1) A device 
employed at a telegraphic station, by 
means of which any one of a number of 
telegraphic instruments in use at that 
station may be placed in or removed 
from any line connected with the station, 
or by means of which one w T ire may be 
connected to another. (2) A switchboard 
for conveniently effecting and changing 
telegraphic connections. 

Telegraphic Through-Traffic— A gen- 
eral term for the telegraphic messages 
sent directly between the terminal sta- 
tions, as distinguished from way traffic, 
which includes some intermediate sta- 
tion. 

Telegraphic Time-Service. — (1) Any 
telegraphic distribution of time. (2) The 
telegraphic distribution of time to jewel- 
lers, railroad time-keepers, or others in 
need of frequent imformation as to the 
precise time, in which electric signals 
are sent out from a standard clock, through 
relays, at two second intervals, with spe- 
cial signals at minute, five-minute, and 
hour intervals. 



Tel.] 



953 



[Tel. 



Telegraphic Transmitter.— A tablet 
having suitable contact marks placed on 
its surface, such that by moving a metal- 
lic rod over it proper signals are sent. 

Telegraphic Translator. — A term some- 
times applied to a telegraphic repeater. 

Telegraphic Way-Traffic— Telegraphic 
messages sent from one office to another, 
as distinguished from messages between 
terminal offices only. 

Telegraphic Wire. — The wires employed 
in telegraphic line circuits. 

Telegraphical. — Of or pertaining to the 
telegraph. 

Telegraphically.— In a telegraphic man- 
ner. 

Telegraphing. — Sending a communica- 
tion by means of a telegraph. 
Telegraphist. — A telegraphic operator. 

Telegraphone. — An instrument whereby 
the indentations on the cylinder of a graph- 
ophone can be reproduced upon another 
cylinder, at the same time that the vocal 
sounds represented by the indentations 
are being rendered audible. 

Telegraphy. — Any system by means of 
which a communication or despatch is 
transmitted to a distance, by means other 
than that of the unassisted voice. 

Tele - Hydro - Barometer. — An instru- 
ment for indicating and recording at a 
distance the height of water or other 
liquid in a vessel or reservoir. 

Tele-Hydro-Barometer, Electric— An 
apparatus for electrically transmitting to, 
and recording at a distant station, the 
height of water or other liquid. 

Tele-Indicator. — A term sometimes em- 
ployed for telemeter. 

Tele-Intensity of Projector. — The ap- 
parent luminous intensity of a search 
light at a distance. 

Tele-Manometer, Electric. — A gauge 
for electrically indicating and recording 
pressures at a distance. 

Tele-Meteorograph. — A form of meteor- 

. ograph, registering at a distance by the 
aid of electricity. 

Telemeter. — An apparatus for electrically 
indicating and recording at a distance 
the pressure on a gauge, the reading of a 
thermometer, or the indications of a 
similar instrument. 

Tele-Metric — Of or pertaining to a tele- 
meter. 

Telephone. — To communicate by means 
of a telephone. 



Telephone. — An instrument for the elec- 
tric transmission of articulate speech. 

Telephone Battery.— Any form of open- 
circuit battery, suitable for use in connec- 
tion with a telephone. 

Telephone Booth.— A telephone cabinet 
booth. 

Telephone Cabinet-Booth.— A silence 
telephone cabinet. 

Telephone Cable.— (1) A cable, either 
aerial or subterranean, suitable for the 
transmission of telephonic despatches. 
(2) Generally, a cable whose conductors 
are twisted in pairs, for the purpose of 
avoiding the disturbance produced by 
cross-talk. 

Telephone Call-Bell.— A bell employed 
in connection with a telephone circuit 
for calling a correspondent at the other 
end of the line to his telephone. 

Telephone Call-Wire.— (1) A wire em- 
ployed in certain telephone systems, by 
the subscriber, for the purpose of calling 
the central office. (2) A special calling 
wire in a telephone system. 

Telephone Circuit. — An electric circuit 
for the transmission of telephonic mes- 
sages. 

Telephone Cords.— (1) Flexible conduc- 
tors provided for use in connection with a 
telephone. (2) Flexible conducting cords 
provided with a telephone switchboard 
for making connections between sub- 
scribers. 

Telephone Cross-Talk.— A disturbance 
produced in a telephone circuit by induc- 
tion or leakage from a neighboring circuit. 

Telephone Drop. — An annunciator drop 
used on a telephone switchboard. 

Telephone Exchange.— A central office 
provided with circuits, switches and other 
devices, by means of which any one of a 
number of subscribers, connected either 
directly or indirectly with the exchange, 
may be placed in communication with 
any other subscriber, or with some other 
exchange. 

Telephone-Exchange Switchboard. — 
A switchboard employed in a central 
telephone exchange for the purpose of 
readily placing any subscriber in connec- 
tion with any other subscriber connected 
with that system. 

Telephone Galvanometer.— A high- 
resistance galvanometer consisting of an 
electro-magnet, provided with a soft-iron 
disc delicately mounted between its poles, 
and permanently bridged across a tele- 
phone circuit for the purpose of giving a 
visual call-signal. 



Tel.] 



954 



[Tel, 



Telephone Head-Gear. — Any apparatus 
placed on the head for readily attaching 
a telephone receiver to the ear of the 
operator. 

Telephone Indicator.— (1) An indicator 
employed on a telephone circuit to in- 
dicate the number of the correspondent 
calling. (2) A telephone drop annuncia- 
tor. 

Telephone Indicator-Coil.— A coil em- 
ployed on a telephone indicator. 

Telephone Meter.— (1) An apparatus em- 
ployed on telephone circuits for register- 
ing the number of connections between 
subscribers and the time or duration of 
the same. (2) A calculagraph. 

Telephone Relay.— An electro-magnetic 
relay employed to close an indicator cir- 
cuit or a call-bell circuit in a telephone 
system. 

Telephone Repeating-Coil.— (1) A form 
of induction coil employed for repeating 
a telephonic message. (2) An induction 
coil having two insulated windings, one 
in eacii of the two telephone circuits to 
be connected. 

Telephone Set. — A general term for the 
apparatus employed by a telephone sub- 
scriber at his office. 

Telephone Side Tone.— The tone obtained 
in a telephone receiver by talking to or 
tapping at its own transmitter. 

Telephone Subscriber.— A term applied 
to a person who is connected with a cen- 
tral telephone station. 

Telephone Subway. — A subway provided 
for the reception of telephone cables or 
wires. 

Telephone Switch.— (1) Any switch em- 
ployed in connection with a telephone. 
(2) A switch employed to place either a 
call-bell or a telephone in a telephone 
circuit. 

Telephone Test-Board.— A board pro- 
vided in a central-telephone exchange 
for the leading-in and orderly arrange- 
ment of the line wires, between the out- 
side line and the switchboard, for identi- 
fication and testing. 

Telephone Time-Check.— A clock in a 
telephone exchange by means of which 
a drop shutter is automatically released, 
at a particular trunk- wire indicator, at 
the expiration of the allotted time that a 
subscriber is given the use of the trunk 
line, and by which the central-station 
operator's attention is called to the fact 
of such expiration. (2) A telephone 
meter. 

Telephone Tinnitus.— (1) A professional 



neurosis of the auditory mechanism as- 
cribed to the constant use of the tele- 
phone. (2) A nervous auditory disorder 
attributed to constant use of the tele- 
phone. 

Telephone Transformer.— (1) An appa- 
ratus for repeating into one circuit a 
telephonic message received on another 
circuit. (2) A telephone repeating coil. 

Telephone Translator.— A telephone re- 
peater. 

Telephoner. — (1) A term sometimes ap- 
plied to a person at one end of a simple 
telephone line, in contradistinction to a 
telephone subscriber at the end of a cir- 
cuit connected with any telephone ex- 
change. (2) Any one carrying on a con- 
versation by means of a telephone. 

Telephonic. — Of or pertaining to a tele- 
phone. 

Telephonic Alarm.— (1) An alarm bell 
for calling a correspondent to his tele- 
phone. (2) A call bell. 

Telephonic Cable. — A telephone cable. 

Telephonic Cross-Connection. — Tele- 
phonic transposition. 

Telephonic Exchange. — A telephone ex- 
change. 

Telephonic Insulator. — Any insulator 
employed in connection with a telephone 
line. 

Telephonic Line. — The line wire or cir- 
cuit employed in telephonic transmission. 

Telephonic Joint. — A joint effected be- 
tween the ends of two wires in a tele- 
phone circuit. 

Telephonic Meter.— A telephone meter. 

Telephonic Receiver. — (1) The instru- 
ment employed in receiving a telephonic- 
message. (2) The instrument held to the 
ear for the purpose of receiving a tele- 
phonic message. 

Telephonically. — By means of a tele- 
phone. 

Telephonist. — Any one employing a tele- 
phone. 

Telephony. — The art of transmitting ar- 
ticulate speech by means of a telephone. 

Telephote. — (1) An apparatus for the 
telegraphic transmission of pictures by 
means of the action of light on selenium. 
(2) The pherope. 

Tele-Photography. — A system of fac- 
simile transmission by dots and dashes 
transmitted by means of a continuous cur- 
rent, whose intensity is varied by a trans* 
mitting instrument containing a selenium 
resistance. 



Tel.] 



955 



[Tern, 



Tele-Radiophone. — A form of radiophone 
arranged for the simultaneous transmis- 
sion of telegraphic and telephonic mes- 
sages. 

Telescope. — An optical instrument for 
rendering distant objects visible by en- 
larging their apparent dimensions and by- 
increasing the amount of the light emitted 
by them that reaches the eye. 

Telescopic. — Of or pertaining to the tele- 
scope. 

Telescriptor. — A name given to a particu- 
lar form of printing telegraph. 

Teleseme. — A self -registering hotel an- 
nunciator by means of which a dial 
• operated in a room indicates the charac- 
ter of the service required. 

Telestereoscope. — An optical instrument 
for causing distant objects to appear in 
relief. 

Tele-Thermograph.— (1) A registering 
tele-thermometer. (2) The record made 
by a tele-thermometer. 

Tele-Thermometer, Electric. — An elec- 
trical recording thermometer, for indicat- 
ing and recording temperature at a dis- 
tance. 

Telluric Magnetic Force. — A term some- 
times employed for the earth's magnetic 
force. 

Telluric Mines. — Explosive mines under- 
ground's distinguished from sub-aqueous, 
or sub-marine explosive mines. 

Telpher. — A general name for the appara- 
tus employed in systems of telpherage. 

Telpher Line. — The electric circuit em- 
ployed in a telpherage system. 

Telpher Locomotion. — The transporta- 
tion of merchandise by means of a telpher 
system, or telpherage. 

Telpher Locomotive. — An electric motor 
by means of which telpher cars are drawn 
on a telpher line, 

Telpherage. — A system for the convey- 
ance of carriages suspended from electric 
conductors, driven by means of electric 
motors, that take th3 current required to 
energize them diree J ly from the conduct- 
ors on which they are suspended. 

Temper.— To obtain the requisite degree 
of liar ops? and elasticity of a, metal by 
cooling while heated. 

Tempers r ire. — The thermal condition of 
a body considered with reference to its 
capability to communicate heat to other 
bodies. 

Temperature Alarm, Electric — An 
electric alarm automatically operated by 
a chr. : of temperature. 



Temperature Coefficient,— (1) A coef- 
ficient of variation in a quantity, per de- 
gree of change in temperature. (2) The 
coefficient by which a change of tempera- 
ture must be multiplied in order to arrive 
at the change in a quantity due to the 
change of temperature. 

Temperature Elevation.— (1) The excess 
of temperature of a heated body over the 
temperature of its environment. (2) The 
excess of temperature acquired by a con- 
ductor traversed by a current over the 
surrounding air. 

Temperature G-radient.— (1) A line rep- 
resenting the rate-of-change of tempera- 
ture in a body through which heat is flow- 
ing. (2) A space-rate-of-change in tem- 
perature. (3) A rate-of-change in any 
quantity varying with temperature. 

Temperature 3 legulating-Switch for 
Electric Car Heater.— A switch em- 
ployed in systems of car heating, whereby 
the separate heaters may be connected in 
series, or in parallel groups, between the 
trolley and the track, or by means of 
which one or more of the heaters may be 
removed at will. 

Tempering.— Obtaining a change in the 
hardness and elasticity of a metal by sud- 
denly cootii.g it while heated. 

Tempering, Electric— A process for 
temperi. g metals in which heat of electric 
origin i-.. employed instead of ordinary 
heat. 

Temporary. — Lasting but for a while. 
Temporary Charge by Induction.— An 

electric charge of a temporary character 
produced on a conductor by induction, as 
distinguished from a permanent charge 
so obtained. 

Temporary Currents. — Currents that 
continue but for a brief interval of time. 

Temporary Electromotive Forces.— 
Electromotive forces which continue but 
for a brief interval of time. 

Temporary Intensity of Magnetiza- 
tion. — The intensity of the magnetization 
temporarily induced in a bar of soft iron, 
as distinguished from permanent mag- 
netization induced in hard steel. 

Temporary Magnetization.— (1) A word 
employed for the magnetization produced 
in a mass of soft iron, when brought into 
a magnetic field. (2) Magnetization which 
is temporary in character. 

Temporary Magneto-Motive Forces. 

Magneto-motive forces that continue but 
for a brief interval of time. 
Temporary Socket.— A socket provided 



Ten.] 



956 



[Tes.. 



for an incandescent lamp that is not in- 
tended to be permanently installed. 

Tenacity. — (1) The stress required to pro- 
duce a rupture in a mass of given cross 
section of any material. (2) The power of 
a material to resist rupture. 

Tension. — (1) An elongating stress. (2) 
The strain produced in a substance by the 
action of a stress. (3) The pressure pro- 
duced by a confined gas against the walls 
of the containing vessel, due to molecular 
impact. 

Tension, Electric. — A term loosely ap- 
plied to signify indifferently surface den- 
sity, electromotive force, electromotive 
intensity, dielectric stress, or difference 
of potential. 

Tension-Ratchet.— A name sometimes 
given to a line-dynamometer. 

Terminal Board. — A switchboard situat- 
ed on a dynamo. 

Terminal Branch Cut-Out.— A cut-out 
for a branch taken from the end of a main 
line. 

Terminal Electromotive Force.— The 
electromotive force of a dynamo taken at 
the terminals of the machine. 

Terminal Insulator.— (1) An insulator 
at the terminus of a line. (2) A telegraph 
line insulator provided with two grooves 
for the reception of two ends which may 
be kept insulated from each other. 

Terminal Pole. — (1) The last pole of a line. 
(2) A pole of greater dimensions and more 
securely anchored than the rest, erected 
at the end of a telegraphic, telephonic, 
trolley, or power line, or where aerial wires 
join subterranean cables, and intended to 
safely resist the lateral tension of the line. 

Terminal Pressure.— The pressure at the 
terminals of any electric apparatus. 

Terminal Reflection.— A term applied 
to the reflection of electro-magnetic waves 
from the end of an open-circuited con- 
ductor. 

Terminal Telegraphic Station.— The 
telegraphic station at either terminus of 
a line. 

Terminal Voltage. — The terminal elec- 
tromotive force. 

Terminals. — A name indifferently applied 
to the poles or to the electrodes of a vol- 
taic battery. 

Terra-Cotta Conduit. — An earthenware 
conduit. 

u Terra Voltaism." — The operation of a 
telegraph system by a single voltaic ele- 
ment, consisting of a pair of dissimilar 



metals buried in the earth at opposite 
ends of the line. 

Terella. — A sphere of hardened steel, or of 
lode-stone, magnetized so that the distri- 
bution of its magnetism shall resemble 
that of the earth. 

Terrestrial Electricity.— A term pro- 
posed for atmospheric electricity. 

Terrestrial Magnetic Induction.— The 
production, of magnetism by the action of 
the earth's field. 

Terrestrial Magnetism.— A name ap- 
plied to the magnetism of the earth. 

Tesla Coil.— A form of oil-insulated in- 
duction coil or transformer. 

Tesla Discharge. — A variety of high-fre- 
quency, high-pressure discharge. 

Tesla Frequencies. — A term sometimes 
applied to frequencies which are much 
higher than those ordinarily employed. 

Tesla Transformer. — A step-up, oil-in- 
sulated transformer, employed by Tesla 
in obtaining high-frequency discharges. 

Test Board. — (1) A board employed in a 
telegraphic, telephonic, or transmission cir- 
cuits, generally, provided with the measur- 
ing instruments required for testing its 
insulation and other electrical properties. 
(2) A board in a telephone station to 
which telephone lines are connected, for 
the purpose of quickly connecting the 
testing instruments to such lines. 

Test Cell. — A voltaic cell employed for 
the busy or engaged test in a multiple 
telephone switchboard. 

Test Circuit.— In a multiple-telephone 
switchboard the circuit for the busy test. 

Test Clerk. — A clerk to whom the duties 
of testing the telephone lines are assigned. 

Test Loop. — A loop running to a test 
board. 

Test Plugs. — (1) Plugs used in testing. 
(2) Plugs for insertion in testing jacks. 

Test Ring. — (1) A call made by the central 
station to each subscriber to ascertain 
whether the line is in good operating con- 
dition. (2) A ring in front of each jack 
in a multiple telephone switchboard, and 
supplying a contact for the busy test. 

Test Room. — A testing room. 

Test Thimble. — A thimble at a central 
telephone exchange carrying a contact, 
and employed for making a busy test at a 
multiple telephone switchboard. 

Test Wire for Multiple Switchboard. 

A wire running to a multiple switchboard 
and connecting all the jacks of the same 
number in the different sections for the 



Tes,] 



957 



[The. 



purpose of enabling the operator to ascer- 
tain whether the subscriber needed is 
busy. 
Test Wire of Metallic Circuit.— (1) The 
return-wire of a metallic circuit. (2) In 
telephony, that wire in a subscriber's me- 
tallic-circuit loop which serves for the 
busy test at the switchboard. 

Test Wires. — (1) The wires in a multiple 
telephone switchboard, by which the 
busy test is made. (2) Any wires or cir- 
cuits used in making a test. (3) Wires 
to be tested or undergoing a test. 

Testing. — (I) Submitting to trial for elec- 
tric capabilities. (2) Determining the 
value of the current strength, the dif- 
ference of potential, the resistance, the 
coulombs, the farads the joules, the watts, 
etc., in any circuit. (3) Making electrical 
measurements, generally. 

Testing Bank. — A bank of lamps, or other 
inductionless resistances, employed in 
testing a circuit. 

Testing Board. — A board employed in a 
telephone switchboard for the purpose of 
testing the condition of the lines. 

Testing Car for Railway Circuits.— 
An electric trolley-car provided for mak- 
ing electric tests along a line of street 
railway while the car is in motion. 

Testing Jacks. — In a multiple telephone 
switchboard, or distributing board, special 
jacks sometimes inserted in any circuit 
for testing such circuit. 

Testing Magneto. — A magneto-electric 
machine employed to produce the high 
electromotive force required in testing 
high-resistance circuits. 

Testing of Joints. — (1) Determining the 
insulation or conductor resistance of a 
joint in any circuit. (2) Ascertaining the 
resistance of the insulating material 
around a joint in a cable. 

Testing Point of Spring Jack.— The 
tip of a spring jack. 

Testing Pole. — A term sometimes em- 
ployed in electro-therapeutics for the in- 
different pole or electrode. 

Testing Posts. — Hollow posts provided 
with a door, placed above an underground 
cable, into which the wires are sometimes 
led, employed for ease in opening and 
testing. 

Testing Rod. — An insulated conducting 
rod employed in testing insulators for 
dipping into the liquid contained in their 
sheds, when inverted in a testing bath. 

Testing Room. — (1) A room on board a 
cable-ship provided with instruments for 



cable testing and signalling. (2) A room 
fitted with tables and apparatus for mak- 
ing electrical tests. (3) In a telephone 
exchange, a room usually near the switch 
room through which all telephone lines 
pass and arranged for conveniently test- 
ing such lines. 

Testing Switch. — In a quadruplex tele- 
graphic system, a switch for throwing 
the line from the sending battery to 
ground through a suitable resistance, for 
the purpose of enabling the distant sta- 
tion to obtain a balance. 

Testing Transformer.— (1) A transformer 
employed in any system of distribution 
for the purpose of testing for grounds, for 
the condition of the line, for drop of po- 
tential, etc. (2) A transformer employed 
in testing. 

Tetanus.— Continuous spasmodic contrac- 
tion of the muscles. 

Tetrad Atom. — An atom whose valency 
or atomicity is four. 

Tetrivalent. — Possessing a valency or 
atomicity of four. 

Tetrode Working.— A term applied to a 
four-way mode of working the Delany 
synchronous multiple telegraph. 

Thaumatrope. — An optical toy depending 
on the persistence of the retinal image, 
in which two different pictures placed 
upon the opposite sides of a card are 
caused, by the rapid rotation of the card, 
to appear as a single picture. 

Theatre Dimmer.— (1) A dimmer employ- 
ed in theatres for varying the intensity of 
the illumination. (2) A rheostat or chok- 
ing coil employed in a theatre-lighting 
circuit. 

Theatre Dimming Rheostat.— A rheo- 
stat employed in connection with a theatre 
dimmer. 

Theatrophone. — A sytem of telephonic 
communication between theatres or opera- 
houses and subscribers. 

Theodolite. — An instrument employed for 
measuring angles in vertical or horizon- 
tal planes. 

Theoretical Magnet. — A hypothetical 
magnet, assumed for the purpose of 
mathematical discussion as possessing in- 
finite length and thinness, and uniform 
magnetization. 

Therapeutic Adapter. — An adapter em- 
ployed in electro-therapeutic work. 

Therapeutical Electrization.— Subject- 
ing different parts of the human body to 
the action of electric currents for the cure 
of a diseased condition. 



The.] 



958 



[The. 



Therm.— (1) A heat unit equal to the 
amount of heat required to raise the tem- 
perature of a gramme of water, at the 
temperature of its greatest density, one 
degree Centigrade. (2) The smaller 
calorie. 

Therm Calorie. — A word sometimes used 
for the smaller calorie. 

Thermsethesiometer. — An instrument 
employed in electro-therapeutics for test- 
ing the temperature sense in nervous 
diseases. 

Thermal.— Of or pertaining to heat. 

Thermal Absorption. — The absorption of 
heat energy during its passage through a 
body. 

Thermal Activity.— (1) The activity pos- 
sessed by a body, arising from its heat 
energy. (2) The rate of doing thermal 
work. (3) The rate of generating heat. 

Thermal Balance. — (1) A differential 
galvanometer employed for determining 
small differences of temperature. (2) The 
bolometer. 

Thermal Batteries. — (1) Thermo-piles. 
(2) Thermo-electric batteries. (3) An elec- 
tric source operated by heat energy. 

Thermal Cautery. — A cautery heated by 
ordinary heat, as distinguished from an 
electric cautery, or one heated by heat of 
electric origin. 

Thermal Circuit Closer. — A circuit- 
closer operated by changes of tempera- 
ture. 

Thermal Coil of Resistance Box.— A 
coil of wire inserted in a resistance box, 
and possessing a high temperature suffi- 
cient, for the purpose of indicating by its 
resistance the temperature within the 
box. 

Thermal Current.— A heat current, or 
one due to the flow or transference of 
heat through a conductor. 

Thermal Current-Strength. — The quan- 
tity of heat per second transmitted across 
any area of normal cross-section of a con- 
ductor. 

Thermal DifFusivity.— A term proposed 
for thermometric conductivity, or the 
ratio of the calorimetrical conductivity 
to the specific heat per unit volume. 

Thermal Electromotive Force of Re- 
sistance Coils. — A thermo-electric 
couple inserted in a resistance box, for 
the purpose of determining the tempera- 
ture within it. 

Thermal Equivalent of Work.— The 
equivalent, in heat units, of a given 
quantity of mechanical work. 



Thermal Incandescence.— The shining 
or glowing of a substance, generally a 
solid, by means of heat other than that of 
electric origin. 

Thermal Resistance. — The resistance 
offered by a substance to the passage of 
heat. 

Thermal Resistivity.— (1) Specific ther- 
mal resistance. (2) The specific thermal 
resistance of a substance referred to the 
thermal resistance of a unit cube between 
any pair of parallel faces. 

Thermally Effective Value.— (1) In an 
alternating-current circuit, the effective 
values from thermal measurements or 
considerations. (2) The square-root-of- 
mean-square values. 

Thermic Balance. — A bolometer. 

Thermic Interrupter.— A device operat- 
ed by the expansion of a metallic wire 
employed for the purpose of preventing 
more than a certain number of arc-lamps 
being used in a circuit where the current 
is paid for by the number of lights, rather 
than by the current supplied. 

Thermo-Barometer. — (1) A device for 
determining the elevation of a mountain 
by observing the temperature at which 
water boils on that elevation. (2) A 
hypsometer. 

Thermo-Battery. — A term sometimes ap- 
plied for a thermo-electric battery. 

Thermo-Call. — A thermo-electric call. 

Thermo-Cell. — A thermo-electric cell. 

Thermo-Chemical Cell. — An electric 
cell, in which a difference of potential is 
produced by the combined action of heat 
and chemical action. 

Thermo-Chemistry. — That branch of 
chemistry which treats of the measure- 
ment of chemical energy in thermal units. 

Thermochrosy. — (1) A word expressive 
of the fact that ordinary radiant heat, 
like light, consists of an assemblage of 
waves of different frequencies. (2) Heat 
coloration. 

Thermo-Electric Battery. — A combina- 
tion, as a single thermo-electric source, of 
a number of separate thermo-electric cells 
or couples. 

Thermo-Electric Call. — An instrument 
for electrically sounding an alarm when 
the temperature rises above or falls below 
a fixed point. 

Thermo-Electric Cell. — A name applied 
to a thermo-electric couple. 

Thermo-Electric Couple.— Any two dis- 
similar metals which, when connected at 
their ends only, so as to form a complete 



The.] 



959 



[The. 



electric circuit, will produce an electric 
current when one end is more highly 
heated than the other. 

Thermo-Eleetric Current. — A current 
produced by a thermo-electromotive 
force. 

Thermo-Eleetric Diagram. — A. diagram 
in which the thermo-electric power be- 
tween different metals is given for dif- 
ferent temperatures. 

Thermo-Eleetric Effect.— The produc- 
tion of an electromotive force at a thermo- 
electric junction by reason of the differ- 
ence of temperature between that junc- 
tion and the other junction of the couple. 

Thermo-Eleetric Electromotive Force 
of Voltaic Cell. — The thermo-electro- 
motive force produced by a voltaic couple. 

Thermo-Eleetric Element. — A name ap- 
plied to either of the metals that form a 
thermo-electric couple. 

Thermo-Eleetric Force.— (1) The force 
produced by a thermo-electric couple. 
(2) The electromotive force of a thermo- 
electric circuit. 

Thermo-Eleetric Generator. — A ther- 
mo-electric pile. 

Thermo-Eleetric Inversion. — An inver- 
sion of the thermo-electromotive force of 
a couple at certain temperatures. 

Thermo-Eleetric Junction.— A junction 
of a thermo-electric couple. 

Thermo-Eleetric Neutral Point.— A 
temperature at which two thermo-elec- 
tric forces are equal. (2) A temperature 
at which a junction of two metals has no 
thermal E. M. F. 

Thermo-Eleetric Pair. — A thermo-elec- 
tric couple. 

Thermo-Eleetric Pile.— A thermo-elec- 
tric battery. 

Thermo-Eleetric Potential-Difference. 
Difference of potential produced by a 
thermo-electric cell or pile. 

Thermo-Eleetric Power. — A number 
which, when multiplied by the difference 
of temperatures of a thermo-electric 
couple, will give the difference of poten- 
tial generated thereby. 

Thermo-Eleetric Series. — A list of 
metals, so arranged as to their thermo- 
electric powers, that each in the series is 
electro-positive to any lower in the list. 

Thermo-Electricity. — (1) The electro- 
motive forces developed by a thermo- 
electric cell or battery. (2) Electricity 
produced by differences of temperature 
at the junction of dissimilar metals. 

Thermo-Electriflcation.— E lectrifica- 



tion produced by differences of tempera- 
ture in a thermo-electric couple. 
Thermo-Electrometer. — A name some- 
times, though not happily, given to an 
electric thermometer. 

Thermo - Electromotive Force. — An 
electromotive force or difference of poten- 
tial produced by differences of tempera- 
ture at a thermo-electric junction. 

Thermo-Element. — A name sometimes 
employed for a thermo-couple. 

Thermo-G-alvanometer. — A galvanome- 
ter employed in connection with a thermo- 
pile for the purpose of showing difference 
of temperature by means of the currents 
developed. 

Thermo-Lumineseence.— Luminescence 
produced in a substance by heat at a 
temperature below that of luminosity. 

Thermolysis. — The decomposition of a 
molecule by heat. 

Thermo -Magnetic Generator. — (1) A de- 
vice for producing electricity by the com- 
bined influence of heat and magnetism. 
(2) A pyro-magnetic generator. 

Thermo-Magnetic Motor. — A pyro- 
magnetic motor. 

Thermometer, Electric. — A device for 
determining the effects of an electric dis- 
charge by the movements of a liquid 
column due to the expansion of a con- 
fined mass of air through which the dis- 
charge is passed. 

Thermometric Conductivity. — The 
ratio of the calorimetric conductivity to 
the specific heat of unit volume. 

Thermometric Heat. — A term proposed 
for heat in gross matter, as distinguished 
from radiant heat, or wave motion in the 
ether. 

Thermometric Resistance Coil. — A coil 
whose resistance is known at a given 
temperature, and employed to determine 
an unknown temperature to which it is 
exposed, from the change in its resistance. 

Thermometry. — That branch of science 
which treats of the determination of 
temperature. 

Thermo-Multiplier. — (1) A word some- 
times used for thermo-pile. (2) A form 
of low-resistance galvanometer suitable 
for use in connection with a thermo-pile. 

Thermo-Pair. — A thermo-electric couple. 

Thermophone. — (1) An electric instru- 
ment for producing sound by means of 
electricity. (2) Any instrument by means 
of which sounds are produced by the ab- 
sorption of radiant energy. 

Thermo-Pile. — A thermo-electric battery. 



The.] 



960 



[Thr. 



Thermo-Pile Galvanometer.— A form 
of galvanometer for detecting small dif- 
ferences of temperature, in which the 
thermo-pile is placed within the instru- 
ment. 

Thermoscopie Receiver.— A name some- 
times given to a microphonic receiver. 

Thermostat. — An instrument for auto- 
matically maintaining a given tempera- 
ture by closing an electric circuit through 
the expansion of a solid or liquid. 

Thermostatic Alarm, Electric. — Any 
electric alarm operated by the action of a 
thermostat. 

Thermostatic— Of or relating to a ther- 
mostat. 

Thermostatic Regulation.— Any regula- 
tion, such as in the temperature of a room, 
effected by the action of a thermostat. 

Thermostatic Regulator. — A regulator 
whose action is dependent on a ther- 
mostat. 

Thermo - Telephone.— (1) A telephone 
transmitter consisting of a continuous 
wire, one end of which is connected with a 
transmitting diaphragm placed in circuit 
with the receiving telephone battery, and 
having a current passed through it of 
sufficient strength to heat the wire. (2) A 
telephone receiver in which the dia- 
phragm is set in v ibration by thermally- 
produced changes in the length of an at- 
tached wire. 

Thermo-Tropic Battery. — A name pro- 
posed for a form of carbon battery, in 
which the E. M. F. is produced by the ac- 
tion of heat. 

Thermo-Tropic Current.— The currents 
produced by a thermo-tropic battery. 

Thief Alarm. — A term sometimes em- 
ployed for a burglar alarm. 

Third -Rail Electric Railway.— An 
electric street-car railway in which a third 
rail, insulated from the track, is employed 
for one side of the circuit, the outside 
rails, together with return feeders, being 
employed for the other side of the circuit. 

Thimble Brush. — A suitably shaped 
brush employed for cleansing such sur- 
faces as the inside of a thimble, and so 
preparing them for electro-plating. 

Thomson. — A name proposed, but not 
adopted, for a unit of electric conduc- 
tivity. 

Thomson Effect.— (1) The production of 
an electromotive force in unequally 
heated homogeneous conducting sub- 
stances. (2) The increase or decrease in 
the differences of temperature in an un- 



equally heated conductor, produced by 
the passage of an electric current through 
the conductor. 

Thomson's Bridge. — A modified form of 
Wheatstone's bridge employed for the 
measurement of very small resistances. 

Three Ammeter Method of Measure- 
ment. — A method of measuring activity 
in an alternating-current circuit by the 
combined use of three ammeters in a 
main and branch circuits respectively. 

Three-Bearing Generator.— (1) A belt- 
driven dynamo-electric generator, pro- 
vided with a third shaft bearing situated 
between the armature and the pulley. 
(2) A generator whose rotor shaft has 
three bearings. 

Three-Bearing Motor.— (1) A belt-driv- 
ing motor provided with a third shaft 
bearing between the pulley and the ar- 
mature. (2) A motor whose rotor shaft 
has three bearings. 

Three-Bearing Railway Generator.— 
A railway-generator having three bear- 
ings for its rotor shaft. 

Three-Bladed Switch.— (1) A switch 
provided with three blades. (2) A switch 
closing three circuits simultaneously. 

Three-Branched Spark. — A form of 
branched spark obtained by the discharge 
of a Leyden jar through a peculiar form 
of induction coil. 

Three - Circuit Way - Telegraphic 
Switchboard. — A form of telegraphic 
switchboard suitable for use at a way 
station. 

Three-Coil Armature Winding of Al- 
ternator. — An armature winding pro- 
viding three coils in a ring armature or 
three slots in a drum armature for each 
and every pole in the field frame. 

Three-Coil Armature Winding of 
Multiphase Alternator. — An armature 
winding providing three coils in a ring 
armature or three slots in a drum arma- 
ture, per phase, for each and every pole 
in the field frame. 

Three Corner Telegraphic Repeater. 
A telegraphic repeater which repeats from 
one circuit to two circuits. 

Three-Current Test to Instrumental 
Zero. — A localization submarine cable 
test, in which three separate measure- 
ments of resistance are made with differ- 
ent current strengths in succession, the 
Wheatstone bridge balance being taken 
to instrument zero. 

Three-Filament Incandescent Lamp 
for Triphase Circuits. — An incandes- 
cent lamp intended for use on triphase 



Thr.] 



961 



[Thr, 



circuits provided with three leading-in 
wires connected to the free ends of three 
filaments which are connected in a com- 
mon joint. 

Three-Part Commutator.— A commuta- 
tor made up of three insulated segments. 

Three-Phase Armature. — An armature 
possessing a three-phase winding. 

Three-Phase Armature-Winding.— An 
armature winding such as will enable it 
to produce three-phase currents. 

Three-Phase Bar- Winding for Arma- 
ture. — A bar winding for an armature, 
such as will enable it to produce three- 
phase currents. 

Three-Phase Circuit. — Any circuit suit- 
able for the transmission of three-phase 
currents. 

Three-Phase Coil- Winding for Arma- 
ture. — A coil winding for an armature, 
such as will enable it to produce three- 
phase currents. 

Three - Phase Continuous - Current 
Commutating Machine. — A trans- 
former from triphase alternating to con- 
tinuous currents, employing a revolving 
armature provided with a commutator. 
(2) A triphase rotary transformer. 

Three-Phase Currents. — Three alternat- 
ing-currents differing in phase from one 
another by one-third of a cycle. 

Three-Phase Dynamo. — A three-phase 
generator. 

Three-Phase Generator. — Any generator 
capable of producing three-phase cur- 
rents. 

Three-Phaser. — A three-phase generator. 

Three-Phase Meter. — A meter suitable 
for operation on a three-phase system, for 
recording the energy delivered on all 
three branches. 

Three-Phase Motor. — Any motor suitable 
for operation by three-phase currents. 

Three-Phase Rotary-Converter.— A ro- 
tary converter suitable for use in connec- 
tion with three-phase currents. 

Three - Phase Rotating - Magnetic 
Field. — A rotating field produced by the 
action of a three-phase current. 

Three-Phase System.— A system for the 
transmission of electric energy by means 
of three-phase currents. 

Three-Phase Transformer.— Three sep- 
arate transformers employed for the 
transformation of triphase currents. 

Three-Phase Transmission.— Transmis- 
sion by means of three-phase currents. 
01 



Three-Phase Two-Phase Transformer. 

An alternating-current transformer for 
transforming from three-phase currents 
to two-phase currents. 

Three-Phase Working. — Three-phase 
transmission. 

Three-Phaser. — (1) A three-phase gener- 
ator. (2) A triphaser. 

Three-Point Switch.— (1) A switch by 
means of which a circuit can be com- 
pleted through three different contact 
points. (2) A switch designed to make 
three distinct contacts. 

Three-Point Trolley Switch.— A trolley 
switch provided for a bifurcation in a 
road, or where a road divides into three 
branches. 

Three-Voltmeter Method of Measure- 
ment. — A method of measuring activity 
in an alternating-current circuit, employ- 
ing three voltmeters simultaneously. 

Three-Way Frog. — A three-way trolley 
frog. 

Three- Way Plug.— A multiple telephone 
switchboard plug making three contacts 
at sleeve, ring and tip respectively. 

Three- Way Switch. — A three-point 
switch. 

Three-Way Trolley-Frog. — A trolley 
frog used where a trolley line branches 
in three directions. 

Three- Way Trolley-Switch. — (1) A 

trolley switch designed for use at a point 
where the line branches in three direc- 
tions. (2) A trolley switch with three 
connections. 

Three- Wire Circuit. — (1) A circuit em- 
ployed in a three-wire system. (2) A 
three-wire diphase system. (3) A three- 
wire triphase system. 

Three- Wire Diphase. — A form of diphase 
circuit containing three wires, in which 
one of the wires is usually provided with 
a greater area of cross-section and is em- 
ployed as the common return. 

Three-Wire Distribution Board.— A 
distribution board in a three-wire system. 

Three-Wire Mains. — The mains employed 
in a three-wire system of distribution. 

Three-Wire Meter. — A meter suitable 
for operation on a three-wire system for 
recording the power delivered on both 
sides of the system. 

Three- Wire Moulding. — Moulding em- 
ployed in a three-wire distribution system. 

Three-Wire Multiple Switchboard. — 
A multiple telephone switchboard in 
which the jacks in a subscriber's line are 



Thr.] 



962 



[Tim 



connected in multiple, and in which three 
wires run to all jacks. 

Three-Wire Switchboard.— (1) A tele- 
phone switchboard with three wires to 
each jack. (2) A switchboard employed 
in a three-wire system of electric distri- 
bution. 

Three-Wire Switchboard.— A switch- 
board suitable for use in connection with 
a three-wire system of distribution. 

Three-Wire System. — A system of elec- 
tric distribution for lamps or other mul- 
tiple-connected translating devices, in 
which three conductors are employed in 
connection with two dynamos connected 
in series, the central or neutral conductor 
being connected to the junction of the 
dynamos, and the two other conductors to 
the remaining free terminal of each. 

Three-Wire Transmission.— (1) Trans- 
mission by the three- wire system. (2) 
Transmission by means of the three-wire 
diphase or three-wire triphase systems. 

Three- Wire Telephone Switchboard. 
A branched terminal telephone switch- 
board. 

Throttling. — Partially or completely cut- 
ting off. 

Throttling of Lines of Magnetic Force. 
Any decrease in the density of magnetic 
flux due to a magnetic joint, or to any 
decrease in the magnetic permeability of 
any portion of a circuit. (2) Saturation. 

Through. — (1) In communication with, 
telegraphically. (2) Directly connected 
telegraphically, without intermediate 
stations. (3) Completed or ended. 

Through Circuit. — A telephonic or tele- 
graphic circuit that has been completed 
through to a given station, by cutting out 
interruptions or breaks in a line, by the 
connection together of sections of dif- 
ferent wires. 

Through Line. — A line extending be- 
tween two terminal stations, as distin- 
guished from a line containing way sta- 
tions. 

Through Telephone Tablets.— Panels 
placed in a telephone switchboard for 
connecting subscribers on different 
switchboards. 

Throw. — A term sometimes employed for 
the excursion or throw of a needle. 

Throw of Needle.— A phrase sometimes 
employed for the angular deflection of a 
needle, particularly when the needle 
makes its first swing. 

Throw-Back-Indicator, Electric. — An 

annunciator with a drop that is automati- 
cally replaced. 



Throw-Over Reversing Switch.— A re- 
versing switch which is operated by 
throwing it over from one side to the 
other. 

Throw- Over Starting Switch.— A 
throw-over switch employed for starting 
an electric motor. 

Throw-Over Switch.— (1) A switch for 
readily and rapidly changing a circuit 
from one source to another or one system 
to another. (2) A switch which is 
thrown over from one set of contacts to 
another, by movement about an axis. 

Thumb-Cock Electric Burner. — An 

electric gas-burner in which the turning 
of an ordinary thumb-cock turns on the 
gas and ignites it by a spark produced by 
a wiping contact, actuated by the motion 
of the thumb-cock. 

Thunder. — The loud noise accompanying 
a disruptive lightning discharge. 

Thunder Rod. — A term formerly em- 
ployed for lightning rod. 

Thunder Storm. — A rain storm accom- 
panied by thunder and lightning. 

Ticker. — A word sometimes employed for 
stock ticker, or printing telegraph. 

Ticket Operator.— In telephony, an oper- 
ator at a central exchange whose duty it 
is to record calls on tickets for that pur- 
pose. 

Tie Bar. — A bar extending across the track 
at suitable intervals between two opposite 
rails, and employed to prevent the spread- 
ing of the rails. 

Tie Feeder. — A feeder connecting two 
stations, two feeders, or two feeding 
points. 

Tie Line. — (1) In an electric distributing 
system, a conductor free from translating 
devices and employed to equalize poten- 
tial. (2) A conductor connecting two 
points in a distributing system for the 
purpose of equalizing their potentials. 

Tie Sleeper. — A sleeper laid transversely 
to a track and serving to retain in place 
the rails which are fastened to it. 

Tie Wire. — (1) Binding wire of an insu- 
lator. (2) Wire which binds an overhead 
wire to the groove of its insulator. 

Time Annunciator. — An alarm clock. 

Time-Ball, Electric. — A ball suspended in 
a prominent position on a tall pole and 
caused to fall at the exact hour of noon, 
or at any other pre-determined time, for 
the purpose of giving a visual signal of 
correct time to an entire neighborhood. 

Time Constant. — (1) In an electric circuit 
the ratio of the inductance to the con- 



Tim.] 



903 



[Too. 



ductor resistance. (2) In an electric cir- 
cuit containing a condenser the product 
of the capacity of the condenser, and the 
resistance of its discharging circuit. 

Time-Constant of Circuit. — (1) The time 
in which a current will fall in a circuit 
when the E. M. F. is suddenly removed, in 
a ratio whose Naperian logarithm is unity. 
(2) The ratio of the inductance of a cir- 
cuit to its resistance. 

Time-Constant oi Condenser.— The time 
in which the charge of a condenser falls 
in a ratio whose Naperian logarithm is 
unity. 

Time-Constant of Electro-Magnet.— 
The time required for the current to fall, 
when the E. M. F. is suddenly withdrawn, 
to a ratio whose naperian logarithm is 
unity. 

Time Cut-Out. — An automatic cut-out ar- 
ranged so as to permit a translating de- 
vice to operate for a certain time, after 
which it is cut out of the circuit. 

Time Detector, Electric. — An electri- 
cally operated watchman's clock. An ap- 
paratus for electrically registering the 
time at which a watchman visits one or 
more stations and closes or opens a cir- 
cuit connected with the register. 

Time Fall o± Electromotive Force of 
Secondary Cell. — A gradual decrease in 
the potential difference of a secondary or 
storage cell observed during its discharge. 

Time Flow. — The ratio expressed in ergs- 
per-square-centi metre, of the amount of 
energv which is passed through a normal 
area of cross -section, to that cross-section. 

Time Gun. — A gun that is automatically 
fired by a standard clock, for the purpose 
of giving a time signal to an entire neigh- 
borhood. 

Time Hysteresis. — A term sometimes in- 
correctly employed for magnetic creep- 
ing. 

Time-Illumination. — (1) A given illumi- 
nation that is continued for a given time. 
(2) The effect produced by an illumina- 
tion continued for a time. (3) The pro- 
duct of illumination and time. 

fime-Lag of Magnetization.— (1) A lag 
which appears to exist between the time 
of the action of the magnetizing force, 
and the appearance of the magnetism. 
(2) In an alternating-current choking-eoil 
or transformer, the lag of magnetization 
due to hysteresis, expressed as a time or 
fraction of a period. 

Time Meter, Electric. — An electric meter 
whose operation is based on a record of 



time during which an electric current is 
passing. 

Time of Oscillation.— The time of vi- 
bration. 

Time of Vibration. — The time required 
for a complete to-and-fro motion of the 
particles of an elastic medium. 

Time Register. — Any device for register- 
ing a lapse of time. 

Time Register for Railroads.— A tele- 
graphic apparatus or register designed to 
record a telegraphic message transmitted 
over a line. 

Time Relay.— (1) A relay employed in a 
form of stock ticker for momentarily de- 
laj'ing the releasing of a clutch and the 
closing of a transmitter, until the print- 
ing of a given letter has been assured. 
(2) A relay employed in a system of time 
signalling. 

Time-Rise of Electromotive Force of 
Secondary Cell. — A gradual increase in 
the potential difference of a secondary or 
storage cell observed during charge. 

Time Switch. — (1) A switch arranged to 
open or close a circuit at a certain time 
or after the lapse of a certain time. 
(2) An automatic switch in which a pre- 
determined time is required either to in- 
sert a resistance into or remove it from 
a circuit. 

Time Telegraph.— A general term for the 
apparatus employed in time telegraphy. 

Time Telegraphy. — A system for the tel- 
egraphic transmission of time. 

Tinned Wire.— Wire electro-plated with 
tin. 

Tinning Metal.— The solder employed in 
joining electrotype shells or for preparing 
their backs for the reception of the back- 
ing metal. 

Toe of Grapnel.— A prong of a cable 
grapnel. 

Toll Station.— A pay telephone or tele- 
graph station. 

Toll System.— A system of charging for 
telephone communications based upon 
telephone calls, as distinguished from a 
charge based upon rental. 

Tone. — Any musical note of a definite fre- 
quency. 

Tongue of Relay.— The tip or extremity 
of the armature, carrying a contact point. 

Tooling. — The operation of shaping a 
gutta-percha covered joint by the appli- 
cation of a warm tool to its surface. 

Toothed-Core Armature. — A laminated 
armature-core whose toothed discs pro- 



Too.] 



964 



[Tou. 



vide longitudinal grooves on the surface 
of the armature for the reception of the 
armature coils. 

Toothed-Core Discs. — The discs employed 
in a toothed-core armature. 

Toothed-Drum Armature. — A drum- 
shaped form of toothed-core armature. 

Toothed-Ring Armature. — A ring- 
shaped form of toothed-core armature. 

Top-Hat Curve. — A curve of electror 
motive force, current or flux which has 
the shape of a top hat, that is, in which 
the value is fairly constant for a consid- 
erable time at its maximum rise and fall. 

Topler-Holtz Machine.— A form of elec- 
trostatic induction, or influence, machine. 

Torch Signalling. — A form of flash sig- 
nalling. 

Tore. — A toroid. 

Toroid. — A solid of revolution bounded by 
a surface generated by revolving any 
closed plane curve about an axis in its 
plane which does not cut it. 

Toroidal Coil. — (1) A coil wound in the 
form of a toroid. (2) A closed circular 
solenoid. 

Toroidal Current-Sheet. — A uniform 
current-sheet having the form of a 
toroid. 

Torpedo Boat. — A boat used for carrying 
and discharging torpedoes. 

Torpedo Cable. — (1) A cable in the circuit 
of which a torpedo fuse is placed. (2) A 
cable designed for use with a torpedo. 

Torpedo, Electric— (1) A name some- 
times given to an electric ray. (2) An 
electrically operated torpedo. 

Torpedo Nets.— Steel-wire netting sus- 
pended from or attached to a ship's side 
for the purpose of ensuring protection 
against moving torpedoes. 

Torque.— (1) The moment of a force ap- 
plied to a dynamo or other machine which 
causes its rotation. (2) The mechanical 
rotary or turning force which acts on the 
armature of a dynamo-electric machine, 
or motor, and causes it to rotate. (3) The 
ratio of the mechanical activity of a 
motor, at its belt or pulley, to the angular 
velocity. 

Torque Efficiency.— The ratio of the 
torque exerted by a motor at a given in- 
put or terminal electric activity, to the 
torque it would exert if it were a perfect 
machine and had no loss of energy. 

Torqueless Stress.— A twistless stress, or 
stress which produces no torque. 

Torricellian Vacuum. — The vacuum 
which exists above the surface of the 



mercury in a barometer tube, or other 
vessel over thirty inches in vertical 
height, which has been filled with boiled 
mercury and inverted below the surface 
of the mercury in a vessel. 

Torsibility.— Possessing the ability of be- 
ing torsed or twisted. 

Torsion.— The twisting of a body by the 
application of a torsional force. 

Torsion Galvanometer. — A galvanom- 
eter in which the strength of a deflecting 
current is measured by the torsion exerted 
on the suspension system. 

Torsional Rigidity of Fibres. — The 
elastic couple set up in a fibre per unit of 
twist. 

Torsional Vibration.— The vibration pro- 
duced in a solid body by torsion. 

Total Candle-Power.— A term some- 
times used for the total quantity of 
light emitted by any luminous source. 

Total Contact. — A full or metallic contact. 
Total-Current-Panel of Switchboard. 

That panel of a switchboard which is pro- 
vided with devices for measuring and con- 
trolling the total current generated by a 
station. 

Total Disconnection.— (1) Any discon- 
nection effected by the opening of a 
switch or the actual breaking of a circuit. 
(2) A complete loss of continuity in a cir- 
cuit. 

Total Earth. — A term sometimes used for 
dead earth. 

Total Efficiency of Luminous Source. 
The ratio of the luminous rays to the 
total energy expended. 

Total Intensity of Earth's Magnetism. 

(1) The resultant or entire force of the 
earth's magnetism, as distinguished from 
the horizontal or vertical components. 

(2) The flux density of the earth's mag- 
netism. 

Total Magnetic Induction.— (1) The 
number of lines of magnetizing force 
which pass through any space where 
magnetizable material is placed, to- 
gether with the lines added by the mag- 
netization of the magnetic material. 
(2) Total magnetic intensity, or in- 
duction density, in a magnetized sub- 
stance. 

Total Resistance.— The sum ^: \he re- 
sistances of a circuit. 

Tourmaline. — A crystalline body consist- 
ing of natural silicates arid borates of 
alumina, lime, iron, etc., possessing pyro- 
electric properties. 



Ton.] 



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[Tra. 



Tourniquet, Electric— A term some- 
times used for an electric flyer. 

Tower, Electric— A high tower, provided 
in systems of tower illumination, for the 
support of a number of electric arc-lamps. 

Tower-System of Electric Lighting.— 
The lighting of extended areas by means 
of arc lights placed on the tops of tall 
towers. 

Tower Wagon. — The repair wagon em- 
ployed on trolley lines, and provided with 
a structure for enabling the workmen to 
conveniently reach the trolley wires. 

Towing, Electric. — Electric hauling of 
canal boats. 

Towing Torpedo. — A torpedo arranged 
to be towed after a vessel, and exploded 
when it strikes the side of an enemy's 
vessel. 

Track Bond. — A rail bond. 

Track Instrument. — An electric contact 
capable of being closed by a train moving 
over it, placed by the side of a railroad 
track, and employed to sound an alarm 
or indicate at a distance the presence of 
the train. 

Track Joint. — A rail joint. 

Track Switch. — (1) A switch for leading a 
car from one track to another. (2) A 
mechanical switch in the rail of a street- 
car track for changing the route of a car. 

Track-to-Dynamo Bonding.— A method 
of bonding in which a track of positive 
polarity is bonded to the negative side of 
a dynamo. 

Traction, Electric. — The propulsion of a 
car, or other vehicle, by the action of an 
electric motor. 

Trailer. — (1) An ordinary car attached to 
a trolley car and drawn after it. (2) Any 
car hauled by a motor car. 

Trailer Grapnel. — A second or following 
grapnel attached to and travelling behind 
an ordinary grapnel. 

Trailing Pole. — (1) The following pole 
edges of a dynamo-electric machine. (2) 
The pole edges of a dynamo-electric ma- 
chine, from which a point on the surface 
of the armature moves when midway be- 
tween the poles. 

Train Describer. — (1) An electric contriv- 
ance arranged for automatically indicat- 
ing the position of trains on a railroad. 
(2) In a system of block signalling by 
electricity, an instrument for indicating 
at a distance the character of a train 
which is being sent along the line. 

Train Wire. — A line wire connected with 
the general despatcher's office, employed 



in a block system of railroads, and used 
for sending train orders only. 

Trajectory. — (1) The curve described by a 
projectile thrown obliquely upwards. (2) 
A curve which cuts, according to a given 
law, a system of curves obtained by vary- 
ing a parameter. 

Tramcar, Electric. — A term applied to 
an electric trolley car. 

Tramway, Electric — A term applied to 
an electric railway. 

Trans-Continental Telephony.— Tele- 
phonic communication established across 
a continent. 

Transfer Board. — In telephony, a switch- 
board at which calls are transferred from 
one junction line to another. 

Transfer Bus-Bar. — A bus-bar that is em- 
ployed to gradually transfer a feeder 
from one bus-bar to another, without the 
sudden variation of potential which 
would occur if it were thrown over di- 
rectly. 

Transfer Operator. — In telephony, an op- 
erator at a transfer board. 

Transform.— (1) To change or convert. 
(2) To change or convert the electromo- 
tive force, and, consequently, the current 
strength in a circuit, by any means. (3) 
To change the type of a current, as from 
an alternating into a continuous current. 

Transformation. — The act of transform- 
ing or changing. 

Transformation of Electromotive 
Force or Current. — A change in the 
value of an electromotive force or current 
by any means. 

Transformation of Electric Force.— 

(1 ) Transformation of electromotive 
force. (2) Transformation of electric en- 
ergy into some other form of energy. 

Transformation of Heat. — Transforma- 
tion of heat energy into any other form 
of energy. 

Transformer. — An induction coil em- 
ployed either for raising or for lowering 
electric pressure. 

Transformer Connection Board. — A 
board employed on a transformer for ease 
in changing or inter-connecting its cir- 
cuits. 

Transformer Controller. — (1) An appa- 
ratus for operating or controlling a trans- 
former. (2) A controller of pressure op- 
erated on the principle of an alternating- 
current transformer. 

Transformer Fuse.— A fuse employed 
either in the primary or secondary circuit 
of a transformer. 



Tra.] 



966 



[Tra. 



Transformer Fuse-Block.— A fuse-block 
in or near a transformer case. 

Transformer Guard.— (1) A transformer 
lightning-guard. (2) Any device for 
automatically grounding the secondary of 
a transformer on its accidental contact 
with the primary. 

Transformer Indicator-Diagram.— A 

set of diagrams automatically recorded on 
a card, which give the instantaneous 
values of the current and electromotive 
force of a transformer circuit. 

Transformer Lightning- Arrester .—A 
form of lightning arrester designed for 
the protection of transformers. 

Transformer Lightning Guard. — A 
transformer lightning-arrester. 

Transformer Motor. — An induction mo- 
tor. 

Transformer Secondary Connection 
Board. — A separate transformer connec- 
tion board provided for its secondary 
circuits. 

Transformer Stampings. — Sheet steel 
stampings of such shape as is suitable for 
building up the laminated core of a trans- 
former. 

Transformer Sub-Station.— A sub-sta- 
tion where a number of transformers are 
grouped, designed as a sub-centre of dis- 
tribution. 

Transforming. — (1) Changing electric en- 
ergy from lower pressure and higher cur- 
rent to higher pressure and lower current 
or vice-versa. (2) Changing the charac- 
ter of a current. 

Transforming Currents.— Changing the 
value of the current strength in any 
circuit, with a corresponding opposite 
change in pressure. 

Transforming Down. — Lowering the 
pressure in a distribution circuit by means 
of a step-down transformer. 

Transforming Station.— (1) In a system 
of distribution by transformers, a station 
other than a central station, where a num- 
ber of transformers are placed in order to 
supply a group of houses in that neighbor- 
hood. (2) A transformer sub-station. 

Transforming Up.— Raising the pressure 
in a distribution circuit, by means of a 
step-up transformer. 

Transient.— (1) Momentary. (2) Lasting 
or enduring but for a short time. 

Transient Currents.— Currents that are 
of but momentary duration. 

Transient Magnetomotive Force.— (1) 
A momentary magnetomotive force. (2) 



A magneto-motive force produced by the 
momentary passage-of an electric current. 

Trans-Illumination.— Such an illumina- 
tion of an interior cavity of the body as 
to permit it to be visible through the in- 
tervening portions of the body as a trans- 
lucent screen. 

Transition Layer. — A layer marking the 
separation of two homogeneous I todies at 
which the electric or magnetic proper- 
ties pass with great rapidity from one 
value to another. 

Transition Resistance.— (1) A term 
sometimes used in electro-therapeutics 
for a change in the value of a resistance 
caused by polarization. (2) Resistance 
residing in the contact surface between a 
solid and a liquid, or between two solids. 

Translater. — A telegraphic translator or 
repeater. 

Translating Commutator. — A term 
sometimes used for translation commu- 
tator. 

Translating Device. — A name frequently 

given to an electro-receptive device. 
Translating Telegraphic Station. — 

(1) A receiving station. (2) Any station 
at which a telegraphic message is auto- 
matically repeated into another circuit. 

Translation Commutator.— A name 
sometimes given to a switch on a trans- 
lating board. 

Translation Lag. — A lag due to the 
traverse of an active conductor past a 
magnet pole, whereby the current in the 
conductor is displaced in the direction of 
the motion, and produces a moving field, 
the iron mass or body tending to accom- 
modate itself to the direction of the flux 
in the moving field. 

Translator. — An orthography for tran- 
slater. 

Translator Keys.— Keys employed in a 
translator for signalling on either circuit. 

Translucence. — Possessing the property 
of transmitting light but of preventing* 
the outlines of objects from being seen. 

Translucent. — Possessing the property of 
translucence. 

Translucent-Disc Photometer.— A 
photometer in which the light to be meas- 
ured is placed on one side of a partly 
translucent and partly opaque disc, and 
the standard candle, or other photometric 
standard, is placed on the opposite side, 
the intensity of the light being estimated 
by the distance of the lights from the disc, 
when an equal illumination is obtained 
over both surfaces. 



Tra.] 



96^ 



[Tre. 



Transmission Circuit, Electric— The 
circuit employed to receive the apparatus 
necessary in any transfer of electric en- 
ergy from the generators to the receptive 
devices. 

Transmission Dynamometer. — A dyna- 
mometer in which the mechanical power 
that is measured is transmitted to some 
machine, as distinguished from a dyna- 
mometer which measures and at the same 
time absorbs the energy. 

Transmission, Electric. — The transfer- 
ence of energy from one pomt to another 
by means of electric currents. 

Transmission Insulator.— (1) An insu- 
lator employed on transmission lines. (2) 
A high-tension insulator. 

Transmission Line. — A transmission cir- 
cuit. 

Transmission of Energy.— The trans- 
ference of energy from one point to an- 
other. 

Transmission of Electric Energy.— The 
transference of electric energy from one 
point to another. 

Transmitted Power. — Power that is 
transferred from one point to another. 

Transmitter, Electric— (1) A general 
name applied to the various electric ap- 
paratus employed in telegraphy or tele- 
phony to transmit or send electric im- 
pulses over a line wire or conductor. 
(2) Any electric-transmitting instrument, 
as distinguished from a receiving instru- 
ment. 

Transmitting Magnet. — The magnet em- 
ployed in any transmitting instrument. 

Transmitting Station. — A station from 
which any electric signals or impulses are 
sent. 

Transposing. — In a system of telephonic 
communication, a device for avoiding the 
bad effects of mutual induction, by alter- 
nately crossing equal lengths of consecu- 
tive sections of the line. 

Transposition.— The transposing of a tele- 
graph or telephone circuit. 

Transposition Insulator.— A special 
form of insulator provided for the ready 
transposition of a telephone circuit. 

Transposition Joints of Telephone 
Circuit. — The joints employed on a tele- 
phone circuit at the transposition in- 
sulators. 

Transverse Electromotive Force.— An 
electromotive force excited by a magnetic 
field in a substance in which electric dis- 
placement is occurring. 

Transverse Vibration.— A vibration in 



an elastic medium in which the successive 
particles move at right angles to the direc- 
tion in which the wave is progressing 
through the medium. 

Travelling Derrick.— A derrick sup- 
ported on guideways, on a platform over 
which it is movable, provided for shifting 
or moving heavy masses through short 
distances. 

Travelling Dynamo.— A dynamo mount- 
ed on a movable platform. 

Travelling Motor. — (1) A motor placed 
on a movable car or carriage, as distin- 
guished from a stationary motor. (2) A 
locomotor. 

Travelling of Arc— An unsteadiness pro- 
duced in the light of a carbon arc occa- 
sioned by the shifting of the position of 
the arc between the electrodes. 

Traversing Motor, Electric— (1) A mo- 
tor which moves regularly to-and-fro, 
through a limited distance. (2) In an 
electrically operated crane, the motor 
which operates the traverse. 

Tread of Car Wheel.— The running face 
of a car wheel, or the part that comes in 
contact with the surface of the track. 

Treated Coke Filament. — A coke fila- 
ment of an incandescent lamp that has 
been subjected to the flashing process. 

Tree-System of Parallel Distribution. 
A system of parallel distribution of in- 
candescent lamps, in which the main 
conductors of the system resemble the 
trunk of a tree, and the auxiliary leads 
branch in various directions, somewhat 
after the fashion of a spreading tree, the 
lamps occupying the place of the twigs, 
leaves and fruit. 

Tree Insulator. — (1) An insulator placed 
on a tree for the support of an aerial wire. 
(2) A variety of insulator suitable for at- 
tachment to trees, and designed so as to 
keep the conductor in normal position, 
despite the movement of the tree. 

Tree Wire. — A special form of insulated 
wire designed to resist the abrasion of 
the insulating substance, when rubbed 
against a rough surface, like the bark of 
a tree. 

Trega. — A prefix for a trillion, or one mil- 
lion million, or 10 12 . 

Tregadyne. — A trillion dynes, or roughly 
the weight of a thousand tons. 

Tregerg. — One trillion ergs, or 73,730 foot- 
pounds at Greenwich ; or, approximately, 
33 foot-tons. 

Tregohm. — One trillion ohms, or one mil- 
lion megohms. 



Tre.] 



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Tregohm Galvanometer.— A galvano- 
meter which gives unit deflection through 
a resistance of one tregohm, in circuit 
with one volt. 

Trembler. — A name sometimes applied to 
a trembling bell. 

Trembler Bell. — A trembling bell. 

Trembling Bell. — A form of vibrating or 
automatic make-and-break contact bell. 

Trevelyan Effect.— A musical note 
emitted under certain circumstances 
when a mass of heated copper is supported 
on thin edges on a block of cold lead. 

Triad Atom. — An atom whose valency or 
atomicity is three. 

Triangular Triphase "Winding. —A 
word sometimes employed for the inter- 
linked or three-wire triphase. 

Triangular Triphaser.— A triangularly 
wound triphaser. 

Triero. — A prefix signifying one trillionth 
part, or 10- 12 . 

Triero- Ampere. — The one trillionth of an 
ampere. 

Tricro-Farad. — The one trillionth of a 
farad. 

Tricron. — One trillionth of a metre, or 
lO- 12 metre. 

Trier ohm. — The one trillionth of an ohm. 

Trifilar Suspension. — A suspension sup- 
ported by three parallel fibres. 

Trigonometrical. — Of or pertaining to 
trigonometry, or the science of angles, 
their relations, and properties. 

Trigonometrical Functions. — Certain 
quantities definitely related to angles 
considered as independent variables. 

Trigonometrically. — In a trigonometri- 
cal manner. 

Trigonometry.— That branch of mathe- 
matical science which treats of angles and 
their properties, in triangles or otherwise. 

Trimmer. — A name sometimes given to a 
man who recarbons electric arc-lamps. 

Trimming a Lamp. — Re-carboning an 
arc lamp. 

Trimming a Wire. — (1) Preparing a wire 
for jointing or connecting to an instru- 
ment. (2) Baring a wire of insulation 
and cleansing its conducting surface. 

Triode Working. — A three-way mode of 
telegraphic working by the Delany syn- 
chronous multiplex telegraphic system. 

Trip Indicator. — A form of indicator in 
which the indicator arm or drop is disen- 
gaged by the tripping action produced by 



the movement of the armature of an e\_Z' 
tro-magnet. 
Triphase.— A word frequently employed 
for three-phase. 

Triphase Armature. — A three-phase 
armature. 

Triphase Armature- Windings. —Three- 
phase armature windings. 

Triphase Circuit.— A three-phase circuit. 

Triphase-Current.— A three-phase cur- 
rent. 

Triphase Dynamo.— A dynamo capable 
of producing three-phase currents. 

Triphase Generator. — A triphase 
dynamo. 

Triphase Motor.— A motor capable of 
being operated by triphase currents. 

Triphase Rotary-Field.— A rotary field 
produced by the simultaneous action of 
triphase currents. 

Triphase Botary-Transformer.— A ro- 
tary transformer operated by, or produc- 
ing three-phase currents. 

Triphase Botating-Magnetic Field. — 

A triphase rotary field. 

Triphase Transformers. — (1) Three sep- 
arate transformers employed for chang- 
ing the pressure on triphase circuits. 

(2) A single transformer having three 
separate triphase windings. 

Triphase Alternating-Currents. — 

Three Uniphase alternating-currents 
whose phases are displaced with regard 
to one another by one-third of a cycle. 

Triphaser. — A triphase generator. 

Triple-Carbon Arc-Lamp. — An arc- 
lamp in which three carbon electrodes 
are used. 

Triple Connector. — A connector suitable 
for uniting the ends of three wires. 

Triple Petticoat Insulator. — An aerial 
line insulator provided with a triple pet- 
ticoat. 

Triple-Pole Single-Throw Switch. — 
A single-throw switch having three 
blades, and intended for closing three 
circuits simultaneously. 

Triple-Pole Switch. — (I) A switch consist- 
ing of a combination of three separate 
switches for opening or closing three cir* 
cuits at the same instant. (2) A switch 
employed to open or close three contacts. 

(3) A switch employed to open or clos* 
triphase circuits. 

Triple-Truck Support.— (1) A support 
for a car body, consisting of three sepa 
rate trucks. (2) A radial-tru<*L support 



TriO 



969 



[Tro, 



Triplex Telephony.— (1) The simultan- 
eous telephonic transmission of three 
distinct messages over the same wire in 
the same direction. 

Triply Re-Entrant Armature Wind- 
ing. — An armature winding provided 
with three independent conducting paths 
or windings each of which is separately 
re-entrant. 

Tripod Roof Support.— A roof-top sup- 
port for a telegraph line, in the shape of 
a tripod. 

Tripping Coil. — A coil forming part of the 
mechanism of a circuit-breaker on the 
switchboard of a central railroad station, 
so arranged that when the current has 
reached a certain predetermined value, 
limited by the action of a spring, the trip- 
ping mechanism is operated, thus break- 
ing the circuit. 

Trivalent. — Possessing an atomicity or 
valency of three. 

Trolley. — A rolling contact- wheel that 
moves over a trolley line and carries off 
the current required to drive the motor 
cars. 

Trolley Base. — A base provided for the 
support of a trolley pole, and furnished 
with springs to preserve a firm contact 
between the trolley and the trolley wire, 
and also provided with a swivel joint for 
readily reversing the direction of the 
trolley pole. 

Trolley Base-Frame. — A trolley base. 

Trolley Bus-Bar. — In a railway power 
station, the bus-bar connected with the 
trolley system, as distinguished from the 
bus-bar connected with the ground. 

Trolley Car. — A motor car in a system of 
electric railroads employing a trolley 
system. 

Trolley Car-Controller.— (1) A series- par- 
allel controller. (2) A car-control! er. 

Trolley- Contact. — The contact secured 
between a trolley and the trolley wire. 

Trolley-Cord. — The cord attached to the 
trolley pole or mast for removing it from 
and placing it on the line. 

Trolley-Crossing. — (1) An insulating de- 
vice, placed at the crossing of two trolley 
wires, by which the trolley, while run- 
ning on one line may cross the other with- 
out coming into electrical contact with it. 
(2) A. plate supported at the crossing of 
two trolley wires with guides to assist 
the trolley wheel across it. 

Trolley Crossing-Ear.— An ear employed 
at a trolley crossing. 

Trolley Cross-Over. — (1) An arrangement 



for suspending the trolley wires at a 
trolley crossing. (2) A trolley crossing. 

Trolley Ear. — A metal piece supported by 
an insulator, to which the trolley wire is 
fastened. 

Trolley Fork. — The mechanism which 
mechanically connects the trolley wheel 
to the trolley pole. 

Trolley Frog. — (1) The device to which 
the trolley wire is attached, employed for 
causing a car to deviate from one line to 
another. (2) A name given to the device 
employed in fastening or holding together 
the trolley wires at any point where the 
wires branch, and properly guiding the 
trolley along the trolley wire on the 
movement of the car over the track, 
under the action of the track switch. 

Trolley Guard.— A trolley wire guard. 

Trolley Hanger. — A device for support- 
ing and properly insulating a trolley wire. 

Trolley Harp.— The metallic frame placed 
on a trolley fork for supporting the trolley 
wheel. 

Trolley Ice-Clearer. — A form of trolley 
wheel suitable for removing ice or sleet 
from a trolley wire. 

Trolley Insulator. — A name sometimes 
applied to a trolley ear. 

Trolley Insulated Crossing.— An insu- 
lated trolley crossing. 

Trolley Mast. — A term frequently used 
for trolley pole. 

Trolley Mechanism.— (1) The device em- 
ployed for carrying the current from the 
trolley line to the motor in the car. (2) 
A general mechanism, including the 
trolley base, pole, wheel and rope. 

Trolley Pole. — A pole, or mast, of wood 
or metal supporting the trolley and em- 
ployed to carry a conductor from the car 
to the trolley wire. 

Trolley Section. — (1) A single continuous 
length of trolley wire. (2) A portion of a 
trolley line insulated from adjoining por- 
tions and furnished with separate feed 
wires. 

Trolley Railway.— An electrically oper- 
ated railroad employing a trolley. 

Trolley Stand. — (1) A word sometimes 
used for a trolley base. (2) A support 
provided for a trolley pole. 

Trolley Strain-Insulator.— An insulator 
provided for the support of the strain 
wires. 

Trolley Strain- Wires. — Wires employed 
for attachment to lugs in the anchor 
strain ear, for the purpose of maintaining 
the trolley line taut. 



Tro.] 



970 



LTru, 



Trolley Switch.— (1) A switch placed on a 
track for the purpose of changing the 
car from one track to another. (2) An 
overhead switch provided at a turn of a 
trolley road for guiding the trolley to 
another line when the frogs on the track 
beneath have thrown the wheels of the 
car into another track. 

Trolley Three-Way Frog.— A trolley 
frog used where the line branches in 
three directions. 

Trolley Traction.— Electric traction by 
the trolley system. 

Trolley Truck. — The truck supporting 
a trolley car and containing the car 
motors. 

Trolley Two-Way Frog.— The ordinary 
V-shaped trolley frog. 

Trolley Wheel.— (1) A metallic wheel 
connected with the trolley pole and moved 
over the trolley wire, for the purpose of 
taking therefrom the current required 
for driving the motor car. (2) The trolley. 

Trolley Wire. — The bare overhead wire 
employed in a trolley system for supply- 
ing the driving current to the car motors 
through the intervention of the trolley 
mechanism. 

Trolley Wire Insulator.— The insulator 
provided for the support of a trolley wire. 

Trolley Wire Splice.— A joint or splice 
employed in joining two ends of trolley 
wires, consisting essentially in slipping 
the ends in a tubular conductor and 
then brazing them. 

Trop. — A proposed unit of entropy equal 
to the quotient of one joule divided by one 
degree Centigrade. 

Truck for Car Motor.— A support pro- 
vided with wheels, and employed either 
singly, or in connection with one or more 
similar trucks, for the support of the car 
body. 

True Contact Force.— The force or effect, 
distinguished from the voltaic effect 
which exists at the points of contact be- 
tween two dissimilar metals. 

True Galvanometer Constant.— The 
intensity of the field produced at the 
centre of a galvanometer coil by a unit 
current flowing through the coil. 

True Ohm. — (1) An ideal ohm having the 
true theoretical value. (2) A term some- 
times applied to the International ohm in 
contradistinction to the B. A. or legal 
ohm. 

True Power. — In an alternating-current 
circuit the power which is represented 
by the true watts, as distinguished from 



the apparent power, or that represented by 
the apparent watts. 

True Resistance.— The resistance which 
a conductor offers to the passage of a cur- 
rent, by reason of its dimensions and 
resistivity, as distinguished from the 
spurious resistance produced by a counter 
electromotive force. 

True Watts.— The activity in an alternat- 
ing-current circuit, as given by the read- 
ing of a correctly calibrated wattmeter 
connected with such circuit. 

True Zero. — An instrument or scale zero, 
as distinguished from a false zero of a 
galvanometer. 

Trumpet, Electric. — An electro-magnetio 
buzzer "whose sound is strengthened by a 
trumpet- shaped resonator. 

Trunion Screws. — A pair of screws whose 
opposed points form the pivots of a mov- 
able shutter, armature, or other rotating 
device. 

Trunk Call.— A telephone call transmitted 
through a trunk wire. 

Trunk Connection.— A telephonic con- 
nection established through a trunk wire. 

Trunk Junction - Board. — A junction 
telephone switchboard for trunk wires. 

Trunk-Line Wires.— (1) Through wires 
extended between two distant stations, 
provided with receiving and transmitting 
instruments at their ends only. (^) In 
telephony, main line wires connecting two 
terminal offices for connection to sub- 
offices or subscribers. (3) A main line 
wire connecting two important terminals 
for receiving telephone traffic. 

Trunk-Line Working. — Telephone work- 
ing embracing the use of trunk lines be- 
tween central stations, as distinguished 
from lines connecting a central station 
with subscribers. 

Trunk Operator. — In telephony, an oper- 
ator at a trunk switchboard. 

Trunk Switchboard. — In telephony, a 
switchboard at which trunk lines termi- 
nate. 

Trunk Wire. — (1) A trunk line wire. (2) 
A main telephone wire. (8) A connect- 
ing wire running from town to towm, or 
exchange to exchange, as distinguished 
from a wire connected permanently to a 
subscriber. 

Trunk Woi king.— Telephonic or tele- 
graphic transmission by means of trunk 
line-wires. 

Trunking - Out Telephone Switch- 
board. — A form of telephone switch- 
board employed in long-distance working, 



Tru.] 



971 



[Tw 



Trunking Switchboard.— A switchboard 
in which a few subscribers only are con- 
nected to the operator, thus enabling him 
to obtain any other subscriber by means 
of trunk wires extending to other sec- 
tions. 

Trunking Telephone System. — (1) A 
system of telephony employing trunk 
wires. (2) A system of telephony in which 
multiple switchboards are dispensed with, 
and all calls are trunked from the in- 
coming to the outgoing panel. 

Trussed Pole.— A pole which has been 
strengthened against lateral pull by the 
use of an outrigger and stays. 

Trussed Standard.— A standard which 
has been strengthened to resist lateral 
stresses by the use of an outrigger and 
stays. 

Tube of Flow. — A word sometimes used 
for a tube of force. 

Tube of Force. — An imaginary tube in 
electrified or magnetized space, bounded 
by lines of electrostatic or magnetic force, 
and intersected by equipotential surfaces. 

Tube of Induction. — In a space occupied 
by magnetic induction, an imaginary tube 
of induction flux bounded by induction 
lines. 

Tube of Magnetic Force.— In magnet- 
ized space, a tube bounded by lines of 
magnetic force. 

Tubular Annunciator Drop.— A special 
form of telephone annunciator-drop in 
the shape of a tube, and provided with 
an iron-clad magnet. 

Tubular Braid.— A braid of fibrous insu- 
lating material, woven in the form of a 
tube, and provided for drawing over a 
joint after the two wires have been con- 
nected. 

Tubular Conductors.— Conductors in the 
shape of tubes. 

Tubular Connectors. — Connectors in the 
shape of tubes. 

Tubular Current.— (1) A term sometimes 
applied to the current that traverses the 
superficial portions only cf a solid con- 
ductor. (2) A current flowing through a 
tube, or having a distribution such as 
would be produced by flow through a 
tube. 

Tubular Electro-Magnet.— An electro- 
magnet of a tubular form. 

Tubular Magnet.— (1) A magnet in which 
a single coil enclosing a core is surrounded 
by an iron cylinder connected to the core 
at one end by an iron base or yoke. (2) 
A form of iron-clad magnet. 



Tumbler Switch. — A switch provided 
with a double-contact knife-blade which 
can be readily depressed by the movement 
of a bolt lever placed at the top. 

Tumbling Box.— (1) A rotating box in 
which metallic articles that are to be 
electro-plated are placed, so as to be 
polished by attrition against one another. 
(2) A rotating box in which rough cast- 
ings are placed for smoothing their sur- 
faces by attrition. 

Tuning-Fork Dynamo.— An oscillatory 
dynamo. 

Tuning-Fork Interrupter.— A reed in- 
interrupter. 

Tuning of Electric Circuit.— Altering 
the period of a circuit, or varying either 
its capacity or self-induction, so as to 
bring it in resonance with another circuit. 

Tunnel Armature. — An armature of a 
dynamo-electric machine in which the 
conductors are placed in holes, or nearly 
closed grooves, beneath the external 
surface of the core. 

Turnbuckle. — (1) An appliance for strain- 
ing span wires. (2) A screw tightener 
for a rod, guy, or line. 

Turn-Out. — (1) A short section of single 
track which allows two cars to pass one 
another on a single track line . (2) A short 
side section placed at a station on a single- 
track road for switching a car off the main 
line so as to leave it clear. 

Turn-Table , Electric— A table suitable 
for show-windows revolved around a ver- 
tical axis by means of an electric motor. 

Turret-Turning Motor.— A motor em- 
ployed on board a war-ship for turning a 
gun turret. 

Turtle-Back Electro.— A curved electro- 
type employed for use in cylindrical 
presses. 

Twigs. — (1) A term sometimes applied to 
the branches or conductors connected 
with the sub-mains in a system of incan- 
descent distribution. (2) Sub-branches, 

Twin-Carbon Arc-Lamp.— A double-car- 
bon arc-lamp. 

Twin Conductors.— Two parallel con- 
ductors, laid side-by-side, and covered by 
a simple coating of braid. 

Twin Filament Lamp.— A double-fila- 
ment lamp. 

Twin Wire. — A conductor consisting of 
two separate conductors bound together 
by an insulating covering. 

Twin- Wire Circuit.— A circuit formed 
of twin conductors. 



Twi.] 



972 



[Two. 



Twist System. — A system of running 
overhead wires for the purpose of destroy- 
ing mutual inductive disturbances, and 
consisting in giving to the wires a helical 
twist as they run. 

Twist in Armature Leads. — A displace- 
ment of the ends of the armature wires 
connected with the commutator seg- 
ments, as regards the position of the coils 
on the armature, for the purpose of ob- 
taining a more convenient position for 
the diameter of commutation, and, con- 
sequently, for the points of contact of the 
collecting brushes on the commutator. 

Twist in Leads. — A twist given at regu- 
lar intervals, to the leads of twin con- 
ductors, for the purpose of avoiding the 
effects of induction. 

Twisted Bunched-Cable.— A bunched 
cable, the separate conductors of which 
consist of twisted pairs placed in succes- 
sive layers. 

Twisted Double-Conductors.— A pair 
or a number of pairs of twisted twin con- 
ductors. 

Twisted Pair Cable. — A cable contain- 
ing one, several, or many twisted pairs of 
conductors, suitable for metallic circuits. 

Twisted Pairs of Conductors. — An 
assemblage of twisted pairs of con- 
ductors, for metallic circuits. 

Twisted Strip- Voltmeter.— A voltmeter 
consisting of a twisted strip of platinum- 
silver, and operating by the tendency of 
the strip to coil or uncoil when its tempera- 
ture is changed by the passage through 
it of the current to be measured. 

Twisted Wire-Clip. — A clip formed of a 
twisted wire. 

Twisted Wires. — A term sometimes em- 
ployed for transposed aerial telephone 
wires. 

Twisting Force. — A term sometimes used 
for torque. 

Two-Bearing Generator.— A generator 
whose rotor is provided with but two 
bearings, as distinguished from a three- 
bearing generator. 

Two-Bearing Motor. — A motor whose 
rotor is provided with but two bearings, 
as distinguished from a three-bearing 
motor. 

Two-Circuit Armature- Winding. —An 
armature winding which provides only 
two circuits through an armature be- 
tween the commutator brushes, no matter 
how great may be the number of poles. 

Two-Circuit Dynamo. — A dynamo pro- 
vided with a two-circuit armature wind- 



Two-Circuit Multiple -Winding. — A 

multiple winding on an armature, each 
component of which offers two circuits 
to the current. 

Two-Circuit Single- Wound Armature. 
A single-wound armature possessing two 
circuits independently of the number of 
poles and distinguished by the fact that 
the pitch is always forward. 

Two-Coil Armature- Win ding of Alter- 
nator. — A winding providing two slots 
in drum armatures or two coils in ring 
armature, for each and every pole in the 
field frame. 

Two-Coil Armature- Winding of Mul- 
tiphase Alternator. — A winding pro- 
viding two slots in drum armatures, or two 
coils in ring armatures, per phase, for 
each and every pole in the field frame. 

Two-Fluid Voltaic Cell.— A double-fluid 
voltaic cell. 

Two-Layer Amature- Winding.— (1) A 
winding which is essentially applied in 
two layers. (2) A winding having more 
than two layers, but which would be 
capable of application in two layers only. 

Two-Liquid Cell. — A term sometimes 
used for double-fluid cell. 

Two-Part Commutator.— A commutator 
containing two segments suitable for com- 
muting currents in a single coil rotated 
in a bipolar field. 

Two-Phase Alternator. — A diphase al- 
ternator. 

Two-Phase Armature. — A diphase arma- 
ture. 

Two-Phase Circuit. — A diphase circuit. 

Two-Phase Dynamo or Generator. — 
A diphase generator. 

Two-Phase Motor.— A diphase motor. 

Two-Phase Rotary - Transformer. — A 
diphase rotary transformer. 

Two-Phase-Three-Phase Transformer. 
An alternating-current transformer for 
transforming from two-phase currents to 
three-phase currents. 

Two-Phase Transformer. — A diphase 
transformer. 

Two-Phase Working. — Transmitting 
electric power by means of diphase cur- 
rents. 

Two-Phaser. — (1) A generator of diphase 
or quarter-phase alternating-currents. 
(2) A diphaser. 

Two-Point Switch. — A switch by means 
of which a circuit can be completed 
through two different contact points. 

Two-Point Trolley Switch.— A trolley 



Two.] 



973 



[IM>. 



switch provided for a bifurcation in a 
road. 

Two-Pole Dynamo-Electric Machine. 
A dynamo-electric machine whose field 
is produced by two poles. 

Two, Three, or Pour-Conductor Cable. 
A cable containing two, three or four 
separate conducting wires. 

Two-Way Door-Trigger. — A trigger 
which operates both when the door is 
opened and when it is closed. 

Two-Way Splice-Box. — A splice box 
provided with two tubular conduits or 
ways. 

Two- Way Switch. — A switch provided 
with two contacts connected with two 
separate and distinct circuits. 

Two- Wire Distributing Board.— A dis- 
tributing board for metallic circuits. 

Two- Wire Incandescent Lighting. — 
Incandescent lighting from a single pair 
of mains, as distinguished from three- 
wire incandescent lighting. 

Two-Wire Mains. — A name for the 
mains employed in the ordinary system 
of multiple distribution, as distinguished 



from a three-wire main, or that used in a 
three-wire system. 

Two-Wire Moulding. — A moulding pro- 
vided with two grooves, and employed for 
the reception of two- wire mains or bran- 
ches. 

Two-Wire Multiple-Switchboard.— A 
multiple telephone switchboard in which 
the jacks of a subscriber's circuit are con- 
nected by two wires. 

Two-Wire Switchboard.— A telephone 
switchboard with two-wire connections. 

Tying-In of Line Wire. — Securing aline 
wire to its insulator. 

Type-Printing Telegraphy. — Printing 
telegraphy. 

Type-Printing Telegraphic Transmit- 
ter. — A transmitter employed in printing 
telegraph}'. 

Typewriter, Electric. — A typewriting 
machine in which the keys are only in- 
tended to make the contacts of circuits 
of electro-magnets, the attractions of 
whose armatures cause the movement of 
the type levers required for the work of 
printing. 



u 



IT. — A contraction sometimes employed for 

unit. 
"Ultimate Capacity of Switchboard.— 

The total number of subscribers that a 
multiple telephone switchboard can be 
made to accommodate. 

Ultimate Optical Efficiency.— A term 
sometimes employed for the conditions 
required to ensure the greatest efficiency 
in the observation of small angular de- 
flections of a suspended mirror by prop- 
erly proportioning the dimensions of dif- 
ferent parts of the system. 

Ultra-Gaseous Matter.— (1) The peculiar 
condition of the matter which consti- 
tutes the residual atmospheres of high 
vacua. (2) Radiant matter. 

Ultra-Incandescent Lamp.— An incan- 
descent lamp in which the filament is 
covered with oxides of thorium, etc., so 
that their radiative powers are utilized 
by the glowing filament. 

Ultra-Thermal Lightning Arrester.— 
An arrester for protecting instruments 
from unduly powerful currents, operated 
by the expansion of a metallic wire placed 
in the line circuit. 



Ultra-Ultra- Violet.— A term proposed for 
luminous frequencies far beyond the vio- 
let in the spectrum. 

Ultra- Violet Rays.— A term proposed 
for rays whose frequencies are greater 
than that of violet light. 

Ultra- Violet Spectrum.— That portion 
of the spectrum which lies beyond the 
violet, or whose frequencies are greater 
than that of the violet. 

Umbrella Type of Generator.— A type 
of generator in which an umbrella-shaped 
rotor is revolved around the stator or 
stationary element. 

Umbrella Springs. — In telephone switch- 
board plugs, contact-springs pressing out 
sideways from the plug, like umbrella 
springs. 

Unbalanced Load.— In a system of elec- 
tric distribution, a load whose distribu- 
tion is unsymmetrical. 

Unbalanced Polyphase System.— A 
polyphase system in which the load and, 
therefore, the pressures and currents, are 
not symmetrically distributed. 

Unbattery .— 1) To disconnect from a bat- 
tery. (2) To remove a battery from a car, 



Unb.l 



974 



[Und, 



carriage, boat, building, device or recep- 
tacle. 
Unbuilding of Dynamo.— The loss of 
magnetization of a dynamo field. 

Undemagnetizahle.— A term applied to 
an electro-magnetic railroad signal, whose 
signals -are un reversible by atmospheric 
causes. 

Under frame. — A truck of an electric mo- 
tor car. 

Underground Cable.— A cable suitable 
for being placed underground. 

Underground-Cable Support.— (1) Any 
support provided in a subway for holding 
an underground cable. (2) A support 
provided for holding a cable where it 
passes around the side of a manhole, un- 
derground conduit, or other similar loca- 
tion. 

Underground-Cable Terminal.— (1) The 
place where an underground cable 
emerges from the ground. (2) A cross- 
connecting or distributing board placed 
where an underground cable enters or 
leaves the ground, in order to facilitate 
the making and changing of the connec- 
tions. 

Underground Conductor. — An electric 
conductor placed underground, either by 
actual burial, or by passing it through 
underground conduits or subways. 

Underground Electric Conduit.— 
(1) An underground pipe or tube provided 
with a number of separate ways or ducts 
for the reception of electric wires or 
cables. (2) An underground passage-way 
or space provided for the reception of 
electric wires or cables. 

Underground Electric Tube. — An iron 
pipe containing three insulated conduc- 
tors separated from one another and from 
the pipe by means of a bituminous insul- 
ating substance, employed in connection 
with the Edison three-wire system of dis- 
tribution. 

Underground Railway. — A name some- 
times applied to an under-running trolley 
system. 

Underground Telegraph.— (1) A tele- 
graph, a large portion of whosp circuit 
consists of underground wires or conduc- 
tors. (2) A telephone cable provided for 
use underground. 

Underground Telephone Cable.— A 

subterranean telephone cable, as distin- 
guished from an aerial telephone cable. 

Underground Trolley System.— A 
system of car propulsion in which the 
trolley wheel is replaced by a plow or 
sled that is pushed before, or drawn after, 



the car along a trolley wire placed inside 
a slotted underground conduit. 

Underground Tube.— An underground 
electric tube. 

Under-Running of Cable.— The opera- 
tion of passing a shallow-water cable over 
a boat, barge or vessel for the purposes of 
examination, by hauling the cable in at 
the bows, and allowing it to pass out at 
the same time over the stern ; or, simply 
allowing it to run over a sheave while the 
boat is urged along the line of cable. 

Under- Running of Incandescent 
Lamps. — The operation of incandescent 
lamps at a pressure below the normal. 

Under-Running Sheave.— A supported 
sheave for the admission of a bight of 
cable, and suitable for use in underrunning 
as distinguished from a sheave through 
which an end must be passed. 

Under-Running Trolley.— (1) A trolley 
wheel running under a wire in the usual 
way. (2) A word sometimes used for un- 
derground underrunning trolley. 

Under-Running Trolley.— A system of 
street-car propulsion in which the trolley 
wire is suitably supported in an under- 
ground slotted conduit, the current being 
taken off by means of a sled or shoe, 
pushed before or drawn after the car. 

Undertaker. — (1) One who supplies elec- 
tric energy to consumers. (2) A word 
sometimes used in electric lighting litera- 
ture for those who are ready to deliver 
electric energy to consumers. 

Under-Type Magnet.— A horse-shoe 
magnet of the vertical type, whose arma- 
ture is placed near the lower end. 

Undulating Current. — (1) A name some- 
times given to anundulatory current. (2) 
V current of constant direction but contin- 
uously varying strength. 

Undulation. — A wave or vibration, es- 
pecially electric. 

Undulator. — A form of rotating commu- 
tator employed for the use of transform- 
ers on continuous-current circuits. (2) A 
commutating device for the operation of 
alternating-current apparatus from a 
continuous-current circuit. 

Undulatory Currents.— Currents of con- 
stant direction whose strength gradually 
changes. 

Undulatory Discharge.— (1) A discharge 
whose strength gradually changes with- 
out change of direction. (2) A term 
sometimes used for an oscillatory dis- 
charge. 

Undulatory Winding.— A name fre- 
quently given to a wave winding. 



CJne. 



975 



[Uni. 



Unevenly Distributed Armature 
Winding. — A winding in which the 
slots do not recur at equal intervals 
around the periphery of the armature. 

Unfiashed Filament.— V lamp filament 
that has not been subjected to the flashing 
process. 

TJnfooting. — A layer of broken stone, 
gravel and concrete, placed in layers and 
rammed, and employed at the bottom of a 
foundation trench for receiving the ma- 
sonry work. 

Ungilding Bath. — A stripping bath suit- 
able for the removal of a coating of gold. 

Uni-Coil Alternating-Current Arma- 
ture-Winding. — A winding providing 
one slot or coil on the armature for each 
and every pole in the field frame. 

Uni-Coil Multiphase Armature- Wind- 
ing. — A multiphase armature winding- 
providing one slot or coil per phase for 
each and every pole in the field frame. 

Uni-Directed Currents.— (1) Currents 
that have been caused to take the same 
direction by means of a commutator. 
(2) Commuted currents. 

Uni-Directed Electromotive Forces. 

Unidirectional electromotive forces. 

Unidirectional. — Possessing the same 
direction. 

Unidirectional Discharge.— An electric 
discharge which preserves the same direc- 
tion from the beginning to the end of the 
discharge. 

Unidirectional Electromotive Forces. 
Similarly directed electromotive forces. 

Unidirectional Leak. — A gradual loss 
or leakage of electricity which takes place 
in the same direction. 

Uninlar Suspension. — Suspension by 
means of a single wire or thread. 

Uniform Density of Field.— A field in 
which the density is the same in all equal 
areas of similar cross-section, 

Uniform Flux. — Uniform magnetic-flux. 

Uniform Magnetic-Field.— (1) A field 
of uniform density. (2) A field traversed 
by the same number of lines of magnetic 
flux in all portions of area of normal 
cross-section. (3) Magnetic flux in 
straight lines and of uniform density. 

Uniform Magnetic Filament. — A term 
sometimes applied to a magnetic fila- 
ment. 

Uniform Magnetic Flux.— (1) A mag- 
netic flux whose density is everywhere 
the same. (2) The flux of a uniform 
magnetic-field. 



Uniform Magnetization.— Such a mag- 
netization of a rectangular or cylindrical 
bar that equal areas of normal cross- 
section are traversed by the same quan- 
tity of magnetic flux. 

Uniform Potential. — (1) A potential 
whose value does not vary from point to 
point. (2) A constant potential. 

Uniformly Distributed Current. — (1) A 
term sometimes employed in the sense of 
a steady current. (2) A current having 
the same density at all points in a cross- 
section of a conductor. 

Unigraph. — A portable form of sending 
and receiving Morse instrument in one 
piece. 

Uninsulated Return.— (1) A return which 
employs the earth only as a return cir- 
cuit. (2) An earth-return. 

Uni-Periodie Current. — An alternating 
current of a single frequency, as distin- 
guished from a multi-periodic current. 

Uniphase. — Single phase. 

Uniphase Alternator. — An alternator 
that produces uniphase currents. 

Uniphase Armature.— The armature of 
a uniphase alternator. 

Uniphase Armature- Winding.— Such 
an armature-winding as will produce uni- 
phase alternating-currents. 

Uniphase Circuit. — Any circuit through 
which uniphase or single-phase currents 
are passing. 

Uniphase Dynamo.— A uniphase alter- 
nator. 

Uniphase Generator. — A uniphase al- 
ternator. 

Uniphase Motor.— An electric motor 

capable of being operated by uniphase 

currents. 
Uniphaser. — A term sometimes employed 

for a uniphase alternator. 
Uniplanar. — Confined to a single plane. 
Unipolar. — Possessing a single pole. 
Unipolar Alternator. — An alternator 

provided witli a so-called single magnetic 

pole. 

Unipolar Armature. — A dynamo-electric 
machine armature whose polarity is not 
reversed during its rotation in the field of 
the machine. 

Unipolar Dynamo. — (1) A dynamo pro- 
vided with a unipolar armature. (2) A 
commutatorless, continuous-current dy- 
namo. 

Unipolar Electric Bath. — An electro- 
therapeutic bath in which the water 
forms one of the electrodes of the source. 



UnL] 



976 



[UnL 



and the other electrode is attached to a 
metal rod fixed at a convenient height 
above the body. 

Unipolar Induction. — (1) A term some- 
times applied to the induction that occurs 
when a conductor is so moved through a 
magnetic field as to continuously cut its 
lines of force. (2) The induction that 
occurs in a commutatorless, continuous- 
current dynamo. 

Unipolar Magnet. — A term proposed for 
a magnet in the shape of a long bar, one 
pole of which lies in the axis of rotation, 
the axis being placed near to the other 
pole which is balanced by a counterpoise. 

Unipolar Stimulation of Nerve.— The 
stimulation of a nerve produced by the 
application of a single electrode to that 
nerve. 

Uni-Slot Armature-Winding or Al- 
ternator. — An alternator armature- 
winding in which a single slot is provided 
for each and every pole in the armature 
frame. 

Unit Angle.— (1) A radian. (2) An angle 
equal to 57.29578° ; or, 57° 17' 44.8" nearly. 
(3) A degree, minute, second, grad, radian 
or other unit of angular measure. 

Unit Angular Velocity.— (1) A radian 
per second. (2) The velocity under which 
a particle moving in a circular path 
whose radius is equal to unity, would 
traverse unit angle in unit time. (3) Any 
angular velocity which describes a unit 
angle in unit time. 

Unit Difference or Potential of Elec- 
tromotive Force. — (1) Such a differ- 
ence of potential between two points that 
requires the expenditure of one erg of 
work to bring a unit of positive electricity 
from one of these points to the other, 
against the electric force. (2) In the 
practical system of units, the volt. 

Unit Jar. — A small Leyden jar sometimes 
employed to measure, approximately, the 
quantity of electricity passing into a Ley- 
den battery or condenser. 

Unit Magnetic-Pole. — (1).A magnetic 
pole whose strength is such that it would 
act on a similar pole at a distance of one 
centimetre with a force of a dyne. (2) 
A magnetic pole of unit strength. 

Unit of Acceleration.— That accelera- 
tion which will give to a body unit ve- 
locity in unit time, as for example, a 
centimetre-per-second per-second. 

Unit of Activity.— (1) A rate-of-doing- 
work that will perform one unit of work 
in each second. (2) In the C. G. S. sys- 



tem, an activity of one erg-per-second. 
(3) In the practical system, the watt. 

Unit of Diviance. — A term proposed for 
unit of resistance to lines of electrostatic 
force. 

Unit of Electric Quantity.— (1) A unit 
quantity of electricity. (2) The quantity 
of electricity conveyed by unit current 
per second. (3) In the practical system 
of units, the coulomb. 

Unit of Electric Supply.— (1) A unit, 
provisionally adopted in England by the 
Board of Trade, equal to a supp!y of one 
thousand amperes flowing for one hour 
under an electromotive force of one volt* 

(2) The Board of Trade unit, or kilowatt- 
hour. (3) An amount of electric energy- 
equal to 3,600,000 joules. 

Unit of Electric Work.— The joule. 

Unit of Electrostatic Capacity.— (1) 
Such a capacity of a condenser, or con- 
ductor, that an electromotive force of one 
volt will charge it with a quantity of 
electricity equal to one coulomb. (2) 
The farad. 

Unit of Force. — (1) A force which acting 
for one second on a mass of one gramme 
will give it a velocity of a centimetre-per- 
second. (2) In the C. G. S. system, the 
dyne. 

Unit of Heat.— (1) The quantity of heat 
required to raise a given weight of water 
through one degree of the thermometric 
scale. (2) The British thermal unit or 
the pound-degree-Fahrenheit ; i. e., the 
amount of heat required to raise one 
pound of w T ater one degree Fahrenheit. 

(3) The greater calorie, or the amount of 
heat required to raise the temperature of 
one thousand grammes of water one de- 
gree centigrade. (4) The smaller calorie, 
or the amount of heat required to raise 
the temperature of one gramme of water 
one degree centigrade. (5) The joule ; or 
the quantity of heat energy developed in a 
second by the passage of a current of one 
ampere through the resistance of one 
ohm. 

Unit of Illumination.— The lux. 

Unit of Inductance. — (1) A unit of 
length equal to one centimetre. (2) In 
the practical system of units, a secohm or 
quadrant. (3) The henry. 

Unit of Light. — Such a light that collect- 
ed at a single point, would produce unit 
illumination at unit distance from such 
point. 

Unit of Luminous Intensity .— The 
British candle : or the intensity of light 
emitted by a candle, of definite dimen- 



Uni.] 



977 



[Up-C. 



sions and composition, burning at the 
rate of two grains per minute. 

Unit of Magnetic-Flux. — The weber ; or, 
the amount of flux which would pass 
through a magnetic circuit whose reluc- 
tance is one oersted, under a magneto- 
motive force of one gelbert. 

Unit of Magnetic Intensity.— The gauss ; 
or, a flux density of one weber-per-square- 
centimetre of normal cross-section. 

Unit of Magnetic Reluctance.— The 
oersted; or, the reluctance which is offered 
to the passage of magnetic flux by a cubic 
centimetre of air, when measured between 
parallel faces. 

Unit of Magneto-Motive Force.— The 
gilbert ; or, the magneto-motive force 
which is required to act on a circuit in 
order to cause one weber of flux to pass 
through it against a reluctance, or mag- 
netic resistance of one oersted. 

Unit of Mass. — The quantity of matter 
in a standard gramme. 

Unit of Out-Put of Dynamo-Electric 
Machine. — (1) The unit of electric power 
furnished by the current of a dynamo- 
electric machine. (2) The kilowatt. 

Unit of Photometric Intensity.— The 
intensity of light produced by a candle of 
given dimensions and composition that 
consumes two grains per minute. 

Unit of Resistance.— (1) Such a resistance 
that unit difference of potential is re- 
quired to cause the passage of unit cur- 
rent strength through it. (2) In the 
practical system of units, the ohm. 

Unit of Self-induction.— The unit of in- 
ductance. 

Unit Quantity of Electricity.— (1) Such 
a quantity of electricity as would pass 
in one second through a circuit whose re- 
sistance is one ohm under an electromotive 
force of one volt. (2) The coulomb. 

Unit Strength of Current.— (1) Such a 
strength of current that when passed 
through a circuit one centimetre in length 
arranged in an arc of a circle one centi- 
metre in radius, will exert a force of one 
dyne on a unit magnetic pole placed at 
the centre. (2) In the practical system 
of units, the ampere. (3) In the C. G. S. 
system of units, ten amperes. 

Unit of Power. — Any unit which meas- 
ures the rate at which energy is expended, 
such as the ergper-second, the foot- 
pound-per-minute, the kilogram me- metre- 
per-minute, the horse-power, etc. 

Unit of Twist of a Fibre.— Such a twist 
that in unit of length of fibre a unit 
angular twist is produced. 
62 



Units of Work.— (1) The erg. (2) A dyne- 
centimetre, or the amount of work done 
when a force of one dyne acts through 
a distance of one centimetre. (3) A foot- 
pound, or the amount of work required to 
raise one pound vertically through the 
distance of one foot. 

Univalent. — (1) Possessing a valency or 
atomicity of one. (2) Monovalent. 

Universal Battery System. — In teleg- 
raphy or telephony, a system of employ- 
ing one battery for the supply of a plur- 
ality of circuits. 

Universal Discharger.— An apparatus 
for sending the discharge of a Leyden 
jar, or condenser, through any desired 
circuit. 

Universal Ether. — (1) The luminiferous 
ether. (2) The ether. 

Universal Switch. — A pin switchboard 
composed of horizontal and vertical me- 
tallic bars capable of inter-connection by 
means of pins. 

Unlighted Segment of Aurora. — A term 
frequently applied to the dark segment of 
an aurora. 

Unmarked End of Magnet. — A name 
formerly applied to the south-seeking pole 
of a magnet. 

Unmarked Pole of Magnet.— The south- 
seeking pole of a magnet. 

Unmarked Magnet Pole.— A name some- 
times given to the south pole of a?nagnet. 

Unplugging. — Introducing the resistance 

of a resistance box into a circuit by the 

removal of the plug keys, 
Unpolarized. — Devoid of polarization. 
Unsilvering Bath.— A stripping bath, 

suitable for the removal of a coating of 

silver. 

Unsymmetrical Polyphase Motor.— A 
polyphase motor provided with unsym- 
metrical windings. 

Untreated Filament.— The filament of an 
incandescent lamp that has not been sub- 
jected to the flashing process. 

Unvaring Current.— (1) A current whose 
strength does not vary from time to time. 
(2) A current of constant strength and 
direction. 

Up-and - Down - Working. — In teleg- 
raphy, a method of operating consisting 
of sending a message over the line from 
each end alternately, as distinguished 
from batch working. 

Up-Contact of Switch.— A contact which 
is made by the upward movement of ;i 
switch. 



Up.] 



978 



[Var. 



Up Lines. — In Great Britain, lines in the 
direction of the principal station on a 
circuit, as distinguished from the down 
lines. 

Up Side. — In telegraphy in Great Britain, 
that side nearer to the principal station of 
a circuit, as distinguished from the down 
side. 

Upper Harmonics of Current.— The 
higher frequencies of a simple-periodic or 
alternating current. 

Upright Board. — A telephone switch- 
board whose surface is vertical, as dis- 
tinguished from a flat board. 

Upright Galvanometer.— A galvano- 
meter whose needle moves in a vertical 
plane. 



Uranium Rays.— A phrase sometimes 
employed for Becquerel rays. 

Urban Telephony.— Telephonic com- 
munication between different portions of 
the same city. 

Urethral Electrode.— An electro- thera- 
peutic electrode suitable for treatment of 
the urethra. 

Useful Current.— A name proposed for 
the effective current in an alternating- 
current circuit. 

Useful Life of Incandescent Lamp. — 
The time during which an incandescent 
lamp can furnish practical and operative 
illumination. 

Utilizing Apparatus.— Any device by- 
means of which energy may be utilized. 



V. — A contraction for volt. 

V. — A contraction for volume. 

V. — A contraction sometimes used for ve- 
locity. 

v. — (1) A symbol employed for the ratio 
existing between the units of resistance 
in the electrostatic and magnetic C. G. S. 
system of units. (2) A velocity ratio. 

V. A. — A contraction sometimes used for 
voltaic alternatives. 

Vacuum. — A space from which all, or 
nearly all, traces of gas have been re- 
moved. 

Vacuum Lightning-Discharger. — A 
vacuum lightning protector. 

Vacuum Lightning - Protector. — A 
lightning protector employing a vacuum 
tube for carrying off high-pressure dis- 
charges. 

Vacuum Manometer. — Any manometer 
whose operation is independent of at- 
mospheric pressure. 

Vaccuum Pump. — An air pump. 

Vacuum -Tube Lighting. — Artificial 
illumination obtained by the passage of 
electric discharges through vacuum 
tubes. 

Vacuum Tubes. — (1) Glass tubes in 
which the air or other gas has been par- 
tially removed, and through which electric 
discharges are passed for the production 
of luminous effects. (2) A name some- 
times applied to Crookes, Roentgen, or 
other high-vacuum tubes. 

Vaginal Electrode.— An electro-thera- 



peutical electrode suitably shaped for the 
treatment of the vagina. 

Valency. — The combining value of a 
chemical atom, as regards its power of 
displacing other atoms in chemical com- 
pounds. 

Valve, Electric. — An electrically-con- 
trolled or operated valve. 

Vapor. — A gaseous substance produced by 
the action of heat, or by reduction of pres- 
sure, on a vaporizable liquid. 

Vapor Globe of Incandescent Lamp. 
A glass globe surrounding the chamber 
of an incandescent lamp, for the purpose 
of enabling it to be safely employed in an 
explosive atmosphere, or to permit it to 
be exposed in places where water is liable 
to fall on it. 

Vapor Pressure.— The pressure at which 
a liquid changes into a vapor. 

Vaporization. — The conversion of a vola- 
tile liquid into a vapor, either as in evap- 
oration at the surface of a liquid, or 
throughout its mass, as in ebullition. 

Variable Condenser.— A term sometimes 
employed for an adjustable condenser. 

Variable Inductance. — (1) The induc- 
tance of a substance whose magnetic per- 
meability is not constant. (2) An adjust- 
able inductance. 

Variable Period of Electric Circuit.— 

That period during which the current 
strength is rising or falling in a circuit, 
after the making or breaking of the same, 
until the current strength is reached or 



Tar.] 



979 



[Yen 



until the line has been completely dis- 
charged. 

Variable Period of Electric Current. 
The time which is required for an electric 
current to reach its full strength after 
the circuit is made, or for reaching zero 
strength when its circuit has been opened. 

"Variable Period of Telegraph Line.— 
The time required for the current in a 
telegraphic line to reach a constant 
strength after the circuit through it has 
been closed. 

Variable Ratio Transformer.— An alter- 
nating-current transformer whose ratio of 
transformation is subject to variation. 

Variable Resistance. —(1) A resistance, 
the value of which can be readily varied 
or changed. (2) An adjustable resist- 
ance. 

Variable State of Charge on Telegraph 
Line. — The condition of the charge on a 
telegraph wire, while the strength of the 
current is increasing up to its full 
strength in all parts, or diminishing to 
zero. 

Variation Chart or Map.— (1) A chart or 
map on which the variations of the earth's 
magnetism are marked. (2) An isogonic 
chart. 

Variation Magnetometer.— A form of 
magnetometer suitable for measuring 
changes in the earth's magnetic variation 
at any place. 

Variation of Declination. — A variation 
in the magnetic declination of the earth 
at any place. 

Variation of Earth's Magnetism.— Any 
variation in the value of the magnetic 
declination or inclination that occurs 
simultaneously over all parts of the earth. 

Variation of Magnetic Needle.— (1) The 
angular deviation of the magnetic needle 
from the true geographical north. (2) The 
declination of the magnetic needle. 

Variometer. — (1) An instrument for com- 
paring the horizontal component of the 
earth's magnetism in different localities. 
(2) The magnetic variometer. 

Varnish, Electric— A varnish formed of 
any good insulating material. 

Varley's Photometer. — A form of pho- 
tometer in which the intensity of the 
light to be measured is determined from 
the relative openings of two concentric 
circular diaphragms placed in two rotat- 
ing discs through which the standard light 
and the light to be measured respectively 
pass. 

Varley's Unit of Resistance.— The re- 
sistance of one statute mile of a special 



copper wire j^th of an inch in diameter. 
(No longer in use.) 

Varying Continuous - Current.— A di- 
rect current whose strength varies from 
time to time. 

Varying Undirectional - Current.— A 
varying continuous or direct current. 

Vector. — (1) A directed quantity. (2) A 
quantity possessing both direction and 
magnitude. 

Vector Diagram. — A diagram represent- 
ing the relations of vector quantities. 

Vector Equations. — Equations connect- 
ing vector quantities. 

Vector Formula. — A formula containing 
vector quantities. 

Vector Impedance. — The impedance of 
an alternating-current circuit considered 
as a vector or directed quantity. 

Vector Potential. — A potential possessing 
direction, as well as magnitude, derived 
by the process of summation of vectors 
or elementary directed quantities, as op- 
posed to a scalar potential, or one pos- 
sessing undirected magnitude. 

Vector Quantity. — A quantity possessing 
both direction and magnitude. 

Vector Sum. — The geometrical sum of 
two or more vector quantities. 

Vectorial Algebra.— The algebra of vec- 
tors or directed quantities. 

Vehicle, Electric. — (1) An electrically- 
propelled vehicle. (2) An automobile 
carriage. 

Velocimeter. — Any apparatus for measur- 
ing the speed of a machine, or velocity 
generally. 

Velocity. — The distance traversed by a 
body in any time. 

Velocity of Discharge.— (1) The veloc- 
ity with which a liquid or gas escapes 
from an orifice in a given time. (2) The 
time required for the passage of a dis- 
charge from a given length of conductor. 

Valocity of Transmission of Signal- 
ling. — The apparent speed of transmis- 
sion of signals over a telegraph circuit. 

Velocity Ratio.— (1) A ratio of the na- 
ture of a velocity that exists between the 
dimensions of the electrostatic and elec- 
tro-magnetic units. (2) The ratio between 
the velocities of two mutually associated 
or interconnected bodies or parts in 
a machine. 

Vena-Contracta. — A contracted vein or 
conical jet that exists in a jet of water 
escaping from a circular orifice in the 
wall of a- containing vessel. 



Ten,] 



980 



[Yir, 



Ventilated Armature- Windings.— Ar- 
mature windings provided with means 
for cooling by forcing currents of air over 
them. 

Ventilating Duct. — A ventilating space. 

Ventilating Groove.— A ventilating space 
or duct in an armature core. 

Ventilation of Armature of Dynamo 
or Motor. — The renewal of air in the 
armature chamber, due to the passage 
through it of a stream of air employed 
for the purpose of preventing too high a 
temperature elevation during operation. 

Verdet's Constant.— The magneto-optic 
constant of a transparent magnetized 
substance, expressed in angular rotation 
of the plane of polarization, for a lumin- 
ous ray of definite frequency at a definite 
temperature, between points on the ray 
path whose magnetic potential differs by 
unity. 

Veriscope. — A form of bioscope. 

Vernier. — A device for the more accurate 
measurement of smaller differences of 
length or angle than could be detected by 
the eye alone, by means of the direct read- 
ing of the position of a mark on a slid- 
ing scale. 

Vernier Caliper. — A caliper possessing a 
vernier scale provided for greater precis- 
ion in observation. 

Vernier Slides. — A pair of resistance 
slides one of which is connected in shunt 
to a pair of contacts on the other. 

Vernier Wire-Gauge. — A micrometer 
wire-gauge. 

Vertical Component of Earth's Mag- 
netism. — That component of the earth's 
directive force which acts in a vertical 
direction. 

Vertical Electrostatic Voltmeter. — 

A form of voltmeter the needle of which 
moves in a vertical instead of in a hori- 
zontal plane. 

Vertical Galvanometer.— A galvanome- 
ter whose needle is capable of motion in 
a vertical plane only. 

Vertical Intensity of Earth's Mag- 
netism. — (1) The vertical component of 
the earth's magnetism. (2) The force 
which tends to cause a magnetic needle 
to assume a vertical position. 

Vertical Magnetic Needle.— A magnetic 
needle free to move in a vertical plane 
only. 

V. Frog. — A trolley frog shaped like a 
letter V. 

Vibrating. — Periodically moving to-and- 
fro. 



Vibrating Bell. — A name sometimes 
given to a trembling bell. 

Vibrating Contact.— (1) A spring con- 
tact connected with one part of a circuit, 
and so supported as to be able to vibrate 
towards and from another part of the 
circuit, thus automatically closing and 
opening the same. (2) A form of auto- 
matic contact-breaker. 

Vibrating Electric Doublet.— A source 
of electro-magnetic waves consisting of 
two equal and opposite oscillating charges 
concentrated on two small conductors 
whose distance from each other is indefi- 
nitely small in comparison with the dis- 
tance at which the resulting wave disturb- 
ance is considered. 

Vibrating Electrotome. — An auto- 
matic circuit-breaker producing a musi- 
cal note. 

Vibration. — A complete to-and-fro move- 
ment of a vibrating body. 

Vibration Frequency.— The number of 
vibrations produced per second. 

Vibration Needle. — A tube containing 
cylindrical weights for attachment to a 
suspension for measuring the torsional 
rigidity of the same. 

Vibration Period. — The period of a single 
or whole vibration in a conductor in 
which an oscillatory vibration is being 
produced. 

Vibrator. — An electro-magnetic device 
provided on a siphon recorder for main- 
taining the siphon in continual vibra- 
tion, so that ink is thrown from it on a 
fillet of paper beneath. 

Villari Critical Point. — A term proposed 
for that strength of magnetic field at 
which the reversal of the effects of ten- 
sion occurs. 

Vine System of Space Relations.— A 
system of space relations, usually adopted 
by electrical writers, which follows the 
vine tendril ; i. e., which considers ad- 
vance in the direction of a right-handed 
rotation as positive. 

Violle. — A unit of luminous intensity pro- 
duced in a perpendicular direction by one 
square centimetre of platinum at the tem- 
perature of its solidification. 

Violle Lamp. — The violle. 

Virgin Iron. — Iron that has never been 
subjected to magnetization. 

Virtual Amperes.— (1) Amperes meas- 
ured in an alternating-current as the 
square root of the mean square of the 
current, and determined by an ammeter 



Tir.] 



981 



[Yol. 



calibrated by constant currents. (2) Ef- 
fective amperes. 

Virtual Conductance.— A term some- 
times employed for equivalent conduct- 
ance. 

Virtual Counter Electromotive Force. 
Effective C. E. M. F. in an alternating- 
current circuit. 

Virtual Current. — The virtual amperes. 

Virtual Resistance. — The apparent re- 
sistance of a circuit. 

Virtual Voltage. — Voltage measured in 
an alternating-current circuit as the 
square root of the mean square of the 
value in volts, as obtained by a voltmeter 
calibrated by continuous currents. 

Virtual Work. — In a system of bodies or 
material points, the amount of work 
which would be done by the force acting 
upon the bodies in an indefinitely small 
displacement, and which work vanishes 
when the system is in equilibrium. 

Viscous Hysteresis. — (1) The time lag 
observed in magnetizing a bar of iron 
which is neither referable to the induc- 
tion in the iron nor to self-induction in 
the magnetizing current, but to the mag- 
netic viscosity of a substance. (2) A 
sluggishness exhibited by iron for mag- 
netization or demagnetization, due to 
magnetic viscosity. 

Visual. — Of or pertaining to vision. 

Visual Angle. — An angle subtended be- 
tween two lines drawn from an eye to 
opposite extremities of an object. 

Visual Clearing-Indicator.— (1) An in- 
dicator at a telephone exchange for in- 
forming the operator that a conversation 
has ended, by the lighting up of a little 
incandescent lamp through a relay con- 
tact. (2) A clearing indicator appealing 
to the eye, as distinguished from an in- 
dicator which releases a drop. 

Visual Telegraphic Signals.— Telegra- 
phic signals that can be seen, as distin- 
guished from those which can be heard. 

Visual Telegraphy.— (1) Any system of 
telegraphy whose receiving instruments 
give visual signals. (2) Needle telegraphy. 

Vis- Viva. — (1 ) The energy stored in a mov- 
ing body. (2) The measure of the amount 
of work that must be performed in order 
to bring a moving body to rest. 

Vitreous. — Of or pertaining to glass. 

Vitreous Electricity. — A term formerly 
employed for positive electricity. 

Vitreous Electrification. — A term for- 
merly employed for positive electrifica- 
tion/ 



Vi trite. — A variety of insulating sub- 
stance. 

Volatilization, Electric. — (1) A term 
sometimes used instead of electric evap- 
oration. (2) The volatilization of a con- 
ductor under the influence of heat of 
electric origin. 

Volatilization of Electric Conductor.— 
The deflagration of an electric conductor 
by electrically generated heat. 

Volcanic Lightning.— The lightning dis- 
charges that attend most volcanic erup- 
tions. 

Volt. — (1) The practical unit of electro- 
motive force. (2) Such an electromotive 
force as is induced in a conductor which 
cuts lines of magnetic flux at the rate of 
100,000,000 per second. (3) Such an elec- 
tromotive force as would cause a current 
of one ampere to flow against a resistance 
of one ohm. (4) Such an electromotive 
force as would charge a condenser of the 
capacity of one farad with a quantity of 
electricity equal to one coulomb. (5) 
10 8 absolute electro-magnetic units of elec- 
tromotive force. 

Volt-Ammeter. — (1) A name sometimes 
given to any instrument capable of meas- 
uring either the volts or the amperes in a 
circuit, or both. (2) The measurer of the 
volt-amperes or watts. (3) A wattmeter. 

Volt- Ampere.— The watt. 

Volt Box. — The name sometimes given to 
a divided wire placed across the terminals 
of a voltmeter to be tested. (2) A name 
sometimes given to a resistance divided 
into such sections that any suitable frac- 
tional drop in potential in the entire re- 
sistance can be readily measured by a po- 
tentiometer. 

Volt Indicator. — A name sometimes given 
to a voltmeter. 

Voltage. — The value of the electromotive 
force or difference of potential of any part 
of a circuit, expressed in volts. 

Volta-Electric. — Of or pertaining to volta- 
electricity. 

Volta-Electric Induction. — A term 
sometimes used for voltaic induction. 

Volta-Electricity. — A word sometimes 
used for voltaic electricity. 

Volta-Electrometer.— A word sometimes 
used for voltameter. 

Volta -Electrometfic— Of or pertaining 
to a voltameter or to voltaic electricity. 

Volta-Electromotive Force. — Voltaic 
electromotive force. 

Volta-Force. — Contact force between dif- 
ferent metals. 



Vol.] 



982 



[Vol. 



Volta-Plast. — An unnecessary word pro- 
posed for a voltaic battery, used in electro- 
plating. 

Volta-Type. — An unnecessary word pro- 
posed for electro-type. 

Volta's Law. — The difference of potential 
between any two metals is equal to the 
sum of the difference of potential between 
the intervening substances in the contact 
series. 

Voltagraphy. — An unnecessary word 
sometimes used for electro-typing. 

Voltaic Accumulator. — A term some- 
times used for a secondary cell. 

Voltaic Alternatives.— (1) A term used 
in medical electricity for the sudden re- 
versals in the polarity of the electrodes of 
a voltaic battery employed in electro- 
therapeutics. (2) An alternating current 
obtained from a voltaic battery by the use 
of a suitable commutator. 

Voltaic Arc— (1) A brilliant arc or bow of 
light which appears between the elec- 
trodes or terminals of a sufficiently power- 
ful source of electricity, when placed in 
contact and then separated a short dis- 
tance from each other. (2) The source of 
light of the electric arc-lamp. 

Voltaic Balance.— An apparatus employed 
' to measure the voltaic energy present in 
any aqueous solution by balancing the 
electromotive forces produced by two 
small zinc-platinum couples immersed in 
water and placed in series with the circuit 
of a sensitive galvanometer, so as to bal- 
ance one another, and then applying a solu- 
tion of the substance whose energy is to be 
measured to the liquid in one of the solu- 
tions. 

Voltaic Battery. — The combination as a 
single source of a number of separate vol- 
taic cells. 

Voltaic Battery Indicator. — A device for 
indicating the condition of a voltaic bat- 
tery. 

Voltaic Battery Protector.— A device 
for automatically opening the circuit of a 
voltaic battery, whenever itr becomes 
accidentally grounded. 

Voltaic Bow. — A word sometimes used 
for a voltaic arc. 

Voltaic Capacity of Accumulator.— A 
term sometimes applied to the storage 
capacity of an accumulator. 

Voltaic Cell. — (1) The combination of two 
metals, or of a metal and a metalloid, 
which ,when dipped into a liquid or liquids 
called electrolytes, and connected by a 
conductor, will produce a current of elec- 



tricity. (2) A voltaic couple and it* 
accompanying electrolytes. 

Voltaic Circle.— A name formerly em- 
ployed for voltaic cell or circuit. 

Voltaic Circuit. — The path through which 
the current flows from a voltaic cell or 
battery through the translating devices 
and back again through the cell or 
battery. 

Voltaic Couple. — Any two materials, gen- 
erally dissimilar metals, which are capa- 
ble of- acting as an electric source when 
dipped into an electrolyte. 

Voltaic Coupler. — Any device by means 
of which voltaic cells may be readily 
coupled or connected in different varieties 
of circuits. 

Voltaic Effect.— The difference of poten- 
tial observed at the point of contact of 
dissimilar metals. 

Voltaic Electricity.— The difference of 
potential produced by a voltaic cell or 
battery. 

Voltaic Electromotive Force.— A term 
sometimes used for the electromotive* 
force generated at the electrodes of an 
electrolytic cell in contradistinction to- 
the counter-electromotive force produced 
at such electrodes before polarization. 

Voltaic Elements.— Two metals or sub- 
stances which form a voltaic couple. 

Voltaic Endosmose.— A term sometimes 
used for electric osmose or endosmose. 

Voltaic Force. — A word sometimes used 
for voltaic electromotive force. 

Voltaic Heat Cell.— A cell by means of 
which heat energy is changed or converted 
into electric energy. 

Voltaic Impulse. — A word sometime^ 
used for the electromotive impulse of a 
voltaic couple. 

Voltaic Induction. — A word sometimes 
used for current induction. 

Voltaic Magnet. — An unnecessary term 
sometimes employed for a solenoid or 
electro-magnetic helix. 

Voltaic Pair. — A voltaic couple. 

Voltaic Pile. — A word sometimes used 
for voltaic battery. 

Voltaism. — (1) A word sometimes em- 
ployed in electro-therapeutics for treat- 
ment by means of the voltaic current. 
(2) The production of electricity by means 
of voltaic couples. 

Voltameter.— An electrolytic cell em- 
ployed for measuring the quantity of 
electric current passing through it, by 
the amount of chemical decomposition 
affected in a given time. 



Tol.] 



983 



[Wal. 



Voltameter Law.— The amount of chemi- 
cal action produced by electrolysis in any 
electrolyte is proportional to the quantity 
of electricity which passes through that 
electrolyte. 

Volta's Condensing Electroscope.— An 
electroscope whose leaves are charged by 
means of a condenser, employed for the 
detection of feeble charges. 

Voltmeter. — Any instrument employed 
for measuring differences of potential. 

Voltmeter Panel of Switchboard.— The 
panel of a switchboard containing a volt- 
meter or voltmeters. 

Voltmeter Switch. — A switch for readily 
and safely connecting a voltmeter with 
any one of a number of circuits whose 
pressures may have to be measured. 

Volume Density, Electric— The amount 
of electricity per unit of volume. 

Volume Density of Charge.— The elec- 
tric volume-density. 

Volume of Illumination. — A term pro- 
posed for a total quantity of illumination 
comprised between a surface on a hori- 
zontal plane, and the locus of the extremi- 
ties of ordinates drawn vertically to each 
part of that surface, in values represent- 
ing the intensity of illumination at that 
point. 

Volume Specific Resistance.— (1) The 
electric resistance of a cubic centimetre of 
material measured between opposite faces 
of the cube, and expressed in the C. G. S. 
absolute system of units. (2) Volume re- 
sistivity. (3) Specific resistance by vol- 
ume as compared with the volume resist- 
ance of a standard substance. 

Volume Voltameter.— A voltameter in 



which the quantity of current passing is 
determined by the volume of gas evolved. 

Volumetric Energy.— (1) Energy per 
unit of volume. (2) The energy in any 
substance or space divided by the volume 
of the substance or space. 

Vortex Atom. — A hypothetical vortex in 
the ether constituting an atom of a ma- 
terial substance. 

Vortex Cylinder. — A cylindrically shaped 
vortex ring. 

Vortex Ether. — An ether possessing in- 
ertia and capable of forming vortices like 
a Motionless liquid. 

Vortex Ring.— (1) A ring of vortically 
moving matter. (2) A name sometimes 
given to a motion in the air or other gross 
matter, similar to that which is supposed 
to constitute a vortex atom. 

Vortex-Ring Field.— The field of influ- 
ence possessed by -a vortex ring. 

Vortex Stream Lines. — Stream lines in 
the ether or matter, constituting a vortex 
atom or ring. 

Vulca. — A variety of insulating material. 

Vulcabeston. — A variety of insulating 
substance composed of asbestos and rub- 
ber. 

Vulcanite. — (1) A variety of vulcanized 
rubber, possessing high powers of insula- 
tion and specific inductive capacity. (2) 
Ebonite. 

Vulcanized Fibre. — A variety of insulat- 
ing material suitable for purposes requir- 
ing the highest insulation. 

Vulcanizing Wooden Poles.— Subject- 
ing poles to the action of heat while in a 
closed cylinder. 



w 



W. — A contraction for watt. 

W. — A contraction for work. 

W. — A contraction for weight. 

W. — A contraction for physical energy, 
whether electrical, thermal, mechanical 
or chemical ; or, in general, for the pro- 
duct of the force acting, and the distance 
through which it acts. 

W. — A symbol for electric energy. 

W. — A symbol proposed for moment of a 
couple. 

W. H. E. — A contraction for watt-hour 

efficiency. 
"W. P. — A contraction for waterproof. 



w. h. — An abbreviation for watt-hour, a 
practical unit of electric energy. 

Wall Box for Flush Switch.— A box 
sunk in a wall for the reception of a flush 
switch. 

Wall Bracket.— (1) An insulator bracket 
attached to a wall. (2) A more or less 
ornamental support for one or more in- 
candescent lamps attached to the wall of 
a room, hall, or corridor. 

Wall Frame for Flush Switch.— A term 
sometimes used for the wall box of a flush 
switch. 

Wall Plug. — A plug provided for the in- 
sertion of a lamp or other electro-recep- 



Wal.] 



984 



[Wat. 



tive device in a wall socket, thus connect- 
ing it with the lead. 

Wall Set. — Telephone apparatus arranged 
for use when supported on or against a 
wall. 

Wall Socket. — A socket placed in a wall 
and provided with openings for the inser- 
tion of a wall plug with which the ends 
of a flexible twin-lead are connected. 

Wand, Electric. — A term sometimes used 
for an electrophorus in the form of a torch. 

Wandering of Electric Spark. — A dis- 
charge possessing the appearance of a 
brilliant luminous globule, which moves 
slowly, in an irregular path, over the sur- 
face of the tin-foil on a condenser to 
which the terminals of a powerful rheo- 
static machine is placed, when a portion 
of the mica plate in the condenser is ac- 
cidentally pierced. 

Wanted Station. — A word sometimes em- 
ployed for a station that is desired by a 
telephone subscriber. 

Ward. — A term proposed for a line and 
direction in a line. 

Waring Anti-Induction Cable. — A 
form of lead-covered anti-induction cable. 

Washer Plate.— A buried metallic plate 
for supporting the tension of a stay-rod. 

Waste Magnetic Field.— A term fre- 
quently employed for stray field. 

Watch-Case Telephone Receiver. — A 

name sometimes given to a small tele- 
phone receiver in the shape of a watch- 
case. 

Watchman's Electric Clock.— A name 
sometimes given to a watchman's electric 
register. 

Watchman's Electric Register.— A 
clock device for permanently recording 
the time of a watchman's visit to each of 
the different localities he is required to 
visit at stated intervals. 

Water Battery.— A battery formed of 
zinc-copper couples immersed in an elec- 
trolyte of ordinary water. 

Water-Cooled Transformer.— A trans- 
former that is cooled by the forced circu- 
lation of water through it. 

Water-Dropping Accumulator.— A de- 
vice for increasing the difference of po- 
tential between two electric charges, by 
the dropping of water through electrified 
funnels. 

Water-Dropping Collector. — A term 
sometimes employed for a water-drop- 
ping accumulator. 

Water-Gramme-Degree Centigrade.— 
(1) A heat unit equal to the quantity of 



heat required to raise a gramme of water 
one degree Centigrade. (2) The small 
calorie. 
Water Horse-Power. — A term employed 
by the Indian Government for a horse- 
power developed by falling water, and 
estimated as being equal to 15 cubic feet 
of w T ater falling per second, through a dis- 
tance of one foot. 

Water Telephone Transmitter. — A 

telephone transmitter consisting of a jet 
of water issuing vertically downwards 
from a small orifice. 

Water-Leyel Alarm, Electric— (1) A 
device for electrically sounding an alarm 
when a water level varies materially from 
a given level. (2) A liquid-level alarm. 

Water-Pipe Resistance. — The resistance 
which any pipe offers to the flow of water 
through it. 

Water-Proof Wire.— Wire covered by a 
water-proof material. 

Water Pyrometer. — A pyrometer em- 
ployed for determining the temperature 
of a furnace, or other intense source of 
heat, by the increase in temperature of a 
known weight of water, into which a 
metal cylinder of a given weight has 
been put, after having been exposed for a 
given time to the source of heat to be 
measured. 

Water Rheostat.— A rheostat whose resist- 
ance is obtained by means of a mass of 
water of fixed dimensions. 

Water-Tube Dead-Beat Suspension. — 
A dead-beat suspension obtained for the 
mirror of a sensitive galvanometer by the 
resistance offered by water in a tube to 
the movement of a vane attached to the 
suspension axis. 

Water Voltaic Cell.— A cell consisting 
of a couple immersed in ordinary water. 

Water Voltameter.— A name sometimes 
given to a dilute sulphuric acid volta- 
meter. 

Watt. — (1) A unit of electric power. (2) A 
volt-ampere. (3) The power developed 
when 44.25 foot pounds of work are done 
in a minute, or 0.7375 foot-pound of work 
is done in a second. 

Watt Arc— A voltaic arc, the electrio 
power of which is estimated in watts. 

Watt Balance. — A form of electric balance 
suitable for measuring in watts the elec- 
tric energy developed in any circuit. 

Watt Generator. — A term sometimes em- 
ployed for the power in watts that any 
electric source is capable of producing. 

Watt-Hour. — (1) A unit of electric work. 



Wat.] 



985 



[Wea. 



(2) A term employed to indicate the ex- 
penditure of an electric power of one 
watt for an hour. 

Watt-Hour Efficiency of Storage Bat- 
tery. — The ratio between the amount of 
electric work in watt-hours a battery 
will yield after being charged, and the 
amount of work in watt-hours expended 
in charging it. 

Watt-Hour Meter. — A form of recording 
watt-meter. 

Wattless Component. — A component 
of E. M. F. or current, in quadrature with 
the working component. 

Wattless Component of Current.— (1) 
In an alternating-current circuit that 
component of the current which is in 
quadrature with the impressed E. M. F. 
and which, therefore, takes from or gives 
no energy to the circuit. (2) In an alter- 
nating-current circuit the product of the 

E. M. F. and the effective susceptance. 

Wattless Component of Electromo- 
tive Force. — (1) In an alternating-cur- 
rent circuit, that component of the E. M. 

F. which is in quadrature with the cur- 
rent strength, and, therefore, does no 
work on the current. (2) In an alternat- 
ing-current circuit the product of the 
current and the effective reactance. 

Wattless Current. — (1) That component 
of an alternating electric current which is 
in quadrature with the pressure and 
which, therefore, does no work. (2) The 
idle current. (3) In an alternating-cur- 
rent circuit the product of the effective 
susceptance and the E. M. F. 

Wattless E. M.F.— (1) The wattless com- 
ponent of E. M. F. in an alternating-cur- 
rent circuit. (2) The reactive E. M. F., 
as distinguished from the active E. M. F. 
of an alternating-current circuit. (3) In 
an alternating-current circuit, the pro- 
duct of the E. M. F. and the effective or 
apparent conductance. 

Wattless Magnetizing Current. — (1) A 
component of the magnetizing current 
which consumes no power on the average. 
(2) That component of the current which 
flows through the primary of a trans- 
former, which serves for magnetizing 
only, and which is in quadrature witli the 
pressure, as distinguished from the com- 
ponent of magnetizing current which 
expends energy in the iron core. 

Wattmeter. — An instrument for measur- 
ing the power in any circuit. 

Watt-Minute. — (1) A unit of electric 
work. (2) An expenditure of electric 
power of one watt for one minute. 



Watt-Second.— (1) A unit of electric work. 
(2) An expenditure of electric power of 
one watt for one second. (3) A joule. 

Wave. — An oscillatory motion in an elastic 
medium, periodic in time. 

Wave Bisector. — An electric chronograph 
for determining the current or potential 
in a telegraph circuit or line at any given 
small interval of time after the applica- 
tion of the sending current. 

Wave, Electric. — An electric periodic dis- 
turbance in an elastic medium. 

Wave Form of Alternating Current. — 
Any particular type of an alternating- 
current wave. 

Wave Form of Alternating Current. 
A graphical type of an alternating-cur- 
rent wave. 

Wave Winding. — (1) Undulatory wind- 
ing. (2) Continuous winding. (3) A wind- 
ing which, when developed, has the form 
of a wave. 

Waves of Condensation and Rarefac- 
tion. — (1) The alternate spheres of con- 
densed and rarified air by means of which 
sound is propagated. (2) Sound waves. 

Way. — A term sometimes employed for 
cable w r ay. 

Way Lease. — A permit obtained from the 
owner of a property for the erection of 
poles or other attachments for telephonic 
or telegraphic lines. 

Way Leave. — A word sometimes used for 
way lease. 

Way Leave.— (1) A right of way. (2) 
An easement. 

Way Line. — A line communicating with 
way stations. 

Way Office Cut-Out.— A cut-out em- 
ployed for inserting or removing a way 
office in a telegraphic line, by the aid of 
a plug. 

Way Telegraphic Station. — Any station 
intermediate between the terminal sta- 
tions. 

Ways for Dynamo-Electric Machine. 
Slides on the base of a dynamo-electric 
machine for moving part of its frame. 

Weather Contact.— (1) A weather cross. 
(2) A partial contact between w r ires ow- 
ing to leakage in bad weather. 

Weather Cross. — A contact or leak occur- 
ring in a telegraphic or other line during 
wet weather, from a defective action of 
the insulators. 

Weather Proof Insulation.— A trade- 
name for a character of insulation con- 
sisting of one or more layers of braided 



Wea.] 



986 



[Wim. 



material soaked in an insulating com- 
pound. 
"Weather-Proof Wire.— A wire provided 
with weather-proof insulation. 

"Weber. — (1) The practical unit of magnetic 
flux. (2) A unit of magnetic flux having 
the value of one absolute unit or line. 
(3) A term formerly employed for unit of 
current, but now replaced by ampere. (4) 
A term proposed by Clausius and Siemens, 
but not adopted, for a magnetic pole of 
unit strength. 

Weber Turns.— Flux linkages in C. G. S. 
units of flux and the turns through which 
they pass. 

Weber's Theory of Diamagnetism.— A 
theory which endeavors to account for the 
phenomena of diamagnetism on the as- 
sumption of originally magnetized parti- 
cles, molecules, or atoms. 

Wedge Battery.— In a telegraph station, 
a battery whose terminals are connected 
with a wedge for insertion in a jack. 

Wedge Cut-Out. — A form of cut-out em- 
ployed on telegraphic circuits. 

Weeding-Out of Harmonics by Elec- 
tric Resonance. — Gradually removing 
the upper harmonics from a complex- 
harmonic current by altering the natural 
period of the system, until it is in unison 
or resonance with the fundamental fre- 
quency. 

Weight of Observations.— The relative 
numerical reliability of observations. 

Weight Efficiency of Transformer. — 
The specific output or activity of a trans- 
former. 

Weight Voltameter — A voltameter in 
which the quantity of current passing is 
determined by the difference of weight of 
the instrument after the current has 
passed for a given time. 

Weight Voltmeter. — A voltmeter in 
which the potential difference to be meas- 
ured is determined by the movement of 
a magnetic needle under the influence of 
the current, against the action of a 
weight. 

Weight-Per-Mile-Ohm.— (1) A standard 
of conductivity of wires. (2) The weight 
per mile of a wire, multiplied by its re- 
sistance per mile at a given temperature. 

Welded Rail Bond.— A rail bond ef- 
fected by electrically welding together 
the ends of the rails. 

Welder. — A name sometimes applied to an 
electric welder. 

Welding.— Uniting, generally at a high 



temperature, two pieces of metal in one 
without the appearance of a junction. 

Welding Converter.— A welding trans- 
former. 

Welding, Electric— Effecting the weld- 
ing union of metals by means of heat of 
electric origin. 

Welding Transformer.— A step-down 
transformer employed in electric welding. 

Welsbach Burner. — A form of incandes- 
cent mantel burner whose light is due to 
the incandescence under the action of a 
Bunsen flame of a mantel covered with 
refractory materials. 

Western Union Splice.— A term some- 
times employed for an American wire 
joint. 

Wheatstone's Electric Balance. — A 
name sometimes given to an electric 
bridge or balance. 

Wheatstone's Electric Bridge. — A 
Wheatstone's electric balance. 

Wheel Brush. — A name given to any- 
rotary brush. 

Wheel Printing Telegraph.— A printing 
telegraph in which a printing wheel is 
employed. 

Whip. — A vibrating contact-maker. 

Whirl, Electric— (1) A term employed to 
indicate the circular directions of the 
lines of magnetic force surrounding a 
conductor conveying an electric current. 
(2) A magnetic whirl. 

Whistle, Electric— An automatic electric 
whistle. 

Whistling Effect.— (1) An effect produced 
with a carbon transmitter and telephone 
receiver in a line, such that if the trans- 
mitter be close to the receiver and then 
slightly jarred, a musical note will be 
emitted by the receiver which will react 
upon the transmitter and produce similar 
sounds in other receivers on the same 
circuit. (2) A means sometimes em- 
ployed to call a subscriber's attention 
when his receiver has been accidentally 
left in the line circuit, instead of the bell. 

White. — Containing all the frequencies of 
the sun s radiation. 

White Heat. — A temperature of a heated 
body, at which it emits all visible fre- 
quencies from the red to the violet, and 
therefore glows with a white light. 

Wig- Wag Signalling. — A term sometimes 

used for torch signalling. 
Wimshust's Electrostatic Machine.— A 

form of influence electric machine. 



Win.] 



[Woo. 



Wind and Water Line of Telegraph 
Pole. — The surface of a telegraph pole at 
the level of the ground, where it is ex- 
posed to the destructive action of air and 
water. 

Wind, Electric. — The convection streams 
of air particles produced at the extremi- 
ties of points attached to the surface of 
charged insulated conductors. 

Windage of Dynamo Armature.— A 
term proposed for the air-gap between 
the armature and the pole-pieces of a 
dynamo. (Not in general use.) 

Winding Space.— The space provided on 
an armature or magnet core for its mag- 
netizing coils. 

Windings. — A general name applied to 
the coils placed on an armature of a 
dynamo or motor, or on the core of an 
electro-magnet. 

Wind-Mill Electric— A term sometimes 
used for an electric flyer. 

Wind-Mill Meter.— An alternating-cur- 
rent meter whose operation is dependent 
on the motion of a wind -mill, by currents 
of air set up by tiie heat emitted from a 
conductor through which the current to 
be measured is passing. 

Window Contact.— A variety of burglar- 
alarm contact, by means of which an 
alarm bell is rung by a slight pressure 
against a blind contact, on any attempt 
from without, after the breaking of the 
glass in the window. 

Window-Tube Insulator.— A tube of 
vulcanite, or other insulating material, 
provided for the insulation of a wire 
entering a room through a window. 

Wings. — The conducting plates, flaps, or 
extensions, of an electric resonator or 
oscillator. 

Wipe Spark. — A spark obtained from a 
spark coil by the wiping contact of a 
spring. 

Wiped Joint.— (1) A wiped solder or 
plumber's joint. (2) A joint in the lead 
sheathing of a cable formed by adding free 
surface metal, as in a plumber's joint in 
lead pipes. 

Wiping Contact. — A contact obtained by 
a wiping movement of one conductor 
against another. 

Wippe. — An orthography sometimes em- 
ployed for whip. 

Wire. — (1) To provide with a conduct- 
ing circuit. (2) To send a telegram. 

Wire. — (1) A conductor that forms part of 
a circuit. (2) A telegram. 

Wire Core.— A form of laminated core ob- 



tained by the use of a number of iron 
wires. 

Wire Drum.— A drum for holding over- 
head wires in process of erection. 

Wire Dynamometer.— A line dynamo- 
meter. 

Wire Finder. — Any form of galvanometer 
used to locate or find the corresponding 
ends of different wires in a bunched cable. 

Wire-G-rating Polarizer.— A series of 
parallel wires set in a frame and em- 
ployed for polarizing electro-magnetic 
waves. 

Wire Guard. — A wire netting placed over 
an incandescent lamp chamber, acting as 
a guard or protection for it. 

Wire Holder.— (t) A form of insulator 
suitable for holding or supporting a wire. 
(2) A reel or cross suitable for holding a 
roll of wire. 

Wire Joint. — (1) Any joint connecting 
two pieces of line wire. (2) A telegraphic 
joint. 

Wire Rail-Bond. — A bond between con- 
tiguous or opposite rails effected by- 
means of a conducting wire. 

Wire Selector. — A wire finder. 

Wire Shade-G-uard. — A wire guard pro- 
vided for the shade of an incandescent 
lamp. 

Wire Shield for Incandescent Lamp. — 
A wire lamp-guard. 

Wire Splice.— A splice effected between 
two pieces of wire. 

Wire Terminals.— Metal eyes for solder- 
ing to the ends of wires and for connec- 
tions to switchboards. 

Wire-Wound Armature.— An armature 
which is wound with wire, as distin- 
guished from an armature wound with 
bars. 

Wired. — Provided with a conducting wire 
or wires. 

Wireless Telegraphy. — (1) A general 
term for any form of telegraphic com- 
munication which can be effected with- 
out wire circuits. (2) Induction teleg- 
raphy. (3) Conduction telegraphy through 
the medium of the earth. 

Wiring. — (1) Placing or installing the 
wires required in any circuit. (2) Col- 
lectively, the wires or electric conductors 
employed in any circuit of electric dis- 
tribution. 

Wood Mouldings, Electric— Mouldings 
of dried non-conducting wood provided 
with longitudinal grooves for the recep- 



Woo.] 



988 



[X-Ra. 



tion and support of electric wires or con- 
ductors. 
Wood's Button-Repeater.— A form of 
manual telegraphic repeater. 

Work. — The product of the force by the 
distance through which it acts. 

Work, Electric— (1) The joule. (2) A 
volt-coulomb, or the work done by the 
passage of one conduct through one volt. 

Work-Meter. — A word sometimes used 
for energy meter. 

Working Current.— (1) In an alternating- 
current circuit, a name sometimes given 
to an active current, or that component 
of the current which is in phase with the 
pressure. (2) Any current in a circuit, 
which does work. (3) A current operat- 
ing a translating device. 

Working Current of Motor.— The active 
current of an alternating-current motor. 

Working Efficiency of Telegraphic 
Circuit. — The variation or margin be- 
tween the joint resistance of the line 
conductor and the resistance of the in- 
sulators supporting such conductor. 

Working Galvanometer-Constant.— A 
term sometimes employed for galvano- 
meter constant. 



Working Position of Switch.— The po- 
sition of a switch when closed. 

Working Speed of Cable.— A term em- 
ployed for the number of signals that can 
be sent over a cable in a given time. 

Working Substance of Storage Bat- 
tery. — A name sometimes given to the 
active material of a storage battery. 

Woven-Wire Dynamo or Motor 

Brushes. — Gauze brushes for dynamos 
or motors. 

Wrapped Wire.— Wire covered with a 
wrapping of insulating material. 

Wrecking Wagon for Trolley Line. — A 

word sometimes used for repair wagon. 

Writing Error. — In telegraphy an error 
made in writing a message. 

Writing Telegraph. —A general name 
for the apparatus used in writing tele- 
graphy. 

Writing Telegraphy.— A species of fac- 
simile telegraphy, by means of which the 
motions of a transmitting pen so vary 
the resistance of two lines connected with 
the receiving instrument, as to cause 
a receiving pen or stylus to reproduce 
them. 



X-Graph. — A word sometimes employed 
for radiograph. 

X-Radiation. — A term sometimes used 
for Roentgen radiation. 

X-Ray Field.— The field of activity of 
X-rays. 

X-Ray Fluoroscopy.— The study of flu- 
oroscopic effects obtained by means of 
the X-rays. 

X-Ray Lamp. — A lamp consisting essen- 
tially of a high-vacuum tube', the inner 
walls of which are covered with crystals 
of calcium tungstate or other fluorescent 
substance, which emits fluorescent light 
when exposed to X-rays. 

X-Ray Photograph. — A term sometimes 
employed for radiograph. 

X-Ray Photography.— Photography ef- 
fected by means of the X-rays. 

X-Ray Picture. — A term sometimes em- 
ployed for radiograph. 



X-Ray Source.— Any source capable of 
producing X-rays. 

X-Ray Transformer. — A transformer 
employed for obtaining the high-potential 
discharges employed in Roentgen or X- 
ray tubes. 

X-Ray Transformer-Coil.— A form of 
induction coil employed for the produc- 
tion of X-rays. 

X-Ray Tube. — A name sometimes given 
to a Roentgen ray tube. 

X-Rays. — (1) A name frequently given to 
X-radiation. (2) The invisible rays emit- 
ted by an electrically excited Crookes 
tube, and which are capable of penetrat- 
ing many substances opaque to light, and 
of producing actinic or fluorescent effects. 
(3) The unknown rays emitted by an X- 
ray tube from some point, generally op- 
posite the cathode, which receives cath- 
ode-ray bombardment. 



T-Co.] 



989 



[Zin. 



Y-Connection of Three-Phaser.— (1) The 

connection, resembling the letter Y, of the 
three circuits of a triphaser to a common 
junction. (2) Star connection. 

Y-Connected Three-Phaser Armature. 

(1) A triphase armature having three cir- 
cuits connected to a common point. (2) A 
star-connected triphase armature. 

Y-Conneetor. — A connector resembling 
the letter Y in shape for joining a con- 
ductor to two branch wires. 

Y-Current. — The current between any 
wire of a triphase system and the neutral 
point. 

Y-Guy for Telegraph Pole.— A Y-shaped 
guy attached to a telegraph pole for pre- 
venting it from bending near the top. 

Y-Potential of-Triphase System.— The 
effective difference of potential or volt- 
meter pressure between one terminal or 



conductor of a triphase system and the 
neutral point. 
Y-Shaped Spark. — A variety of three- 
branched spark obtained by the discharge 
of a Leyden jar through a peculiar form 
of induction coil. 

Yale-Lock-Switch Burglar-Alarm.— 

An apparatus whereby the opening of a 
door by an authorized party provided with 
a regular key, will not sound an alarm, 
but any other opening will sound an alarm. 

Yacht-Tender, Electric— An electrically 
propelled tender provided for use in con- 
nection with a yacht. 

Yoke. — That portion of the iron of an elec- 
tro-magnet that joins the two cores. 

Yoke Horse-Shoe Electro-Magnet.— A 

horse-shoe electro-magnet whose two 
straight limbs are formed of two straight 
rods or bars connected together at one 
pair of ends by a yoke. 



Z. — A symbol sometimes employed in elec- 
tro-therapeutics for muscular contraction. 

Z. — A symbol for electro-chemical equiv- 
alent. 

Z-Insulator. — A simple form of single- 
shed earthenware overhead line insul- 
ator. 

Zamboni's Dry Pile.— A form of dry pile 
consisting of discs of paper, silvered on 
one side and tinned on the other, placed 
together alternately with slightly moist- 
ened bin-oxide of manganese. 

Zeeman Effect.— The broadening of the 
lines in the spectrum of a heated sub- 
stance when placed in the flux of a power- 
ful magnetic field. 

Zero Method.— (1) Any method employed 
in electrical measurement, in which the 
value of the electromotive force, the resist- 
ance, current, or other similar quantities, 
are determined by balancing against such 
quantities equal values of the same units, 
and ascertaining the equality, not by the 
deflection of a needle of a galvanometer or 
electrometer, but by the absence of such 
deflections. (2) A null method. 

Zero Potential. — (1) An arbitrary poten- 
tial-level from which electric levels are 
measured. (2) The earth's potential. 



Zigzag Electro-Magnet.— A multipolar 
electro-magnet whose magnetizing coils 
are separately wound in grooves cut in 
the face of straight or curved bars. 

Zigzag Electromotive Force. — An elec- 
tromotive force, the curve of which would 
have the general form of a zigzag. 

Zigzag Lightning.— (1) A common vari- 
ety of lightning flash, in which the dis- 
charge assumes a forked or zigzag ap- 
pearance. (2) Forked lightning. 

Zigzag Periodic Electromotive 
Force. — A zigzag alternating electro- 
motive force. 

Zigzag Type of Periodically Alter- 
nating Electromotive Force.— An 
alternating electromotive force whose 
graphic representation is a zig-zag curve. 

Zinc Battery. — A battery employed in 
sending zinc currents to line, 

Zinc-Carbon Voltaic Cell.— A voltaic 
cell consisting of a zinc-carbon couple 
immersed in a suitable electrolyte. 

Zinc-Copper Voltaic Cell.— A voltaic 
cell consisting of a zinc-copper couple im- 
mersed in a suitable electrolyte. 

Zinc-Lead Accumulator. — A secondary 
cell employing plates of lead and zinc. 






Zin.] 



990 



[Zon. 



Zinc Currents. — A term sometimes used 
for negative currents. 

Zinc-Lead Voltaic Cell.— A voltaic cell 
consisting of a zinc-lead couple immersed 
in a suitable electrolyte. 

Zinc Plating.— Electro-plating with zinc. 

Zinc Sender. — A device employed in tele- 
graphic circuits in order to counteract 
the retardation produced by the charge 
given to the line, in which a momentary 
reverse current is sent into the line after 
each signal. 

Zincs. — A general term applied to the zinc 
elements of voltaic cells. 

Zincode of Voltaic Cell.— A name for- 



merly given to the zinc terminal or elec- 
trode of a voltaic cell. 
Zootrope. — An optical toy depending on 
the persistence of vision, in which a num- 
ber of pictures of animals are so caused 
to pass before the eye as to produce th© 
appearance of the motions of life. 

Zonal Harmonic— A zonal surface har- 
monic. 

Zonal Surface Harmonic. — A spherical 
harmonic which is symmetrical about an 
axis. 

Zone Lamp.— A lamp provided with a 
lens-shaped chamber so as to cause it to 
throw out its light in a single zone onlj. 



M 



xm 



